Zen by reinit

AI chess analysis

The reason behind the verdict.

Stockfish finds the evidence. Cassia connects it to the threat, tactic, structure, or plan behind the move.

Analyze a gameSee the example
Zen by reinit showing a chess position beside Cassia's explanation of why the move g3 was a blunder
A real Zen analysis: the board, engine context, and Cassia explanation stay visible together.

AI should explain the analysis, not invent it.

General language models are not reliable chess engines. Zen gives calculation and explanation different jobs: Stockfish establishes what happened on the board, then Cassia helps translate those facts into chess reasoning.

Read how Cassia is grounded

A grounded explanation

From “blunder” to a line you can understand

This recording comes from the working product. It shows the concrete reason behind the classification and the defensive idea in the stronger move.

Cassia follows the forcing sequence on the same board the player is reviewing.

The verdict

8. g3? is classified as a blunder.

The reason

The move allows ...Qxe4+. The check gains time and creates a fork against the king and the rook on h1.

The defensive idea

Kd2 answers the check while the pawn on g2 still blocks the queen's path to h1 and remains defended.

The next question

Play the suggested defence in Explore, then use Simulation to see whether the idea survives a realistic continuation.

Calculation, explanation, and practice stay connected

Stockfish calculates

The engine evaluates the position, compares candidate moves, and supplies the concrete lines behind the verdict.

Cassia explains

Cassia turns the engine evidence into a reason you can follow on the board, without pretending language is calculation.

You verify

Explore lets you play the alternative. Simulation adds resistance so the explanation becomes something you can test.

The explanation remains part of your game

Zen is a personal chess review workspace, not a disposable report. Import Chess.com, Lichess, or PGN games, return to their turning points, and keep the analysis available in your library.

Exporting a .zen file can preserve classifications and Cassia conversations alongside the game, so a useful review does not have to begin again from raw PGN.

See the complete feature reference

Questions about AI chess analysis

What is AI chess analysis in Zen?

Zen separates chess calculation from language. Stockfish analyzes the position and candidate lines. Cassia uses that engine-grounded evidence to explain the threat, tactic, structure, or plan behind the result in plain language.

Is Cassia a chess engine?

No. Stockfish is the chess engine. Cassia is the explanatory assistant inside Zen. It does not replace engine analysis or independently invent the evaluation.

Can Cassia explain why my move was a blunder?

Yes. After Zen analyzes a game, select a move and ask Cassia to explain it. Cassia can connect the evaluation change to concrete details such as a missed check, hanging piece, tactical sequence, weakened square, or plan.

Which chess games can I analyze?

Zen can import games from Chess.com and Lichess by username, or accept a pasted or uploaded PGN. The games can remain in a personal local library for later review.

Do I need an account?

No account is required for the local game library, browser-based Stockfish analysis, Explore, or Simulation. Cassia requires an account because it uses an optional AI-assisted service.

Can Cassia make mistakes?

Yes. Cassia is in active development and can still produce an incomplete or incorrect explanation. Zen shows the board, engine lines, and analysis context so players can verify the explanation rather than treating it as an unquestionable verdict.

Bring one game. Leave with a reason you can test.

No account is required to start with the local library and Stockfish analysis.

Analyze a game