Claude Approver 🛎️

The Problem

I run a lot of long Claude Code tasks in the background. Builds, refactors, tests — anything that takes more than a minute. The annoying part is the polling: am I done yet? Did it finish? Did it get stuck?

I needed a physical, in-the-room signal. Something I'd notice without staring at a terminal.

The Build

A tiny ESP32 XIAO S3 board running custom firmware, paired to my Mac over Bluetooth Low Energy. When Claude finishes a task — or wants approval for something risky — the device:

• 🎵 Plays a jingle (different jingle per event — done, approved, error)
• 💡 Lights up with status colors
• 🔘 Has buttons I can press to approve / reject without reaching for the keyboard

The Architecture

It's a small stack but it has more layers than you'd expect.

• ESP32 firmware — Arduino + NimBLE, presents as a BLE HID keyboard plus an HTTP control endpoint over WiFi.
• Mac menu-bar app — bridges between Claude and the device. Holds the BLE/HTTP connection.
• MCP server — exposes the device to Claude as tools (play_jingle, set_led_status, device_status).
• HTTP transport — the path that ended up working reliably after BLE HID output reports turned out to be blocked on macOS.

What I Learned

macOS does not let userspace apps write HID output reports to a bonded BLE keyboard — IOKit blocks it for security. I burned an evening proving that, then pivoted the control channel to HTTP over WiFi, which works perfectly. That whole detour ended up being its own little research project.

Tech