A key id retired from ENCRYPTION_KEYS, or a corrupt row, made decrypt throw
inside the provider builders, and a briefing generation answered 500. An
unreadable key now drops its entry from the chain like a missing one, with a
warning on the event, so the generation answers the no-provider 422
(ai.provider.none). The connection test reads it as no stored key. The
parity walk holds that case to the contract again.