> ## Documentation Index
> Fetch the complete documentation index at: https://mux.coder.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Environment Variables

> Environment variables available in agent bash commands and hooks

The following environment variables are available in all agent bash tool executions, including [init hooks](/hooks/init).

## Available Variables

| Variable             | Description                                                                                                                   |
| -------------------- | ----------------------------------------------------------------------------------------------------------------------------- |
| `MUX_PROJECT_PATH`   | Absolute path to the project root on the **local machine**. Always refers to your local project path, even on SSH workspaces. |
| `MUX_RUNTIME`        | Runtime type: `"local"`, `"worktree"`, `"ssh"`, or `"docker"`                                                                 |
| `MUX_WORKSPACE_NAME` | Name of the workspace (typically the branch name)                                                                             |
| `MUX_MODEL_STRING`   | Model identifier (e.g., `"anthropic:claude-sonnet-4-20250514"`)                                                               |
| `MUX_THINKING_LEVEL` | Reasoning level: `"off"`, `"low"`, `"medium"`, `"high"`, or `"xhigh"`                                                         |
| `MUX_COSTS_USD`      | Cumulative session costs in USD, formatted to 2 decimal places (e.g., `"1.23"`)                                               |

## Usage Example

```bash theme={null}
#!/usr/bin/env bash

echo "Project: $MUX_PROJECT_PATH"
echo "Runtime: $MUX_RUNTIME"
echo "Workspace: $MUX_WORKSPACE_NAME"
echo "Model: $MUX_MODEL_STRING"
echo "Thinking: $MUX_THINKING_LEVEL"
echo "Costs: \$${MUX_COSTS_USD:-0.00}"

# Runtime-specific behavior
if [ "$MUX_RUNTIME" = "ssh" ]; then
  echo "Running on SSH remote"
elif [ "$MUX_RUNTIME" = "docker" ]; then
  echo "Running in Docker container"
else
  echo "Running locally"
fi
```

## Use Cases

* **PR footers**: Include model and cost information in automated PR descriptions
* **Conditional logic**: Adapt scripts based on runtime environment
* **Logging**: Track which model and settings were used for a task
* **Cost monitoring**: Check cumulative costs before expensive operations