A pier where your sessions dock. pier takes one tmux pane and fills it with every running session — which worktree and branch each one is on, whether it's working or waiting for you — and jumps to any of them with a single click. Not a second app to run alongside, just one more pane in the terminal you already keep open.
brew install zkzofn/tap/pierThe round trip
Two Claude Code sessions in, you start doing the rounds — cycling through windows to find the one that stopped and wants an answer. Three sessions in, the rounds cost more than the work.
tmux already knows which panes exist. pier reads that, asks Claude Code's hooks what each one is doing, and puts the answer in a column you never have to leave.
Recorded by Claude Code hooks, picked up by the sidebar through fsnotify.
What it does
pier sits in a tmux pane. Your prefix key, your config, your muscle memory — all of it stays.
Every running Claude Code instance across all your tmux sessions, grouped by worktree — path and branch. Sessions with no Claude Code pane are listed too, marked $, so a plain shell stays visible and jumpable.
prefix + g show / hide the sidebar
Claude Code hooks record what each pane is doing and the sidebar picks the change up instantly. Working, waiting for your input, or waiting for you to approve a permission — the answer is a glyph, not a tour of your windows.
● working ○ waiting ! permission
Click an item to focus it, even when it lives in a different tmux session. With the sidebar focused, j and k move and Enter jumps. Item labels carry the prompt you last submitted there, so you know what you left running.
prefix + ← focus the sidebar
prefix+N opens the picker with your current session on top and the cursor already on it, so Enter means "one more Claude Code here". Type to filter directories, ^S for a plain shell instead, Tab to rename before it starts.
prefix + N then Enter
A conversation lost to a crash, power loss, or OS shutdown grows an ↻ resume button in the picker, and ↻ restore all rebuilds the whole pre-shutdown layout in one stroke. Resuming is always an explicit choice, never automatic.
↻ resume ↻ restore all
Outside tmux it opens the picker and attaches to whatever you pick. Inside tmux it runs claude in the current pane. Flags like -r pass straight through, and a word pier does not know is an error — so a typo never starts a session.
pier -r → claude -r
How it works
State files are decoration. Even if every hook dies, the list of sessions stays correct.
Every two seconds the sidebar runs list-panes -a and detects Claude Code panes by process name or version string.
pier hook runs as a child of Claude Code, so it inherits the pane and maps to it exactly. No resident process.
State lands in a file per pane and the TUI picks the change up instantly, without waiting for the next poll.
Keyboard
Click ? help at the bottom of the sidebar and pier shows you this same list, in a popup.
Footprint
tmux's model means one sidebar per session. Measured on macOS (Apple Silicon), RSS.
| Item | Measured |
|---|---|
| One sidebar | 7.1 – 9.7 MB (avg 8.1 MB) |
| Total with 6 sessions | 48.8 MB |
| pier hook / pier status | No resident process (a few ms per event) |
| Binary size | 5 MB |
Tagging a release runs the tests, builds the binaries, publishes the GitHub Release from the CHANGELOG, and bumps the Homebrew formula — in one pass, or not at all.
Install
The first pier run offers to wire tmux and the Claude Code hooks, and to add a shell alias. Say no to either and run it later.
brew install zkzofn/tap/pierpiergit clone https://github.com/zkzofn/pier.git cd pier make setup # build, install to ~/.local/bin, wire it up pier
Homebrew ships a prebuilt binary; Go 1.24+ is only needed for a source build.
pier upgrade asks the tap right now and runs the Homebrew upgrade for you. A pier start checks once a day on its own, and while a newer version is out every sidebar carries an↑ version · pier upgrade line.
PIER_NO_UPDATE_CHECK=1 silences both.
Questions
pier is developed and verified on macOS. Linux should work but is unverified — a source build has been seen bringing the sidebar up on tmux 3.4, but the hook and Claude Code wiring has not been checked there. Release binaries are built for darwin/arm64 and darwin/amd64.
pier setup appends one marked block to ~/.tmux.conf and merges six hook entries into ~/.claude/settings.json. Existing settings are preserved, a .bak-pier backup of settings.json is written first, re-running never duplicates anything, and a running tmux server is reloaded on the spot.
Everything but the status icons, prompt labels, and crash recovery still works — sidebar, jump, and status bar are driven by tmux itself. The icons just stay at · (unknown).
tmux is the source of truth. Every two seconds the sidebar polls tmux list-panes -a and detects Claude Code panes directly. The hook state files are decoration — even if the hooks die, the list stays correct.
brew update && brew upgrade zkzofn/tap/pier, or pier upgrade from inside pier, which asks the tap right now and runs the upgrade for you. While a newer version is out, every sidebar carries an ↑ version · pier upgrade line at the bottom.
One command, then pier. The wizard handles the rest, and everything it writes is a marked block it can find again.
brew install zkzofn/tap/pier