Optionaloptions: ErrorOptionsReadonlyreasonAn optional machine-readable reason, rendered into the response body alongside the message. DECLARED HERE rather than sniffed structurally at the mapper so the channel is part of the contract a subclass opts into, and so the mapper needs no import of any subclass to render it (see the header for why that import must not exist).
ReadonlystatusThe response status, 4xx or 5xx; any other status answers 500.
An authoritative run-state read did not succeed, so nothing that read returned is evidence about the run: 503 with
reason.codeRUN_STATE_UNREADABLE. One cause is Mastra answering from its in-memory fallback instead of from storage — what comes back then describes the Run object this isolate happens to hold rather than what is persisted. Distinct from UnknownRunError: the run may well exist and be suspended — nothing about it could be READ. The message therefore names no cause: it is minted where the read failed, not where the reason is known.Retryable: the caller asked for nothing wrong and the condition clears on its own, so it is not a 500 that reads as a code fault, and a 404 or a summary would invite a conclusion from a read that never happened.