Caissa

A modern macOS chess GUI, forked from Lucas Chess R6

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Requirements

Apple Silicon (M1 or later) · macOS 14 Sonoma or later · git-lfs

Intel Macs are not supported — the vendored native engines are built arm64 only. Windows and Linux users should use upstream Lucas Chess R6.

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Install

# 1. Install Git LFS (once per machine)
brew install git-lfs
git lfs install

# 2. Clone — do NOT use the GitHub "Download ZIP" button
#    (ZIP archives carry no LFS objects and macOS quarantines the result)
git clone https://github.com/JohnnyFoulds/caissa
cd caissa

# 3. Create the Python virtual environment
python3.13 -m venv .venv
.venv/bin/pip install -r requirements.txt

# 4. Launch
./Caissa.command

That is all. No Homebrew chess engines, no build tools, no Docker — the native engines are committed in LFS and are ready the moment the clone finishes.

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What you get out of the box

Fourteen native arm64 engines, playable immediately with no extra setup:

Engine	Version	Notes
Stockfish	18	NNUE nets included beside the binary
Lc0	0.32.1	Metal backend; 791556.pb.gz net included
Maia	1100 – 2200 (10 nets)	Human-like play at your Elo; shares the Lc0 binary
irina	current	Fast, lightweight
Drawfish	74d10eb	Stockfish derivative: stalemate = win

See bin/OS/darwin/Engines/SOURCES.md for exact versions, build flags, and sha256 checksums.

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Optional: the Docker engine bridge

Docker unlocks ~91 additional Linux/Windows engines (the full upstream roster of 105 total):

# Install Docker Desktop, then:
tools/setup_darwin_engines.py   # generates the wrapper scripts once
./Caissa.command                # Docker container is pre-warmed automatically

Docker is genuinely optional — the app starts and plays normally without it.

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How Caissa differs from upstream Lucas Chess R6

• Native Apple Silicon engines — Stockfish, Lc0, Maia, irina and Drawfish committed in Git LFS; no Homebrew symlinks, no build tools required after cloning
• Docker bridge is optional — the app is fully playable with the 14 native engines alone
• Auto-updater removed — upstream's update mechanism targets Lucas Chess versioning and would corrupt a fork; see Releases for updates
• Modern macOS-first focus — this fork targets Apple Silicon and macOS; Intel and Windows/Linux users should use upstream

This is a modified work under GPL 3.0. The original Lucas Chess R6 is by Lucas Monge.

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Credits and licence

• Lucas Chess R6 — © Lucas Monge, GPL 3.0 — github.com/lukasmonk/lucaschessR6
• Stockfish — Tord Romstad, Marco Costalba, Joona Kiiski et al., GPL 3.0
• Lc0 — Gary Linscott, Folkert Huizinga et al., GPL 3.0
• Maia — Reid McIlroy-Young et al., MIT
• irina — upstream authors, GPL 3.0
• Drawfish — Nathan Rugg, GPL 3.0

All source pointers and licence texts are in bin/OS/darwin/Engines/SOURCES.md. This repository is licensed under GPL 3.0.

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Developer notes

# Install dependencies
python3.13 -m venv .venv && .venv/bin/pip install -r requirements.txt

# Run directly
cd bin && ../.venv/bin/python3 LucasR.py

• macOS platform entry point: bin/OS/darwin/OSEngines.py
• Native engine build scripts: tools/build_stockfish.sh, tools/build_lc0.sh, tools/build_drawfish.sh
• Engine provenance: bin/OS/darwin/Engines/SOURCES.md
• Docker wrapper generator: tools/gen_darwin_engines.py

The full implementation plan lives at .claude/plans/i-want-you-to-lazy-truffle.md.