Blink

Your terminal pane lights up when your coding agent needs you.
Stop checking every pane: the agent waiting for a permission, an answer or your next message glows amber until you look.

Install for Claude Code, Codex or Copilot CLI

When Claude Code, Codex CLI or GitHub Copilot CLI needs you (a permission, a question, a plan to approve, or simply the end of its answer), Blink lights up that agent's own terminal pane. In Ghostty the whole pane pulses amber while you work elsewhere, and stops as soon as you type in it.

• Nothing to launch. Open any terminal window and start claude, codex or copilot as usual: no wrapper, no alias. Windows that were already open work too.
• Only the waiting pane. The other panes, including the one you are typing in, stay untouched.
• No idle cost. 0 % CPU while nothing waits, ~1.4 % while a pane pulses.
• No dependencies. Python 3.9+ standard library. No prompt or conversation text is ever stored.

Note

Experimental. Used on macOS with Ghostty 1.3.1, Claude Code and Copilot CLI. Codex CLI and iTerm2 are only covered by automated tests so far.

Install

git clone https://github.com/n-pizzetta/blink.git
cd blink
python3 blink.py install

Agents that were already running need a restart to load the hooks. Codex asks you to trust new hooks once: run /hooks in Codex and approve Blink's. This is Codex's own review; Blink does not bypass it.

Keep the clone where it is, since the hooks point to it. After moving it, run install again.

python3 blink.py doctor      # what is installed, which agents are waiting
python3 blink.py uninstall   # remove everything install added

What install changes

Target	Change
Claude Code	Blink's hooks merged into ~/.claude/settings.json; your other hooks are kept
Codex CLI	Blink's hooks merged into ~/.codex/hooks.json
Copilot CLI	~/.copilot/hooks/blink.json
Ghostty	A marked block in your Ghostty config: config-file = ?<clone>/.runtime/ghostty.conf, then a live reload

Agents that are not installed are skipped. CLAUDE_CONFIG_DIR, CODEX_HOME, COPILOT_HOME and XDG_CONFIG_HOME are honored. Hooks run with /usr/bin/python3 when it is a real interpreter, so they survive mise or pyenv upgrades; otherwise with the Python that ran install.

If you delete the clone without uninstalling, Ghostty ignores the missing file and the hooks fail silently; uninstall from a fresh clone cleans both up.

Terminals

Terminal	Signal
Ghostty	The whole pane pulses amber, only while you are not looking at it. A hidden tab is not drawn: it gets the bell, shown as 🔔 in its title with bell-features = title
iTerm2	Amber tab color and a "waiting for you" badge on the pane, plus the bell
tmux, screen, Terminal.app, WezTerm, kitty, VS Code…	The bell

Detection uses TERM_PROGRAM. SSH sessions are not covered.

What signals

CLI	Signals	Never signals
Claude Code	PermissionRequest, AskUserQuestion, ExitPlanMode, permission and elicitation notifications, Stop	idle_prompt, authentication, subagents
Codex CLI	PermissionRequest, request_user_input (when Codex emits PreToolUse for it), Stop	subagents
Copilot CLI	notification.permission_prompt, ask_user, notification.elicitation_dialog, agentStop	permissionRequest (fires before auto-approval), agent_idle

A question asked in the text of an answer is covered by the end of turn: no keyword matching, no transcript reading. A turn that is still running, for example waiting for a background agent, signals once it ends.

The signal stops when you type in the pane or send a new prompt, when the agent resumes work, or when it exits.

How it works

1. A hook fires and finds the agent as its nearest non-shell parent process, then takes that process's terminal (ps -o tty). An agent without a terminal, such as a headless claude -p run by another agent, is ignored.
2. A small watcher process writes the signal to that terminal device. For Ghostty it sets palette slot 255 to a marker color (OSC 4) whose last byte is the pulse intensity; shaders/attention.glsl tints the pane when it sees the marker and the pane is not focused.
3. When the request is over, the watcher resets the palette (OSC 104) and exits. Typing is detected through the terminal's input access time, the same value w uses for idle times: Blink never reads your keystrokes.

Hooks only observe: they never approve, deny, or print anything the agent reads. State lives in ~/.cache/blink/ and holds session IDs, a pid, a terminal name and pending request kinds. Sessions whose agent exited, or that a new session replaced in the same pane, are forgotten.

Energy

Ghostty's usual way to animate a shader, custom-shader-animation = always, renders every visible pane continuously, even when nothing waits. Measured on one visible Ghostty 1.3.1 surface (Apple Silicon, ps CPU time over 20 s):

Mode	CPU	Energy impact
No custom shader	0 %	0
A shader with the animation loop (always)	6–7 %, permanently, per visible pane	12–16
Blink, nothing waiting	0 %	0
Blink, one pane pulsing	~1.4 %	~1.7

Blink sets custom-shader-animation = false, so Ghostty only redraws a pane when its content changes. While a request is pending, the watcher rewrites the pane's palette ~15 times per second, which redraws that pane alone. Hidden tabs and windows are not rendered at all. This setting also stops the animation of any other custom shader you use.

Limits

• The signal is written to the pane's terminal from outside the agent. A write could in theory land in the middle of a large frame the agent is drawing, causing a one-frame glitch.
• Palette slot 255 is reserved while a pane pulses. Text drawn with that indexed color is recolored meanwhile, then reset to your theme's value.
• iTerm2 tab colors are per tab, not per split; the badge is per pane.
• Used on macOS only. On Linux the automated tests pass, but the kernel updates a terminal's access time at most every 8 seconds: typing right after the signal starts can go unnoticed until you type again. The Ghostty step of install looks for the macOS app (--app).
• Blink relies on how each CLI runs its hooks. Verified with Claude Code 2.1.296, Codex CLI 0.162.0, Copilot CLI 1.0.95 and Ghostty 1.3.1; a later version can change that. doctor is the first thing to run if a pane stays dark.

Demo without an agent

python3 blink.py demo

Opens a separate Ghostty instance with a temporary configuration (yours is not touched) and four panes. Session 2 asks for an answer after eight seconds.

• Click the waiting pane: the pulse stops, status "seen".
• Enter: answer. b: new request in four seconds, then switch pane.
• p: pulse right now. q: close this demo pane.

If macOS blocks automation, add panes with Cmd+D / Cmd+Shift+D, or start with python3 blink.py demo --single. From another shell, python3 blink.py status, wait 2 and clear 2 drive the last demo.

Development

python3 -m unittest discover -s tests -v

The tests run the real hooks from a fake agent in a real pseudo-terminal, for all three CLIs and the three terminal kinds. No model, credentials or network. See CONTRIBUTING.md before opening a pull request.

References: Ghostty shaders, OSC 4 palette, Claude Code hooks, Codex hooks, Copilot CLI hooks, iTerm2 escape codes.

Feedback and security

• Ideas, bugs, a terminal to support: open an issue.
• Security: see SECURITY.md to report a vulnerability privately.
• Contributing: pull requests are welcome, see CONTRIBUTING.md.

See also

Marey, the flight recorder for your Claude Code and Codex sessions: replay every turn, see where the tokens went, and spot the sessions that went sideways.

License

Blink is free and open source under the MIT License.