dsh-caps-beacon

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Use the Caps Lock LED on your MacBook as a status light for DeepSeek Harness — a DSH-native take on Mac-Agent-Beacon.

Solid = working · Fast blinking = needs your attention · Off = idle

When you send DSH off to work in the background, you can stop switching back to check on it: a glance at the keyboard tells you everything.

What the LED means

Host state	LED
A root agent is running (tools, model calls, retries)	solid
An approval request is waiting for you	blinking
An ask_user_question prompt or plan review is waiting for your answer	blinking
A root turn ended in error or blocked (latched until the next turn starts)	blinking
Idle	off

Attention always wins over working: the moment an approval is resolved, the light returns to solid. Subagents and background children stay silent by default (rootsOnly) so parallel fan-outs don't strobe your keyboard.

The plugin is a pure observer: the approval/request and tools/execute listeners delegate through next() and never decide anything. It writes the LED only — no key presses, no keyboard remapping, no approval-policy changes. On exit, the helper restores the physical light to the current logical Caps Lock state.

How it works

DSH host events ──▶ plugin state machine ──▶ beacon-led (C) ──▶ Caps Lock LED

• The plugin listens to DSH's public host events — agent/status, approval/request, tools/execute, and session/event. No internal interfaces are reverse-engineered, so nothing silently breaks when the agent stack updates.
• A small C helper (native/led.c, adapted from CapsPulse via Mac-Agent-Beacon, both MIT) drives the built-in keyboard's Caps Lock LED through macOS IOKit/IOHID output elements. The plugin keeps one beacon-led serve child alive and writes 1/0 bytes to its stdin; blinking is a timer in the plugin.
• The helper never injects key presses. If the logical Caps Lock state changes under a write, it stops immediately.
• The helper can still die for environmental reasons — a system sleep resetting the HID device, a stray signal reaching its process group. The plugin restarts it automatically (exponential backoff, 1s to 30s) and re-applies the current mode, so the beacon self-heals instead of going dark until the next dsh restart.

Requirements

• A MacBook with a built-in Apple keyboard (external and Magic Keyboards are not supported).
• macOS with Xcode Command Line Tools (xcode-select --install) for the one make step.
• DeepSeek Harness (dsh) with a profile — tested with web.

Install

# 1. Add the plugin to your profile (any profile works, `web` shown here).
dsh plugin --profile web add github:xinyang920/dsh-caps-beacon

# 2. Build the LED helper where pnpm placed the package.
cd ~/.dsh/profiles/web/node_modules/dsh-caps-beacon && make

# 3. Restart dsh web — bundle membership is read at startup.

Step 1 registers the bundle in dsh.profile.bundles automatically. Step 2 compiles build/beacon-led (about one second; the installer deliberately does not run compiled code for you). Step 3 is required because plugins load at boot.

Grant LED access if asked

On most machines the helper can write the LED with no extra authorization. If yours blocks it:

1. Run ./build/beacon-led inspect — it explains the failure when access is denied.
2. Open System Settings → Privacy & Security → Input Monitoring, click +, press Cmd-Shift-G, and enter the absolute path of dsh-caps-beacon/build/beacon-led inside your profile's node_modules.
3. Restart dsh web.

Verify

# The helper finds the keyboard and LED element:
./build/beacon-led inspect
# {"keyboard":"Apple Internal Keyboard / Trackpad","led_output":true,...}

# The helper process is alive while dsh runs:
pgrep -fl beacon-led

Then give any task to a session: the LED goes solid while it runs. The easiest blink test is to ask the agent a question that makes it call ask_user_question — the LED blinks while the prompt waits for you.

Helper failures and unexpected exits are logged under the [dsh-caps-beacon] prefix in the dsh log.

Configuration

Override the row by id dsh-caps-beacon in your profile's cordis.patch.yml (a patch replaces the row's whole config, so restate what you own):

- id: dsh-caps-beacon
  config:
    enabled: true
    ledPath: ""            # absolute path to beacon-led; default: bundled build/beacon-led
    blinkIntervalMs: 250
    rootsOnly: true        # ignore subagents and background children
    verbose: false         # log every mode change
    triggers:
      approval: true       # approval/request pending
      question: true       # ask_user_question / exit_plan_mode pending
      error: true          # turn ended in error/blocked

Troubleshooting

• LED never lights — check pgrep -fl beacon-led while dsh runs. No process means the plugin did not load: confirm dsh-caps-beacon appears in dsh.profile.bundles (~/.dsh/profiles/web/package.json) and restart. A process with a dark LED usually means an external keyboard or Karabiner is involved: Karabiner-Elements can block LED access when it grabs the built-in keyboard exclusively.
• LED went dark mid-session — the helper died (system sleep and terminal Ctrl+C are the usual causes). Since v0.1.1 the plugin revives it automatically within seconds; the revival is visible in the dsh log as [dsh-caps-beacon] helper restarted after failure. If the LED stays dark past a minute, restart dsh web.
• make fails — install Xcode Command Line Tools (xcode-select --install) and retry.
• Upgraded the plugin — rerun step 2 of the install (make in the package directory) so the helper binary matches, then restart.

Uninstall

dsh plugin --profile web remove dsh-caps-beacon

Also remove dsh-caps-beacon from dsh.profile.bundles in ~/.dsh/profiles/web/package.json if your dsh version did not, then restart.

Credits

• Mac-Agent-Beacon (MIT) — the original Codex status light and the direct source of the LED helper's stdin protocol and safety checks. This project replaces its hardest part (reverse-engineering the Codex Desktop IPC stream) with DSH's public host events.
• CapsPulse (MIT) — the original IOKit/IOHID Caps Lock LED technique.

See THIRD_PARTY_NOTICES.md.

License

MIT