g6: Free Chess Analysis

demo.mp4

Public frontend for g6, an evidence-grounded chess analysis product.

The app lets someone paste a Chess.com or Lichess game link, open a g6chess.com/game/live/... or g6chess.com/lichess/... route, or paste PGN. It imports the game through the analysis API, polls for completed move analysis, and renders a board-first review with move labels, engine/book continuations, and coach-style explanations

Product Direction

g6 is not an LLM chess calculator, the product boundary is:

Stockfish + human-likelihood evidence + rules + verifiers = chess truth
LLM or deterministic renderer = wording for verified explanations

The user question we are trying to answer is:

At this move in my game, what happened, how good was my move, and what should I understand?

The frontend turns that into a usable review surface: import a real game, navigate the move list, inspect critical moments, preview verified lines on the board, and explore alternatives without losing the main game.

What Is In This Repo

• Vite + React + TypeScript frontend.
• Chess.com URL, Lichess URL, and PGN import UI.
• Route parsing for shareable game links and selected ply state.
• Polling client for the game-analysis API.
• Board-first analysis workspace with move list, eval bar, player bars, explanation panel, opening-book lines, and engine-line previews.
• UltraChess React board integration.
• Browser Stockfish as an exploration fallback for positions not covered by the server snapshot.

The repository is useful for working on the public UI and API contract. It is not enough to run the full g6 analysis product without the private backend.

Related Work

• ultrachess: Rust/WASM chess library with TypeScript bindings for legal move generation, FEN/SAN/PGN, perft, and hashing.
• ultrachess-react: React chessboard subsystem used by this app, with external board state, byte-scoped square subscriptions, WAAPI piece animation, and canvas arrows.
• Private g6 explanation engine: evidence packets, move labels, verified explanation generation, source-rights policy, and eval infrastructure.
• Older g6chess-* repos: product lineage around imports, live-game sync, narratives, puzzles, and the broader g6 application.

Local Development

If you're interested in the collaboration and contribution, please contact me for private backend repository access. I'm planning to opensource it anyway eventually, but the current state is not ready for public review.

Install dependencies:

bun install

Start the dev server:

bun run dev

The app runs at:

http://127.0.0.1:5173/

Point it at an analysis API with [If you're interested in the collaboration and contribution, please contact me for private repository access]:

VITE_G6_API_BASE_URL=http://127.0.0.1:8001

Enable Cloudflare Turnstile for anonymous import starts with:

VITE_G6_TURNSTILE_SITE_KEY=...

Expected API shape today:

• POST /api/game-analysis/import
• GET /api/game-analysis/import/chess-com/live/{externalGameId}
• GET /api/game-analysis/import/lichess/{externalGameId}
• polling through the returned status_url
• Import responses and game-analysis snapshots include a game skeleton with PGN-derived SAN/UCI/FEN move data. The client can render the board from that skeleton while deeper context and explanations are still pending.
• Normal import requests use include_context=false. Completed move snapshots include compact board, engine-line, label, and explanation fields for the UI; full context packets are reserved for internal/debug tooling.
• Engine top_lines describe pre-move alternatives from fen_before. When the played move matches the best line, the UI pairs that with the next ply's best line as a Best continuation row and shows the remaining current-position alternatives below. The visible row count defaults to two and can be changed in board settings. Engine WDL and Maia move-choice probabilities are kept for analysis data but are not shown as human win-probability percentages in the engine-line list.

Checks

bun run typecheck
bun run lint
bun run test
bun run build

bun install copies the browser Stockfish worker assets into public/stockfish/.