Confirm and close issue #5: CopperBot head-on collision avoidance

[Copilot]

Issue #5 requested difficulty-scaled head-on collision behavior for CopperBot. The feature was already fully implemented in v3.6.0 — this PR confirms it's working as specified.

Verified behavior

Collision tile scoring in calculate_move() across all difficulty levels:

Level	Behavior
1	Always avoid predicted opponent head tile
2–5	Avoid with probability 90%→10% (interpolated); otherwise seek
6–9	Seek if my_length > opp_length, probability 10%→90%; otherwise avoid
10	Always seek if longer; always avoid if not

# Level 6–9 core logic
prioritize_prob = 0.1 + (self.difficulty - 6) * 0.8 / 3
if my_length > opp_length and random.random() < prioritize_prob:
    score += collision_bonus   # 2000
else:
    score += collision_penalty # -5000

Simulation over 200 trials per level confirmed empirical rates match the specified probabilities. Already documented in CHANGELOG under v3.6.0.

Warning

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Original prompt

confirm server issue #5 is fixed, updated and close if so

[Chronological Review] 1. User requested "launch-game" → skill loaded, server and client launched on ports 8765 and 3000 2. User requested 2 instances of sleepy-snake → found bot at copperhead-server/bot-library/sleepy_snake.py, launched both, they played and finished 3. User requested 2 instances of sleepy-snake level 1 → launched with --difficulty 1, observed stalemate trigger 4. User asked why stalemate took ~90s instead of 30s → investigated code, explained that accidental food collection resets the timer (ticks_since_last_collection * tick_rate >= game_timeout) 5. User requested changelog update and push to v401 → fixed dates from 2026-06-26 to 2026-03-10, added missing entries (Sleepy Snake bot, competition status messaging), pushed both repos 6. User requested UX fix for disqualification message → traced server->client flow, found server sends close code 4008, client showed "Disconnected" instead of descriptive message 7. First fix attempt: added 4008 handler in connectWebSocket's onclose → tested but still showed "Disconnected from lobby" because players join via joinLobby() which has its own onclose handler 8. Second fix: added 4008 handler to lobby's onclose handler → tested, user confirmed it works, pushed to v401 9. User requested fix for server issue #10 (stale playfield) → investigated, found root cause: client doesn't clear gameState on match_assigned, server doesn't send initial game state 10. Fixed both server (include game state in match_assigned) and client (clear/render fresh state on match_assigned) 11. Relaunched to test → both services running, awaiting user testing

[Intent Mapping]

• "launch-game" → launch CopperHead server and client locally
• "launch 2 instances of sleepy-snake" → run bot instances
• "launch 2 instances of sleepy-snake level 1" → run L1 difficulty bots (food-avoiding)
• "why did it take so long?" → explain stalemate timing
• "update the changelog and push to v401 branch" → update both changelogs, commit and push
• "when a human is disqualified..." → fix disqualification UX (status message + button text)
• "relaunch locally to test" → restart server/client to test changes
• "Fix server issue Playfield in stale state before round start #10" → fix stale playfield before round start
• "relaunch to test" → restart server/client to test issue Playfield in stale state before round start #10 fix

[Technical Inventory]

• CopperHead: multiplayer snake game with server (Python/FastAPI/WebSocket) and client (JavaScript)
• Repos: copperhead-server (revodavid/copperhead-server) and copperhead-client (revodavid/copperhead-client)
• Branch: v401 for both repos
• Server: Python, FastAPI, Uvicorn, WebSocket on port 8765
• Client: Static JS served via python -m http.server on port 3000
• Local settings: server-settings.local.json (20x16 grid, 0.04s tick, 2 points to win, 0 bots, auto-start: always)
• Bots: sleepy_snake.py in bot-library/, copperbot.py, murderbot.py
• Close code 4008: custom WebSocket code for ready timeout
• Game stalemate: ticks_since_last_collection * config.tick_rate >= config.game_timeout

[Code Archaeology]

• copperhead-server/main.py: Game class (line 962), GameRoom class (line 1205), _handle_ready_timeout (line 1278), connect_competition_player (line 1329), broadcast_state (line 1696), game_loop (line 1543), start_game (line 1507), _start_next_game (line 1670)
• copperhead-client/game.js: connectWebSocket onclose (line 737), joinLobby onclose (line 1729), match_assigned handler (line 1039), sendReady (line 1187), updateCanvas (line 1325), "Return to Lobby" pattern (line 1189)
• copperhead-server/bot-library/sleepy_snake.py: wandering bot with difficulty 1-10
• copperhead-server/CHANGELOG.md: updated v4.0.1 date and entries
• copperhead-client/CHANGELOG.md: updated v4.0.1 date and entries

[Progress Assessment]

• DONE: Game launching, bot launching, stalemate investigation, changelog updates, disqualification UX fix (both handlers), issue Playfield in stale state before round start #10 fix (both server and client)
• PENDING: Testing issue Playfield in stale state before round start #10 fix (server and client relaunched, awaiting user verification), pushing issue Playfield in stale state before round start #10 commits to v401

[Context Validation]

• All commits made but issue Playfield in stale state before round start #10 changes not yet pushed to remote
• Server and client are currently running with latest code
• Admin token for current session: 5e344adf250f9e5b

[Recent Commands Analysis]

• Last commands: Relaunched server and client for issue Playfield in stale state before round start #10 testing
• Server started (PID 31484 on port 8765), client started (PID 51156 on port 3000)
• Admin token: 5e344adf250f9e5b
• User needs to test that playfield shows correct dimensions and starting snake heads before clicking "Start Round"

1. Conversation Overview: - Primary Objectives: Launch and test CopperHead snake game locally; fix UX issues including disqualification messaging and stale playfield rendering (GitHub issue #10); update changelogs and push to v401 branch - Session Context: The session involved iterative development on the CopperHead multiplayer snake gam...

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