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Overview

typemux-cc supports three Python LSP backends. You can switch between them using the TYPEMUX_CC_BACKEND environment variable.

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Available Backends

Pyright is the default backend if TYPEMUX_CC_BACKEND is not set.
BackendCommandStatus
pyrightpyright-langserver --stdio✅ Stable (default)
tyty server🧪 Experimental (verified)
pyreflypyrefly lsp🧪 Experimental (verified)

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Installation Instructions

Pyright is the default and most stable backend. 
# Via npm (recommended)
npm install -g pyright

# Via pip (alternative)
pip install pyright
Verify installation: 
which pyright-langserver

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ty (Experimental)

ty is a new Python type checker by the creators of uv (Astral). 
# Via pip
pip install ty

# Via uvx
uvx ty
Verify installation: 
which ty
ty is experimental but verified to work with typemux-cc.

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pyrefly (Experimental)

pyrefly is Meta’s Python type checker. 
# Via pip
pip install pyrefly
Verify installation: 
which pyrefly
pyrefly is experimental but verified to work with typemux-cc.

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Backend Selection

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Via Configuration File

Create or edit ~/.config/typemux-cc/config: 
mkdir -p ~/.config/typemux-cc
cat > ~/.config/typemux-cc/config << 'EOF'
# Select backend (pyright, ty, or pyrefly)
export TYPEMUX_CC_BACKEND="pyright"
EOF

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Via Environment Variable

# One-time use
TYPEMUX_CC_BACKEND=ty ./target/release/typemux-cc

# For current session
export TYPEMUX_CC_BACKEND=ty

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Via CLI Flag

./target/release/typemux-cc --backend ty

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Backend-Specific Notes

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Pyright

  • Most mature: Production-ready with extensive type checking features
  • Default choice: Automatically selected if TYPEMUX_CC_BACKEND is not set
  • Installation: Available via both npm and pip
  • Best for: General Python development, maximum compatibility

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ty

  • Performance focused: Built by Astral (creators of uv and ruff)
  • Experimental: Newer project, still under active development
  • Best for: Users who want cutting-edge performance
  • Note: Some advanced type features may not be fully supported yet

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pyrefly

  • Meta-backed: Developed by Facebook/Meta
  • Experimental: Less widely adopted than pyright
  • Best for: Projects already using Meta’s Python tooling
  • Note: Smaller ecosystem and community compared to pyright

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Common Issues

Make sure the backend command is available in your PATH before starting typemux-cc. Use which <command> to verify.

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Backend not found

# Check if backend is in PATH
which pyright-langserver  # for pyright
which ty                  # for ty
which pyrefly            # for pyrefly

# Check typemux-cc logs
tail -100 /tmp/typemux-cc.log

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Wrong backend being used

Verify your configuration: 
# Check environment variable
echo $TYPEMUX_CC_BACKEND

# Check config file
cat ~/.config/typemux-cc/config

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Backend crashes

Enable detailed logging: 
RUST_LOG=trace TYPEMUX_CC_LOG_FILE=/tmp/typemux-cc.log
Then check the logs for backend-specific error messages.