> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/K-dash/typemux-cc/llms.txt
> Use this file to discover all available pages before exploring further.

# Supported Backends

> LSP backends compatible with typemux-cc

## Overview

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

## Available Backends

<Note>
  Pyright is the default backend if `TYPEMUX_CC_BACKEND` is not set.
</Note>

| Backend                                         | Command                      | Status                     |
| ----------------------------------------------- | ---------------------------- | -------------------------- |
| [pyright](https://github.com/microsoft/pyright) | `pyright-langserver --stdio` | ✅ Stable (**default**)     |
| [ty](https://github.com/astral-sh/ty)           | `ty server`                  | 🧪 Experimental (verified) |
| [pyrefly](https://github.com/facebook/pyrefly)  | `pyrefly lsp`                | 🧪 Experimental (verified) |

## Installation Instructions

### Pyright (Recommended)

Pyright is the default and most stable backend.

```bash theme={null}
# Via npm (recommended)
npm install -g pyright

# Via pip (alternative)
pip install pyright
```

Verify installation:

```bash theme={null}
which pyright-langserver
```

### ty (Experimental)

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

```bash theme={null}
# Via pip
pip install ty

# Via uvx
uvx ty
```

Verify installation:

```bash theme={null}
which ty
```

<Info>
  ty is experimental but verified to work with typemux-cc.
</Info>

### pyrefly (Experimental)

pyrefly is Meta's Python type checker.

```bash theme={null}
# Via pip
pip install pyrefly
```

Verify installation:

```bash theme={null}
which pyrefly
```

<Info>
  pyrefly is experimental but verified to work with typemux-cc.
</Info>

## Backend Selection

### Via Configuration File

Create or edit `~/.config/typemux-cc/config`:

```bash theme={null}
mkdir -p ~/.config/typemux-cc
cat > ~/.config/typemux-cc/config << 'EOF'
# Select backend (pyright, ty, or pyrefly)
export TYPEMUX_CC_BACKEND="pyright"
EOF
```

### Via Environment Variable

```bash theme={null}
# One-time use
TYPEMUX_CC_BACKEND=ty ./target/release/typemux-cc

# For current session
export TYPEMUX_CC_BACKEND=ty
```

### Via CLI Flag

```bash theme={null}
./target/release/typemux-cc --backend ty
```

## Backend-Specific Notes

### 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

### 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

### 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

## Common Issues

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

### Backend not found

```bash theme={null}
# 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
```

### Wrong backend being used

Verify your configuration:

```bash theme={null}
# Check environment variable
echo $TYPEMUX_CC_BACKEND

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

### Backend crashes

Enable detailed logging:

```bash theme={null}
RUST_LOG=trace TYPEMUX_CC_LOG_FILE=/tmp/typemux-cc.log
```

Then check the logs for backend-specific error messages.