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mux supports using remote hosts over SSH for workspaces. When configured, all tool operations will execute over SSH and the agent is securely isolated from your local machine. Our security architecture considers the remote machine potentially hostile. No keys or credentials are implicitly transferred there—just the git archive and Project Secrets. We highly recommend using SSH workspaces for an optimal experience:
  • Security: Prompt injection risk is contained to the credentials / files on the remote machine.
  • Performance: Run many, many agents in parallel while maintaining good battery life and UI performance
ssh workspaces The Host can be:
  • a hostname (e.g. my-server.com)
  • a username and hostname (e.g. user@my-server.com)
  • an alias from your ~/.ssh/config, e.g. my-server
  • anything that passes through ssh <host> can be used as a host
We delegate SSH configuration to the system’s ssh command, so you can set up advanced configuration for your agent host in your local ~/.ssh/config file. Here’s an example of a config entry: 
Host ovh-1
	HostName 148.113.1.1
	User root

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Authentication

As we delegate to ssh, this is really an abbreviated reference of how ssh authenticates.
There are a few practical ways to set up authentication.

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Local default keys

ssh will check these locations by default: 
~/.ssh/id_rsa
~/.ssh/id_ecdsa
~/.ssh/id_ecdsa_sk
~/.ssh/id_ed25519
~/.ssh/id_ed25519_sk

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SSH Agent

If you have an SSH agent running, you can add your key: 
ssh-add ~/.ssh/my_key_ecdsa
and ssh will use it to authenticate.

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Config

You can also configure authentication in your ~/.ssh/config file. 
Host my-server
	HostName 148.113.1.1
	User root
	IdentityFile ~/.ssh/id_rsa

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Coder Workspaces

If you’re using Coder Workspaces, you can use an existing Workspace as a mux agent host:
  1. Run coder config-ssh
  2. Use coder.<workspace-name> as your SSH host when creating a new mux workspace
Note that in this approach we’re multiplexing mux workspaces onto a single Coder workspace. This avoids the compute provisioning overhead to enable rapid creation and deletion of workspaces.