CWE-807: the kill switch was keyed only by the caller-declared X-Device-SerialNumber, so omitting or forging the header dodged block and kill. A block now mirrors onto the device's certificate identities (Sessions.OwnerDeviceId) as id:{guid} alias rows in BlockedDevices, resolved at block time; KillSwitchEvaluator checks serial, then identity, then version and stamps the DeviceIdentityBinding request dimension. Alias rows are hidden from listings and exempt from the legacy-key migration; unblock removes them. Session-scoped watchdog blocks were unreachable (no session id ever reached the evaluator): ingest now carries the verdict past the body parse and re-evaluates with the session id, and holds the registered serial against the block list when the header differs.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>