> ## Documentation Index
> Fetch the complete documentation index at: https://mux-mike-promote-experiments.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Runtimes

> Configure where and how Xum executes agent workspaces

Runtimes determine where and how Xum executes agent workspaces.

| Runtime | Isolation | Best For |
| - | - | - |
| **[Local](/runtime/local)** | All workspaces share the project directory | Quick edits to your working copy |
| **[Worktree](/runtime/worktree)** | Each workspace gets its own directory | Running multiple agents in parallel |
| **[SSH](/runtime/ssh)** | Remote execution over SSH | Security, performance, heavy parallelism |
| **[Docker](/runtime/docker)** | Isolated container per workspace | Full isolation, reproducible environments |
| **[Dev Container](/runtime/devcontainer)** | Container from devcontainer.json | Projects with existing devcontainer configs |

## Choosing a Runtime

Choose a runtime when creating a workspace.

## Init Hooks

[Init hooks](/hooks/init) and agent bash tool executions can detect the runtime type via the `XUM_RUNTIME` environment variable:

* `local` — Local runtime
* `worktree` — Worktree runtime
* `ssh` — SSH runtime
* `docker` — Docker runtime
* `devcontainer` — Dev Container runtime

This lets your init hook adapt behavior, e.g., skip worktree-specific setup when running in local mode.