Mephisto 3.1.207 — chess.com puzzle import
Chess.com puzzles import through the same button. The reader is in; the database itself follows the upstream merge.
Which download?
| Archive | Size | Use it when |
|---|---|---|
mephisto-3.1.207.zip |
585 MB | First install — everything, engines included |
mephisto-3.1.207-update.zip |
5.9 MB | You already have Mephisto — extract over your existing folder |
⚠️ Extract the update over your existing install, never into an empty folder — without the engines it cannot run. Extract in place: Chrome derives an unpacked extension's id from its folder path, so a new folder means a new id and re-running the native-host installer.
What's new
Settings → Load Puzzle Database now takes either file. The format is detected from the header, so there is nothing extra to pick, and importing both simply gives you both — they key on the position, so neither overwrites the other.
The two files cannot share a parser. Lichess rows are split on newlines, which is right for six million rows with nothing quoted in the columns that matter. Chess.com's pgn column holds a full PGN with literal newlines inside its quotes, so those rows go through a real streaming CSV reader; Lichess keeps its fast path.
Moves arrive as chess.com TCN — two characters per move, promotions encoded past the 64th square. The decoder is verified by replaying published rows through chess.js: all 12 moves of a 3554-rated tactic and all 4 of a 590 are legal from the position each row states, promotion included.
Daily archive rows are the exception twice over: they carry SAN rather than TCN, and they have no setup move, so the side to move is the solver. SAN needs a rules engine, which puzzle-db.js deliberately does not carry (it also runs in the service worker) — the settings page injects one.
Still to come
The 620,000+ puzzle database itself will be published once the upstream pull request is merged. This release is the reader, so it is ready the day the file lands.