Trellis

A terminal app for macOS with a side-panel UI, workspaces, and native notifications — built for engineers juggling parallel sessions.

Overview

Trellis is a macOS terminal reimagined around how engineers actually work today: multiple sessions running side by side, each demanding attention at different times.

Instead of buried tabs or split panes you lose track of, Trellis gives you a side-panel layout with workspace-based organization. Switch between contexts with tabs, keep long-running processes visible, and let OSC 777/9 notifications surface what matters — as desktop alerts, badge counts, or focus shifts — so nothing slips through.

Built for workflows where you're running multiple Claude Code instances, watching build pipelines, and tailing logs all at once.

Features

• Workspaces — Isolated contexts with independent layouts. Switch between projects without losing state.
• Split panes — Horizontal and vertical splits with draggable dividers. Recursive nesting supported.
• Tab system — Each area holds multiple tabs. Drag tabs between areas or drop them on edges to create new splits.
• Native notifications — OSC 9/777 desktop notifications with per-tab badge counts and click-to-focus.
• Built-in browser — Side-by-side documentation browsing without leaving the terminal.
• File tree — Directory browser with preview pane and .gitignore-aware filtering.
• CLI control — Control panels from any terminal via the trellis command (tmux-style).

Tech

• Terminal engine: libghostty (GPU-accelerated via Metal)
• GUI: SwiftUI + AppKit
• Build: Nix Flakes + Make

Install

Download the latest .dmg from Releases, open it, and drag Trellis to Applications.

Note: Trellis is not signed with an Apple Developer certificate. macOS will block the app on first launch with "Trellis is damaged and can't be opened." This is a Gatekeeper restriction, not an actual problem with the app.

To run it, remove the quarantine attribute after copying to Applications:

xattr -d com.apple.quarantine /Applications/Trellis.app

CLI Control

Trellis ships with a built-in CLI for controlling panels from any terminal — useful for AI agent workflows where one agent needs to spawn or communicate with another.

Setup: Enable in Settings → CLI Control → Allow external CLI control.

The trellis binary (the app itself) doubles as the CLI client when invoked with a subcommand.

# List all terminal panels
trellis list-panels

# Send keys to the active panel (or create a new one if no --panel given)
trellis send-keys 'codex .' Enter          # new panel, prints its id to stdout
trellis send-keys --panel s:<id> 'hi' Enter  # existing panel

Agent-to-agent example — Claude Code spawns Codex in a new panel, Codex reports back when done:

# Claude Code side: start Codex in a new panel, capture the panel id
CODEX_PANEL=$(trellis send-keys 'codex .' Enter)

# Codex side: when finished, notify Claude Code's panel
trellis send-keys --panel s:<cc-panel-id> 'LGTM!' Enter

Reference:

Command	Description
trellis list-panels	JSON list of all terminal panels with id, title, pwd, workspace
trellis send-keys [--panel|-p <id>] <keys> [Enter]	Send text to a panel. Omit --panel to create a new panel. Enter appends a newline.

Notes:

• Panel ids are in s:<UUID> format; use list-panels to discover them.
• --panel / -p are equivalent.
• Enter is a special token that appends \n; other keys like Tab or Ctrl sequences (\x03 = Ctrl+C) can be embedded directly in the string.
• When --panel is omitted, the new panel id is printed to stdout, making it pipeable.

Development

See docs/dev.md for setup instructions.

# Prerequisites: Xcode, Nix, direnv
direnv allow
make setup   # Build libghostty (first time only)
make run     # Build and launch Trellis.app

License

TBD