> ## 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.

# Dev Container Runtime

> Run agents in containers defined by devcontainer.json

Dev Container runtime runs each workspace in a container built from your project's [devcontainer.json](https://containers.dev/implementors/json_reference/). If your project already uses dev containers for VS Code or other editors, Mux can use the same configuration.

## Requirements

* [Dev Container CLI](https://github.com/devcontainers/cli): `npm install -g @devcontainers/cli`
* Docker daemon running
* A `devcontainer.json` in the project

## How it works

1. Mux creates a git worktree on the host machine
2. Runs `devcontainer up` to build/start the container
3. Commands execute inside the container via `devcontainer exec`
4. Deleting the workspace stops the container and removes the worktree

## Configuration

Select Dev Container in the workspace creation UI. If your project has multiple configs, choose one from the dropdown.

Mux searches these locations:

* `.devcontainer.json`
* `.devcontainer/devcontainer.json`
* `.devcontainer/*/devcontainer.json` (named configs)

## Credential sharing

Like the [Docker runtime](/runtime/docker), you can check "Share credentials" to enable git authentication inside the container:

* **SSH agent forwarding** — Your SSH keys work without copying private keys
* **Git config** — Host `~/.gitconfig` is copied into the container
* **GitHub CLI** — If `GH_TOKEN` is set in [project secrets](/config/project-secrets), it's passed to the container

## Filesystem layout

Worktrees live on the host at `~/.mux/src/<project>/<workspace>`. The container mounts this directory (location inside the container depends on your devcontainer.json `workspaceFolder`).

## Notes

* The Dev Container runtime button only appears if Mux finds a `devcontainer.json` in the project.