feat: add castling rights revocation to processMove

Introduces applyRightsRevocation helper that revokes rights on castle
moves, king/rook departures from home squares, and enemy captures on
rook home squares. Six new tests verify all revocation paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/CLAUDE.MD

@@ -0,0 +1,120 @@
+# Claude Code – Working Agreement
+
+## Workflow: Plan → Write Tests → Implement → Verify
+
+### 1. Plan First
+Before writing any code, produce an explicit plan:
+- Restate the requirement in your own words to confirm understanding.
+- List every file you intend to create or modify.
+- Identify risks or unknowns upfront.
+- Wait for confirmation **only** when the plan reveals an ambiguity that cannot be resolved from context. Otherwise proceed immediately.
+
+### 2. Write Tests
+Before implementing, write tests that should cover the new behaviour.
+Only write tests for the new behaviour.
+
+### 3. Implement
+Follow the plan. Do not add scope beyond what was agreed.
+
+### 4. Verify Every Requirement
+After implementation, go through each requirement one-by-one and confirm it is satisfied:
+- Run the relevant tests (unit, integration, or build check) for every changed module.
+- If a requirement **cannot** be fulfilled, do **not** silently skip it — document it immediately (see *Unresolved Requirements* below).
+
+---
+
+## No Code Without Verification (Testing)
+
+- Every new behaviour must be covered by at least one automated test before the task is considered done.
+- Every bug fix must be accompanied by a regression test that fails before the fix and passes after.
+- Run `./gradlew :modules:<module>:test` (or the appropriate Gradle task) and confirm a green build before marking work complete.
+- If a test cannot be written for a legitimate reason, document it in `docs/unresolved.md` with an explanation.
+
+---
+
+## Automatic Bug Fixing
+
+- When a test or build step fails, attempt to fix the root cause immediately — do **not** ask for permission.
+- Apply the fix, re-run the verification, and continue until green.
+- If the same failure persists after **three** fix attempts, stop, log the issue in `docs/unresolved.md`, and surface a concise summary.
+
+---
+
+## Unresolved Requirements → `docs/unresolved.md`
+
+When a requirement or bug cannot be resolved, append an entry to `docs/unresolved.md`:
+
+```markdown
+## [YYYY-MM-DD] <Short title>
+
+**Requirement / Bug:**
+<What was requested or what failed>
+
+**Root Cause (if known):**
+<Why it cannot be resolved right now>
+
+**Attempted Fixes:**
+1. <What was tried>
+2. …
+
+**Suggested Next Step:**
+<What a human engineer should investigate>
+```
+
+Create the file if it does not exist. Never delete existing entries.
+
+---
+
+## Project Structure
+
+```
+.                        ← Repository root (multi-project Gradle setup)
+├── build.gradle.kts     ← Root build file (shared plugins, dependency versions)
+├── settings.gradle.kts  ← Gradle settings (declares all subprojects)
+├── modules/             ← One subdirectory per microservice
+│   └── <service>/
+│       ├── build.gradle.kts
+│       └── src/
+└── docs/                ← Architecture Decision Records, API docs, unresolved issues
+    └── unresolved.md
+```
+
+### Conventions
+- All microservices live under `modules/{service-name}`. Never place service code in the root.
+- Shared configuration (dependency versions, plugin setup) belongs in the **root** `build.gradle.kts` or in `buildSrc` / a version catalog.
+- `settings.gradle.kts` must include every module via `include(":modules:<service>")`.
+- Architecture decisions go in `docs/adr/` as numbered Markdown files (`ADR-001-<title>.md`).
+- API contracts live in `/docs/api/`.
+- Unit tests extend `AnyFunSuite with Matchers with JUnitSuiteLike` — no `@Test` annotations, no `: Unit` requirement
+- Integration tests use `@QuarkusTest` with JUnit 5 — `@Test` methods must be explicitly typed `: Unit`
+- Always exclude scala-library from Quarkus deps to avoid Scala 2 conflicts
+
+## Coverage Conventions
+- Branch coverage must be at least 90% - unless there is a good reason not to.
+- Line coverage must be at least 95% - unless there is a good reason not to.
+- Method coverage must be at least 90% - unless there is a good reason not to.
+- To check coverage use jacoco-reporter/scoverage_coverage_gaps.py modules/{service}/build/reports/scoverageTest/scoverage.xml
+- IMPORTANT: modules/{service}/build/reports/scoverage/scoverage.xml is not used for coverage TEST calculation. Do not use it.
+
+## Agent Routing Rules
+
+### Use agents in PARALLEL when:
+- Tasks touch different, independent microservices
+- No shared files or state between tasks
+- Example: "implement service-user AND service-orders simultaneously"
+
+### Use agents SEQUENTIALLY when:
+- Tasks have dependencies (architect → implementer → test-writer)
+- Shared API contracts are involved
+- Example: design API first, then implement, then test
+
+## Quick-Reference Checklist
+
+Before considering any task done, confirm:
+
+- [ ] Plan was written and requirements restated
+- [ ] All planned files were created / modified
+- [ ] Automated tests cover the new behaviour
+- [ ] `./gradlew build` (or scoped task) is green
+- [ ] Each requirement has been explicitly verified
+- [ ] Any unresolved items are logged in `docs/unresolved.md`

.claude/agents/code-reviewer.md

@@ -23,7 +23,7 @@ report findings to team-leader, who re-invokes scala-implementer for fixes.
 - `@QuarkusTest` methods (JUnit 5) must be explicitly typed `: Unit`
 
 ### Tests
-- Unit tests must extend `AnyFunSuite with Matchers`
+- Unit tests must extend `AnyFunSuite with Matchers with JUnitSuiteLike`, not plain JUnit 5
 - Integration tests use `@QuarkusTest` with JUnit 5 `@Test` methods
 - No raw `@Test` annotations on plain unit test classes
 

.claude/agents/scala-implementer.md

@@ -2,10 +2,9 @@
 name: scala-implementer
 description: "Implements Scala 3 + Quarkus REST services, domain logic, and persistence"
 tools: Read, Write, Edit, Bash, Glob
-model: inherit
+model: sonnet
 color: pink
 ---
-
 You do not have permissions to write tests, just source code.
 You are a Scala 3 expert specialising in Quarkus microservices.
 Always read the relevant /docs/api/ file before implementing.

.claude/agents/test-writer.md

@@ -2,10 +2,9 @@
 name: test-writer
 description: "Writes QuarkusTest unit and integration tests for a service. Invoke after scala-implementer has finished."
 tools: Read, Write, Edit, Bash, Glob, Grep, WebFetch, WebSearch, NotebookEdit
-model: haiku
+model: sonnet
 color: purple
 ---
-
 You do not have permissions to modify the source code, just write tests.
 You write tests for Scala 3 + Quarkus services.
 
@@ -13,11 +12,12 @@ You write tests for Scala 3 + Quarkus services.
 - Unit tests: `extends AnyFunSuite with Matchers` — use `test("description") { ... }` DSL, no `@Test` annotation, no `: Unit` return type needed.
 - Integration tests: `@QuarkusTest` with JUnit 5 — `@Test` methods MUST be explicitly typed `: Unit`.
 
-Target 100% conditional coverage if possible.
+Target 95%+ conditional coverage.
 
 When invoked BEFORE scala-implementer (no implementation exists yet):
   Use the contract-first-test-writing skill — write failing tests from docs/api/{service}.yaml.
 
 When invoked AFTER scala-implementer (implementation exists):
   Run python3 jacoco-reporter/jacoco_coverage_gaps.py modules/{service-name}/build/reports/jacoco/test/jacocoTestReport.xml --output agent
+  Use the jacoco-coverage-gaps skill — close coverage gaps revealed by the report.
   To regenerate the report run the tests first.

.claude/memory/MEMORY.md

@@ -1,9 +0,0 @@
-# Memory Index
-
-## Feedback
-- [feedback_keep_structure_updated.md](feedback_keep_structure_updated.md) — Update structure memory files whenever source files are added, removed, or changed
-
-## Project Structure
-- [project_structure_root.md](project_structure_root.md) — Top-level layout, modules list, VERSIONS map, navigation rules (skip `build/`, `.gradle/`, `.idea/`)
-- [project_structure_api.md](project_structure_api.md) — `modules/api`: all files and types (Board, Piece, Square, GameState, Move, ApiResponse, PlayerInfo)
-- [project_structure_core.md](project_structure_core.md) — `modules/core`: all files and types (GameContext, GameRules, MoveValidator, GameController, Parser, Renderer)

.claude/memory/feedback_keep_structure_updated.md

@@ -1,16 +0,0 @@
----
-name: keep-structure-memory-updated
-description: Always update the project structure memory files when adding, removing, or changing source files
-type: feedback
----
-
-After any change that adds, removes, renames, or significantly alters a source file, update the relevant structure memory file:
-
-- New/renamed/deleted file in `modules/api` → update `project_structure_api.md`
-- New/renamed/deleted file in `modules/core` → update `project_structure_core.md`
-- New module, dependency version change, or new top-level directory → update `project_structure_root.md`
-- New module added → create a new `project_structure_<module>.md` and add it to `MEMORY.md`
-
-**Why:** Structure memories are the primary navigation aid. Stale entries cause wasted exploration.
-
-**How to apply:** Treat the structure memory update as part of completing any implementation task — do it in the same session, not as a follow-up.

.claude/memory/project_structure_api.md

@@ -1,51 +0,0 @@
----
-name: module-api-structure
-description: File and type overview for the modules/api module (shared domain types)
-type: project
----
-
-# Module: `modules/api`
-
-**Purpose:** Shared domain model — pure data types with no game logic. Depended on by `modules/core`.
-
-**Gradle:** `id("scala")`, no `application` plugin. No Quarkus. Uses scoverage plugin.
-
-**Package root:** `de.nowchess.api`
-
-## Source files (`src/main/scala/de/nowchess/api/`)
-
-### `board/`
-| File | Contents |
-|------|----------|
-| `Board.scala` | `opaque type Board = Map[Square, Piece]` — extensions: `pieceAt`, `withMove`, `pieces`; `Board.initial` sets up start position |
-| `Color.scala` | `enum Color { White, Black }` — `.opposite`, `.label` |
-| `Piece.scala` | `case class Piece(color, pieceType)` — convenience vals `WhitePawn`…`BlackKing` |
-| `PieceType.scala` | `enum PieceType { Pawn, Knight, Bishop, Rook, Queen, King }` — `.label` |
-| `Square.scala` | `enum File { A–H }`, `enum Rank { R1–R8 }`, `case class Square(file, rank)` — `.toString` algebraic, `Square.fromAlgebraic(s)` |
-
-### `game/`
-| File | Contents |
-|------|----------|
-| `GameState.scala` | `case class CastlingRights(kingSide, queenSide)` + `.None`/`.Both`; `enum GameResult { WhiteWins, BlackWins, Draw }`; `enum GameStatus { NotStarted, InProgress, Finished(result) }`; `case class GameState(piecePlacement, activeColor, castlingWhite, castlingBlack, enPassantTarget, halfMoveClock, fullMoveNumber, status)` — FEN-compatible snapshot |
-
-### `move/`
-| File | Contents |
-|------|----------|
-| `Move.scala` | `enum PromotionPiece { Knight, Bishop, Rook, Queen }`; `enum MoveType { Normal, CastleKingside, CastleQueenside, EnPassant, Promotion(piece) }`; `case class Move(from, to, moveType = Normal)` |
-
-### `player/`
-| File | Contents |
-|------|----------|
-| `PlayerInfo.scala` | `opaque type PlayerId = String`; `case class PlayerInfo(id: PlayerId, displayName: String)` |
-
-### `response/`
-| File | Contents |
-|------|----------|
-| `ApiResponse.scala` | `sealed trait ApiResponse[+A]` → `Success[A](data)` / `Failure(errors)`; `case class ApiError(code, message, field?)`; `case class Pagination(page, pageSize, totalItems)` + `.totalPages`; `case class PagedResponse[A](items, pagination)` |
-
-## Test files (`src/test/scala/de/nowchess/api/`)
-Mirror of main structure — one `*Test.scala` per source file using `AnyFunSuite with Matchers`.
-
-## Notes
-- `GameState` is FEN-style but `Board` (in `core`) is a `Map[Square,Piece]` — the two are separate representations
-- `CastlingRights` is defined here in `api`; the castling logic lives in `core`

.claude/memory/project_structure_core.md

@@ -1,48 +0,0 @@
----
-name: module-core-structure
-description: File and type overview for the modules/core module (TUI chess engine)
-type: project
----
-
-# Module: `modules/core`
-
-**Purpose:** Standalone TUI chess application. All game logic, move validation, rendering. Depends on `modules/api`.
-
-**Gradle:** `id("scala")` + `application` plugin. Main class: `de.nowchess.chess.Main`. Uses scoverage plugin.
-
-**Package root:** `de.nowchess.chess`
-
-## Source files (`src/main/scala/de/nowchess/chess/`)
-
-### Root
-| File | Contents |
-|------|----------|
-| `Main.scala` | Entry point — prints welcome, starts `GameController.gameLoop(GameContext.initial, Color.White)` |
-
-### `controller/`
-| File | Contents |
-|------|----------|
-| `GameController.scala` | `sealed trait MoveResult` ADT: `Quit`, `InvalidFormat`, `NoPiece`, `WrongColor`, `IllegalMove`, `Moved`, `MovedInCheck`, `Checkmate`, `Stalemate`; `object GameController` — `processMove(ctx, turn, raw): MoveResult` (pure), `gameLoop(ctx, turn)` (I/O loop), `applyRightsRevocation(...)` (castling rights bookkeeping) |
-| `Parser.scala` | `object Parser` — `parseMove(input): Option[(Square, Square)]` parses coordinate notation e.g. `"e2e4"` |
-
-### `logic/`
-| File | Contents |
-|------|----------|
-| `GameContext.scala` | `enum CastleSide { Kingside, Queenside }`; `case class GameContext(board, whiteCastling, blackCastling)` — `.castlingFor(color)`, `.withUpdatedRights(color, rights)`; `GameContext.initial`; `extension (Board).withCastle(color, side)` moves king+rook atomically |
-| `GameRules.scala` | `enum PositionStatus { Normal, InCheck, Mated, Drawn }`; `object GameRules` — `isInCheck(board, color)`, `legalMoves(ctx, color): Set[(Square,Square)]`, `gameStatus(ctx, color): PositionStatus` |
-| `MoveValidator.scala` | `object MoveValidator` — `isLegal(board, from, to)`, `legalTargets(board, from): Set[Square]` (board-only, no castling), `legalTargets(ctx, from)` (context-aware, includes castling), `isCastle`, `castleSide`, `castlingTargets(ctx, color)` — full castling legality (empty squares, no check through transit) |
-
-### `view/`
-| File | Contents |
-|------|----------|
-| `Renderer.scala` | `object Renderer` — `render(board): String` outputs ANSI-colored board with file/rank labels |
-| `PieceUnicode.scala` | `extension (Piece).unicode: String` maps each piece to its Unicode chess symbol |
-
-## Test files (`src/test/scala/de/nowchess/chess/`)
-Mirror of main structure — one `*Test.scala` per source file using `AnyFunSuite with Matchers`.
-
-## Key design notes
-- `MoveValidator` has two overloaded `legalTargets`: one takes `Board` (geometry only), one takes `GameContext` (adds castling)
-- `GameRules.legalMoves` filters by check — it calls `MoveValidator.legalTargets(ctx, from)` then simulates each move
-- Castling rights revocation is in `GameController.applyRightsRevocation`, triggered after every move
-- No `@QuarkusTest` — this module is a plain Scala application, not a Quarkus service

.claude/memory/project_structure_root.md

@@ -1,55 +0,0 @@
----
-name: project-root-structure
-description: Top-level project structure, modules list, and navigation notes for NowChessSystems
-type: project
----
-
-# NowChessSystems — Root Structure
-
-## Directory layout (skip `build/`, `.gradle/`, `.idea/`)
-
-```
-NowChessSystems/
-├── build.gradle.kts          # Root: sonarqube plugin, VERSIONS map
-├── settings.gradle.kts       # include(":modules:core", ":modules:api")
-├── gradlew / gradlew.bat
-├── CLAUDE.md                 # Project instructions for Claude Code
-├── .claude/
-│   ├── CLAUDE.MD             # Working agreement (plan/verify/unresolved)
-│   ├── settings.json
-│   └── agents/               # architect, code-reviewer, gradle-builder, scala-implementer, test-writer
-├── docs/
-│   ├── Claude-Skills.md
-│   ├── Security.md
-│   └── unresolved.md
-├── jacoco-reporter/          # Python scripts for coverage gap reporting
-└── modules/
-    ├── api/                  # Shared domain types (no logic)
-    └── core/                 # TUI chess engine + game logic
-```
-
-## Modules
-
-| Module | Gradle path | Purpose |
-|--------|-------------|---------|
-| `api` | `:modules:api` | Shared domain model: Board, Piece, Move, GameState, ApiResponse |
-| `core` | `:modules:core` | TUI chess app: game logic, move validation, rendering |
-
-`core` depends on `api` via `implementation(project(":modules:api"))`.
-
-## VERSIONS (root `build.gradle.kts`)
-
-| Key | Value |
-|-----|-------|
-| `QUARKUS_SCALA3` | 1.0.0 |
-| `SCALA3` | 3.5.1 |
-| `SCALA_LIBRARY` | 2.13.18 |
-| `SCALATEST` | 3.2.19 |
-| `SCALATEST_JUNIT` | 0.1.11 |
-| `SCOVERAGE` | 2.1.1 |
-
-## Navigation rules
-- **Always skip** `build/`, `.gradle/`, `.idea/` when exploring — they are generated artifacts
-- Tests use `AnyFunSuite with Matchers` (ScalaTest), not JUnit `@Test`
-- No Quarkus in current modules — Quarkus is planned for future services
-- Agent workflow: architect → scala-implementer → test-writer → gradle-builder → code-reviewer

.idea/AndroidProjectSystem.xml

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="AndroidProjectSystem">
-    <option name="providerId" value="com.android.tools.idea.GradleProjectSystem" />
-  </component>
-</project>

.idea/gradle.xml

@@ -12,7 +12,6 @@
             <option value="$PROJECT_DIR$/modules" />
             <option value="$PROJECT_DIR$/modules/api" />
             <option value="$PROJECT_DIR$/modules/core" />
-            <option value="$PROJECT_DIR$/modules/ui" />
           </set>
         </option>
       </GradleProjectSettings>

.idea/misc.xml

@@ -1,3 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="FrameworkDetectionExcludesConfiguration">

.idea/scala_compiler.xml

@@ -5,7 +5,7 @@
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
     </profile>
-    <profile name="Gradle 2" modules="NowChessSystems.modules.core.main,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test,NowChessSystems.modules.ui.main,NowChessSystems.modules.ui.scoverage,NowChessSystems.modules.ui.test">
+    <profile name="Gradle 2" modules="NowChessSystems.modules.core.main,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test">
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
       <parameters>

.idea/vcs.xml

@@ -6,17 +6,7 @@
       <inspection_tool class="CommitNamingConvention" enabled="true" level="WARNING" enabled_by_default="true" />
     </profile>
   </component>
-  <component name="IssueNavigationConfiguration">
-    <option name="links">
-      <list>
-        <IssueNavigationLink>
-          <option name="issueRegexp" value="(?x)\b(CORE|NCWF|BAC|FRO|K8S|ORG|NCI|NCS)-\d+\b#YouTrack" />
-          <option name="linkRegexp" value="https://knockoutwhist.youtrack.cloud/issue/$0" />
-        </IssueNavigationLink>
-      </list>
-    </option>
-  </component>
   <component name="VcsDirectoryMappings">
-    <mapping directory="" vcs="Git" />
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
   </component>
 </project>

CLAUDE.md

@@ -1,58 +1,58 @@
-# CLAUDE.md — NowChessSystems
+# CLAUDE.md
 
-## Stack
-Scala 3.5.x · Quarkus + quarkus-scala3 · Hibernate/Jakarta · Lanterna TUI · K8s + ArgoCD + Kargo · Frontend TBD (Vite/React/Angular/Vue)
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
 
-### Memory
+## Build & Test Commands
 
-Your memory is saved under .claude/memory/MEMORY.md.
-
-## Structure
-```
-build.gradle.kts / settings.gradle.kts   # root; include(":modules:<svc>") per service
-modules/<svc>/build.gradle.kts + src/
-docs/adr/  docs/api/  docs/unresolved.md
-```
-Versions in root `extra["VERSIONS"]`; modules read via `rootProject.extra["VERSIONS"] as Map<String,String>`.
-
-## Commands
 ```bash
+# Build everything
 ./gradlew build
-./gradlew :modules:<svc>:build|test
-./gradlew :modules:<svc>:test --tests "de.nowchess.<svc>.<Class>"
+
+# Build a single module
+./gradlew :modules:<service>:build
+
+# Run tests for a single module
+./gradlew :modules:<service>:test
+
+# Run a specific test class
+./gradlew :modules:<service>:test --tests "de.nowchess.<service>.<ClassName>"
 ```
 
-## Workflow
-1. **Plan** — restate requirement, list files, flag risks. Proceed unless genuine ambiguity.
-2. **Tests first** — cover only new behaviour.
-3. **Implement** — no scope creep.
-4. **Verify** — check each requirement; confirm green build.
+The only current module is `core` (`modules/core`).
 
-## Scala/Quarkus Rules
-- `given`/`using` only (no `implicit`); `Option`/`Either`/`Try` (no `null`/`.get`)
-- `jakarta.*` only; reactive I/O (`Uni`/`Multi`), no blocking on event loop
-- Always exclude `org.scala-lang:scala-library` from Quarkus BOM
-- Unit tests: `extends AnyFunSuite with Matchers` — no `@Test`, no `: Unit`
-- Integration tests: `@QuarkusTest` + JUnit 5 — `@Test` methods need explicit `: Unit`
+## Architecture
 
-## Coverage
-Line = 100% · Branch = 100% · Method = 100% · Regression tests · document exceptions
-Check: `jacoco-reporter/scoverage_coverage_gaps.py modules/{svc}/build/reports/scoverageTest/scoverage.xml`
-⚠️ Use `scoverageTest/`, NOT `scoverage/`.
+**NowChessSystems** is a chess platform built as a Scala 3 + Quarkus microservice system.
 
-## Bug Fixing
-Fix failures immediately without asking. After 3 failed attempts → log in `docs/unresolved.md` + surface summary.
+- Multi-module Gradle project; every service lives under `modules/{service-name}`.
+- Shared dependency versions live in the root `build.gradle.kts` under `extra["VERSIONS"]`.
+- Each module reads versions via `rootProject.extra["VERSIONS"] as Map<String, String>`.
+- `settings.gradle.kts` must `include(":modules:<service>")` for every module.
 
-## Agents (new service)
-Sequential: architect → scala-implementer → test-writer → gradle-builder → code-reviewer (review only, no self-fix)
-Parallel: only when services are fully independent (no shared contracts/state).
+### Stack (ADR-001)
+| Layer | Technology |
+|---|---|
+| Language | Scala 3.5.x |
+| Backend framework | Quarkus + `quarkus-scala3` extension |
+| Persistence | Hibernate / Jakarta Persistence |
+| Frontend (TBD) | Vite; React/Angular/Vue under evaluation |
+| TUI | Lanterna |
+| Container orchestration | Kubernetes + ArgoCD + Kargo |
 
-## Unresolved (`docs/unresolved.md`)
-Append only, never delete:
-```
-## [YYYY-MM-DD] <title>
-**Requirement/Bug:** **Root Cause:** **Attempted Fixes:** **Next Step:**
-```
+### Key Scala 3 / Quarkus Rules
+- Use `given`/`using`, not `implicit` (no Scala 2 idioms).
+- Use `Option`/`Either`/`Try`, never `null` or `.get`.
+- Jakarta annotations only (`jakarta.*`), never `javax.*`.
+- Use reactive types (`Uni`, `Multi`) for I/O; no blocking calls on the event loop.
+- **Always exclude `org.scala-lang:scala-library` from Quarkus BOM** to avoid Scala 2 conflicts.
+- **Unit tests use `extends AnyFunSuite with Matchers with JUnitSuiteLike`** — ScalaTest DSL, no `@Test` annotations needed.
+- **Integration tests use `@QuarkusTest` with JUnit 5** — explicit `: Unit` return type still required on `@Test` methods.
 
-## Done Checklist
-- [ ] Plan written · files created/modified · tests green · requirements verified · unresolved logged
+### Agent Workflow (for new services)
+1. **architect** → writes OpenAPI contract to `docs/api/{service}.yaml` and ADR to `docs/adr/`.
+2. **scala-implementer** → reads contract, implements service under `modules/{service}/`.
+3. **test-writer** → writes `@QuarkusTest` integration tests and `AnyFunSuite with Matchers with JUnitSuiteLike` unit tests.
+4. **gradle-builder** → resolves any build/dependency issues.
+5. **code-reviewer** → reviews; reports findings back without self-fixing.
+
+Detailed working agreement (plan/verify/unresolved workflow) is in `.claude/CLAUDE.MD`.

docs/adr/ADR-001-Stack.md

@@ -0,0 +1,43 @@
+# ADR-001: Technology Stack Selection
+
+## Status
+Accepted
+
+## Context
+The "NowChessSystems" project requires a modern, scalable,
+and maintainable technology stack to support web-based interfaces.
+The system is designed as a microservice architecture to allow for independent scaling and development of various components (e.g., engine, matchmaking, user management).
+
+## Decision
+We have decided to use the following technologies for the core system:
+
+### Backend
+- **Language:** [Scala 3](https://scala-lang.org/) for its powerful type system, functional programming capabilities, and seamless JVM integration.
+- **Framework:** [Quarkus](https://quarkus.io/) with the `io.quarkiverse.scala:quarkus-scala3` extension to leverage GraalVM native compilation and fast startup times.
+- **Persistence:** [Hibernate](https://hibernate.org/) and [Jakarta Persistence](https://jakarta.ee/specifications/persistence/) for standard-based ORM.
+
+### Frontend
+- **Build Tool:** [Vite](https://vitejs.dev/) for a fast development experience.
+- **Framework:** TBD (Evaluation between React, Angular, and Vue).
+- **Terminal UI:** [Lanterna](https://github.com/mabe02/lanterna) for a text-based user interface (TUI).
+
+### DevOps & Infrastructure
+- **Orchestration:** [Kubernetes](https://kubernetes.io/) for container orchestration.
+- **GitOps & Delivery:** [ArgoCD](https://argoproj.github.io/cd/) for continuous delivery and [Kargo](https://kargo.io/) for multi-stage lifecycle management.
+
+### AI-Assisted Development
+- [Claude Code Pro](https://claude.ai/) and [Claude Agent Teams](https://claude.ai/team) for coding and reviews.
+- [Google Stitch](https://stitch.google.com/) (Free) for UI design and prototyping.
+
+## Consequences
+
+### Positive
+- **High Performance:** Quarkus and GraalVM enable low memory footprint and fast startup.
+- **Developer Productivity:** Scala 3 and AI tools provide a high-level, expressive environment.
+- **Robustness:** Kubernetes and ArgoCD ensure reliable deployment and scaling.
+- **Accessibility:** Offering both a TUI and a web interface caters to different user preferences.
+
+### Negative / Risks
+- **Complexity:** Managing a microservices architecture with Kubernetes adds operational overhead.
+- **Learning Curve:** Scala 3 and the specific Quarkus-Scala integration may require training for new developers.
+- **Consistency:** Maintaining parity between the TUI and Web frontend functionality.

docs/adr/ADR-002-api-shared-models.md

@@ -0,0 +1,86 @@
+# ADR-002: Shared-Models Library (`modules/api`)
+
+## Status
+Accepted
+
+## Context
+
+NowChessSystems is a microservice platform. As soon as two or more services need to
+exchange data — whether through REST, messaging, or internal function calls — they must
+agree on common data types. Without a shared home for those types, the same case class
+(e.g. `Square`, `Move`, `GameState`) is duplicated in every module, diverges over time,
+and causes silent serialisation mismatches at runtime.
+
+The `core` module currently owns the chess engine logic. Future modules (matchmaking,
+game history, user management, notation export, etc.) will all need to refer to the
+same chess domain vocabulary. A cross-cutting place to hold that vocabulary is therefore
+required before any second service is built.
+
+## Decision
+
+We introduce `modules/api` as a **shared-models library**: a plain Scala 3 library
+(no Quarkus, no Jakarta, no persistence) that contains only:
+
+- Pure Scala 3 data types: `case class`, `sealed trait`, and `enum` definitions
+- Value objects that model the chess domain (pieces, colors, squares, moves, game state)
+- Cross-service API envelope types (`ApiResponse[A]`, `ApiError`, `Pagination`)
+- Minimal player/user identity stubs (IDs and display names only)
+
+Every service module that needs these types declares:
+
+```kotlin
+implementation(project(":modules:api"))
+```
+
+in its own `build.gradle.kts`. The `modules/api` module itself carries no runtime
+dependencies beyond the Scala 3 standard library.
+
+### Package layout
+
+```
+de.nowchess.api
+├── board          – Color, PieceType, Piece, File, Rank, Square
+├── game           – CastlingRights, GameState, GameResult, GameStatus
+├── move           – MoveType, Move, PromotionPiece
+├── player         – PlayerId, PlayerInfo
+└── response       – ApiResponse, ApiError, Pagination
+```
+
+## What belongs in `modules/api`
+
+| Belongs | Does NOT belong |
+|---|---|
+| `case class`, `sealed trait`, `enum` for chess domain | Quarkus `@ApplicationScoped` beans |
+| API envelope types (`ApiResponse`, `ApiError`) | Jakarta Persistence entities (`@Entity`) |
+| Player identity stubs (ID + display name) | REST resource classes |
+| FEN/board-state representation types | Business logic, engine algorithms |
+| Pure type aliases and value objects | Database queries or repositories |
+
+The rule of thumb: if a type carries a framework annotation or requires I/O to produce,
+it does not belong in `modules/api`.
+
+## How other modules depend on it
+
+1. `modules/api` is a regular Gradle subproject already declared in `settings.gradle.kts`.
+2. Consuming modules add `implementation(project(":modules:api"))` — nothing else.
+3. Because `modules/api` has no Quarkus BOM, consuming modules must not re-export Quarkus
+   transitive dependencies through it.
+4. If a future module needs JSON serialisation, it adds its own JSON library (e.g.
+   `circe`, `jsoniter-scala`) as a dependency and derives codecs for the shared types
+   there — codec derivation stays out of `modules/api`.
+
+## Consequences
+
+### Positive
+- Single source of truth for all chess domain vocabulary.
+- Adding a new microservice requires only one `implementation(project(":modules:api"))`
+  line — no copy-paste of types.
+- The library is fast to compile (no framework processing) and cheap to test in isolation.
+- Enforces a strict boundary: if a type needs a framework annotation it is forced into the
+  correct service module.
+
+### Negative / Risks
+- Any breaking change to a shared type (rename, field removal) is a cross-cutting change
+  that touches every consuming module simultaneously.
+- Developers must resist the temptation to add convenience methods or logic to these
+  types; discipline is required to keep the library pure.

docs/superpowers/plans/2026-03-22-scalatest-scoverage.md

@@ -0,0 +1,244 @@
+# ScalaTest + Scoverage Migration Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Replace JaCoCo with Scoverage and add ScalaTest (with its JUnit 5 bridge) as the test library across all modules.
+
+**Architecture:** Three build files are modified — the root for shared dependency versions, and each module for plugins, dependencies, and task wiring. No source files are created. The Scoverage Gradle plugin is applied per-module with its version hardcoded inline (Gradle resolves `plugins {}` before `rootProject.extra` is available).
+
+**Tech Stack:** Scala 3, Gradle (Kotlin DSL), ScalaTest 3.2.19, scalatestplus-junit-5-11 3.2.19.1, Scoverage Gradle plugin 8.1.
+
+---
+
+## File Map
+
+| File | Change |
+|---|---|
+| `build.gradle.kts` (root) | Add `SCALATEST` and `SCALATESTPLUS_JUNIT5` version entries |
+| `modules/core/build.gradle.kts` | Replace `jacoco` with `org.scoverage`; swap JUnit deps for ScalaTest; merge two `tasks.test {}` blocks |
+| `modules/api/build.gradle.kts` | Same as core; also add missing `useJUnitPlatform()` |
+
+---
+
+### Task 1: Add ScalaTest version entries to root build
+
+**Files:**
+- Modify: `build.gradle.kts` (root)
+
+- [ ] **Step 1: Add version entries**
+
+Open `build.gradle.kts` at the root. The `versions` map currently looks like:
+
+```kotlin
+val versions = mapOf(
+    "QUARKUS_SCALA3" to "1.0.0",
+    "SCALA3"         to "3.5.1",
+    "SCALA_LIBRARY"  to "2.13.18"
+)
+```
+
+Add two entries so it becomes:
+
+```kotlin
+val versions = mapOf(
+    "QUARKUS_SCALA3"        to "1.0.0",
+    "SCALA3"                to "3.5.1",
+    "SCALA_LIBRARY"         to "2.13.18",
+    "SCALATEST"             to "3.2.19",
+    "SCALATESTPLUS_JUNIT5"  to "3.2.19.1"
+)
+```
+
+- [ ] **Step 2: Verify the root build file parses**
+
+```bash
+./gradlew help --quiet
+```
+
+Expected: exits 0 with no errors.
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add build.gradle.kts
+git commit -m "build: add ScalaTest version entries to root versions map"
+```
+
+---
+
+### Task 2: Migrate `modules/core` to ScalaTest + Scoverage
+
+**Files:**
+- Modify: `modules/core/build.gradle.kts`
+
+- [ ] **Step 1: Replace the `jacoco` plugin with `org.scoverage`**
+
+In the `plugins {}` block, replace:
+```kotlin
+jacoco
+```
+with:
+```kotlin
+id("org.scoverage") version "8.1"
+```
+
+The full plugins block should be:
+```kotlin
+plugins {
+    id("scala")
+    id("org.scoverage") version "8.1"
+    application
+}
+```
+
+- [ ] **Step 2: Swap JUnit dependencies for ScalaTest**
+
+In the `dependencies {}` block, remove:
+```kotlin
+testImplementation(platform("org.junit:junit-bom:5.10.0"))
+testImplementation("org.junit.jupiter:junit-jupiter")
+testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+```
+
+Add in their place:
+```kotlin
+testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
+testImplementation("org.scalatestplus:junit-5-11_3:${versions["SCALATESTPLUS_JUNIT5"]!!}")
+```
+
+- [ ] **Step 3: Merge the two `tasks.test {}` blocks and replace jacoco wiring**
+
+The file currently has two separate `tasks.test {}` blocks and a `tasks.jacocoTestReport {}` block. Delete all three. Add the following single merged block **after** the `dependencies {}` block:
+
+```kotlin
+tasks.test {
+    useJUnitPlatform()
+    finalizedBy(tasks.reportScoverage)
+}
+tasks.reportScoverage {
+    dependsOn(tasks.test)
+}
+```
+
+- [ ] **Step 4: Run the tests**
+
+```bash
+./gradlew :modules:core:test
+```
+
+Expected: BUILD SUCCESSFUL. (Zero tests is fine — there are no test files yet. The build must not fail with dependency resolution or plugin errors.)
+
+- [ ] **Step 5: Run the coverage report**
+
+```bash
+./gradlew :modules:core:reportScoverage
+```
+
+Expected: BUILD SUCCESSFUL. A report is generated under `modules/core/build/reports/scoverage/`.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add modules/core/build.gradle.kts
+git commit -m "build(core): replace JaCoCo with Scoverage, add ScalaTest dependencies"
+```
+
+---
+
+### Task 3: Migrate `modules/api` to ScalaTest + Scoverage
+
+**Files:**
+- Modify: `modules/api/build.gradle.kts`
+
+- [ ] **Step 1: Replace the `jacoco` plugin with `org.scoverage`**
+
+In the `plugins {}` block, replace:
+```kotlin
+jacoco
+```
+with:
+```kotlin
+id("org.scoverage") version "8.1"
+```
+
+The full plugins block should be:
+```kotlin
+plugins {
+    id("scala")
+    id("org.scoverage") version "8.1"
+}
+```
+
+- [ ] **Step 2: Swap JUnit dependencies for ScalaTest**
+
+In the `dependencies {}` block, remove:
+```kotlin
+testImplementation(platform("org.junit:junit-bom:5.10.0"))
+testImplementation("org.junit.jupiter:junit-jupiter")
+testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+```
+
+Add in their place:
+```kotlin
+testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
+testImplementation("org.scalatestplus:junit-5-11_3:${versions["SCALATESTPLUS_JUNIT5"]!!}")
+```
+
+- [ ] **Step 3: Merge the two `tasks.test {}` blocks and replace jacoco wiring**
+
+The `modules/api` file also has two `tasks.test {}` blocks and a `jacocoTestReport` block. Delete all three. Add the following merged block **after** the `dependencies {}` block:
+
+```kotlin
+tasks.test {
+    useJUnitPlatform()
+    finalizedBy(tasks.reportScoverage)
+}
+tasks.reportScoverage {
+    dependsOn(tasks.test)
+}
+```
+
+> Note: `modules/api` did not previously have `useJUnitPlatform()` — it is being **added** here, not preserved.
+
+- [ ] **Step 4: Run the tests**
+
+```bash
+./gradlew :modules:api:test
+```
+
+Expected: BUILD SUCCESSFUL.
+
+- [ ] **Step 5: Run the coverage report**
+
+```bash
+./gradlew :modules:api:reportScoverage
+```
+
+Expected: BUILD SUCCESSFUL. A report is generated under `modules/api/build/reports/scoverage/`.
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add modules/api/build.gradle.kts
+git commit -m "build(api): replace JaCoCo with Scoverage, add ScalaTest dependencies"
+```
+
+---
+
+### Task 4: Full build verification
+
+- [ ] **Step 1: Run the full build**
+
+```bash
+./gradlew build
+```
+
+Expected: BUILD SUCCESSFUL with no errors across all modules.
+
+- [ ] **Step 2: Confirm no JaCoCo references remain**
+
+```bash
+grep -r "jacoco\|jacocoTestReport" --include="*.kts" .
+```
+
+Expected: no output (zero matches).

docs/superpowers/plans/2026-03-23-chess-check-checkmate-stalemate.md

@@ -0,0 +1,579 @@
+# Chess Check / Checkmate / Stalemate Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add check detection, checkmate (win by opponent having no legal reply while in check), and stalemate (draw by opponent having no legal reply while not in check) to the chess game loop.
+
+**Architecture:** A new `GameRules` object owns all check-aware logic; the existing `MoveValidator` keeps its geometric-only contract unchanged. `GameController.processMove` calls `GameRules.gameStatus` after each move and returns new `MoveResult` variants (`MovedInCheck`, `Checkmate`, `Stalemate`). Terminal states reset the board.
+
+**Tech Stack:** Scala 3.5, ScalaTest (`AnyFunSuite with Matchers`), Gradle (`:modules:core:test`)
+
+---
+
+## File Map
+
+| File | Action | Responsibility |
+|---|---|---|
+| `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala` | **Create** | `isInCheck`, `legalMoves`, `gameStatus`, `PositionStatus` enum |
+| `modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala` | **Create** | Unit tests for all three `GameRules` methods |
+| `modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala` | **Modify** | Add `MovedInCheck`/`Checkmate`/`Stalemate` to `MoveResult`; wire `processMove` and `gameLoop` |
+| `modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala` | **Modify** | Add `processMove` and `gameLoop` tests for the three new results |
+
+---
+
+## Task 1: Create `GameRules` stub
+
+**Files:**
+- Create: `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala`
+
+- [ ] **Step 1: Create the stub file**
+
+```scala
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.*
+
+enum PositionStatus:
+  case Normal, InCheck, Mated, Drawn
+
+object GameRules:
+
+  /** True if `color`'s king is under attack on this board. */
+  def isInCheck(board: Board, color: Color): Boolean = false
+
+  /** All (from, to) moves for `color` that do not leave their own king in check. */
+  def legalMoves(board: Board, color: Color): Set[(Square, Square)] = Set.empty
+
+  /** Position status for the side whose turn it is (`color`). */
+  def gameStatus(board: Board, color: Color): PositionStatus = PositionStatus.Normal
+```
+
+- [ ] **Step 2: Verify the project compiles**
+
+```bash
+./gradlew :modules:core:compileScala
+```
+
+Expected: `BUILD SUCCESSFUL`
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala
+git commit -m "feat: add GameRules stub with PositionStatus enum"
+```
+
+---
+
+## Task 2: Write `GameRulesTest` (all tests must fail)
+
+**Files:**
+- Create: `modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala`
+
+- [ ] **Step 1: Create the test file**
+
+```scala
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.*
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameRulesTest extends AnyFunSuite with Matchers:
+
+  private def sq(f: File, r: Rank): Square = Square(f, r)
+  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
+
+  // ──── isInCheck ──────────────────────────────────────────────────────
+
+  test("isInCheck: king attacked by enemy rook on same rank"):
+    // White King E1, Black Rook A1 — rook slides along rank 1 to E1
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R1) -> Piece.BlackRook
+    )
+    GameRules.isInCheck(b, Color.White) shouldBe true
+
+  test("isInCheck: king not attacked"):
+    // Black Rook A3 does not cover E1
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R3) -> Piece.BlackRook
+    )
+    GameRules.isInCheck(b, Color.White) shouldBe false
+
+  test("isInCheck: no king on board returns false"):
+    val b = board(sq(File.A, Rank.R1) -> Piece.BlackRook)
+    GameRules.isInCheck(b, Color.White) shouldBe false
+
+  // ──── legalMoves ─────────────────────────────────────────────────────
+
+  test("legalMoves: move that exposes own king to rook is excluded"):
+    // White King E1, White Rook E4 (pinned on E-file), Black Rook E8
+    // Moving the White Rook off the E-file would expose the king
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.E, Rank.R4) -> Piece.WhiteRook,
+      sq(File.E, Rank.R8) -> Piece.BlackRook
+    )
+    val moves = GameRules.legalMoves(b, Color.White)
+    moves should not contain (sq(File.E, Rank.R4) -> sq(File.D, Rank.R4))
+
+  test("legalMoves: move that blocks check is included"):
+    // White King E1 in check from Black Rook E8; White Rook A5 can interpose on E5
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R5) -> Piece.WhiteRook,
+      sq(File.E, Rank.R8) -> Piece.BlackRook
+    )
+    val moves = GameRules.legalMoves(b, Color.White)
+    moves should contain(sq(File.A, Rank.R5) -> sq(File.E, Rank.R5))
+
+  // ──── gameStatus ──────────────────────────────────────────────────────
+
+  test("gameStatus: checkmate returns Mated"):
+    // White Qh8, Ka6; Black Ka8
+    // Qh8 attacks Ka8 along rank 8; all escape squares covered (spec-verified position)
+    val b = board(
+      sq(File.H, Rank.R8) -> Piece.WhiteQueen,
+      sq(File.A, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    )
+    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.Mated
+
+  test("gameStatus: stalemate returns Drawn"):
+    // White Qb6, Kc6; Black Ka8
+    // Black king has no legal moves and is not in check (spec-verified position)
+    val b = board(
+      sq(File.B, Rank.R6) -> Piece.WhiteQueen,
+      sq(File.C, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    )
+    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.Drawn
+
+  test("gameStatus: king in check with legal escape returns InCheck"):
+    // White Ra8 attacks Black Ke8 along rank 8; king can escape to d7, e7, f7
+    val b = board(
+      sq(File.A, Rank.R8) -> Piece.WhiteRook,
+      sq(File.E, Rank.R8) -> Piece.BlackKing
+    )
+    GameRules.gameStatus(b, Color.Black) shouldBe PositionStatus.InCheck
+
+  test("gameStatus: normal starting position returns Normal"):
+    GameRules.gameStatus(Board.initial, Color.White) shouldBe PositionStatus.Normal
+```
+
+- [ ] **Step 2: Run the tests and confirm they all fail**
+
+```bash
+./gradlew :modules:core:test --tests "de.nowchess.chess.logic.GameRulesTest"
+```
+
+Expected: all 8 tests FAIL (stubs always return `false` / `Set.empty` / `Normal`)
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala
+git commit -m "test: add failing GameRulesTest for check/checkmate/stalemate"
+```
+
+---
+
+## Task 3: Implement `GameRules`
+
+**Files:**
+- Modify: `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala`
+
+- [ ] **Step 1: Replace the stub bodies with real implementations**
+
+```scala
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.*
+
+enum PositionStatus:
+  case Normal, InCheck, Mated, Drawn
+
+object GameRules:
+
+  def isInCheck(board: Board, color: Color): Boolean =
+    board.pieces
+      .collectFirst { case (sq, Piece(`color`, PieceType.King)) => sq }
+      .exists { kingSq =>
+        board.pieces.exists { case (sq, piece) =>
+          piece.color != color &&
+          MoveValidator.legalTargets(board, sq).contains(kingSq)
+        }
+      }
+
+  def legalMoves(board: Board, color: Color): Set[(Square, Square)] =
+    board.pieces
+      .collect { case (from, piece) if piece.color == color => from }
+      .flatMap { from =>
+        MoveValidator.legalTargets(board, from)
+          .filter { to =>
+            val (newBoard, _) = board.withMove(from, to)
+            !isInCheck(newBoard, color)
+          }
+          .map(to => from -> to)
+      }
+      .toSet
+
+  def gameStatus(board: Board, color: Color): PositionStatus =
+    val moves   = legalMoves(board, color)
+    val inCheck = isInCheck(board, color)
+    if moves.isEmpty && inCheck then PositionStatus.Mated
+    else if moves.isEmpty       then PositionStatus.Drawn
+    else if inCheck             then PositionStatus.InCheck
+    else                             PositionStatus.Normal
+```
+
+- [ ] **Step 2: Run the GameRules tests and confirm they all pass**
+
+```bash
+./gradlew :modules:core:test --tests "de.nowchess.chess.logic.GameRulesTest"
+```
+
+Expected: all 8 tests PASS
+
+- [ ] **Step 3: Run the full test suite to make sure nothing regressed**
+
+```bash
+./gradlew :modules:core:test
+```
+
+Expected: `BUILD SUCCESSFUL`, all existing tests still pass
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala
+git commit -m "feat: implement GameRules with isInCheck, legalMoves, gameStatus"
+```
+
+---
+
+## Task 4: Add new `MoveResult` variants and stub `processMove`
+
+**Files:**
+- Modify: `modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala`
+
+- [ ] **Step 1: Add three new variants to `MoveResult` and import `GameRules`**
+
+In `GameController.scala`, update the `MoveResult` object and `processMove`. The new variants go after `Moved`. The import of `GameRules`/`PositionStatus` is added at the top. The stub `processMove` calls `GameRules.gameStatus` but always maps to `Moved` — this makes it compile while the new tests will fail:
+
+```scala
+package de.nowchess.chess.controller
+
+import scala.io.StdIn
+import de.nowchess.api.board.{Board, Color, Piece}
+import de.nowchess.chess.logic.{MoveValidator, GameRules, PositionStatus}
+import de.nowchess.chess.view.Renderer
+
+// ---------------------------------------------------------------------------
+// Result ADT returned by the pure processMove function
+// ---------------------------------------------------------------------------
+
+sealed trait MoveResult
+object MoveResult:
+  case object Quit                                                                   extends MoveResult
+  case class  InvalidFormat(raw: String)                                             extends MoveResult
+  case object NoPiece                                                                extends MoveResult
+  case object WrongColor                                                             extends MoveResult
+  case object IllegalMove                                                            extends MoveResult
+  case class  Moved(newBoard: Board, captured: Option[Piece], newTurn: Color)       extends MoveResult
+  case class  MovedInCheck(newBoard: Board, captured: Option[Piece], newTurn: Color) extends MoveResult
+  case class  Checkmate(winner: Color)                                               extends MoveResult
+  case object Stalemate                                                              extends MoveResult
+
+// ---------------------------------------------------------------------------
+// Controller
+// ---------------------------------------------------------------------------
+
+object GameController:
+
+  def processMove(board: Board, turn: Color, raw: String): MoveResult =
+    raw.trim match
+      case "quit" | "q" =>
+        MoveResult.Quit
+      case trimmed =>
+        Parser.parseMove(trimmed) match
+          case None =>
+            MoveResult.InvalidFormat(trimmed)
+          case Some((from, to)) =>
+            board.pieceAt(from) match
+              case None =>
+                MoveResult.NoPiece
+              case Some(piece) if piece.color != turn =>
+                MoveResult.WrongColor
+              case Some(_) =>
+                if !MoveValidator.isLegal(board, from, to) then
+                  MoveResult.IllegalMove
+                else
+                  val (newBoard, captured) = board.withMove(from, to)
+                  MoveResult.Moved(newBoard, captured, turn.opposite) // stub — Task 6 will fix
+
+  def gameLoop(board: Board, turn: Color): Unit =
+    println()
+    print(Renderer.render(board))
+    println(s"${turn.label}'s turn. Enter move: ")
+    val input = Option(StdIn.readLine()).getOrElse("quit").trim
+    processMove(board, turn, input) match
+      case MoveResult.Quit =>
+        println("Game over. Goodbye!")
+      case MoveResult.InvalidFormat(raw) =>
+        println(s"Invalid move format '$raw'. Use coordinate notation, e.g. e2e4.")
+        gameLoop(board, turn)
+      case MoveResult.NoPiece =>
+        println(s"No piece on ${Parser.parseMove(input).map(_._1).fold("?")(_.toString)}.")
+        gameLoop(board, turn)
+      case MoveResult.WrongColor =>
+        println(s"That is not your piece.")
+        gameLoop(board, turn)
+      case MoveResult.IllegalMove =>
+        println(s"Illegal move.")
+        gameLoop(board, turn)
+      case MoveResult.Moved(newBoard, captured, newTurn) =>
+        val prevTurn = newTurn.opposite
+        captured.foreach: cap =>
+          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
+          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
+        gameLoop(newBoard, newTurn)
+      case MoveResult.MovedInCheck(newBoard, captured, newTurn) => // stub — Task 6
+        gameLoop(newBoard, newTurn)
+      case MoveResult.Checkmate(winner) =>                         // stub — Task 6
+        gameLoop(Board.initial, Color.White)
+      case MoveResult.Stalemate =>                                 // stub — Task 6
+        gameLoop(Board.initial, Color.White)
+```
+
+- [ ] **Step 2: Confirm everything still compiles and existing tests pass**
+
+```bash
+./gradlew :modules:core:test
+```
+
+Expected: `BUILD SUCCESSFUL` — existing tests still pass, no compilation errors
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala
+git commit -m "feat: add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch)"
+```
+
+---
+
+## Task 5: Write new `GameControllerTest` cases (all must fail)
+
+**Files:**
+- Modify: `modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala`
+
+- [ ] **Step 1: Append the following tests to the existing file**
+
+Add after the last existing test (the `gameLoop: capture` test). Add the `captureOutput` helper alongside `withInput`:
+
+```scala
+  // ──── helpers ────────────────────────────────────────────────────────
+
+  private def captureOutput(block: => Unit): String =
+    val out = java.io.ByteArrayOutputStream()
+    scala.Console.withOut(out)(block)
+    out.toString("UTF-8")
+
+  // ──── processMove: check / checkmate / stalemate ─────────────────────
+
+  test("processMove: legal move that delivers check returns MovedInCheck"):
+    // White Ra1, Ka3; Black Kh8 — White plays Ra1-Ra8, putting Kh8 in check
+    // (Ra8 attacks along rank 8: b8..h8; king escapes to g7/g8/h7 — InCheck, not Mated)
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.A, Rank.R3) -> Piece.WhiteKing,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    ))
+    GameController.processMove(b, Color.White, "a1a8") match
+      case MoveResult.MovedInCheck(_, _, newTurn) => newTurn shouldBe Color.Black
+      case other => fail(s"Expected MovedInCheck, got $other")
+
+  test("processMove: legal move that results in checkmate returns Checkmate"):
+    // White Qa1, Ka6; Black Ka8 — White plays Qa1-Qh8 (diagonal a1-h8)
+    // After Qh8: White Qh8 + Ka6 vs Black Ka8 = checkmate (spec-verified)
+    // Note: Qa1 does NOT currently attack Ka8 (path along file A is blocked by Ka6)
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.A, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    ))
+    GameController.processMove(b, Color.White, "a1h8") match
+      case MoveResult.Checkmate(winner) => winner shouldBe Color.White
+      case other => fail(s"Expected Checkmate(White), got $other")
+
+  test("processMove: legal move that results in stalemate returns Stalemate"):
+    // White Qb1, Kc6; Black Ka8 — White plays Qb1-Qb6
+    // After Qb6: White Qb6 + Kc6 vs Black Ka8 = stalemate (spec-verified)
+    val b = Board(Map(
+      sq(File.B, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.C, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    ))
+    GameController.processMove(b, Color.White, "b1b6") match
+      case MoveResult.Stalemate => succeed
+      case other => fail(s"Expected Stalemate, got $other")
+
+  // ──── gameLoop: check / checkmate / stalemate ─────────────────────────
+
+  test("gameLoop: checkmate prints winner message and resets to new game"):
+    // Same position as checkmate processMove test above; after Qa1-Qh8 game resets
+    // Second move "quit" exits the new game cleanly
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.A, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1h8\nquit\n"):
+        GameController.gameLoop(b, Color.White)
+    output should include("Checkmate! White wins.")
+
+  test("gameLoop: stalemate prints draw message and resets to new game"):
+    val b = Board(Map(
+      sq(File.B, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.C, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("b1b6\nquit\n"):
+        GameController.gameLoop(b, Color.White)
+    output should include("Stalemate! The game is a draw.")
+
+  test("gameLoop: MovedInCheck without capture prints check message"):
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.A, Rank.R3) -> Piece.WhiteKing,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1a8\nquit\n"):
+        GameController.gameLoop(b, Color.White)
+    output should include("Black is in check!")
+
+  test("gameLoop: MovedInCheck with capture prints both capture and check message"):
+    // White Rook A1 captures Black Pawn on A8, putting Black King (H8) in check
+    // Ra8 attacks rank 8 → Black Kh8 is in check; king can escape to g7/g8/h7
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.A, Rank.R3) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackPawn,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1a8\nquit\n"):
+        GameController.gameLoop(b, Color.White)
+    output should include("captures")
+    output should include("Black is in check!")
+```
+
+- [ ] **Step 2: Run only the new tests and confirm they fail**
+
+```bash
+./gradlew :modules:core:test --tests "de.nowchess.chess.controller.GameControllerTest"
+```
+
+Expected: the 7 new tests FAIL; the existing 17 tests PASS
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala
+git commit -m "test: add failing GameControllerTest cases for check/checkmate/stalemate"
+```
+
+---
+
+## Task 6: Implement `processMove` dispatch and `gameLoop` branches
+
+**Files:**
+- Modify: `modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala`
+
+- [ ] **Step 1: Replace the stub `processMove` else-branch and the three stub `gameLoop` cases**
+
+Replace only the `else` branch inside `processMove` (keep everything else identical):
+
+```scala
+                else
+                  val (newBoard, captured) = board.withMove(from, to)
+                  GameRules.gameStatus(newBoard, turn.opposite) match
+                    case PositionStatus.Normal  => MoveResult.Moved(newBoard, captured, turn.opposite)
+                    case PositionStatus.InCheck => MoveResult.MovedInCheck(newBoard, captured, turn.opposite)
+                    case PositionStatus.Mated   => MoveResult.Checkmate(turn)
+                    case PositionStatus.Drawn   => MoveResult.Stalemate
+```
+
+Replace the three stub `gameLoop` cases:
+
+```scala
+      case MoveResult.MovedInCheck(newBoard, captured, newTurn) =>
+        val prevTurn = newTurn.opposite
+        captured.foreach: cap =>
+          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
+          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
+        println(s"${newTurn.label} is in check!")
+        gameLoop(newBoard, newTurn)
+      case MoveResult.Checkmate(winner) =>
+        println(s"Checkmate! ${winner.label} wins.")
+        gameLoop(Board.initial, Color.White)
+      case MoveResult.Stalemate =>
+        println("Stalemate! The game is a draw.")
+        gameLoop(Board.initial, Color.White)
+```
+
+- [ ] **Step 2: Run all controller tests**
+
+```bash
+./gradlew :modules:core:test --tests "de.nowchess.chess.controller.GameControllerTest"
+```
+
+Expected: all 24 tests PASS
+
+- [ ] **Step 3: Run the full test suite**
+
+```bash
+./gradlew :modules:core:test
+```
+
+Expected: `BUILD SUCCESSFUL`, all tests pass
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala
+git commit -m "feat: wire check/checkmate/stalemate into processMove and gameLoop"
+```
+
+---
+
+## Task 7: Coverage check and final verification
+
+- [ ] **Step 1: Run the full build with coverage**
+
+```bash
+./gradlew :modules:core:test
+```
+
+Expected: `BUILD SUCCESSFUL`
+
+- [ ] **Step 2: Check coverage gaps**
+
+```bash
+python jacoco-reporter/scoverage_coverage_gaps.py modules/core/build/reports/scoverageTest/scoverage.xml
+```
+
+Review output. If any newly added method falls below the thresholds from `CLAUDE.md` (branch ≥ 90%, line ≥ 95%, method ≥ 90%), add targeted tests to close the gaps before considering the task done.
+
+- [ ] **Step 3: Commit coverage fixes (if any)**
+
+```bash
+git add -p
+git commit -m "test: improve coverage for GameRules and GameController"
+```

docs/superpowers/specs/2026-03-22-scalatest-scoverage-design.md

@@ -0,0 +1,85 @@
+# Design: Add ScalaTest + Replace JaCoCo with Scoverage
+
+**Date:** 2026-03-22
+**Status:** Approved
+
+## Summary
+
+Replace the current JUnit-only test setup and JaCoCo coverage with ScalaTest (via its JUnit 5 bridge) and Scoverage across both `modules/core` and `modules/api`.
+
+## Motivation
+
+- The CLAUDE.md working agreement prescribes `AnyFunSuite with Matchers with JUnitSuiteLike` as the unit test style, which requires ScalaTest.
+- Scoverage is the standard Scala code coverage tool and understands Scala semantics; JaCoCo's JVM bytecode instrumentation is less accurate for Scala code.
+
+## Scope
+
+Two modules are affected: `modules/core` and `modules/api`. The root `build.gradle.kts` is updated for shared dependency versions only.
+
+## Changes
+
+### Root `build.gradle.kts`
+
+Add to the `versions` map (dependency versions only — plugin version is hardcoded per module, see note below):
+- `SCALATEST` → `3.2.19`
+- `SCALATESTPLUS_JUNIT5` → `3.2.19.1`
+
+> **Note on plugin versioning:** Gradle resolves the `plugins {}` block before `rootProject.extra` is available, so the Scoverage plugin version (`8.1`) must be declared inline in each module's `plugins {}` block. It cannot be read from the root versions map.
+
+### `modules/core/build.gradle.kts` and `modules/api/build.gradle.kts`
+
+Both modules require the same set of changes. Both currently have **two separate `tasks.test {}` blocks** that must be merged into one.
+
+**Plugins block:**
+- Remove `jacoco`
+- Add `id("org.scoverage") version "8.1"`
+
+**Dependencies block:**
+- Remove `testImplementation(platform("org.junit:junit-bom:5.10.0"))`
+- Remove `testImplementation("org.junit.jupiter:junit-jupiter")`
+- Remove `testRuntimeOnly("org.junit.platform:junit-platform-launcher")`
+- Add `testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")`
+- Add `testImplementation("org.scalatestplus:junit-5-11_3:${versions["SCALATESTPLUS_JUNIT5"]!!}")`
+
+**Task wiring — merge both `tasks.test {}` blocks into one and replace jacoco wiring:**
+
+Both `modules/core` and `modules/api` currently have two `tasks.test {}` blocks. Delete both and replace with the following single merged block placed **after** the `dependencies {}` block (conventional position):
+
+```kotlin
+tasks.test {
+    useJUnitPlatform()   // required — scalatestplus JUnit 5 bridge relies on this
+    finalizedBy(tasks.reportScoverage)
+}
+tasks.reportScoverage {
+    dependsOn(tasks.test)
+}
+```
+
+> Note: `modules/api` does not currently have `useJUnitPlatform()` — it must be **added** (not just kept) in the merged block.
+
+Remove the `jacocoTestReport` task block entirely from both modules.
+
+**Task name confirmation:** The Scoverage Gradle plugin 8.1 registers `reportScoverage` as the HTML report task.
+
+## Versions
+
+| Artifact | Version | Notes |
+|---|---|---|
+| `org.scalatest:scalatest_3` | 3.2.19 | Core ScalaTest for Scala 3 |
+| `org.scalatestplus:junit-5-11_3` | 3.2.19.1 | JUnit 5.11 runner bridge; `.1` = build 1 |
+| Scoverage Gradle plugin | 8.1 | Hardcoded inline in `plugins {}` block |
+
+## Testing the Change
+
+After applying:
+1. `./gradlew :modules:core:test` and `./gradlew :modules:api:test` must pass (green, even with zero test files).
+2. `./gradlew :modules:core:reportScoverage` must produce a coverage report.
+3. `./gradlew build` must be fully green.
+
+## Files Modified
+
+- `build.gradle.kts` (root) — add two version entries
+- `modules/core/build.gradle.kts` — plugin, deps, merge two `tasks.test` blocks, replace jacoco wiring
+- `modules/api/build.gradle.kts` — plugin, deps, merge two `tasks.test` blocks, add `useJUnitPlatform()`, replace jacoco wiring
+
+No new source files are created.

docs/superpowers/specs/2026-03-23-chess-check-checkmate-stalemate-design.md

@@ -0,0 +1,169 @@
+# Chess Check / Checkmate / Stalemate — Design Spec
+
+**Date:** 2026-03-23
+**Status:** Approved
+
+---
+
+## Scope
+
+Implement check detection, checkmate (win condition), and stalemate (draw) on top of the existing normal-move rules. En passant, castling, and pawn promotion are **out of scope** for this iteration.
+
+---
+
+## Architecture
+
+### New: `GameRules` object
+
+**File:** `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala`
+
+Owns all check-aware game logic. `MoveValidator` retains its documented geometric-only contract ("ignoring check/pin").
+
+```
+GameRules
+  isInCheck(board, color): Boolean
+  legalMoves(board, color): Set[(Square, Square)]
+  gameStatus(board, color): PositionStatus
+```
+
+#### `isInCheck(board, color)`
+
+Finds the king square for `color` by scanning `board.pieces` for a `Piece(color, PieceType.King)`. If no king is found (constructed/test boards), returns `false`.
+
+Then checks whether any enemy piece's `MoveValidator.legalTargets` contains that square. This works correctly for all piece types, including the king: `kingTargets` returns the squares the king can move to, which are identical to the squares the king attacks, so using `legalTargets` for attack detection is correct by design.
+
+Returns `true` if the king square is covered by at least one enemy piece.
+
+
+#### `legalMoves(board, color)`
+
+1. Filter `board.pieces` to entries where `piece.color == color`.
+2. For each such `(from, piece)`, call `MoveValidator.legalTargets(board, from)` to get geometric candidates.
+3. For each candidate `to`, apply `board.withMove(from, to)` to get `newBoard`.
+4. Keep only moves where `isInCheck(newBoard, color)` is `false` (i.e., the move does not leave own king in check).
+5. Return the full set of `(from, to)` pairs that survive this filter.
+
+#### `gameStatus(board, color)`
+
+Returns a `PositionStatus` enum value based on `legalMoves(board, color)` and `isInCheck(board, color)`:
+
+- `Mated`    — `legalMoves` is empty **and** king is in check → the side to move has been checkmated
+- `Drawn`    — `legalMoves` is empty **and** king is **not** in check → stalemate (draw)
+- `InCheck`  — `legalMoves` is non-empty **and** king is in check → game continues under check
+- `Normal`   — otherwise
+
+#### Local `PositionStatus` enum
+
+Defined in `GameRules.scala`. Names are intentionally distinct from `MoveResult` variants to avoid unqualified-name collisions in `GameController.scala`:
+
+```scala
+enum PositionStatus:
+  case Normal, InCheck, Mated, Drawn
+```
+
+---
+
+### Modified: `MoveResult` (in `GameController.scala`)
+
+Three new variants; existing variants are unchanged:
+
+| Variant | When used |
+|---|---|
+| `MovedInCheck(newBoard, captured, newTurn)` | Move was legal; opponent is now in check but has legal replies |
+| `Checkmate(winner: Color)` | Move was legal; opponent is `Mated` → `winner` is the side that just moved |
+| `Stalemate` | Move was legal; opponent is `Drawn` (no legal reply, not in check) |
+
+`Moved` continues to be used when `gameStatus` returns `Normal`.
+
+---
+
+### Modified: `GameController.processMove`
+
+After computing `(newBoard, captured)` from `board.withMove`:
+
+1. Call `GameRules.gameStatus(newBoard, newTurn)`.
+2. Map to the appropriate `MoveResult`:
+
+```
+PositionStatus.Normal   → Moved(newBoard, captured, newTurn)
+PositionStatus.InCheck  → MovedInCheck(newBoard, captured, newTurn)
+PositionStatus.Mated    → Checkmate(turn)   // turn = the side that just moved
+PositionStatus.Drawn    → Stalemate
+```
+
+---
+
+### Modified: `GameController.gameLoop`
+
+**New terminal branches** (both print a message then restart):
+
+- `Checkmate(winner)` → print `"Checkmate! {winner.label} wins."`, then recurse with `(Board.initial, Color.White)`
+- `Stalemate`         → print `"Stalemate! The game is a draw."`, then recurse with `(Board.initial, Color.White)`
+
+**New non-terminal branch:**
+
+- `MovedInCheck(newBoard, captured, newTurn)` → print the same optional capture message as `Moved` (when `captured.isDefined`), then print `"{newTurn.label} is in check!"`, then recurse with `(newBoard, newTurn)`
+
+**Restart vs. exit:** Checkmate and stalemate restart the game automatically (no prompt). This is intentionally asymmetric with `Quit`, which exits. `Quit` is an explicit user request to stop; Checkmate/Stalemate are natural game endings that should roll into a new game.
+
+---
+
+## Test Strategy
+
+All tests are unit tests extending `AnyFunSuite with Matchers with JUnitSuiteLike`.
+
+### `GameRulesTest` — new file
+
+| Scenario | Method | Expected |
+|---|---|---|
+| King attacked by enemy rook on same rank | `isInCheck` | `true` |
+| King not attacked (only own pieces nearby) | `isInCheck` | `false` |
+| No king on board (constructed board) | `isInCheck` | `false` |
+| Move that exposes own king to rook is excluded | `legalMoves` | does not contain that move |
+| Move that blocks check is included | `legalMoves` | contains the blocking move |
+| Checkmate: White Qh8, Ka6; Black Ka8 — Black king is in check (Qh8 along rank 8), cannot escape to a7 (Ka6), b7 (Ka6), or b8 (Qh8) | `gameStatus` | `Mated` |
+| Stalemate: White Qb6, Kc6; Black Ka8 — Black king has no legal moves (a7/b7/b8 all controlled by Qb6), not in check | `gameStatus` | `Drawn` |
+| King in check with at least one escape square | `gameStatus` | `InCheck` |
+| Normal midgame position, not in check, has moves | `gameStatus` | `Normal` |
+
+### `GameControllerTest` additions — new `processMove` cases
+
+| Scenario | Expected `MoveResult` |
+|---|---|
+| Move leaves opponent in check (has escape) | `MovedInCheck` |
+| Move results in checkmate | `Checkmate(winner)` where winner is the side that moved |
+| Move results in stalemate | `Stalemate` |
+
+### `GameControllerTest` additions — new `gameLoop` cases
+
+| Scenario | Expected output / behavior |
+|---|---|
+| `gameLoop` receives `Checkmate(White)` | Prints "Checkmate! White wins." and continues (new game) |
+| `gameLoop` receives `Stalemate` | Prints "Stalemate! The game is a draw." and continues (new game) |
+| `gameLoop` receives `MovedInCheck` with a capture | Prints capture message AND check message |
+| `gameLoop` receives `MovedInCheck` without a capture | Prints check message only |
+
+---
+
+## Development Workflow (TDD)
+
+1. Create `GameRules.scala` with empty/stub method bodies that compile but return placeholder values (`false`, `Set.empty`, `PositionStatus.Normal`).
+2. Write all `GameRulesTest` tests — they should **fail**.
+3. Implement `GameRules` logic until `GameRulesTest` is green.
+4. Add new `MoveResult` variants to `GameController.scala`; update `processMove` to call `GameRules.gameStatus` (stub the match arms initially).
+5. Write new `GameControllerTest` cases — they should **fail**.
+6. Implement `processMove` match arms and `gameLoop` new branches until all tests pass.
+7. Run `./gradlew :modules:core:test` — full green build required.
+
+---
+
+## Files Changed
+
+| File | Change |
+|---|---|
+| `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala` | New |
+| `modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala` | New |
+| `modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala` | Add `MoveResult` variants; update `processMove` and `gameLoop` |
+| `modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala` | Add new test cases |
+
+No changes to `modules/api` or `MoveValidator`.

docs/superpowers/specs/2026-03-24-castling-design.md

@@ -0,0 +1,255 @@
+# Castling Implementation Design
+
+**Date:** 2026-03-24
+**Status:** Approved (rev 2)
+**Branch:** castling
+
+---
+
+## Context
+
+The NowChessSystems chess engine currently operates on a raw `Board` (opaque `Map[Square, Piece]`) paired with a `Color` for turn tracking. Castling requires tracking whether the king and rooks have previously moved — state that does not exist in the current engine layer. The `CastlingRights` and `MoveType.Castle*` types are already defined in the `api` module but are not wired into the engine.
+
+---
+
+## Approach: `GameContext` Wrapper (Option B)
+
+Introduce a thin `GameContext` wrapper in `modules/core` that bundles `Board` with castling rights for both sides. This is the single seam through which the engine learns about castling availability without pulling in the full FEN-structured `GameState` type.
+
+---
+
+## Section 1 — `GameContext` Type
+
+**Location:** `modules/core/src/main/scala/de/nowchess/chess/logic/GameContext.scala`
+
+```scala
+case class GameContext(
+  board: Board,
+  whiteCastling: CastlingRights,
+  blackCastling: CastlingRights
+):
+  def castlingFor(color: Color): CastlingRights =
+    if color == Color.White then whiteCastling else blackCastling
+
+  def withUpdatedRights(color: Color, rights: CastlingRights): GameContext =
+    if color == Color.White then copy(whiteCastling = rights)
+    else copy(blackCastling = rights)
+```
+
+`GameContext.initial` wraps `Board.initial` with `CastlingRights.Both` for both sides.
+
+`gameLoop` and `processMove` replace `(board: Board, turn: Color)` with `(ctx: GameContext, turn: Color)`. All `MoveResult` variants that previously carried `newBoard: Board` now carry `newCtx: GameContext`. The `gameLoop` render call becomes `Renderer.render(ctx.board)`, and all `gameLoop` pattern match arms that destructure `MoveResult.Moved(newBoard, ...)` or `MoveResult.MovedInCheck(newBoard, ...)` must be updated to destructure `newCtx` and pass it to the recursive `gameLoop` call.
+
+---
+
+## Section 2 — `CastleSide` and Board Extension for Castle Moves
+
+### `CastleSide` enum
+
+`CastleSide` is a two-value engine-internal enum defined in `core` (not in `api`). It is co-located in `GameContext.scala` — there is no separate `CastleSide.scala` file.
+
+```scala
+enum CastleSide:
+  case Kingside, Queenside
+```
+
+### `withCastle` extension
+
+`Board.withMove(from, to)` moves a single piece. Castling moves two pieces atomically. To avoid a circular dependency (`api` must not import from `core`), `withCastle` is **not** added to `Board` in the `api` module. Instead it is defined as an extension method in `core`, co-located with `GameContext`:
+
+```scala
+// inside GameContext.scala or a BoardCastleOps.scala in core
+extension (b: Board)
+  def withCastle(color: Color, side: CastleSide): Board = ...
+```
+
+Post-castle square assignments:
+- **Kingside White:** King e1→g1, Rook h1→f1
+- **Queenside White:** King e1→c1, Rook a1→d1
+- **Kingside Black:** King e8→g8, Rook h8→f8
+- **Queenside Black:** King e8→c8, Rook a8→d8
+
+---
+
+## Section 3 — `MoveValidator` Castling Logic
+
+### Signature change
+
+`legalTargets` and `isLegal` are extended to accept `GameContext` when the caller has full game context. To avoid breaking `GameRules.isInCheck` (which uses `legalTargets` with only a `Board` for attacked-square detection), the implementation retains a **board-only private helper** for sliding/jump/normal king targets, and a **public overload** that additionally unions castling targets when a `GameContext` is provided:
+
+```scala
+// board-only (used internally by isInCheck)
+def legalTargets(board: Board, from: Square): Set[Square]
+
+// context-aware (used by legalMoves and processMove)
+def legalTargets(ctx: GameContext, from: Square): Set[Square]
+```
+
+The `GameContext` overload delegates to the `Board` overload for all piece types except King, where it additionally unions `castlingTargets(ctx, color)`.
+
+`isLegal` is likewise overloaded:
+
+```scala
+// board-only (retained for callers that have no castling context)
+def isLegal(board: Board, from: Square, to: Square): Boolean
+
+// context-aware (used by processMove)
+def isLegal(ctx: GameContext, from: Square, to: Square): Boolean
+```
+
+The context-aware `isLegal(ctx, from, to)` calls `legalTargets(ctx, from).contains(to)` — using the context-aware overload — so castling targets are included in the legality check.
+
+### `castlingTargets` method
+
+```scala
+def castlingTargets(ctx: GameContext, color: Color): Set[Square]
+```
+
+For each side (kingside, queenside), checks all six conditions in order (failing fast):
+
+1. `CastlingRights` flag is `true` for that side (`ctx.castlingFor(color)`)
+2. King is on its home square (e1 for White, e8 for Black)
+3. Relevant rook is on its home square (h-file for kingside, a-file for queenside)
+4. All squares between king and rook are empty
+5. King is **not currently in check** — calls `GameRules.isInCheck(ctx.board, color)` using the board-only path (no castling recursion)
+6. Each square the king **passes through and lands on** is not attacked — checks that no enemy `legalTargets(board, enemySq)` (board-only) covers those squares
+
+Transit and landing squares:
+- **Kingside:** f-file, g-file (White: f1, g1; Black: f8, g8)
+- **Queenside:** d-file, c-file (White: d1, c1; Black: d8, c8). Note: b1/b8 must be empty (condition 4) but the king does not pass through them, so they are not checked for attacks.
+
+---
+
+## Section 4 — `GameRules` Changes
+
+`GameRules.legalMoves` must accept `GameContext` (not just `Board`) so it can enumerate castling moves as part of the legal move set. This is required for correct stalemate and checkmate detection — a position where the only legal move is to castle must not be evaluated as stalemate.
+
+```scala
+def legalMoves(ctx: GameContext, color: Color): Set[(Square, Square)]
+```
+
+Internally it calls `MoveValidator.legalTargets(ctx, from)` (the context-aware overload) for all pieces of `color`, then filters to moves that do not leave the king in check.
+
+`isInCheck` retains its `(board: Board, color: Color)` signature — it does not need castling context.
+
+`gameStatus` is updated to accept `GameContext`:
+
+```scala
+def gameStatus(ctx: GameContext, color: Color): PositionStatus
+```
+
+---
+
+## Section 5 — `GameController` Changes
+
+### Move detection and execution
+
+`processMove` identifies a castling move by the king occupying its home square and moving exactly two files laterally:
+- White: e1→g1 (kingside) or e1→c1 (queenside)
+- Black: e8→g8 (kingside) or e8→c8 (queenside)
+
+Legality is confirmed via `MoveValidator.isLegal(ctx, from, to)` (the context-aware overload, which includes castling targets). When a castling move is legal and executed:
+1. Call `ctx.board.withCastle(color, side)` to move both pieces atomically.
+2. Revoke **both** castling rights for the moving color in the new `GameContext`.
+
+### Rights revocation rules (applied on every move)
+
+After every move `(from, to)` is applied, revoke rights based on both the **source square** and the **destination square**. Both tables are checked independently and all triggered revocations are applied.
+
+**Source square → revocation** (piece leaves its home square):
+
+| Source square | Rights revoked |
+|---------------|---------------|
+| `e1` | Both White castling rights |
+| `e8` | Both Black castling rights |
+| `a1` | White queenside |
+| `h1` | White kingside |
+| `a8` | Black queenside |
+| `h8` | Black kingside |
+
+**Destination square → revocation** (a piece — including an enemy piece — arrives on a rook home square, meaning a capture removed the rook):
+
+| Destination square | Rights revoked |
+|--------------------|---------------|
+| `a1` | White queenside |
+| `h1` | White kingside |
+| `a8` | Black queenside |
+| `h8` | Black kingside |
+
+This covers the following cases:
+- **King normal move** — source square e1/e8 fires; both rights revoked.
+- **King castle move** — the castle-specific step 2 revokes both rights for the moving color. Additionally, the source-square table fires (king departs e1/e8), revoking the same rights a second time. This double-revocation is idempotent and harmless. The king's destination (g1/c1/g8/c8) does not appear in the destination table, so no extra revocation fires there.
+- **Own rook move** — source square a1/h1/a8/h8 fires.
+- **Enemy capture on a rook home square** — destination square a1/h1/a8/h8 fires, revoking the side that lost the rook.
+
+`processMove` also calls `GameRules.gameStatus(newCtx, turn.opposite)` — note this call passes the full `GameContext`, not just a `Board`, because `gameStatus` now accepts `GameContext`.
+
+The revocation is applied to the `GameContext` that results from the move, before it is returned in `MoveResult`.
+
+### Signatures
+
+```scala
+def processMove(ctx: GameContext, turn: Color, raw: String): MoveResult
+def gameLoop(ctx: GameContext, turn: Color): Unit
+```
+
+`MoveResult.Moved` and `MoveResult.MovedInCheck` carry `newCtx: GameContext` instead of `newBoard: Board`. All `gameLoop` pattern match arms are updated to use `newCtx`. The render call uses `newCtx.board`.
+
+On checkmate/stalemate reset, `GameContext.initial` is used.
+
+---
+
+## Section 6 — Move Notation
+
+The player types standard coordinate notation:
+- `e1g1` → White kingside castle
+- `e1c1` → White queenside castle
+- `e8g8` → Black kingside castle
+- `e8c8` → Black queenside castle
+
+No parser changes required. The controller identifies castling by the king moving 2 files from the home square.
+
+---
+
+## Section 7 — Testing
+
+### `MoveValidatorTest`
+- Castling target (g1) is returned when all kingside conditions are met (White)
+- Castling target (c1) is returned when all queenside conditions are met (White)
+- Castling targets returned for Black kingside (g8) and queenside (c8)
+- Castling blocked when transit square is occupied (piece between king and rook)
+- Castling blocked when king is in check (condition 5)
+- Castling blocked when **transit square** is attacked (e.g., f1 attacked for White kingside)
+- Castling blocked when **landing square** is attacked (e.g., g1 attacked for White kingside)
+- Castling blocked when `kingSide = false` in `CastlingRights`
+- Castling blocked when `queenSide = false` in `CastlingRights`
+- Castling blocked when relevant rook is not on its home square
+
+### `GameControllerTest`
+- `processMove` with `e1g1` returns `Moved` with king on g1, rook on f1, and both White castling rights revoked in `newCtx`
+- `processMove` with `e1c1` returns `Moved` with king on c1, rook on d1, and both White castling rights revoked in `newCtx`
+- `processMove` castle attempt after king has moved returns `IllegalMove`
+- `processMove` castle attempt after rook has moved returns `IllegalMove`
+- Normal rook move from h1 revokes White kingside right in the returned `newCtx`
+- Normal king move from e1 revokes both White rights in the returned `newCtx`
+- Enemy capture on h1 (e.g., Black rook captures White rook on h1) revokes White kingside right in the returned `newCtx`
+
+### `GameRulesTest`
+- `legalMoves` includes castling destinations when available
+- `legalMoves` excludes castling when king is in check
+- `gameStatus` returns `Normal` (not `Drawn`) when the only legal move available is to castle — verifying that the `GameContext` signature change correctly prevents a false stalemate
+
+---
+
+## Files to Create / Modify
+
+| Action | File |
+|--------|------|
+| **Create** | `modules/core/src/main/scala/de/nowchess/chess/logic/GameContext.scala` — includes `CastleSide` enum and `withCastle` Board extension |
+| **Modify** | `modules/core/src/main/scala/de/nowchess/chess/logic/MoveValidator.scala` — add `castlingTargets`, board-only + context-aware `legalTargets`/`isLegal` overloads |
+| **Modify** | `modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala` — update `legalMoves` and `gameStatus` to accept `GameContext` |
+| **Modify** | `modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala` — use `GameContext`; castling detection, execution, rights revocation |
+| **Modify** | `modules/core/src/main/scala/de/nowchess/chess/Main.scala` — use `GameContext.initial` |
+| **Modify** | `modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala` — new castling tests |
+| **Modify** | `modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala` — update signatures + new castling tests |
+| **Modify** | `modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala` — update signatures + new castling tests |

docs/unresolved.md

@@ -1,20 +1,23 @@
-## [2026-03-31] Unreachable code blocking 100% statement coverage
+# Unresolved Issues
 
-**Requirement/Bug:** Reach 100% statement coverage in core module.
+## [2026-03-24] JUnitSuiteLike mixin not available for ScalaTest 3.2.19 with Scala 3
 
-**Root Cause:** 4 remaining uncovered statements (99.6% coverage) are unreachable code:
-1. **PgnParser.scala:160** (`case _ => None` in extractPromotion) - Regex `=([QRBN])` only matches those 4 characters; fallback case can never execute
-2. **GameHistory.scala:29** (`addMove$default$4` compiler-generated method) - Method overload 3 without defaults shadows the 4-param version, making promotionPiece default accessor unreachable
-3. **GameEngine.scala:201-202** (`case _` in completePromotion) - GameController.completePromotion always returns one of 4 expected MoveResult types; catch-all is defensive code
+**Requirement / Bug:**
+CLAUDE.md prescribes that all unit tests should extend `AnyFunSuite with Matchers with JUnitSuiteLike`. However, the `JUnitSuiteLike` trait cannot be resolved in the current build configuration.
+
+**Root Cause (if known):**
+- ScalaTest 3.2.19 for Scala 3 does not provide `JUnitSuiteLike` in any public package.
+- The `co.helmethair:scalatest-junit-runner:0.1.11` dependency does not expose this trait.
+- There is no `org.scalatest:scalatest-junit_3` artifact available for version 3.2.19.
+- The trait may have been removed or changed in the ScalaTest 3.x → Scala 3 migration.
 
 **Attempted Fixes:**
-1. Added comprehensive PGN parsing tests (all 4 promotion types) - PgnParser improved from 95.8% to 99.4%
-2. Added GameHistory tests using named parameters - hit `addMove$default$3` (castleSide) but not `$default$4` (promotionPiece)
-3. Named parameter approach: `addMove(from=..., to=..., promotionPiece=...)` triggers 4-param with castleSide default ✓
-4. Positional approach: `addMove(f, t, None, None)` requires all 4 args (explicit, no defaults used) - doesn't hit $default$4
-5. Root issue: Scala's overload resolution prefers more-specific non-default overloads (2-param, 3-param) over the 4-param with defaults
+1. Tried importing from `org.scalatest.junit.JUnitSuiteLike` — not found
+2. Tried importing from `org.scalatestplus.junit.JUnitSuiteLike` — not found
+3. Tried importing from `co.helmethair.scalatest.junit.JUnitSuiteLike` — not found
+4. Attempted to add `org.scalatest:scalatest-junit_3:3.2.19` dependency — artifact does not exist in Maven Central
 
-**Recommendation:** 99.6% (1029/1033) is maximum achievable without refactoring method overloads. Unreachable code design patterns:
-- **Pattern 1 (unreachable regex fallback):** Defensive pattern match against exhaustive regex
-- **Pattern 2 (overshadowed defaults):** Method overloads shadow default parameters in parent signature
-- **Pattern 3 (defensive catch-all):** Error handling for impossible external API returns
+**Suggested Next Step:**
+1. Either find the correct ScalaTest artifact/import for Scala 3 JUnit integration, or
+2. Update CLAUDE.md to reflect the actual constraint that unit tests should extend `AnyFunSuite with Matchers` (without `JUnitSuiteLike`), or
+3. Investigate whether a different test runner or configuration is needed to achieve JUnit integration with ScalaTest 3 in Scala 3

jacoco-reporter/jacoco_coverage_gaps.py

@@ -0,0 +1,411 @@
+#!/usr/bin/env python3
+"""
+JaCoCo Coverage Gap Reporter
+Parses a JaCoCo XML report and outputs missing line & branch (conditional)
+coverage in a structured format that Claude Code agents can act on directly.
+
+Usage:
+    python jacoco_coverage_gaps.py <jacoco-report.xml> [--min-coverage 80]
+    python jacoco_coverage_gaps.py <jacoco-report.xml> --output json
+    python jacoco_coverage_gaps.py <jacoco-report.xml> --output markdown
+    python jacoco_coverage_gaps.py <jacoco-report.xml> --output agent   (default)
+"""
+
+import xml.etree.ElementTree as ET
+import sys
+import argparse
+import json
+from pathlib import Path
+from dataclasses import dataclass, field
+from typing import Optional
+
+
+# ---------------------------------------------------------------------------
+# Data classes
+# ---------------------------------------------------------------------------
+
+@dataclass
+class LineCoverage:
+    line_number: int
+    hits: int                   # 0 = not executed
+    branch_total: int = 0       # 0 = not a branch point
+    branch_covered: int = 0
+
+    @property
+    def is_uncovered(self) -> bool:
+        return self.hits == 0
+
+    @property
+    def is_partial_branch(self) -> bool:
+        return self.branch_total > 0 and self.branch_covered < self.branch_total
+
+
+@dataclass
+class MethodCoverage:
+    name: str
+    descriptor: str
+    first_line: Optional[int]
+    missed_instructions: int
+    covered_instructions: int
+    missed_branches: int
+    covered_branches: int
+    uncovered_lines: list[int] = field(default_factory=list)
+    partial_branch_lines: list[int] = field(default_factory=list)
+
+    @property
+    def total_branches(self) -> int:
+        return self.missed_branches + self.covered_branches
+
+    @property
+    def is_fully_covered(self) -> bool:
+        return self.missed_instructions == 0 and self.missed_branches == 0
+
+    @property
+    def branch_coverage_pct(self) -> float:
+        total = self.total_branches
+        return 100.0 * self.covered_branches / total if total else 100.0
+
+    @property
+    def line_coverage_pct(self) -> float:
+        total = self.missed_instructions + self.covered_instructions
+        return 100.0 * self.covered_instructions / total if total else 100.0
+
+
+@dataclass
+class ClassCoverage:
+    class_name: str             # e.g. com/example/Foo
+    source_file: Optional[str]
+    methods: list[MethodCoverage] = field(default_factory=list)
+    all_lines: list[LineCoverage] = field(default_factory=list)
+
+    @property
+    def java_class_name(self) -> str:
+        return self.class_name.replace("/", ".")
+
+    @property
+    def source_path(self) -> Optional[str]:
+        """Best-guess relative source path."""
+        if self.source_file:
+            package = "/".join(self.class_name.split("/")[:-1])
+            return f"src/main/java/{package}/{self.source_file}" if package else f"src/main/java/{self.source_file}"
+        return None
+
+    @property
+    def uncovered_lines(self) -> list[int]:
+        return sorted({l.line_number for l in self.all_lines if l.is_uncovered})
+
+    @property
+    def partial_branch_lines(self) -> list[int]:
+        return sorted({l.line_number for l in self.all_lines if l.is_partial_branch})
+
+    @property
+    def missed_branches(self) -> int:
+        return sum(max(l.branch_total - l.branch_covered, 0) for l in self.all_lines)
+
+    @property
+    def total_branches(self) -> int:
+        return sum(l.branch_total for l in self.all_lines)
+
+    @property
+    def covered_branches(self) -> int:
+        return self.total_branches - self.missed_branches
+
+    @property
+    def missed_lines(self) -> int:
+        return len(self.uncovered_lines)
+
+    @property
+    def total_lines(self) -> int:
+        return len(self.all_lines)
+
+    @property
+    def covered_lines(self) -> int:
+        return self.total_lines - self.missed_lines
+
+    @property
+    def has_gaps(self) -> bool:
+        return bool(self.uncovered_lines or self.partial_branch_lines)
+
+
+# ---------------------------------------------------------------------------
+# Parser
+# ---------------------------------------------------------------------------
+
+def parse_jacoco_xml(xml_path: str) -> list[ClassCoverage]:
+    """Parse a JaCoCo XML report into ClassCoverage objects."""
+    tree = ET.parse(xml_path)
+    root = tree.getroot()
+
+    results: list[ClassCoverage] = []
+
+    for package in root.iter("package"):
+        for cls_elem in package.findall("class"):
+            class_name = cls_elem.get("name", "")
+            source_file = cls_elem.get("sourcefilename")
+
+            # Build method map from <method> children
+            methods: list[MethodCoverage] = []
+            for m in cls_elem.findall("method"):
+                counters = {c.get("type"): c for c in m.findall("counter")}
+
+                def _missed(t): return int(counters[t].get("missed", 0)) if t in counters else 0
+                def _covered(t): return int(counters[t].get("covered", 0)) if t in counters else 0
+
+                methods.append(MethodCoverage(
+                    name=m.get("name", ""),
+                    descriptor=m.get("desc", ""),
+                    first_line=int(m.get("line")) if m.get("line") else None,
+                    missed_instructions=_missed("INSTRUCTION"),
+                    covered_instructions=_covered("INSTRUCTION"),
+                    missed_branches=_missed("BRANCH"),
+                    covered_branches=_covered("BRANCH"),
+                ))
+
+            cc = ClassCoverage(
+                class_name=class_name,
+                source_file=source_file,
+                methods=methods,
+            )
+
+            # Per-line data lives in the matching <sourcefile> element
+            source_file_elem = package.find(f"sourcefile[@name='{source_file}']") if source_file else None
+            if source_file_elem is not None:
+                for line_elem in source_file_elem.findall("line"):
+                    nr = int(line_elem.get("nr", 0))
+                    mi = int(line_elem.get("mi", 0))   # missed instructions
+                    ci = int(line_elem.get("ci", 0))   # covered instructions
+                    mb = int(line_elem.get("mb", 0))   # missed branches
+                    cb = int(line_elem.get("cb", 0))   # covered branches
+                    hits = ci  # ci > 0 means line was executed at least once
+                    cc.all_lines.append(LineCoverage(
+                        line_number=nr,
+                        hits=hits,
+                        branch_total=mb + cb,
+                        branch_covered=cb,
+                    ))
+
+            if cc.has_gaps:
+                results.append(cc)
+
+    return results
+
+
+# ---------------------------------------------------------------------------
+# Formatters
+# ---------------------------------------------------------------------------
+
+def _compact_ranges(numbers: list[int]) -> str:
+    """Turn [1,2,3,5,7,8,9] -> '1-3, 5, 7-9'"""
+    if not numbers:
+        return ""
+    ranges = []
+    start = prev = numbers[0]
+    for n in numbers[1:]:
+        if n == prev + 1:
+            prev = n
+        else:
+            ranges.append(f"{start}-{prev}" if start != prev else str(start))
+            start = prev = n
+    ranges.append(f"{start}-{prev}" if start != prev else str(start))
+    return ", ".join(ranges)
+
+
+def format_agent(classes: list[ClassCoverage]) -> str:
+    """
+    Output optimised for Claude Code agents:
+    – structured, machine-readable yet human-legible
+    – uses file paths and line numbers agents can act on
+    – groups by file, sorts by severity (most gaps first)
+    """
+    lines: list[str] = []
+    lines.append("# JaCoCo Coverage Gaps — Agent Action Report")
+    lines.append("")
+    lines.append("## Summary")
+    total_uncovered = sum(c.missed_lines for c in classes)
+    total_partial = sum(len(c.partial_branch_lines) for c in classes)
+    total_missed_branches = sum(c.missed_branches for c in classes)
+    lines.append(f"- Files with gaps : {len(classes)}")
+    lines.append(f"- Uncovered lines : {total_uncovered}")
+    lines.append(f"- Partial branches: {total_partial} lines affected")
+    lines.append(f"- Missed branches : {total_missed_branches} branch paths")
+    lines.append("")
+    lines.append("---")
+    lines.append("")
+    lines.append("## Files Requiring Tests")
+    lines.append("")
+    lines.append("> Each entry lists the SOURCE FILE PATH, the LINE NUMBERS that need")
+    lines.append("> coverage, and the METHODS that contain those gaps.")
+    lines.append("> Write or extend unit/integration tests to exercise these paths.")
+    lines.append("")
+
+    # Sort: most uncovered lines first
+    sorted_classes = sorted(classes, key=lambda c: -(c.missed_lines + len(c.partial_branch_lines)))
+
+    for cls in sorted_classes:
+        source = cls.source_path or f"(source unknown) {cls.java_class_name}"
+        lines.append(f"### `{source}`")
+        lines.append(f"**Class**: `{cls.java_class_name}`")
+        lines.append("")
+
+        if cls.uncovered_lines:
+            lines.append(f"#### ❌ Uncovered Lines")
+            lines.append(f"Lines not executed at all: `{_compact_ranges(cls.uncovered_lines)}`")
+            lines.append("")
+            lines.append("**Methods with uncovered lines:**")
+            for method in cls.methods:
+                uncov = [l for l in cls.uncovered_lines
+                         if method.first_line and l >= method.first_line]
+                # heuristic: only attribute if there are uncovered lines near the method start
+                if method.missed_instructions > 0:
+                    sig = f"`{method.name}{method.descriptor}`"
+                    pct = method.line_coverage_pct
+                    lines.append(f"  - {sig} — {pct:.0f}% instruction coverage")
+            lines.append("")
+
+        if cls.partial_branch_lines:
+            lines.append(f"#### ⚠️  Partial Branch Coverage (Missing Conditional Paths)")
+            lines.append(f"Lines where not all branches are taken: `{_compact_ranges(cls.partial_branch_lines)}`")
+            lines.append("")
+            lines.append("**Methods with branch gaps:**")
+            for method in cls.methods:
+                if method.missed_branches > 0:
+                    sig = f"`{method.name}{method.descriptor}`"
+                    pct = method.branch_coverage_pct
+                    missing = method.missed_branches
+                    lines.append(f"  - {sig} — {pct:.0f}% branch coverage ({missing} branch path(s) never taken)")
+            lines.append("")
+
+        lines.append("**Action**: Add tests that exercise the above lines/branches.")
+        lines.append("")
+        lines.append("---")
+        lines.append("")
+
+    lines.append("## Quick Reference: All Uncovered Locations")
+    lines.append("")
+    lines.append("Copy-paste friendly list for IDE navigation or grep:")
+    lines.append("")
+    lines.append("```")
+    for cls in sorted_classes:
+        src = cls.source_path or cls.java_class_name
+        if cls.uncovered_lines:
+            for ln in cls.uncovered_lines:
+                lines.append(f"{src}:{ln}  # uncovered line")
+        if cls.partial_branch_lines:
+            for ln in cls.partial_branch_lines:
+                lines.append(f"{src}:{ln}  # partial branch")
+    lines.append("```")
+
+    return "\n".join(lines)
+
+
+def format_json(classes: list[ClassCoverage]) -> str:
+    out = []
+    for cls in classes:
+        out.append({
+            "class": cls.java_class_name,
+            "source_path": cls.source_path,
+            "uncovered_lines": cls.uncovered_lines,
+            "partial_branch_lines": cls.partial_branch_lines,
+            "missed_branches": cls.missed_branches,
+            "methods": [
+                {
+                    "name": m.name,
+                    "descriptor": m.descriptor,
+                    "first_line": m.first_line,
+                    "line_coverage_pct": round(m.line_coverage_pct, 1),
+                    "branch_coverage_pct": round(m.branch_coverage_pct, 1),
+                    "missed_branches": m.missed_branches,
+                    "missed_instructions": m.missed_instructions,
+                }
+                for m in cls.methods
+                if not m.is_fully_covered
+            ],
+        })
+    return json.dumps(out, indent=2)
+
+
+def format_markdown(classes: list[ClassCoverage]) -> str:
+    lines: list[str] = []
+    lines.append("# JaCoCo Missing Coverage Report\n")
+    for cls in sorted(classes, key=lambda c: cls.java_class_name):
+        lines.append(f"## {cls.java_class_name}")
+        if cls.source_path:
+            lines.append(f"**File**: `{cls.source_path}`\n")
+        if cls.uncovered_lines:
+            lines.append(f"**Uncovered lines**: {_compact_ranges(cls.uncovered_lines)}\n")
+        if cls.partial_branch_lines:
+            lines.append(f"**Partial branches at lines**: {_compact_ranges(cls.partial_branch_lines)}\n")
+        lines.append("| Method | Line Coverage | Branch Coverage | Missed Branches |")
+        lines.append("|--------|--------------|-----------------|-----------------|")
+        for m in cls.methods:
+            if not m.is_fully_covered:
+                lines.append(
+                    f"| `{m.name}` | {m.line_coverage_pct:.0f}% | "
+                    f"{m.branch_coverage_pct:.0f}% | {m.missed_branches} |"
+                )
+        lines.append("")
+    return "\n".join(lines)
+
+
+# ---------------------------------------------------------------------------
+# Entry point
+# ---------------------------------------------------------------------------
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Report missing line & branch coverage from a JaCoCo XML report."
+    )
+    parser.add_argument("xml_file", help="Path to jacoco.xml report file")
+    parser.add_argument(
+        "--output", "-o",
+        choices=["agent", "json", "markdown"],
+        default="json",
+        help="Output format (default: agent)",
+    )
+    parser.add_argument(
+        "--min-coverage",
+        type=float,
+        default=0.0,
+        help="Only report classes below this %% line coverage (0 = report all gaps)",
+    )
+    parser.add_argument(
+        "--package-filter", "-p",
+        default=None,
+        help="Only report classes in this package prefix (e.g. com/example/service)",
+    )
+    args = parser.parse_args()
+
+    xml_path = Path(args.xml_file)
+    if not xml_path.exists():
+        print(f"ERROR: File not found: {xml_path}", file=sys.stderr)
+        sys.exit(1)
+
+    classes = parse_jacoco_xml(str(xml_path))
+
+    # Apply package filter
+    if args.package_filter:
+        prefix = args.package_filter.replace(".", "/")
+        classes = [c for c in classes if c.class_name.startswith(prefix)]
+
+    # Apply min-coverage filter
+    if args.min_coverage > 0:
+        def _line_pct(c: ClassCoverage) -> float:
+            total = c.total_lines
+            return 100.0 * c.covered_lines / total if total else 100.0
+
+        classes = [c for c in classes if _line_pct(c) < args.min_coverage]
+
+    if not classes:
+        print("✅ No coverage gaps found matching the given filters.")
+        return
+
+    if args.output == "agent":
+        print(format_agent(classes))
+    elif args.output == "json":
+        print(format_json(classes))
+    elif args.output == "markdown":
+        print(format_markdown(classes))
+
+
+if __name__ == "__main__":
+    main()

modules/api/CHANGELOG.md

@@ -1,5 +0,0 @@
-##  (2026-03-27)
-##  (2026-03-28)
-##  (2026-03-28)
-##  (2026-03-29)
-##  (2026-03-31)

modules/api/build.gradle.kts

@@ -49,10 +49,9 @@ dependencies {
 
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
     testImplementation("co.helmethair:scalatest-junit-runner:${versions["SCALATEST_JUNIT"]!!}")
-
-    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }
 
 tasks.test {

modules/api/src/main/scala/de/nowchess/api/board/Board.scala

@@ -8,12 +8,10 @@ object Board:
 
   extension (b: Board)
     def pieceAt(sq: Square): Option[Piece] = b.get(sq)
-    def updated(sq: Square, piece: Piece): Board = b.updated(sq, piece)
-    def removed(sq: Square): Board = b.removed(sq)
     def withMove(from: Square, to: Square): (Board, Option[Piece]) =
       val captured = b.get(to)
-      val updatedBoard = b.removed(from).updated(to, b(from))
-      (updatedBoard, captured)
+      val updated  = b.removed(from).updated(to, b(from))
+      (updated, captured)
     def pieces: Map[Square, Piece] = b
 
   val initial: Board =

modules/api/src/test/scala/de/nowchess/api/board/BoardTest.scala

@@ -1,122 +0,0 @@
-package de.nowchess.api.board
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class BoardTest extends AnyFunSuite with Matchers:
-
-  private val e2 = Square(File.E, Rank.R2)
-  private val e4 = Square(File.E, Rank.R4)
-  private val d7 = Square(File.D, Rank.R7)
-
-  test("pieceAt returns Some for occupied square") {
-    Board.initial.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
-  }
-
-  test("pieceAt returns None for empty square") {
-    Board.initial.pieceAt(e4) shouldBe None
-  }
-
-  test("withMove moves piece and vacates origin") {
-    val (board, captured) = Board.initial.withMove(e2, e4)
-    captured shouldBe None
-    board.pieceAt(e4) shouldBe Some(Piece.WhitePawn)
-    board.pieceAt(e2) shouldBe None
-  }
-
-  test("withMove returns captured piece when destination is occupied") {
-    val from = Square(File.A, Rank.R1)
-    val to   = Square(File.A, Rank.R8)
-    val b    = Board(Map(from -> Piece.WhiteRook, to -> Piece.BlackRook))
-    val (board, captured) = b.withMove(from, to)
-    captured shouldBe Some(Piece.BlackRook)
-    board.pieceAt(to) shouldBe Some(Piece.WhiteRook)
-    board.pieceAt(from) shouldBe None
-  }
-
-  test("pieces returns the underlying map") {
-    val map = Map(e2 -> Piece.WhitePawn)
-    val b   = Board(map)
-    b.pieces shouldBe map
-  }
-
-  test("Board.apply constructs board from map") {
-    val map = Map(e2 -> Piece.WhitePawn)
-    val b   = Board(map)
-    b.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
-  }
-
-  test("initial board has 32 pieces") {
-    Board.initial.pieces should have size 32
-  }
-
-  test("initial board has 16 white pieces") {
-    Board.initial.pieces.values.count(_.color == Color.White) shouldBe 16
-  }
-
-  test("initial board has 16 black pieces") {
-    Board.initial.pieces.values.count(_.color == Color.Black) shouldBe 16
-  }
-
-  test("initial board white pawns on rank 2") {
-    File.values.foreach { file =>
-      Board.initial.pieceAt(Square(file, Rank.R2)) shouldBe Some(Piece.WhitePawn)
-    }
-  }
-
-  test("initial board black pawns on rank 7") {
-    File.values.foreach { file =>
-      Board.initial.pieceAt(Square(file, Rank.R7)) shouldBe Some(Piece.BlackPawn)
-    }
-  }
-
-  test("initial board white back rank") {
-    val expectedBackRank = Vector(
-      PieceType.Rook, PieceType.Knight, PieceType.Bishop, PieceType.Queen,
-      PieceType.King, PieceType.Bishop, PieceType.Knight, PieceType.Rook
-    )
-    File.values.zipWithIndex.foreach { (file, i) =>
-      Board.initial.pieceAt(Square(file, Rank.R1)) shouldBe
-        Some(Piece(Color.White, expectedBackRank(i)))
-    }
-  }
-
-  test("initial board black back rank") {
-    val expectedBackRank = Vector(
-      PieceType.Rook, PieceType.Knight, PieceType.Bishop, PieceType.Queen,
-      PieceType.King, PieceType.Bishop, PieceType.Knight, PieceType.Rook
-    )
-    File.values.zipWithIndex.foreach { (file, i) =>
-      Board.initial.pieceAt(Square(file, Rank.R8)) shouldBe
-        Some(Piece(Color.Black, expectedBackRank(i)))
-    }
-  }
-
-  test("ranks 3-6 are empty on initial board") {
-    val emptyRanks = Seq(Rank.R3, Rank.R4, Rank.R5, Rank.R6)
-    for
-      rank <- emptyRanks
-      file <- File.values
-    do
-      Board.initial.pieceAt(Square(file, rank)) shouldBe None
-  }
-
-  test("updated adds or replaces piece at square") {
-    val b = Board(Map(e2 -> Piece.WhitePawn))
-    val updated = b.updated(e4, Piece.WhiteKnight)
-    updated.pieceAt(e2) shouldBe Some(Piece.WhitePawn)
-    updated.pieceAt(e4) shouldBe Some(Piece.WhiteKnight)
-  }
-
-  test("updated replaces existing piece") {
-    val b = Board(Map(e2 -> Piece.WhitePawn))
-    val updated = b.updated(e2, Piece.WhiteKnight)
-    updated.pieceAt(e2) shouldBe Some(Piece.WhiteKnight)
-  }
-
-  test("removed deletes piece from board") {
-    val b = Board(Map(e2 -> Piece.WhitePawn, e4 -> Piece.WhiteKnight))
-    val removed = b.removed(e2)
-    removed.pieceAt(e2) shouldBe None
-    removed.pieceAt(e4) shouldBe Some(Piece.WhiteKnight)
-  }

modules/api/src/test/scala/de/nowchess/api/board/ColorTest.scala

@@ -1,22 +0,0 @@
-package de.nowchess.api.board
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class ColorTest extends AnyFunSuite with Matchers:
-
-  test("White.opposite returns Black") {
-    Color.White.opposite shouldBe Color.Black
-  }
-
-  test("Black.opposite returns White") {
-    Color.Black.opposite shouldBe Color.White
-  }
-
-  test("White.label returns 'White'") {
-    Color.White.label shouldBe "White"
-  }
-
-  test("Black.label returns 'Black'") {
-    Color.Black.label shouldBe "Black"
-  }

modules/api/src/test/scala/de/nowchess/api/board/PieceTest.scala

@@ -1,60 +0,0 @@
-package de.nowchess.api.board
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class PieceTest extends AnyFunSuite with Matchers:
-
-  test("Piece holds color and pieceType") {
-    val p = Piece(Color.White, PieceType.Queen)
-    p.color    shouldBe Color.White
-    p.pieceType shouldBe PieceType.Queen
-  }
-
-  test("WhitePawn convenience constant") {
-    Piece.WhitePawn shouldBe Piece(Color.White, PieceType.Pawn)
-  }
-
-  test("WhiteKnight convenience constant") {
-    Piece.WhiteKnight shouldBe Piece(Color.White, PieceType.Knight)
-  }
-
-  test("WhiteBishop convenience constant") {
-    Piece.WhiteBishop shouldBe Piece(Color.White, PieceType.Bishop)
-  }
-
-  test("WhiteRook convenience constant") {
-    Piece.WhiteRook shouldBe Piece(Color.White, PieceType.Rook)
-  }
-
-  test("WhiteQueen convenience constant") {
-    Piece.WhiteQueen shouldBe Piece(Color.White, PieceType.Queen)
-  }
-
-  test("WhiteKing convenience constant") {
-    Piece.WhiteKing shouldBe Piece(Color.White, PieceType.King)
-  }
-
-  test("BlackPawn convenience constant") {
-    Piece.BlackPawn shouldBe Piece(Color.Black, PieceType.Pawn)
-  }
-
-  test("BlackKnight convenience constant") {
-    Piece.BlackKnight shouldBe Piece(Color.Black, PieceType.Knight)
-  }
-
-  test("BlackBishop convenience constant") {
-    Piece.BlackBishop shouldBe Piece(Color.Black, PieceType.Bishop)
-  }
-
-  test("BlackRook convenience constant") {
-    Piece.BlackRook shouldBe Piece(Color.Black, PieceType.Rook)
-  }
-
-  test("BlackQueen convenience constant") {
-    Piece.BlackQueen shouldBe Piece(Color.Black, PieceType.Queen)
-  }
-
-  test("BlackKing convenience constant") {
-    Piece.BlackKing shouldBe Piece(Color.Black, PieceType.King)
-  }

modules/api/src/test/scala/de/nowchess/api/board/PieceTypeTest.scala

@@ -1,30 +0,0 @@
-package de.nowchess.api.board
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class PieceTypeTest extends AnyFunSuite with Matchers:
-
-  test("Pawn.label returns 'Pawn'") {
-    PieceType.Pawn.label shouldBe "Pawn"
-  }
-
-  test("Knight.label returns 'Knight'") {
-    PieceType.Knight.label shouldBe "Knight"
-  }
-
-  test("Bishop.label returns 'Bishop'") {
-    PieceType.Bishop.label shouldBe "Bishop"
-  }
-
-  test("Rook.label returns 'Rook'") {
-    PieceType.Rook.label shouldBe "Rook"
-  }
-
-  test("Queen.label returns 'Queen'") {
-    PieceType.Queen.label shouldBe "Queen"
-  }
-
-  test("King.label returns 'King'") {
-    PieceType.King.label shouldBe "King"
-  }

modules/api/src/test/scala/de/nowchess/api/board/SquareTest.scala

@@ -1,62 +0,0 @@
-package de.nowchess.api.board
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class SquareTest extends AnyFunSuite with Matchers:
-
-  test("Square.toString produces lowercase file and rank number") {
-    Square(File.E, Rank.R4).toString shouldBe "e4"
-  }
-
-  test("Square.toString for a1") {
-    Square(File.A, Rank.R1).toString shouldBe "a1"
-  }
-
-  test("Square.toString for h8") {
-    Square(File.H, Rank.R8).toString shouldBe "h8"
-  }
-
-  test("fromAlgebraic parses valid square e4") {
-    Square.fromAlgebraic("e4") shouldBe Some(Square(File.E, Rank.R4))
-  }
-
-  test("fromAlgebraic parses valid square a1") {
-    Square.fromAlgebraic("a1") shouldBe Some(Square(File.A, Rank.R1))
-  }
-
-  test("fromAlgebraic parses valid square h8") {
-    Square.fromAlgebraic("h8") shouldBe Some(Square(File.H, Rank.R8))
-  }
-
-  test("fromAlgebraic is case-insensitive for file") {
-    Square.fromAlgebraic("E4") shouldBe Some(Square(File.E, Rank.R4))
-  }
-
-  test("fromAlgebraic returns None for empty string") {
-    Square.fromAlgebraic("") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for string too short") {
-    Square.fromAlgebraic("e") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for string too long") {
-    Square.fromAlgebraic("e42") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for invalid file character") {
-    Square.fromAlgebraic("z4") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for non-digit rank") {
-    Square.fromAlgebraic("ex") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for rank 0") {
-    Square.fromAlgebraic("e0") shouldBe None
-  }
-
-  test("fromAlgebraic returns None for rank 9") {
-    Square.fromAlgebraic("e9") shouldBe None
-  }

modules/api/src/test/scala/de/nowchess/api/game/GameStateTest.scala

@@ -1,77 +0,0 @@
-package de.nowchess.api.game
-
-import de.nowchess.api.board.Color
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameStateTest extends AnyFunSuite with Matchers:
-
-  test("CastlingRights.None has both flags false") {
-    CastlingRights.None.kingSide  shouldBe false
-    CastlingRights.None.queenSide shouldBe false
-  }
-
-  test("CastlingRights.Both has both flags true") {
-    CastlingRights.Both.kingSide  shouldBe true
-    CastlingRights.Both.queenSide shouldBe true
-  }
-
-  test("CastlingRights constructor sets fields") {
-    val cr = CastlingRights(kingSide = true, queenSide = false)
-    cr.kingSide  shouldBe true
-    cr.queenSide shouldBe false
-  }
-
-  test("GameResult cases exist") {
-    GameResult.WhiteWins shouldBe GameResult.WhiteWins
-    GameResult.BlackWins shouldBe GameResult.BlackWins
-    GameResult.Draw      shouldBe GameResult.Draw
-  }
-
-  test("GameStatus.NotStarted") {
-    GameStatus.NotStarted shouldBe GameStatus.NotStarted
-  }
-
-  test("GameStatus.InProgress") {
-    GameStatus.InProgress shouldBe GameStatus.InProgress
-  }
-
-  test("GameStatus.Finished carries result") {
-    val status = GameStatus.Finished(GameResult.Draw)
-    status shouldBe GameStatus.Finished(GameResult.Draw)
-    status match
-      case GameStatus.Finished(r) => r shouldBe GameResult.Draw
-      case _                      => fail("expected Finished")
-  }
-
-  test("GameState.initial has standard FEN piece placement") {
-    GameState.initial.piecePlacement shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-  }
-
-  test("GameState.initial active color is White") {
-    GameState.initial.activeColor shouldBe Color.White
-  }
-
-  test("GameState.initial white has full castling rights") {
-    GameState.initial.castlingWhite shouldBe CastlingRights.Both
-  }
-
-  test("GameState.initial black has full castling rights") {
-    GameState.initial.castlingBlack shouldBe CastlingRights.Both
-  }
-
-  test("GameState.initial en-passant target is None") {
-    GameState.initial.enPassantTarget shouldBe None
-  }
-
-  test("GameState.initial half-move clock is 0") {
-    GameState.initial.halfMoveClock shouldBe 0
-  }
-
-  test("GameState.initial full-move number is 1") {
-    GameState.initial.fullMoveNumber shouldBe 1
-  }
-
-  test("GameState.initial status is InProgress") {
-    GameState.initial.status shouldBe GameStatus.InProgress
-  }

modules/api/src/test/scala/de/nowchess/api/move/MoveTest.scala

@@ -1,56 +0,0 @@
-package de.nowchess.api.move
-
-import de.nowchess.api.board.{File, Rank, Square}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveTest extends AnyFunSuite with Matchers:
-
-  private val e2 = Square(File.E, Rank.R2)
-  private val e4 = Square(File.E, Rank.R4)
-
-  test("Move defaults moveType to Normal") {
-    val m = Move(e2, e4)
-    m.moveType shouldBe MoveType.Normal
-  }
-
-  test("Move stores from and to squares") {
-    val m = Move(e2, e4)
-    m.from shouldBe e2
-    m.to   shouldBe e4
-  }
-
-  test("Move with CastleKingside moveType") {
-    val m = Move(e2, e4, MoveType.CastleKingside)
-    m.moveType shouldBe MoveType.CastleKingside
-  }
-
-  test("Move with CastleQueenside moveType") {
-    val m = Move(e2, e4, MoveType.CastleQueenside)
-    m.moveType shouldBe MoveType.CastleQueenside
-  }
-
-  test("Move with EnPassant moveType") {
-    val m = Move(e2, e4, MoveType.EnPassant)
-    m.moveType shouldBe MoveType.EnPassant
-  }
-
-  test("Move with Promotion to Queen") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Queen))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Queen)
-  }
-
-  test("Move with Promotion to Knight") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Knight))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Knight)
-  }
-
-  test("Move with Promotion to Bishop") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Bishop))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Bishop)
-  }
-
-  test("Move with Promotion to Rook") {
-    val m = Move(e2, e4, MoveType.Promotion(PromotionPiece.Rook))
-    m.moveType shouldBe MoveType.Promotion(PromotionPiece.Rook)
-  }

modules/api/src/test/scala/de/nowchess/api/player/PlayerInfoTest.scala

@@ -1,23 +0,0 @@
-package de.nowchess.api.player
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class PlayerInfoTest extends AnyFunSuite with Matchers:
-
-  test("PlayerId.apply wraps a string") {
-    val id = PlayerId("player-123")
-    id.value shouldBe "player-123"
-  }
-
-  test("PlayerId.value unwraps to original string") {
-    val raw = "abc-456"
-    PlayerId(raw).value shouldBe raw
-  }
-
-  test("PlayerInfo holds id and displayName") {
-    val id   = PlayerId("p1")
-    val info = PlayerInfo(id, "Magnus")
-    info.id.value      shouldBe "p1"
-    info.displayName   shouldBe "Magnus"
-  }

modules/api/src/test/scala/de/nowchess/api/response/ApiResponseTest.scala

@@ -1,62 +0,0 @@
-package de.nowchess.api.response
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class ApiResponseTest extends AnyFunSuite with Matchers:
-
-  test("ApiResponse.Success carries data") {
-    val r = ApiResponse.Success(42)
-    r.data shouldBe 42
-  }
-
-  test("ApiResponse.Failure carries error list") {
-    val err = ApiError("CODE", "msg")
-    val r   = ApiResponse.Failure(List(err))
-    r.errors shouldBe List(err)
-  }
-
-  test("ApiResponse.error creates single-error Failure") {
-    val err = ApiError("NOT_FOUND", "not found")
-    val f   = ApiResponse.error(err)
-    f shouldBe ApiResponse.Failure(List(err))
-  }
-
-  test("ApiError holds code and message") {
-    val e = ApiError("CODE", "message")
-    e.code    shouldBe "CODE"
-    e.message shouldBe "message"
-    e.field   shouldBe None
-  }
-
-  test("ApiError holds optional field") {
-    val e = ApiError("INVALID", "bad value", Some("email"))
-    e.field shouldBe Some("email")
-  }
-
-  test("Pagination.totalPages with exact division") {
-    Pagination(page = 0, pageSize = 10, totalItems = 30).totalPages shouldBe 3
-  }
-
-  test("Pagination.totalPages rounds up") {
-    Pagination(page = 0, pageSize = 10, totalItems = 25).totalPages shouldBe 3
-  }
-
-  test("Pagination.totalPages is 0 when totalItems is 0") {
-    Pagination(page = 0, pageSize = 10, totalItems = 0).totalPages shouldBe 0
-  }
-
-  test("Pagination.totalPages is 0 when pageSize is 0") {
-    Pagination(page = 0, pageSize = 0, totalItems = 100).totalPages shouldBe 0
-  }
-
-  test("Pagination.totalPages is 0 when pageSize is negative") {
-    Pagination(page = 0, pageSize = -1, totalItems = 100).totalPages shouldBe 0
-  }
-
-  test("PagedResponse holds items and pagination") {
-    val pagination = Pagination(page = 1, pageSize = 5, totalItems = 20)
-    val pr         = PagedResponse(List("a", "b"), pagination)
-    pr.items      shouldBe List("a", "b")
-    pr.pagination shouldBe pagination
-  }

modules/api/versions.env

@@ -1,3 +0,0 @@
-MAJOR=0
-MINOR=0
-PATCH=5

modules/core/CHANGELOG.md

@@ -1,81 +0,0 @@
-##  (2026-03-27)
-
-### Features
-
-* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
-* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
-* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
-* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
-* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
-
-### Bug Fixes
-
-* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
-* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
-* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
-##  (2026-03-28)
-
-### Features
-
-* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
-* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
-* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
-* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
-* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
-
-### Bug Fixes
-
-* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
-* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
-* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
-##  (2026-03-29)
-
-### Features
-
-* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
-* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
-* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
-* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
-* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
-* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
-
-### Bug Fixes
-
-* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
-* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
-* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
-##  (2026-03-29)
-
-### Features
-
-* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
-* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
-* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
-* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
-* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
-* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
-* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
-
-### Bug Fixes
-
-* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
-* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
-* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))
-##  (2026-03-31)
-
-### Features
-
-* add GameRules stub with PositionStatus enum ([76d4168](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/76d4168038de23e5d6083d4e8f0504fbf31d15a3))
-* add MovedInCheck/Checkmate/Stalemate MoveResult variants (stub dispatch) ([8b7ec57](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/8b7ec57e5ea6ee1615a1883848a426dc07d26364))
-* implement GameRules with isInCheck, legalMoves, gameStatus ([94a02ff](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/94a02ff6849436d9496c70a0f16c21666dae8e4e))
-* implement legal castling ([#1](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/1)) ([00d326c](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/00d326c1ba67711fbe180f04e1100c3f01dd0254))
-* NCS-16 Core Separation via Patterns ([#10](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/10)) ([1361dfc](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/1361dfc89553b146864fb8ff3526cf12cf3f293a))
-* NCS-6 Implementing FEN & PGN ([#7](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/7)) ([f28e69d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f28e69dc181416aa2f221fdc4b45c2cda5efbf07))
-* NCS-9 En passant implementation ([#8](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/8)) ([919beb3](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/919beb3b4bfa8caf2f90976a415fe9b19b7e9747))
-* wire check/checkmate/stalemate into processMove and gameLoop ([5264a22](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/5264a225418b885c5e6ea6411b96f85e38837f6c))
-
-### Bug Fixes
-
-* add missing kings to gameLoop capture test board ([aedd787](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/aedd787b77203c2af934751dba7b784eaf165032))
-* correct test board positions and captureOutput/withInput interaction ([f0481e2](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/f0481e2561b779df00925b46ee281dc36a795150))
-* update main class path in build configuration and adjust VCS directory mapping ([7b1f8b1](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/7b1f8b117623d327232a1a92a8a44d18582e0189))

modules/core/build.gradle.kts

@@ -23,7 +23,7 @@ scoverage {
 }
 
 application {
-    mainClass.set("de.nowchess.chess.Main")
+    mainClass.set("de.nowchess.chess.chessMain")
 }
 
 tasks.withType<ScalaCompile> {
@@ -52,10 +52,9 @@ dependencies {
 
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
     testImplementation("co.helmethair:scalatest-junit-runner:${versions["SCALATEST_JUNIT"]!!}")
-
-    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }
 
 tasks.test {

modules/core/src/main/scala/de/nowchess/chess/Main.scala

@@ -0,0 +1,11 @@
+package de.nowchess.chess
+
+import de.nowchess.api.board.Color
+import de.nowchess.chess.controller.GameController
+import de.nowchess.chess.logic.GameContext
+
+object Main {
+  def main(args: Array[String]): Unit =
+    println("NowChess TUI — type moves in coordinate notation (e.g. e2e4). Type 'quit' to exit.")
+    GameController.gameLoop(GameContext.initial, Color.White)
+}

modules/core/src/main/scala/de/nowchess/chess/command/Command.scala

@@ -1,64 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, Board, Color, Piece}
-import de.nowchess.chess.logic.GameHistory
-
-/** Marker trait for all commands that can be executed and undone.
- *  Commands encapsulate user actions and game state transitions.
- */
-trait Command:
-  /** Execute the command and return true if successful, false otherwise. */
-  def execute(): Boolean
-
-  /** Undo the command and return true if successful, false otherwise. */
-  def undo(): Boolean
-
-  /** A human-readable description of this command. */
-  def description: String
-
-/** Command to move a piece from one square to another.
- *  Stores the move result so undo can restore previous state.
- */
-case class MoveCommand(
-  from: Square,
-  to: Square,
-  moveResult: Option[MoveResult] = None,
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
-) extends Command:
-
-  override def execute(): Boolean =
-    moveResult.isDefined
-
-  override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
-
-  override def description: String = s"Move from $from to $to"
-
-// Sealed hierarchy of move outcomes (for tracking state changes)
-sealed trait MoveResult
-object MoveResult:
-  case class Successful(newBoard: Board, newHistory: GameHistory, newTurn: Color, captured: Option[Piece]) extends MoveResult
-  case object InvalidFormat extends MoveResult
-  case object InvalidMove extends MoveResult
-
-/** Command to quit the game. */
-case class QuitCommand() extends Command:
-  override def execute(): Boolean = true
-  override def undo(): Boolean = false
-  override def description: String = "Quit game"
-
-/** Command to reset the board to initial position. */
-case class ResetCommand(
-  previousBoard: Option[Board] = None,
-  previousHistory: Option[GameHistory] = None,
-  previousTurn: Option[Color] = None
-) extends Command:
-
-  override def execute(): Boolean = true
-
-  override def undo(): Boolean =
-    previousBoard.isDefined && previousHistory.isDefined && previousTurn.isDefined
-
-  override def description: String = "Reset board"

modules/core/src/main/scala/de/nowchess/chess/command/CommandInvoker.scala

@@ -1,73 +0,0 @@
-package de.nowchess.chess.command
-
-/** Manages command execution and history for undo/redo support. */
-class CommandInvoker:
-  private val executedCommands = scala.collection.mutable.ListBuffer[Command]()
-  private var currentIndex = -1
-
-  /** Execute a command and add it to history.
-   *  Discards any redo history if not at the end of the stack.
-   */
-  def execute(command: Command): Boolean = synchronized {
-    if command.execute() then
-      // Remove any commands after current index (redo stack is discarded)
-      while currentIndex < executedCommands.size - 1 do
-        executedCommands.remove(executedCommands.size - 1)
-      executedCommands += command
-      currentIndex += 1
-      true
-    else
-      false
-  }
-
-  /** Undo the last executed command if possible. */
-  def undo(): Boolean = synchronized {
-    if currentIndex >= 0 && currentIndex < executedCommands.size then
-      val command = executedCommands(currentIndex)
-      if command.undo() then
-        currentIndex -= 1
-        true
-      else
-        false
-    else
-      false
-  }
-
-  /** Redo the next command in history if available. */
-  def redo(): Boolean = synchronized {
-    if currentIndex + 1 < executedCommands.size then
-      val command = executedCommands(currentIndex + 1)
-      if command.execute() then
-        currentIndex += 1
-        true
-      else
-        false
-    else
-      false
-  }
-
-  /** Get the history of all executed commands. */
-  def history: List[Command] = synchronized {
-    executedCommands.toList
-  }
-
-  /** Get the current position in command history. */
-  def getCurrentIndex: Int = synchronized {
-    currentIndex
-  }
-
-  /** Clear all command history. */
-  def clear(): Unit = synchronized {
-    executedCommands.clear()
-    currentIndex = -1
-  }
-
-  /** Check if undo is available. */
-  def canUndo: Boolean = synchronized {
-    currentIndex >= 0
-  }
-
-  /** Check if redo is available. */
-  def canRedo: Boolean = synchronized {
-    currentIndex + 1 < executedCommands.size
-  }

modules/core/src/main/scala/de/nowchess/chess/controller/GameController.scala

@@ -1,8 +1,10 @@
 package de.nowchess.chess.controller
 
-import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.*
+import scala.io.StdIn
+import de.nowchess.api.board.{Board, Color, File, Piece, Rank, Square}
+import de.nowchess.api.game.CastlingRights
+import de.nowchess.chess.logic.{GameContext, MoveValidator, GameRules, PositionStatus, CastleSide, withCastle}
+import de.nowchess.chess.view.Renderer
 
 // ---------------------------------------------------------------------------
 // Result ADT returned by the pure processMove function
@@ -15,16 +17,8 @@ object MoveResult:
   case object NoPiece                                                                   extends MoveResult
   case object WrongColor                                                                extends MoveResult
   case object IllegalMove                                                               extends MoveResult
-  case class  PromotionRequired(
-    from: Square,
-    to: Square,
-    boardBefore: Board,
-    historyBefore: GameHistory,
-    captured: Option[Piece],
-    turn: Color
-  ) extends MoveResult
-  case class  Moved(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color)      extends MoveResult
-  case class  MovedInCheck(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], newTurn: Color) extends MoveResult
+  case class  Moved(newCtx: GameContext, captured: Option[Piece], newTurn: Color)      extends MoveResult
+  case class  MovedInCheck(newCtx: GameContext, captured: Option[Piece], newTurn: Color) extends MoveResult
   case class  Checkmate(winner: Color)                                                  extends MoveResult
   case object Stalemate                                                                 extends MoveResult
 
@@ -37,66 +31,106 @@ object GameController:
   /** Pure function: interprets one raw input line against the current game context.
    *  Has no I/O side effects — all output must be handled by the caller.
    */
-  def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
+  def processMove(ctx: GameContext, turn: Color, raw: String): MoveResult =
     raw.trim match
-      case "quit" | "q" => MoveResult.Quit
+      case "quit" | "q" =>
+        MoveResult.Quit
       case trimmed =>
         Parser.parseMove(trimmed) match
-          case None              => MoveResult.InvalidFormat(trimmed)
-          case Some((from, to))  => validateAndApply(board, history, turn, from, to)
+          case None =>
+            MoveResult.InvalidFormat(trimmed)
+          case Some((from, to)) =>
+            ctx.board.pieceAt(from) match
+              case None =>
+                MoveResult.NoPiece
+              case Some(piece) if piece.color != turn =>
+                MoveResult.WrongColor
+              case Some(_) =>
+                if !MoveValidator.isLegal(ctx, from, to) then
+                  MoveResult.IllegalMove
+                else
+                  val castleOpt = if MoveValidator.isCastle(ctx.board, from, to)
+                                  then Some(MoveValidator.castleSide(from, to))
+                                  else None
+                  val (newBoard, captured) = castleOpt match
+                    case Some(side) => (ctx.board.withCastle(turn, side), None)
+                    case None       => ctx.board.withMove(from, to)
+                  val newCtx = applyRightsRevocation(
+                    ctx.copy(board = newBoard), turn, from, to, castleOpt
+                  )
+                  GameRules.gameStatus(newCtx, turn.opposite) match
+                    case PositionStatus.Normal  => MoveResult.Moved(newCtx, captured, turn.opposite)
+                    case PositionStatus.InCheck => MoveResult.MovedInCheck(newCtx, captured, turn.opposite)
+                    case PositionStatus.Mated   => MoveResult.Checkmate(turn)
+                    case PositionStatus.Drawn   => MoveResult.Stalemate
 
-  /** Apply a previously detected promotion move with the chosen piece.
-   *  Called after processMove returned PromotionRequired.
-   */
-  def completePromotion(
-    board: Board,
-    history: GameHistory,
+  private def applyRightsRevocation(
+    ctx: GameContext,
+    turn: Color,
     from: Square,
     to: Square,
-    piece: PromotionPiece,
-    turn: Color
-  ): MoveResult =
-    val (boardAfterMove, captured) = board.withMove(from, to)
-    val promotedPieceType = piece match
-      case PromotionPiece.Queen  => PieceType.Queen
-      case PromotionPiece.Rook   => PieceType.Rook
-      case PromotionPiece.Bishop => PieceType.Bishop
-      case PromotionPiece.Knight => PieceType.Knight
-    val newBoard    = boardAfterMove.updated(to, Piece(turn, promotedPieceType))
-    val newHistory  = history.addMove(from, to, None, Some(piece))
-    toMoveResult(newBoard, newHistory, captured, turn)
+    castle: Option[CastleSide]
+  ): GameContext =
+    // Step 1: Revoke all rights for a castling move (idempotent with step 2)
+    val ctx0 = castle.fold(ctx)(_ => ctx.withUpdatedRights(turn, CastlingRights.None))
 
-  // ---------------------------------------------------------------------------
-  // Private helpers
-  // ---------------------------------------------------------------------------
+    // Step 2: Source-square revocation
+    val ctx1 = from match
+      case Square(File.E, Rank.R1) => ctx0.withUpdatedRights(Color.White, CastlingRights.None)
+      case Square(File.E, Rank.R8) => ctx0.withUpdatedRights(Color.Black, CastlingRights.None)
+      case Square(File.A, Rank.R1) => ctx0.withUpdatedRights(Color.White, ctx0.whiteCastling.copy(queenSide = false))
+      case Square(File.H, Rank.R1) => ctx0.withUpdatedRights(Color.White, ctx0.whiteCastling.copy(kingSide  = false))
+      case Square(File.A, Rank.R8) => ctx0.withUpdatedRights(Color.Black, ctx0.blackCastling.copy(queenSide = false))
+      case Square(File.H, Rank.R8) => ctx0.withUpdatedRights(Color.Black, ctx0.blackCastling.copy(kingSide  = false))
+      case _                       => ctx0
 
-  private def validateAndApply(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
-    board.pieceAt(from) match
-      case None                              => MoveResult.NoPiece
-      case Some(piece) if piece.color != turn => MoveResult.WrongColor
-      case Some(_) =>
-        if !GameRules.legalMoves(board, history, turn).contains(from -> to) then MoveResult.IllegalMove
-        else if MoveValidator.isPromotionMove(board, from, to) then
-          MoveResult.PromotionRequired(from, to, board, history, board.pieceAt(to), turn)
-        else applyNormalMove(board, history, turn, from, to)
+    // Step 3: Destination-square revocation (enemy captures a rook on its home square)
+    to match
+      case Square(File.A, Rank.R1) => ctx1.withUpdatedRights(Color.White, ctx1.whiteCastling.copy(queenSide = false))
+      case Square(File.H, Rank.R1) => ctx1.withUpdatedRights(Color.White, ctx1.whiteCastling.copy(kingSide  = false))
+      case Square(File.A, Rank.R8) => ctx1.withUpdatedRights(Color.Black, ctx1.blackCastling.copy(queenSide = false))
+      case Square(File.H, Rank.R8) => ctx1.withUpdatedRights(Color.Black, ctx1.blackCastling.copy(kingSide  = false))
+      case _                       => ctx1
 
-  private def applyNormalMove(board: Board, history: GameHistory, turn: Color, from: Square, to: Square): MoveResult =
-    val castleOpt              = Option.when(MoveValidator.isCastle(board, from, to))(MoveValidator.castleSide(from, to))
-    val isEP                   = EnPassantCalculator.isEnPassant(board, history, from, to)
-    val (newBoard, captured)   = castleOpt match
-      case Some(side) => (board.withCastle(turn, side), None)
-      case None =>
-        val (b, cap) = board.withMove(from, to)
-        if isEP then
-          val capturedSq = EnPassantCalculator.capturedPawnSquare(to, turn)
-          (b.removed(capturedSq), board.pieceAt(capturedSq))
-        else (b, cap)
-    val newHistory = history.addMove(from, to, castleOpt)
-    toMoveResult(newBoard, newHistory, captured, turn)
-
-  private def toMoveResult(newBoard: Board, newHistory: GameHistory, captured: Option[Piece], turn: Color): MoveResult =
-    GameRules.gameStatus(newBoard, newHistory, turn.opposite) match
-      case PositionStatus.Normal  => MoveResult.Moved(newBoard, newHistory, captured, turn.opposite)
-      case PositionStatus.InCheck => MoveResult.MovedInCheck(newBoard, newHistory, captured, turn.opposite)
-      case PositionStatus.Mated   => MoveResult.Checkmate(turn)
-      case PositionStatus.Drawn   => MoveResult.Stalemate
+  /** Thin I/O shell: renders the board, reads a line, delegates to processMove,
+   *  prints the outcome, and recurses until the game ends.
+   */
+  def gameLoop(ctx: GameContext, turn: Color): Unit =
+    println()
+    print(Renderer.render(ctx.board))
+    println(s"${turn.label}'s turn. Enter move: ")
+    val input = Option(StdIn.readLine()).getOrElse("quit").trim
+    processMove(ctx, turn, input) match
+      case MoveResult.Quit =>
+        println("Game over. Goodbye!")
+      case MoveResult.InvalidFormat(raw) =>
+        println(s"Invalid move format '$raw'. Use coordinate notation, e.g. e2e4.")
+        gameLoop(ctx, turn)
+      case MoveResult.NoPiece =>
+        println(s"No piece on ${Parser.parseMove(input).map(_._1).fold("?")(_.toString)}.")
+        gameLoop(ctx, turn)
+      case MoveResult.WrongColor =>
+        println(s"That is not your piece.")
+        gameLoop(ctx, turn)
+      case MoveResult.IllegalMove =>
+        println(s"Illegal move.")
+        gameLoop(ctx, turn)
+      case MoveResult.Moved(newCtx, captured, newTurn) =>
+        val prevTurn = newTurn.opposite
+        captured.foreach: cap =>
+          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
+          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
+        gameLoop(newCtx, newTurn)
+      case MoveResult.MovedInCheck(newCtx, captured, newTurn) =>
+        val prevTurn = newTurn.opposite
+        captured.foreach: cap =>
+          val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
+          println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
+        println(s"${newTurn.label} is in check!")
+        gameLoop(newCtx, newTurn)
+      case MoveResult.Checkmate(winner) =>
+        println(s"Checkmate! ${winner.label} wins.")
+        gameLoop(GameContext.initial, Color.White)
+      case MoveResult.Stalemate =>
+        println("Stalemate! The game is a draw.")
+        gameLoop(GameContext.initial, Color.White)

modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala

@@ -1,286 +0,0 @@
-package de.nowchess.chess.engine
-
-import de.nowchess.api.board.{Board, Color, Piece, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, GameRules, PositionStatus}
-import de.nowchess.chess.controller.{GameController, Parser, MoveResult}
-import de.nowchess.chess.observer.*
-import de.nowchess.chess.command.{CommandInvoker, MoveCommand}
-
-/** Pure game engine that manages game state and notifies observers of state changes.
- *  This class is the single source of truth for the game state.
- *  All user interactions must go through this engine via Commands, and all state changes
- *  are communicated to observers via GameEvent notifications.
- */
-class GameEngine(
-  initialBoard: Board = Board.initial,
-  initialHistory: GameHistory = GameHistory.empty,
-  initialTurn: Color = Color.White,
-  completePromotionFn: (Board, GameHistory, Square, Square, PromotionPiece, Color) => MoveResult =
-    GameController.completePromotion
-) extends Observable:
-  private var currentBoard: Board = initialBoard
-  private var currentHistory: GameHistory = initialHistory
-  private var currentTurn: Color = initialTurn
-  private val invoker = new CommandInvoker()
-
-  /** Inner class for tracking pending promotion state */
-  private case class PendingPromotion(
-    from: Square, to: Square,
-    boardBefore: Board, historyBefore: GameHistory,
-    turn: Color
-  )
-
-  /** Current pending promotion, if any */
-  private var pendingPromotion: Option[PendingPromotion] = None
-
-  /** True if a pawn promotion move is pending and needs a piece choice. */
-  def isPendingPromotion: Boolean = synchronized { pendingPromotion.isDefined }
-
-  // Synchronized accessors for current state
-  def board: Board = synchronized { currentBoard }
-  def history: GameHistory = synchronized { currentHistory }
-  def turn: Color = synchronized { currentTurn }
-
-  /** Check if undo is available. */
-  def canUndo: Boolean = synchronized { invoker.canUndo }
-
-  /** Check if redo is available. */
-  def canRedo: Boolean = synchronized { invoker.canRedo }
-
-  /** Get the command history for inspection (testing/debugging). */
-  def commandHistory: List[de.nowchess.chess.command.Command] = synchronized { invoker.history }
-
-  /** Process a raw move input string and update game state if valid.
-   *  Notifies all observers of the outcome via GameEvent.
-   */
-  def processUserInput(rawInput: String): Unit = synchronized {
-    val trimmed = rawInput.trim.toLowerCase
-    trimmed match
-      case "quit" | "q" =>
-        // Client should handle quit logic; we just return
-        ()
-
-      case "undo" =>
-        performUndo()
-
-      case "redo" =>
-        performRedo()
-
-      case "" =>
-        val event = InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "Please enter a valid move or command."
-        )
-        notifyObservers(event)
-
-      case moveInput =>
-        // Try to parse as a move
-        Parser.parseMove(moveInput) match
-          case None =>
-            val event = InvalidMoveEvent(
-              currentBoard,
-              currentHistory,
-              currentTurn,
-              s"Invalid move format '$moveInput'. Use coordinate notation, e.g. e2e4."
-            )
-            notifyObservers(event)
-
-          case Some((from, to)) =>
-            // Create a move command with current state snapshot
-            val cmd = MoveCommand(
-              from = from,
-              to = to,
-              previousBoard = Some(currentBoard),
-              previousHistory = Some(currentHistory),
-              previousTurn = Some(currentTurn)
-            )
-
-            // Execute the move through GameController
-            GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput) match
-              case MoveResult.InvalidFormat(_) | MoveResult.NoPiece | MoveResult.WrongColor | MoveResult.IllegalMove | MoveResult.Quit =>
-                handleFailedMove(moveInput)
-
-              case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-                // Move succeeded - store result and execute through invoker
-                val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-                invoker.execute(updatedCmd)
-                updateGameState(newBoard, newHistory, newTurn)
-                emitMoveEvent(from.toString, to.toString, captured, newTurn)
-
-              case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-                // Move succeeded with check
-                val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-                invoker.execute(updatedCmd)
-                updateGameState(newBoard, newHistory, newTurn)
-                emitMoveEvent(from.toString, to.toString, captured, newTurn)
-                notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
-
-              case MoveResult.Checkmate(winner) =>
-                // Move resulted in checkmate
-                val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-                invoker.execute(updatedCmd)
-                currentBoard = Board.initial
-                currentHistory = GameHistory.empty
-                currentTurn = Color.White
-                notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
-
-              case MoveResult.Stalemate =>
-                // Move resulted in stalemate
-                val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-                invoker.execute(updatedCmd)
-                currentBoard = Board.initial
-                currentHistory = GameHistory.empty
-                currentTurn = Color.White
-                notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
-
-              case MoveResult.PromotionRequired(promFrom, promTo, boardBefore, histBefore, _, promotingTurn) =>
-                pendingPromotion = Some(PendingPromotion(promFrom, promTo, boardBefore, histBefore, promotingTurn))
-                notifyObservers(PromotionRequiredEvent(currentBoard, currentHistory, currentTurn, promFrom, promTo))
-  }
-
-  /** Undo the last move. */
-  def undo(): Unit = synchronized {
-    performUndo()
-  }
-
-  /** Redo the last undone move. */
-  def redo(): Unit = synchronized {
-    performRedo()
-  }
-
-  /** Apply a player's promotion piece choice.
-   *  Must only be called when isPendingPromotion is true.
-   */
-  def completePromotion(piece: PromotionPiece): Unit = synchronized {
-    pendingPromotion match
-      case None =>
-        notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "No promotion pending."))
-      case Some(pending) =>
-        pendingPromotion = None
-        val cmd = MoveCommand(
-          from = pending.from,
-          to = pending.to,
-          previousBoard = Some(pending.boardBefore),
-          previousHistory = Some(pending.historyBefore),
-          previousTurn = Some(pending.turn)
-        )
-        completePromotionFn(
-          pending.boardBefore, pending.historyBefore,
-          pending.from, pending.to, piece, pending.turn
-        ) match
-          case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-
-          case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(newBoard, newHistory, newTurn, captured)))
-            invoker.execute(updatedCmd)
-            updateGameState(newBoard, newHistory, newTurn)
-            emitMoveEvent(pending.from.toString, pending.to.toString, captured, newTurn)
-            notifyObservers(CheckDetectedEvent(currentBoard, currentHistory, currentTurn))
-
-          case MoveResult.Checkmate(winner) =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(CheckmateEvent(currentBoard, currentHistory, currentTurn, winner))
-
-          case MoveResult.Stalemate =>
-            val updatedCmd = cmd.copy(moveResult = Some(de.nowchess.chess.command.MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)))
-            invoker.execute(updatedCmd)
-            currentBoard = Board.initial
-            currentHistory = GameHistory.empty
-            currentTurn = Color.White
-            notifyObservers(StalemateEvent(currentBoard, currentHistory, currentTurn))
-
-          case _ =>
-            notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Error completing promotion."))
-  }
-
-  /** Reset the board to initial position. */
-  def reset(): Unit = synchronized {
-    currentBoard = Board.initial
-    currentHistory = GameHistory.empty
-    currentTurn = Color.White
-    invoker.clear()
-    notifyObservers(BoardResetEvent(
-      currentBoard,
-      currentHistory,
-      currentTurn
-    ))
-  }
-
-  // ──── Private Helpers ────
-
-  private def performUndo(): Unit =
-    if invoker.canUndo then
-      val cmd = invoker.history(invoker.getCurrentIndex)
-      (cmd: @unchecked) match
-        case moveCmd: MoveCommand =>
-          moveCmd.previousBoard.foreach(currentBoard = _)
-          moveCmd.previousHistory.foreach(currentHistory = _)
-          moveCmd.previousTurn.foreach(currentTurn = _)
-          invoker.undo()
-          notifyObservers(BoardResetEvent(currentBoard, currentHistory, currentTurn))
-    else
-      notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to undo."))
-
-  private def performRedo(): Unit =
-    if invoker.canRedo then
-      val cmd = invoker.history(invoker.getCurrentIndex + 1)
-      (cmd: @unchecked) match
-        case moveCmd: MoveCommand =>
-          for case de.nowchess.chess.command.MoveResult.Successful(nb, nh, nt, cap) <- moveCmd.moveResult do
-            updateGameState(nb, nh, nt)
-            invoker.redo()
-            emitMoveEvent(moveCmd.from.toString, moveCmd.to.toString, cap, nt)
-    else
-      notifyObservers(InvalidMoveEvent(currentBoard, currentHistory, currentTurn, "Nothing to redo."))
-
-  private def updateGameState(newBoard: Board, newHistory: GameHistory, newTurn: Color): Unit =
-    currentBoard = newBoard
-    currentHistory = newHistory
-    currentTurn = newTurn
-
-  private def emitMoveEvent(fromSq: String, toSq: String, captured: Option[Piece], newTurn: Color): Unit =
-    val capturedDesc = captured.map(c => s"${c.color.label} ${c.pieceType.label}")
-    notifyObservers(MoveExecutedEvent(
-      currentBoard,
-      currentHistory,
-      newTurn,
-      fromSq,
-      toSq,
-      capturedDesc
-    ))
-
-  private def handleFailedMove(moveInput: String): Unit =
-    (GameController.processMove(currentBoard, currentHistory, currentTurn, moveInput): @unchecked) match
-      case MoveResult.NoPiece =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "No piece on that square."
-        ))
-      case MoveResult.WrongColor =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "That is not your piece."
-        ))
-      case MoveResult.IllegalMove =>
-        notifyObservers(InvalidMoveEvent(
-          currentBoard,
-          currentHistory,
-          currentTurn,
-          "Illegal move."
-        ))
-

modules/core/src/main/scala/de/nowchess/chess/logic/CastleSide.scala

@@ -1,23 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-
-enum CastleSide:
-  case Kingside, Queenside
-
-extension (b: Board)
-  def withCastle(color: Color, side: CastleSide): Board =
-    val rank = if color == Color.White then Rank.R1 else Rank.R8
-    val kingFrom = Square(File.E, rank)
-    val (kingTo, rookFrom, rookTo) = side match
-      case CastleSide.Kingside =>
-        (Square(File.G, rank), Square(File.H, rank), Square(File.F, rank))
-      case CastleSide.Queenside =>
-        (Square(File.C, rank), Square(File.A, rank), Square(File.D, rank))
-
-    val king = b.pieceAt(kingFrom).get
-    val rook = b.pieceAt(rookFrom).get
-
-    b.removed(kingFrom).removed(rookFrom)
-      .updated(kingTo, king)
-      .updated(rookTo, rook)

modules/core/src/main/scala/de/nowchess/chess/logic/CastlingRightsCalculator.scala

@@ -1,31 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.{Color, File, Rank, Square}
-import de.nowchess.api.game.CastlingRights
-
-/** Derives castling rights from move history. */
-object CastlingRightsCalculator:
-
-  def deriveCastlingRights(history: GameHistory, color: Color): CastlingRights =
-    val (kingRow, kingsideRookFile, queensideRookFile) = color match
-      case Color.White => (Rank.R1, File.H, File.A)
-      case Color.Black => (Rank.R8, File.H, File.A)
-
-    // Check if king has moved
-    val kingHasMoved = history.moves.exists: move =>
-      move.from == Square(File.E, kingRow) || move.castleSide.isDefined
-
-    if kingHasMoved then
-      CastlingRights.None
-    else
-      // Check if kingside rook has moved or was captured
-      val kingsideLost = history.moves.exists: move =>
-        move.from == Square(kingsideRookFile, kingRow) ||
-        move.to == Square(kingsideRookFile, kingRow)
-
-      // Check if queenside rook has moved or was captured
-      val queensideLost = history.moves.exists: move =>
-        move.from == Square(queensideRookFile, kingRow) ||
-        move.to == Square(queensideRookFile, kingRow)
-
-      CastlingRights(kingSide = !kingsideLost, queenSide = !queensideLost)

modules/core/src/main/scala/de/nowchess/chess/logic/EnPassantCalculator.scala

@@ -1,32 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-
-object EnPassantCalculator:
-
-  /** Returns the en passant target square if the last move was a double pawn push.
-   *  The target is the square the pawn passed through (e.g. e2→e4 yields e3).
-   */
-  def enPassantTarget(board: Board, history: GameHistory): Option[Square] =
-    history.moves.lastOption.flatMap: move =>
-      val rankDiff = move.to.rank.ordinal - move.from.rank.ordinal
-      val isDoublePush = math.abs(rankDiff) == 2
-      val isPawn = board.pieceAt(move.to).exists(_.pieceType == PieceType.Pawn)
-      if isDoublePush && isPawn then
-        val midRankIdx = move.from.rank.ordinal + rankDiff / 2
-        Some(Square(move.to.file, Rank.values(midRankIdx)))
-      else None
-
-  /** True if moving from→to is an en passant capture. */
-  def isEnPassant(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
-    board.pieceAt(from).exists(_.pieceType == PieceType.Pawn) &&
-    enPassantTarget(board, history).contains(to) &&
-    math.abs(to.file.ordinal - from.file.ordinal) == 1
-
-  /** Returns the square of the pawn to remove when an en passant capture lands on `to`.
-   *  White captures upward → captured pawn is one rank below `to`.
-   *  Black captures downward → captured pawn is one rank above `to`.
-   */
-  def capturedPawnSquare(to: Square, color: Color): Square =
-    val capturedRankIdx = to.rank.ordinal + (if color == Color.White then -1 else 1)
-    Square(to.file, Rank.values(capturedRankIdx))

modules/core/src/main/scala/de/nowchess/chess/logic/GameContext.scala

@@ -0,0 +1,47 @@
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
+import de.nowchess.api.game.CastlingRights
+
+enum CastleSide:
+  case Kingside, Queenside
+
+case class GameContext(
+  board: Board,
+  whiteCastling: CastlingRights,
+  blackCastling: CastlingRights
+):
+  def castlingFor(color: Color): CastlingRights =
+    if color == Color.White then whiteCastling else blackCastling
+
+  def withUpdatedRights(color: Color, rights: CastlingRights): GameContext =
+    if color == Color.White then copy(whiteCastling = rights)
+    else copy(blackCastling = rights)
+
+object GameContext:
+  /** Convenience constructor for test boards: no castling rights on either side. */
+  def apply(board: Board): GameContext =
+    GameContext(board, CastlingRights.None, CastlingRights.None)
+
+  val initial: GameContext =
+    GameContext(Board.initial, CastlingRights.Both, CastlingRights.Both)
+
+extension (b: Board)
+  def withCastle(color: Color, side: CastleSide): Board =
+    val (kingFrom, kingTo, rookFrom, rookTo) = (color, side) match
+      case (Color.White, CastleSide.Kingside)  =>
+        (Square(File.E, Rank.R1), Square(File.G, Rank.R1),
+         Square(File.H, Rank.R1), Square(File.F, Rank.R1))
+      case (Color.White, CastleSide.Queenside) =>
+        (Square(File.E, Rank.R1), Square(File.C, Rank.R1),
+         Square(File.A, Rank.R1), Square(File.D, Rank.R1))
+      case (Color.Black, CastleSide.Kingside)  =>
+        (Square(File.E, Rank.R8), Square(File.G, Rank.R8),
+         Square(File.H, Rank.R8), Square(File.F, Rank.R8))
+      case (Color.Black, CastleSide.Queenside) =>
+        (Square(File.E, Rank.R8), Square(File.C, Rank.R8),
+         Square(File.A, Rank.R8), Square(File.D, Rank.R8))
+    val king = Piece(color, PieceType.King)
+    val rook = Piece(color, PieceType.Rook)
+    Board(b.pieces.removed(kingFrom).removed(rookFrom)
+                  .updated(kingTo, king).updated(rookTo, rook))

modules/core/src/main/scala/de/nowchess/chess/logic/GameHistory.scala

@@ -1,31 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.Square
-import de.nowchess.api.move.PromotionPiece
-
-/** A single move recorded in the game history. Distinct from api.move.Move which represents user intent. */
-case class HistoryMove(
-  from: Square,
-  to: Square,
-  castleSide: Option[CastleSide],
-  promotionPiece: Option[PromotionPiece] = None
-)
-
-/** Complete game history: ordered list of moves. */
-case class GameHistory(moves: List[HistoryMove] = List.empty):
-  def addMove(move: HistoryMove): GameHistory =
-    GameHistory(moves :+ move)
-
-  def addMove(from: Square, to: Square): GameHistory =
-    addMove(HistoryMove(from, to, None))
-
-  def addMove(
-    from: Square,
-    to: Square,
-    castleSide: Option[CastleSide] = None,
-    promotionPiece: Option[PromotionPiece] = None
-  ): GameHistory =
-    addMove(HistoryMove(from, to, castleSide, promotionPiece))
-
-object GameHistory:
-  val empty: GameHistory = GameHistory()

modules/core/src/main/scala/de/nowchess/chess/logic/GameRules.scala

@@ -1,7 +1,7 @@
 package de.nowchess.chess.logic
 
 import de.nowchess.api.board.*
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.chess.logic.GameContext
 
 enum PositionStatus:
   case Normal, InCheck, Mated, Drawn
@@ -20,17 +20,17 @@ object GameRules:
       }
 
   /** All (from, to) moves for `color` that do not leave their own king in check. */
-  def legalMoves(board: Board, history: GameHistory, color: Color): Set[(Square, Square)] =
-    board.pieces
+  def legalMoves(ctx: GameContext, color: Color): Set[(Square, Square)] =
+    ctx.board.pieces
       .collect { case (from, piece) if piece.color == color => from }
       .flatMap { from =>
-        MoveValidator.legalTargets(board, history, from)           // context-aware: includes castling
+        MoveValidator.legalTargets(ctx, from)           // context-aware: includes castling
           .filter { to =>
             val newBoard =
-              if MoveValidator.isCastle(board, from, to) then
-                board.withCastle(color, MoveValidator.castleSide(from, to))
+              if MoveValidator.isCastle(ctx.board, from, to) then
+                ctx.board.withCastle(color, MoveValidator.castleSide(from, to))
               else
-                board.withMove(from, to)._1
+                ctx.board.withMove(from, to)._1
             !isInCheck(newBoard, color)
           }
           .map(to => from -> to)
@@ -38,9 +38,9 @@ object GameRules:
       .toSet
 
   /** Position status for the side whose turn it is (`color`). */
-  def gameStatus(board: Board, history: GameHistory, color: Color): PositionStatus =
-    val moves   = legalMoves(board, history, color)
-    val inCheck = isInCheck(board, color)
+  def gameStatus(ctx: GameContext, color: Color): PositionStatus =
+    val moves   = legalMoves(ctx, color)
+    val inCheck = isInCheck(ctx.board, color)
     if moves.isEmpty && inCheck then PositionStatus.Mated
     else if moves.isEmpty       then PositionStatus.Drawn
     else if inCheck             then PositionStatus.InCheck

modules/core/src/main/scala/de/nowchess/chess/logic/MoveValidator.scala

@@ -1,7 +1,7 @@
 package de.nowchess.chess.logic
 
 import de.nowchess.api.board.*
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
+import de.nowchess.chess.logic.{GameContext, CastleSide}
 
 object MoveValidator:
 
@@ -126,58 +126,42 @@ object MoveValidator:
   def castleSide(from: Square, to: Square): CastleSide =
     if to.file.ordinal > from.file.ordinal then CastleSide.Kingside else CastleSide.Queenside
 
-  def castlingTargets(board: Board, history: GameHistory, color: Color): Set[Square] =
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, color)
+  def castlingTargets(ctx: GameContext, color: Color): Set[Square] =
+    val rights = ctx.castlingFor(color)
     val rank   = if color == Color.White then Rank.R1 else Rank.R8
     val kingSq = Square(File.E, rank)
     val enemy  = color.opposite
 
-    if !board.pieceAt(kingSq).contains(Piece(color, PieceType.King)) ||
-       GameRules.isInCheck(board, color) then Set.empty
-    else
-      val kingsideSq = Option.when(
-        rights.kingSide &&
-        board.pieceAt(Square(File.H, rank)).contains(Piece(color, PieceType.Rook)) &&
-        List(Square(File.F, rank), Square(File.G, rank)).forall(s => board.pieceAt(s).isEmpty) &&
-        !List(Square(File.F, rank), Square(File.G, rank)).exists(s => isAttackedBy(board, s, enemy))
-      )(Square(File.G, rank))
+    if ctx.board.pieceAt(kingSq) != Some(Piece(color, PieceType.King)) then return Set.empty
+    if GameRules.isInCheck(ctx.board, color) then return Set.empty
 
-      val queensideSq = Option.when(
-        rights.queenSide &&
-        board.pieceAt(Square(File.A, rank)).contains(Piece(color, PieceType.Rook)) &&
-        List(Square(File.B, rank), Square(File.C, rank), Square(File.D, rank)).forall(s => board.pieceAt(s).isEmpty) &&
-        !List(Square(File.D, rank), Square(File.C, rank)).exists(s => isAttackedBy(board, s, enemy))
-      )(Square(File.C, rank))
+    var result = Set.empty[Square]
 
-      kingsideSq.toSet ++ queensideSq.toSet
+    if rights.kingSide then
+      val rookSq  = Square(File.H, rank)
+      val transit = List(Square(File.F, rank), Square(File.G, rank))
+      if ctx.board.pieceAt(rookSq).contains(Piece(color, PieceType.Rook)) &&
+         transit.forall(s => ctx.board.pieceAt(s).isEmpty) &&
+         !transit.exists(s => isAttackedBy(ctx.board, s, enemy)) then
+        result += Square(File.G, rank)
 
-  def legalTargets(board: Board, history: GameHistory, from: Square): Set[Square] =
-    board.pieceAt(from) match
+    if rights.queenSide then
+      val rookSq       = Square(File.A, rank)
+      val emptySquares = List(Square(File.B, rank), Square(File.C, rank), Square(File.D, rank))
+      val transitSqs   = List(Square(File.D, rank), Square(File.C, rank))
+      if ctx.board.pieceAt(rookSq).contains(Piece(color, PieceType.Rook)) &&
+         emptySquares.forall(s => ctx.board.pieceAt(s).isEmpty) &&
+         !transitSqs.exists(s => isAttackedBy(ctx.board, s, enemy)) then
+        result += Square(File.C, rank)
+
+    result
+
+  def legalTargets(ctx: GameContext, from: Square): Set[Square] =
+    ctx.board.pieceAt(from) match
       case Some(piece) if piece.pieceType == PieceType.King =>
-        legalTargets(board, from) ++ castlingTargets(board, history, piece.color)
-      case Some(piece) if piece.pieceType == PieceType.Pawn =>
-        pawnTargets(board, history, from, piece.color)
+        legalTargets(ctx.board, from) ++ castlingTargets(ctx, piece.color)
       case _ =>
-        legalTargets(board, from)
+        legalTargets(ctx.board, from)
 
-  private def pawnTargets(board: Board, history: GameHistory, from: Square, color: Color): Set[Square] =
-    val existing = pawnTargets(board, from, color)
-    val fi  = from.file.ordinal
-    val ri  = from.rank.ordinal
-    val dir = if color == Color.White then 1 else -1
-    val epCapture: Set[Square] =
-      EnPassantCalculator.enPassantTarget(board, history).filter: target =>
-        squareAt(fi - 1, ri + dir).contains(target) || squareAt(fi + 1, ri + dir).contains(target)
-      .toSet
-    existing ++ epCapture
-
-  def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
-    legalTargets(board, history, from).contains(to)
-
-  /** Returns true if the piece on `from` is a pawn moving to its back rank (promotion). */
-  def isPromotionMove(board: Board, from: Square, to: Square): Boolean =
-    board.pieceAt(from) match
-      case Some(Piece(_, PieceType.Pawn)) =>
-        (from.rank == Rank.R7 && to.rank == Rank.R8) ||
-        (from.rank == Rank.R2 && to.rank == Rank.R1)
-      case _ => false
+  def isLegal(ctx: GameContext, from: Square, to: Square): Boolean =
+    legalTargets(ctx, from).contains(to)

modules/core/src/main/scala/de/nowchess/chess/notation/FenExporter.scala

@@ -1,60 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.{CastlingRights, GameState}
-import de.nowchess.api.board.Color
-
-object FenExporter:
-
-  /** Convert a Board to FEN piece-placement string (rank 8 to rank 1, separated by '/'). */
-  def boardToFen(board: Board): String =
-    Rank.values.reverse
-      .map(rank => buildRankString(board, rank))
-      .mkString("/")
-
-  /** Build the FEN representation for a single rank. */
-  private def buildRankString(board: Board, rank: Rank): String =
-    val rankSquares = File.values.map(file => Square(file, rank))
-    val rankChars = scala.collection.mutable.ListBuffer[Char]()
-    var emptyCount = 0
-
-    for square <- rankSquares do
-      board.pieceAt(square) match
-        case Some(piece) =>
-          if emptyCount > 0 then
-            rankChars += emptyCount.toString.charAt(0)
-            emptyCount = 0
-          rankChars += pieceToPgnChar(piece)
-        case None =>
-          emptyCount += 1
-
-    if emptyCount > 0 then rankChars += emptyCount.toString.charAt(0)
-    rankChars.mkString
-
-  /** Convert a GameState to a complete FEN string. */
-  def gameStateToFen(state: GameState): String =
-    val piecePlacement = state.piecePlacement
-    val activeColor = if state.activeColor == Color.White then "w" else "b"
-    val castling = castlingString(state.castlingWhite, state.castlingBlack)
-    val enPassant = state.enPassantTarget.map(_.toString).getOrElse("-")
-    s"$piecePlacement $activeColor $castling $enPassant ${state.halfMoveClock} ${state.fullMoveNumber}"
-
-  /** Convert castling rights to FEN notation. */
-  private def castlingString(white: CastlingRights, black: CastlingRights): String =
-    val wk = if white.kingSide then "K" else ""
-    val wq = if white.queenSide then "Q" else ""
-    val bk = if black.kingSide then "k" else ""
-    val bq = if black.queenSide then "q" else ""
-    val result = s"$wk$wq$bk$bq"
-    if result.isEmpty then "-" else result
-
-  /** Convert a Piece to its FEN character (uppercase = White, lowercase = Black). */
-  private def pieceToPgnChar(piece: Piece): Char =
-    val base = piece.pieceType match
-      case PieceType.Pawn   => 'p'
-      case PieceType.Knight => 'n'
-      case PieceType.Bishop => 'b'
-      case PieceType.Rook   => 'r'
-      case PieceType.Queen  => 'q'
-      case PieceType.King   => 'k'
-    if piece.color == Color.White then base.toUpper else base

modules/core/src/main/scala/de/nowchess/chess/notation/FenParser.scala

@@ -1,103 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.{CastlingRights, GameState, GameStatus}
-
-object FenParser:
-
-  /** Parse a complete FEN string into a GameState.
-   *  Returns None if the format is invalid. */
-  def parseFen(fen: String): Option[GameState] =
-    val parts = fen.trim.split("\\s+")
-    Option.when(parts.length == 6)(parts).flatMap: parts =>
-      for
-        _ <- parseBoard(parts(0))
-        activeColor <- parseColor(parts(1))
-        castlingRights <- parseCastling(parts(2))
-        enPassant <- parseEnPassant(parts(3))
-        halfMoveClock <- parts(4).toIntOption
-        fullMoveNumber <- parts(5).toIntOption
-        if halfMoveClock >= 0 && fullMoveNumber >= 1
-      yield GameState(
-        piecePlacement = parts(0),
-        activeColor = activeColor,
-        castlingWhite = castlingRights._1,
-        castlingBlack = castlingRights._2,
-        enPassantTarget = enPassant,
-        halfMoveClock = halfMoveClock,
-        fullMoveNumber = fullMoveNumber,
-        status = GameStatus.InProgress
-      )
-
-  /** Parse active color ("w" or "b"). */
-  private def parseColor(s: String): Option[Color] =
-    if s == "w" then Some(Color.White)
-    else if s == "b" then Some(Color.Black)
-    else None
-
-  /** Parse castling rights string (e.g. "KQkq", "K", "-") into rights for White and Black. */
-  private def parseCastling(s: String): Option[(CastlingRights, CastlingRights)] =
-    if s == "-" then
-      Some((CastlingRights.None, CastlingRights.None))
-    else if s.length <= 4 && s.forall(c => "KQkq".contains(c)) then
-      val white = CastlingRights(kingSide = s.contains('K'), queenSide = s.contains('Q'))
-      val black = CastlingRights(kingSide = s.contains('k'), queenSide = s.contains('q'))
-      Some((white, black))
-    else
-      None
-
-  /** Parse en passant target square ("-" for none, or algebraic like "e3"). */
-  private def parseEnPassant(s: String): Option[Option[Square]] =
-    if s == "-" then Some(None)
-    else Square.fromAlgebraic(s).map(Some(_))
-
-  /** Parses a FEN piece-placement string (rank 8 to rank 1, separated by '/') into a Board.
-   *  Returns None if the format is invalid. */
-  def parseBoard(fen: String): Option[Board] =
-    val rankStrings = fen.split("/", -1)
-    if rankStrings.length != 8 then None
-    else
-      // Parse each rank, collecting all (Square, Piece) pairs or failing on the first error
-      val parsedRanks: Option[List[List[(Square, Piece)]]] =
-        rankStrings.zipWithIndex.foldLeft(Option(List.empty[List[(Square, Piece)]])):
-          case (None, _) => None
-          case (Some(acc), (rankStr, rankIdx)) =>
-            val rank = Rank.values(7 - rankIdx) // ranks go 8→1, so reverse
-            parsePieceRank(rankStr, rank).map(squares => acc :+ squares)
-      parsedRanks.map(ranks => Board(ranks.flatten.toMap))
-
-  /** Parse a single rank string (e.g. "rnbqkbnr" or "p3p3") into a list of (Square, Piece) pairs.
-   *  Returns None if the rank string contains invalid characters or the wrong number of files. */
-  private def parsePieceRank(rankStr: String, rank: Rank): Option[List[(Square, Piece)]] =
-    var fileIdx = 0
-    val squares = scala.collection.mutable.ListBuffer[(Square, Piece)]()
-    var failed = false
-
-    for c <- rankStr if !failed do
-      if fileIdx > 7 then
-        failed = true
-      else if c.isDigit then
-        fileIdx += c.asDigit
-      else
-        charToPiece(c) match
-          case None => failed = true
-          case Some(piece) =>
-            val file = File.values(fileIdx)
-            squares += (Square(file, rank) -> piece)
-            fileIdx += 1
-
-    if failed || fileIdx != 8 then None
-    else Some(squares.toList)
-
-  /** Convert a FEN piece character to a Piece. Uppercase = White, lowercase = Black. */
-  private def charToPiece(c: Char): Option[Piece] =
-    val color = if Character.isUpperCase(c) then Color.White else Color.Black
-    val pieceTypeOpt = c.toLower match
-      case 'p' => Some(PieceType.Pawn)
-      case 'n' => Some(PieceType.Knight)
-      case 'b' => Some(PieceType.Bishop)
-      case 'r' => Some(PieceType.Rook)
-      case 'q' => Some(PieceType.Queen)
-      case 'k' => Some(PieceType.King)
-      case _   => None
-    pieceTypeOpt.map(pt => Piece(color, pt))

modules/core/src/main/scala/de/nowchess/chess/notation/PgnExporter.scala

@@ -1,43 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove}
-
-object PgnExporter:
-
-  /** Export a game with headers and history to PGN format. */
-  def exportGame(headers: Map[String, String], history: GameHistory): String =
-    val headerLines = headers.map { case (key, value) =>
-      s"""[$key "$value"]"""
-    }.mkString("\n")
-
-    val moveText = if history.moves.isEmpty then ""
-    else
-      val groupedMoves = history.moves.zipWithIndex.groupBy(_._2 / 2)
-      val moveLines = for (moveNumber, movePairs) <- groupedMoves.toList.sortBy(_._1) yield
-        val moveNum = moveNumber + 1
-        val whiteMoveStr = movePairs.find(_._2 % 2 == 0).map(p => moveToAlgebraic(p._1)).getOrElse("")
-        val blackMoveStr = movePairs.find(_._2 % 2 == 1).map(p => moveToAlgebraic(p._1)).getOrElse("")
-        if blackMoveStr.isEmpty then s"$moveNum. $whiteMoveStr"
-        else s"$moveNum. $whiteMoveStr $blackMoveStr"
-
-      moveLines.mkString(" ") + " *"
-
-    if headerLines.isEmpty then moveText
-    else if moveText.isEmpty then headerLines
-    else s"$headerLines\n\n$moveText"
-
-  /** Convert a HistoryMove to algebraic notation. */
-  private def moveToAlgebraic(move: HistoryMove): String =
-    move.castleSide match
-      case Some(CastleSide.Kingside)  => "O-O"
-      case Some(CastleSide.Queenside) => "O-O-O"
-      case None =>
-        val base = s"${move.from}${move.to}"
-        move.promotionPiece match
-          case Some(PromotionPiece.Queen)  => s"$base=Q"
-          case Some(PromotionPiece.Rook)   => s"$base=R"
-          case Some(PromotionPiece.Bishop) => s"$base=B"
-          case Some(PromotionPiece.Knight) => s"$base=N"
-          case None                        => base

modules/core/src/main/scala/de/nowchess/chess/notation/PgnParser.scala

@@ -1,175 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory, HistoryMove, GameRules, MoveValidator, withCastle}
-
-/** A parsed PGN game containing headers and the resolved move list. */
-case class PgnGame(
-  headers: Map[String, String],
-  moves: List[HistoryMove]
-)
-
-object PgnParser:
-
-  /** Parse a complete PGN text into a PgnGame with headers and moves.
-   *  Always succeeds (returns Some); malformed tokens are silently skipped. */
-  def parsePgn(pgn: String): Option[PgnGame] =
-    val lines = pgn.split("\n").map(_.trim)
-    val (headerLines, rest) = lines.span(_.startsWith("["))
-
-    val headers  = parseHeaders(headerLines)
-    val moveText = rest.mkString(" ")
-    val moves    = parseMovesText(moveText)
-
-    Some(PgnGame(headers, moves))
-
-  /** Parse PGN header lines of the form [Key "Value"]. */
-  private def parseHeaders(lines: Array[String]): Map[String, String] =
-    val pattern = """^\[(\w+)\s+"([^"]*)"\s*\]$""".r
-    lines.flatMap(line => pattern.findFirstMatchIn(line).map(m => m.group(1) -> m.group(2))).toMap
-
-  /** Parse the move-text section (e.g. "1. e4 e5 2. Nf3") into resolved HistoryMoves. */
-  private def parseMovesText(moveText: String): List[HistoryMove] =
-    val tokens = moveText.split("\\s+").filter(_.nonEmpty)
-
-    // Fold over tokens, threading (board, history, currentColor, accumulator)
-    val (_, _, _, moves) = tokens.foldLeft(
-      (Board.initial, GameHistory.empty, Color.White, List.empty[HistoryMove])
-    ):
-      case (state @ (board, history, color, acc), token) =>
-        // Skip move-number markers (e.g. "1.", "2.") and result tokens
-        if isMoveNumberOrResult(token) then state
-        else
-          parseAlgebraicMove(token, board, history, color) match
-            case None       => state  // unrecognised token — skip silently
-            case Some(move) =>
-              val newBoard   = applyMoveToBoard(board, move, color)
-              val newHistory = history.addMove(move)
-              (newBoard, newHistory, color.opposite, acc :+ move)
-
-    moves
-
-  /** Apply a single HistoryMove to a Board, handling castling and promotion. */
-  private def applyMoveToBoard(board: Board, move: HistoryMove, color: Color): Board =
-    move.castleSide match
-      case Some(side) => board.withCastle(color, side)
-      case None =>
-        val (boardAfterMove, _) = board.withMove(move.from, move.to)
-        move.promotionPiece match
-          case Some(pp) =>
-            val pieceType = pp match
-              case PromotionPiece.Queen  => PieceType.Queen
-              case PromotionPiece.Rook   => PieceType.Rook
-              case PromotionPiece.Bishop => PieceType.Bishop
-              case PromotionPiece.Knight => PieceType.Knight
-            boardAfterMove.updated(move.to, Piece(color, pieceType))
-          case None => boardAfterMove
-
-  /** True for move-number tokens ("1.", "12.") and PGN result tokens. */
-  private def isMoveNumberOrResult(token: String): Boolean =
-    token.matches("""\d+\.""") ||
-    token == "*"               ||
-    token == "1-0"             ||
-    token == "0-1"             ||
-    token == "1/2-1/2"
-
-  /** Parse a single algebraic notation token into a HistoryMove, given the current board state. */
-  def parseAlgebraicMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    notation match
-      case "O-O" | "O-O+" | "O-O#" =>
-        val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.G, rank), Some(CastleSide.Kingside)))
-
-      case "O-O-O" | "O-O-O+" | "O-O-O#" =>
-        val rank = if color == Color.White then Rank.R1 else Rank.R8
-        Some(HistoryMove(Square(File.E, rank), Square(File.C, rank), Some(CastleSide.Queenside)))
-
-      case _ =>
-        parseRegularMove(notation, board, history, color)
-
-  /** Parse regular algebraic notation (pawn moves, piece moves, captures, disambiguation). */
-  private def parseRegularMove(notation: String, board: Board, history: GameHistory, color: Color): Option[HistoryMove] =
-    // Strip check/mate/capture indicators and promotion suffix (e.g. =Q)
-    val clean = notation
-      .replace("+", "")
-      .replace("#", "")
-      .replace("x", "")
-      .replaceAll("=[NBRQ]$", "")
-
-    // The destination square is always the last two characters
-    if clean.length < 2 then None
-    else
-      val destStr = clean.takeRight(2)
-      Square.fromAlgebraic(destStr).flatMap: toSquare =>
-        val disambig = clean.dropRight(2) // "" | "N"|"B"|"R"|"Q"|"K" | file | rank | file+rank
-
-        // Determine required piece type: upper-case first char = piece letter; else pawn
-        val requiredPieceType: Option[PieceType] =
-          if disambig.nonEmpty && disambig.head.isUpper then charToPieceType(disambig.head)
-          else if clean.head.isUpper then charToPieceType(clean.head)
-          else Some(PieceType.Pawn)
-
-        // Collect the disambiguation hint that remains after stripping the piece letter
-        val hint =
-          if disambig.nonEmpty && disambig.head.isUpper then disambig.tail
-          else disambig  // hint is file/rank info or empty
-
-        // Candidate source squares: pieces of `color` that can geometrically reach `toSquare`.
-        // We prefer pieces that can actually reach the target; if none can (positionally illegal
-        // PGN input), fall back to any piece of the matching type belonging to `color`.
-        val reachable: Set[Square] =
-          board.pieces.collect {
-            case (from, piece) if piece.color == color &&
-              MoveValidator.legalTargets(board, from).contains(toSquare) => from
-          }.toSet
-
-        val candidates: Set[Square] =
-          if reachable.nonEmpty then reachable
-          else
-            // Fallback for positionally-illegal but syntactically valid PGN notation:
-            // find any piece of `color` with the correct piece type on the board.
-            board.pieces.collect {
-              case (from, piece) if piece.color == color => from
-            }.toSet
-
-        // Filter by required piece type
-        val byPiece = candidates.filter(from =>
-          requiredPieceType.forall(pt => board.pieceAt(from).exists(_.pieceType == pt))
-        )
-
-        // Apply disambiguation hint (file letter or rank digit)
-        val disambiguated =
-          if hint.isEmpty then byPiece
-          else byPiece.filter(from => matchesHint(from, hint))
-
-        val promotion = extractPromotion(notation)
-        disambiguated.headOption.map(from => HistoryMove(from, toSquare, None, promotion))
-
-  /** True if `sq` matches a disambiguation hint (file letter, rank digit, or both). */
-  private def matchesHint(sq: Square, hint: String): Boolean =
-    hint.forall(c => if c >= 'a' && c <= 'h' then sq.file.toString.equalsIgnoreCase(c.toString)
-    else if c >= '1' && c <= '8' then sq.rank.ordinal == (c - '1')
-    else true)
-
-  /** Extract a promotion piece from a notation string containing =Q/=R/=B/=N. */
-  private[notation] def extractPromotion(notation: String): Option[PromotionPiece] =
-    val promotionPattern = """=([A-Z])""".r
-    promotionPattern.findFirstMatchIn(notation).flatMap { m =>
-      m.group(1) match
-        case "Q" => Some(PromotionPiece.Queen)
-        case "R" => Some(PromotionPiece.Rook)
-        case "B" => Some(PromotionPiece.Bishop)
-        case "N" => Some(PromotionPiece.Knight)
-        case _   => None
-    }
-
-  /** Convert a piece-letter character to a PieceType. */
-  private def charToPieceType(c: Char): Option[PieceType] =
-    c match
-      case 'N' => Some(PieceType.Knight)
-      case 'B' => Some(PieceType.Bishop)
-      case 'R' => Some(PieceType.Rook)
-      case 'Q' => Some(PieceType.Queen)
-      case 'K' => Some(PieceType.King)
-      case _   => None

modules/core/src/main/scala/de/nowchess/chess/observer/Observer.scala

@@ -1,96 +0,0 @@
-package de.nowchess.chess.observer
-
-import de.nowchess.api.board.{Board, Color, Square}
-import de.nowchess.chess.logic.GameHistory
-
-/** Base trait for all game state events.
- *  Events are immutable snapshots of game state changes.
- */
-sealed trait GameEvent:
-  def board: Board
-  def history: GameHistory
-  def turn: Color
-
-/** Fired when a move is successfully executed. */
-case class MoveExecutedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  fromSquare: String,
-  toSquare: String,
-  capturedPiece: Option[String]
-) extends GameEvent
-
-/** Fired when the current player is in check. */
-case class CheckDetectedEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
-) extends GameEvent
-
-/** Fired when the game reaches checkmate. */
-case class CheckmateEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  winner: Color
-) extends GameEvent
-
-/** Fired when the game reaches stalemate. */
-case class StalemateEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
-) extends GameEvent
-
-/** Fired when a move is invalid. */
-case class InvalidMoveEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  reason: String
-) extends GameEvent
-
-/** Fired when a pawn reaches the back rank and the player must choose a promotion piece. */
-case class PromotionRequiredEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color,
-  from: Square,
-  to: Square
-) extends GameEvent
-
-/** Fired when the board is reset. */
-case class BoardResetEvent(
-  board: Board,
-  history: GameHistory,
-  turn: Color
-) extends GameEvent
-
-/** Observer trait: implement to receive game state updates. */
-trait Observer:
-  def onGameEvent(event: GameEvent): Unit
-
-/** Observable trait: manages observers and notifies them of events. */
-trait Observable:
-  private val observers = scala.collection.mutable.Set[Observer]()
-
-  /** Register an observer to receive game events. */
-  def subscribe(observer: Observer): Unit = synchronized {
-    observers += observer
-  }
-
-  /** Unregister an observer. */
-  def unsubscribe(observer: Observer): Unit = synchronized {
-    observers -= observer
-  }
-
-  /** Notify all observers of a game event. */
-  protected def notifyObservers(event: GameEvent): Unit = synchronized {
-    observers.foreach(_.onGameEvent(event))
-  }
-
-  /** Return current list of observers (for testing). */
-  def observerCount: Int = synchronized {
-    observers.size
-  }

modules/core/src/main/scala/de/nowchess/chess/view/Renderer.scala

@@ -11,18 +11,21 @@ object Renderer:
   private val AnsiBlackPiece  = "\u001b[30m"         // black text
 
   def render(board: Board): String =
-    val rows = (0 until 8).reverse.map { rank =>
-      val cells = (0 until 8).map { file =>
-        val sq        = Square(File.values(file), Rank.values(rank))
-        val isLightSq = (file + rank) % 2 != 0
-        val bgColor   = if isLightSq then AnsiLightSquare else AnsiDarkSquare
-        board.pieceAt(sq) match
+    val sb = new StringBuilder
+    sb.append("  a  b  c  d  e  f  g  h\n")
+    for rank <- (0 until 8).reverse do
+      sb.append(s"${rank + 1} ")
+      for file <- 0 until 8 do
+        val sq          = Square(File.values(file), Rank.values(rank))
+        val isLightSq   = (file + rank) % 2 != 0
+        val bgColor     = if isLightSq then AnsiLightSquare else AnsiDarkSquare
+        val cellContent = board.pieceAt(sq) match
           case Some(piece) =>
             val fgColor = if piece.color == Color.White then AnsiWhitePiece else AnsiBlackPiece
             s"$bgColor$fgColor ${piece.unicode} $AnsiReset"
           case None =>
             s"$bgColor   $AnsiReset"
-      }.mkString
-      s"${rank + 1} $cells ${rank + 1}"
-    }.mkString("\n")
-    s"  a  b  c  d  e  f  g  h\n$rows\n  a  b  c  d  e  f  g  h\n"
+        sb.append(cellContent)
+      sb.append(s" ${rank + 1}\n")
+    sb.append("  a  b  c  d  e  f  g  h\n")
+    sb.toString

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerBranchTest.scala

@@ -1,216 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CommandInvokerBranchTest extends AnyFunSuite with Matchers:
-  
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  // ──── Helper: Command that always fails ────
-  private case class FailingCommand() extends Command:
-    override def execute(): Boolean = false
-    override def undo(): Boolean = false
-    override def description: String = "Failing command"
-
-  // ──── Helper: Command that conditionally fails on undo or execute ────
-  private case class ConditionalFailCommand(var shouldFailOnUndo: Boolean = false, var shouldFailOnExecute: Boolean = false) extends Command:
-    override def execute(): Boolean = !shouldFailOnExecute
-    override def undo(): Boolean = !shouldFailOnUndo
-    override def description: String = "Conditional fail"
-
-  private def createMoveCommand(from: Square, to: Square, executeSucceeds: Boolean = true): MoveCommand =
-    val cmd = MoveCommand(
-      from = from,
-      to = to,
-      moveResult = if executeSucceeds then Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)) else None,
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd
-
-  // ──── BRANCH: execute() returns false ────
-  test("CommandInvoker.execute() with failing command returns false"):
-    val invoker = new CommandInvoker()
-    val cmd = FailingCommand()
-    invoker.execute(cmd) shouldBe false
-    invoker.history.size shouldBe 0
-    invoker.getCurrentIndex shouldBe -1
-
-  test("CommandInvoker.execute() does not add failed command to history"):
-    val invoker = new CommandInvoker()
-    val failingCmd = FailingCommand()
-    val successCmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
-    invoker.execute(failingCmd) shouldBe false
-    invoker.history.size shouldBe 0
-    
-    invoker.execute(successCmd) shouldBe true
-    invoker.history.size shouldBe 1
-    invoker.history(0) shouldBe successCmd
-
-  // ──── BRANCH: undo() with invalid index (currentIndex < 0) ────
-  test("CommandInvoker.undo() returns false when currentIndex < 0"):
-    val invoker = new CommandInvoker()
-    // currentIndex starts at -1
-    invoker.undo() shouldBe false
-
-  test("CommandInvoker.undo() returns false when empty history"):
-    val invoker = new CommandInvoker()
-    invoker.canUndo shouldBe false
-    invoker.undo() shouldBe false
-
-  // ──── BRANCH: undo() with invalid index (currentIndex >= size) ────
-  test("CommandInvoker.undo() returns false when currentIndex >= history size"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex now = 1, history.size = 2
-    
-    invoker.undo()  // currentIndex becomes 0
-    invoker.undo()  // currentIndex becomes -1
-    invoker.undo()  // currentIndex still -1, should fail
-
-  // ──── BRANCH: undo() command returns false ────
-  test("CommandInvoker.undo() returns false when command.undo() fails"):
-    val invoker = new CommandInvoker()
-    val failingCmd = ConditionalFailCommand(shouldFailOnUndo = true)
-    
-    invoker.execute(failingCmd) shouldBe true
-    invoker.canUndo shouldBe true
-    
-    invoker.undo() shouldBe false
-    // Index should not change when undo fails
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker.undo() returns true when command.undo() succeeds"):
-    val invoker = new CommandInvoker()
-    val successCmd = ConditionalFailCommand(shouldFailOnUndo = false)
-    
-    invoker.execute(successCmd) shouldBe true
-    invoker.undo() shouldBe true
-    invoker.getCurrentIndex shouldBe -1
-
-  // ──── BRANCH: redo() with invalid index (currentIndex + 1 >= size) ────
-  test("CommandInvoker.redo() returns false when nothing to redo"):
-    val invoker = new CommandInvoker()
-    invoker.redo() shouldBe false
-
-  test("CommandInvoker.redo() returns false when at end of history"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
-    invoker.execute(cmd)
-    // currentIndex = 0, history.size = 1
-    invoker.canRedo shouldBe false
-    invoker.redo() shouldBe false
-
-  test("CommandInvoker.redo() returns false when currentIndex + 1 >= size"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2, currentIndex + 1 = 2, so 2 < 2 is false
-    invoker.canRedo shouldBe false
-    invoker.redo() shouldBe false
-
-  // ──── BRANCH: redo() command returns false ────
-  test("CommandInvoker.redo() returns false when command.execute() fails"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val redoFailCmd = ConditionalFailCommand(shouldFailOnExecute = false)  // Succeeds on first execute
-    
-    invoker.execute(cmd1)
-    invoker.execute(redoFailCmd)  // Succeeds and added to history
-    
-    invoker.undo()
-    // currentIndex = 0, redoFailCmd is at index 1
-    invoker.canRedo shouldBe true
-    
-    // Now modify to fail on next execute (redo)
-    redoFailCmd.shouldFailOnExecute = true
-    invoker.redo() shouldBe false
-    // currentIndex should not change
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker.redo() returns true when command.execute() succeeds"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    
-    invoker.execute(cmd) shouldBe true
-    invoker.undo() shouldBe true
-    invoker.redo() shouldBe true
-    invoker.getCurrentIndex shouldBe 0
-
-  // ──── BRANCH: execute() with redo history discarding (while loop) ────
-  test("CommandInvoker.execute() discards redo history via while loop"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    
-    invoker.undo()
-    // currentIndex = 0, size = 2
-    // Redo history exists: cmd2 is at index 1
-    invoker.canRedo shouldBe true
-    
-    invoker.execute(cmd3)
-    // while loop should discard cmd2
-    invoker.canRedo shouldBe false
-    invoker.history.size shouldBe 2
-    invoker.history(1) shouldBe cmd3
-
-  test("CommandInvoker.execute() discards multiple redo commands"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.G, Rank.R1), sq(File.F, Rank.R3))
-    val cmd4 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    invoker.execute(cmd3)
-    invoker.execute(cmd4)
-    // currentIndex = 3, size = 4
-    
-    invoker.undo()
-    invoker.undo()
-    // currentIndex = 1, size = 4
-    // Redo history: cmd3 (idx 2), cmd4 (idx 3)
-    invoker.canRedo shouldBe true
-    
-    val newCmd = createMoveCommand(sq(File.B, Rank.R2), sq(File.B, Rank.R4))
-    invoker.execute(newCmd)
-    // While loop should discard indices 2 and 3 (cmd3 and cmd4)
-    invoker.history.size shouldBe 3
-    invoker.canRedo shouldBe false
-
-  // ──── BRANCH: execute() with no redo history to discard ────
-  test("CommandInvoker.execute() with no redo history (while condition false)"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    // currentIndex = 1, size = 2
-    // currentIndex < size - 1 is 1 < 1 which is false, so while loop doesn't run
-    
-    invoker.canRedo shouldBe false
-    
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd3)  // While loop condition should be false, no iterations
-    invoker.history.size shouldBe 3
-

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerTest.scala

@@ -1,123 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CommandInvokerTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  
-  private def createMoveCommand(from: Square, to: Square): MoveCommand =
-    MoveCommand(
-      from = from,
-      to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-
-  test("CommandInvoker executes a command and adds it to history"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd) shouldBe true
-    invoker.history.size shouldBe 1
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker executes multiple commands in sequence"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    invoker.execute(cmd1) shouldBe true
-    invoker.execute(cmd2) shouldBe true
-    invoker.history.size shouldBe 2
-    invoker.getCurrentIndex shouldBe 1
-
-  test("CommandInvoker.canUndo returns false when empty"):
-    val invoker = new CommandInvoker()
-    invoker.canUndo shouldBe false
-
-  test("CommandInvoker.canUndo returns true after execution"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.canUndo shouldBe true
-
-  test("CommandInvoker.undo decrements current index"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.getCurrentIndex shouldBe 0
-    invoker.undo() shouldBe true
-    invoker.getCurrentIndex shouldBe -1
-
-  test("CommandInvoker.canRedo returns true after undo"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo()
-    invoker.canRedo shouldBe true
-
-  test("CommandInvoker.redo re-executes a command"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo() shouldBe true
-    invoker.redo() shouldBe true
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker.canUndo returns false when at beginning"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.undo()
-    invoker.canUndo shouldBe false
-
-  test("CommandInvoker clear removes all history"):
-    val invoker = new CommandInvoker()
-    val cmd = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    invoker.execute(cmd)
-    invoker.clear()
-    invoker.history.size shouldBe 0
-    invoker.getCurrentIndex shouldBe -1
-
-  test("CommandInvoker discards all history when executing after undoing all"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    invoker.undo()
-    invoker.undo()
-    // After undoing twice, we're at the beginning (before any commands)
-    invoker.getCurrentIndex shouldBe -1
-    invoker.canRedo shouldBe true
-    // Executing a new command from the beginning discards all redo history
-    invoker.execute(cmd3)
-    invoker.canRedo shouldBe false
-    invoker.history.size shouldBe 1
-    invoker.history(0) shouldBe cmd3
-    invoker.getCurrentIndex shouldBe 0
-
-  test("CommandInvoker discards redo history when executing mid-history"):
-    val invoker = new CommandInvoker()
-    val cmd1 = createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val cmd2 = createMoveCommand(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    val cmd3 = createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    invoker.execute(cmd1)
-    invoker.execute(cmd2)
-    invoker.undo()
-    // After one undo, we're at the end of cmd1
-    invoker.getCurrentIndex shouldBe 0
-    invoker.canRedo shouldBe true
-    // Executing a new command discards cmd2 (the redo history)
-    invoker.execute(cmd3)
-    invoker.canRedo shouldBe false
-    invoker.history.size shouldBe 2
-    invoker.history(0) shouldBe cmd1
-    invoker.history(1) shouldBe cmd3
-    invoker.getCurrentIndex shouldBe 1
-

modules/core/src/test/scala/de/nowchess/chess/command/CommandInvokerThreadSafetyTest.scala

@@ -1,131 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import scala.collection.mutable
-
-class CommandInvokerThreadSafetyTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  private def createMoveCommand(from: Square, to: Square): MoveCommand =
-    MoveCommand(
-      from = from,
-      to = to,
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-
-  test("CommandInvoker is thread-safe for concurrent execute and history reads"):
-    val invoker = new CommandInvoker()
-    @volatile var raceDetected = false
-    val exceptions = mutable.ListBuffer[Exception]()
-
-    // Thread 1: executes commands
-    val executorThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for i <- 1 to 1000 do
-            val cmd = createMoveCommand(
-              sq(File.E, Rank.R2),
-              sq(File.E, Rank.R4)
-            )
-            invoker.execute(cmd)
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 2: reads history during execution
-    val readerThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 1000 do
-            val _ = invoker.history
-            val _ = invoker.getCurrentIndex
-            Thread.sleep(0) // Yield to increase contention
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    executorThread.start()
-    readerThread.start()
-    executorThread.join()
-    readerThread.join()
-
-    exceptions.isEmpty shouldBe true
-    raceDetected shouldBe false
-
-  test("CommandInvoker is thread-safe for concurrent execute, undo, and redo"):
-    val invoker = new CommandInvoker()
-    @volatile var raceDetected = false
-    val exceptions = mutable.ListBuffer[Exception]()
-
-    // Pre-populate with some commands
-    for _ <- 1 to 5 do
-      invoker.execute(createMoveCommand(sq(File.E, Rank.R2), sq(File.E, Rank.R4)))
-
-    // Thread 1: executes new commands
-    val executorThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            invoker.execute(createMoveCommand(sq(File.D, Rank.R2), sq(File.D, Rank.R4)))
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 2: undoes commands
-    val undoThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            if invoker.canUndo then
-              invoker.undo()
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    // Thread 3: redoes commands
-    val redoThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            if invoker.canRedo then
-              invoker.redo()
-        } catch {
-          case e: Exception =>
-            exceptions += e
-            raceDetected = true
-        }
-      }
-    })
-
-    executorThread.start()
-    undoThread.start()
-    redoThread.start()
-    executorThread.join()
-    undoThread.join()
-    redoThread.join()
-
-    exceptions.isEmpty shouldBe true
-    raceDetected shouldBe false

modules/core/src/test/scala/de/nowchess/chess/command/CommandTest.scala

@@ -1,52 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CommandTest extends AnyFunSuite with Matchers:
-
-  test("QuitCommand can be created"):
-    val cmd = QuitCommand()
-    cmd shouldNot be(null)
-
-  test("QuitCommand execute returns true"):
-    val cmd = QuitCommand()
-    cmd.execute() shouldBe true
-
-  test("QuitCommand undo returns false (cannot undo quit)"):
-    val cmd = QuitCommand()
-    cmd.undo() shouldBe false
-
-  test("QuitCommand description"):
-    val cmd = QuitCommand()
-    cmd.description shouldBe "Quit game"
-
-  test("ResetCommand with no prior state"):
-    val cmd = ResetCommand()
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe false
-
-  test("ResetCommand with prior state can undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe true
-
-  test("ResetCommand with partial state cannot undo"):
-    val cmd = ResetCommand(
-      previousBoard = Some(Board.initial),
-      previousHistory = None,  // missing
-      previousTurn = Some(Color.White)
-    )
-    cmd.execute() shouldBe true
-    cmd.undo() shouldBe false
-
-  test("ResetCommand description"):
-    val cmd = ResetCommand()
-    cmd.description shouldBe "Reset board"
-

modules/core/src/test/scala/de/nowchess/chess/command/MoveCommandImmutabilityTest.scala

@@ -1,65 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveCommandImmutabilityTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("MoveCommand should be immutable - fields cannot be mutated after creation"):
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-
-    // Create second command with filled state
-    val result = MoveResult.Successful(Board.initial, GameHistory.empty, Color.Black, None)
-    val cmd2 = cmd1.copy(
-      moveResult = Some(result),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-
-    // Original should be unchanged
-    cmd1.moveResult shouldBe None
-    cmd1.previousBoard shouldBe None
-    cmd1.previousHistory shouldBe None
-    cmd1.previousTurn shouldBe None
-
-    // New should have values
-    cmd2.moveResult shouldBe Some(result)
-    cmd2.previousBoard shouldBe Some(Board.initial)
-    cmd2.previousHistory shouldBe Some(GameHistory.empty)
-    cmd2.previousTurn shouldBe Some(Color.White)
-
-  test("MoveCommand equals and hashCode respect immutability"):
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
-    )
-
-    val cmd2 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = None,
-      previousBoard = None,
-      previousHistory = None,
-      previousTurn = None
-    )
-
-    // Same values should be equal
-    cmd1 shouldBe cmd2
-    cmd1.hashCode shouldBe cmd2.hashCode
-
-    // Hash should be consistent (required for use as map keys)
-    val hash1 = cmd1.hashCode
-    val hash2 = cmd1.hashCode
-    hash1 shouldBe hash2

modules/core/src/test/scala/de/nowchess/chess/controller/GameControllerTest.scala

@@ -2,489 +2,406 @@ package de.nowchess.chess.controller
 
 import de.nowchess.api.board.*
 import de.nowchess.api.game.CastlingRights
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
+import de.nowchess.chess.logic.{GameContext, CastleSide}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
+import java.io.ByteArrayInputStream
+
 class GameControllerTest extends AnyFunSuite with Matchers:
 
   private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
-    GameController.processMove(board, history, turn, raw)
-
-  private def castlingRights(history: GameHistory, color: Color): CastlingRights =
-    de.nowchess.chess.logic.CastlingRightsCalculator.deriveCastlingRights(history, color)
+  private val initial = GameContext.initial
 
   // ──── processMove ────────────────────────────────────────────────────
 
   test("processMove: 'quit' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "quit") shouldBe MoveResult.Quit
+    GameController.processMove(initial, Color.White, "quit") shouldBe MoveResult.Quit
 
   test("processMove: 'q' input returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "q") shouldBe MoveResult.Quit
+    GameController.processMove(initial, Color.White, "q") shouldBe MoveResult.Quit
 
   test("processMove: quit with surrounding whitespace returns Quit"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "  quit  ") shouldBe MoveResult.Quit
+    GameController.processMove(initial, Color.White, "  quit  ") shouldBe MoveResult.Quit
 
   test("processMove: unparseable input returns InvalidFormat"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
+    GameController.processMove(initial, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
 
   test("processMove: valid format but empty square returns NoPiece"):
     // E3 is empty in the initial position
-    processMove(Board.initial, GameHistory.empty, Color.White, "e3e4") shouldBe MoveResult.NoPiece
+    GameController.processMove(initial, Color.White, "e3e4") shouldBe MoveResult.NoPiece
 
   test("processMove: piece of wrong color returns WrongColor"):
     // E7 has a Black pawn; it is White's turn
-    processMove(Board.initial, GameHistory.empty, Color.White, "e7e6") shouldBe MoveResult.WrongColor
+    GameController.processMove(initial, Color.White, "e7e6") shouldBe MoveResult.WrongColor
 
   test("processMove: geometrically illegal move returns IllegalMove"):
     // White pawn at E2 cannot jump three squares to E5
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that leaves own king in check returns IllegalMove"):
-    // White King E1 is in check from Black Rook E8. Moving the D2 pawn is
-    // geometrically legal but does not resolve the check — must be rejected.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.D, Rank.R2) -> Piece.WhitePawn,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "d2d4") shouldBe MoveResult.IllegalMove
-
-  test("processMove: move that resolves check is allowed"):
-    // White King E1 is in check from Black Rook E8 along the E-file.
-    // White Rook A5 interposes at E5 — resolves the check, no new check on Black King A8.
-    val b = Board(Map(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R5) -> Piece.WhiteRook,
-      sq(File.E, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a5e5") match
-      case _: MoveResult.Moved => succeed
-      case other => fail(s"Expected Moved, got $other")
+    GameController.processMove(initial, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
 
   test("processMove: legal pawn move returns Moved with updated board and flipped turn"):
-    processMove(Board.initial, GameHistory.empty, Color.White, "e2e4") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.E, Rank.R4)) shouldBe Some(Piece.WhitePawn)
-        newBoard.pieceAt(sq(File.E, Rank.R2)) shouldBe None
+    GameController.processMove(initial, Color.White, "e2e4") match
+      case MoveResult.Moved(newCtx, captured, newTurn) =>
+        newCtx.board.pieceAt(sq(File.E, Rank.R4)) shouldBe Some(Piece.WhitePawn)
+        newCtx.board.pieceAt(sq(File.E, Rank.R2)) shouldBe None
         captured shouldBe None
         newTurn shouldBe Color.Black
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: legal capture returns Moved with the captured piece"):
-    val board = Board(Map(
+    val captureCtx = GameContext(Board(Map(
+      sq(File.E, Rank.R5) -> Piece.WhitePawn,
+      sq(File.D, Rank.R6) -> Piece.BlackPawn,
+      sq(File.H, Rank.R1) -> Piece.BlackKing,
+      sq(File.H, Rank.R8) -> Piece.WhiteKing
+    )))
+    GameController.processMove(captureCtx, Color.White, "e5d6") match
+      case MoveResult.Moved(newCtx, captured, newTurn) =>
+        captured shouldBe Some(Piece.BlackPawn)
+        newCtx.board.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
+        newTurn shouldBe Color.Black
+      case other => fail(s"Expected Moved, got $other")
+
+  // ──── gameLoop ───────────────────────────────────────────────────────
+
+  private def withInput(input: String)(block: => Unit): Unit =
+    val stream = ByteArrayInputStream(input.getBytes("UTF-8"))
+    scala.Console.withIn(stream)(block)
+
+  test("gameLoop: 'quit' exits cleanly without exception"):
+    withInput("quit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: EOF (null readLine) exits via quit fallback"):
+    withInput(""):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: invalid format prints message and recurses until quit"):
+    withInput("badmove\nquit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: NoPiece prints message and recurses until quit"):
+    // E3 is empty in the initial position
+    withInput("e3e4\nquit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: WrongColor prints message and recurses until quit"):
+    // E7 has a Black pawn; it is White's turn
+    withInput("e7e6\nquit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: IllegalMove prints message and recurses until quit"):
+    withInput("e2e5\nquit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: legal non-capture move recurses with new board then quits"):
+    withInput("e2e4\nquit\n"):
+      GameController.gameLoop(GameContext.initial, Color.White)
+
+  test("gameLoop: capture move prints capture message then recurses and quits"):
+    val captureBoard = Board(Map(
       sq(File.E, Rank.R5) -> Piece.WhitePawn,
       sq(File.D, Rank.R6) -> Piece.BlackPawn,
       sq(File.H, Rank.R1) -> Piece.BlackKing,
       sq(File.H, Rank.R8) -> Piece.WhiteKing
     ))
-    processMove(board, GameHistory.empty, Color.White, "e5d6") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        captured shouldBe Some(Piece.BlackPawn)
-        newBoard.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
-        newTurn shouldBe Color.Black
-      case other => fail(s"Expected Moved, got $other")
+    withInput("e5d6\nquit\n"):
+      GameController.gameLoop(GameContext(captureBoard), Color.White)
+
+  // ──── helpers ────────────────────────────────────────────────────────
+
+  private def captureOutput(block: => Unit): String =
+    val out = java.io.ByteArrayOutputStream()
+    scala.Console.withOut(out)(block)
+    out.toString("UTF-8")
 
   // ──── processMove: check / checkmate / stalemate ─────────────────────
 
   test("processMove: legal move that delivers check returns MovedInCheck"):
     // White Ra1, Ka3; Black Kh8 — White plays Ra1-Ra8, Ra8 attacks rank 8 putting Kh8 in check
     // Kh8 can escape to g7/g8/h7 so this is InCheck, not Mated
-    val b = Board(Map(
+    val ctx = GameContext(Board(Map(
       sq(File.A, Rank.R1) -> Piece.WhiteRook,
       sq(File.C, Rank.R3) -> Piece.WhiteKing,
       sq(File.H, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1a8") match
-      case MoveResult.MovedInCheck(_, _, _, newTurn) => newTurn shouldBe Color.Black
+    )))
+    GameController.processMove(ctx, Color.White, "a1a8") match
+      case MoveResult.MovedInCheck(_, _, newTurn) => newTurn shouldBe Color.Black
       case other => fail(s"Expected MovedInCheck, got $other")
 
   test("processMove: legal move that results in checkmate returns Checkmate"):
     // White Qa1, Ka6; Black Ka8 — White plays Qa1-Qh8 (diagonal a1→h8)
     // After Qh8: White Qh8 + Ka6 vs Black Ka8 = checkmate (spec-verified position)
     // Qa1 does NOT currently attack Ka8 — path along file A is blocked by Ka6
-    val b = Board(Map(
+    val ctx = GameContext(Board(Map(
       sq(File.A, Rank.R1) -> Piece.WhiteQueen,
       sq(File.A, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
-    ))
-    processMove(b, GameHistory.empty, Color.White, "a1h8") match
+    )))
+    GameController.processMove(ctx, Color.White, "a1h8") match
       case MoveResult.Checkmate(winner) => winner shouldBe Color.White
       case other => fail(s"Expected Checkmate(White), got $other")
 
   test("processMove: legal move that results in stalemate returns Stalemate"):
     // White Qb1, Kc6; Black Ka8 — White plays Qb1-Qb6
     // After Qb6: White Qb6 + Kc6 vs Black Ka8 = stalemate (spec-verified position)
+    val ctx = GameContext(Board(Map(
+      sq(File.B, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.C, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    )))
+    GameController.processMove(ctx, Color.White, "b1b6") match
+      case MoveResult.Stalemate => succeed
+      case other => fail(s"Expected Stalemate, got $other")
+
+  // ──── gameLoop: check / checkmate / stalemate ─────────────────────────
+
+  test("gameLoop: checkmate prints winner message and resets to new game"):
+    // After Qa1-Qh8, position is checkmate; second "quit" exits the new game
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteQueen,
+      sq(File.A, Rank.R6) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1h8\nquit\n"):
+        GameController.gameLoop(GameContext(b), Color.White)
+    output should include("Checkmate! White wins.")
+
+  test("gameLoop: stalemate prints draw message and resets to new game"):
     val b = Board(Map(
       sq(File.B, Rank.R1) -> Piece.WhiteQueen,
       sq(File.C, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
     ))
-    processMove(b, GameHistory.empty, Color.White, "b1b6") match
-      case MoveResult.Stalemate => succeed
-      case other => fail(s"Expected Stalemate, got $other")
+    val output = captureOutput:
+      withInput("b1b6\nquit\n"):
+        GameController.gameLoop(GameContext(b), Color.White)
+    output should include("Stalemate! The game is a draw.")
+
+  test("gameLoop: MovedInCheck without capture prints check message"):
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.C, Rank.R3) -> Piece.WhiteKing,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1a8\nquit\n"):
+        GameController.gameLoop(GameContext(b), Color.White)
+    output should include("Black is in check!")
+
+  test("gameLoop: MovedInCheck with capture prints both capture and check message"):
+    // White Rook A1 captures Black Pawn on A8, Ra8 then attacks rank 8 putting Kh8 in check
+    val b = Board(Map(
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.C, Rank.R3) -> Piece.WhiteKing,
+      sq(File.A, Rank.R8) -> Piece.BlackPawn,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    ))
+    val output = captureOutput:
+      withInput("a1a8\nquit\n"):
+        GameController.gameLoop(GameContext(b), Color.White)
+    output should include("captures")
+    output should include("Black is in check!")
 
   // ──── castling execution ─────────────────────────────────────────────
 
   test("processMove: e1g1 returns Moved with king on g1 and rook on f1"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
-        newBoard.pieceAt(sq(File.G, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.F, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-        newBoard.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-        newBoard.pieceAt(sq(File.H, Rank.R1)) shouldBe None
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1g1") match
+      case MoveResult.Moved(newCtx, captured, newTurn) =>
+        newCtx.board.pieceAt(sq(File.G, Rank.R1)) shouldBe Some(Piece.WhiteKing)
+        newCtx.board.pieceAt(sq(File.F, Rank.R1)) shouldBe Some(Piece.WhiteRook)
+        newCtx.board.pieceAt(sq(File.E, Rank.R1)) shouldBe None
+        newCtx.board.pieceAt(sq(File.H, Rank.R1)) shouldBe None
         captured shouldBe None
         newTurn shouldBe Color.Black
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: e1c1 returns Moved with king on c1 and rook on d1"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.A, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1c1") match
-      case MoveResult.Moved(newBoard, _, _, _) =>
-        newBoard.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-        newBoard.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1c1") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.board.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
+        newCtx.board.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
       case other => fail(s"Expected Moved, got $other")
 
   // ──── rights revocation ──────────────────────────────────────────────
 
   test("processMove: e1g1 revokes both white castling rights"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1g1") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.whiteCastling shouldBe CastlingRights.None
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: moving rook from h1 revokes white kingside right"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "h1h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide  shouldBe false
-        castlingRights(newHistory, Color.White).queenSide shouldBe true
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "h1h4") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.whiteCastling.kingSide  shouldBe false
+        newCtx.whiteCastling.queenSide shouldBe true
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.whiteCastling.kingSide  shouldBe false
+        newCtx.whiteCastling.queenSide shouldBe true
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving king from e1 revokes both white rights"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1e2") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1e2") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.whiteCastling shouldBe CastlingRights.None
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: enemy capture on h1 revokes white kingside right"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R2) -> Piece.BlackRook,
         sq(File.A, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h2h1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).kingSide shouldBe false
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.Black, "h2h1") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.whiteCastling.kingSide shouldBe false
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.whiteCastling.kingSide shouldBe false
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: castle attempt when rights revoked returns IllegalMove"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2)).addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R1))
-    processMove(b, history, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
+      )),
+      whiteCastling = CastlingRights.None,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
 
   test("processMove: castle attempt when rook not on home square returns IllegalMove"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.G, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
 
   test("processMove: moving king from e8 revokes both black rights"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "e8e7") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black) shouldBe CastlingRights.None
+      )),
+      whiteCastling = CastlingRights.None,
+      blackCastling = CastlingRights.Both
+    )
+    GameController.processMove(ctx, Color.Black, "e8e7") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.blackCastling shouldBe CastlingRights.None
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.blackCastling shouldBe CastlingRights.None
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving rook from a8 revokes black queenside right"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.A, Rank.R8) -> Piece.BlackRook,
         sq(File.H, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a8a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).queenSide shouldBe false
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe true
+      )),
+      whiteCastling = CastlingRights.None,
+      blackCastling = CastlingRights.Both
+    )
+    GameController.processMove(ctx, Color.Black, "a8a7") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.blackCastling.queenSide shouldBe false
+        newCtx.blackCastling.kingSide  shouldBe true
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.blackCastling.queenSide shouldBe false
+        newCtx.blackCastling.kingSide  shouldBe true
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving rook from h8 revokes black kingside right"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.H, Rank.R8) -> Piece.BlackRook,
-        sq(File.A, Rank.R1) -> Piece.WhiteKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "h8h4") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.Black).kingSide  shouldBe false
-        castlingRights(newHistory, Color.Black).queenSide shouldBe true
+        sq(File.H, Rank.R1) -> Piece.WhiteKing
+      )),
+      whiteCastling = CastlingRights.None,
+      blackCastling = CastlingRights.Both
+    )
+    GameController.processMove(ctx, Color.Black, "h8h7") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.blackCastling.kingSide  shouldBe false
+        newCtx.blackCastling.queenSide shouldBe true
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.blackCastling.kingSide  shouldBe false
+        newCtx.blackCastling.queenSide shouldBe true
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: enemy capture on a1 revokes white queenside right"):
-    val b = Board(Map(
+    val ctx = GameContext(
+      board = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.A, Rank.R1) -> Piece.WhiteRook,
         sq(File.A, Rank.R2) -> Piece.BlackRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ))
-    processMove(b, GameHistory.empty, Color.Black, "a2a1") match
-      case MoveResult.Moved(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
-      case MoveResult.MovedInCheck(_, newHistory, _, _) =>
-        castlingRights(newHistory, Color.White).queenSide shouldBe false
+      )),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameController.processMove(ctx, Color.Black, "a2a1") match
+      case MoveResult.Moved(newCtx, _, _) =>
+        newCtx.whiteCastling.queenSide shouldBe false
+      case MoveResult.MovedInCheck(newCtx, _, _) =>
+        newCtx.whiteCastling.queenSide shouldBe false
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
-
-  // ──── en passant ────────────────────────────────────────────────────────
-
-  test("en passant capture removes the captured pawn from the board"):
-    // Setup: white pawn e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = Board(Map(
-      Square(File.E, Rank.R5) -> Piece.WhitePawn,
-      Square(File.D, Rank.R5) -> Piece.BlackPawn,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing,
-      Square(File.E, Rank.R8) -> Piece.BlackKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.D, Rank.R7), Square(File.D, Rank.R5))
-    val result = GameController.processMove(b, h, Color.White, "e5d6")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.D, Rank.R5)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.BlackPawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  test("en passant capture by black removes the captured white pawn"):
-    // Setup: black pawn d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = Board(Map(
-      Square(File.D, Rank.R4) -> Piece.BlackPawn,
-      Square(File.E, Rank.R4) -> Piece.WhitePawn,
-      Square(File.E, Rank.R8) -> Piece.BlackKing,
-      Square(File.E, Rank.R1) -> Piece.WhiteKing
-    ))
-    val h = GameHistory.empty.addMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4))
-    val result = GameController.processMove(b, h, Color.Black, "d4e3")
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(Square(File.E, Rank.R4)) shouldBe None  // captured pawn removed
-        newBoard.pieceAt(Square(File.E, Rank.R3)) shouldBe Some(Piece.BlackPawn)  // capturing pawn placed
-        captured shouldBe Some(Piece.WhitePawn)
-      case other => fail(s"Expected Moved but got $other")
-
-  // ──── pawn promotion detection ───────────────────────────────────────────
-
-  test("processMove detects white pawn reaching R8 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7e8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R7))
-        to   should be (sq(File.E, Rank.R8))
-        turn should be (Color.White)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects black pawn reaching R1 and returns PromotionRequired"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.Black, "e2e1")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(from, to, _, _, _, turn) =>
-        from should be (sq(File.E, Rank.R2))
-        to   should be (sq(File.E, Rank.R1))
-        turn should be (Color.Black)
-      case _ => fail("Expected PromotionRequired")
-
-  test("processMove detects pawn capturing to back rank as PromotionRequired with captured piece"):
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    val result = GameController.processMove(board, GameHistory.empty, Color.White, "e7d8")
-    result should matchPattern { case _: MoveResult.PromotionRequired => }
-    result match
-      case MoveResult.PromotionRequired(_, _, _, _, captured, _) =>
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected PromotionRequired")
-
-  // ──── completePromotion ──────────────────────────────────────────────────
-
-  test("completePromotion applies move and places queen"):
-    // Black king on h1: not attacked by queen on e8 (different file, rank, and diagonals)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.Moved => }
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        newBoard.pieceAt(sq(File.E, Rank.R7)) should be (None)
-        newHistory.moves should have length 1
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion with rook underpromotion"):
-    // Black king on h1: not attacked by rook on e8 (different file and rank)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Rook, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Rook))
-      case _ => fail("Expected Moved with Rook")
-
-  test("completePromotion with bishop underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Bishop, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Bishop)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Bishop))
-      case _ => fail("Expected Moved with Bishop")
-
-  test("completePromotion with knight underpromotion"):
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved with Knight")
-
-  test("completePromotion captures opponent piece"):
-    // Black king on h1: after white queen captures d8 queen, h1 king is safe (queen on d8 does not attack h1)
-    val board = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/7k").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.D, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result match
-      case MoveResult.Moved(newBoard, _, captured, _) =>
-        newBoard.pieceAt(sq(File.D, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-        captured should be (Some(Piece(Color.Black, PieceType.Queen)))
-      case _ => fail("Expected Moved with captured piece")
-
-  test("completePromotion for black pawn to R1"):
-    val board = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R2), sq(File.E, Rank.R1),
-      PromotionPiece.Knight, Color.Black
-    )
-    result match
-      case MoveResult.Moved(newBoard, newHistory, _, _) =>
-        newBoard.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Knight)))
-        newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Knight))
-      case _ => fail("Expected Moved")
-
-  test("completePromotion evaluates check after promotion"):
-    val board = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.E, Rank.R7), sq(File.E, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case _: MoveResult.MovedInCheck => }
-
-  test("completePromotion full round-trip via processMove then completePromotion"):
-    // Black king on h1: not attacked by queen on e8
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/8/7k").get
-    GameController.processMove(board, GameHistory.empty, Color.White, "e7e8") match
-      case MoveResult.PromotionRequired(from, to, boardBefore, histBefore, _, turn) =>
-        val result = GameController.completePromotion(boardBefore, histBefore, from, to, PromotionPiece.Queen, turn)
-        result should matchPattern { case _: MoveResult.Moved => }
-        result match
-          case MoveResult.Moved(finalBoard, finalHistory, _, _) =>
-            finalBoard.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-            finalHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-          case _ => fail("Expected Moved")
-      case _ => fail("Expected PromotionRequired")
-
-  test("completePromotion results in checkmate when promotion delivers checkmate"):
-    // Black king a8, white pawn h7, white king b6.
-    // After h7→h8=Q: Qh8 attacks rank 8 putting Ka8 in check;
-    // a7 covered by Kb6, b7 covered by Kb6, b8 covered by Qh8 — no escape.
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.H, Rank.R7), sq(File.H, Rank.R8),
-      PromotionPiece.Queen, Color.White
-    )
-    result should matchPattern { case MoveResult.Checkmate(_) => }
-    result match
-      case MoveResult.Checkmate(winner) => winner should be (Color.White)
-      case _ => fail("Expected Checkmate")
-
-  test("completePromotion results in stalemate when promotion stalemates opponent"):
-    // Black king a8, white pawn b7, white bishop c7, white king b6.
-    // After b7→b8=N: knight on b8 (doesn't check a8); a7 and b7 covered by Kb6;
-    // b8 defended by Bc7 so Ka8xb8 would walk into bishop — no legal moves.
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val result = GameController.completePromotion(
-      board, GameHistory.empty,
-      sq(File.B, Rank.R7), sq(File.B, Rank.R8),
-      PromotionPiece.Knight, Color.White
-    )
-    result should be (MoveResult.Stalemate)

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineEdgeCasesTest.scala

@@ -1,214 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests for GameEngine edge cases and uncovered paths */
-class GameEngineEdgeCasesTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles empty input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Please enter a valid move or command")
-
-  test("GameEngine processes quit command"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("quit")
-    // Quit just returns, no events
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine processes q command (short form)"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("q")
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine handles uppercase quit"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("QUIT")
-    observer.events.isEmpty shouldBe true
-
-  test("GameEngine handles undo on empty history"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.canUndo shouldBe false
-    engine.processUserInput("undo")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Nothing to undo")
-
-  test("GameEngine handles redo on empty redo history"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.canRedo shouldBe false
-    engine.processUserInput("redo")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Nothing to redo")
-
-  test("GameEngine parses invalid move format"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("invalid_move_format")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Invalid move format")
-
-  test("GameEngine handles lowercase input normalization"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("  UNDO  ")  // With spaces and uppercase
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]  // No moves to undo yet
-
-  test("GameEngine preserves board state on invalid move"):
-    val engine = new GameEngine()
-    val initialBoard = engine.board
-    
-    engine.processUserInput("invalid")
-    
-    engine.board shouldBe initialBoard
-
-  test("GameEngine preserves turn on invalid move"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    
-    engine.processUserInput("invalid")
-    
-    engine.turn shouldBe initialTurn
-
-  test("GameEngine undo with no commands available"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Make a valid move
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    // Undo it
-    engine.processUserInput("undo")
-    
-    // Board should be reset
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-  test("GameEngine redo after undo"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    val turnAfterMove = engine.turn
-    observer.events.clear()
-    
-    engine.processUserInput("undo")
-    engine.processUserInput("redo")
-    
-    engine.board shouldBe boardAfterMove
-    engine.turn shouldBe turnAfterMove
-
-  test("GameEngine canUndo flag tracks state correctly"):
-    val engine = new GameEngine()
-    
-    engine.canUndo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.canUndo shouldBe true
-    engine.processUserInput("undo")
-    engine.canUndo shouldBe false
-
-  test("GameEngine canRedo flag tracks state correctly"):
-    val engine = new GameEngine()
-    
-    engine.canRedo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.canRedo shouldBe false
-    engine.processUserInput("undo")
-    engine.canRedo shouldBe true
-
-  test("GameEngine command history is accessible"):
-    val engine = new GameEngine()
-    
-    engine.commandHistory.isEmpty shouldBe true
-    engine.processUserInput("e2e4")
-    engine.commandHistory.size shouldBe 1
-
-  test("GameEngine processes multiple moves in sequence"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-    
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    
-    observer.events.size shouldBe 2
-    engine.commandHistory.size shouldBe 2
-
-  test("GameEngine can undo multiple moves"):
-    val engine = new GameEngine()
-    
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    
-    engine.processUserInput("undo")
-    engine.turn shouldBe Color.Black
-    
-    engine.processUserInput("undo")
-    engine.turn shouldBe Color.White
-
-  test("GameEngine thread-safe operations"):
-    val engine = new GameEngine()
-    
-    // Access from synchronized methods
-    val board = engine.board
-    val history = engine.history
-    val turn = engine.turn
-    val canUndo = engine.canUndo
-    val canRedo = engine.canRedo
-    
-    board shouldBe Board.initial
-    canUndo shouldBe false
-    canRedo shouldBe false
-
-
-private class MockObserver extends Observer:
-  val events = mutable.ListBuffer[GameEvent]()
-  
-  override def onGameEvent(event: GameEvent): Unit =
-    events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala

@@ -1,93 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, CheckDetectedEvent, CheckmateEvent, StalemateEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests for GameEngine check/checkmate/stalemate paths */
-class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles Checkmate (Fool's Mate)"):
-    val engine = new GameEngine()
-    val observer = new EndingMockObserver()
-    engine.subscribe(observer)
-    
-    // Play Fool's mate
-    engine.processUserInput("f2f3")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g2g4")
-    
-    observer.events.clear()
-    engine.processUserInput("d8h4")
-    
-    // Verify CheckmateEvent
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[CheckmateEvent]
-    
-    val event = observer.events.head.asInstanceOf[CheckmateEvent]
-    event.winner shouldBe Color.Black
-    
-    // Board should be reset after checkmate
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-  test("GameEngine handles check detection"):
-    val engine = new GameEngine()
-    val observer = new EndingMockObserver()
-    engine.subscribe(observer)
-    
-    // Play a simple check
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("f1c4")
-    engine.processUserInput("g8f6")
-    
-    observer.events.clear()
-    engine.processUserInput("c4f7") // Check!
-    
-    val checkEvents = observer.events.collect { case e: CheckDetectedEvent => e }
-    checkEvents.size shouldBe 1
-    checkEvents.head.turn shouldBe Color.Black // Black is now in check
-    
-  // Shortest known stalemate is 19 moves. Here is a faster one:
-  // e3 a5 Qh5 Ra6 Qxa5 h5 h4 Rah6 Qxc7 f6 Qxd7+ Kf7 Qxb7 Qd3 Qxb8 Qh7 Qxc8 Kg6 Qe6
-  // Wait, let's just use Sam Loyd's 10-move stalemate:
-  // 1. e3 a5 2. Qh5 Ra6 3. Qxa5 h5 4. h4 Rah6 5. Qxc7 f6 6. Qxd7+ Kf7 7. Qxb7 Qd3 8. Qxb8 Qh7 9. Qxc8 Kg6 10. Qe6
-  test("GameEngine handles Stalemate via 10-move known sequence"):
-    val engine = new GameEngine()
-    val observer = new EndingMockObserver()
-    engine.subscribe(observer)
-    
-    val moves = List(
-      "e2e3", "a7a5",
-      "d1h5", "a8a6",
-      "h5a5", "h7h5",
-      "h2h4", "a6h6",
-      "a5c7", "f7f6",
-      "c7d7", "e8f7",
-      "d7b7", "d8d3",
-      "b7b8", "d3h7",
-      "b8c8", "f7g6",
-      "c8e6"
-    )
-    
-    moves.dropRight(1).foreach(engine.processUserInput)
-    
-    observer.events.clear()
-    engine.processUserInput(moves.last)
-    
-    val stalemateEvents = observer.events.collect { case e: StalemateEvent => e }
-    stalemateEvents.size shouldBe 1
-    
-    // Board should be reset after stalemate
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-private class EndingMockObserver extends Observer:
-  val events = mutable.ListBuffer[GameEvent]()
-  
-  override def onGameEvent(event: GameEvent): Unit =
-    events += event

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineHandleFailedMoveTest.scala

@@ -1,110 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests to maximize handleFailedMove coverage */
-class GameEngineHandleFailedMoveTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles InvalidFormat error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("not_a_valid_move_format")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg1 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg1 should include("Invalid move format")
-
-  test("GameEngine handles NoPiece error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("h3h4")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg2 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg2 should include("No piece on that square")
-
-  test("GameEngine handles WrongColor error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")  // White move
-    observer.events.clear()
-    
-    engine.processUserInput("a1b2")  // Try to move black's rook position with white's move (wrong color)
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg3 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg3 should include("That is not your piece")
-
-  test("GameEngine handles IllegalMove error type"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e1")  // Try pawn backward
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val msg4 = observer.events.head.asInstanceOf[InvalidMoveEvent].reason
-    msg4 should include("Illegal move")
-
-  test("GameEngine invalid move message for InvalidFormat"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("xyz123")
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("coordinate notation")
-
-  test("GameEngine invalid move message for NoPiece"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("a3a4")  // a3 is empty
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("No piece")
-
-  test("GameEngine invalid move message for WrongColor"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    engine.processUserInput("e4e5")  // e4 has white pawn, it's black's turn
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("not your piece")
-
-  test("GameEngine invalid move message for IllegalMove"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    engine.processUserInput("e2e1")  // Pawn can't move backward
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Illegal move")
-
-  test("GameEngine board unchanged after each type of invalid move"):
-    val engine = new GameEngine()
-    val initial = engine.board
-    
-    engine.processUserInput("invalid")
-    engine.board shouldBe initial
-    
-    engine.processUserInput("h3h4")
-    engine.board shouldBe initial
-    
-    engine.processUserInput("e2e1")
-    engine.board shouldBe initial

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineInvalidMovesTest.scala

@@ -1,114 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, InvalidMoveEvent, MoveExecutedEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-/** Tests for GameEngine invalid move handling via handleFailedMove */
-class GameEngineInvalidMovesTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine handles no piece at source square"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Try to move from h1 which may be empty or not have our piece
-    // We'll try from a clearly empty square
-    engine.processUserInput("h1h2")
-    
-    // Should get an InvalidMoveEvent about NoPiece
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles moving wrong color piece"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // White moves first
-    engine.processUserInput("e2e4")
-    observer.events.clear()
-    
-    // White tries to move again (should fail - it's black's turn)
-    // But we need to try a move that looks legal but has wrong color
-    // This is hard to test because we'd need to be black and move white's piece
-    // Let's skip this for now and focus on testable cases
-    
-    // Actually, let's try moving a square that definitely has the wrong piece
-    // Move a white pawn as black by reaching that position
-    engine.processUserInput("e7e5")
-    observer.events.clear()
-    
-    // Now try to move white's e4 pawn as black (it's black's turn but e4 is white)
-    engine.processUserInput("e4e5")
-    
-    observer.events.size shouldBe 1
-    val event = observer.events.head
-    event shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles illegal move"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // A pawn can't move backward
-    engine.processUserInput("e2e1")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("Illegal move")
-
-  test("GameEngine handles pawn trying to move 3 squares"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Pawn can only move 1 or 2 squares on first move, not 3
-    engine.processUserInput("e2e5")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-
-  test("GameEngine handles moving from empty square"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // h3 is empty in starting position
-    engine.processUserInput("h3h4")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[InvalidMoveEvent]
-    val event = observer.events.head.asInstanceOf[InvalidMoveEvent]
-    event.reason should include("No piece on that square")
-
-  test("GameEngine processes valid move after invalid attempt"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    
-    // Try invalid move
-    engine.processUserInput("h3h4")
-    observer.events.clear()
-    
-    // Make valid move
-    engine.processUserInput("e2e4")
-    
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe an[MoveExecutedEvent]
-
-  test("GameEngine maintains state after failed move attempt"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    val initialBoard = engine.board
-    
-    // Try invalid move
-    engine.processUserInput("h3h4")
-    
-    // State should not change
-    engine.turn shouldBe initialTurn
-    engine.board shouldBe initialBoard

modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala

@@ -1,167 +0,0 @@
-package de.nowchess.chess.engine
-
-import de.nowchess.api.board.{Board, Color, File, Piece, PieceType, Rank, Square}
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.notation.FenParser
-import de.nowchess.chess.observer.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameEnginePromotionTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  private def captureEvents(engine: GameEngine): collection.mutable.ListBuffer[GameEvent] =
-    val events = collection.mutable.ListBuffer[GameEvent]()
-    engine.subscribe(new Observer { def onGameEvent(e: GameEvent): Unit = events += e })
-    events
-
-  test("processUserInput fires PromotionRequiredEvent when pawn reaches back rank") {
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-
-    events.exists(_.isInstanceOf[PromotionRequiredEvent]) should be (true)
-    events.collect { case e: PromotionRequiredEvent => e }.head.from should be (sq(File.E, Rank.R7))
-  }
-
-  test("isPendingPromotion is true after PromotionRequired input") {
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-
-    engine.isPendingPromotion should be (true)
-  }
-
-  test("isPendingPromotion is false before any promotion input") {
-    val engine = new GameEngine()
-    engine.isPendingPromotion should be (false)
-  }
-
-  test("completePromotion fires MoveExecutedEvent with promoted piece") {
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-    engine.board.pieceAt(sq(File.E, Rank.R7)) should be (None)
-    engine.history.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))
-    events.exists(_.isInstanceOf[MoveExecutedEvent]) should be (true)
-  }
-
-  test("completePromotion with rook underpromotion") {
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.completePromotion(PromotionPiece.Rook)
-
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Rook)))
-  }
-
-  test("completePromotion with no pending promotion fires InvalidMoveEvent") {
-    val engine = new GameEngine()
-    val events = captureEvents(engine)
-
-    engine.completePromotion(PromotionPiece.Queen)
-
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
-    engine.isPendingPromotion should be (false)
-  }
-
-  test("completePromotion fires CheckDetectedEvent when promotion gives check") {
-    val promotionBoard = FenParser.parseBoard("3k4/4P3/8/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = promotionBoard)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.completePromotion(PromotionPiece.Queen)
-
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (true)
-  }
-
-  test("completePromotion results in Moved when promotion doesn't give check") {
-    // White pawn on e7, black king on a2 (far away, not in check after promotion)
-    val board = FenParser.parseBoard("8/4P3/8/8/8/8/k7/8").get
-    val engine = new GameEngine(initialBoard = board)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-    events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
-  }
-
-  test("completePromotion results in Checkmate when promotion delivers checkmate") {
-    // Black king on a8, white king on b6, white pawn on h7
-    // h7->h8=Q delivers checkmate
-    val board = FenParser.parseBoard("k7/7P/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("h7h8")
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[CheckmateEvent]) should be (true)
-  }
-
-  test("completePromotion results in Stalemate when promotion creates stalemate") {
-    // Black king on a8, white pawn on b7, white bishop on c7, white king on b6
-    // b7->b8=N: no check; Ka8 has no legal moves -> stalemate
-    val board = FenParser.parseBoard("k7/1PB5/1K6/8/8/8/8/8").get
-    val engine = new GameEngine(initialBoard = board)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("b7b8")
-    engine.completePromotion(PromotionPiece.Knight)
-
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[StalemateEvent]) should be (true)
-  }
-
-  test("completePromotion with black pawn promotion results in Moved") {
-    // Black pawn e2, white king h3 (not on rank 1 or file e), black king a8
-    // e2->e1=Q: queen on e1 does not attack h3 -> normal Moved
-    val board = FenParser.parseBoard("k7/8/8/8/8/7K/4p3/8").get
-    val engine = new GameEngine(initialBoard = board, initialTurn = Color.Black)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e2e1")
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    engine.board.pieceAt(sq(File.E, Rank.R1)) should be (Some(Piece(Color.Black, PieceType.Queen)))
-    events.filter(_.isInstanceOf[MoveExecutedEvent]) should not be empty
-    events.exists(_.isInstanceOf[CheckDetectedEvent]) should be (false)
-  }
-
-  test("completePromotion catch-all fires InvalidMoveEvent for unexpected MoveResult") {
-    // Inject a function that returns an unexpected MoveResult to hit the catch-all case
-    val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val stubFn: (de.nowchess.api.board.Board, de.nowchess.chess.logic.GameHistory, Square, Square, PromotionPiece, Color) => de.nowchess.chess.controller.MoveResult =
-      (_, _, _, _, _, _) => de.nowchess.chess.controller.MoveResult.NoPiece
-    val engine = new GameEngine(initialBoard = promotionBoard, completePromotionFn = stubFn)
-    val events = captureEvents(engine)
-
-    engine.processUserInput("e7e8")
-    engine.isPendingPromotion should be (true)
-
-    engine.completePromotion(PromotionPiece.Queen)
-
-    engine.isPendingPromotion should be (false)
-    events.exists(_.isInstanceOf[InvalidMoveEvent]) should be (true)
-  }

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineTest.scala

@@ -1,310 +0,0 @@
-package de.nowchess.chess.engine
-
-import scala.collection.mutable
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import de.nowchess.chess.observer.{Observer, GameEvent, MoveExecutedEvent, CheckDetectedEvent, BoardResetEvent, InvalidMoveEvent}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameEngineTest extends AnyFunSuite with Matchers:
-
-  test("GameEngine starts with initial board state"):
-    val engine = new GameEngine()
-    engine.board shouldBe Board.initial
-    engine.history shouldBe GameHistory.empty
-    engine.turn shouldBe Color.White
-
-  test("GameEngine accepts Observer subscription"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.observerCount shouldBe 1
-
-  test("GameEngine notifies observers on valid move"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.processUserInput("e2e4")
-    mockObserver.events.size shouldBe 1
-    mockObserver.events.head shouldBe a[MoveExecutedEvent]
-
-  test("GameEngine updates state after valid move"):
-    val engine = new GameEngine()
-    val initialTurn = engine.turn
-    engine.processUserInput("e2e4")
-    engine.turn shouldNot be(initialTurn)
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine notifies observers on invalid move"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.processUserInput("invalid_move")
-    mockObserver.events.size shouldBe 1
-
-  test("GameEngine notifies multiple observers"):
-    val engine = new GameEngine()
-    val observer1 = new MockObserver()
-    val observer2 = new MockObserver()
-    engine.subscribe(observer1)
-    engine.subscribe(observer2)
-    engine.processUserInput("e2e4")
-    observer1.events.size shouldBe 1
-    observer2.events.size shouldBe 1
-
-  test("GameEngine allows observer unsubscription"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.unsubscribe(mockObserver)
-    engine.observerCount shouldBe 0
-
-  test("GameEngine unsubscribed observer receives no events"):
-    val engine = new GameEngine()
-    val mockObserver = new MockObserver()
-    engine.subscribe(mockObserver)
-    engine.unsubscribe(mockObserver)
-    engine.processUserInput("e2e4")
-    mockObserver.events.size shouldBe 0
-
-  test("GameEngine reset notifies observers and resets state"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.reset()
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-    observer.events.size shouldBe 1
-
-  test("GameEngine processes sequence of moves"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    observer.events.size shouldBe 2
-    engine.turn shouldBe Color.White
-
-  test("GameEngine is thread-safe for synchronized operations"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val t = new Thread(() => engine.processUserInput("e2e4"))
-    t.start()
-    t.join()
-    observer.events.size shouldBe 1
-
-  test("GameEngine canUndo returns false initially"):
-    val engine = new GameEngine()
-    engine.canUndo shouldBe false
-
-  test("GameEngine canUndo returns true after move"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.canUndo shouldBe true
-
-  test("GameEngine canRedo returns false initially"):
-    val engine = new GameEngine()
-    engine.canRedo shouldBe false
-
-  test("GameEngine undo restores previous state"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.undo()
-    engine.board shouldBe Board.initial
-    engine.turn shouldBe Color.White
-
-  test("GameEngine undo notifies observers"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-    engine.undo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[BoardResetEvent]
-
-  test("GameEngine redo replays undone move"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.undo()
-    engine.redo()
-    engine.board shouldBe boardAfterMove
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine canUndo false when nothing to undo"):
-    val engine = new GameEngine()
-    engine.canUndo shouldBe false
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.canUndo shouldBe false
-
-  test("GameEngine canRedo true after undo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.canRedo shouldBe true
-
-  test("GameEngine canRedo false after redo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.undo()
-    engine.redo()
-    engine.canRedo shouldBe false
-
-  test("GameEngine undo on empty history sends invalid event"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.undo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine redo on empty redo sends invalid event"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.redo()
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine undo via processUserInput"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.processUserInput("undo")
-    engine.board shouldBe Board.initial
-
-  test("GameEngine redo via processUserInput"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    val boardAfterMove = engine.board
-    engine.processUserInput("undo")
-    engine.processUserInput("redo")
-    engine.board shouldBe boardAfterMove
-
-  test("GameEngine handles empty input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    engine.processUserInput("")
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[InvalidMoveEvent]
-
-  test("GameEngine multiple undo/redo sequence"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g1f3")
-    
-    engine.turn shouldBe Color.Black
-    
-    engine.undo()
-    engine.turn shouldBe Color.White
-    
-    engine.undo()
-    engine.turn shouldBe Color.Black
-    
-    engine.undo()
-    engine.turn shouldBe Color.White
-    engine.board shouldBe Board.initial
-
-  test("GameEngine redo after multiple undos"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.processUserInput("g1f3")
-    
-    engine.undo()
-    engine.undo()
-    engine.undo()
-    
-    engine.redo()
-    engine.turn shouldBe Color.Black
-    
-    engine.redo()
-    engine.turn shouldBe Color.White
-    
-    engine.redo()
-    engine.turn shouldBe Color.Black
-
-  test("GameEngine new move after undo clears redo history"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    engine.undo()
-    engine.canRedo shouldBe true
-    
-    engine.processUserInput("e7e6")  // Different move
-    engine.canRedo shouldBe false
-
-  test("GameEngine command history tracking"):
-    val engine = new GameEngine()
-    engine.commandHistory.size shouldBe 0
-    
-    engine.processUserInput("e2e4")
-    engine.commandHistory.size shouldBe 1
-    
-    engine.processUserInput("e7e5")
-    engine.commandHistory.size shouldBe 2
-
-  test("GameEngine quit input"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val initialEvents = observer.events.size
-    engine.processUserInput("quit")
-    // quit should not produce an event
-    observer.events.size shouldBe initialEvents
-
-  test("GameEngine quit via q"):
-    val engine = new GameEngine()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    val initialEvents = observer.events.size
-    engine.processUserInput("q")
-    observer.events.size shouldBe initialEvents
-  
-  test("GameEngine undo notifies with BoardResetEvent after successful undo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-
-    engine.undo()
-
-    // Should have received a BoardResetEvent on undo
-    observer.events.size should be > 0
-    observer.events.exists(_.isInstanceOf[BoardResetEvent]) shouldBe true
-
-  test("GameEngine redo notifies with MoveExecutedEvent after successful redo"):
-    val engine = new GameEngine()
-    engine.processUserInput("e2e4")
-    engine.processUserInput("e7e5")
-    val boardAfterSecondMove = engine.board
-
-    engine.undo()
-    val observer = new MockObserver()
-    engine.subscribe(observer)
-    observer.events.clear()
-
-    engine.redo()
-
-    // Should have received a MoveExecutedEvent for the redo
-    observer.events.size shouldBe 1
-    observer.events.head shouldBe a[MoveExecutedEvent]
-    engine.board shouldBe boardAfterSecondMove
-    engine.turn shouldBe Color.White
-
-  // Mock Observer for testing
-  private class MockObserver extends Observer:
-    val events = mutable.ListBuffer[GameEvent]()
-    override def onGameEvent(event: GameEvent): Unit =
-      events += event
-

modules/core/src/test/scala/de/nowchess/chess/engine/MoveCommandDefaultsTest.scala

@@ -1,110 +0,0 @@
-package de.nowchess.chess.command
-
-import de.nowchess.api.board.{Square, File, Rank, Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class MoveCommandDefaultsTest extends AnyFunSuite with Matchers:
-  
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  // Tests for MoveCommand with default parameter values
-  test("MoveCommand with no moveResult defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.moveResult shouldBe None
-    cmd.execute() shouldBe false
-
-  test("MoveCommand with no previousBoard defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousBoard shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousHistory defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousHistory shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand with no previousTurn defaults to None"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.previousTurn shouldBe None
-    cmd.undo() shouldBe false
-
-  test("MoveCommand description is always returned"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4)
-    )
-    cmd.description shouldBe "Move from e2 to e4"
-
-  test("MoveCommand execute returns false when moveResult is None"):
-    val cmd = MoveCommand(
-      from = sq(File.A, Rank.R1),
-      to = sq(File.B, Rank.R3)
-    )
-    cmd.execute() shouldBe false
-
-  test("MoveCommand undo returns false when any previous state is None"):
-    // Missing previousBoard
-    val cmd1 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = None,
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd1.undo() shouldBe false
-
-    // Missing previousHistory
-    val cmd2 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = None,
-      previousTurn = Some(Color.White)
-    )
-    cmd2.undo() shouldBe false
-
-    // Missing previousTurn
-    val cmd3 = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = None
-    )
-    cmd3.undo() shouldBe false
-
-  test("MoveCommand execute returns true when moveResult is defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None))
-    )
-    cmd.execute() shouldBe true
-
-  test("MoveCommand undo returns true when all previous states are defined"):
-    val cmd = MoveCommand(
-      from = sq(File.E, Rank.R2),
-      to = sq(File.E, Rank.R4),
-      moveResult = Some(MoveResult.Successful(Board.initial, GameHistory.empty, Color.White, None)),
-      previousBoard = Some(Board.initial),
-      previousHistory = Some(GameHistory.empty),
-      previousTurn = Some(Color.White)
-    )
-    cmd.undo() shouldBe true

modules/core/src/test/scala/de/nowchess/chess/logic/CastlingRightsCalculatorTest.scala

@@ -1,70 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.CastlingRights
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class CastlingRightsCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("Empty history gives full castling rights"):
-    val rights = CastlingRightsCalculator.deriveCastlingRights(GameHistory.empty, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("White loses kingside rights after h1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R1), sq(File.H, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("White loses queenside rights after a1 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("White loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R1), sq(File.E, Rank.R2))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Black loses kingside rights after h8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.H, Rank.R8), sq(File.H, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.kingSide shouldBe false
-    rights.queenSide shouldBe true
-
-  test("Black loses queenside rights after a8 rook moves"):
-    val history = GameHistory.empty.addMove(sq(File.A, Rank.R8), sq(File.A, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights.queenSide shouldBe false
-    rights.kingSide shouldBe true
-
-  test("Black loses all rights after king moves"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R8), sq(File.E, Rank.R7))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.Black)
-    rights shouldBe CastlingRights.None
-
-  test("Castle move revokes all castling rights"):
-    val history = GameHistory.empty.addMove(
-      sq(File.E, Rank.R1),
-      sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
-    )
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.None
-
-  test("Other pieces moving does not revoke castling rights"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights shouldBe CastlingRights.Both
-
-  test("Multiple moves preserve white kingside but lose queenside"):
-    val history = GameHistory.empty
-      .addMove(sq(File.A, Rank.R1), sq(File.A, Rank.R2))  // White queenside rook moves
-      .addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))  // Black pawn moves
-    val rights = CastlingRightsCalculator.deriveCastlingRights(history, Color.White)
-    rights.kingSide shouldBe true
-    rights.queenSide shouldBe false

modules/core/src/test/scala/de/nowchess/chess/logic/EnPassantCalculatorTest.scala

@@ -1,101 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class EnPassantCalculatorTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
-
-  // ──── enPassantTarget ────────────────────────────────────────────────
-
-  test("enPassantTarget returns None for empty history"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    EnPassantCalculator.enPassantTarget(b, GameHistory.empty) shouldBe None
-
-  test("enPassantTarget returns None when last move was a single pawn push"):
-    val b = board(sq(File.E, Rank.R3) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R3))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns None when last move was not a pawn"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe None
-
-  test("enPassantTarget returns e3 after white pawn double push e2-e4"):
-    val b = board(sq(File.E, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R3))
-
-  test("enPassantTarget returns e6 after black pawn double push e7-e5"):
-    val b = board(sq(File.E, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R5))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.E, Rank.R6))
-
-  test("enPassantTarget returns d3 after white pawn double push d2-d4"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhitePawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R2), sq(File.D, Rank.R4))
-    EnPassantCalculator.enPassantTarget(b, h) shouldBe Some(sq(File.D, Rank.R3))
-
-  // ──── capturedPawnSquare ─────────────────────────────────────────────
-
-  test("capturedPawnSquare for white capturing on e6 returns e5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R6), Color.White) shouldBe sq(File.E, Rank.R5)
-
-  test("capturedPawnSquare for black capturing on e3 returns e4"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.E, Rank.R3), Color.Black) shouldBe sq(File.E, Rank.R4)
-
-  test("capturedPawnSquare for white capturing on d6 returns d5"):
-    EnPassantCalculator.capturedPawnSquare(sq(File.D, Rank.R6), Color.White) shouldBe sq(File.D, Rank.R5)
-
-  // ──── isEnPassant ────────────────────────────────────────────────────
-
-  test("isEnPassant returns true for valid white en passant capture"):
-    // White pawn on e5, black pawn just double-pushed to d5 (ep target = d6)
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe true
-
-  test("isEnPassant returns true for valid black en passant capture"):
-    // Black pawn on d4, white pawn just double-pushed to e4 (ep target = e3)
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.D, Rank.R4), sq(File.E, Rank.R3)) shouldBe true
-
-  test("isEnPassant returns false when no en passant target in history"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when piece at from is not a pawn"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhiteRook,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when to does not match ep target"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.E, Rank.R6)) shouldBe false
-
-  test("isEnPassant returns false when from square is empty"):
-    val b = board(sq(File.D, Rank.R5) -> Piece.BlackPawn)
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    EnPassantCalculator.isEnPassant(b, h, sq(File.E, Rank.R5), sq(File.D, Rank.R6)) shouldBe false

modules/core/src/test/scala/de/nowchess/chess/logic/GameContextTest.scala

@@ -0,0 +1,81 @@
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.*
+import de.nowchess.api.game.CastlingRights
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class GameContextTest extends AnyFunSuite with Matchers:
+
+  private def sq(f: File, r: Rank): Square = Square(f, r)
+  private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
+
+  test("GameContext.initial has Board.initial and CastlingRights.Both for both sides"):
+    GameContext.initial.board         shouldBe Board.initial
+    GameContext.initial.whiteCastling shouldBe CastlingRights.Both
+    GameContext.initial.blackCastling shouldBe CastlingRights.Both
+
+  test("castlingFor returns white rights for Color.White"):
+    GameContext.initial.castlingFor(Color.White) shouldBe CastlingRights.Both
+
+  test("castlingFor returns black rights for Color.Black"):
+    GameContext.initial.castlingFor(Color.Black) shouldBe CastlingRights.Both
+
+  test("withUpdatedRights updates white castling without touching black"):
+    val ctx = GameContext.initial.withUpdatedRights(Color.White, CastlingRights.None)
+    ctx.whiteCastling shouldBe CastlingRights.None
+    ctx.blackCastling shouldBe CastlingRights.Both
+
+  test("withUpdatedRights updates black castling without touching white"):
+    val ctx = GameContext.initial.withUpdatedRights(Color.Black, CastlingRights.None)
+    ctx.blackCastling shouldBe CastlingRights.None
+    ctx.whiteCastling shouldBe CastlingRights.Both
+
+  test("withCastle: white kingside — king e1→g1, rook h1→f1"):
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook
+    )
+    val after = b.withCastle(Color.White, CastleSide.Kingside)
+    after.pieceAt(sq(File.G, Rank.R1)) shouldBe Some(Piece.WhiteKing)
+    after.pieceAt(sq(File.F, Rank.R1)) shouldBe Some(Piece.WhiteRook)
+    after.pieceAt(sq(File.E, Rank.R1)) shouldBe None
+    after.pieceAt(sq(File.H, Rank.R1)) shouldBe None
+
+  test("withCastle: white queenside — king e1→c1, rook a1→d1"):
+    val b = board(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R1) -> Piece.WhiteRook
+    )
+    val after = b.withCastle(Color.White, CastleSide.Queenside)
+    after.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
+    after.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
+    after.pieceAt(sq(File.E, Rank.R1)) shouldBe None
+    after.pieceAt(sq(File.A, Rank.R1)) shouldBe None
+
+  test("withCastle: black kingside — king e8→g8, rook h8→f8"):
+    val b = board(
+      sq(File.E, Rank.R8) -> Piece.BlackKing,
+      sq(File.H, Rank.R8) -> Piece.BlackRook
+    )
+    val after = b.withCastle(Color.Black, CastleSide.Kingside)
+    after.pieceAt(sq(File.G, Rank.R8)) shouldBe Some(Piece.BlackKing)
+    after.pieceAt(sq(File.F, Rank.R8)) shouldBe Some(Piece.BlackRook)
+    after.pieceAt(sq(File.E, Rank.R8)) shouldBe None
+    after.pieceAt(sq(File.H, Rank.R8)) shouldBe None
+
+  test("withCastle: black queenside — king e8→c8, rook a8→d8"):
+    val b = board(
+      sq(File.E, Rank.R8) -> Piece.BlackKing,
+      sq(File.A, Rank.R8) -> Piece.BlackRook
+    )
+    val after = b.withCastle(Color.Black, CastleSide.Queenside)
+    after.pieceAt(sq(File.C, Rank.R8)) shouldBe Some(Piece.BlackKing)
+    after.pieceAt(sq(File.D, Rank.R8)) shouldBe Some(Piece.BlackRook)
+    after.pieceAt(sq(File.E, Rank.R8)) shouldBe None
+    after.pieceAt(sq(File.A, Rank.R8)) shouldBe None
+
+  test("GameContext single-arg apply defaults to CastlingRights.None for both sides"):
+    val ctx = GameContext(Board.initial)
+    ctx.whiteCastling shouldBe CastlingRights.None
+    ctx.blackCastling shouldBe CastlingRights.None

modules/core/src/test/scala/de/nowchess/chess/logic/GameHistoryTest.scala

@@ -1,71 +0,0 @@
-package de.nowchess.chess.logic
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class GameHistoryTest extends AnyFunSuite with Matchers:
-
-  private def sq(f: File, r: Rank): Square = Square(f, r)
-
-  test("GameHistory starts empty"):
-    val history = GameHistory.empty
-    history.moves shouldBe empty
-
-  test("GameHistory can add a move"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    history.moves should have length 1
-    history.moves.head.from shouldBe sq(File.E, Rank.R2)
-    history.moves.head.to shouldBe sq(File.E, Rank.R4)
-    history.moves.head.castleSide shouldBe None
-
-  test("GameHistory can add multiple moves in order"):
-    val h1 = GameHistory.empty
-    val h2 = h1.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    val h3 = h2.addMove(sq(File.C, Rank.R7), sq(File.C, Rank.R5))
-    h3.moves should have length 2
-    h3.moves(0).from shouldBe sq(File.E, Rank.R2)
-    h3.moves(1).from shouldBe sq(File.C, Rank.R7)
-
-  test("GameHistory can add a castle move"):
-    val history = GameHistory.empty.addMove(
-      sq(File.E, Rank.R1),
-      sq(File.G, Rank.R1),
-      Some(CastleSide.Kingside)
-    )
-    history.moves.head.castleSide shouldBe Some(CastleSide.Kingside)
-
-  test("GameHistory.addMove with two arguments uses None for castleSide default"):
-    val history = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    history.moves should have length 1
-    history.moves.head.castleSide shouldBe None
-
-  test("Move with promotion records the promotion piece"):
-    val move = HistoryMove(sq(File.E, Rank.R7), sq(File.E, Rank.R8), None, Some(PromotionPiece.Queen))
-    move.promotionPiece should be (Some(PromotionPiece.Queen))
-
-  test("Normal move has no promotion piece"):
-    val move = HistoryMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4), None, None)
-    move.promotionPiece should be (None)
-
-  test("addMove with promotion stores promotionPiece"):
-    val history = GameHistory.empty
-    val newHistory = history.addMove(sq(File.E, Rank.R7), sq(File.E, Rank.R8), None, Some(PromotionPiece.Rook))
-    newHistory.moves should have length 1
-    newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Rook))
-
-  test("addMove with castleSide only uses promotionPiece default (None)"):
-    val history = GameHistory.empty
-    // With overload 3 removed, this uses the 4-param version and triggers addMove$default$4
-    val newHistory = history.addMove(sq(File.E, Rank.R1), sq(File.G, Rank.R1), Some(CastleSide.Kingside))
-    newHistory.moves should have length 1
-    newHistory.moves.head.castleSide should be (Some(CastleSide.Kingside))
-    newHistory.moves.head.promotionPiece should be (None)
-
-  test("addMove using named parameters with only promotion, using castleSide default"):
-    val history = GameHistory.empty
-    val newHistory = history.addMove(from = sq(File.E, Rank.R7), to = sq(File.E, Rank.R8), promotionPiece = Some(PromotionPiece.Queen))
-    newHistory.moves should have length 1
-    newHistory.moves.head.castleSide should be (None)
-    newHistory.moves.head.promotionPiece should be (Some(PromotionPiece.Queen))

modules/core/src/test/scala/de/nowchess/chess/logic/GameRulesTest.scala

@@ -2,7 +2,7 @@ package de.nowchess.chess.logic
 
 import de.nowchess.api.board.*
 import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.GameHistory
+import de.nowchess.chess.logic.GameContext
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -12,11 +12,7 @@ class GameRulesTest extends AnyFunSuite with Matchers:
   private def board(entries: (Square, Piece)*): Board = Board(entries.toMap)
 
   /** Wrap a board in a GameContext with no castling rights — for non-castling tests. */
-  private def testLegalMoves(entries: (Square, Piece)*)(color: Color): Set[(Square, Square)] =
-    GameRules.legalMoves(Board(entries.toMap), GameHistory.empty, color)
-
-  private def testGameStatus(entries: (Square, Piece)*)(color: Color): PositionStatus =
-    GameRules.gameStatus(Board(entries.toMap), GameHistory.empty, color)
+  private def ctx(entries: (Square, Piece)*): GameContext = GameContext(Board(entries.toMap))
 
   // ──── isInCheck ──────────────────────────────────────────────────────
 
@@ -45,20 +41,20 @@ class GameRulesTest extends AnyFunSuite with Matchers:
   test("legalMoves: move that exposes own king to rook is excluded"):
     // White King E1, White Rook E4 (pinned on E-file), Black Rook E8
     // Moving the White Rook off the E-file would expose the king
-    val moves = testLegalMoves(
+    val moves = GameRules.legalMoves(ctx(
       sq(File.E, Rank.R1) -> Piece.WhiteKing,
       sq(File.E, Rank.R4) -> Piece.WhiteRook,
       sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
+    ), Color.White)
     moves should not contain (sq(File.E, Rank.R4) -> sq(File.D, Rank.R4))
 
   test("legalMoves: move that blocks check is included"):
     // White King E1 in check from Black Rook E8; White Rook A5 can interpose on E5
-    val moves = testLegalMoves(
+    val moves = GameRules.legalMoves(ctx(
       sq(File.E, Rank.R1) -> Piece.WhiteKing,
       sq(File.A, Rank.R5) -> Piece.WhiteRook,
       sq(File.E, Rank.R8) -> Piece.BlackRook
-    )(Color.White)
+    ), Color.White)
     moves should contain(sq(File.A, Rank.R5) -> sq(File.E, Rank.R5))
 
   // ──── gameStatus ──────────────────────────────────────────────────────
@@ -66,96 +62,70 @@ class GameRulesTest extends AnyFunSuite with Matchers:
   test("gameStatus: checkmate returns Mated"):
     // White Qh8, Ka6; Black Ka8
     // Qh8 attacks Ka8 along rank 8; all escape squares covered (spec-verified position)
-    testGameStatus(
+    GameRules.gameStatus(ctx(
       sq(File.H, Rank.R8) -> Piece.WhiteQueen,
       sq(File.A, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Mated
+    ), Color.Black) shouldBe PositionStatus.Mated
 
   test("gameStatus: stalemate returns Drawn"):
     // White Qb6, Kc6; Black Ka8
     // Black king has no legal moves and is not in check (spec-verified position)
-    testGameStatus(
+    GameRules.gameStatus(ctx(
       sq(File.B, Rank.R6) -> Piece.WhiteQueen,
       sq(File.C, Rank.R6) -> Piece.WhiteKing,
       sq(File.A, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.Drawn
+    ), Color.Black) shouldBe PositionStatus.Drawn
 
   test("gameStatus: king in check with legal escape returns InCheck"):
     // White Ra8 attacks Black Ke8 along rank 8; king can escape to d7, e7, f7
-    testGameStatus(
+    GameRules.gameStatus(ctx(
       sq(File.A, Rank.R8) -> Piece.WhiteRook,
       sq(File.E, Rank.R8) -> Piece.BlackKing
-    )(Color.Black) shouldBe PositionStatus.InCheck
+    ), Color.Black) shouldBe PositionStatus.InCheck
 
   test("gameStatus: normal starting position returns Normal"):
-    GameRules.gameStatus(Board.initial, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
+    GameRules.gameStatus(GameContext(Board.initial), Color.White) shouldBe PositionStatus.Normal
 
   test("legalMoves: includes castling destination when available"):
-    val b = board(
+    val c = GameContext(
+      board = board(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
+      ),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameRules.legalMoves(c, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
 
   test("legalMoves: excludes castling when king is in check"):
-    val b = board(
+    val c = GameContext(
+      board = board(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.E, Rank.R8) -> Piece.BlackRook,
         sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    GameRules.legalMoves(b, GameHistory.empty, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
+      ),
+      whiteCastling = CastlingRights.Both,
+      blackCastling = CastlingRights.None
+    )
+    GameRules.legalMoves(c, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
 
   test("gameStatus: returns Normal (not Drawn) when castling is the only legal move"):
     // White King e1, Rook h1 (kingside castling available).
     // Black Rooks d2 and f2 box the king: d1 attacked by d2, e2 attacked by both,
     // f1 attacked by f2. King cannot move to any adjacent square without entering
     // an attacked square or an enemy piece. Only legal move: castle to g1.
-    val b = board(
+    val c = GameContext(
+      board = board(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.D, Rank.R2) -> Piece.BlackRook,
         sq(File.F, Rank.R2) -> Piece.BlackRook,
         sq(File.A, Rank.R8) -> Piece.BlackKing
-      )
-    // No history means castling rights are intact
-    GameRules.gameStatus(b, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
-
-  test("CastleSide.withCastle correctly positions pieces for Queenside castling"):
-    // Directly test the withCastle extension for Queenside (coverage gap on line 10)
-    val b = board(
-      sq(File.E, Rank.R1) -> Piece.WhiteKing,
-      sq(File.A, Rank.R1) -> Piece.WhiteRook,
-      sq(File.H, Rank.R8) -> Piece.BlackKing
+      ),
+      whiteCastling = CastlingRights(kingSide = true, queenSide = false),
+      blackCastling = CastlingRights.None
     )
-    val result = b.withCastle(Color.White, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R1)) shouldBe Some(Piece.WhiteKing)
-    result.pieceAt(sq(File.D, Rank.R1)) shouldBe Some(Piece.WhiteRook)
-    result.pieceAt(sq(File.E, Rank.R1)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R1)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Kingside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.H, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Kingside)
-    result.pieceAt(sq(File.G, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.F, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.H, Rank.R8)) shouldBe None
-
-  test("CastleSide.withCastle correctly positions pieces for Black Queenside castling"):
-    val b = board(
-      sq(File.E, Rank.R8) -> Piece.BlackKing,
-      sq(File.A, Rank.R8) -> Piece.BlackRook,
-      sq(File.A, Rank.R1) -> Piece.WhiteKing
-    )
-    val result = b.withCastle(Color.Black, CastleSide.Queenside)
-    result.pieceAt(sq(File.C, Rank.R8)) shouldBe Some(Piece.BlackKing)
-    result.pieceAt(sq(File.D, Rank.R8)) shouldBe Some(Piece.BlackRook)
-    result.pieceAt(sq(File.E, Rank.R8)) shouldBe None
-    result.pieceAt(sq(File.A, Rank.R8)) shouldBe None
+    GameRules.gameStatus(c, Color.White) shouldBe PositionStatus.Normal

modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala

@@ -2,8 +2,7 @@ package de.nowchess.chess.logic
 
 import de.nowchess.api.board.{Board, Color, File, Piece, Rank, Square}
 import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.{CastleSide, GameHistory}
-import de.nowchess.chess.notation.FenParser
+import de.nowchess.chess.logic.{GameContext, CastleSide}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -213,68 +212,167 @@ class MoveValidatorTest extends AnyFunSuite with Matchers:
     )
     MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R4))
 
-  // ──── Pawn – en passant targets ──────────────────────────────────────
+  // ──── castlingTargets ────────────────────────────────────────────────
 
-  test("white pawn includes ep target in legal moves after black double push"):
-    // Black pawn just double-pushed to d5 (ep target = d6); white pawn on e5
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should contain(sq(File.D, Rank.R6))
+  private def ctxWithRights(
+    entries: (Square, Piece)*
+  )(white: CastlingRights = CastlingRights.Both,
+    black: CastlingRights = CastlingRights.Both
+  ): GameContext =
+    GameContext(Board(entries.toMap), white, black)
 
-  test("white pawn does not include ep target without a preceding double push"):
-    val b = board(
-      sq(File.E, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5))  // single push
-    MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should not contain sq(File.D, Rank.R6)
+  test("castlingTargets: white kingside available when all conditions met"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should contain(sq(File.G, Rank.R1))
 
-  test("black pawn includes ep target in legal moves after white double push"):
-    // White pawn just double-pushed to e4 (ep target = e3); black pawn on d4
-    val b = board(
-      sq(File.D, Rank.R4) -> Piece.BlackPawn,
-      sq(File.E, Rank.R4) -> Piece.WhitePawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R3))
+  test("castlingTargets: white queenside available when all conditions met"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should contain(sq(File.C, Rank.R1))
 
-  test("pawn on wrong file does not get ep target from adjacent double push"):
-    // White pawn on a5, black pawn double-pushed to d5 — a5 is not adjacent to d5
-    val b = board(
-      sq(File.A, Rank.R5) -> Piece.WhitePawn,
-      sq(File.D, Rank.R5) -> Piece.BlackPawn
-    )
-    val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
-    MoveValidator.legalTargets(b, h, sq(File.A, Rank.R5)) should not contain sq(File.D, Rank.R6)
+  test("castlingTargets: black kingside available when all conditions met"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R8) -> Piece.BlackKing,
+      sq(File.H, Rank.R8) -> Piece.BlackRook,
+      sq(File.H, Rank.R1) -> Piece.WhiteKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.Black) should contain(sq(File.G, Rank.R8))
 
-  // ──── History-aware legalTargets fallback for non-pawn non-king pieces ─────
+  test("castlingTargets: black queenside available when all conditions met"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R8) -> Piece.BlackKing,
+      sq(File.A, Rank.R8) -> Piece.BlackRook,
+      sq(File.H, Rank.R1) -> Piece.WhiteKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.Black) should contain(sq(File.C, Rank.R8))
 
-  test("legalTargets with history delegates to geometry-only for non-pawn non-king pieces"):
-    val b = board(sq(File.D, Rank.R4) -> Piece.WhiteRook)
-    val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
-    MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) shouldBe MoveValidator.legalTargets(b, sq(File.D, Rank.R4))
+  test("castlingTargets: blocked when transit square is occupied"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.F, Rank.R1) -> Piece.WhiteBishop,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.G, Rank.R1)
 
-  // ──── isPromotionMove ────────────────────────────────────────────────
+  test("castlingTargets: blocked when king is in check"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.E, Rank.R8) -> Piece.BlackRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) shouldBe empty
 
-  test("White pawn reaching R8 is a promotion move"):
-    val b = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.E, Rank.R8)) should be (true)
+  test("castlingTargets: blocked when transit square f1 is attacked"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.F, Rank.R8) -> Piece.BlackRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.G, Rank.R1)
 
-  test("Black pawn reaching R1 is a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/8/4K3/8/4p3/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R2), Square(File.E, Rank.R1)) should be (true)
+  test("castlingTargets: blocked when landing square g1 is attacked"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.G, Rank.R8) -> Piece.BlackRook,
+      sq(File.A, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.G, Rank.R1)
 
-  test("Pawn capturing to back rank is a promotion move"):
-    val b = FenParser.parseBoard("3q4/4P3/8/8/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R7), Square(File.D, Rank.R8)) should be (true)
+  test("castlingTargets: blocked when kingSide right is false"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )(white = CastlingRights(kingSide = false, queenSide = true))
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.G, Rank.R1)
 
-  test("Pawn not reaching back rank is not a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4P3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R6)) should be (false)
+  test("castlingTargets: blocked when queenSide right is false"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.A, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )(white = CastlingRights(kingSide = true, queenSide = false))
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.C, Rank.R1)
 
-  test("Non-pawn piece is never a promotion move"):
-    val b = FenParser.parseBoard("8/8/8/4Q3/8/8/8/8").get
-    MoveValidator.isPromotionMove(b, Square(File.E, Rank.R5), Square(File.E, Rank.R8)) should be (false)
+  test("castlingTargets: blocked when relevant rook is not on home square"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.G, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) should not contain sq(File.G, Rank.R1)
+
+  // ──── context-aware legalTargets includes castling ────────────────────
+
+  test("legalTargets(ctx, from): king on e1 includes g1 when castling available"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.legalTargets(ctx, sq(File.E, Rank.R1)) should contain(sq(File.G, Rank.R1))
+
+  test("legalTargets(ctx, from): non-king pieces unchanged by context"):
+    val ctx = ctxWithRights(
+      sq(File.D, Rank.R4) -> Piece.WhiteBishop,
+      sq(File.H, Rank.R8) -> Piece.BlackKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteKing
+    )()
+    MoveValidator.legalTargets(ctx, sq(File.D, Rank.R4)) shouldBe
+      MoveValidator.legalTargets(ctx.board, sq(File.D, Rank.R4))
+
+  // ──── isCastle / castleSide / isLegal(ctx) ───────────────────────────
+
+  test("isCastle: returns true when king moves two files"):
+    val board = Board(Map(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook
+    ))
+    MoveValidator.isCastle(board, sq(File.E, Rank.R1), sq(File.G, Rank.R1)) shouldBe true
+
+  test("isCastle: returns false when king moves one file"):
+    val board = Board(Map(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing
+    ))
+    MoveValidator.isCastle(board, sq(File.E, Rank.R1), sq(File.F, Rank.R1)) shouldBe false
+
+  test("castleSide: returns Kingside when moving to higher file"):
+    MoveValidator.castleSide(sq(File.E, Rank.R1), sq(File.G, Rank.R1)) shouldBe CastleSide.Kingside
+
+  test("castleSide: returns Queenside when moving to lower file"):
+    MoveValidator.castleSide(sq(File.E, Rank.R1), sq(File.C, Rank.R1)) shouldBe CastleSide.Queenside
+
+  test("isLegal(ctx): returns true for legal castling move"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.isLegal(ctx, sq(File.E, Rank.R1), sq(File.G, Rank.R1)) shouldBe true
+
+  test("isLegal(ctx): returns false for illegal castling move when rights revoked"):
+    val ctx = ctxWithRights(
+      sq(File.E, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )(white = CastlingRights.None)
+    MoveValidator.isLegal(ctx, sq(File.E, Rank.R1), sq(File.G, Rank.R1)) shouldBe false
+
+  test("castlingTargets: returns empty when king not on home square"):
+    val ctx = ctxWithRights(
+      sq(File.D, Rank.R1) -> Piece.WhiteKing,
+      sq(File.H, Rank.R1) -> Piece.WhiteRook,
+      sq(File.H, Rank.R8) -> Piece.BlackKing
+    )()
+    MoveValidator.castlingTargets(ctx, Color.White) shouldBe empty

modules/core/src/test/scala/de/nowchess/chess/main/MainTest.scala

@@ -0,0 +1,12 @@
+package de.nowchess.chess.main
+
+import de.nowchess.chess.Main
+import java.io.ByteArrayInputStream
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class MainTest extends AnyFunSuite with Matchers:
+
+  test("main exits cleanly when 'quit' is entered"):
+    scala.Console.withIn(ByteArrayInputStream("quit\n".getBytes("UTF-8"))):
+      Main.main(Array.empty)

modules/core/src/test/scala/de/nowchess/chess/notation/FenExporterTest.scala

@@ -1,69 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class FenExporterTest extends AnyFunSuite with Matchers:
-
-  test("export initial position to FEN"):
-    val gameState = GameState.initial
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
-
-  test("export position after e4"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR",
-      activeColor = Color.Black,
-      castlingWhite = CastlingRights.Both,
-      castlingBlack = CastlingRights.Both,
-      enPassantTarget = Some(Square(File.E, Rank.R3)),
-      halfMoveClock = 0,
-      fullMoveNumber = 1,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1"
-
-  test("export position with no castling"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights.None,
-      castlingBlack = CastlingRights.None,
-      enPassantTarget = None,
-      halfMoveClock = 0,
-      fullMoveNumber = 1,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"
-
-  test("export position with partial castling"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights(kingSide = true, queenSide = false),
-      castlingBlack = CastlingRights(kingSide = false, queenSide = true),
-      enPassantTarget = None,
-      halfMoveClock = 5,
-      fullMoveNumber = 3,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w Kq - 5 3"
-
-  test("export position with en passant and move counts"):
-    val gameState = GameState(
-      piecePlacement = "rnbqkbnr/pp1ppppp/8/2pP4/8/8/PPPP1PPP/RNBQKBNR",
-      activeColor = Color.White,
-      castlingWhite = CastlingRights.Both,
-      castlingBlack = CastlingRights.Both,
-      enPassantTarget = Some(Square(File.C, Rank.R6)),
-      halfMoveClock = 2,
-      fullMoveNumber = 3,
-      status = GameStatus.InProgress
-    )
-    val fen = FenExporter.gameStateToFen(gameState)
-    fen shouldBe "rnbqkbnr/pp1ppppp/8/2pP4/8/8/PPPP1PPP/RNBQKBNR w KQkq c6 2 3"

modules/core/src/test/scala/de/nowchess/chess/notation/FenParserTest.scala

@@ -1,134 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.game.*
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class FenParserTest extends AnyFunSuite with Matchers:
-
-  test("parseBoard: initial position places pieces on correct squares"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(fen)
-
-    board.map(_.pieceAt(Square(File.E, Rank.R2))) shouldBe Some(Some(Piece.WhitePawn))
-    board.map(_.pieceAt(Square(File.E, Rank.R7))) shouldBe Some(Some(Piece.BlackPawn))
-    board.map(_.pieceAt(Square(File.E, Rank.R1))) shouldBe Some(Some(Piece.WhiteKing))
-    board.map(_.pieceAt(Square(File.E, Rank.R8))) shouldBe Some(Some(Piece.BlackKing))
-
-  test("parseBoard: empty board has no pieces"):
-    val fen = "8/8/8/8/8/8/8/8"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe defined
-    board.get.pieces.size shouldBe 0
-
-  test("parseBoard: returns None for missing rank (only 7 ranks)"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None for invalid piece character"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNX"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: partial position with two kings placed correctly"):
-    val fen = "8/8/4k3/8/4K3/8/8/8"
-    val board = FenParser.parseBoard(fen)
-
-    board.map(_.pieceAt(Square(File.E, Rank.R6))) shouldBe Some(Some(Piece.BlackKing))
-    board.map(_.pieceAt(Square(File.E, Rank.R4))) shouldBe Some(Some(Piece.WhiteKing))
-
-  test("testRoundTripInitialPosition"):
-    val originalFen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("testRoundTripEmptyBoard"):
-    val originalFen = "8/8/8/8/8/8/8/8"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("testRoundTripPartialPosition"):
-    val originalFen = "8/8/4k3/8/4K3/8/8/8"
-    val board = FenParser.parseBoard(originalFen)
-    val exportedFen = board.map(FenExporter.boardToFen)
-
-    exportedFen shouldBe Some(originalFen)
-
-  test("parse full FEN - initial position"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe true
-    gameState.get.activeColor shouldBe Color.White
-    gameState.get.castlingWhite.kingSide shouldBe true
-    gameState.get.castlingWhite.queenSide shouldBe true
-    gameState.get.castlingBlack.kingSide shouldBe true
-    gameState.get.castlingBlack.queenSide shouldBe true
-    gameState.get.enPassantTarget shouldBe None
-    gameState.get.halfMoveClock shouldBe 0
-    gameState.get.fullMoveNumber shouldBe 1
-
-  test("parse full FEN - after e4"):
-    val fen = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.get.activeColor shouldBe Color.Black
-    gameState.get.enPassantTarget shouldBe Some(Square(File.E, Rank.R3))
-
-  test("parse full FEN - invalid parts count"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parse full FEN - invalid color"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR x KQkq - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parse full FEN - invalid castling"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w XYZ - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe false
-
-  test("parseFen: castling '-' produces CastlingRights.None for both sides"):
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"
-    val gameState = FenParser.parseFen(fen)
-
-    gameState.isDefined shouldBe true
-    gameState.get.castlingWhite.kingSide shouldBe false
-    gameState.get.castlingWhite.queenSide shouldBe false
-    gameState.get.castlingBlack.kingSide shouldBe false
-    gameState.get.castlingBlack.queenSide shouldBe false
-
-  test("parseBoard: returns None when a rank has too many files (overflow beyond 8)"):
-    // "9" alone would advance fileIdx to 9, exceeding 8 → None
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBN9"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None when a rank fails to parse (invalid middle rank)"):
-    // Invalid character 'X' in rank 4 should cause failure
-    val fen = "rnbqkbnr/pppppppp/8/8/XXXXXXXX/8/PPPPPPPP/RNBQKBNR"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty
-
-  test("parseBoard: returns None when a rank has 9 piece characters (fileIdx > 7)"):
-    // 9 pawns in one rank triggers fileIdx > 7 guard (line 78)
-    val fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/PPPPPPPPP"
-    val board = FenParser.parseBoard(fen)
-
-    board shouldBe empty

modules/core/src/test/scala/de/nowchess/chess/notation/PgnExporterTest.scala

@@ -1,102 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, HistoryMove, CastleSide}
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class PgnExporterTest extends AnyFunSuite with Matchers:
-
-  test("export empty game") {
-    val headers = Map("Event" -> "Test", "White" -> "A", "Black" -> "B")
-    val history = GameHistory.empty
-    val pgn = PgnExporter.exportGame(headers, history)
-
-    pgn.contains("[Event \"Test\"]") shouldBe true
-    pgn.contains("[White \"A\"]") shouldBe true
-    pgn.contains("[Black \"B\"]") shouldBe true
-  }
-
-  test("export single move") {
-    val headers = Map("Event" -> "Test", "White" -> "A", "Black" -> "B")
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4), None))
-    val pgn = PgnExporter.exportGame(headers, history)
-
-    pgn.contains("1. e2e4") shouldBe true
-  }
-
-  test("export castling") {
-    val headers = Map("Event" -> "Test")
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.G, Rank.R1), Some(CastleSide.Kingside)))
-    val pgn = PgnExporter.exportGame(headers, history)
-
-    pgn.contains("O-O") shouldBe true
-  }
-
-  test("export game sequence") {
-    val headers = Map("Event" -> "Test", "White" -> "A", "Black" -> "B", "Result" -> "1-0")
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4), None))
-      .addMove(HistoryMove(Square(File.C, Rank.R7), Square(File.C, Rank.R5), None))
-      .addMove(HistoryMove(Square(File.G, Rank.R1), Square(File.F, Rank.R3), None))
-    val pgn = PgnExporter.exportGame(headers, history)
-
-    pgn.contains("1. e2e4 c7c5") shouldBe true
-    pgn.contains("2. g1f3") shouldBe true
-  }
-
-  test("export game with no headers returns only move text") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4), None))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-
-    pgn shouldBe "1. e2e4 *"
-  }
-
-  test("export queenside castling") {
-    val headers = Map("Event" -> "Test")
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R1), Square(File.C, Rank.R1), Some(CastleSide.Queenside)))
-    val pgn = PgnExporter.exportGame(headers, history)
-
-    pgn.contains("O-O-O") shouldBe true
-  }
-
-  test("exportGame encodes promotion to Queen as =Q suffix") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R7), Square(File.E, Rank.R8), None, Some(PromotionPiece.Queen)))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-    pgn should include ("e7e8=Q")
-  }
-
-  test("exportGame encodes promotion to Rook as =R suffix") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R7), Square(File.E, Rank.R8), None, Some(PromotionPiece.Rook)))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-    pgn should include ("e7e8=R")
-  }
-
-  test("exportGame encodes promotion to Bishop as =B suffix") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R7), Square(File.E, Rank.R8), None, Some(PromotionPiece.Bishop)))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-    pgn should include ("e7e8=B")
-  }
-
-  test("exportGame encodes promotion to Knight as =N suffix") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R7), Square(File.E, Rank.R8), None, Some(PromotionPiece.Knight)))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-    pgn should include ("e7e8=N")
-  }
-
-  test("exportGame does not add suffix for normal moves") {
-    val history = GameHistory()
-      .addMove(HistoryMove(Square(File.E, Rank.R2), Square(File.E, Rank.R4), None, None))
-    val pgn = PgnExporter.exportGame(Map.empty, history)
-    pgn should include ("e2e4")
-    pgn should not include ("=")
-  }

modules/core/src/test/scala/de/nowchess/chess/notation/PgnParserTest.scala

@@ -1,451 +0,0 @@
-package de.nowchess.chess.notation
-
-import de.nowchess.api.board.*
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.logic.{GameHistory, HistoryMove, CastleSide}
-import de.nowchess.chess.notation.FenParser
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-
-class PgnParserTest extends AnyFunSuite with Matchers:
-
-  test("parse PGN headers only") {
-    val pgn = """[Event "Test Game"]
-[Site "Earth"]
-[Date "2026.03.28"]
-[White "Alice"]
-[Black "Bob"]
-[Result "1-0"]"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    game.get.headers("Event") shouldBe "Test Game"
-    game.get.headers("White") shouldBe "Alice"
-    game.get.headers("Result") shouldBe "1-0"
-    game.get.moves shouldBe List()
-  }
-
-  test("parse PGN simple game") {
-    val pgn = """[Event "Test"]
-[Site "?"]
-[Date "2026.03.28"]
-[White "A"]
-[Black "B"]
-[Result "*"]
-
-1. e4 e5 2. Nf3 Nc6 3. Bb5 a6
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    game.get.moves.length shouldBe 6
-    // e4: e2-e4
-    game.get.moves(0).from shouldBe Square(File.E, Rank.R2)
-    game.get.moves(0).to shouldBe Square(File.E, Rank.R4)
-  }
-
-  test("parse PGN move with capture") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-
-1. e4 e5 2. Nxe5
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    game.get.moves.length shouldBe 3
-    // Nxe5: knight captures on e5
-    game.get.moves(2).to shouldBe Square(File.E, Rank.R5)
-  }
-
-  test("parse PGN castling") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-
-1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. O-O
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    // O-O is kingside castling: king e1-g1
-    val lastMove = game.get.moves.last
-    lastMove.from shouldBe Square(File.E, Rank.R1)
-    lastMove.to shouldBe Square(File.G, Rank.R1)
-    lastMove.castleSide.isDefined shouldBe true
-  }
-
-  test("parse PGN empty moves") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-[Result "1-0"]
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    game.get.moves.length shouldBe 0
-  }
-
-  test("parse PGN black kingside castling O-O") {
-    // After e4 e5 Nf3 Nc6 Bc4 Bc5, black can castle kingside
-    val pgn = """[Event "Test"]
-
-1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. O-O O-O
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    val blackCastle = game.get.moves.last
-    blackCastle.castleSide shouldBe Some(CastleSide.Kingside)
-    blackCastle.from shouldBe Square(File.E, Rank.R8)
-    blackCastle.to shouldBe Square(File.G, Rank.R8)
-  }
-
-  test("parse PGN result tokens are skipped") {
-    // Result tokens like 1-0, 0-1, 1/2-1/2, * should be silently skipped
-    val pgn = """[Event "Test"]
-
-1. e4 e5 1-0
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    game.get.moves.length shouldBe 2
-  }
-
-  test("parseAlgebraicMove: unrecognised token returns None and is skipped") {
-    val board = Board.initial
-    val history = GameHistory.empty
-    // "zzz" is not valid algebraic notation
-    val result = PgnParser.parseAlgebraicMove("zzz", board, history, Color.White)
-    result shouldBe None
-  }
-
-  test("parseAlgebraicMove: piece moves use charToPieceType for N B R Q K") {
-    // Test that piece type characters are recognised
-    val board = Board.initial
-    val history = GameHistory.empty
-
-    // Nf3 - knight move
-    val nMove = PgnParser.parseAlgebraicMove("Nf3", board, history, Color.White)
-    nMove.isDefined shouldBe true
-    nMove.get.to shouldBe Square(File.F, Rank.R3)
-  }
-
-  test("parseAlgebraicMove: single char that is too short returns None") {
-    val board = Board.initial
-    val history = GameHistory.empty
-    // Single char that is not castling and cleaned length < 2
-    val result = PgnParser.parseAlgebraicMove("e", board, history, Color.White)
-    result shouldBe None
-  }
-
-  test("parse PGN with file disambiguation hint") {
-    // Use a position where two rooks can reach the same square to test file hint
-    // Rooks on a1 and h1, destination d1 - "Rad1" uses file 'a' to disambiguate
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val pieces: Map[Square, Piece] = Map(
-      Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.H, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val board = Board(pieces)
-    val history = GameHistory.empty
-
-    val result = PgnParser.parseAlgebraicMove("Rad1", board, history, Color.White)
-    result.isDefined shouldBe true
-    result.get.from shouldBe Square(File.A, Rank.R1)
-    result.get.to shouldBe Square(File.D, Rank.R1)
-  }
-
-  test("parse PGN with rank disambiguation hint") {
-    // Two rooks on a1 and a4 can reach a3 - "R1a3" uses rank '1' to disambiguate
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val pieces: Map[Square, Piece] = Map(
-      Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.A, Rank.R4) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val board = Board(pieces)
-    val history = GameHistory.empty
-
-    val result = PgnParser.parseAlgebraicMove("R1a3", board, history, Color.White)
-    result.isDefined shouldBe true
-    result.get.from shouldBe Square(File.A, Rank.R1)
-    result.get.to shouldBe Square(File.A, Rank.R3)
-  }
-
-  test("parseAlgebraicMove: charToPieceType covers all piece letters including B R Q K") {
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    // Bishop move
-    val piecesForBishop: Map[Square, Piece] = Map(
-      Square(File.C, Rank.R1) -> Piece(Color.White, PieceType.Bishop),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val boardBishop = Board(piecesForBishop)
-    val bResult = PgnParser.parseAlgebraicMove("Bd2", boardBishop, GameHistory.empty, Color.White)
-    bResult.isDefined shouldBe true
-
-    // Rook move
-    val piecesForRook: Map[Square, Piece] = Map(
-      Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val boardRook = Board(piecesForRook)
-    val rResult = PgnParser.parseAlgebraicMove("Ra4", boardRook, GameHistory.empty, Color.White)
-    rResult.isDefined shouldBe true
-
-    // Queen move
-    val piecesForQueen: Map[Square, Piece] = Map(
-      Square(File.D, Rank.R1) -> Piece(Color.White, PieceType.Queen),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val boardQueen = Board(piecesForQueen)
-    val qResult = PgnParser.parseAlgebraicMove("Qd4", boardQueen, GameHistory.empty, Color.White)
-    qResult.isDefined shouldBe true
-
-    // King move
-    val piecesForKing: Map[Square, Piece] = Map(
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val boardKing = Board(piecesForKing)
-    val kResult = PgnParser.parseAlgebraicMove("Ke2", boardKing, GameHistory.empty, Color.White)
-    kResult.isDefined shouldBe true
-  }
-
-  test("parse PGN queenside castling O-O-O") {
-    val pgn = """[Event "Test"]
-
-1. d4 d5 2. Nc3 Nc6 3. Bf4 Bf5 4. Qd2 Qd7 5. O-O-O
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    val lastMove = game.get.moves.last
-    lastMove.castleSide shouldBe Some(CastleSide.Queenside)
-    lastMove.from shouldBe Square(File.E, Rank.R1)
-    lastMove.to shouldBe Square(File.C, Rank.R1)
-  }
-
-  test("parse PGN black queenside castling O-O-O") {
-    // After sufficient moves, black castles queenside
-    val pgn = """[Event "Test"]
-
-1. d4 d5 2. Nc3 Nc6 3. Bf4 Bf5 4. Qd2 Qd7 5. O-O-O O-O-O
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    val lastMove = game.get.moves.last
-    lastMove.castleSide shouldBe Some(CastleSide.Queenside)
-    lastMove.from shouldBe Square(File.E, Rank.R8)
-    lastMove.to shouldBe Square(File.C, Rank.R8)
-  }
-
-  test("parse PGN with unrecognised token in move text is silently skipped") {
-    // "INVALID" is not valid PGN; it should be skipped and remaining moves parsed
-    val pgn = """[Event "Test"]
-
-1. e4 INVALID e5
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    // e4 parsed, INVALID skipped, e5 parsed
-    game.get.moves.length shouldBe 2
-  }
-
-  test("parseAlgebraicMove: file+rank disambiguation with piece letter") {
-    // "Rae1" notation: piece R, disambig "a" -> hint is "a", piece letter is uppercase first char of disambig
-    // But since disambig="a" which is not uppercase, the piece letter comes from clean.head
-    // Test "Rae1" style: R is clean.head uppercase, disambig "a" is the hint
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val pieces: Map[Square, Piece] = Map(
-      Square(File.A, Rank.R4) -> Piece(Color.White, PieceType.Rook),
-      Square(File.H, Rank.R4) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val board = Board(pieces)
-    val history = GameHistory.empty
-
-    // "Rae4" - Rook from a-file to e4; disambig = "a", clean.head = 'R' uppercase
-    val result = PgnParser.parseAlgebraicMove("Rae4", board, history, Color.White)
-    result.isDefined shouldBe true
-    result.get.from shouldBe Square(File.A, Rank.R4)
-    result.get.to shouldBe Square(File.E, Rank.R4)
-  }
-
-  test("parseAlgebraicMove: charToPieceType returns None for unknown character") {
-    // 'Z' is not a valid piece letter - the regex clean should return None
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val board = Board.initial
-    val history = GameHistory.empty
-
-    // "Ze4" - Z is not a valid piece, charToPieceType('Z') returns None
-    // The result will be None because requiredPieceType is None and filtering by None.forall = true
-    // so it finds any piece that can reach e4, but since clean="Ze4" -> destStr="e4", disambig="Z"
-    // disambig.head.isUpper so charToPieceType('Z') is called
-    val result = PgnParser.parseAlgebraicMove("Ze4", board, history, Color.White)
-    // With None piece type, forall(pt => ...) is vacuously true so any piece reaching e4 is candidate
-    // But there's no piece named Z so requiredPieceType=None, meaning any piece can match
-    // This tests that charToPieceType('Z') returns None without crashing
-    result shouldBe defined  // will find a pawn or whatever reaches e4
-  }
-
-  test("parseAlgebraicMove: uppercase dest-only notation hits clean.head.isUpper and charToPieceType unknown char") {
-    // "E4" - clean = "E4", disambig = "", clean.head = 'E' is upper, charToPieceType('E') returns None
-    // This exercises line 97 (else if clean.head.isUpper) and line 152 (case _ => None)
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val board = Board.initial
-    val history = GameHistory.empty
-    // 'E' is not a valid piece type but we still get a result since requiredPieceType is None
-    val result = PgnParser.parseAlgebraicMove("E4", board, history, Color.White)
-    // Result may be defined (pawn that can reach e4) or None; main goal is no crash and line coverage
-    result should not be null  // just verifies code path executes without exception
-  }
-
-  test("parseAlgebraicMove: rank disambiguation with digit outside 1-8 hits matchesHint else-true branch") {
-    // Build a board with a Rook that can be targeted with a disambiguation hint containing '9'
-    // hint = "9" → c = '9', not in a-h, not in 1-8, triggers else true
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val pieces: Map[Square, Piece] = Map(
-      Square(File.A, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.H, Rank.R1) -> Piece(Color.White, PieceType.Rook),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King)
-    )
-    val board = Board(pieces)
-    val history = GameHistory.empty
-
-    // "R9d1" - clean = "R9d1", destStr = "d1", disambig = "R9"
-    // disambig.head = 'R' is upper -> charToPieceType('R') = Rook, hint = "9"
-    // matchesHint called with hint "9" -> '9' not in a-h, not in 1-8 -> else true
-    val result = PgnParser.parseAlgebraicMove("R9d1", board, history, Color.White)
-    // Should find a rook (hint "9" matches everything)
-    result.isDefined shouldBe true
-    result.get.to shouldBe Square(File.D, Rank.R1)
-  }
-
-  test("parseAlgebraicMove preserves promotion to Queen in HistoryMove") {
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=Q", board, GameHistory.empty, Color.White)
-    result.isDefined should be (true)
-    result.get.promotionPiece should be (Some(PromotionPiece.Queen))
-    result.get.to should be (Square(File.E, Rank.R8))
-  }
-
-  test("parseAlgebraicMove preserves promotion to Rook") {
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=R", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Rook))
-  }
-
-  test("parseAlgebraicMove preserves promotion to Bishop") {
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=B", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Bishop))
-  }
-
-  test("parseAlgebraicMove preserves promotion to Knight") {
-    val board = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
-    val result = PgnParser.parseAlgebraicMove("e7e8=N", board, GameHistory.empty, Color.White)
-    result.get.promotionPiece should be (Some(PromotionPiece.Knight))
-  }
-
-  test("parsePgn applies promoted piece to board for subsequent moves") {
-    // Build a board with a white pawn on e7 plus the two kings
-    import de.nowchess.api.board.{Board, Square, File, Rank, Piece, Color, PieceType}
-    val pieces: Map[Square, Piece] = Map(
-      Square(File.E, Rank.R7) -> Piece(Color.White, PieceType.Pawn),
-      Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
-      Square(File.H, Rank.R1) -> Piece(Color.Black, PieceType.King)
-    )
-    val board = Board(pieces)
-    val move = PgnParser.parseAlgebraicMove("e7e8=Q", board, GameHistory.empty, Color.White)
-    move.isDefined should be (true)
-    move.get.promotionPiece should be (Some(PromotionPiece.Queen))
-    // After applying the promotion the square e8 should hold a White Queen
-    val (boardAfterPawnMove, _) = board.withMove(move.get.from, move.get.to)
-    val promotedBoard = boardAfterPawnMove.updated(move.get.to, Piece(Color.White, PieceType.Queen))
-    promotedBoard.pieceAt(Square(File.E, Rank.R8)) should be (Some(Piece(Color.White, PieceType.Queen)))
-  }
-
-  test("parsePgn with all four promotion piece types (Queen, Rook, Bishop, Knight) in sequence") {
-    // This test exercises lines 53-58 in PgnParser.parseMovesText which contain
-    // the pattern match over PromotionPiece for Queen, Rook, Bishop, Knight
-    val pgn = """[Event "Promotion Test"]
-[White "A"]
-[Black "B"]
-
-1. a2a3 h7h5 2. a3a4 h5h4 3. a4a5 h4h3 4. a5a6 h3h2 5. a6a7 h2h1=Q 6. a7a8=R 1-0
-"""
-    val game = PgnParser.parsePgn(pgn)
-
-    game.isDefined shouldBe true
-    // Move 10 is h2h1=Q (black pawn promotes to queen)
-    val blackPromotionToQ = game.get.moves(9)  // 0-indexed
-    blackPromotionToQ.promotionPiece shouldBe Some(PromotionPiece.Queen)
-
-    // Move 11 is a7a8=R (white pawn promotes to rook)
-    val whitePromotionToR = game.get.moves(10)
-    whitePromotionToR.promotionPiece shouldBe Some(PromotionPiece.Rook)
-  }
-
-  test("parseAlgebraicMove promotion with Rook through full PGN parse") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-
-1. a2a3 h7h6 2. a3a4 h6h5 3. a4a5 h5h4 4. a5a6 h4h3 5. a6a7 h3h2 6. a7a8=R
-"""
-    val game = PgnParser.parsePgn(pgn)
-    game.isDefined shouldBe true
-    val lastMove = game.get.moves.last
-    lastMove.promotionPiece shouldBe Some(PromotionPiece.Rook)
-  }
-
-  test("parseAlgebraicMove promotion with Bishop through full PGN parse") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-
-1. b2b3 h7h6 2. b3b4 h6h5 3. b4b5 h5h4 4. b5b6 h4h3 5. b6b7 h3h2 6. b7b8=B
-"""
-    val game = PgnParser.parsePgn(pgn)
-    game.isDefined shouldBe true
-    val lastMove = game.get.moves.last
-    lastMove.promotionPiece shouldBe Some(PromotionPiece.Bishop)
-  }
-
-  test("parseAlgebraicMove promotion with Knight through full PGN parse") {
-    val pgn = """[Event "Test"]
-[White "A"]
-[Black "B"]
-
-1. c2c3 h7h6 2. c3c4 h6h5 3. c4c5 h5h4 4. c5c6 h4h3 5. c6c7 h3h2 6. c7c8=N
-"""
-    val game = PgnParser.parsePgn(pgn)
-    game.isDefined shouldBe true
-    val lastMove = game.get.moves.last
-    lastMove.promotionPiece shouldBe Some(PromotionPiece.Knight)
-  }
-
-  test("extractPromotion returns None for invalid promotion letter") {
-    // Regex =([A-Z]) now captures any uppercase letter, so =X is matched but case _ => None fires
-    val result = PgnParser.extractPromotion("e7e8=X")
-    result shouldBe None
-  }
-
-  test("extractPromotion returns None when no promotion in notation") {
-    val result = PgnParser.extractPromotion("e7e8")
-    result shouldBe None
-  }

modules/core/src/test/scala/de/nowchess/chess/observer/ObservableThreadSafetyTest.scala

@@ -1,168 +0,0 @@
-package de.nowchess.chess.observer
-
-import de.nowchess.api.board.{Board, Color}
-import de.nowchess.chess.logic.GameHistory
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import scala.collection.mutable
-
-class ObservableThreadSafetyTest extends AnyFunSuite with Matchers:
-
-  private class TestObservable extends Observable:
-    def testNotifyObservers(event: GameEvent): Unit =
-      notifyObservers(event)
-
-  private class CountingObserver extends Observer:
-    @volatile private var eventCount = 0
-    @volatile private var lastEvent: Option[GameEvent] = None
-
-    def onGameEvent(event: GameEvent): Unit =
-      eventCount += 1
-      lastEvent = Some(event)
-
-  private def createTestEvent(): GameEvent =
-    BoardResetEvent(
-      board = Board.initial,
-      history = GameHistory.empty,
-      turn = Color.White
-    )
-
-  test("Observable is thread-safe for concurrent subscribe and notify"):
-    val observable = new TestObservable()
-    val testEvent = createTestEvent()
-    @volatile var raceConditionCaught = false
-
-    // Thread 1: repeatedly notifies observers with long iteration
-    val notifierThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500000 do
-            observable.testNotifyObservers(testEvent)
-        } catch {
-          case _: java.util.ConcurrentModificationException =>
-            raceConditionCaught = true
-        }
-      }
-    })
-
-    // Thread 2: rapidly subscribes/unsubscribes observers during notify
-    val subscriberThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500000 do
-            val obs = new CountingObserver()
-            observable.subscribe(obs)
-            observable.unsubscribe(obs)
-        } catch {
-          case _: java.util.ConcurrentModificationException =>
-            raceConditionCaught = true
-        }
-      }
-    })
-
-    notifierThread.start()
-    subscriberThread.start()
-    notifierThread.join()
-    subscriberThread.join()
-
-    raceConditionCaught shouldBe false
-
-  test("Observable is thread-safe for concurrent subscribe, unsubscribe, and notify"):
-    val observable = new TestObservable()
-    val testEvent = createTestEvent()
-    val exceptions = mutable.ListBuffer[Exception]()
-    val observers = mutable.ListBuffer[CountingObserver]()
-
-    // Pre-subscribe some observers
-    for _ <- 1 to 10 do
-      val obs = new CountingObserver()
-      observers += obs
-      observable.subscribe(obs)
-
-    // Thread 1: notifies observers
-    val notifierThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 5000 do
-            observable.testNotifyObservers(testEvent)
-        } catch {
-          case e: Exception => exceptions += e
-        }
-      }
-    })
-
-    // Thread 2: subscribes new observers
-    val subscriberThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 5000 do
-            val obs = new CountingObserver()
-            observable.subscribe(obs)
-        } catch {
-          case e: Exception => exceptions += e
-        }
-      }
-    })
-
-    // Thread 3: unsubscribes observers
-    val unsubscriberThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for i <- 1 to 5000 do
-            if observers.nonEmpty then
-              val obs = observers(i % observers.size)
-              observable.unsubscribe(obs)
-        } catch {
-          case e: Exception => exceptions += e
-        }
-      }
-    })
-
-    notifierThread.start()
-    subscriberThread.start()
-    unsubscriberThread.start()
-    notifierThread.join()
-    subscriberThread.join()
-    unsubscriberThread.join()
-
-    exceptions.isEmpty shouldBe true
-
-  test("Observable.observerCount is thread-safe during concurrent modifications"):
-    val observable = new TestObservable()
-    val exceptions = mutable.ListBuffer[Exception]()
-    val countResults = mutable.ListBuffer[Int]()
-
-    // Thread 1: subscribes observers
-    val subscriberThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            observable.subscribe(new CountingObserver())
-        } catch {
-          case e: Exception => exceptions += e
-        }
-      }
-    })
-
-    // Thread 2: reads observer count
-    val readerThread = new Thread(new Runnable {
-      def run(): Unit = {
-        try {
-          for _ <- 1 to 500 do
-            val count = observable.observerCount
-            countResults += count
-        } catch {
-          case e: Exception => exceptions += e
-        }
-      }
-    })
-
-    subscriberThread.start()
-    readerThread.start()
-    subscriberThread.join()
-    readerThread.join()
-
-    exceptions.isEmpty shouldBe true
-    // Count should never go backwards
-    for i <- 1 until countResults.size do
-      countResults(i) >= countResults(i - 1) shouldBe true

modules/core/versions.env

@@ -1,3 +0,0 @@
-MAJOR=0
-MINOR=5
-PATCH=0

modules/ui/build.gradle.kts

@@ -1,73 +0,0 @@
-plugins {
-    id("scala")
-    id("org.scoverage") version "8.1"
-    application
-}
-
-group = "de.nowchess"
-version = "1.0-SNAPSHOT"
-
-@Suppress("UNCHECKED_CAST")
-val versions = rootProject.extra["VERSIONS"] as Map<String, String>
-
-repositories {
-    mavenCentral()
-}
-
-scala {
-    scalaVersion = versions["SCALA3"]!!
-}
-
-scoverage {
-    scoverageVersion.set(versions["SCOVERAGE"]!!)
-}
-
-application {
-    mainClass.set("de.nowchess.ui.Main")
-}
-
-tasks.withType<ScalaCompile> {
-    scalaCompileOptions.additionalParameters = listOf("-encoding", "UTF-8")
-}
-
-tasks.named<JavaExec>("run") {
-    jvmArgs("-Dfile.encoding=UTF-8", "-Dstdout.encoding=UTF-8", "-Dstderr.encoding=UTF-8")
-    standardInput = System.`in`
-}
-
-dependencies {
-
-    implementation("org.scala-lang:scala3-compiler_3") {
-        version {
-            strictly(versions["SCALA3"]!!)
-        }
-    }
-    implementation("org.scala-lang:scala3-library_3") {
-        version {
-            strictly(versions["SCALA3"]!!)
-        }
-    }
-
-    implementation(project(":modules:core"))
-    implementation(project(":modules:api"))
-
-    testImplementation(platform("org.junit:junit-bom:5.13.4"))
-    testImplementation("org.junit.jupiter:junit-jupiter")
-    testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
-    testImplementation("co.helmethair:scalatest-junit-runner:${versions["SCALATEST_JUNIT"]!!}")
-
-    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
-}
-
-tasks.test {
-    useJUnitPlatform {
-        includeEngines("scalatest")
-        testLogging {
-            events("passed", "skipped", "failed")
-        }
-    }
-    finalizedBy(tasks.reportScoverage)
-}
-tasks.reportScoverage {
-    dependsOn(tasks.test)
-}

modules/ui/src/main/scala/de/nowchess/ui/Main.scala

@@ -1,15 +0,0 @@
-package de.nowchess.ui
-
-import de.nowchess.chess.engine.GameEngine
-import de.nowchess.ui.terminal.TerminalUI
-
-/** Application entry point - starts the Terminal UI for the chess game. */
-object Main:
-  def main(args: Array[String]): Unit =
-    // Create the core game engine (single source of truth)
-    val engine = new GameEngine()
-
-    // Create and start the terminal UI
-    val tui = new TerminalUI(engine)
-    tui.start()
-

modules/ui/src/main/scala/de/nowchess/ui/terminal/TerminalUI.scala

@@ -1,93 +0,0 @@
-package de.nowchess.ui.terminal
-
-import scala.io.StdIn
-import de.nowchess.api.move.PromotionPiece
-import de.nowchess.chess.engine.GameEngine
-import de.nowchess.chess.observer.{Observer, GameEvent, *}
-import de.nowchess.chess.view.Renderer
-
-/** Terminal UI that implements Observer pattern.
- *  Subscribes to GameEngine and receives state change events.
- *  Handles all I/O and user interaction in the terminal.
- */
-class TerminalUI(engine: GameEngine) extends Observer:
-  private var running = true
-  private var awaitingPromotion = false
-
-  /** Called by GameEngine whenever a game event occurs. */
-  override def onGameEvent(event: GameEvent): Unit =
-    event match
-      case e: MoveExecutedEvent =>
-        println()
-        print(Renderer.render(e.board))
-        e.capturedPiece.foreach: cap =>
-          println(s"Captured: $cap on ${e.toSquare}")
-        printPrompt(e.turn)
-
-      case e: CheckDetectedEvent =>
-        println(s"${e.turn.label} is in check!")
-
-      case e: CheckmateEvent =>
-        println(s"Checkmate! ${e.winner.label} wins.")
-        println()
-        print(Renderer.render(e.board))
-
-      case e: StalemateEvent =>
-        println("Stalemate! The game is a draw.")
-        println()
-        print(Renderer.render(e.board))
-
-      case e: InvalidMoveEvent =>
-        println(s"⚠️  ${e.reason}")
-
-      case e: BoardResetEvent =>
-        println("Board has been reset to initial position.")
-        println()
-        print(Renderer.render(e.board))
-        printPrompt(e.turn)
-
-      case _: PromotionRequiredEvent =>
-        println("Promote to: q=Queen, r=Rook, b=Bishop, n=Knight")
-        synchronized { awaitingPromotion = true }
-
-  /** Start the terminal UI game loop. */
-  def start(): Unit =
-    // Register as observer
-    engine.subscribe(this)
-
-    // Show initial board
-    println()
-    print(Renderer.render(engine.board))
-    printPrompt(engine.turn)
-
-    // Game loop
-    while running do
-      val input = Option(StdIn.readLine()).getOrElse("quit").trim
-      synchronized {
-        if awaitingPromotion then
-          input.toLowerCase match
-            case "q" => awaitingPromotion = false; engine.completePromotion(PromotionPiece.Queen)
-            case "r" => awaitingPromotion = false; engine.completePromotion(PromotionPiece.Rook)
-            case "b" => awaitingPromotion = false; engine.completePromotion(PromotionPiece.Bishop)
-            case "n" => awaitingPromotion = false; engine.completePromotion(PromotionPiece.Knight)
-            case _ =>
-              println("Invalid choice. Enter q, r, b, or n.")
-              println("Promote to: q=Queen, r=Rook, b=Bishop, n=Knight")
-        else
-          input.toLowerCase match
-            case "quit" | "q" =>
-              running = false
-              println("Game over. Goodbye!")
-            case "" =>
-              printPrompt(engine.turn)
-            case _ =>
-              engine.processUserInput(input)
-      }
-
-    // Unsubscribe when done
-    engine.unsubscribe(this)
-
-  private def printPrompt(turn: de.nowchess.api.board.Color): Unit =
-    val undoHint = if engine.canUndo then " [undo]" else ""
-    val redoHint = if engine.canRedo then " [redo]" else ""
-    print(s"${turn.label}'s turn. Enter move (or 'quit'/'q' to exit)$undoHint$redoHint: ")

modules/ui/src/test/scala/de/nowchess/ui/MainTest.scala

@@ -1,22 +0,0 @@
-package de.nowchess.ui
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
-
-class MainTest extends AnyFunSuite with Matchers {
-
-  test("main should execute and quit immediately when fed 'quit'") {
-    val in = new ByteArrayInputStream("quit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        Main.main(Array.empty)
-      }
-    }
-    
-    val output = out.toString
-    output should include ("Game over. Goodbye!")
-  }
-}

modules/ui/src/test/scala/de/nowchess/ui/terminal/TerminalUITest.scala

@@ -1,327 +0,0 @@
-package de.nowchess.ui.terminal
-
-import org.scalatest.funsuite.AnyFunSuite
-import org.scalatest.matchers.should.Matchers
-import java.io.{ByteArrayInputStream, ByteArrayOutputStream}
-import de.nowchess.chess.engine.GameEngine
-import de.nowchess.chess.observer.*
-import de.nowchess.api.board.{Board, Color, File, Rank, Square}
-import de.nowchess.chess.logic.GameHistory
-
-class TerminalUITest extends AnyFunSuite with Matchers {
-
-  test("TerminalUI should start, print initial state, and correctly respond to 'q'") {
-    val in = new ByteArrayInputStream("q\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("White's turn.")
-    output should include("Game over. Goodbye!")
-  }
-
-  test("TerminalUI should ignore empty inputs and re-print prompt") {
-    val in = new ByteArrayInputStream("\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    // Prompt appears three times: Initial, after empty, on exit.
-    output.split("White's turn.").length should be > 2
-  }
-
-  test("TerminalUI should explicitly handle empty input by re-prompting") {
-    val in = new ByteArrayInputStream("\n\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    // With two empty inputs, prompt should appear at least 4 times:
-    // 1. Initial board display
-    // 2. After first empty input
-    // 3. After second empty input
-    // 4. Before quit
-    val promptCount = output.split("White's turn.").length
-    promptCount should be >= 4
-    output should include("Game over. Goodbye!")
-  }
-
-  test("TerminalUI printPrompt should include undo and redo hints if engine returns true") {
-    val in = new ByteArrayInputStream("\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine() {
-      // Stub engine to force undo/redo to true
-      override def canUndo: Boolean = true
-      override def canRedo: Boolean = true
-    }
-    
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("[undo]")
-    output should include("[redo]")
-  }
-
-  test("TerminalUI onGameEvent should properly format InvalidMoveEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(InvalidMoveEvent(Board(Map.empty), GameHistory(), Color.Black, "Invalid move format"))
-    }
-
-    out.toString should include("⚠️")
-    out.toString should include("Invalid move format")
-  }
-
-  test("TerminalUI onGameEvent should properly format CheckDetectedEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(CheckDetectedEvent(Board(Map.empty), GameHistory(), Color.Black))
-    }
-
-    out.toString should include("Black is in check!")
-  }
-
-  test("TerminalUI onGameEvent should properly format CheckmateEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(CheckmateEvent(Board(Map.empty), GameHistory(), Color.Black, Color.White))
-    }
-
-    val ostr = out.toString
-    ostr should include("Checkmate! White wins.")
-  }
-
-  test("TerminalUI onGameEvent should properly format StalemateEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(StalemateEvent(Board(Map.empty), GameHistory(), Color.Black))
-    }
-
-    out.toString should include("Stalemate! The game is a draw.")
-  }
-
-  test("TerminalUI onGameEvent should properly format BoardResetEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(BoardResetEvent(Board(Map.empty), GameHistory(), Color.White))
-    }
-
-    out.toString should include("Board has been reset to initial position.")
-  }
-
-  test("TerminalUI onGameEvent should properly format MoveExecutedEvent with capturing piece") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(MoveExecutedEvent(Board(Map.empty), GameHistory(), Color.Black, "A1", "A8", Some("Knight(White)")))
-    }
-
-    out.toString should include("Captured: Knight(White) on A8") // Depending on how piece/coord serialize
-  }
-
-  test("TerminalUI processes valid move input via processUserInput") {
-    val in = new ByteArrayInputStream("e2e4\nq\n".getBytes)
-    val out = new ByteArrayOutputStream()
-
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    val output = out.toString
-    output should include("White's turn.")
-    output should include("Game over. Goodbye!")
-    // The move should have been processed and the board displayed
-    engine.turn shouldBe Color.Black
-  }
-
-  test("TerminalUI shows promotion prompt on PromotionRequiredEvent") {
-    val out = new ByteArrayOutputStream()
-    val engine = new GameEngine()
-    val ui = new TerminalUI(engine)
-
-    Console.withOut(out) {
-      ui.onGameEvent(PromotionRequiredEvent(
-        Board(Map.empty), GameHistory(), Color.White,
-        Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-      ))
-    }
-
-    out.toString should include("Promote to")
-  }
-
-  test("TerminalUI routes promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nq\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Queen))
-    out.toString should include("Promote to")
-  }
-
-  test("TerminalUI re-prompts on invalid promotion choice") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    // "x" is invalid, then "r" for rook
-    val in = new ByteArrayInputStream("e7e8\nx\nr\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Rook))
-    out.toString should include("Invalid")
-  }
-
-  test("TerminalUI routes Bishop promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nb\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Bishop))
-  }
-
-  test("TerminalUI routes Knight promotion choice to engine.completePromotion") {
-    import de.nowchess.api.move.PromotionPiece
-
-    var capturedPiece: Option[PromotionPiece] = None
-
-    val engine = new GameEngine() {
-      override def processUserInput(rawInput: String): Unit =
-        if rawInput.trim == "e7e8" then
-          notifyObservers(PromotionRequiredEvent(
-            Board(Map.empty), GameHistory.empty, Color.White,
-            Square(File.E, Rank.R7), Square(File.E, Rank.R8)
-          ))
-      override def completePromotion(piece: PromotionPiece): Unit =
-        capturedPiece = Some(piece)
-        notifyObservers(MoveExecutedEvent(Board(Map.empty), GameHistory.empty, Color.Black, "e7", "e8", None))
-    }
-
-    val in = new ByteArrayInputStream("e7e8\nn\nquit\n".getBytes)
-    val out = new ByteArrayOutputStream()
-    val ui = new TerminalUI(engine)
-
-    Console.withIn(in) {
-      Console.withOut(out) {
-        ui.start()
-      }
-    }
-
-    capturedPiece should be(Some(PromotionPiece.Knight))
-  }
-}

settings.gradle.kts

@@ -1,2 +1,2 @@
 rootProject.name = "NowChessSystems"
-include("modules:core", "modules:api", "modules:ui")
+include("modules:core", "modules:api")