> ## 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.

# SSH Runtime

> Run agents on remote hosts over SSH for security and performance

Mux can run workspaces on a remote host over SSH. When configured, tool operations (file reads/edits, `bash`, etc.) execute on the remote machine.

## Threat model

Mux treats the remote host as potentially hostile. By default it does **not** forward your local keys or credentials.

The only data synced to the remote machine is:

* a git archive of the project
* [Project Secrets](/config/project-secrets) (explicitly configured)

## Why use SSH runtime

* **Security**: Prompt injection risk is contained to the credentials/files on the remote machine.
  * SSH remotes pair well with [Agentic Git Identity](/config/agentic-git-identity).
* **Performance**: Run many agents in parallel without burning laptop CPU/battery.

<img src="https://mintcdn.com/mux/b6cj0iIb5Ljk3RY5/img/new-workspace-ssh.webp?fit=max&auto=format&n=b6cj0iIb5Ljk3RY5&q=85&s=127eb9965f68f6a81333264489663909" alt="ssh workspaces" width="3234" height="1958" data-path="img/new-workspace-ssh.webp" />

## Host value

The host field accepts anything you can pass to `ssh <host>`:

* a hostname (for example `my-server.com`)
* a username and hostname (for example `user@my-server.com`)
* an alias from your `~/.ssh/config` (for example `my-server`)

Mux delegates SSH configuration to your system `ssh` command, so advanced settings live in `~/.ssh/config`.

Example entry:

```text theme={null}
Host ovh-1
  HostName 148.113.1.1
  User root
```

## Authentication

<Info>
  Mux delegates to `ssh`. This is an abbreviated reference of common ways `ssh` authenticates.
</Info>

### Local default keys

`ssh` checks these locations by default:

```text theme={null}
~/.ssh/id_rsa
~/.ssh/id_ecdsa
~/.ssh/id_ecdsa_sk
~/.ssh/id_ed25519
~/.ssh/id_ed25519_sk
```

### SSH agent

If you have an SSH agent running, add your key:

```bash theme={null}
ssh-add ~/.ssh/my_key_ecdsa
```

### `~/.ssh/config`

You can also set an explicit identity file:

```text theme={null}
Host my-server
  HostName 148.113.1.1
  User root
  IdentityFile ~/.ssh/id_rsa
```

## Coder Workspaces

If you use [Coder](https://coder.com), see the [Coder runtime](/runtime/coder) page.