echo-cue 🔔

A short Web-Audio "ding-dong" when OpenClaw Control UI finishes a reply. Locally nicknamed echo.

A zero-build local patch for the OpenClaw Control UI (webchat) that plays a short two-tone chime (A5 → E5, ~900ms) when an assistant reply finishes streaming.

Think of it as the missing "reply ready" sound for OpenClaw's web UI — especially useful when you keep the Control UI in a background tab while you work elsewhere.

This is a stop-gap mirror of upstream PR openclaw/openclaw#73894 (issue #69186) which implements the same feature but has not been merged yet. echo-cue works today and gracefully steps aside the moment upstream ships.

Install

Via ClawHub (recommended)

clawhub install echo-cue
bash $(clawhub list --json | jq -r '.[]|select(.slug=="echo-cue").path')/apply.sh

Manual

git clone https://github.com/SymbolStar/echo-cue.git
cd echo-cue
bash apply.sh

Then refresh your Control UI browser tab. Click or press a key once on the page to unlock the AudioContext (browser policy — happens automatically the first time you send a message).

Verify

DevTools console:

window.__milly_cue_v1__   // → true

Toggle (per browser, no UI)

// Disable entirely
localStorage.setItem('milly.completionCue', 'off')

// Re-enable
localStorage.removeItem('milly.completionCue')

// Limit ringing to hidden / unfocused tabs only (default in 0.2.0+: rings always)
localStorage.setItem('milly.completionCue.onlyHidden', 'on')

// Restore default (always rings)
localStorage.removeItem('milly.completionCue.onlyHidden')

Uninstall

bash remove.sh

Restores the original bundle and index.html from the .milly.bak files.

After openclaw update

The update overwrites dist/control-ui/..., dropping the patch. Re-run:

bash apply.sh

apply.sh is idempotent and upstream-aware:

• Already patched → skip
• Upstream responseCompletionSound shipped → skip + advise uninstall

How it works

• Detects every OpenClaw install on the box (Homebrew, nvm, OPENCLAW_HOME)
• Backs up the current Control UI bundle (index-*.js → .milly.bak)
• Appends a small IIFE that:
  • Watches the chat container with a MutationObserver
  • Listens for added .chat-group.assistant nodes
  • Skips NO_REPLY / empty silent completions
  • Plays a Web Audio two-tone chime (A5 → E5)
  • 4-second hard rate-limit + content-fingerprint dedup → no double-rings
• Renames the bundle to index-*.milly-NNN.js and updates index.html so a plain Cmd+R refresh actually picks up the patch (Vite's hashed bundles ship with Cache-Control: immutable, otherwise hard-refresh would still hit cache)

Known limits

• Anchor: .chat-group.assistant DOM class. If OpenClaw renames it the patch silently does nothing (fail-quiet — no breakage).
• AudioContext requires one user gesture per page load (browser policy).
• Webchat only. TUI / iOS / macOS / Android clients are not covered (they have their own native notification stacks).
• Single audible cue per assistant turn regardless of message length.

File layout

File	Purpose
SKILL.md	ClawHub skill manifest (frontmatter name + description)
apply.sh	Detect every OpenClaw install, idempotent inject IIFE, backup, cache-bust
remove.sh	Restore from .milly.bak files
inject/completion-cue.iife.js	The patch payload
tests/manual.md	7-step verify checklist

Related

• ClawHub: https://clawhub.com/skills/echo-cue
• Upstream issue: openclaw/openclaw#69186
• Upstream PR (stop-gap target): openclaw/openclaw#73894
• Sibling skill (same patch pattern): agent-tab-title

License

MIT — see LICENSE.