The ledger pipe asks the runtime through stdio.BusState (it answered ErrNoPipe before), an operation names the call the runtime proved (stdio.CallIDOf), and the page takes the runtime's word on its consumer (stdio.OnHeartbeat): a beat is every subscription heard, a missed heartbeat marks each subscribed source at once with the runtime's why. Rows in TestASourceThatDoesNotAnswerIsSaidAndAskedAgainOnABackoff and TestTheLedgerStoreRefusesWhatTheLedgerWouldHaveToTakeBack; each failed before the change. Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig