kbd-signal

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Turn a VIA-compatible RGB keyboard's backlight into a status lamp for AI coding agents on Windows (defaults target the Keychron K8 Pro). When Claude Code or Codex waits for your approval, your keyboard starts breathing orange — no need to watch the screen.

Works on stock firmware (no flashing) by speaking the VIA raw HID protocol directly.

Signals

Before signaling, the current lighting (effect / speed / brightness / color) is snapshotted and restored afterwards. Nothing is ever written to EEPROM (RAM-only changes), so a power cycle always returns the keyboard to your saved settings.

Requirements & limitations

• Windows or macOS, Python 3.11+ (hidapi is the only dependency; its macOS wheel is self-contained via IOKit, so no Homebrew hidapi is needed)
• Keychron K8 Pro connected via USB cable with the rear switch set to "Cable". Raw HID is not available over Bluetooth — measured: in BT mode with the cable attached, the USB HID collections enumerate but the 0xFF60 raw interface does not
• When the keyboard is absent (BT mode, unplugged), the hook-facing commands (hook, set, restore) silently no-op with exit 0 — hooks are never blocked. Diagnostic commands (detect, test, raw-effect) report the missing device and exit 1
• Do not run the VIA app / Keychron Launcher at the same time (concurrent raw HID writes race)
• Codex requires a version with lifecycle hooks; run codex features list and confirm that hooks is enabled
• Concurrent Claude Code / Codex sessions and subagents are tracked independently; orange remains active while any approval is pending

Install

Recommended: pipx — installs into an isolated environment and puts kbd-signal on PATH, which is exactly what the hook commands need:

pipx install kbd-signal

Windows — if you don't have pipx yet (one-time setup):

py -m pip install --user pipx
py -m pipx ensurepath   # then open a new terminal

Plain pip also works (py -m pip install .); in that case invoke the hooks with the same interpreter you installed into: py -m kbd_signal hook claude.

macOS — install pipx with Homebrew if you don't have it (brew install pipx && pipx ensurepath), then pipx install kbd-signal. The hidapi wheel is self-contained (IOKit backend), so no brew install hidapi is required. Config, state, and log live in ~/Library/Application Support/kbd-signal/.

Usage

kbd-signal detect                # find the keyboard, show protocol & current lighting
kbd-signal set <waiting|done|error>
kbd-signal restore [--after N] [--gen G]
kbd-signal test                  # play all patterns, then restore
kbd-signal raw-effect <n>        # set a raw effect index (debug)
kbd-signal hook claude           # entry point for Claude Code hooks (JSON on stdin)
kbd-signal hook codex [<json>]   # Codex hooks (stdin) / legacy notify (argv)

Restore mode (config.json in the state dir)

The state dir is %LOCALAPPDATA%\kbd-signal on Windows and ~/Library/Application Support/kbd-signal on macOS.

{"restore": "off"}

• "baseline" (default): restore the pre-signal effect and brightness
• "off": restore to brightness 0 (for people who normally keep the backlight dark). The stored effect/color/speed are still written back, so waking the backlight with Fn shows your own settings

The Fn backlight on/off flag is not readable over VIA, which is why "off" exists.

Claude Code integration

Register the same command for PermissionRequest, PostToolUse, Stop, and SessionEnd in your user-scope settings.json (events are dispatched internally by hook_event_name):

{"type": "command", "command": "kbd-signal hook claude", "timeout": 5}

(pipx install — the kbd-signal shim is on PATH. With a plain pip install, use py -m kbd_signal hook claude instead, matching the interpreter you installed into.)

Do not put a filesystem path in the program position. Hook commands may run through either cmd or a POSIX shell: backslashed paths get eaten as escapes by the POSIX shell, and forward-slashed program paths fail under cmd with "Access is denied" — both silently, so the hook simply never signals (measured on Windows 11). PATH-resolved names (kbd-signal, py -m kbd_signal) work under both. The entry point is cheap when idle (the hidapi DLL is imported lazily), so the same command is fine for hot hooks like PostToolUse.

That cmd-vs-POSIX hazard is Windows-only. On macOS/Linux an absolute path in the program position is safe, so if kbd-signal is not on the PATH your hooks run under, use its absolute path — pipx installs the shim at ~/.local/bin/kbd-signal.

Codex integration (since v0.3.0)

Use Codex lifecycle hooks. They are separate from the notify entry in ~/.codex/config.toml, so leave the existing notify command unchanged.

1. Run codex features list and confirm that hooks is enabled
2. Merge the events from examples/codex-hooks.json into the user-level ~/.codex/hooks.json; do not overwrite an existing file
3. Start the Codex CLI and choose Review hooks from the startup Hooks need review prompt, or open /hooks. Verify the source, event, and command before trusting them. Trust is tied to the hook definition hash, so review it again after any change
4. In a new session, trigger an approval and verify orange while waiting and restoration after approval

Every event uses the same command:

{
  "type": "command",
  "command": "kbd-signal hook codex",
  "timeout": 5
}

The configuration uses:

• PermissionRequest to add a pending approval
• PostToolUse to release only the agent that completed its tool
• Stop to release the main session and signal completion only when no other session is waiting
• SubagentStop to clean up a child without flashing green for the whole task
• SessionStart / UserPromptSubmit to clean up stale entries for the same session after an interrupted run

Codex does not expose SessionEnd. If Codex is force-closed while an approval is pending and that session is never resumed, orange can remain active; run kbd-signal restore to recover.

The old agent-turn-complete notify payload remains supported for compatibility, but it cannot report approval waits and competes with the desktop app's notifier, so it is not recommended for new installations.

Concurrent sessions

Owners are keyed by product, session_id, and agent_id. A main-session completion therefore cannot clear another Claude/Codex session or one of its subagents. Updates to state.json remain serialized by the existing interprocess lock.

To roll back, remove only the entries whose command invokes kbd_signal hook codex from ~/.codex/hooks.json, then restart Codex. The desktop app's notify configuration remains untouched.

Protocol notes (verified on hardware)

• Shipped K8 Pro stock firmware speaks VIA protocol 9 (v2) — not the v3 custom-channel layout found on the wireless_playground branch. The protocol is probed at open time (command 0x01) and both layouts are supported:
  • v2: [report_id 0x00, cmd, value_id, data...], value ids 0x80 brightness / 0x81 effect / 0x82 speed / 0x83 color (hue, sat)
  • v3 (protocol ≥ 11): [report_id 0x00, cmd, channel=3, value_id, data...], value ids 1–4
• Commands: set 0x07, get 0x08, save 0x09 (save is never used)
• Effect indices are identical across firmware generations (info.json animation list matches): None=0, Solid Color=1, Breathing=2, … Solid Splash=22
• Device detection: VID 0x3434 + usage page 0xFF60 / usage 0x61 (PIDs differ per layout variant)

Other keyboards (since v0.2.0)

The protocol layer is not K8 Pro specific: VIA v2 value ids are fixed by the VIA spec and Solid Color is always effect 1 in QMK. Point kbd-signal at another VIA-compatible RGB keyboard via config.json:

{
  "restore": "off",
  "device": {
    "vendor_id": "0x3434",
    "product_id": null,
    "product_match": "K8",
    "v3_channel": 3,
    "effects": {"solid": 1, "breathing": 2}
  }
}

Workflow for a new board:

1. kbd-signal detect --all — list every raw-HID (0xFF60) device and copy its VID/PID into config.json
2. kbd-signal raw-effect <n> — step through effect indices until you find solid/breathing, then set effects
3. On a VIA v3 board, set v3_channel to the keyboard's id_qmk_rgb_matrix channel from its VIA definition (v2 boards ignore it)
4. kbd-signal test

Boards without RGB (single-color backlight) are out of scope — states are color-coded.

License

MIT