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Integration

Fleet + tmux: Each Agent Gets Its Own Isolated Terminal Session

tmux is the execution substrate for every Fleet agent. When you start an agent with fleet agent start, Fleet creates a named tmux session, injects the agent's environment variables (name, role, repo, owner, task title, and more), and launches the agent process inside it. The session stays alive between runs, preserving scrollback and context. Fleet determines whether an agent is running by checking tmux has-session at runtime — there is no separate status field in the database.

This design means you can attach to any agent session directly to watch it work in real time, or detach and let it run in the background. Multiple agents run in parallel as separate tmux sessions without shared state.

Setup

1

Install tmux (required by Fleet)

# macOS
brew install tmux

# Ubuntu/Debian
apt install tmux
2

Verify tmux is available

fleet doctor
3

Start an agent and attach to its session

fleet agent start backend-developer
tmux attach -t backend-developer

What you gain

  • Sessions persist across SSH disconnects and terminal closures, so agents keep running even if your local session drops
  • You can attach to any agent's tmux session for live observation without disrupting its execution
  • Agent status is derived from `tmux has-session` at runtime, so it always reflects reality rather than a stale database flag

Honest limits

  • tmux must be installed on the machine running Fleet; it is a hard dependency, not optional
  • Fleet derives tmux session names from agent names, so pre-existing sessions with the same names can collide
  • Environment-variable injection happens at launch; changing an agent's config requires restarting its session

Frequently asked questions

What happens if I kill a tmux session manually?

Fleet reports the agent as not running the next time it checks, since status comes from `tmux has-session`. Restart it with `fleet agent start`.

Can Fleet agents run without tmux?

No. tmux is a hard requirement. Session lifecycle, environment-variable injection, and status checking all depend on it.

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