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Leaf dev.5382 JA - new (old?) chess egnine

 


Leaf - new (old?) chess egnine
Leaf is an open-source chess engine written in C++ by Daniel C. Homan, an astrophysicist at Denison University in Granville, Ohio. Originally developed under the name EXchess, development began in the late 1990s and the engine was actively maintained and released through early 2017. After a long hiatus, the project was restarted in 2026 with significant new features developed in collaboration with Claude Code (Anthropic) and renamed to Leaf.

In early 2026 the project was restarted with a focus on two major new capabilities: a Stockfish-compatible NNUE evaluation and a TDLeaf(λ) online learning system that can train the NNUE weights from self-play.

This work was developed interactively with Claude Code, Anthropic's AI coding assistant. The collaboration covered design, implementation, debugging, and tuning — from the initial NNUE forward-pass implementation through to verifying the evaluation matched Stockfish 15.1 exactly and training the network from self-play games.

Author: Dan Homan


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