Playground
CommunityJev Demos & Experiments
Chess — Chris Wijnia
An interactive chess experiment on chriswijnia.com: play Jev, TypeSafe's System One model, a simple engine or a friend, or watch Jev play itself. Each turn Jev weighs every legal move at once as one typed Choice and shows how sure it is.
- Format
- Playground
- Reading time
- 3 min
- Published by
- Community
- Author
- Chris Wijnia
- Last verified
- Oct 2026
Works forJev for Scoring
Used inJev for Gaming
- Platforms
- BrowserVercel AI Gateway
Highlights
- Each turn Jev weighs every legal move at once as one typed Choice, and its reading shows the pick, how sure it was, and its plan.
- Watch Jev vs Jev, watch Jev vs engine with sides swapping each game, play Jev, play the engine, or two players on one board.
- Three Jev levels and three speeds; Standard or Chess960, which shuffles the back rank into one of 960 starting positions.
- Rules come from chessops, the GPL-3.0 library behind Lichess, and the experiment's source is GPL-3.0 too.
- The coach is Stockfish as stockfish.js (GPL-3.0), loaded only when the coach is on; Jev runs through Vercel's AI Gateway.
Watch out
Grounded on the page text captured on 2026-10-15; the digest includes the page's controls and credits but no benchmarks, pricing or latency figures. Use of the live board was not exercised for this entry, and no playing-strength claim is made for Jev beyond what the page states.
Questions about this entry
Short answers drawn from the linked project or page.
A playable board on chriswijnia.com where you can play Jev, TypeSafe AI's System One model, or a simple engine or a friend, or watch Jev play itself with its thinking on show. Each turn Jev weighs every legal move at once as one typed Choice and shows how sure it is.
Watch Jev vs Jev, the model against itself; watch Jev vs engine, with sides swapping each game; play Jev yourself; play the engine, described as quick and grabbing material; or play a friend on one board.
Jev's level can be Easy, Normal or Hard, and the speed Slow, Normal or Fast. The board can be Standard or Chess960, which shuffles the back rank into one of 960 starting positions, and there is a coach toggle.
Every legal move is weighed at once as one typed Choice, and after each move the reading panel shows the pick, how sure it was, and its plan. Moves can be entered by click or drag, with arrow keys and Enter also supported.
Rules come from chessops by Niklas Fiekas, the library behind Lichess, under the GPL-3.0, and the experiment's source is GPL-3.0 too. The coach is Stockfish as stockfish.js (GPL-3.0), loaded only when the coach is on; Arcade and Console piece sets are by SpicyGame under CC0.
The page does not mention accounts, pricing or limits. Jev is called through Vercel's AI Gateway, but no cost figure appears in the captured text, so treat it as a free experiment unless the site says otherwise.
Chris Wijnia, whose site hosts it under the CW/CHESS interface. The page also credits piece sets to Armando H. Marroquin and Hans L. Bodlaender from Eric Bentzen's En Passant collection, alongside the chessops and stockfish.js work.
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