refactor: NCS-8 removed Context and replaced it with History (#6)

Reviewed-on: #6

.claude/memory/MEMORY.md

@@ -0,0 +1,9 @@
+# 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

@@ -0,0 +1,16 @@
+---
+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

@@ -0,0 +1,51 @@
+---
+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

@@ -0,0 +1,48 @@
+---
+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

@@ -0,0 +1,55 @@
+---
+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

CLAUDE.md

@@ -3,6 +3,10 @@
 ## Stack
 Scala 3.5.x · Quarkus + quarkus-scala3 · Hibernate/Jakarta · Lanterna TUI · K8s + ArgoCD + Kargo · Frontend TBD (Vite/React/Angular/Vue)
 
+### Memory
+
+Your memory is saved under .claude/memory/MEMORY.md.
+
 ## Structure
 ```
 build.gradle.kts / settings.gradle.kts   # root; include(":modules:<svc>") per service

modules/api/CHANGELOG.md

@@ -0,0 +1,2 @@
+##  (2026-03-27)
+##  (2026-03-28)

modules/api/build.gradle.kts

@@ -49,9 +49,10 @@ 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

@@ -8,10 +8,12 @@ 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 updated  = b.removed(from).updated(to, b(from))
-      (updated, captured)
+      val updatedBoard = b.removed(from).updated(to, b(from))
+      (updatedBoard, captured)
     def pieces: Map[Square, Piece] = b
 
   val initial: Board =

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

@@ -0,0 +1,122 @@
+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

@@ -0,0 +1,22 @@
+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

@@ -0,0 +1,60 @@
+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

@@ -0,0 +1,30 @@
+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

@@ -0,0 +1,62 @@
+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

@@ -0,0 +1,77 @@
+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

@@ -0,0 +1,56 @@
+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

@@ -0,0 +1,23 @@
+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

@@ -0,0 +1,62 @@
+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

@@ -0,0 +1,3 @@
+MAJOR=0
+MINOR=0
+PATCH=2

modules/core/CHANGELOG.md

@@ -0,0 +1,30 @@
+##  (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))

modules/core/build.gradle.kts

@@ -52,9 +52,10 @@ 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

@@ -1,11 +1,12 @@
 package de.nowchess.chess
 
+import de.nowchess.api.board.Board
 import de.nowchess.api.board.Color
 import de.nowchess.chess.controller.GameController
-import de.nowchess.chess.logic.GameContext
+import de.nowchess.chess.logic.GameHistory
 
 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)
+    GameController.gameLoop(Board.initial, GameHistory.empty, Color.White)
 }

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

@@ -2,8 +2,7 @@ package de.nowchess.chess.controller
 
 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.logic.*
 import de.nowchess.chess.view.Renderer
 
 // ---------------------------------------------------------------------------
@@ -17,8 +16,8 @@ object MoveResult:
   case object NoPiece                                                                   extends MoveResult
   case object WrongColor                                                                extends MoveResult
   case object IllegalMove                                                               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  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  Checkmate(winner: Color)                                                  extends MoveResult
   case object Stalemate                                                                 extends MoveResult
 
@@ -31,7 +30,7 @@ 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(ctx: GameContext, turn: Color, raw: String): MoveResult =
+  def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
     raw.trim match
       case "quit" | "q" =>
         MoveResult.Quit
@@ -40,97 +39,67 @@ object GameController:
           case None =>
             MoveResult.InvalidFormat(trimmed)
           case Some((from, to)) =>
-            ctx.board.pieceAt(from) match
+            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
+                if !MoveValidator.isLegal(board, history, from, to) then
                   MoveResult.IllegalMove
                 else
-                  val castleOpt = if MoveValidator.isCastle(ctx.board, from, to)
+                  val castleOpt = if MoveValidator.isCastle(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 Some(side) => (board.withCastle(turn, side), None)
+                    case None       => board.withMove(from, to)
+                  val newHistory = history.addMove(from, to, castleOpt)
+                  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
 
-  private def applyRightsRevocation(
-    ctx: GameContext,
-    turn: Color,
-    from: Square,
-    to: Square,
-    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))
-
-    // 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
-
-    // 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
-
   /** 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 =
+  def gameLoop(board: Board, history: GameHistory, turn: Color): Unit =
     println()
-    print(Renderer.render(ctx.board))
+    print(Renderer.render(board))
     println(s"${turn.label}'s turn. Enter move: ")
     val input = Option(StdIn.readLine()).getOrElse("quit").trim
-    processMove(ctx, turn, input) match
+    processMove(board, history, turn, input) match
       case MoveResult.Quit =>
         println("Game over. Goodbye!")
       case MoveResult.InvalidFormat(raw) =>
         println(s"Invalid move format '$raw'. Use coordinate notation, e.g. e2e4.")
-        gameLoop(ctx, turn)
+        gameLoop(board, history, turn)
       case MoveResult.NoPiece =>
         println(s"No piece on ${Parser.parseMove(input).map(_._1).fold("?")(_.toString)}.")
-        gameLoop(ctx, turn)
+        gameLoop(board, history, turn)
       case MoveResult.WrongColor =>
         println(s"That is not your piece.")
-        gameLoop(ctx, turn)
+        gameLoop(board, history, turn)
       case MoveResult.IllegalMove =>
         println(s"Illegal move.")
-        gameLoop(ctx, turn)
-      case MoveResult.Moved(newCtx, captured, newTurn) =>
+        gameLoop(board, history, turn)
+      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
         val prevTurn = newTurn.opposite
         captured.foreach: cap =>
           val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
           println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
-        gameLoop(newCtx, newTurn)
-      case MoveResult.MovedInCheck(newCtx, captured, newTurn) =>
+        gameLoop(newBoard, newHistory, newTurn)
+      case MoveResult.MovedInCheck(newBoard, newHistory, captured, newTurn) =>
         val prevTurn = newTurn.opposite
         captured.foreach: cap =>
           val toSq = Parser.parseMove(input).map(_._2).fold("?")(_.toString)
           println(s"${prevTurn.label} captures ${cap.color.label} ${cap.pieceType.label} on $toSq")
         println(s"${newTurn.label} is in check!")
-        gameLoop(newCtx, newTurn)
+        gameLoop(newBoard, newHistory, newTurn)
       case MoveResult.Checkmate(winner) =>
         println(s"Checkmate! ${winner.label} wins.")
-        gameLoop(GameContext.initial, Color.White)
+        gameLoop(Board.initial, GameHistory.empty, Color.White)
       case MoveResult.Stalemate =>
         println("Stalemate! The game is a draw.")
-        gameLoop(GameContext.initial, Color.White)
+        gameLoop(Board.initial, GameHistory.empty, Color.White)

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

@@ -0,0 +1,23 @@
+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

@@ -0,0 +1,31 @@
+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/GameContext.scala

@@ -1,47 +0,0 @@
-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

@@ -0,0 +1,24 @@
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.Square
+
+/** 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]
+)
+
+/** 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]): GameHistory =
+    addMove(HistoryMove(from, to, castleSide))
+
+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.GameContext
+import de.nowchess.chess.logic.GameHistory
 
 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(ctx: GameContext, color: Color): Set[(Square, Square)] =
-    ctx.board.pieces
+  def legalMoves(board: Board, history: GameHistory, color: Color): Set[(Square, Square)] =
+    board.pieces
       .collect { case (from, piece) if piece.color == color => from }
       .flatMap { from =>
-        MoveValidator.legalTargets(ctx, from)           // context-aware: includes castling
+        MoveValidator.legalTargets(board, history, from)           // context-aware: includes castling
           .filter { to =>
             val newBoard =
-              if MoveValidator.isCastle(ctx.board, from, to) then
-                ctx.board.withCastle(color, MoveValidator.castleSide(from, to))
+              if MoveValidator.isCastle(board, from, to) then
+                board.withCastle(color, MoveValidator.castleSide(from, to))
               else
-                ctx.board.withMove(from, to)._1
+                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(ctx: GameContext, color: Color): PositionStatus =
-    val moves   = legalMoves(ctx, color)
-    val inCheck = isInCheck(ctx.board, color)
+  def gameStatus(board: Board, history: GameHistory, color: Color): PositionStatus =
+    val moves   = legalMoves(board, history, 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

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.{GameContext, CastleSide}
+import de.nowchess.chess.logic.{CastleSide, GameHistory}
 
 object MoveValidator:
 
@@ -126,37 +126,37 @@ object MoveValidator:
   def castleSide(from: Square, to: Square): CastleSide =
     if to.file.ordinal > from.file.ordinal then CastleSide.Kingside else CastleSide.Queenside
 
-  def castlingTargets(ctx: GameContext, color: Color): Set[Square] =
-    val rights = ctx.castlingFor(color)
+  def castlingTargets(board: Board, history: GameHistory, color: Color): Set[Square] =
+    val rights = CastlingRightsCalculator.deriveCastlingRights(history, color)
     val rank   = if color == Color.White then Rank.R1 else Rank.R8
     val kingSq = Square(File.E, rank)
     val enemy  = color.opposite
 
-    if !ctx.board.pieceAt(kingSq).contains(Piece(color, PieceType.King)) ||
-       GameRules.isInCheck(ctx.board, color) then Set.empty
+    if !board.pieceAt(kingSq).contains(Piece(color, PieceType.King)) ||
+       GameRules.isInCheck(board, color) then Set.empty
     else
       val kingsideSq = Option.when(
         rights.kingSide &&
-        ctx.board.pieceAt(Square(File.H, rank)).contains(Piece(color, PieceType.Rook)) &&
-        List(Square(File.F, rank), Square(File.G, rank)).forall(s => ctx.board.pieceAt(s).isEmpty) &&
-        !List(Square(File.F, rank), Square(File.G, rank)).exists(s => isAttackedBy(ctx.board, s, enemy))
+        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))
 
       val queensideSq = Option.when(
         rights.queenSide &&
-        ctx.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 => ctx.board.pieceAt(s).isEmpty) &&
-        !List(Square(File.D, rank), Square(File.C, rank)).exists(s => isAttackedBy(ctx.board, s, enemy))
+        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))
 
       kingsideSq.toSet ++ queensideSq.toSet
 
-  def legalTargets(ctx: GameContext, from: Square): Set[Square] =
-    ctx.board.pieceAt(from) match
+  def legalTargets(board: Board, history: GameHistory, from: Square): Set[Square] =
+    board.pieceAt(from) match
       case Some(piece) if piece.pieceType == PieceType.King =>
-        legalTargets(ctx.board, from) ++ castlingTargets(ctx, piece.color)
+        legalTargets(board, from) ++ castlingTargets(board, history, piece.color)
       case _ =>
-        legalTargets(ctx.board, from)
+        legalTargets(board, from)
 
-  def isLegal(ctx: GameContext, from: Square, to: Square): Boolean =
-    legalTargets(ctx, from).contains(to)
+  def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
+    legalTargets(board, history, from).contains(to)

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

@@ -2,7 +2,7 @@ package de.nowchess.chess.controller
 
 import de.nowchess.api.board.*
 import de.nowchess.api.game.CastlingRights
-import de.nowchess.chess.logic.{GameContext, CastleSide}
+import de.nowchess.chess.logic.{CastleSide, GameHistory}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -11,54 +11,61 @@ import java.io.ByteArrayInputStream
 class GameControllerTest extends AnyFunSuite with Matchers:
 
   private def sq(f: File, r: Rank): Square = Square(f, r)
-  private val initial = GameContext.initial
+  private def processMove(board: Board, history: GameHistory, turn: Color, raw: String): MoveResult =
+    GameController.processMove(board, history, turn, raw)
+
+  private def gameLoop(board: Board, history: GameHistory, turn: Color): Unit =
+    GameController.gameLoop(board, history, turn)
+
+  private def castlingRights(history: GameHistory, color: Color): CastlingRights =
+    de.nowchess.chess.logic.CastlingRightsCalculator.deriveCastlingRights(history, color)
 
   // ──── processMove ────────────────────────────────────────────────────
 
   test("processMove: 'quit' input returns Quit"):
-    GameController.processMove(initial, Color.White, "quit") shouldBe MoveResult.Quit
+    processMove(Board.initial, GameHistory.empty, Color.White, "quit") shouldBe MoveResult.Quit
 
   test("processMove: 'q' input returns Quit"):
-    GameController.processMove(initial, Color.White, "q") shouldBe MoveResult.Quit
+    processMove(Board.initial, GameHistory.empty, Color.White, "q") shouldBe MoveResult.Quit
 
   test("processMove: quit with surrounding whitespace returns Quit"):
-    GameController.processMove(initial, Color.White, "  quit  ") shouldBe MoveResult.Quit
+    processMove(Board.initial, GameHistory.empty, Color.White, "  quit  ") shouldBe MoveResult.Quit
 
   test("processMove: unparseable input returns InvalidFormat"):
-    GameController.processMove(initial, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
+    processMove(Board.initial, GameHistory.empty, Color.White, "xyz") shouldBe MoveResult.InvalidFormat("xyz")
 
   test("processMove: valid format but empty square returns NoPiece"):
     // E3 is empty in the initial position
-    GameController.processMove(initial, Color.White, "e3e4") shouldBe MoveResult.NoPiece
+    processMove(Board.initial, GameHistory.empty, Color.White, "e3e4") shouldBe MoveResult.NoPiece
 
   test("processMove: piece of wrong color returns WrongColor"):
     // E7 has a Black pawn; it is White's turn
-    GameController.processMove(initial, Color.White, "e7e6") shouldBe MoveResult.WrongColor
+    processMove(Board.initial, GameHistory.empty, Color.White, "e7e6") shouldBe MoveResult.WrongColor
 
   test("processMove: geometrically illegal move returns IllegalMove"):
     // White pawn at E2 cannot jump three squares to E5
-    GameController.processMove(initial, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
+    processMove(Board.initial, GameHistory.empty, Color.White, "e2e5") shouldBe MoveResult.IllegalMove
 
   test("processMove: legal pawn move returns Moved with updated board and flipped turn"):
-    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
+    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
         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 captureCtx = GameContext(Board(Map(
+    val board = 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) =>
+    ))
+    processMove(board, GameHistory.empty, Color.White, "e5d6") match
+      case MoveResult.Moved(newBoard, newHistory, captured, newTurn) =>
         captured shouldBe Some(Piece.BlackPawn)
-        newCtx.board.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
+        newBoard.pieceAt(sq(File.D, Rank.R6)) shouldBe Some(Piece.WhitePawn)
         newTurn shouldBe Color.Black
       case other => fail(s"Expected Moved, got $other")
 
@@ -70,33 +77,33 @@ class GameControllerTest extends AnyFunSuite with Matchers:
 
   test("gameLoop: 'quit' exits cleanly without exception"):
     withInput("quit\n"):
-      GameController.gameLoop(GameContext.initial, Color.White)
+      gameLoop(Board.initial, GameHistory.empty, Color.White)
 
   test("gameLoop: EOF (null readLine) exits via quit fallback"):
     withInput(""):
-      GameController.gameLoop(GameContext.initial, Color.White)
+      gameLoop(Board.initial, GameHistory.empty, Color.White)
 
   test("gameLoop: invalid format prints message and recurses until quit"):
     withInput("badmove\nquit\n"):
-      GameController.gameLoop(GameContext.initial, Color.White)
+      gameLoop(Board.initial, GameHistory.empty, 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)
+      gameLoop(Board.initial, GameHistory.empty, 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)
+      gameLoop(Board.initial, GameHistory.empty, Color.White)
 
   test("gameLoop: IllegalMove prints message and recurses until quit"):
     withInput("e2e5\nquit\n"):
-      GameController.gameLoop(GameContext.initial, Color.White)
+      gameLoop(Board.initial, GameHistory.empty, Color.White)
 
   test("gameLoop: legal non-capture move recurses with new board then quits"):
     withInput("e2e4\nquit\n"):
-      GameController.gameLoop(GameContext.initial, Color.White)
+      gameLoop(Board.initial, GameHistory.empty, Color.White)
 
   test("gameLoop: capture move prints capture message then recurses and quits"):
     val captureBoard = Board(Map(
@@ -106,7 +113,7 @@ class GameControllerTest extends AnyFunSuite with Matchers:
       sq(File.H, Rank.R8) -> Piece.WhiteKing
     ))
     withInput("e5d6\nquit\n"):
-      GameController.gameLoop(GameContext(captureBoard), Color.White)
+      gameLoop(captureBoard, GameHistory.empty, Color.White)
 
   // ──── helpers ────────────────────────────────────────────────────────
 
@@ -120,37 +127,37 @@ class GameControllerTest extends AnyFunSuite with Matchers:
   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 ctx = GameContext(Board(Map(
+    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
-    )))
-    GameController.processMove(ctx, Color.White, "a1a8") match
-      case MoveResult.MovedInCheck(_, _, newTurn) => newTurn shouldBe Color.Black
+    ))
+    processMove(b, GameHistory.empty, 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 ctx = GameContext(Board(Map(
+    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(ctx, Color.White, "a1h8") match
+    ))
+    processMove(b, GameHistory.empty, 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(
+    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(ctx, Color.White, "b1b6") match
+    ))
+    processMove(b, GameHistory.empty, Color.White, "b1b6") match
       case MoveResult.Stalemate => succeed
       case other => fail(s"Expected Stalemate, got $other")
 
@@ -165,7 +172,7 @@ class GameControllerTest extends AnyFunSuite with Matchers:
     ))
     val output = captureOutput:
       withInput("a1h8\nquit\n"):
-        GameController.gameLoop(GameContext(b), Color.White)
+        gameLoop(b, GameHistory.empty, Color.White)
     output should include("Checkmate! White wins.")
 
   test("gameLoop: stalemate prints draw message and resets to new game"):
@@ -176,7 +183,7 @@ class GameControllerTest extends AnyFunSuite with Matchers:
     ))
     val output = captureOutput:
       withInput("b1b6\nquit\n"):
-        GameController.gameLoop(GameContext(b), Color.White)
+        gameLoop(b, GameHistory.empty, Color.White)
     output should include("Stalemate! The game is a draw.")
 
   test("gameLoop: MovedInCheck without capture prints check message"):
@@ -187,7 +194,7 @@ class GameControllerTest extends AnyFunSuite with Matchers:
     ))
     val output = captureOutput:
       withInput("a1a8\nquit\n"):
-        GameController.gameLoop(GameContext(b), Color.White)
+        gameLoop(b, GameHistory.empty, Color.White)
     output should include("Black is in check!")
 
   test("gameLoop: MovedInCheck with capture prints both capture and check message"):
@@ -200,208 +207,161 @@ class GameControllerTest extends AnyFunSuite with Matchers:
     ))
     val output = captureOutput:
       withInput("a1a8\nquit\n"):
-        GameController.gameLoop(GameContext(b), Color.White)
+        gameLoop(b, GameHistory.empty, 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 ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      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
+      ))
+    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
         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 ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.A, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      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)
+      ))
+    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)
       case other => fail(s"Expected Moved, got $other")
 
   // ──── rights revocation ──────────────────────────────────────────────
 
   test("processMove: e1g1 revokes both white castling rights"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      whiteCastling = CastlingRights.Both,
-      blackCastling = CastlingRights.None
-    )
-    GameController.processMove(ctx, Color.White, "e1g1") match
-      case MoveResult.Moved(newCtx, _, _) =>
-        newCtx.whiteCastling shouldBe CastlingRights.None
+      ))
+    processMove(b, GameHistory.empty, Color.White, "e1g1") match
+      case MoveResult.Moved(_, newHistory, _, _) =>
+        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: moving rook from h1 revokes white kingside right"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      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
+      ))
+    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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving king from e1 revokes both white rights"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      whiteCastling = CastlingRights.Both,
-      blackCastling = CastlingRights.None
-    )
-    GameController.processMove(ctx, Color.White, "e1e2") match
-      case MoveResult.Moved(newCtx, _, _) =>
-        newCtx.whiteCastling shouldBe CastlingRights.None
+      ))
+    processMove(b, GameHistory.empty, Color.White, "e1e2") match
+      case MoveResult.Moved(_, newHistory, _, _) =>
+        castlingRights(newHistory, Color.White) shouldBe CastlingRights.None
       case other => fail(s"Expected Moved, got $other")
 
   test("processMove: enemy capture on h1 revokes white kingside right"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = 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
-      )),
-      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
+      ))
+    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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: castle attempt when rights revoked returns IllegalMove"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      whiteCastling = CastlingRights.None,
-      blackCastling = CastlingRights.None
-    )
-    GameController.processMove(ctx, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
+      ))
+    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
 
   test("processMove: castle attempt when rook not on home square returns IllegalMove"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.G, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      )),
-      whiteCastling = CastlingRights.Both,
-      blackCastling = CastlingRights.None
-    )
-    GameController.processMove(ctx, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
+      ))
+    processMove(b, GameHistory.empty, Color.White, "e1g1") shouldBe MoveResult.IllegalMove
 
   test("processMove: moving king from e8 revokes both black rights"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.H, Rank.R1) -> Piece.WhiteKing
-      )),
-      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
+      ))
+    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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving rook from a8 revokes black queenside right"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.A, Rank.R8) -> Piece.BlackRook,
         sq(File.H, Rank.R1) -> Piece.WhiteKing
-      )),
-      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
+      ))
+    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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: moving rook from h8 revokes black kingside right"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = Board(Map(
         sq(File.E, Rank.R8) -> Piece.BlackKing,
         sq(File.H, Rank.R8) -> Piece.BlackRook,
-        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
+        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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")
 
   test("processMove: enemy capture on a1 revokes white queenside right"):
-    val ctx = GameContext(
-      board = Board(Map(
+    val b = 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
-      )),
-      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
+      ))
+    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
       case other => fail(s"Expected Moved or MovedInCheck, got $other")

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

@@ -0,0 +1,70 @@
+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/GameContextTest.scala

@@ -1,81 +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 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

@@ -0,0 +1,41 @@
+package de.nowchess.chess.logic
+
+import de.nowchess.api.board.*
+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

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.GameContext
+import de.nowchess.chess.logic.GameHistory
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -12,7 +12,11 @@ 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 ctx(entries: (Square, Piece)*): GameContext = GameContext(Board(entries.toMap))
+  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)
 
   // ──── isInCheck ──────────────────────────────────────────────────────
 
@@ -41,20 +45,20 @@ 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 = GameRules.legalMoves(ctx(
+    val moves = testLegalMoves(
       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 = GameRules.legalMoves(ctx(
+    val moves = testLegalMoves(
       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 ──────────────────────────────────────────────────────
@@ -62,70 +66,96 @@ 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)
-    GameRules.gameStatus(ctx(
+    testGameStatus(
       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)
-    GameRules.gameStatus(ctx(
+    testGameStatus(
       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
-    GameRules.gameStatus(ctx(
+    testGameStatus(
       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(GameContext(Board.initial), Color.White) shouldBe PositionStatus.Normal
+    GameRules.gameStatus(Board.initial, GameHistory.empty, Color.White) shouldBe PositionStatus.Normal
 
   test("legalMoves: includes castling destination when available"):
-    val c = GameContext(
-      board = board(
+    val b = board(
         sq(File.E, Rank.R1) -> Piece.WhiteKing,
         sq(File.H, Rank.R1) -> Piece.WhiteRook,
         sq(File.H, Rank.R8) -> Piece.BlackKing
-      ),
-      whiteCastling = CastlingRights.Both,
-      blackCastling = CastlingRights.None
-    )
-    GameRules.legalMoves(c, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
+      )
+    GameRules.legalMoves(b, GameHistory.empty, Color.White) should contain(sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
 
   test("legalMoves: excludes castling when king is in check"):
-    val c = GameContext(
-      board = board(
+    val b = 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
-      ),
-      whiteCastling = CastlingRights.Both,
-      blackCastling = CastlingRights.None
-    )
-    GameRules.legalMoves(c, Color.White) should not contain (sq(File.E, Rank.R1) -> sq(File.G, Rank.R1))
+      )
+    GameRules.legalMoves(b, GameHistory.empty, 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 c = GameContext(
-      board = board(
+    val b = 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
-      ),
-      whiteCastling = CastlingRights(kingSide = true, queenSide = false),
-      blackCastling = CastlingRights.None
+      )
+    // 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
     )
-    GameRules.gameStatus(c, Color.White) shouldBe PositionStatus.Normal
+    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

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

@@ -2,7 +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.{GameContext, CastleSide}
+import de.nowchess.chess.logic.{CastleSide, GameHistory}
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
@@ -211,168 +211,3 @@ class MoveValidatorTest extends AnyFunSuite with Matchers:
       sq(File.E, Rank.R4) -> Piece.BlackRook
     )
     MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R4))
-
-  // ──── castlingTargets ────────────────────────────────────────────────
-
-  private def ctxWithRights(
-    entries: (Square, Piece)*
-  )(white: CastlingRights = CastlingRights.Both,
-    black: CastlingRights = CastlingRights.Both
-  ): GameContext =
-    GameContext(Board(entries.toMap), white, black)
-
-  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("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("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))
-
-  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("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)
-
-  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("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("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("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("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("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/versions.env

@@ -0,0 +1,3 @@
+MAJOR=0
+MINOR=2
+PATCH=0