v0.2.0 transitioned to api-only, extended and improved features, docs and tests added

2025-10-29 23:28:19 -04:00
parent b98ea83012
commit 0ad608293e
32 changed files with 3683 additions and 1670 deletions
--- a/README.md
+++ b/README.md
@ -1,7 +1,7 @@
 <table>
  <tr>
    <td>
-      <h1>Go Chess</h1>
+      <h1>Go Chess API</h1>
      <p>
        <a href="https://golang.org"><img src="https://img.shields.io/badge/Go-1.24-00ADD8?style=flat&logo=go" alt="Go"></a>
        <a href="https://opensource.org/licenses/BSD-3-Clause"><img src="https://img.shields.io/badge/License-BSD_3--Clause-blue.svg" alt="License"></a>
@ -10,39 +10,60 @@
  </tr>
 </table>

-# Go Chess
+# Chess

-A command-line chess application written in Go.
+Go backend server providing a RESTful API for chess gameplay. Integrates Stockfish engine for move validation and AI opponents.

 ## Features

-*   Command-line interface for gameplay.
-*   Uses an stockfish external chess engine for move validation and computer play.
-*   Supports player vs. player, player vs. computer, and computer vs. computer modes.
-*   Start a new game from the standard starting position.
-*   Resume a game from a FEN (Forsyth-Edwards Notation) string.
-*   Move history display.
-*   Move undo functionality.
+- RESTful API for chess operations
+- Stockfish engine integration for validation and AI
+- Human vs human, human vs computer, computer vs computer modes
+- Custom FEN position support
+- Asynchronous AI move calculation
+- Configurable AI strength and thinking time

-## System Requirements
+## Requirements

-*   **Go Version**: 1.24+ (for building from source)
-*   **Engine**: Requires the **Stockfish** chess engine to be installed. The `stockfish` executable must be available in the system's PATH.
+- Go 1.24+
+- Stockfish chess engine (`stockfish` in PATH)
+
+### Installation
+
+```bash
+# Arch Linux
+yay -S stockfish
+
+# FreeBSD
+pkg install stockfish
+```

 ## Quick Start

-To build and run the application:
+```bash
+git clone https://git.lixen.com/lixen/chess
+cd chess
+go build ./cmd/chessd

-```sh
-# Build the executable
-go build ./cmd/chess
+# Standard mode (1 request/second/IP)
+./chessd

-# Run the application
-./chess
+# Development mode (10 requests/second/IP)
+./chessd -dev
+
+# Run tests (requires dev mode)
+./test/test-api.sh
 ```

-Inside the application, type `help` to see available commands.
+Server listens on `http://localhost:8080`. See [API Reference](./doc/api.md) for endpoints.
+
+## Documentation
+
+- [API Reference](./doc/api.md) - Endpoint specifications
+- [Architecture](./doc/architecture.md) - System design
+- [Development](./doc/development.md) - Build and test instructions
+- [Stockfish Integration](./doc/stockfish.md) - Engine communication

 ## License

-BSD 3-Clause License
+BSD 3-Clause
--- a/cmd/chess/main.go
+++ b/cmd/chess/main.go
@ -1,26 +0,0 @@
-// FILE: cmd/chess/main.go
-package main
-
-import (
-	"fmt"
-	"os"
-
-	"chess/internal/cli"
-	"chess/internal/service"
-	clitransport "chess/internal/transport/cli"
-)
-
-func main() {
-	svc, err := service.New()
-	if err != nil {
-		fmt.Printf("Failed to start: %v\n", err)
-		os.Exit(1)
-	}
-	defer svc.Close()
-
-	view := cli.New(os.Stdin, os.Stdout)
-	handler := clitransport.New(svc, view)
-
-	view.ShowWelcome()
-	handler.Run() // All game loop logic is in the handler
-}
--- a/cmd/chessd/main.go
+++ b/cmd/chessd/main.go
@ -2,7 +2,6 @@
 package main

 import (
-	"context"
 	"flag"
 	"fmt"
 	"log"
@ -11,8 +10,9 @@ import (
 	"syscall"
 	"time"

+	"chess/internal/http"
+	"chess/internal/processor"
 	"chess/internal/service"
-	"chess/internal/transport/http"
 )

 func main() {
@ -24,48 +24,57 @@ func main() {
 	)
 	flag.Parse()

-	// Initialize service (includes engine)
+	// 1. Initialize the Service (Pure State Manager)
 	svc, err := service.New()
 	if err != nil {
 		log.Fatalf("Failed to initialize service: %v", err)
 	}
+	defer svc.Close()
+
+	// 2. Initialize the Processor (Orchestrator), injecting the service
+	proc, err := processor.New(svc)
+	if err != nil {
+		log.Fatalf("Failed to initialize processor: %v", err)
+	}
 	defer func() {
-		if err := svc.Close(); err != nil {
-			log.Printf("Warning: failed to close service cleanly: %v", err)
+		if err := proc.Close(); err != nil {
+			log.Printf("Warning: failed to close processor cleanly: %v", err)
 		}
 	}()

-	// Create Fiber app with dev mode flag
-	app := http.NewFiberApp(svc, *dev)
+	// 3. Initialize the Fiber App/HTTP Handler, injecting the processor
+	app := http.NewFiberApp(proc, *dev)

 	// Server configuration
 	addr := fmt.Sprintf("%s:%d", *host, *port)

-	// Start server in goroutine
+	// Start server in a goroutine
 	go func() {
 		log.Printf("Chess API Server starting...")
 		log.Printf("Listening on: http://%s", addr)
 		log.Printf("API Version: v1")
-		log.Printf("Rate Limit: 1 request/second per IP")
+		if *dev {
+			log.Printf("Rate Limit: 10 requests/second per IP (DEV MODE)")
+		} else {
+			log.Printf("Rate Limit: 1 request/second per IP")
+		}
 		log.Printf("Endpoints: http://%s/api/v1/games", addr)
 		log.Printf("Health: http://%s/health", addr)

 		if err := app.Listen(addr); err != nil {
-			log.Printf("Server error: %v", err)
+			// This log often prints on graceful shutdown, which is normal.
+			log.Printf("Server listen error: %v", err)
 		}
 	}()

-	// Wait for interrupt signal
+	// Wait for an interrupt signal to gracefully shut down
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, os.Interrupt, syscall.SIGTERM)
 	<-quit

 	log.Println("Shutting down server...")

-	// Graceful shutdown with timeout
-	_, cancel := context.WithTimeout(context.Background(), 5*time.Second)
-	defer cancel()
-
+	// Graceful shutdown with a timeout
 	if err := app.ShutdownWithTimeout(5 * time.Second); err != nil {
 		log.Printf("Server forced to shutdown: %v", err)
 	}
--- a/doc/api.md
+++ b/doc/api.md
@ -0,0 +1,160 @@
+# API Reference
+
+Base URL: `http://localhost:8080/api/v1`
+
+Content-Type: `application/json` (required for POST/PUT)
+
+## Endpoints
+
+### Create Game
+`POST /games`
+
+Creates new game with specified players.
+
+**Request:**
+```json
+{
+  "white": {
+    "type": 1,
+    "level": 0,
+    "searchTime": 0
+  },
+  "black": {
+    "type": 2,
+    "level": 15,
+    "searchTime": 1000
+  },
+  "fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
+}
+```
+
+- `type` (integer, required): 1=human, 2=computer
+- `level` (integer, 0-20): AI skill level for computer players
+- `searchTime` (integer, 100-10000ms): AI thinking time for computer players
+- `fen` (string): Starting position in FEN notation (default: standard position)
+
+**Response (201):**
+```json
+{
+  "gameId": "a1b2c3d4-e5f6-7890-1234-567890abcdef",
+  "fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
+  "turn": "w",
+  "state": "ongoing",
+  "moves": [],
+  "players": {
+    "white": {"id": "...", "color": 1, "type": 1},
+    "black": {"id": "...", "color": 2, "type": 2, "level": 15, "searchTime": 1000}
+  }
+}
+```
+
+### Get Game
+`GET /games/{gameId}`
+
+Returns current game state.
+
+**Response (200):**
+```json
+{
+  "gameId": "...",
+  "fen": "...",
+  "turn": "w",
+  "state": "ongoing",
+  "moves": ["e2e4", "e7e5"],
+  "players": {...},
+  "lastMove": {
+    "move": "e7e5",
+    "playerColor": "b",
+    "score": 25,
+    "depth": 12
+  }
+}
+```
+
+States: `ongoing`, `pending` (computer thinking), `white wins`, `black wins`, `draw`, `stalemate`
+
+### Make Move
+`POST /games/{gameId}/moves`
+
+Submits human move or triggers computer move.
+
+**Human move:**
+```json
+{"move": "e2e4"}
+```
+
+**Computer move trigger:**
+```json
+{"move": "cccc"}
+```
+
+Returns updated game state (200) or error (400).
+
+### Undo Moves
+`POST /games/{gameId}/undo`
+
+Reverts moves from history.
+
+**Request:**
+```json
+{"count": 2}
+```
+
+- `count` (integer, 1-300): Number of moves to undo (default: 1)
+
+### Configure Players
+`PUT /games/{gameId}/players`
+
+Changes player configuration mid-game.
+
+**Request:**
+```json
+{
+  "white": {"type": 2, "level": 5, "searchTime": 100},
+  "black": {"type": 1}
+}
+```
+
+### Get Board
+`GET /games/{gameId}/board`
+
+Returns ASCII board visualization.
+
+**Response (200):**
+```json
+{
+  "fen": "...",
+  "board": "  a b c d e f g h\n8 r n b q k b n r 8\n..."
+}
+```
+
+### Delete Game
+`DELETE /games/{gameId}`
+
+Removes game from memory. Returns 204 on success.
+
+## Error Format
+
+```json
+{
+  "error": "Description",
+  "code": "ERROR_CODE",
+  "details": "Additional context"
+}
+```
+
+Error codes:
+- `GAME_NOT_FOUND` - Invalid game ID
+- `INVALID_MOVE` - Illegal chess move
+- `NOT_HUMAN_TURN` - Wrong player type for turn
+- `GAME_OVER` - Game already ended
+- `RATE_LIMIT_EXCEEDED` - Request limit exceeded
+- `INVALID_REQUEST` - Malformed request
+- `INVALID_CONTENT_TYPE` - Missing/wrong Content-Type header
+
+## Rate Limiting
+
+- Standard: 10 request/second/IP
+- Development (`-dev`): 20 requests/second/IP
+
+Exceeding limit returns 429 status.
--- a/doc/architecture.md
+++ b/doc/architecture.md
@ -0,0 +1,61 @@
+# Architecture
+
+## Components
+
+### Transport Layer (`internal/http`)
+Fiber web server handling HTTP requests/responses. Implements routing, rate limiting, content-type validation, request parsing. Translates HTTP to internal Command objects.
+
+### Processing Layer (`internal/processor`)
+Central command handler containing business logic. Single `Execute(Command)` entry point decouples transport from logic. Uses synchronous UCI engine for validation, asynchronous EngineQueue for computer moves.
+
+### Service Layer (`internal/service`)
+In-memory state storage without chess logic. Thread-safe game map protected by RWMutex. Manages game lifecycle, snapshots, and player configuration.
+
+### Supporting Modules
+- **Engine** (`internal/engine`): UCI protocol wrapper for Stockfish process communication
+- **Game** (`internal/game`): Game state with snapshot history
+- **Board** (`internal/board`): FEN parsing and ASCII generation
+- **Core** (`internal/core`): Shared types, API models, error constants
+
+## Request Flow
+
+### Human Move
+1. HTTP handler receives `POST /games/{id}/moves` with UCI move
+2. Creates MakeMoveCommand, calls `processor.Execute()`
+3. Processor validates move via locked validation engine
+4. If legal, gets new FEN from engine
+5. Calls `service.ApplyMove()` to update state
+6. Returns GameResponse
+
+### Computer Move
+1. HTTP handler receives `POST /games/{id}/moves` with `{"move": "cccc"}`
+2. Processor sets game state to `pending`
+3. Submits task to EngineQueue, returns immediately
+4. Worker goroutine calculates move with dedicated Stockfish instance
+5. Callback updates game state via service
+6. Client polls for completion
+
+## Concurrency
+
+- **HTTP Server**: Fiber handles concurrent connections
+- **Game State**: Single RWMutex protects game map (concurrent reads, serial writes)
+- **Engine Workers**: Fixed pool (2 workers) with dedicated Stockfish processes
+- **Validation Engine**: Single mutex-protected instance for synchronous validation
+
+## Data Structures
+
+### Game Snapshot
+```go
+type Snapshot struct {
+    FEN           string
+    PreviousMove  string
+    NextTurnColor Color
+    PlayerID      string
+}
+```
+
+### Command Pattern
+Commands encapsulate operations with type and arguments, processed by single Execute method.
+
+### Player Configuration
+Players identified by UUID, configured with type (human/computer), skill level, and search time.
--- a/doc/development.md
+++ b/doc/development.md
@ -0,0 +1,89 @@
+# Development Guide
+
+## Prerequisites
+
+- Go 1.24+
+- Stockfish in PATH
+- Git
+- curl, jq (for testing)
+
+## Building
+
+```bash
+git clone https://git.lixen.com/lixen/chess
+cd chess
+go build ./cmd/chessd
+```
+
+## Running
+
+### Flags
+- `-host`: Server host (default: localhost)
+- `-port`: Server port (default: 8080)
+- `-dev`: Development mode with relaxed rate limits
+
+### Modes
+```bash
+# Production (1 req/s rate limit)
+./chessd
+
+# Development (10 req/s rate limit)
+./chessd -dev
+```
+
+## Project Structure
+
+```
+chess/
+├── cmd/chessd/        # Entry point
+├── internal/
+│   ├── board/         # FEN/ASCII operations
+│   ├── core/          # Shared types
+│   ├── engine/        # Stockfish UCI wrapper
+│   ├── game/          # Game state
+│   ├── http/          # Fiber handlers
+│   ├── processor/     # Command processing
+│   └── service/       # State management
+└── test/              # Test scripts
+```
+
+## Testing
+
+```bash
+# Unit tests
+go test ./...
+
+# API tests (requires dev mode)
+./chessd -dev &
+./test/test-api.sh
+```
+
+Test script validates:
+- Basic CRUD operations
+- Computer move triggering ("cccc" mechanism)
+- Pending state protection
+- Rate limiting
+- Input validation
+- Error handling
+
+## Configuration
+
+### Fixed Values
+- Engine path: `"stockfish"` (internal/engine/engine.go)
+- Worker count: 2 (internal/processor/processor.go)
+- Queue capacity: 100 (internal/processor/queue.go)
+- Min search time: 100ms (internal/processor/processor.go)
+
+### Validation Rules
+- Player type: 1 (human) or 2 (computer)
+- Skill level: 0-20
+- Search time: 100-10000ms
+- UCI moves: 4-5 characters ([a-h][1-8][a-h][1-8][qrbn]?)
+- Undo count: 1-300
+
+## Limitations
+
+- No persistence (memory only)
+- Hardcoded Stockfish path
+- Fixed worker pool size
+- No game history beyond current session
--- a/doc/stockfish-extended.md
+++ b/doc/stockfish-extended.md
@ -0,0 +1,316 @@
+# Stockfish UCI Protocol Reference
+
+## UCI Protocol Overview
+
+Universal Chess Interface (UCI) is a text-based protocol for communication between chess engines and GUIs. Commands are line-based with ASCII encoding.
+
+## Initialization Sequence
+
+```
+→ uci
+← id name Stockfish 16
+← id author Stockfish developers
+← option name Debug Log File type string default
+← option name Threads type spin default 1 min 1 max 1024
+← option name Hash type spin default 16 min 1 max 33554432
+← [... more options ...]
+← uciok
+
+→ isready
+← readyok
+```
+
+## Core UCI Commands
+
+### Engine Identification
+- `uci` - Initialize UCI mode, engine responds with options and `uciok`
+- `quit` - Terminate engine process
+
+### Synchronization
+- `isready` - Synchronization command, engine responds `readyok` when ready
+- `ucinewgame` - Clear hash tables and reset for new game
+
+### Position Setup
+```
+position [fen <fenstring> | startpos] [moves <move1> ... <moveN>]
+```
+- `startpos` - Standard starting position
+- `fen <fenstring>` - Custom position in FEN notation
+- `moves` - Apply moves from position in UCI format (e.g., e2e4, e7e8q)
+
+### Search Commands
+
+#### Basic Search
+```
+go [searchmoves <move1> ... <moveN>] [ponder] [wtime <ms>] [btime <ms>]
+   [winc <ms>] [binc <ms>] [movestogo <n>] [depth <n>] [nodes <n>]
+   [mate <n>] [movetime <ms>] [infinite]
+```
+
+Parameters:
+- `searchmoves` - Restrict search to specific moves
+- `ponder` - Start pondering mode (thinking on opponent's time)
+- `wtime/btime` - White/black time remaining (ms)
+- `winc/binc` - White/black increment per move (ms)
+- `movestogo` - Moves until next time control
+- `depth` - Search to fixed depth
+- `nodes` - Search fixed number of positions
+- `mate` - Search for mate in N moves
+- `movetime` - Search for fixed time (ms)
+- `infinite` - Search until `stop` command
+
+#### Search Control
+- `stop` - Stop calculating and return best move
+- `ponderhit` - Opponent played expected ponder move
+
+### Engine Options
+```
+setoption name <option_name> [value <value>]
+```
+
+## Stockfish-Specific Options
+
+### Search Parameters
+- `MultiPV` (1-500): Number of principal variations to calculate
+- `Skill Level` (0-20): Playing strength limitation
+- `Contempt` (-100 to 100): Draw avoidance tendency
+- `Analysis Contempt` (Off/White/Black/Both): Contempt perspective
+- `Move Overhead` (0-5000ms): Time buffer for network/GUI delay
+- `Slow Mover` (10-1000): Time management aggressiveness
+- `UCI_AnalyseMode` (true/false): Optimization for analysis
+- `UCI_Chess960` (true/false): Fischer Random Chess support
+- `UCI_ShowWDL` (true/false): Show win/draw/loss probabilities
+- `UCI_LimitStrength` (true/false): Enable ELO limitation
+- `UCI_Elo` (1320-3190): Target ELO when strength limited
+
+### Hash Tables
+- `Hash` (1-33554432 MB): Transposition table size
+- `Clear Hash`: Clear transposition table
+- `Ponder` (true/false): Think during opponent's turn
+
+### Hardware Configuration
+- `Threads` (1-1024): Search threads (typically CPU cores)
+- `Use NNUE` (true/false): Neural network evaluation
+- `EvalFile` (path): Custom NNUE evaluation file
+
+### Syzygy Tablebases
+- `SyzygyPath` (path): Directory containing tablebase files
+- `SyzygyProbeDepth` (1-100): Minimum depth for tablebase probing
+- `Syzygy50MoveRule` (true/false): Consider 50-move rule
+- `SyzygyProbeLimit` (0-7): Maximum pieces for probing
+
+## Debug Commands
+
+### Board Display
+```
+→ d
+← 
+ +---+---+---+---+---+---+---+---+
+ | r | n | b | q | k | b | n | r | 8
+ +---+---+---+---+---+---+---+---+
+ | p | p | p | p | p | p | p | p | 7
+ +---+---+---+---+---+---+---+---+
+ |   |   |   |   |   |   |   |   | 6
+ [...]
+ +---+---+---+---+---+---+---+---+
+   a   b   c   d   e   f   g   h
+
+Fen: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
+Key: 8F8F01D4562F59FB
+Checkers:
+```
+
+### Evaluation
+```
+→ eval
+← Total evaluation: +0.25 (white side)
+← [detailed NNUE evaluation breakdown]
+```
+
+### Performance Testing
+```
+→ bench [depth] [threads] [hash] [fenfile] [limittype] [evaltype]
+```
+Default: `bench 13 1 16 default depth mixed`
+
+## Search Output Format
+
+### Standard Info String
+```
+info depth <d> seldepth <sd> multipv <n> score <score> nodes <n> 
+     nps <n> hashfull <n> tbhits <n> time <ms> pv <move1> ... <moveN>
+```
+
+Fields:
+- `depth` - Current search depth
+- `seldepth` - Selective search depth
+- `multipv` - PV number (when MultiPV > 1)
+- `score cp <n>` - Evaluation in centipawns
+- `score mate <n>` - Mate in N moves (negative if being mated)
+- `score lowerbound/upperbound` - Bound type in fail-high/low
+- `nodes` - Nodes searched
+- `nps` - Nodes per second
+- `hashfull` - Hash table saturation (per mill)
+- `tbhits` - Tablebase positions found
+- `time` - Search time (ms)
+- `pv` - Principal variation (best line)
+- `currmove` - Currently searching move
+- `currmovenumber` - Move number in root move list
+- `string` - Free-form engine output
+
+### Win/Draw/Loss Output (UCI_ShowWDL=true)
+```
+info depth 20 score cp 15 wdl 395 604 1
+```
+WDL values in per mill: win/draw/loss from current side's perspective.
+
+### Multi-PV Example
+```
+setoption name MultiPV value 3
+go depth 15
+
+info multipv 1 depth 15 score cp 31 pv e2e4 e7e5 g1f3
+info multipv 2 depth 15 score cp 20 pv d2d4 d7d5 g1f3
+info multipv 3 depth 15 score cp 15 pv g1f3 g8f6 d2d4
+```
+
+## Best Move Output
+```
+bestmove <move> [ponder <move>]
+```
+- `bestmove` - Best move in UCI notation
+- `ponder` - Expected opponent response for pondering
+
+Special cases:
+- `bestmove (none)` - No legal moves (checkmate/stalemate)
+- `bestmove 0000` - Null move (analysis mode only)
+
+## Advanced Analysis Techniques
+
+### Infinite Analysis
+```
+position fen <position>
+setoption name UCI_AnalyseMode value true
+go infinite
+[... engine thinks until stop ...]
+stop
+```
+
+### Multi-PV Analysis
+```
+setoption name MultiPV value 5
+position startpos moves e2e4 e7e5
+go depth 20
+```
+
+### Mate Search
+```
+go mate 7  # Find mate in 7 moves or less
+```
+
+### Fixed Node Search
+```
+go nodes 1000000  # Analyze exactly 1M positions
+```
+
+### Search Move Restriction
+```
+position startpos
+go searchmoves e2e4 d2d4 g1f3  # Only consider these moves
+```
+
+## Time Management
+
+### Tournament Time Control
+```
+position startpos moves e2e4 e7e5
+go wtime 300000 btime 300000 winc 2000 binc 2000 movestogo 40
+```
+5 minutes + 2 second increment, 40 moves to time control.
+
+### Sudden Death
+```
+go wtime 60000 btime 60000  # 1 minute each, no increment
+```
+
+### Fixed Time Per Move
+```
+go movetime 5000  # Think for exactly 5 seconds
+```
+
+## Performance Tuning
+
+### Analysis Optimization
+```
+setoption name Threads value 8
+setoption name Hash value 4096
+setoption name UCI_AnalyseMode value true
+setoption name MultiPV value 1
+```
+
+### Rapid/Blitz Optimization
+```
+setoption name Move Overhead value 100
+setoption name Slow Mover value 50
+setoption name Threads value 4
+```
+
+### Endgame Optimization
+```
+setoption name SyzygyPath value /path/to/tablebases
+setoption name SyzygyProbeDepth value 1
+```
+
+## Error Handling
+
+Common error responses:
+- `Unknown command: <cmd>` - Invalid UCI command
+- `Illegal move: <move>` - Move not legal in current position
+- `Invalid position` - FEN parsing failed
+- `No such option: <name>` - Unknown engine option
+
+## Protocol Extensions
+
+### Chess960 (Fischer Random)
+```
+setoption name UCI_Chess960 value true
+position fen <chess960_fen> moves <move1> ...
+```
+
+### Debug Logging
+```
+setoption name Debug Log File value debug.txt
+setoption name Use Debug Log value true
+```
+
+### NNUE Evaluation
+```
+setoption name Use NNUE value true
+setoption name EvalFile value nn-[hash].nnue
+```
+
+## Typical Usage Patterns
+
+### Game Analysis
+1. Set analysis mode and resources
+2. Load position with game moves
+3. Run infinite analysis
+4. Stop and retrieve evaluation
+
+### Opening Preparation
+1. Set MultiPV to compare variations
+2. Load opening position
+3. Search to fixed depth
+4. Compare evaluations of candidate moves
+
+### Endgame Study
+1. Configure tablebase paths
+2. Load endgame position
+3. Search for mate or optimal play
+4. Verify with tablebase hits
+
+### Engine Match
+1. Reset with ucinewgame
+2. Set time controls
+3. Apply moves incrementally
+4. Use ponder for thinking on opponent time
--- a/doc/stockfish.md
+++ b/doc/stockfish.md
@ -0,0 +1,85 @@
+# Stockfish Integration
+
+## UCI Protocol Implementation
+
+### Connection Management
+Engine process started via `exec.Command("stockfish")` with bidirectional pipes. Initialization sequence:
+1. Send `uci` → await `uciok`
+2. Send `isready` → await `readyok`
+3. Engine ready for commands
+
+### Commands Used
+
+#### Position Setting
+```
+position fen <fen_string> [moves <move1> <move2> ...]
+```
+Sets board state for validation or search.
+
+#### Move Search
+```
+go movetime <milliseconds>
+```
+Calculates best move with time constraint. Returns:
+- `info depth X score cp Y pv ...` (evaluation info)
+- `bestmove <move>` (final result)
+
+#### Board State Query
+```
+d
+```
+Debug command returning board visualization and FEN. Used for move validation.
+
+#### Configuration
+```
+setoption name Skill Level value <0-20>
+```
+Sets engine strength for computer players.
+
+### Response Parsing
+
+#### Search Results
+```go
+type SearchResult struct {
+    BestMove string  // UCI format move
+    Score    int     // Centipawns or mate distance
+    Depth    int     // Search depth reached
+    IsMate   bool    // Checkmate detected
+    MateIn   int     // Moves to mate
+}
+```
+
+Parse `info` lines for evaluation data, `bestmove` for move selection.
+
+#### FEN Extraction
+Parse `d` output for line starting with `Fen: ` to get canonical position.
+
+### Application Usage
+
+#### Synchronous Validation (Processor)
+Single mutex-protected engine instance validates moves:
+1. Set position with current FEN
+2. Attempt move
+3. Get new FEN via `d` command
+4. Compare FENs to determine legality
+
+#### Asynchronous Calculation (EngineQueue)
+Worker pool with dedicated engines per worker:
+1. Receive task with FEN and time limit
+2. Configure skill level
+3. Search for best move
+4. Return result via callback
+
+### Error Handling
+
+- Timeout protection (2x search time + 1s buffer)
+- Process lifecycle management with graceful shutdown
+- Fallback to force kill if quit fails
+- "(none)" bestmove indicates no legal moves (checkmate/stalemate)
+
+### Performance Considerations
+
+- Reuse engine instances across multiple games
+- `ucinewgame` between games for cache clearing
+- Separate engines for validation vs calculation to avoid contention
+- Fixed worker pool prevents resource exhaustion
--- a/go.mod
+++ b/go.mod
@ -1,23 +1,30 @@
 module chess

-go 1.24
+go 1.24.0

 require (
+	github.com/go-playground/validator/v10 v10.28.0
 	github.com/gofiber/fiber/v2 v2.52.9
 	github.com/google/uuid v1.6.0
 )

 require (
-	github.com/andybalholm/brotli v1.1.0 // indirect
-	github.com/klauspost/compress v1.17.9 // indirect
-	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/andybalholm/brotli v1.2.0 // indirect
+	github.com/clipperhouse/stringish v0.1.1 // indirect
+	github.com/clipperhouse/uax29/v2 v2.3.0 // indirect
+	github.com/gabriel-vasile/mimetype v1.4.11 // indirect
+	github.com/go-playground/locales v0.14.1 // indirect
+	github.com/go-playground/universal-translator v0.18.1 // indirect
+	github.com/klauspost/compress v1.18.1 // indirect
+	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/mattn/go-runewidth v0.0.16 // indirect
-	github.com/philhofer/fwd v1.1.3-0.20240916144458-20a13a1f6b7c // indirect
-	github.com/rivo/uniseg v0.2.0 // indirect
-	github.com/tinylib/msgp v1.2.5 // indirect
+	github.com/mattn/go-runewidth v0.0.19 // indirect
+	github.com/philhofer/fwd v1.2.0 // indirect
+	github.com/tinylib/msgp v1.5.0 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
-	github.com/valyala/fasthttp v1.51.0 // indirect
-	github.com/valyala/tcplisten v1.0.0 // indirect
-	golang.org/x/sys v0.28.0 // indirect
+	github.com/valyala/fasthttp v1.68.0 // indirect
+	golang.org/x/crypto v0.43.0 // indirect
+	golang.org/x/sys v0.37.0 // indirect
+	golang.org/x/text v0.30.0 // indirect
 )
--- a/go.sum
+++ b/go.sum
@ -1,31 +1,57 @@
-github.com/andybalholm/brotli v1.1.0 h1:eLKJA0d02Lf0mVpIDgYnqXcUn0GqVmEFny3VuID1U3M=
-github.com/andybalholm/brotli v1.1.0/go.mod h1:sms7XGricyQI9K10gOSf56VKKWS4oLer58Q+mhRPtnY=
+github.com/andybalholm/brotli v1.2.0 h1:ukwgCxwYrmACq68yiUqwIWnGY0cTPox/M94sVwToPjQ=
+github.com/andybalholm/brotli v1.2.0/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
+github.com/clipperhouse/stringish v0.1.1 h1:+NSqMOr3GR6k1FdRhhnXrLfztGzuG+VuFDfatpWHKCs=
+github.com/clipperhouse/stringish v0.1.1/go.mod h1:v/WhFtE1q0ovMta2+m+UbpZ+2/HEXNWYXQgCt4hdOzA=
+github.com/clipperhouse/uax29/v2 v2.3.0 h1:SNdx9DVUqMoBuBoW3iLOj4FQv3dN5mDtuqwuhIGpJy4=
+github.com/clipperhouse/uax29/v2 v2.3.0/go.mod h1:Wn1g7MK6OoeDT0vL+Q0SQLDz/KpfsVRgg6W7ihQeh4g=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/gabriel-vasile/mimetype v1.4.10 h1:zyueNbySn/z8mJZHLt6IPw0KoZsiQNszIpU+bX4+ZK0=
+github.com/gabriel-vasile/mimetype v1.4.10/go.mod h1:d+9Oxyo1wTzWdyVUPMmXFvp4F9tea18J8ufA774AB3s=
+github.com/gabriel-vasile/mimetype v1.4.11 h1:AQvxbp830wPhHTqc1u7nzoLT+ZFxGY7emj5DR5DYFik=
+github.com/gabriel-vasile/mimetype v1.4.11/go.mod h1:d+9Oxyo1wTzWdyVUPMmXFvp4F9tea18J8ufA774AB3s=
+github.com/go-playground/assert/v2 v2.2.0 h1:JvknZsQTYeFEAhQwI4qEt9cyV5ONwRHC+lYKSsYSR8s=
+github.com/go-playground/assert/v2 v2.2.0/go.mod h1:VDjEfimB/XKnb+ZQfWdccd7VUvScMdVu0Titje2rxJ4=
+github.com/go-playground/locales v0.14.1 h1:EWaQ/wswjilfKLTECiXz7Rh+3BjFhfDFKv/oXslEjJA=
+github.com/go-playground/locales v0.14.1/go.mod h1:hxrqLVvrK65+Rwrd5Fc6F2O76J/NuW9t0sjnWqG1slY=
+github.com/go-playground/universal-translator v0.18.1 h1:Bcnm0ZwsGyWbCzImXv+pAJnYK9S473LQFuzCbDbfSFY=
+github.com/go-playground/universal-translator v0.18.1/go.mod h1:xekY+UJKNuX9WP91TpwSH2VMlDf28Uj24BCp08ZFTUY=
+github.com/go-playground/validator/v10 v10.28.0 h1:Q7ibns33JjyW48gHkuFT91qX48KG0ktULL6FgHdG688=
+github.com/go-playground/validator/v10 v10.28.0/go.mod h1:GoI6I1SjPBh9p7ykNE/yj3fFYbyDOpwMn5KXd+m2hUU=
 github.com/gofiber/fiber/v2 v2.52.9 h1:YjKl5DOiyP3j0mO61u3NTmK7or8GzzWzCFzkboyP5cw=
 github.com/gofiber/fiber/v2 v2.52.9/go.mod h1:YEcBbO/FB+5M1IZNBP9FO3J9281zgPAreiI1oqg8nDw=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
-github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
-github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
-github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
-github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
-github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/klauspost/compress v1.18.1 h1:bcSGx7UbpBqMChDtsF28Lw6v/G94LPrrbMbdC3JH2co=
+github.com/klauspost/compress v1.18.1/go.mod h1:ZQFFVG+MdnR0P+l6wpXgIL4NTtwiKIdBnrBd8Nrxr+0=
+github.com/leodido/go-urn v1.4.0 h1:WT9HwE9SGECu3lg4d/dIA+jxlljEa1/ffXKmRjqdmIQ=
+github.com/leodido/go-urn v1.4.0/go.mod h1:bvxc+MVxLKB4z00jd1z+Dvzr47oO32F/QSNjSBOlFxI=
+github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
+github.com/mattn/go-colorable v0.1.14/go.mod h1:6LmQG8QLFO4G5z1gPvYEzlUgJ2wF+stgPZH1UqBm1s8=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
-github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
-github.com/philhofer/fwd v1.1.3-0.20240916144458-20a13a1f6b7c h1:dAMKvw0MlJT1GshSTtih8C2gDs04w8dReiOGXrGLNoY=
-github.com/philhofer/fwd v1.1.3-0.20240916144458-20a13a1f6b7c/go.mod h1:RqIHx9QI14HlwKwm98g9Re5prTQ6LdeRQn+gXJFxsJM=
-github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
-github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-github.com/tinylib/msgp v1.2.5 h1:WeQg1whrXRFiZusidTQqzETkRpGjFjcIhW6uqWH09po=
-github.com/tinylib/msgp v1.2.5/go.mod h1:ykjzy2wzgrlvpDCRc4LA8UXy6D8bzMSuAF3WD57Gok0=
+github.com/mattn/go-runewidth v0.0.19 h1:v++JhqYnZuu5jSKrk9RbgF5v4CGUjqRfBm05byFGLdw=
+github.com/mattn/go-runewidth v0.0.19/go.mod h1:XBkDxAl56ILZc9knddidhrOlY5R/pDhgLpndooCuJAs=
+github.com/philhofer/fwd v1.2.0 h1:e6DnBTl7vGY+Gz322/ASL4Gyp1FspeMvx1RNDoToZuM=
+github.com/philhofer/fwd v1.2.0/go.mod h1:RqIHx9QI14HlwKwm98g9Re5prTQ6LdeRQn+gXJFxsJM=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/tinylib/msgp v1.5.0 h1:GWnqAE54wmnlFazjq2+vgr736Akg58iiHImh+kPY2pc=
+github.com/tinylib/msgp v1.5.0/go.mod h1:cvjFkb4RiC8qSBOPMGPSzSAx47nAsfhLVTCZZNuHv5o=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
-github.com/valyala/fasthttp v1.51.0 h1:8b30A5JlZ6C7AS81RsWjYMQmrZG6feChmgAolCl1SqA=
-github.com/valyala/fasthttp v1.51.0/go.mod h1:oI2XroL+lI7vdXyYoQk03bXBThfFl2cVdIA3Xl7cH8g=
-github.com/valyala/tcplisten v1.0.0 h1:rBHj/Xf+E1tRGZyWIWwJDiRY0zc1Js+CV5DqwacVSA8=
-github.com/valyala/tcplisten v1.0.0/go.mod h1:T0xQ8SeCZGxckz9qRXTfG43PvQ/mcWh7FwZEA7Ioqkc=
-golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+github.com/valyala/fasthttp v1.68.0 h1:v12Nx16iepr8r9ySOwqI+5RBJ/DqTxhOy1HrHoDFnok=
+github.com/valyala/fasthttp v1.68.0/go.mod h1:5EXiRfYQAoiO/khu4oU9VISC/eVY6JqmSpPJoHCKsz4=
+github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
+github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
+golang.org/x/crypto v0.43.0 h1:dduJYIi3A3KOfdGOHX8AVZ/jGiyPa3IbBozJ5kNuE04=
+golang.org/x/crypto v0.43.0/go.mod h1:BFbav4mRNlXJL4wNeejLpWxB7wMbc79PdRGhWKncxR0=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
-golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ=
+golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.30.0 h1:yznKA/E9zq54KzlzBEAWn1NXSQ8DIp/NYMy88xJjl4k=
+golang.org/x/text v0.30.0/go.mod h1:yDdHFIX9t+tORqspjENWgzaCVXgk0yYnYuSZ8UzzBVM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
--- a/internal/board/board.go
+++ b/internal/board/board.go
@ -21,7 +21,7 @@ type Board struct {
 	fullmove  int
 }

-func FEN(fen string) (*Board, error) {
+func ParseFEN(fen string) (*Board, error) {
 	parts := strings.Fields(fen)
 	if len(parts) != 6 {
 		return nil, fmt.Errorf("invalid FEN: expected 6 parts, got %d", len(parts))
@ -54,10 +54,17 @@ func FEN(fen string) (*Board, error) {
 	}

 	// Parse game state with validation
-	if len(parts[1]) != 1 || (parts[1][0] != 'w' && parts[1][0] != 'b') {
+	if len(parts[1]) != 1 {
+		return nil, fmt.Errorf("invalid FEN: turn must be 'w' or 'b'")
+	}
+	switch parts[1] {
+	case "w":
+		b.turn = core.ColorWhite
+	case "b":
+		b.turn = core.ColorBlack
+	default:
 		return nil, fmt.Errorf("invalid FEN: turn must be 'w' or 'b'")
 	}
-	b.turn = core.Color(parts[1][0])
 	b.castling = parts[2]
 	b.enPassant = parts[3]

@ -71,6 +78,30 @@ func FEN(fen string) (*Board, error) {
 	return b, nil
 }

+// ToASCII creates an ASCII representation of the board
+func (b *Board) ToASCII() string {
+	var sb strings.Builder
+	sb.WriteString("  a b c d e f g h\n")
+
+	for r := 0; r < 8; r++ {
+		sb.WriteString(fmt.Sprintf("%d ", 8-r))
+		for f := 0; f < 8; f++ {
+			square := fmt.Sprintf("%c%c", 'a'+f, '8'-r)
+			piece := b.GetPieceAt(square)
+
+			if piece == 0 {
+				sb.WriteString(". ")
+			} else {
+				sb.WriteString(fmt.Sprintf("%c ", piece))
+			}
+		}
+		sb.WriteString(fmt.Sprintf(" %d\n", 8-r))
+	}
+	sb.WriteString("  a b c d e f g h")
+
+	return sb.String()
+}
+
 func (b *Board) Turn() core.Color {
 	return b.turn
 }
--- a/internal/cli/cli.go
+++ b/internal/cli/cli.go
@ -1,293 +0,0 @@
-// FILE: internal/cli/cli.go
-package cli
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"strings"
-
-	"chess/internal/board"
-	"chess/internal/core"
-	"chess/internal/game"
-)
-
-type CommandType int
-
-const (
-	CmdNone CommandType = iota
-	CmdNew
-	CmdResume
-	CmdMove
-	CmdUndo
-	CmdColor
-	CmdVerbose
-	CmdHistory
-	CmdHelp
-	CmdQuit
-)
-
-type Command struct {
-	Type CommandType
-	Args []string
-	Raw  string
-}
-
-type ColorTheme string
-
-const (
-	ThemeOff   ColorTheme = "off"
-	ThemeBrown ColorTheme = "brown"
-	ThemeGreen ColorTheme = "green"
-	ThemeGray  ColorTheme = "gray"
-)
-
-type themeColors struct {
-	lightBg string
-	darkBg  string
-	white   string
-	black   string
-	reset   string
-}
-
-var themes = map[ColorTheme]themeColors{
-	ThemeOff: {
-		lightBg: "",
-		darkBg:  "",
-		white:   "",
-		black:   "",
-		reset:   "",
-	},
-	ThemeBrown: {
-		lightBg: "\033[48;5;230m", // Beige
-		darkBg:  "\033[48;5;94m",  // Brown
-		white:   "\033[97m",
-		black:   "\033[30m",
-		reset:   "\033[0m",
-	},
-	ThemeGreen: {
-		lightBg: "\033[48;5;157m", // Light green
-		darkBg:  "\033[48;5;22m",  // Dark green
-		white:   "\033[97m",
-		black:   "\033[30m",
-		reset:   "\033[0m",
-	},
-	ThemeGray: {
-		lightBg: "\033[48;5;251m", // Light gray
-		darkBg:  "\033[48;5;240m", // Dark gray
-		white:   "\033[97m",
-		black:   "\033[30m",
-		reset:   "\033[0m",
-	},
-}
-
-type CLI struct {
-	input   *bufio.Scanner
-	output  io.Writer
-	theme   ColorTheme
-	verbose bool
-}
-
-func New(input io.Reader, output io.Writer) *CLI {
-	return &CLI{
-		input:   bufio.NewScanner(input),
-		output:  output,
-		theme:   ThemeOff,
-		verbose: false,
-	}
-}
-
-// Reads a command synchronously
-func (c *CLI) GetCommand() (*Command, error) {
-	if !c.input.Scan() {
-		if err := c.input.Err(); err != nil {
-			return nil, err
-		}
-		return &Command{Type: CmdQuit}, nil
-	}
-
-	input := strings.TrimSpace(c.input.Text())
-	if input == "" {
-		return &Command{Type: CmdNone}, nil
-	}
-
-	return c.parseCommand(input), nil
-}
-
-func (c *CLI) parseCommand(input string) *Command {
-	parts := strings.Fields(input)
-	if len(parts) == 0 {
-		return &Command{Type: CmdNone}
-	}
-
-	cmd := parts[0]
-	args := parts[1:]
-
-	switch cmd {
-	case "new":
-		return &Command{Type: CmdNew, Args: args}
-	case "resume":
-		return &Command{Type: CmdResume, Args: args, Raw: input}
-	case "undo":
-		return &Command{Type: CmdUndo, Args: args}
-	case "color":
-		return &Command{Type: CmdColor, Args: args}
-	case "verbose":
-		return &Command{Type: CmdVerbose}
-	case "history":
-		return &Command{Type: CmdHistory}
-	case "help", "?":
-		return &Command{Type: CmdHelp}
-	case "quit", "exit":
-		return &Command{Type: CmdQuit}
-	default:
-		// Assume it's a move
-		return &Command{Type: CmdMove, Args: []string{cmd}}
-	}
-}
-
-func (c *CLI) SetTheme(theme ColorTheme) error {
-	if _, ok := themes[theme]; !ok {
-		return fmt.Errorf("invalid theme: %s (use: off, brown, green, gray)", theme)
-	}
-	c.theme = theme
-	return nil
-}
-
-func (c *CLI) ToggleVerbose() bool {
-	c.verbose = !c.verbose
-	return c.verbose
-}
-
-func (c *CLI) IsVerbose() bool {
-	return c.verbose
-}
-
-func (c *CLI) ShowMessage(msg string) {
-	fmt.Fprintln(c.output, msg)
-}
-
-func (c *CLI) ShowError(err error) {
-	c.ShowMessage(fmt.Sprintf("Error: %v\n", err))
-}
-
-func (c *CLI) ShowPrompt(prompt string) {
-	fmt.Fprint(c.output, prompt)
-}
-
-func (c *CLI) ReadLine() string {
-	if c.input.Scan() {
-		return strings.TrimSpace(c.input.Text())
-	}
-	return ""
-}
-
-func (c *CLI) DisplayBoard(b *board.Board) {
-	theme := themes[c.theme]
-	var sb strings.Builder
-
-	sb.WriteString("\n  a b c d e f g h\n")
-
-	for r := 0; r < 8; r++ {
-		sb.WriteString(fmt.Sprintf("%d ", 8-r))
-		for f := 0; f < 8; f++ {
-			// Get piece at position
-			square := fmt.Sprintf("%c%c", 'a'+f, '8'-r)
-			piece := b.GetPieceAt(square)
-
-			if c.theme == ThemeOff {
-				// No colors, just show piece or space
-				if piece == 0 {
-					sb.WriteString("  ")
-				} else {
-					sb.WriteString(fmt.Sprintf("%c ", piece))
-				}
-			} else {
-				// Apply theme colors
-				bg := theme.darkBg
-				if (r+f)%2 == 0 {
-					bg = theme.lightBg
-				}
-
-				if piece == 0 {
-					sb.WriteString(fmt.Sprintf("%s  %s", bg, theme.reset))
-				} else {
-					color := theme.black
-					if piece >= 'A' && piece <= 'Z' {
-						color = theme.white
-					}
-					sb.WriteString(fmt.Sprintf("%s%s%c %s", bg, color, piece, theme.reset))
-				}
-			}
-		}
-		sb.WriteString(fmt.Sprintf(" %d\n", 8-r))
-	}
-	sb.WriteString("  a b c d e f g h\n")
-
-	c.ShowMessage(sb.String())
-}
-
-func (c *CLI) ShowHelp() {
-	help := `Commands:
-  new              - Start a new game with player type selection
-  resume <FEN>     - Resume from a specific board position
-  <move>           - Make a move (e.g., e2e4, g1f3)
-  undo [count]     - Undo last move(s), default 1
-  color <theme>    - Set board color theme (off|brown|green|gray)
-  verbose          - Toggle detailed move information
-  history          - Show game move history and positions
-  quit/exit        - Exit the program
-  help/?           - Show this help message
-
-During any game:
-  Press ENTER      - Execute computer move (when it's computer's turn)`
-
-	c.ShowMessage(help)
-}
-
-func (c *CLI) ShowWelcome() {
-	c.ShowMessage("Welcome to Chess!")
-	c.ShowMessage("Commands: new, resume <FEN>, <move>, undo, quit/exit, verbose, history, help/?")
-	c.ShowMessage("Example: 'resume 4k3/8/8/8/8/8/8/4K2R w K - 0 1' to start from a puzzle.")
-	c.ShowMessage("Press ENTER to execute computer moves when it's computer's turn.")
-	c.ShowMessage("")
-}
-
-func (c *CLI) ShowGameHistory(g *game.Game) {
-	c.ShowMessage(fmt.Sprintf("Starting FEN: %s\n", g.InitialFEN()))
-
-	moves := g.Moves()
-	for i := 0; i < len(moves); i += 2 {
-		moveNum := i/2 + 1
-		white := moves[i]
-		if i+1 < len(moves) {
-			black := moves[i+1]
-			c.ShowMessage(fmt.Sprintf("%d. %s | %s\n", moveNum, white, black))
-		} else {
-			c.ShowMessage(fmt.Sprintf("%d. %s | ...\n", moveNum, white))
-		}
-	}
-	c.ShowMessage(fmt.Sprintf("Current FEN: %s\n", g.CurrentFEN()))
-	c.ShowMessage(fmt.Sprintf("Game state: %s\n", g.State()))
-}
-
-func (c *CLI) ShowComputerMove(result *game.MoveResult) {
-	if c.verbose {
-		c.ShowMessage(fmt.Sprintf("Computer (%c): %s (depth=%d, score=%d)\n",
-			result.Player, result.Move, result.Depth, result.Score))
-	} else {
-		// Always show computer moves in non-verbose mode too
-		c.ShowMessage(fmt.Sprintf("Computer (%c): %s\n", result.Player, result.Move))
-	}
-}
-
-func (c *CLI) ShowHumanMove(move string) {
-	if c.verbose {
-		c.ShowMessage(fmt.Sprintf("Your move: %s\n", move))
-	}
-}
-
-func (c *CLI) ShowGameOver(state core.State) {
-	c.ShowMessage(fmt.Sprintf("\nGame Over: %s\n", state))
-	c.ShowMessage("Start a new game with 'new' or 'resume'.")
-}
--- a/internal/core/api.go
+++ b/internal/core/api.go
@ -0,0 +1,53 @@
+// FILE: internal/core/api.go
+package core
+
+// Request types
+
+type CreateGameRequest struct {
+	White PlayerConfig `json:"white" validate:"required"`
+	Black PlayerConfig `json:"black" validate:"required"`
+	FEN   string       `json:"fen,omitempty" validate:"omitempty,max=100"`
+}
+
+type ConfigurePlayersRequest struct {
+	White PlayerConfig `json:"white" validate:"required"`
+	Black PlayerConfig `json:"black" validate:"required"`
+}
+
+type MoveRequest struct {
+	Move string `json:"move" validate:"required,min=4,max=5"` // "cccc" for computer move, 4-5 chars for UCI moves
+}
+
+type UndoRequest struct {
+	Count int `json:"count" validate:"required,min=1,max=300"` // Max based on longest games in history (272), theoretical max 5949
+}
+
+// Response types
+
+type GameResponse struct {
+	GameID   string          `json:"gameId"`
+	FEN      string          `json:"fen"`
+	Turn     string          `json:"turn"`  // "w" or "b"
+	State    string          `json:"state"` // "ongoing", "white_wins", etc
+	Moves    []string        `json:"moves"`
+	Players  PlayersResponse `json:"players"`
+	LastMove *MoveInfo       `json:"lastMove,omitempty"`
+}
+
+type MoveInfo struct {
+	Move        string `json:"move"`
+	PlayerColor string `json:"playerColor"` // "w" or "b"
+	Score       int    `json:"score,omitempty"`
+	Depth       int    `json:"depth,omitempty"`
+}
+
+type BoardResponse struct {
+	FEN   string `json:"fen"`
+	Board string `json:"board"` // ASCII representation
+}
+
+type ErrorResponse struct {
+	Error   string `json:"error"`
+	Code    string `json:"code"`
+	Details string `json:"details,omitempty"`
+}
--- a/internal/core/core.go
+++ b/internal/core/core.go
@ -1,53 +0,0 @@
-// FILE: internal/core/core.go
-package core
-
-type State int
-
-const (
-	StateOngoing State = iota
-	StateWhiteWins
-	StateBlackWins
-	StateDraw
-	StateStalemate
-)
-
-func (s State) String() string {
-	switch s {
-	case StateWhiteWins:
-		return "White wins"
-	case StateBlackWins:
-		return "Black wins"
-	case StateDraw:
-		return "Draw"
-	case StateStalemate:
-		return "Stalemate"
-	default:
-		return "Ongoing"
-	}
-}
-
-type PlayerType int
-
-const (
-	PlayerHuman PlayerType = iota
-	PlayerComputer
-)
-
-type Player struct {
-	ID   string
-	Type PlayerType
-}
-
-type Color byte
-
-const (
-	ColorWhite Color = 'w'
-	ColorBlack Color = 'b'
-)
-
-func OppositeColor(c Color) Color {
-	if c == ColorWhite {
-		return ColorBlack
-	}
-	return ColorWhite
-}
--- a/internal/core/error.go
+++ b/internal/core/error.go
@ -0,0 +1,15 @@
+// FILE: internal/core/core.go
+package core
+
+// Error codes
+const (
+	ErrGameNotFound      = "GAME_NOT_FOUND"
+	ErrInvalidMove       = "INVALID_MOVE"
+	ErrNotHumanTurn      = "NOT_HUMAN_TURN"
+	ErrGameOver          = "GAME_OVER"
+	ErrRateLimitExceeded = "RATE_LIMIT_EXCEEDED"
+	ErrInvalidContent    = "INVALID_CONTENT_TYPE"
+	ErrInvalidRequest    = "INVALID_REQUEST"
+	ErrInvalidFEN        = "INVALID_FEN"
+	ErrInternalError     = "INTERNAL_ERROR"
+)
--- a/internal/core/player.go
+++ b/internal/core/player.go
@ -0,0 +1,75 @@
+// FILE: internal/core/player.go
+package core
+
+import (
+	"github.com/google/uuid"
+)
+
+type PlayerType int
+
+const (
+	PlayerHuman PlayerType = iota + 1
+	PlayerComputer
+)
+
+// Player is the complete game entity with all state
+type Player struct {
+	ID         string     `json:"id"`
+	Color      Color      `json:"color"`
+	Type       PlayerType `json:"type"`
+	Level      int        `json:"level,omitempty"`      // Only for computer
+	SearchTime int        `json:"searchTime,omitempty"` // Only for computer
+}
+
+// PlayerConfig for API requests and configuration
+type PlayerConfig struct {
+	Type       PlayerType `json:"type" validate:"required,oneof=1 2"`
+	Level      int        `json:"level,omitempty" validate:"omitempty,min=0,max=20"`
+	SearchTime int        `json:"searchTime,omitempty" validate:"omitempty,min=100,max=10000"` // Processor sets the min value
+}
+
+// PlayersResponse for API responses - now contains full Player structs
+type PlayersResponse struct {
+	White *Player `json:"white"`
+	Black *Player `json:"black"`
+}
+
+// NewPlayer creates a Player from PlayerConfig
+func NewPlayer(config PlayerConfig, color Color) *Player {
+	player := &Player{
+		ID:    uuid.New().String(),
+		Color: color,
+		Type:  config.Type,
+	}
+
+	if config.Type == PlayerComputer {
+		player.Level = config.Level
+		player.SearchTime = config.SearchTime
+	}
+
+	return player
+}
+
+type Color byte
+
+const (
+	ColorWhite = iota + 1
+	ColorBlack
+)
+
+func (c Color) String() string {
+	if c == ColorWhite {
+		return "w"
+	} else if c == ColorBlack {
+		return "b"
+	} else {
+		return "-"
+	}
+}
+
+func OppositeColor(c Color) Color {
+	if c == ColorWhite {
+		return ColorBlack
+	}
+	return ColorWhite
+}
--- a/internal/core/state.go
+++ b/internal/core/state.go
@ -0,0 +1,35 @@
+// FILE: internal/core/core.go
+package core
+
+type State int
+
+const (
+	StateOngoing State = iota
+	StatePending       // Computer is calculating a move
+	StateStuck         // Computer is calculating a move
+	StateWhiteWins
+	StateBlackWins
+	StateDraw
+	StateStalemate
+)
+
+func (s State) String() string {
+	switch s {
+	case StatePending:
+		return "pending"
+	case StateStuck:
+		return "stuck"
+	case StateWhiteWins:
+		return "white wins"
+	case StateBlackWins:
+		return "black wins"
+	case StateDraw:
+		return "draw"
+	case StateStalemate:
+		return "stalemate"
+	case StateOngoing:
+		return "ongoing"
+	default:
+		return "unknown"
+	}
+}
--- a/internal/engine/engine.go
+++ b/internal/engine/engine.go
@ -25,6 +25,8 @@ type SearchResult struct {
 	BestMove string
 	Score    int
 	Depth    int
+	IsMate   bool
+	MateIn   int
 }

 func New() (*UCI, error) {
@ -40,7 +42,7 @@ func New() (*UCI, error) {
 		return nil, err
 	}

-	if err := cmd.Start(); err != nil {
+	if err = cmd.Start(); err != nil {
 		return nil, fmt.Errorf("failed to start engine: %v", err)
 	}

@ -58,6 +60,16 @@ func New() (*UCI, error) {
 	return uci, nil
 }

+// SetSkillLevel sets the Stockfish skill level (0-20)
+func (u *UCI) SetSkillLevel(level int) {
+	if level < 0 {
+		level = 0
+	} else if level > 20 {
+		level = 20
+	}
+	u.sendCommand(fmt.Sprintf("setoption name Skill Level value %d", level))
+}
+
 // Get FEN from Stockfish's debug ('d') command
 func (u *UCI) GetFEN() (string, error) {
 	u.sendCommand("d")
@ -184,6 +196,16 @@ func (u *UCI) Search(timeMs int) (*SearchResult, error) {
 						fmt.Sscanf(fields[i+1], "%d", &result.Depth)
 					case "cp":
 						fmt.Sscanf(fields[i+1], "%d", &result.Score)
+						result.IsMate = false
+					case "mate":
+						fmt.Sscanf(fields[i+1], "%d", &result.MateIn)
+						result.IsMate = true
+						// Convert mate score to centipawn equivalent for backwards compatibility
+						if result.MateIn > 0 {
+							result.Score = 100000 - result.MateIn
+						} else {
+							result.Score = -100000 - result.MateIn
+						}
 					}
 				}
 			}
--- a/internal/game/game.go
+++ b/internal/game/game.go
@ -9,34 +9,45 @@ import (
 )

 type Snapshot struct {
-	FEN          string     // Board state at this point
-	PreviousMove string     // Move that created this position (empty for initial)
-	NextTurn     core.Color // Whose turn it is at this position
+	FEN           string          `json:"fen"`
+	PreviousMove  string          `json:"previousMove"`
+	NextTurnColor core.Color      `json:"nextTurnColor"`
+	PlayerType    core.PlayerType `json:"playerType"`
+	PlayerID      string          `json:"playerId"` // ID of the player whose turn it is
 }

 // MoveResult tracks the outcome of a move
 type MoveResult struct {
-	Move      string
-	Player    core.Color
-	GameState core.State
-	Score     int
-	Depth     int
+	Move        string     `json:"move"`
+	PlayerColor core.Color `json:"playerColor"`
+	GameState   core.State `json:"gameState"`
+	Score       int        `json:"score"`
+	Depth       int        `json:"depth"`
 }

 type Game struct {
-	snapshots  []Snapshot
-	players    map[core.Color]*core.Player
-	state      core.State
-	lastResult *MoveResult
+	snapshots  []Snapshot                  `json:"snapshots"`
+	players    map[core.Color]*core.Player `json:"players"`
+	state      core.State                  `json:"state"`
+	lastResult *MoveResult                 `json:"lastResult,omitempty"`
 }

-func New(initialFEN string, whitePlayer, blackPlayer *core.Player, startingTurn core.Color) *Game {
+func New(initialFEN string, whitePlayer, blackPlayer *core.Player, startingTurnColor core.Color) *Game {
+	// Determine which player's turn it is initially
+	var initialPlayerID string
+	if startingTurnColor == core.ColorWhite {
+		initialPlayerID = whitePlayer.ID
+	} else {
+		initialPlayerID = blackPlayer.ID
+	}
+
 	return &Game{
 		snapshots: []Snapshot{
 			{
-				FEN:          initialFEN,
-				PreviousMove: "", // No move led to initial position
-				NextTurn:     startingTurn,
+				FEN:           initialFEN,
+				PreviousMove:  "",
+				NextTurnColor: startingTurnColor,
+				PlayerID:      initialPlayerID,
 			},
 		},
 		players: map[core.Color]*core.Player{
@ -63,26 +74,40 @@ func (g *Game) CurrentFEN() string {
 	return g.CurrentSnapshot().FEN
 }

-func (g *Game) NextTurn() core.Color {
-	return g.CurrentSnapshot().NextTurn
+func (g *Game) NextTurnColor() core.Color {
+	return g.CurrentSnapshot().NextTurnColor
 }

 func (g *Game) NextPlayer() *core.Player {
-	return g.players[g.NextTurn()]
+	return g.players[g.NextTurnColor()]
 }

 func (g *Game) GetPlayer(color core.Color) *core.Player {
 	return g.players[color]
 }

-func (g *Game) AddSnapshot(fen string, move string, nextTurn core.Color) {
+func (g *Game) AddSnapshot(fen string, move string, nextTurnColor core.Color) {
+	// Get the player ID for the next turn
+	nextPlayer := g.players[nextTurnColor]
 	g.snapshots = append(g.snapshots, Snapshot{
-		FEN:          fen,
-		PreviousMove: move,
-		NextTurn:     nextTurn,
+		FEN:           fen,
+		PreviousMove:  move,
+		NextTurnColor: nextTurnColor,
+		PlayerID:      nextPlayer.ID,
 	})
 }

+func (g *Game) UpdatePlayers(whitePlayer, blackPlayer *core.Player) {
+	g.players[core.ColorWhite] = whitePlayer
+	g.players[core.ColorBlack] = blackPlayer
+
+	// Update current snapshot's PlayerID to reflect new player
+	if len(g.snapshots) > 0 {
+		currentSnap := &g.snapshots[len(g.snapshots)-1]
+		currentSnap.PlayerID = g.players[currentSnap.NextTurnColor].ID
+	}
+}
+
 func (g *Game) UndoMoves(count int) error {
 	if count < 1 {
 		return fmt.Errorf("invalid undo count: %d", count)
--- a/internal/http/handler.go
+++ b/internal/http/handler.go
@ -0,0 +1,412 @@
+// FILE: internal/http/handler.go
+package http
+
+import (
+	"chess/internal/core"
+	"chess/internal/processor"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/cors"
+	"github.com/gofiber/fiber/v2/middleware/limiter"
+	"github.com/gofiber/fiber/v2/middleware/logger"
+	"github.com/gofiber/fiber/v2/middleware/recover"
+)
+
+const rateLimitRate = 10 // req/sec
+
+type HTTPHandler struct {
+	proc *processor.Processor
+}
+
+func NewHTTPHandler(proc *processor.Processor) *HTTPHandler {
+	return &HTTPHandler{proc: proc}
+}
+
+func NewFiberApp(proc *processor.Processor, devMode bool) *fiber.App {
+	// Create handler
+	h := NewHTTPHandler(proc)
+
+	// Initialize Fiber app
+	app := fiber.New(fiber.Config{
+		ErrorHandler: customErrorHandler,
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 10 * time.Second,
+		IdleTimeout:  30 * time.Second,
+	})
+
+	// Global middleware (order matters)
+	app.Use(recover.New())
+	app.Use(logger.New(logger.Config{
+		Format: "${time} ${status} ${method} ${path} ${latency}\n",
+	}))
+	app.Use(cors.New(cors.Config{
+		AllowOrigins: "*",
+		AllowMethods: "GET,POST,PUT,DELETE,OPTIONS",
+		AllowHeaders: "Origin,Content-Type,Accept",
+	}))
+
+	// Health check (no rate limit)
+	app.Get("/health", h.Health)
+
+	// API v1 routes with rate limiting
+	api := app.Group("/api/v1")
+
+	// Rate limiter: 10/20 req/sec per IP with expiry
+	maxReq := rateLimitRate
+	if devMode {
+		maxReq = rateLimitRate * 2 // Loosen rate limiter for testing
+	}
+	api.Use(limiter.New(limiter.Config{
+		Max:        maxReq,          // Allow requests per second
+		Expiration: 1 * time.Second, // Per second
+		KeyGenerator: func(c *fiber.Ctx) string {
+			// Check X-Forwarded-For first, then X-Real-IP, then RemoteIP
+			if xff := c.Get("X-Forwarded-For"); xff != "" {
+				// Take the first IP from X-Forwarded-For chain
+				if idx := strings.Index(xff, ","); idx != -1 {
+					return strings.TrimSpace(xff[:idx])
+				}
+				return xff
+			}
+			return c.IP()
+		},
+		LimitReached: func(c *fiber.Ctx) error {
+			return c.Status(fiber.StatusTooManyRequests).JSON(core.ErrorResponse{
+				Error:   "rate limit exceeded",
+				Code:    core.ErrRateLimitExceeded,
+				Details: fmt.Sprintf("%d requests per second allowed", maxReq),
+			})
+		},
+		Storage:                nil, // Use in-memory storage (default)
+		SkipFailedRequests:     false,
+		SkipSuccessfulRequests: false,
+	}))
+
+	// Content-Type validation for POST and PUT requests
+	api.Use(contentTypeValidator)
+
+	// Middleware validation for sanitization
+	api.Use(validationMiddleware)
+
+	// Register game routes
+	api.Post("/games", h.CreateGame)
+	api.Put("/games/:gameId/players", h.ConfigurePlayers)
+	api.Get("/games/:gameId", h.GetGame)
+	api.Delete("/games/:gameId", h.DeleteGame)
+	api.Post("/games/:gameId/moves", h.MakeMove)
+	api.Post("/games/:gameId/undo", h.UndoMove)
+	api.Get("/games/:gameId/board", h.GetBoard)
+
+	return app
+}
+
+// contentTypeValidator ensures POST and PUT requests have application/json
+func contentTypeValidator(c *fiber.Ctx) error {
+	method := c.Method()
+	if method == fiber.MethodPost || method == fiber.MethodPut {
+		contentType := c.Get("Content-Type")
+		if contentType != "application/json" && contentType != "" {
+			return c.Status(fiber.StatusUnsupportedMediaType).JSON(core.ErrorResponse{
+				Error:   "unsupported media type",
+				Code:    core.ErrInvalidContent,
+				Details: "Content-Type must be application/json",
+			})
+		}
+	}
+	return c.Next()
+}
+
+// customErrorHandler provides consistent error responses
+func customErrorHandler(c *fiber.Ctx, err error) error {
+	code := fiber.StatusInternalServerError
+	response := core.ErrorResponse{
+		Error: "internal server error",
+		Code:  core.ErrInternalError,
+	}
+
+	// Check if it's a Fiber error
+	if e, ok := err.(*fiber.Error); ok {
+		code = e.Code
+		response.Error = e.Message
+
+		// Map HTTP status to error codes
+		switch code {
+		case fiber.StatusNotFound:
+			response.Code = core.ErrGameNotFound
+		case fiber.StatusBadRequest:
+			response.Code = core.ErrInvalidRequest
+		case fiber.StatusTooManyRequests:
+			response.Code = core.ErrRateLimitExceeded
+		}
+	}
+
+	return c.Status(code).JSON(response)
+}
+
+// Health check endpoint
+func (h *HTTPHandler) Health(c *fiber.Ctx) error {
+	return c.JSON(fiber.Map{
+		"status": "healthy",
+		"time":   time.Now().Unix(),
+	})
+}
+
+// CreateGame creates a new game with specified player types
+func (h *HTTPHandler) CreateGame(c *fiber.Ctx) error {
+	// Ensure middleware validation ran
+	validated, ok := c.Locals("validated").(bool)
+	if !ok || !validated {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation bypass detected",
+			Code:  core.ErrInternalError,
+		})
+	}
+
+	// Retrieve validated parsed body
+	validatedBody := c.Locals("validatedBody")
+	if validatedBody == nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation data missing",
+			Code:  core.ErrInternalError,
+		})
+	}
+	var req core.CreateGameRequest
+	req = *(validatedBody.(*core.CreateGameRequest))
+
+	// Let processor generate game ID via service
+	cmd := processor.NewCreateGameCommand(req)
+
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		return c.Status(fiber.StatusBadRequest).JSON(resp.Error)
+	}
+
+	return c.Status(fiber.StatusCreated).JSON(resp.Data)
+}
+
+// ConfigurePlayers updates player configuration mid-game
+func (h *HTTPHandler) ConfigurePlayers(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Ensure middleware validation ran
+	validated, ok := c.Locals("validated").(bool)
+	if !ok || !validated {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation bypass detected",
+			Code:  core.ErrInternalError,
+		})
+	}
+
+	// Retrieve validated parsed body
+	validatedBody := c.Locals("validatedBody")
+	if validatedBody == nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation data missing",
+			Code:  core.ErrInternalError,
+		})
+	}
+	var req core.ConfigurePlayersRequest
+	req = *(validatedBody.(*core.ConfigurePlayersRequest))
+
+	// Create command and execute
+	cmd := processor.NewConfigurePlayersCommand(gameID, req)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		statusCode := fiber.StatusBadRequest
+		if resp.Error.Code == core.ErrGameNotFound {
+			statusCode = fiber.StatusNotFound
+		}
+		return c.Status(statusCode).JSON(resp.Error)
+	}
+
+	return c.JSON(resp.Data)
+}
+
+// GetGame retrieves current game state
+func (h *HTTPHandler) GetGame(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Create command and execute
+	cmd := processor.NewGetGameCommand(gameID)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		return c.Status(fiber.StatusNotFound).JSON(resp.Error)
+	}
+
+	return c.JSON(resp.Data)
+}
+
+// MakeMove submits a move
+func (h *HTTPHandler) MakeMove(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Ensure middleware validation ran
+	validated, ok := c.Locals("validated").(bool)
+	if !ok || !validated {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation bypass detected",
+			Code:  core.ErrInternalError,
+		})
+	}
+
+	// Retrieve validated parsed body
+	validatedBody := c.Locals("validatedBody")
+	if validatedBody == nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation data missing",
+			Code:  core.ErrInternalError,
+		})
+	}
+	var req core.MoveRequest
+	req = *(validatedBody.(*core.MoveRequest))
+
+	// Create command and execute
+	cmd := processor.NewMakeMoveCommand(gameID, req)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response with correct status code
+	if !resp.Success {
+		statusCode := fiber.StatusBadRequest
+		if resp.Error.Code == core.ErrGameNotFound {
+			statusCode = fiber.StatusNotFound
+		}
+		return c.Status(statusCode).JSON(resp.Error)
+	}
+
+	return c.JSON(resp.Data)
+}
+
+// UndoMove undoes one or more moves
+func (h *HTTPHandler) UndoMove(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Ensure middleware validation ran
+	validated, ok := c.Locals("validated").(bool)
+	if !ok || !validated {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation bypass detected",
+			Code:  core.ErrInternalError,
+		})
+	}
+
+	// Retrieve validated parsed body
+	validatedBody := c.Locals("validatedBody")
+	if validatedBody == nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(core.ErrorResponse{
+			Error: "validation data missing",
+			Code:  core.ErrInternalError,
+		})
+	}
+	var req core.UndoRequest
+	req = *(validatedBody.(*core.UndoRequest))
+
+	// Create command and execute
+	cmd := processor.NewUndoMoveCommand(gameID, req)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		statusCode := fiber.StatusBadRequest
+		if resp.Error.Code == core.ErrGameNotFound {
+			statusCode = fiber.StatusNotFound
+		}
+		return c.Status(statusCode).JSON(resp.Error)
+	}
+
+	return c.JSON(resp.Data)
+}
+
+// DeleteGame ends and cleans up a game
+func (h *HTTPHandler) DeleteGame(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Create command and execute
+	cmd := processor.NewDeleteGameCommand(gameID)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		return c.Status(fiber.StatusNotFound).JSON(resp.Error)
+	}
+
+	return c.SendStatus(fiber.StatusNoContent)
+}
+
+// GetBoard returns ASCII representation of the board
+func (h *HTTPHandler) GetBoard(c *fiber.Ctx) error {
+	gameID := c.Params("gameId")
+
+	// Validate UUID format
+	if !isValidUUID(gameID) {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid game ID format",
+			Code:    core.ErrInvalidRequest,
+			Details: "game ID must be a valid UUID",
+		})
+	}
+
+	// Create command and execute
+	cmd := processor.NewGetBoardCommand(gameID)
+	resp := h.proc.Execute(cmd)
+
+	// Return appropriate HTTP response
+	if !resp.Success {
+		return c.Status(fiber.StatusNotFound).JSON(resp.Error)
+	}
+
+	return c.JSON(resp.Data)
+}
--- a/internal/http/validator.go
+++ b/internal/http/validator.go
@ -0,0 +1,103 @@
+// FILE: internal/http/handler.go
+package http
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"chess/internal/core"
+
+	"github.com/go-playground/validator/v10"
+	"github.com/gofiber/fiber/v2"
+	"github.com/google/uuid"
+)
+
+// Add validator instance near top of file
+var validate = validator.New()
+
+// Add custom validation middleware function
+func validationMiddleware(c *fiber.Ctx) error {
+	// Skip validation for GET, DELETE, OPTIONS
+	method := c.Method()
+	if method == fiber.MethodGet || method == fiber.MethodDelete || method == fiber.MethodOptions {
+		return c.Next()
+	}
+
+	// Determine request type based on path
+	path := c.Path()
+	var requestType interface{}
+
+	switch {
+	case strings.HasSuffix(path, "/games") && method == fiber.MethodPost:
+		requestType = &core.CreateGameRequest{}
+	case strings.HasSuffix(path, "/players") && method == fiber.MethodPut:
+		requestType = &core.ConfigurePlayersRequest{}
+	case strings.HasSuffix(path, "/moves") && method == fiber.MethodPost:
+		requestType = &core.MoveRequest{}
+	case strings.HasSuffix(path, "/undo") && method == fiber.MethodPost:
+		requestType = &core.UndoRequest{}
+	default:
+		return c.Next() // No validation for unknown endpoints
+	}
+
+	// Parse body
+	if err := c.BodyParser(requestType); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "invalid request body",
+			Code:    core.ErrInvalidRequest,
+			Details: err.Error(),
+		})
+	}
+
+	// Validate
+	if errs := validate.Struct(requestType); errs != nil {
+		var details strings.Builder
+		for _, err := range errs.(validator.ValidationErrors) {
+			if details.Len() > 0 {
+				details.WriteString("; ")
+			}
+			switch err.Tag() {
+			case "required":
+				details.WriteString(fmt.Sprintf("%s is required", err.Field()))
+			case "oneof":
+				details.WriteString(fmt.Sprintf("%s must be one of [%s]", err.Field(), err.Param()))
+			case "min":
+				if err.Type().Kind() == reflect.String {
+					details.WriteString(fmt.Sprintf("%s must be at least %s characters", err.Field(), err.Param()))
+				} else {
+					details.WriteString(fmt.Sprintf("%s must be at least %s", err.Field(), err.Param()))
+				}
+			case "max":
+				if err.Type().Kind() == reflect.String {
+					details.WriteString(fmt.Sprintf("%s must be at most %s characters", err.Field(), err.Param()))
+				} else {
+					details.WriteString(fmt.Sprintf("%s must be at most %s", err.Field(), err.Param()))
+				}
+			case "omitempty": // Skip, a control tag that doesn't error
+				continue
+			case "dive": // Skip, panics on wrong type, no error handling since current code does not call validator on slice or map
+				continue
+			default:
+				details.WriteString(fmt.Sprintf("%s failed %s validation", err.Field(), err.Tag()))
+			}
+		}
+
+		return c.Status(fiber.StatusBadRequest).JSON(core.ErrorResponse{
+			Error:   "validation failed",
+			Code:    core.ErrInvalidRequest,
+			Details: details.String(),
+		})
+	}
+
+	// Store validated body for handler use
+	c.Locals("validatedBody", requestType)
+	c.Locals("validated", true)
+
+	return c.Next()
+}
+
+func isValidUUID(s string) bool {
+	_, err := uuid.Parse(s)
+	return err == nil
+}
--- a/internal/processor/command.go
+++ b/internal/processor/command.go
@ -0,0 +1,86 @@
+// FILE: internal/processor/command.go
+package processor
+
+import (
+	"chess/internal/core"
+)
+
+// CommandType defines the type of command being executed
+type CommandType int
+
+const (
+	CmdCreateGame CommandType = iota
+	CmdConfigurePlayers
+	CmdGetGame
+	CmdDeleteGame
+	CmdMakeMove
+	CmdUndoMove
+	CmdGetBoard
+)
+
+// Command is a unified structure for all processor operations
+type Command struct {
+	Type   CommandType
+	GameID string      // For game-specific commands
+	Args   interface{} // Command-specific arguments
+}
+
+// ProcessorResponse wraps the response with metadata
+type ProcessorResponse struct {
+	Success bool                `json:"success"`
+	Pending bool                `json:"pending,omitempty"` // For async operations
+	Data    interface{}         `json:"data,omitempty"`
+	Error   *core.ErrorResponse `json:"error,omitempty"`
+}
+
+func NewCreateGameCommand(req core.CreateGameRequest) Command {
+	return Command{
+		Type: CmdCreateGame,
+		Args: req,
+	}
+}
+
+func NewConfigurePlayersCommand(gameID string, req core.ConfigurePlayersRequest) Command {
+	return Command{
+		Type:   CmdConfigurePlayers,
+		GameID: gameID,
+		Args:   req,
+	}
+}
+
+func NewGetGameCommand(gameID string) Command {
+	return Command{
+		Type:   CmdGetGame,
+		GameID: gameID,
+	}
+}
+
+func NewMakeMoveCommand(gameID string, req core.MoveRequest) Command {
+	return Command{
+		Type:   CmdMakeMove,
+		GameID: gameID,
+		Args:   req,
+	}
+}
+
+func NewUndoMoveCommand(gameID string, req core.UndoRequest) Command {
+	return Command{
+		Type:   CmdUndoMove,
+		GameID: gameID,
+		Args:   req,
+	}
+}
+
+func NewDeleteGameCommand(gameID string) Command {
+	return Command{
+		Type:   CmdDeleteGame,
+		GameID: gameID,
+	}
+}
+
+func NewGetBoardCommand(gameID string) Command {
+	return Command{
+		Type:   CmdGetBoard,
+		GameID: gameID,
+	}
+}
--- a/internal/processor/processor.go
+++ b/internal/processor/processor.go
@ -0,0 +1,565 @@
+// FILE: internal/processor/processor.go
+
+package processor
+
+import (
+	"fmt"
+	"log"
+	"regexp"
+	"strings"
+	"sync"
+	"time"
+	"unicode"
+
+	"chess/internal/board"
+	"chess/internal/core"
+	"chess/internal/engine"
+	"chess/internal/game"
+	"chess/internal/service"
+)
+
+const (
+	minSearchTime = 100
+)
+
+// FEN validation regex
+var fenPattern = regexp.MustCompile(`^[rnbqkpRNBQKP1-8/]+ [wb] [KQkq-]+ [a-h1-8-]+ \d+ \d+$`)
+
+// Processor orchestrates all game logic and engine interactions
+type Processor struct {
+	svc           *service.Service
+	queue         *EngineQueue
+	validationEng *engine.UCI // For synchronous move validation
+	mu            sync.RWMutex
+}
+
+// New creates a processor with its own engine instances
+func New(svc *service.Service) (*Processor, error) {
+	// Create validation engine
+	validationEng, err := engine.New()
+	if err != nil {
+		return nil, fmt.Errorf("failed to create validation engine: %v", err)
+	}
+
+	return &Processor{
+		svc:           svc,
+		queue:         NewEngineQueue(2), // 2 workers for computer moves
+		validationEng: validationEng,
+	}, nil
+}
+
+func (p *Processor) Execute(cmd Command) ProcessorResponse {
+	switch cmd.Type {
+	case CmdCreateGame:
+		return p.handleCreateGame(cmd)
+	case CmdConfigurePlayers:
+		return p.handleConfigurePlayers(cmd)
+	case CmdGetGame:
+		return p.handleGetGame(cmd)
+	case CmdMakeMove:
+		return p.handleMakeMove(cmd)
+	case CmdUndoMove:
+		return p.handleUndoMove(cmd)
+	case CmdDeleteGame:
+		return p.handleDeleteGame(cmd)
+	case CmdGetBoard:
+		return p.handleGetBoard(cmd)
+	default:
+		return p.errorResponse("unknown command", core.ErrInvalidRequest)
+	}
+}
+
+// isFENSafe check for control characters that could inject UCI commands and FEN pattern match
+func (p *Processor) isFENSafe(fen string) bool {
+	// Check for control characters
+	for _, r := range fen {
+		if unicode.IsControl(r) && r != ' ' {
+			return false
+		}
+	}
+
+	// Validate FEN format
+	return fenPattern.MatchString(fen)
+}
+
+func (p *Processor) isMoveSafe(move string) bool {
+	// Check for control characters
+	for _, r := range move {
+		if unicode.IsControl(r) {
+			return false
+		}
+	}
+
+	// UCI valid moves are 4-5 characters only
+	// Examples: e2e4 / e1g1 (castle) / a7a8q (promotion)
+	// UCI moves: [a-h][1-8][a-h][1-8][qrbn]?
+	if len(move) < 4 || len(move) > 5 {
+		return false
+	}
+
+	// Check each character
+	if move[0] < 'a' || move[0] > 'h' ||
+		move[1] < '1' || move[1] > '8' ||
+		move[2] < 'a' || move[2] > 'h' ||
+		move[3] < '1' || move[3] > '8' {
+		return false
+	}
+
+	// Promotion piece if present
+	if len(move) == 5 {
+		promotion := move[4]
+		if promotion != 'q' && promotion != 'r' && promotion != 'b' && promotion != 'n' {
+			return false
+		}
+	}
+
+	return true
+}
+
+// handleCreateGame creates a new game and triggers computer move if needed
+func (p *Processor) handleCreateGame(cmd Command) ProcessorResponse {
+	args, ok := cmd.Args.(core.CreateGameRequest)
+	if !ok {
+		return p.errorResponse("invalid arguments", core.ErrInvalidRequest)
+	}
+
+	// Enforce minimum searchTime for computer players
+	if args.White.Type == core.PlayerComputer && args.White.SearchTime < 100 {
+		args.White.SearchTime = minSearchTime
+	}
+	if args.Black.Type == core.PlayerComputer && args.Black.SearchTime < 100 {
+		args.Black.SearchTime = minSearchTime
+	}
+
+	// Generate game ID
+	gameID := p.svc.GenerateGameID()
+
+	// Validate and canonicalize FEN if provided
+	initialFEN := board.StartingFEN
+	if args.FEN != "" {
+		if !p.isFENSafe(args.FEN) {
+			return p.errorResponse("invalid FEN format or characters", core.ErrInvalidFEN)
+		}
+		initialFEN = args.FEN
+	}
+
+	p.mu.Lock()
+	p.validationEng.NewGame()
+	p.validationEng.SetPosition(initialFEN, []string{})
+	validatedFEN, err := p.validationEng.GetFEN()
+	p.mu.Unlock()
+
+	if err != nil {
+		return p.errorResponse(fmt.Sprintf("invalid FEN: %v", err), core.ErrInvalidRequest)
+	}
+
+	// Parse to get starting turn
+	b, err := board.ParseFEN(validatedFEN)
+	if err != nil {
+		return p.errorResponse(fmt.Sprintf("FEN parse error: %v", err), core.ErrInvalidRequest)
+	}
+
+	// Create game in service with validated FEN and turn
+	if err = p.svc.CreateGame(gameID, args.White, args.Black, validatedFEN, b.Turn()); err != nil {
+		return p.errorResponse(fmt.Sprintf("failed to create game: %v", err), core.ErrInternalError)
+	}
+
+	// Check if the initial FEN represents a completed game
+	p.checkGameEnd(gameID, validatedFEN, core.OppositeColor(b.Turn()))
+
+	// Get created game
+	g, err := p.svc.GetGame(gameID)
+	if err != nil {
+		return p.errorResponse("game creation failed", core.ErrInternalError)
+	}
+
+	// Build response
+	response := p.buildGameResponse(gameID, g)
+
+	return ProcessorResponse{
+		Success: true,
+		Data:    response,
+	}
+}
+
+// handleConfigurePlayers updates player configuration mid-game
+func (p *Processor) handleConfigurePlayers(cmd Command) ProcessorResponse {
+	args, ok := cmd.Args.(core.ConfigurePlayersRequest)
+	if !ok {
+		return p.errorResponse("invalid arguments", core.ErrInvalidRequest)
+	}
+
+	if args.White.Type == core.PlayerComputer && args.White.SearchTime < 100 {
+		args.White.SearchTime = minSearchTime
+	}
+	if args.Black.Type == core.PlayerComputer && args.Black.SearchTime < 100 {
+		args.Black.SearchTime = minSearchTime
+	}
+
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	// Block configuration changes during computer move
+	if g.State() == core.StatePending {
+		return p.errorResponse("cannot change players while computer is calculating", core.ErrInvalidRequest)
+	}
+
+	// Update players in service
+	if err = p.svc.UpdatePlayers(cmd.GameID, args.White, args.Black); err != nil {
+		return p.errorResponse(fmt.Sprintf("failed to update players: %v", err), core.ErrInternalError)
+	}
+
+	// Get updated game
+	g, _ = p.svc.GetGame(cmd.GameID)
+	response := p.buildGameResponse(cmd.GameID, g)
+
+	return ProcessorResponse{
+		Success: true,
+		Data:    response,
+	}
+}
+
+// handleGetGame retrieves game state and triggers computer move if needed
+func (p *Processor) handleGetGame(cmd Command) ProcessorResponse {
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	response := p.buildGameResponse(cmd.GameID, g)
+
+	return ProcessorResponse{
+		Success: true,
+		Data:    response,
+	}
+}
+
+// handleMakeMove processes human moves
+func (p *Processor) handleMakeMove(cmd Command) ProcessorResponse {
+	args, ok := cmd.Args.(core.MoveRequest)
+	if !ok {
+		return p.errorResponse("invalid arguments", core.ErrInvalidRequest)
+	}
+
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	// Validate game state
+	switch g.State() {
+	case core.StatePending:
+		return p.errorResponse("computer move in progress", core.ErrInvalidRequest)
+	case core.StateStuck:
+		return p.errorResponse("game is stuck due to engine error", core.ErrGameOver)
+	case core.StateWhiteWins, core.StateBlackWins, core.StateDraw, core.StateStalemate:
+		return p.errorResponse(fmt.Sprintf("game is over: %s", g.State()), core.ErrGameOver)
+	case core.StateOngoing:
+		break
+	default:
+		return p.errorResponse("game is in invalid state", core.ErrInvalidRequest)
+	}
+
+	// Handle empty move string - trigger computer move
+	if strings.TrimSpace(args.Move) == "cccc" {
+		if g.NextPlayer().Type != core.PlayerComputer {
+			return p.errorResponse("not computer player's turn", core.ErrNotHumanTurn)
+		}
+
+		// Set state to pending and trigger computer move
+		p.svc.UpdateGameState(cmd.GameID, core.StatePending)
+		p.triggerComputerMove(cmd.GameID, g)
+
+		// Re-fetch for updated state
+		g, _ = p.svc.GetGame(cmd.GameID)
+		response := p.buildGameResponse(cmd.GameID, g)
+		response.LastMove = &core.MoveInfo{
+			PlayerColor: g.NextTurnColor().String(),
+		}
+
+		return ProcessorResponse{
+			Success: true,
+			Pending: true,
+			Data:    response,
+		}
+	}
+
+	// Handle human move
+	if g.NextPlayer().Type != core.PlayerHuman {
+		return p.errorResponse("not human player's turn", core.ErrNotHumanTurn)
+	}
+
+	// Normalize and validate move format
+	move := strings.ToLower(strings.TrimSpace(args.Move))
+	if !p.isMoveSafe(move) {
+		return p.errorResponse("invalid move format", core.ErrInvalidMove)
+	}
+
+	currentFEN := g.CurrentFEN()
+	currentColor := g.NextTurnColor()
+
+	// Validate move with engine
+	p.mu.Lock()
+	p.validationEng.SetPosition(currentFEN, []string{move})
+	newFEN, err := p.validationEng.GetFEN()
+	p.mu.Unlock()
+
+	if err != nil || newFEN == currentFEN {
+		return p.errorResponse("illegal move", core.ErrInvalidMove)
+	}
+
+	// Apply move to game state via service
+	if err = p.svc.ApplyMove(cmd.GameID, move, newFEN); err != nil {
+		return p.errorResponse(fmt.Sprintf("failed to apply move: %v", err), core.ErrInternalError)
+	}
+
+	// Store move result metadata
+	p.svc.SetLastMoveResult(cmd.GameID, &game.MoveResult{
+		Move:        move,
+		PlayerColor: currentColor,
+		GameState:   core.StateOngoing,
+	})
+
+	// Check for checkmate/stalemate
+	p.checkGameEnd(cmd.GameID, newFEN, currentColor)
+
+	// Get updated game
+	g, _ = p.svc.GetGame(cmd.GameID)
+	response := p.buildGameResponse(cmd.GameID, g)
+
+	// Add human move info
+	response.LastMove = &core.MoveInfo{
+		Move:        move,
+		PlayerColor: currentColor.String(),
+	}
+
+	return ProcessorResponse{
+		Success: true,
+		Data:    response,
+	}
+}
+
+// handleUndoMove reverts game state
+func (p *Processor) handleUndoMove(cmd Command) ProcessorResponse {
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	// Check game state
+	switch g.State() {
+	case core.StatePending:
+		return p.errorResponse("cannot undo while computer move is in progress", core.ErrInvalidRequest)
+	case core.StateStuck:
+		return p.errorResponse("cannot undo in stuck game", core.ErrInvalidRequest)
+	}
+
+	args := core.UndoRequest{Count: 1}
+	if cmd.Args != nil {
+		if req, ok := cmd.Args.(core.UndoRequest); ok {
+			args = req
+		}
+	}
+
+	if err = p.svc.UndoMoves(cmd.GameID, args.Count); err != nil {
+		if strings.Contains(err.Error(), "not found") {
+			return p.errorResponse("game not found", core.ErrGameNotFound)
+		}
+		return p.errorResponse(err.Error(), core.ErrInvalidRequest)
+	}
+
+	// Reset game state to ongoing after undo
+	p.svc.UpdateGameState(cmd.GameID, core.StateOngoing)
+
+	g, _ = p.svc.GetGame(cmd.GameID)
+	response := p.buildGameResponse(cmd.GameID, g)
+
+	return ProcessorResponse{
+		Success: true,
+		Data:    response,
+	}
+}
+
+// handleDeleteGame removes a game
+func (p *Processor) handleDeleteGame(cmd Command) ProcessorResponse {
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	// TODO: gracefully handle deleting game even if pending, discard engine response
+	// Only block deletion if actively computing
+	if g.State() == core.StatePending {
+		return p.errorResponse("cannot delete game while computer move is in progress", core.ErrInvalidRequest)
+	}
+
+	if err = p.svc.DeleteGame(cmd.GameID); err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	return ProcessorResponse{
+		Success: true,
+	}
+}
+
+// handleGetBoard returns board visualization
+func (p *Processor) handleGetBoard(cmd Command) ProcessorResponse {
+	g, err := p.svc.GetGame(cmd.GameID)
+	if err != nil {
+		return p.errorResponse("game not found", core.ErrGameNotFound)
+	}
+
+	b, err := board.ParseFEN(g.CurrentFEN())
+	if err != nil {
+		return p.errorResponse("error parsing FEN", core.ErrInvalidFEN)
+	}
+	ascii := b.ToASCII()
+
+	return ProcessorResponse{
+		Success: true,
+		Data: core.BoardResponse{
+			FEN:   g.CurrentFEN(),
+			Board: ascii,
+		},
+	}
+}
+
+// triggerComputerMove initiates async engine calculation
+func (p *Processor) triggerComputerMove(gameID string, g *game.Game) {
+	fen := g.CurrentFEN()
+	color := g.NextTurnColor()
+	player := g.NextPlayer()
+
+	// Submit to queue with callback and computer config
+	p.queue.SubmitAsync(gameID, fen, color, player, func(result EngineResult) {
+		// Check if game still exists
+		currentGame, err := p.svc.GetGame(gameID)
+		if err != nil {
+			return // Game was deleted
+		}
+
+		// Only process if still in pending state
+		if currentGame.State() != core.StatePending {
+			return
+		}
+
+		if result.Error != nil {
+			log.Printf("Engine error for game %s: %v", gameID, result.Error)
+			p.svc.UpdateGameState(gameID, core.StateStuck)
+			return
+		}
+
+		// Use centralized state determination
+		state := p.determineGameEndState(core.OppositeColor(color), &engine.SearchResult{
+			BestMove: result.Move,
+			Score:    result.Score,
+			Depth:    result.Depth,
+			IsMate:   result.IsMate,
+			MateIn:   result.MateIn,
+		})
+
+		if state != core.StateOngoing {
+			p.svc.UpdateGameState(gameID, state)
+			return
+		}
+
+		// Apply computer move
+		p.mu.Lock()
+		p.validationEng.SetPosition(fen, []string{result.Move})
+		newFEN, _ := p.validationEng.GetFEN()
+		p.mu.Unlock()
+
+		p.svc.ApplyMove(gameID, result.Move, newFEN)
+		p.svc.SetLastMoveResult(gameID, &game.MoveResult{
+			Move:        result.Move,
+			PlayerColor: color,
+			Score:       result.Score,
+			Depth:       result.Depth,
+		})
+
+		// Reset to ongoing first
+		p.svc.UpdateGameState(gameID, core.StateOngoing)
+
+		// Check if opponent is checkmated
+		p.checkGameEnd(gameID, newFEN, color)
+	})
+}
+
+// determineGameEndState centralized function to determine game end state based on engine evaluation
+func (p *Processor) determineGameEndState(lastMoveBy core.Color, searchResult *engine.SearchResult) core.State {
+	// No legal moves detected
+	if searchResult.BestMove == "" || searchResult.BestMove == "(none)" {
+		if searchResult.IsMate {
+			// It's a checkmate - the side that just moved wins
+			if lastMoveBy == core.ColorWhite {
+				return core.StateWhiteWins
+			}
+			return core.StateBlackWins
+		}
+		// Stalemate - no legal moves but not in check
+		return core.StateStalemate
+	}
+
+	// Game continues
+	return core.StateOngoing
+}
+
+// checkGameEnd determines if game has ended
+func (p *Processor) checkGameEnd(gameID, fen string, lastMoveBy core.Color) {
+	p.mu.Lock()
+	p.validationEng.SetPosition(fen, []string{})
+	search, _ := p.validationEng.Search(100)
+	p.mu.Unlock()
+
+	// Use centralized state determination
+	state := p.determineGameEndState(lastMoveBy, search)
+	if state != core.StateOngoing {
+		p.svc.UpdateGameState(gameID, state)
+	}
+}
+
+// buildGameResponse constructs standard game response
+func (p *Processor) buildGameResponse(gameID string, g *game.Game) core.GameResponse {
+	resp := core.GameResponse{
+		GameID: gameID,
+		FEN:    g.CurrentFEN(),
+		Turn:   g.NextTurnColor().String(),
+		State:  g.State().String(),
+		Moves:  g.Moves(),
+		Players: core.PlayersResponse{
+			White: g.GetPlayer(core.ColorWhite),
+			Black: g.GetPlayer(core.ColorBlack),
+		},
+	}
+
+	// Include last move if available
+	if result := g.LastResult(); result != nil {
+		resp.LastMove = &core.MoveInfo{
+			Move:        result.Move,
+			PlayerColor: result.PlayerColor.String(),
+			Score:       result.Score,
+			Depth:       result.Depth,
+		}
+	}
+
+	return resp
+}
+
+// errorResponse creates error response
+func (p *Processor) errorResponse(message, code string) ProcessorResponse {
+	return ProcessorResponse{
+		Success: false,
+		Error: &core.ErrorResponse{
+			Error: message,
+			Code:  code,
+		},
+	}
+}
+
+// Close cleans up resources
+func (p *Processor) Close() error {
+	p.queue.Shutdown(5 * time.Second)
+	return p.validationEng.Close()
+}
--- a/internal/processor/queue.go
+++ b/internal/processor/queue.go
@ -0,0 +1,209 @@
+// FILE: internal/processor/queue.go
+package processor
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"chess/internal/core"
+	"chess/internal/engine"
+)
+
+// EngineTask represents a computer move calculation request
+type EngineTask struct {
+	GameID   string
+	FEN      string
+	Color    core.Color
+	Player   *core.Player // Full player config including engine configuration
+	Response chan<- EngineResult
+}
+
+// EngineResult contains the outcome of an engine calculation
+type EngineResult struct {
+	GameID string
+	Move   string
+	Score  int
+	Depth  int
+	IsMate bool
+	MateIn int
+	Error  error
+}
+
+// EngineQueue manages async engine computations
+type EngineQueue struct {
+	tasks   chan EngineTask
+	workers int
+	wg      sync.WaitGroup
+	ctx     context.Context
+	cancel  context.CancelFunc
+}
+
+// NewEngineQueue creates a queue with specified worker count
+func NewEngineQueue(workerCount int) *EngineQueue {
+	if workerCount < 1 {
+		workerCount = 2 // Default
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	q := &EngineQueue{
+		tasks:   make(chan EngineTask, 100), // Buffered for queueing
+		workers: workerCount,
+		ctx:     ctx,
+		cancel:  cancel,
+	}
+
+	q.start()
+	return q
+}
+
+// start initializes the worker pool
+func (q *EngineQueue) start() {
+	for i := 0; i < q.workers; i++ {
+		q.wg.Add(1)
+		go q.worker(i)
+	}
+}
+
+// worker processes engine tasks
+func (q *EngineQueue) worker(id int) {
+	defer q.wg.Done()
+
+	// Each worker gets its own engine instance
+	eng, err := engine.New()
+	if err != nil {
+		fmt.Printf("Worker %d failed to initialize engine: %v\n", id, err)
+		return
+	}
+	defer eng.Close()
+
+	for {
+		select {
+		case task, ok := <-q.tasks:
+			if !ok {
+				return // Channel closed
+			}
+
+			result := q.processTask(eng, task)
+
+			// Send result if receiver still listening
+			select {
+			case task.Response <- result:
+			case <-time.After(100 * time.Millisecond):
+				// Receiver abandoned, discard result
+			}
+
+		case <-q.ctx.Done():
+			return
+		}
+	}
+}
+
+// processTask executes a single engine calculation
+func (q *EngineQueue) processTask(eng *engine.UCI, task EngineTask) EngineResult {
+	result := EngineResult{
+		GameID: task.GameID,
+	}
+
+	// Apply computer configuration if provided
+	if task.Player.Type == core.PlayerComputer {
+		eng.SetSkillLevel(task.Player.Level)
+	}
+
+	// Setup position
+	eng.SetPosition(task.FEN, []string{})
+
+	// Determine search time
+	searchTime := 1000 // Default 1 second
+	if task.Player.Type == core.PlayerComputer && task.Player.SearchTime > 0 {
+		searchTime = task.Player.SearchTime
+	}
+
+	// Search for best move
+	search, err := eng.Search(searchTime)
+	if err != nil {
+		result.Error = fmt.Errorf("engine search failed: %v", err)
+		return result
+	}
+
+	// Check for no legal moves
+	if search.BestMove == "" || search.BestMove == "(none)" {
+		result.Move = ""
+		result.IsMate = search.IsMate
+		result.MateIn = search.MateIn
+		return result
+	}
+
+	result.Move = search.BestMove
+	result.Score = search.Score
+	result.Depth = search.Depth
+	result.IsMate = search.IsMate
+	result.MateIn = search.MateIn
+
+	return result
+}
+
+// Submit adds a task to the queue
+func (q *EngineQueue) Submit(task EngineTask) error {
+	select {
+	case q.tasks <- task:
+		return nil
+	case <-q.ctx.Done():
+		return fmt.Errorf("queue is shutting down")
+	default:
+		return fmt.Errorf("queue is full")
+	}
+}
+
+// SubmitAsync submits a task without blocking for result
+func (q *EngineQueue) SubmitAsync(gameID, fen string, color core.Color, player *core.Player, callback func(EngineResult)) error {
+	respChan := make(chan EngineResult, 1)
+
+	task := EngineTask{
+		GameID:   gameID,
+		FEN:      fen,
+		Color:    color,
+		Player:   player,
+		Response: respChan,
+	}
+
+	if err := q.Submit(task); err != nil {
+		return err
+	}
+
+	// Handle result in background
+	go func() {
+		select {
+		case result := <-respChan:
+			callback(result)
+		case <-time.After(5 * time.Second):
+			callback(EngineResult{
+				GameID: gameID,
+				Error:  fmt.Errorf("engine timeout"),
+			})
+		}
+	}()
+
+	return nil
+}
+
+// Shutdown gracefully stops the queue
+func (q *EngineQueue) Shutdown(timeout time.Duration) error {
+	q.cancel()
+	close(q.tasks)
+
+	done := make(chan struct{})
+	go func() {
+		q.wg.Wait()
+		close(done)
+	}()
+
+	select {
+	case <-done:
+		return nil
+	case <-time.After(timeout):
+		return fmt.Errorf("shutdown timeout exceeded")
+	}
+}
--- a/internal/service/service.go
+++ b/internal/service/service.go
@ -3,202 +3,137 @@ package service

 import (
 	"fmt"
-	"strings"
+	"sync"

-	"chess/internal/board"
 	"chess/internal/core"
-	"chess/internal/engine"
 	"chess/internal/game"
+
+	"github.com/google/uuid"
 )

+// Service is a pure state manager for chess games
+// It has NO knowledge of chess rules or engine interactions
 type Service struct {
-	games  map[string]*game.Game
-	engine *engine.UCI
+	games map[string]*game.Game
+	mu    sync.RWMutex
 }

+// New creates a new service instance
 func New() (*Service, error) {
-	eng, err := engine.New()
-	if err != nil {
-		return nil, fmt.Errorf("failed to initialize engine: %v", err)
-	}
-
 	return &Service{
-		games:  make(map[string]*game.Game),
-		engine: eng,
+		games: make(map[string]*game.Game),
 	}, nil
 }

-func (s *Service) NewGame(id string, whiteType, blackType core.PlayerType, fen ...string) error {
-	initialFEN := board.StartingFEN
-	if len(fen) > 0 && fen[0] != "" {
-		initialFEN = fen[0]
+// CreateGame creates game with player configuration
+func (s *Service) CreateGame(id string, whiteConfig, blackConfig core.PlayerConfig, initialFEN string, startingTurn core.Color) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if _, exists := s.games[id]; exists {
+		return fmt.Errorf("game %s already exists", id)
 	}

-	// Use the engine to validate and canonicalize the FEN
-	s.engine.NewGame()
-	s.engine.SetPosition(initialFEN, []string{})
-	validatedFEN, err := s.engine.GetFEN()
-	if err != nil {
-		return fmt.Errorf("could not get FEN from engine: %v", err)
-	}
-
-	b, err := board.FEN(validatedFEN)
-	if err != nil {
-		return fmt.Errorf("engine returned invalid FEN: %v", err)
-	}
-	startingTurn := b.Turn()
-
-	// Setup players based on types
-	whitePlayer := &core.Player{
-		ID:   "white",
-		Type: whiteType,
-	}
-	if whiteType == core.PlayerComputer {
-		whitePlayer.ID = "stockfish-white"
-	}
-
-	blackPlayer := &core.Player{
-		ID:   "black",
-		Type: blackType,
-	}
-	if blackType == core.PlayerComputer {
-		blackPlayer.ID = "stockfish-black"
-	}
-
-	s.games[id] = game.New(validatedFEN, whitePlayer, blackPlayer, startingTurn)
+	// Create players with UUIDs and config
+	whitePlayer := core.NewPlayer(whiteConfig, core.ColorWhite)
+	blackPlayer := core.NewPlayer(blackConfig, core.ColorBlack)

+	s.games[id] = game.New(initialFEN, whitePlayer, blackPlayer, startingTurn)
 	return nil
 }

-func (s *Service) MakeHumanMove(gameID, uci string) error {
-	// Basic move format validation
-	uci = strings.ToLower(strings.TrimSpace(uci))
-	if len(uci) < 4 || len(uci) > 5 {
-		return fmt.Errorf("invalid move format: expected e2e4 or e7e8q")
-	}
+// UpdatePlayers replaces players in an existing game
+func (s *Service) UpdatePlayers(gameID string, whiteConfig, blackConfig core.PlayerConfig) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()

 	g, ok := s.games[gameID]
 	if !ok {
-		return fmt.Errorf("game not found")
+		return fmt.Errorf("game not found: %s", gameID)
 	}

-	// Check if it's human's turn
-	if g.NextPlayer().Type != core.PlayerHuman {
-		return fmt.Errorf("not a human player's turn")
-	}
+	// Create new player instances with new UUIDs
+	whitePlayer := core.NewPlayer(whiteConfig, core.ColorWhite)
+	blackPlayer := core.NewPlayer(blackConfig, core.ColorBlack)

-	currentFEN := g.CurrentFEN()
-	humanColor := g.NextTurn()
+	// Update the game's players
+	g.UpdatePlayers(whitePlayer, blackPlayer)

-	// Try to apply human move
-	s.engine.SetPosition(currentFEN, []string{uci})
-
-	// Get FEN after human move to check if move was legal
-	humanMoveFEN, err := s.engine.GetFEN()
-	if err != nil {
-		return fmt.Errorf("failed to get position: %v", err)
-	}
-
-	// If position didn't change, move was illegal
-	if humanMoveFEN == currentFEN {
-		return fmt.Errorf("illegal move")
-	}
-
-	// Record human move
-	g.AddSnapshot(humanMoveFEN, uci, core.OppositeColor(humanColor))
-
-	// Check if opponent has any legal moves
-	s.engine.SetPosition(humanMoveFEN, []string{})
-	search, _ := s.engine.Search(100) // Quick search to check for legal moves
-
-	result := &game.MoveResult{
-		Move:      uci,
-		Player:    humanColor,
-		GameState: core.StateOngoing,
-	}
-
-	if search.BestMove == "" || search.BestMove == "(none)" {
-		// Human checkmated the opponent
-		if humanColor == core.ColorWhite {
-			g.SetState(core.StateWhiteWins)
-		} else {
-			g.SetState(core.StateBlackWins)
-		}
-		result.GameState = g.State()
-	}
-
-	// Store result in game instead of service
-	g.SetLastResult(result)
 	return nil
 }

-func (s *Service) MakeComputerMove(gameID string) (*game.MoveResult, error) {
+// GetGame retrieves a game by ID
+func (s *Service) GetGame(gameID string) (*game.Game, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
 	g, ok := s.games[gameID]
 	if !ok {
 		return nil, fmt.Errorf("game not found: %s", gameID)
 	}
-
-	if g.NextPlayer().Type != core.PlayerComputer {
-		return nil, fmt.Errorf("not computer's turn")
-	}
-
-	currentColor := g.NextTurn()
-	s.engine.SetPosition(g.CurrentFEN(), []string{})
-	search, err := s.engine.Search(1000)
-	if err != nil {
-		return nil, fmt.Errorf("engine error: %v", err)
-	}
-
-	result := &game.MoveResult{
-		Player:    currentColor,
-		Score:     search.Score,
-		Depth:     search.Depth,
-		GameState: core.StateOngoing,
-	}
-
-	if search.BestMove == "" || search.BestMove == "(none)" {
-		// No legal moves - computer is checkmated
-		if currentColor == core.ColorWhite {
-			g.SetState(core.StateBlackWins)
-		} else {
-			g.SetState(core.StateWhiteWins)
-		}
-		result.GameState = g.State()
-		g.SetLastResult(result)
-		return result, nil
-	}
-
-	result.Move = search.BestMove
-
-	// Apply move and get resulting FEN
-	s.engine.SetPosition(g.CurrentFEN(), []string{search.BestMove})
-	newFEN, err := s.engine.GetFEN()
-	if err != nil {
-		return nil, fmt.Errorf("failed to get position: %v", err)
-	}
-
-	g.AddSnapshot(newFEN, search.BestMove, core.OppositeColor(currentColor))
-
-	// Check if opponent has any legal moves
-	s.engine.SetPosition(newFEN, []string{})
-	testSearch, _ := s.engine.Search(100)
-
-	if testSearch.BestMove == "" || testSearch.BestMove == "(none)" {
-		// Computer checkmated the opponent
-		if currentColor == core.ColorWhite {
-			g.SetState(core.StateWhiteWins)
-		} else {
-			g.SetState(core.StateBlackWins)
-		}
-		result.GameState = g.State()
-	}
-
-	// Store result in game
-	g.SetLastResult(result)
-	return result, nil
+	return g, nil
 }

-func (s *Service) Undo(gameID string, count int) error {
+// GenerateGameID creates a new unique game ID
+func (s *Service) GenerateGameID() string {
+	return uuid.New().String()
+}
+
+// ApplyMove adds a validated move to the game history
+// The processor has already validated this move and calculated the new FEN
+func (s *Service) ApplyMove(gameID, moveUCI, newFEN string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	g, ok := s.games[gameID]
+	if !ok {
+		return fmt.Errorf("game not found: %s", gameID)
+	}
+
+	// Determine whose turn it was before this move
+	currentTurn := g.NextTurnColor()
+	nextTurn := core.OppositeColor(currentTurn)
+
+	// Add the new position to game history
+	g.AddSnapshot(newFEN, moveUCI, nextTurn)
+
+	return nil
+}
+
+// UpdateGameState sets the game's end state (checkmate, stalemate, etc)
+func (s *Service) UpdateGameState(gameID string, state core.State) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	g, ok := s.games[gameID]
+	if !ok {
+		return fmt.Errorf("game not found: %s", gameID)
+	}
+
+	g.SetState(state)
+	return nil
+}
+
+// SetLastMoveResult stores metadata about the last move (score, depth, etc)
+// Used by processor to track computer move evaluations
+func (s *Service) SetLastMoveResult(gameID string, result *game.MoveResult) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	g, ok := s.games[gameID]
+	if !ok {
+		return fmt.Errorf("game not found: %s", gameID)
+	}
+
+	g.SetLastResult(result)
+	return nil
+}
+
+// UndoMoves removes the specified number of moves from game history
+func (s *Service) UndoMoves(gameID string, count int) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	g, ok := s.games[gameID]
 	if !ok {
 		return fmt.Errorf("game not found: %s", gameID)
@ -207,34 +142,25 @@ func (s *Service) Undo(gameID string, count int) error {
 	return g.UndoMoves(count)
 }

-func (s *Service) GetCurrentBoard(gameID string) (*board.Board, error) {
-	g, ok := s.games[gameID]
-	if !ok {
-		return nil, fmt.Errorf("game not found: %s", gameID)
-	}
-
-	return board.FEN(g.CurrentFEN())
-}
-
-func (s *Service) GetGame(gameID string) (*game.Game, error) {
-	g, ok := s.games[gameID]
-	if !ok {
-		return nil, fmt.Errorf("game not found: %s", gameID)
-	}
-	return g, nil
-}
-
+// DeleteGame removes a game from memory
 func (s *Service) DeleteGame(gameID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	if _, ok := s.games[gameID]; !ok {
 		return fmt.Errorf("game not found: %s", gameID)
 	}
+
 	delete(s.games, gameID)
 	return nil
 }

+// Close cleans up resources (currently a no-op as no engine to close)
 func (s *Service) Close() error {
-	if s.engine != nil {
-		return s.engine.Close()
-	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	// Clear all games
+	s.games = make(map[string]*game.Game)
 	return nil
 }
--- a/internal/transport/cli/handler.go
+++ b/internal/transport/cli/handler.go
@ -1,248 +0,0 @@
-// FILE: internal/transport/cli/handler.go
-package cli
-
-import (
-	"fmt"
-	"strconv"
-	"strings"
-
-	"chess/internal/cli"
-	"chess/internal/core"
-	"chess/internal/service"
-
-	"github.com/google/uuid"
-)
-
-type CLIHandler struct {
-	svc    *service.Service
-	view   *cli.CLI
-	gameID string
-}
-
-func New(svc *service.Service, view *cli.CLI) *CLIHandler {
-	return &CLIHandler{
-		svc:  svc,
-		view: view,
-	}
-}
-
-// Main game loop - simple command processing
-func (h *CLIHandler) Run() {
-	for {
-		// Generate prompt based on current game state
-		prompt := h.getPrompt()
-		h.view.ShowPrompt(prompt)
-
-		// Get command (blocking)
-		cmd, err := h.view.GetCommand()
-		if err != nil {
-			break
-		}
-
-		// Process command - returns false to exit
-		if !h.ProcessCommand(cmd) {
-			break
-		}
-	}
-}
-
-// Generates the appropriate command prompt
-func (h *CLIHandler) getPrompt() string {
-	prompt := "> "
-	if h.gameID != "" {
-		g, err := h.svc.GetGame(h.gameID)
-		if err == nil && g.State() == core.StateOngoing {
-			// Always show whose turn it is
-			prompt = fmt.Sprintf("[%c]> ", g.NextTurn())
-			if g.NextPlayer().Type == core.PlayerComputer {
-				prompt = "ENTER to execute computer move\n" + prompt
-			}
-		}
-	}
-	return prompt
-}
-
-// Handles user commands - returns false to exit
-func (h *CLIHandler) ProcessCommand(cmd *cli.Command) bool {
-	switch cmd.Type {
-	case cli.CmdQuit:
-		return false
-
-	case cli.CmdNone:
-		// Empty command triggers computer move if it's computer's turn
-		if h.gameID != "" {
-			g, err := h.svc.GetGame(h.gameID)
-			if err == nil && g.State() == core.StateOngoing &&
-				g.NextPlayer().Type == core.PlayerComputer {
-				h.executeComputerMove()
-			}
-		}
-		return true
-
-	case cli.CmdNew:
-		return h.handleNewGame("")
-
-	case cli.CmdResume:
-		if len(cmd.Args) < 1 {
-			h.view.ShowMessage("Usage: resume <FEN string>")
-			return true
-		}
-		fen := strings.Join(cmd.Args, " ")
-		return h.handleNewGame(fen)
-
-	case cli.CmdMove:
-		if h.gameID == "" {
-			h.view.ShowMessage("No active game. Use 'new' or 'resume <FEN>'.")
-			return true
-		}
-
-		g, _ := h.svc.GetGame(h.gameID)
-		if g.NextPlayer().Type != core.PlayerHuman {
-			h.view.ShowMessage("It's not a human player's turn. Press ENTER to execute computer move.")
-			return true
-		}
-
-		if err := h.svc.MakeHumanMove(h.gameID, cmd.Args[0]); err != nil {
-			h.view.ShowError(fmt.Errorf("invalid move: %v", err))
-			return true
-		}
-
-		// Get result and display human move
-		g, _ = h.svc.GetGame(h.gameID)
-		result := g.LastResult()
-		if result != nil {
-			h.view.ShowHumanMove(result.Move)
-		}
-
-		board, _ := h.svc.GetCurrentBoard(h.gameID)
-		h.view.DisplayBoard(board)
-
-		if result != nil && result.GameState != core.StateOngoing {
-			h.view.ShowGameOver(result.GameState)
-			h.gameID = ""
-		}
-
-	case cli.CmdUndo:
-		if h.gameID == "" {
-			h.view.ShowMessage("No active game.")
-			return true
-		}
-
-		// Parse undo count
-		count := 1
-		if len(cmd.Args) > 0 {
-			if n, err := strconv.Atoi(cmd.Args[0]); err == nil && n > 0 {
-				count = n
-			} else {
-				h.view.ShowMessage("Invalid undo count. Usage: undo [count]")
-				return true
-			}
-		}
-
-		if err := h.svc.Undo(h.gameID, count); err != nil {
-			h.view.ShowError(err)
-		} else {
-			if count == 1 {
-				h.view.ShowMessage("Move undone")
-			} else {
-				h.view.ShowMessage(fmt.Sprintf("%d moves undone", count))
-			}
-
-			board, _ := h.svc.GetCurrentBoard(h.gameID)
-			h.view.DisplayBoard(board)
-		}
-
-	case cli.CmdColor:
-		if len(cmd.Args) < 1 {
-			h.view.ShowMessage("Usage: color <off|brown|green|gray>")
-			return true
-		}
-
-		theme := cli.ColorTheme(cmd.Args[0])
-		if err := h.view.SetTheme(theme); err != nil {
-			h.view.ShowError(err)
-		} else {
-			h.view.ShowMessage(fmt.Sprintf("Color theme set to: %s", theme))
-			if h.gameID != "" {
-				board, _ := h.svc.GetCurrentBoard(h.gameID)
-				h.view.DisplayBoard(board)
-			}
-		}
-
-	case cli.CmdVerbose:
-		verbose := h.view.ToggleVerbose()
-		h.view.ShowMessage(fmt.Sprintf("Verbose mode: %t", verbose))
-
-	case cli.CmdHistory:
-		if h.gameID == "" {
-			h.view.ShowMessage("No active game.")
-			return true
-		}
-		g, _ := h.svc.GetGame(h.gameID)
-		h.view.ShowGameHistory(g)
-
-	case cli.CmdHelp:
-		h.view.ShowHelp()
-	}
-
-	return true
-}
-
-func (h *CLIHandler) executeComputerMove() {
-	result, err := h.svc.MakeComputerMove(h.gameID)
-	if err != nil {
-		h.view.ShowError(fmt.Errorf("engine error: %v", err))
-		h.gameID = ""
-		return
-	}
-
-	h.view.ShowComputerMove(result)
-	board, _ := h.svc.GetCurrentBoard(h.gameID)
-	h.view.DisplayBoard(board)
-
-	if result.GameState != core.StateOngoing {
-		h.view.ShowGameOver(result.GameState)
-		h.gameID = ""
-	}
-}
-
-// Starts a new game with player type selection
-func (h *CLIHandler) handleNewGame(fen string) bool {
-	// Get player types
-	h.view.ShowPrompt("Select White player (h/c): ")
-	whiteInput := h.view.ReadLine()
-	var whiteType core.PlayerType
-	if whiteInput == "c" || whiteInput == "computer" {
-		whiteType = core.PlayerComputer
-	} else {
-		whiteType = core.PlayerHuman
-	}
-
-	h.view.ShowPrompt("Select Black player (h/c): ")
-	blackInput := h.view.ReadLine()
-	var blackType core.PlayerType
-	if blackInput == "c" || blackInput == "computer" {
-		blackType = core.PlayerComputer
-	} else {
-		blackType = core.PlayerHuman
-	}
-
-	// Create new game
-	h.gameID = uuid.New().String()
-	var fenArray []string
-	if fen != "" {
-		fenArray = []string{fen}
-	}
-
-	if err := h.svc.NewGame(h.gameID, whiteType, blackType, fenArray...); err != nil {
-		h.view.ShowError(fmt.Errorf("could not start the game: %v", err))
-		h.gameID = ""
-		return true
-	}
-
-	h.view.ShowMessage("Game started.")
-	board, _ := h.svc.GetCurrentBoard(h.gameID)
-	h.view.DisplayBoard(board)
-
-	return true
-}
--- a/internal/transport/http/game_handler.go
+++ b/internal/transport/http/game_handler.go
@ -1,316 +0,0 @@
-// FILE: internal/transport/http/game_handler.go
-package http
-
-import (
-	"fmt"
-	"strings"
-
-	"chess/internal/board"
-	"chess/internal/core"
-	"chess/internal/game"
-
-	"github.com/gofiber/fiber/v2"
-	"github.com/google/uuid"
-)
-
-// CreateGame creates a new game with specified player types
-func (h *HTTPHandler) CreateGame(c *fiber.Ctx) error {
-	var req CreateGameRequest
-	if err := c.BodyParser(&req); err != nil {
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "invalid request body",
-			Code:    ErrInvalidRequest,
-			Details: err.Error(),
-		})
-	}
-
-	gameID := uuid.New().String()
-
-	// Create game with proper type conversion
-	var fenArray []string
-	if req.FEN != "" {
-		fenArray = []string{req.FEN}
-	}
-
-	err := h.svc.NewGame(
-		gameID,
-		core.PlayerType(req.White),
-		core.PlayerType(req.Black),
-		fenArray...,
-	)
-	if err != nil {
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "failed to create game",
-			Code:    ErrInvalidRequest,
-			Details: err.Error(),
-		})
-	}
-
-	// Build response - cache game instance
-	g, _ := h.svc.GetGame(gameID)
-	response := h.buildGameResponse(gameID, g)
-
-	// Execute computer move if computer starts
-	if g.NextPlayer().Type == core.PlayerComputer && g.State() == core.StateOngoing {
-		if err := h.executeComputerMove(gameID, g, &response); err != nil {
-			// Log error but return game created successfully
-			fmt.Printf("Warning: failed to execute initial computer move: %v\n", err)
-		}
-	}
-
-	return c.Status(fiber.StatusCreated).JSON(response)
-}
-
-// GetGame retrieves current game state, executing computer move if needed
-func (h *HTTPHandler) GetGame(c *fiber.Ctx) error {
-	gameID := c.Params("gameId")
-
-	g, err := h.svc.GetGame(gameID)
-	if err != nil {
-		return c.Status(fiber.StatusNotFound).JSON(ErrorResponse{
-			Error: "game not found",
-			Code:  ErrGameNotFound,
-		})
-	}
-
-	response := h.buildGameResponse(gameID, g)
-
-	// Auto-execute computer move if it's computer's turn
-	if g.NextPlayer().Type == core.PlayerComputer && g.State() == core.StateOngoing {
-		if err := h.executeComputerMove(gameID, g, &response); err != nil {
-			return c.Status(fiber.StatusInternalServerError).JSON(ErrorResponse{
-				Error:   "failed to execute computer move",
-				Code:    ErrInternalError,
-				Details: err.Error(),
-			})
-		}
-	}
-
-	return c.JSON(response)
-}
-
-// MakeMove submits a human player move
-func (h *HTTPHandler) MakeMove(c *fiber.Ctx) error {
-	gameID := c.Params("gameId")
-
-	var req MoveRequest
-	if err := c.BodyParser(&req); err != nil {
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "invalid request body",
-			Code:    ErrInvalidRequest,
-			Details: err.Error(),
-		})
-	}
-
-	g, err := h.svc.GetGame(gameID)
-	if err != nil {
-		return c.Status(fiber.StatusNotFound).JSON(ErrorResponse{
-			Error: "game not found",
-			Code:  ErrGameNotFound,
-		})
-	}
-
-	// Check game state BEFORE making move
-	if g.State() != core.StateOngoing {
-		fmt.Printf("DEBUG: Move rejected - game over (state: %s)\n", g.State())
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "game is over",
-			Code:    ErrGameOver,
-			Details: fmt.Sprintf("game state: %s", g.State()),
-		})
-	}
-
-	// Verify it's human's turn
-	currentPlayer := g.NextPlayer()
-	if currentPlayer.Type != core.PlayerHuman {
-		fmt.Printf("DEBUG: Move rejected - not human turn (current: %v, turn: %c)\n",
-			currentPlayer.Type, g.NextTurn())
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "not human player's turn",
-			Code:    ErrNotHumanTurn,
-			Details: fmt.Sprintf("current turn: %c", g.NextTurn()),
-		})
-	}
-
-	fmt.Printf("DEBUG: Attempting human move %s for game %s\n", req.Move, gameID)
-
-	// Make human move
-	if err := h.svc.MakeHumanMove(gameID, req.Move); err != nil {
-		fmt.Printf("DEBUG: Move failed: %v\n", err)
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "invalid move",
-			Code:    ErrInvalidMove,
-			Details: err.Error(),
-		})
-	}
-
-	// Get updated game state - refresh g
-	g, _ = h.svc.GetGame(gameID)
-	response := h.buildGameResponse(gameID, g)
-
-	// Include human move info from LastResult
-	if result := g.LastResult(); result != nil {
-		response.LastMove = &MoveInfo{
-			Move:   result.Move,
-			Player: colorToString(result.Player),
-		}
-	}
-
-	fmt.Printf("DEBUG: Human move successful, new state: %s, next turn: %c\n",
-		g.State(), g.NextTurn())
-
-	// Execute computer response if needed
-	if g.NextPlayer().Type == core.PlayerComputer && g.State() == core.StateOngoing {
-		fmt.Printf("DEBUG: Executing computer response\n")
-		if err := h.executeComputerMove(gameID, g, &response); err != nil {
-			// Computer move failed, but human move succeeded
-			fmt.Printf("Warning: computer move failed: %v\n", err)
-		}
-	}
-
-	return c.JSON(response)
-}
-
-// UndoMove undoes one or more moves
-func (h *HTTPHandler) UndoMove(c *fiber.Ctx) error {
-	gameID := c.Params("gameId")
-
-	var req UndoRequest
-	if err := c.BodyParser(&req); err != nil {
-		// Body parsing failed, use default
-		req.Count = 1
-	}
-
-	if req.Count < 1 {
-		req.Count = 1
-	}
-
-	if err := h.svc.Undo(gameID, req.Count); err != nil {
-		// Determine if game not found or invalid undo
-		if strings.Contains(err.Error(), "not found") {
-			return c.Status(fiber.StatusNotFound).JSON(ErrorResponse{
-				Error: "game not found",
-				Code:  ErrGameNotFound,
-			})
-		}
-		return c.Status(fiber.StatusBadRequest).JSON(ErrorResponse{
-			Error:   "cannot undo moves",
-			Code:    ErrInvalidRequest,
-			Details: err.Error(),
-		})
-	}
-
-	// Return updated game state
-	g, _ := h.svc.GetGame(gameID)
-	response := h.buildGameResponse(gameID, g)
-
-	return c.JSON(response)
-}
-
-// DeleteGame ends and cleans up a game
-func (h *HTTPHandler) DeleteGame(c *fiber.Ctx) error {
-	gameID := c.Params("gameId")
-
-	if err := h.svc.DeleteGame(gameID); err != nil {
-		return c.Status(fiber.StatusNotFound).JSON(ErrorResponse{
-			Error: "game not found",
-			Code:  ErrGameNotFound,
-		})
-	}
-
-	return c.SendStatus(fiber.StatusNoContent)
-}
-
-// GetBoard returns ASCII representation of the board
-func (h *HTTPHandler) GetBoard(c *fiber.Ctx) error {
-	gameID := c.Params("gameId")
-
-	g, err := h.svc.GetGame(gameID)
-	if err != nil {
-		return c.Status(fiber.StatusNotFound).JSON(ErrorResponse{
-			Error: "game not found",
-			Code:  ErrGameNotFound,
-		})
-	}
-
-	b, _ := h.svc.GetCurrentBoard(gameID)
-
-	// Generate ASCII board
-	ascii := h.generateASCIIBoard(b)
-
-	return c.JSON(BoardResponse{
-		FEN:   g.CurrentFEN(),
-		Board: ascii,
-	})
-}
-
-// Helper: Build standard game response - FIXED to use GetPlayer()
-func (h *HTTPHandler) buildGameResponse(gameID string, g *game.Game) GameResponse {
-	whitePlayer := g.GetPlayer(core.ColorWhite)
-	blackPlayer := g.GetPlayer(core.ColorBlack)
-
-	return GameResponse{
-		GameID: gameID,
-		FEN:    g.CurrentFEN(),
-		Turn:   colorToString(g.NextTurn()),
-		State:  stateToString(g.State()),
-		Moves:  g.Moves(),
-		Players: PlayersInfo{
-			White: PlayerType(whitePlayer.Type),
-			Black: PlayerType(blackPlayer.Type),
-		},
-	}
-}
-
-// Helper: Execute computer move and update response - FIXED to accept game instance
-func (h *HTTPHandler) executeComputerMove(gameID string, g *game.Game, response *GameResponse) error {
-	result, err := h.svc.MakeComputerMove(gameID)
-	if err != nil {
-		return err
-	}
-
-	// Refresh game state after computer move
-	g, _ = h.svc.GetGame(gameID)
-
-	// Update response fields
-	response.FEN = g.CurrentFEN()
-	response.Turn = colorToString(g.NextTurn())
-	response.State = stateToString(g.State())
-	response.Moves = g.Moves()
-
-	// Add computer move info
-	if result != nil {
-		response.LastMove = &MoveInfo{
-			Move:   result.Move,
-			Player: colorToString(result.Player),
-			Score:  result.Score,
-			Depth:  result.Depth,
-		}
-	}
-
-	return nil
-}
-
-// Helper: Generate ASCII board representation
-func (h *HTTPHandler) generateASCIIBoard(b *board.Board) string {
-	var sb strings.Builder
-	sb.WriteString("  a b c d e f g h\n")
-
-	for r := 0; r < 8; r++ {
-		sb.WriteString(fmt.Sprintf("%d ", 8-r))
-		for f := 0; f < 8; f++ {
-			square := fmt.Sprintf("%c%c", 'a'+f, '8'-r)
-			piece := b.GetPieceAt(square)
-
-			if piece == 0 {
-				sb.WriteString(". ")
-			} else {
-				sb.WriteString(fmt.Sprintf("%c ", piece))
-			}
-		}
-		sb.WriteString(fmt.Sprintf(" %d\n", 8-r))
-	}
-	sb.WriteString("  a b c d e f g h")
-
-	return sb.String()
-}
--- a/internal/transport/http/handler.go
+++ b/internal/transport/http/handler.go
@ -1,148 +0,0 @@
-// FILE: internal/transport/http/handler.go
-package http
-
-import (
-	"fmt"
-	"strings"
-	"time"
-
-	"chess/internal/service"
-
-	"github.com/gofiber/fiber/v2"
-	"github.com/gofiber/fiber/v2/middleware/cors"
-	"github.com/gofiber/fiber/v2/middleware/limiter"
-	"github.com/gofiber/fiber/v2/middleware/logger"
-	"github.com/gofiber/fiber/v2/middleware/recover"
-)
-
-type HTTPHandler struct {
-	svc *service.Service
-}
-
-func NewHTTPHandler(svc *service.Service) *HTTPHandler {
-	return &HTTPHandler{svc: svc}
-}
-
-func NewFiberApp(svc *service.Service, devMode bool) *fiber.App {
-	// Create handler
-	h := NewHTTPHandler(svc)
-
-	// Initialize Fiber app
-	app := fiber.New(fiber.Config{
-		ErrorHandler: customErrorHandler,
-		ReadTimeout:  10 * time.Second,
-		WriteTimeout: 10 * time.Second,
-		IdleTimeout:  30 * time.Second,
-	})
-
-	// Global middleware (order matters)
-	app.Use(recover.New())
-	app.Use(logger.New(logger.Config{
-		Format: "${time} ${status} ${method} ${path} ${latency}\n",
-	}))
-	app.Use(cors.New(cors.Config{
-		AllowOrigins: "*",
-		AllowMethods: "GET,POST,DELETE,OPTIONS",
-		AllowHeaders: "Origin,Content-Type,Accept",
-	}))
-
-	// Health check (no rate limit)
-	app.Get("/health", h.Health)
-
-	// API v1 routes with rate limiting
-	api := app.Group("/api/v1")
-
-	// Rate limiter: 1/10 req/sec per IP with expiry
-	maxReq := 1
-	if devMode {
-		maxReq = 10
-	}
-	api.Use(limiter.New(limiter.Config{
-		Max:        maxReq,          // Allow requests per second
-		Expiration: 1 * time.Second, // Per second
-		KeyGenerator: func(c *fiber.Ctx) string {
-			// Check X-Forwarded-For first, then X-Real-IP, then RemoteIP
-			if xff := c.Get("X-Forwarded-For"); xff != "" {
-				// Take the first IP from X-Forwarded-For chain
-				if idx := strings.Index(xff, ","); idx != -1 {
-					return strings.TrimSpace(xff[:idx])
-				}
-				return xff
-			}
-			return c.IP()
-		},
-		LimitReached: func(c *fiber.Ctx) error {
-			return c.Status(fiber.StatusTooManyRequests).JSON(ErrorResponse{
-				Error:   "rate limit exceeded",
-				Code:    ErrRateLimitExceeded,
-				Details: fmt.Sprintf("%d requests per second allowed", maxReq),
-			})
-		},
-		Storage:                nil, // Use in-memory storage (default)
-		SkipFailedRequests:     false,
-		SkipSuccessfulRequests: false,
-	}))
-
-	// Content-Type validation for POST requests
-	api.Use(contentTypeValidator)
-
-	// Register game routes
-	api.Post("/games", h.CreateGame)
-	api.Get("/games/:gameId", h.GetGame)
-	api.Delete("/games/:gameId", h.DeleteGame)
-	api.Post("/games/:gameId/moves", h.MakeMove)
-	api.Post("/games/:gameId/undo", h.UndoMove)
-	api.Get("/games/:gameId/board", h.GetBoard)
-
-	return app
-}
-
-// contentTypeValidator ensures POST requests have application/json
-func contentTypeValidator(c *fiber.Ctx) error {
-	if c.Method() == "POST" {
-		contentType := c.Get("Content-Type")
-		if contentType != "application/json" && contentType != "" {
-			return c.Status(fiber.StatusUnsupportedMediaType).JSON(ErrorResponse{
-				Error:   "unsupported media type",
-				Code:    ErrInvalidContent,
-				Details: "Content-Type must be application/json",
-			})
-		}
-	}
-	return c.Next()
-}
-
-// customErrorHandler provides consistent error responses
-func customErrorHandler(c *fiber.Ctx, err error) error {
-	code := fiber.StatusInternalServerError
-	response := ErrorResponse{
-		Error: "internal server error",
-		Code:  ErrInternalError,
-	}
-
-	// Check if it's a Fiber error
-	if e, ok := err.(*fiber.Error); ok {
-		code = e.Code
-		response.Error = e.Message
-
-		// Map HTTP status to error codes
-		switch code {
-		case fiber.StatusNotFound:
-			response.Code = ErrGameNotFound
-		case fiber.StatusBadRequest:
-			response.Code = ErrInvalidRequest
-		case fiber.StatusTooManyRequests:
-			response.Code = ErrRateLimitExceeded
-		}
-	}
-
-	return c.Status(code).JSON(response)
-}
-
-// Health check endpoint
-func (h *HTTPHandler) Health(c *fiber.Ctx) error {
-	return c.JSON(fiber.Map{
-		"status": "healthy",
-		"time":   time.Now().Unix(),
-	})
-}
--- a/internal/transport/http/types.go
+++ b/internal/transport/http/types.go
@ -1,119 +0,0 @@
-// FILE: internal/transport/http/types.go
-package http
-
-import (
-	"chess/internal/core"
-)
-
-// Request types
-
-type CreateGameRequest struct {
-	White PlayerType `json:"white"` // 0=human, 1=computer
-	Black PlayerType `json:"black"` // 0=human, 1=computer
-	FEN   string     `json:"fen,omitempty"`
-}
-
-type MoveRequest struct {
-	Move string `json:"move"` // UCI format: "e2e4"
-}
-
-type UndoRequest struct {
-	Count int `json:"count,omitempty"` // default: 1
-}
-
-// Response types
-
-type GameResponse struct {
-	GameID   string      `json:"gameId"`
-	FEN      string      `json:"fen"`
-	Turn     string      `json:"turn"`  // "w" or "b"
-	State    string      `json:"state"` // "ongoing", "white_wins", etc
-	Moves    []string    `json:"moves"`
-	Players  PlayersInfo `json:"players"`
-	LastMove *MoveInfo   `json:"lastMove,omitempty"`
-}
-
-type PlayersInfo struct {
-	White PlayerType `json:"white"`
-	Black PlayerType `json:"black"`
-}
-
-type MoveInfo struct {
-	Move   string `json:"move"`
-	Player string `json:"player"` // "w" or "b"
-	Score  int    `json:"score,omitempty"`
-	Depth  int    `json:"depth,omitempty"`
-}
-
-type BoardResponse struct {
-	FEN   string `json:"fen"`
-	Board string `json:"board"` // ASCII representation
-}
-
-type ErrorResponse struct {
-	Error   string `json:"error"`
-	Code    string `json:"code"`
-	Details string `json:"details,omitempty"`
-}
-
-// Custom type for JSON marshaling of PlayerType
-type PlayerType core.PlayerType
-
-func (p PlayerType) MarshalJSON() ([]byte, error) {
-	// Map to int for JSON: 0=human, 1=computer
-	return []byte(string('0' + p)), nil
-}
-
-func (p *PlayerType) UnmarshalJSON(data []byte) error {
-	if len(data) == 1 && data[0] >= '0' && data[0] <= '1' {
-		*p = PlayerType(data[0] - '0')
-		return nil
-	}
-	// Also accept string format for compatibility
-	str := string(data)
-	if str == `"human"` || str == "human" {
-		*p = PlayerType(core.PlayerHuman)
-	} else if str == `"computer"` || str == "computer" {
-		*p = PlayerType(core.PlayerComputer)
-	} else if str == "0" {
-		*p = PlayerType(core.PlayerHuman)
-	} else if str == "1" {
-		*p = PlayerType(core.PlayerComputer)
-	}
-	return nil
-}
-
-// Helper functions
-
-func colorToString(c core.Color) string {
-	return string(c)
-}
-
-func stateToString(s core.State) string {
-	switch s {
-	case core.StateOngoing:
-		return "ongoing"
-	case core.StateWhiteWins:
-		return "white_wins"
-	case core.StateBlackWins:
-		return "black_wins"
-	case core.StateDraw:
-		return "draw"
-	case core.StateStalemate:
-		return "stalemate"
-	default:
-		return "unknown"
-	}
-}
-
-// Error codes
-const (
-	ErrGameNotFound      = "GAME_NOT_FOUND"
-	ErrInvalidMove       = "INVALID_MOVE"
-	ErrNotHumanTurn      = "NOT_HUMAN_TURN"
-	ErrGameOver          = "GAME_OVER"
-	ErrRateLimitExceeded = "RATE_LIMIT_EXCEEDED"
-	ErrInvalidContent    = "INVALID_CONTENT_TYPE"
-	ErrInvalidRequest    = "INVALID_REQUEST"
-	ErrInternalError     = "INTERNAL_ERROR"
-)
--- a/internal/transport/transport.go
+++ b/internal/transport/transport.go
@ -1,29 +0,0 @@
-// FILE: internal/transport/transport.go
-package transport
-
-import (
-	"chess/internal/board"
-	"chess/internal/core"
-	"chess/internal/game"
-)
-
-// Handler processes user commands independent of transport medium
-type Handler interface {
-	HandleNewGame(id string, fen string, whiteType, blackType core.PlayerType) error
-	HandleMove(gameID, move string) error
-	HandleUndo(gameID string) error
-	HandleGetBoard(gameID string) (*board.Board, error)
-	HandleGetGame(gameID string) (*game.Game, error)
-}
-
-// View abstracts display/output operations
-type View interface {
-	DisplayBoard(b *board.Board)
-	ShowMessage(msg string)
-	ShowError(err error)
-	ShowGameHistory(g *game.Game)
-	ShowComputerMove(player core.Color, move string, depth, score int)
-	ShowHumanMove(move string)
-	ShowGameOver(state core.State)
-	ShowPrompt(prompt string)
-}
--- a/test/test-api.sh
+++ b/test/test-api.sh
--- a/test/test-player-config.sh
+++ b/test/test-player-config.sh
@ -0,0 +1,272 @@
+#!/usr/bin/env bash
+# FILE: test-player-config.sh
+
+# Player Configuration Deep Test Suite
+# Tests all aspects of player configuration changes mid-game
+# Debug-focused: prints full responses for analysis
+
+BASE_URL="http://localhost:8080"
+API_URL="${BASE_URL}/api/v1"
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+MAGENTA='\033[0;35m'
+CYAN='\033[0;36m'
+NC='\033[0m'
+
+# Helper to pretty-print JSON
+print_json() {
+    local label=$1
+    local json=$2
+    echo -e "${CYAN}>>> $label:${NC}"
+    echo "$json" | jq '.' 2>/dev/null || echo "$json"
+    echo ""
+}
+
+# Helper to extract and display specific fields
+show_players() {
+    local json=$1
+    local white_type=$(echo "$json" | jq -r '.players.white.type' 2>/dev/null)
+    local black_type=$(echo "$json" | jq -r '.players.black.type' 2>/dev/null)
+    local white_id=$(echo "$json" | jq -r '.players.white.id' 2>/dev/null)
+    local black_id=$(echo "$json" | jq -r '.players.black.id' 2>/dev/null)
+    
+    echo -e "${YELLOW}Players State:${NC}"
+    echo "  White: type=$white_type, id=$white_id"
+    echo "  Black: type=$black_type, id=$black_id"
+}
+
+# API request wrapper
+api_request() {
+    local method=$1
+    local url=$2
+    shift 2
+    curl -s "$@" -X "$method" "$url"
+}
+
+wait_for_pending() {
+    local game_id=$1
+    local max_wait=3
+    local waited=0
+    
+    while [ $waited -lt $max_wait ]; do
+        local response=$(api_request GET "$API_URL/games/$game_id")
+        local state=$(echo "$response" | jq -r '.state' 2>/dev/null)
+        if [ "$state" != "Pending" ]; then
+            return 0
+        fi
+        sleep 0.2
+        waited=$((waited + 1))
+    done
+    return 1
+}
+
+echo -e "${CYAN}═══════════════════════════════════════════════════════════${NC}"
+echo -e "${CYAN}Player Configuration Deep Test Suite${NC}"
+echo -e "${CYAN}═══════════════════════════════════════════════════════════${NC}"
+
+# Test 1: Basic player type changes
+echo -e "\n${GREEN}TEST 1: Create H-v-C, immediately change to C-v-H${NC}"
+echo "------------------------------------------------------"
+
+RESPONSE=$(api_request POST "$API_URL/games" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 2, "level": 5}}')
+GAME1_ID=$(echo "$RESPONSE" | jq -r '.gameId' 2>/dev/null)
+
+print_json "Initial H-v-C game created" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Change configuration
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME1_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 2, "level": 10}, "black": {"type": 1}}')
+
+print_json "After configuration change (should be C-v-H)" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Verify with GET
+RESPONSE=$(api_request GET "$API_URL/games/$GAME1_ID")
+print_json "GET verification" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Cleanup
+api_request DELETE "$API_URL/games/$GAME1_ID" > /dev/null
+
+# Test 2: Change during active game
+echo -e "\n${GREEN}TEST 2: H-v-H game with moves, then change to H-v-C${NC}"
+echo "------------------------------------------------------"
+
+RESPONSE=$(api_request POST "$API_URL/games" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 1}}')
+GAME2_ID=$(echo "$RESPONSE" | jq -r '.gameId' 2>/dev/null)
+
+print_json "Initial H-v-H game" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Make some moves
+echo -e "\n${BLUE}Making moves: e2e4, e7e5, g1f3${NC}"
+
+RESPONSE=$(api_request POST "$API_URL/games/$GAME2_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "e2e4"}')
+echo "Move 1 (e2e4): $(echo "$RESPONSE" | jq -r '.state' 2>/dev/null)"
+
+RESPONSE=$(api_request POST "$API_URL/games/$GAME2_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "e7e5"}')
+echo "Move 2 (e7e5): $(echo "$RESPONSE" | jq -r '.state' 2>/dev/null)"
+
+RESPONSE=$(api_request POST "$API_URL/games/$GAME2_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "g1f3"}')
+echo "Move 3 (g1f3): $(echo "$RESPONSE" | jq -r '.state' 2>/dev/null)"
+
+# Get current state
+RESPONSE=$(api_request GET "$API_URL/games/$GAME2_ID")
+print_json "Game state after 3 moves" "$RESPONSE"
+echo "Move history: $(echo "$RESPONSE" | jq -r '.moves' 2>/dev/null)"
+
+# Change to H-v-C
+echo -e "\n${BLUE}Changing configuration to H-v-C${NC}"
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME2_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 2, "level": 8, "searchTime": 200}}')
+
+print_json "After config change (should be H-v-C)" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Trigger computer move
+echo -e "\n${BLUE}Triggering computer move (black)${NC}"
+RESPONSE=$(api_request POST "$API_URL/games/$GAME2_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "cccc"}')
+
+if echo "$RESPONSE" | jq -r '.state' 2>/dev/null | grep -q "Pending"; then
+    echo "Computer move triggered, waiting..."
+    wait_for_pending "$GAME2_ID"
+fi
+
+# Get final state with history
+RESPONSE=$(api_request GET "$API_URL/games/$GAME2_ID")
+print_json "Final game state with computer move" "$RESPONSE"
+echo -e "${MAGENTA}Complete move history: $(echo "$RESPONSE" | jq -r '.moves' 2>/dev/null)${NC}"
+show_players "$RESPONSE"
+
+# Cleanup
+api_request DELETE "$API_URL/games/$GAME2_ID" > /dev/null
+
+# Test 3: Multiple configuration changes
+echo -e "\n${GREEN}TEST 3: Multiple configuration changes${NC}"
+echo "------------------------------------------------------"
+
+RESPONSE=$(api_request POST "$API_URL/games" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 2, "level": 15}, "black": {"type": 2, "level": 15}}')
+GAME3_ID=$(echo "$RESPONSE" | jq -r '.gameId' 2>/dev/null)
+
+print_json "Initial C-v-C game" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Change 1: C-v-C to H-v-H
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME3_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 1}}')
+print_json "Change 1: Now H-v-H" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Change 2: H-v-H to H-v-C
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME3_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 2, "level": 20}}')
+print_json "Change 2: Now H-v-C" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Change 3: H-v-C to C-v-H
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME3_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 2, "level": 1}, "black": {"type": 1}}')
+print_json "Change 3: Now C-v-H" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Final verification
+RESPONSE=$(api_request GET "$API_URL/games/$GAME3_ID")
+print_json "Final GET verification" "$RESPONSE"
+show_players "$RESPONSE"
+
+# Cleanup
+api_request DELETE "$API_URL/games/$GAME3_ID" > /dev/null
+
+# Test 4: Error cases
+echo -e "\n${GREEN}TEST 4: Error handling${NC}"
+echo "------------------------------------------------------"
+
+# Try to change during pending state
+RESPONSE=$(api_request POST "$API_URL/games" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 2, "searchTime": 500}}')
+GAME4_ID=$(echo "$RESPONSE" | jq -r '.gameId' 2>/dev/null)
+
+# Make human move
+api_request POST "$API_URL/games/$GAME4_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "e2e4"}' > /dev/null
+
+# Trigger computer move
+api_request POST "$API_URL/games/$GAME4_ID/moves" \
+    -H "Content-Type: application/json" \
+    -d '{"move": "cccc"}' > /dev/null
+
+# Immediately try to change config (should fail)
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME4_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 2}, "black": {"type": 1}}')
+
+print_json "Config change during Pending (should error)" "$RESPONSE"
+
+wait_for_pending "$GAME4_ID"
+api_request DELETE "$API_URL/games/$GAME4_ID" > /dev/null
+
+# Test 5: Verify player IDs change
+echo -e "\n${GREEN}TEST 5: Verify player IDs change on reconfiguration${NC}"
+echo "------------------------------------------------------"
+
+RESPONSE=$(api_request POST "$API_URL/games" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 1}}')
+GAME5_ID=$(echo "$RESPONSE" | jq -r '.gameId' 2>/dev/null)
+
+WHITE_ID_1=$(echo "$RESPONSE" | jq -r '.players.white.id' 2>/dev/null)
+BLACK_ID_1=$(echo "$RESPONSE" | jq -r '.players.black.id' 2>/dev/null)
+echo "Initial IDs: White=$WHITE_ID_1, Black=$BLACK_ID_1"
+
+# Change configuration (even to same types)
+RESPONSE=$(api_request PUT "$API_URL/games/$GAME5_ID/players" \
+    -H "Content-Type: application/json" \
+    -d '{"white": {"type": 1}, "black": {"type": 1}}')
+
+WHITE_ID_2=$(echo "$RESPONSE" | jq -r '.players.white.id' 2>/dev/null)
+BLACK_ID_2=$(echo "$RESPONSE" | jq -r '.players.black.id' 2>/dev/null)
+echo "After reconfig: White=$WHITE_ID_2, Black=$BLACK_ID_2"
+
+if [ "$WHITE_ID_1" != "$WHITE_ID_2" ]; then
+    echo -e "${GREEN}✓ White player ID changed (expected)${NC}"
+else
+    echo -e "${RED}✗ White player ID unchanged (unexpected)${NC}"
+fi
+
+if [ "$BLACK_ID_1" != "$BLACK_ID_2" ]; then
+    echo -e "${GREEN}✓ Black player ID changed (expected)${NC}"
+else
+    echo -e "${RED}✗ Black player ID unchanged (unexpected)${NC}"
+fi
+
+api_request DELETE "$API_URL/games/$GAME5_ID" > /dev/null
+
+echo -e "\n${CYAN}═══════════════════════════════════════════════════════════${NC}"
+echo -e "${CYAN}Test Complete${NC}"
+echo -e "${CYAN}═══════════════════════════════════════════════════════════${NC}"