keychron k2: bluetooth always-on

Problem statement: the Keychron K2 (C3, stock firmware) disconnects from macOS after ~10 minutes idle — and there’s no way to prevent it. I spent some time looking for a fix. The usual suggestions: Disable Bluetooth auto-sleep in macOS? macOS doesn’t do that — the keyboard decides to sleep, not the host. Install a keep-alive app? The keyboard’s firmware powers down its own radio. By the time the app could send a ping, there’s nothing on the other end listening. Key combo to disable sleep on the keyboard? Only on newer Keychron boards (QMK/VIA). The C3 runs stock firmware with no configurable sleep timer. Flash QMK and set an infinite sleep timeout? The C3 isn’t a QMK board. Can’t. The C3 stays paired — macOS reconnects on the first keypress, with ~1s lag. That’s the firmware’s design. The radio sleeps to save battery. Nothing running on the Mac can reach through a sleeping radio and wake the other end. The only real fix: flip the side switch to Cable, plug in USB-C. No Bluetooth, no…