call_question_conflict
POST /v1/calls refused: a per-call question reuses an id the pinned version's objectives already carry. Per-call questions are additive-only - overriding a gate-proven objective per call would bypass the publish gate - so there is no precedence rule, only this refusal. errors[] names each colliding questions[i].id.
Problem shape
Every non-2xx response is an RFC 9457 application/problem+json body. The type URI below is stable and machine-matchable, so branch on the final path segment (the code) and treat the status as redundant confirmation. See the error-handling guide.
{
"type": "https://docs.vocapable.com/errors/call_question_conflict",
"title": "…",
"status": 409,
"detail": "…",
"instance": "/v1/…"
}