letee

Letee, pronounced luh-tee.
Every tmux session, local or remote, at your fingertips.

letee runs inside your existing terminal and works on top of tmux. No new terminal app, no replacement tmux setup, no retraining your keyboard muscle memory. Keep your terminal, tmux configuration, keybindings, plugins, and workflows while adding a persistent sidebar for finding, opening, and switching between sessions across your machine and SSH hosts. Your sessions remain ordinary tmux sessions; letee simply puts them within reach.

Track important sessions, see at a glance which ones need attention, and jump between local and remote work without hunting through terminal tabs.

Why letee?

• Keep your terminal and tmux setup: unlike cmux, letee runs inside your current terminal and builds on tmux instead of forcing a new terminal app. Your configuration, keybindings, plugins, and workflows keep working.
• One view across machines: local and remote sessions live in the same sidebar.
• Fast context switches: see which sessions need your attention via tmux bells, then jump straight to them.

Quick start

Requires Python 3.11+, tmux, and OpenSSH. Automatic coding-agent discovery additionally requires astatus locally and on configured remote hosts.

pip install letee
letee

That opens an outer tmux workspace with the letee sidebar on the left and your selected session on the right. Press Enter on a session to step into it; press q to close the sidebar, then C-s s to reopen it on Sessions.

How it works

letee creates or attaches to a dedicated outer tmux server. That outer layer owns only the layout:

• outer prefix: C-s
• focus/open Sessions: C-s s
• add session: C-s +
• focus/open Agents: C-s a
• hide sidebar: C-s h
• quit cockpit: C-s q
• show help: C-s ?
• detach cockpit: C-s d
• forward outer prefix to inner session: C-s C-s
• standard outer tmux prefix bindings: disabled
• outer status: off
• left pane: letee sidebar, 40 columns by default
• right pane: selected local/remote tmux attach client

Inner local and remote sessions keep their normal tmux prefix and bindings, and remain alive when you switch away. Only letee's outer prefix key table is restricted.

Configuration

Files live in ~/.config/letee/:

hosts = ["my-remote-machine"]
prefix = "C-s"
sidebar_width = 40
status_timeout = 5
persistent_ssh = true

Prefix

prefix accepts one non-empty, printable tmux key token without whitespace. sidebar_width sets left pane width in columns. status_timeout controls how many seconds sidebar feedback remains visible. Both numeric settings must be positive integers. Restart sidebar by rerunning letee after changing these values.

C-s normally sends XOFF when terminal IXON flow control is enabled. Attached tmux disables flow control on outer tty, so outer prefix works without global stty changes. Readline, Emacs, or Vim C-s commands require C-s C-s to forward literal C-s; inner tty may still treat it as XOFF, in which case C-q resumes output.

To restore old prefix, set prefix = "C-g" and rerun letee.

Remote hosts

Hosts are SSH aliases only. Keep host-specific users, ports, keys, proxies, IPv6, and other connection settings in ~/.ssh/config.

By default, letee makes OpenSSH reuse one authenticated transport per host with ControlMaster=auto, ControlPersist=10m, and ControlPath=~/.ssh/letee-%C. Later discovery polls, switches, creates, and kills avoid repeating TCP setup, key exchange, and authentication. Control sockets remain for 10 minutes after last use.

Every letee SSH connection also uses ServerAliveInterval=60 and ServerAliveCountMax=3 to detect dead connections and keep idle sessions active through network and NAT timeouts. Keepalive remains enabled when persistent_ssh is disabled.

To omit letee's persistence options, set:

persistent_ssh = false

SSH config still applies, so this opt-out does not disable multiplexing configured there.

Names of the hosts must match:

[A-Za-z0-9_.-]{1,64}

CLI commands

letee list
letee switch local:<session>
letee switch ssh:<host>:<session>
letee switch-session <1-9>
letee create local <session>
letee create ssh <host> <session>
letee kill local:<session>
letee kill ssh:<host>:<session>

Switching uses outer tmux respawn-pane on right pane. Real tmux sessions stay alive.

Sidebar keys

• C-s s: focus Sessions; recreates sidebar if quit
• C-s +: focus Sessions and open Add session menu
• C-s a: focus Agents; recreates sidebar if quit
• C-s h: hide sidebar
• C-s q: quit outer letee
• C-s ?: show help in right pane
• C-s d: detach outer letee
• C-s C-s: forward C-s to inner session
• C-s 1–C-s 9: switch directly to numbered tracked target
• j / k or arrows: move selection pointer (›) in focused region
• [ / ]: give Agents/Sessions region more rows for current run
• h / l: cycle agent ordering mode (Priority / Session) when ordering row is selected
• Enter: switch selected session or exact agent pane, or activate selected Add row
• a: open Add session menu from Sessions or Agents
• r: remove selected target without killing it
• K / J: move selected tracked target up/down without wrapping
• x: kill and remove selected tracked session (asks first)
• /: open existing-session search directly
• ?: open help in right pane
• q: quit sidebar only

› marks keyboard selection and left-pane focus; mint reverse highlight marks active cockpit session independently. Unfocused sidebar hides pointer, leaves sidebar colors unchanged, and keeps active session highlighted and visible.

Normal sidebar lists sessions in persisted order. Add menu separates New session from Existing session. New-session flow skips location selection when exactly one local/SSH location is available; multiple locations use dedicated picker, then dedicated name input. Existing-session search lists only untracked sessions. Selecting or creating one persists it and switches immediately. Independently navigable Agents region remains visible below AGENTS divider when Add menu is closed. First nine sessions receive shortcut numbers; K/J updates order. Missing sessions remain launchers: Enter uses tmux new-session -A to recreate and attach. Sessions persist in ~/.config/letee/sessions. Only tracked sessions trigger sidebar bell indicators and beeps. Set LETEE_ASCII=1 for text-only labels and ellipses.

Agent discovery

Letee discovers coding agents by reading astatus JSON status files. The astatus plugin for your coding agent is required for detection — install it in each agent you want letee to discover. See the astatus documentation for full setup instructions and configuration.

Getting started with coding agents

Agent discovery requires the astatus plugin for your coding agent. The plugin emits JSON status files that letee reads to show agent state in the sidebar.

Codex (OpenAI Codex CLI)

pip install agent-status
codex plugin marketplace add julsemaan/astatus
codex plugin add agent-status@astatus

Start Codex in any repo, open /hooks, and trust the agent-status hooks. First prompt starts a detached sidecar that emits 20-second heartbeats.

Pi (pi-coding-agent)

pi install git:github.com/julsemaan/astatus

Then run /reload or restart pi.

OpenCode

Add the astatus plugin to opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["agent-status-opencode"]
}

Then start or restart OpenCode. OpenCode installs the plugin from npm automatically.

Run letee — agents appear automatically in the Agents sidebar (C-s a).

How agent discovery works

Agent records are read from $AGENT_STATUS_DIR, $XDG_STATE_HOME/agent-status, or ~/.local/state/agent-status, in that order. Local and remote running agents updated within 60 seconds are correlated by exact tmux socket and pane ID. Selecting agent navigates to exact server, window, and pane; active agent name and location remain orange independently of keyboard selection. Working agents show for <duration>; other states show no duration. Working durations prefer task.status_timestamp and fall back to runtime.updated_at; unusable optional timestamps omit duration. Each agent row starts with a semantic status icon; working agents use an animated Braille spinner. Focused selection replaces that icon with ›, and moving focus away restores it. Status icon and text share semantic color; selection cursor stays orange. LETEE_ASCII=1 uses ASCII icons, spinner frames, and > cursor. Attention states remain bold and idle/canceled remain dim without color. Agents are discovered automatically, but only agents in tracked sessions appear. Agents cannot be added, removed, reordered, or killed as favorites.

Agent alerts

When a tracked agent changes from working to idle, completed, input-required, auth-required, failed, rejected, or canceled, sidebar beeps once and marks that exact pane/agent with 🔔 (BELL in ASCII mode). Initial discovery does not alert. Marker survives later state changes until exact pane opens, is already active during discovery, disappears from discovery, or sidebar restarts.

Mouse controls

• click session row: select and switch
• right-click tracked session: open native tmux menu to remove it or kill it with confirmation; right-click does not switch sessions
• drag tracked session: reorder it; hovering ↑ more or ↓ more auto-scrolls, and leaving sidebar drops at current insertion line
• click ＋ add, Add choice, or available location row: activate same flow as Enter
• wheel over sidebar: navigate selectable session and host rows
• right-pane mouse events: forwarded by outer tmux to mouse-aware applications
• live border dragging: disabled so text selection can cross the sidebar divider without resizing it

Tmux mouse capture may require holding Shift for terminal-native text selection.

Clipboard

Native tmux copy mode forwards copied text through nested sessions using OSC 52. Physical terminal must support and enable OSC 52 clipboard access. letee declares inner clients as clipboard capable and sets outer server option set-clipboard on; inner tmux configuration remains unchanged, including explicit set-clipboard off.

Security: set-clipboard on permits processes in local and remote panes to set system clipboard through OSC 52. Only connect to trusted hosts and run trusted pane processes.

Recovery

Press C-s s to restart/focus Sessions, C-s a to restart/focus Agents, or C-s + to open Add session menu. Or rerun:

letee

It reuses valid cockpit, repairs broken window, and respawns missing sidebar.

Development

make dev-install
make test          # unit tests
make lint          # Ruff
make coverage      # branch coverage (85% minimum)
make build-check   # build distributions and validate metadata
make check         # all quality gates

License

Licensed under the Apache License 2.0.

Missing cockpit for switch/create prints:

No valid letee. Run: letee