The BT-off custom slave (2.12.12) can't survive the C6's OTA rollback protection: it flashes, the C6 boots it, reverts to 2.12.11, host reflashes -> ~30s reboot loop, worse than the wedge. BLE-coex hypothesis is UNTESTABLE via OTA (custom slaves won't stick; needs direct C6 UART flash, out of scope tonight). Reverted to the self-healing 2.12.11 baseline: ~5-13min MTBF, 15s auto-recovery. That is the shippable overnight state. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>