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Terminal backend

Every agent Overdeck runs lives in a terminal-backend pane. The default backend is Herdr, a terminal workspace manager with a headless server per session. tmux is still supported, but only when you ask for it. Herdr is strict: if it is selected and its binary or this home’s session server is missing, agent launches fail with an error that names pan install. Overdeck never falls back to tmux silently.

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Selection

Overdeck picks the backend from these sources, in order:
  1. The OVERDECK_TERMINAL_BACKEND environment variable (herdr or tmux).
  2. terminal.backend in ~/.overdeck/config.yaml:
  3. Otherwise herdr.
Selection is a policy, not a probe: a missing herdr binary does not change it. Availability is checked separately, every time an agent launches — the herdr binary on PATH or in ~/.local/bin, and the session socket for this Overdeck home (~/.config/herdr/sessions/<session>/herdr.sock, where <session> is overdeck for the default ~/.overdeck home). The dashboard logs the result once at boot:
When Herdr is selected but unavailable, that line is an error that starts with UNAVAILABLE: and says what is missing.

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What pan install and pan sync do

Both commands run the same Herdr setup:
  • Binary. If herdr is missing, it is installed with the vendor installer (curl -fsSL https://herdr.dev/install.sh | sh) into ~/.local/bin. An installer-managed binary is kept on the stable channel; a binary installed by Homebrew, mise or Nix is verified but never changed.
  • Config. ~/.config/herdr/config.toml gets:
    Herdr’s default is true, which relaunches every agent pane with its native resume after a Herdr server restart. That would bypass Overdeck’s own resume gates, so agents you paused, stopped, or that a pipeline gate is holding would come back on their own. The file is edited line by line: your comments and other settings stay exactly as they were. The result is checked with herdr config check, and a running server reloads it with herdr server reload-config.
  • Session server. One headless herdr --session <session> server per Overdeck home. On a systemd host it runs as the user unit <session>-herdr.service — overdeck-herdr.service for the default home. Elsewhere it is started detached, logging to ~/.overdeck/logs/herdr-<session>.log. pan up also makes sure this server is running.
  • Integrations. Herdr integrations report an agent’s lifecycle to Herdr directly instead of Herdr reading the screen. Overdeck installs the pilot set — pi, omp, kimi (Kimi Code 0.14.0 or later) and opencode — for each harness whose binary is installed. claude, codex and hermes only report session identity, which Overdeck does not use yet, so Overdeck neither installs nor removes them.
The Herdr step is skipped under CI, under Vitest, when the backend is explicitly tmux, and with pan install --skip-herdr. Re-running either command is safe: with everything in place it installs nothing and writes nothing.

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Updates

Overdeck compares the installed version with https://herdr.dev/latest.json (an unreachable manifest skips the check; it is never an error).
  • pan install runs herdr update when a newer stable release exists.
  • pan sync runs herdr update only when no session server is running for this home. When one is running, it prints the manual steps instead.
  • pan up never updates.
Nothing ever restarts the session server automatically. A restart closes every agent pane, so it is always your call: run systemctl --user restart overdeck-herdr.service at a quiet moment. pan doctor warns when the running server is older than the installed binary.

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pan doctor rows

Under an explicit tmux backend, only the Terminal backend row is shown.

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Opting into tmux

Set the backend in ~/.overdeck/config.yaml:
or export OVERDECK_TERMINAL_BACKEND=tmux. With terminal.backend: tmux, Overdeck skips all Herdr setup and runs agents on the tmux -L overdeck socket.

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Claude Code hooks

If you install Herdr’s claude integration yourself, it adds a SessionStart hook to ~/.claude/settings.json. Overdeck registers its own SessionStart hook in the same list. Claude Code runs all matching hooks for an event in parallel, and the two are independent: Herdr’s reports the session to Herdr; Overdeck’s injects context and starts the heartbeat. pan sync never removes Herdr’s entry, and Herdr’s installer does not remove Overdeck’s. pan doctor warns if Herdr’s claude integration is installed while Overdeck’s SessionStart hook is missing.