duplicate_chess/.claude/handoffs/2026-05-19-060141-duplicate-chess-v1-built.md

Handoff: Duplicate Chess v1 — built, tested, merged to main

Session Metadata

• Created: 2026-05-19 06:01:41
• Project: /home/claude/bin/duplicate_chess
• Branch: main (all work merged and pushed to git.sethpc.xyz/Seth/duplicate_chess)
• Session duration: one long session — brainstorm → spec → plan → full 14-task implementation → merge.

Recent Commits (for context)

• 5047ad7 docs: update CLAUDE.md — v1 implemented and merged
• fae9f8d docs: correct Task 4 test move data in the plan
• 5db0410 fix: real project README and save-file version validation
• ead4839 feat(ui): assemble the duplicate chess sandbox app
• bedb5a0 feat(ui): promotion dialog
• Full implementation range: 9611c0a (scaffold + spec) → 5047ad7. 18 commits.

Handoff Chain

• Continues from: None (first handoff — this is a brand-new project).
• Supersedes: None.

Current State Summary

duplicate_chess is a brand-new project created this session — a local browser sandbox for "duplicate chess", a four-player chess variant invented by Andrew Freiberg (Seth's father; also the inventor behind the sibling blind_chess project). The session ran the full superpowers pipeline: brainstorming → design spec → implementation plan → subagent-driven execution of all 14 plan tasks → final review → merge. v1 is code-complete, all 27 engine tests pass, the build and typecheck are clean, and it is merged to main and pushed. The one thing not done: a human interactive browser test (clicking through a real game). The app mounts and renders correctly (verified via a headless smoke render).

Codebase Understanding

Architecture Overview

Single Vite + Svelte 5 + TypeScript app, no server (duplicate chess is perfect-information, so everything runs client-side — this is the key difference from blind_chess, which needs a server as its trusted view boundary).

• Engine (src/engine/, pure TypeScript, DOM-free, vitest-tested): four chess.js games (NW/NE/SW/SE). A player's legal moves = the intersection of the moves legal on their two boards, keyed by (from,to,promotion). Ghost immobility, the synchronized-checkmate definition, and en-passant/castling divergence all fall out of the intersection — no special-case code.
• UI (src/lib/): a reactive store wraps the engine; the compass renders the four boards as a 45°-rotated pinwheel; the triple-highlight (green = playable on both boards, grey = legal on one only) is the teaching feature.

Critical Files

File	Purpose	Relevance
docs/superpowers/specs/2026-05-19-duplicate-chess-design.md	The full design spec	Read first — variant rules, engine model, provisional rules
docs/superpowers/plans/2026-05-19-duplicate-chess-sandbox.md	The 14-task implementation plan	What was built, task by task
src/engine/legality.ts	legalSyncedMoves + selectionHighlight	The intersection — the heart of the variant
src/engine/game.ts	DuplicateGame — 4 chess.js, history, undo, draw clocks	The single source of truth for game state
src/engine/ghosts.ts	Ghost derivation by cross-board comparison
src/engine/endgame.ts	checkmate/stalemate/threefold/fifty-move; PROVISIONAL rules	Andrew can revise the provisional rulings — grep PROVISIONAL
src/lib/stores/game.svelte.ts	Reactive store wrapping the engine	#game is plain (non-reactive); view is the $state snapshot
src/lib/Compass.svelte	The four-board pinwheel + click-to-move wiring

Key Patterns Discovered

• The engine is DOM-free and the single source of truth. The UI never computes legality; it calls the engine and renders the result.
• Store reactivity: chess.js objects must NOT be wrapped in a Svelte $state proxy. The store keeps DuplicateGame in a plain private #game field and exposes a plain-data view snapshot in $state, rebuilt after every change.
• The pinwheel rotations (NW 225°, NE 135°, SW 315°, SE 45°) put each player's army on the board edge facing their seat. Confirmed against Andrew's sketch.
• Tests reach real positions via playSymmetric (test-helpers.ts): when all four players move symmetrically the four boards stay identical, so each board is an ordinary chess game — that is how the checkmate/stalemate/threefold tests reach real terminal positions.

Work Completed

Tasks Finished

• All 14 tasks of the implementation plan, executed via subagent-driven development (fresh implementer subagent per task + a combined spec/quality review per task + a final whole-implementation review by an opus reviewer).
• Engine: types, boards, game, legality, ghosts, endgame, notation + an integration test. 27 vitest tests, all passing.
• UI: the reactive store + Board, Compass, Panel, PromotionDialog, App components.
• Two post-review fixes: a real project README, and save-file version validation in deserialize.
• Merged build-sandbox → main, pushed, feature branch deleted.

Files Modified

The whole project was created this session. See git log on main. New trees: src/engine/ (7 modules + 6 test files), src/lib/ (store + 4 components), src/App.svelte, src/app.css, plus the Vite scaffold and project docs.

Decisions Made

All recorded in DECISIONS.md. Key ones: local sandbox first (not networked); single Vite app, no server; engine = 4× chess.js + intersection; compass UI as a pinwheel of diamonds; coordinate notation; provisional endgame rules picked by Claude and marked PROVISIONAL. One decision surfaced during the build and is NOT yet in DECISIONS.md — see "Blockers/Open Questions".

Pending Work

Immediate Next Steps

1. Manual interactive browser test. Run pnpm install && pnpm dev, open the URL, and play a real game: click a piece on a glowing board → confirm the green/grey triple-highlight → click a green square → move applies to both that player's boards → turn advances. Verify ghosts appear after a one-sided capture, promotion dialog fires, undo / Prev / Next / Live work, Save downloads JSON and Load restores it. The engine is well-tested; the UI interaction is verified only by svelte-check + a headless smoke render so far.
2. Decide the scrubbing semantics (see Open Questions) and reconcile spec §4.3.
3. (Optional) The remaining minor follow-ups below, if they matter.

Blockers/Open Questions

• Scrub semantics — spec vs shipped code disagree. Spec §4.3 says "making a new move while scrubbed truncates history." The shipped code instead makes scrubbing view-only (you must click "● Live" before moving). The final review flagged this; the view-only behaviour is arguably cleaner. Seth to confirm which to keep; then update spec §4.3 (or the code) to match.
• The provisional endgame rules (spec §6) are Claude's defaults, not Andrew's rulings — double-board-mate = two winners, any stalemate ends the game all-draw, threefold/50-move tracked on the whole system. Andrew should confirm.

Deferred Items

• deserialize trusts the player field in a save file rather than recomputing it from turn order — a corrupt/hand-edited save could desync. App-written saves are always consistent, so this is robustness-only. Fix: have DuplicateGame's constructor ignore entry.player and use the turn-order default.
• Move log has no round-number column (within spec, but a nicety).
• Spec §4.3 names a replayTo(n) primitive; the code uses new DuplicateGame(history.slice(0,n)) instead — functionally equivalent, cosmetic naming mismatch only.
• Networking / AI / position editor — explicitly out of v1 scope (spec §7).

Context for Resuming Agent

Important Context

• The project is DONE for v1 and merged to main. There is nothing half-built. A resuming agent's job is the manual browser test (#1 above) and then deciding whether to ship/deploy or extend.
• blind_chess is the sibling project (~/bin/blind_chess) — same inventor, same homelab conventions, similar shared-engine + view-filter shape. The original inventor conversation that defines duplicate chess is ~/bin/blind_chess/USERFILES/4-person-chess.txt, and Andrew's compass sketch is ~/bin/blind_chess/USERFILES/4personchess.png.
• Provisional rules are isolated in src/engine/endgame.ts and commented PROVISIONAL (spec §6) — grep for it to find every spot a future ruling lands.
• v1 is local only — no deploy. Hosting the static pnpm build output behind Caddy is a trivial later option (it is just static files), not done.

Assumptions Made

• The interactive browser test passing is assumed but unverified — the headless smoke render confirmed the app mounts and renders all four boards with no console errors, but no clicks were exercised.
• 27 is the expected test count (all in src/engine/; the UI has no test harness by design — svelte-check + manual, same as blind_chess).

Potential Gotchas

• pnpm test uses --passWithNoTests (vitest 4.x exits 1 on no test files) — a deliberate scaffold choice; harmless now that tests exist.
• A .secrets.baseline file exists for the global detect-secrets pre-commit hook (it flags pnpm-lock.yaml SHA-512 integrity hashes as false positives).
• svelte-check reports 5 warnings — all pre-existing Vite-template tsconfig warnings (deprecated moduleResolution, missing composite). 0 errors. The warnings are not defects; ignore them or fix the template tsconfig if desired.
• The brainstorming visual-companion mockups for the compass live under ~/bin/blind_chess/.superpowers/brainstorm/.../content/ (layout-v6.html is the approved layout) — they are in the blind_chess repo, not this one.

Environment State

Tools/Services Used

• pnpm workspace tooling (Node 22, pnpm 10). gitea CLI for push.
• Subagent-driven development for the build (sonnet implementers/reviewers, an opus final reviewer).

Active Processes

• None. No dev server left running.

Environment Variables

• None added or required.

Related Resources

• Spec: docs/superpowers/specs/2026-05-19-duplicate-chess-design.md
• Plan: docs/superpowers/plans/2026-05-19-duplicate-chess-sandbox.md
• DECISIONS.md, IDEA.md
• Repo: https://git.sethpc.xyz/Seth/duplicate_chess (main at 5047ad7)
• Inventor conversation + sketch: ~/bin/blind_chess/USERFILES/4-person-chess.txt, ~/bin/blind_chess/USERFILES/4personchess.png

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Security Reminder: No credentials or secrets are included in this handoff.