shared_phone_continuation_unavailable
The existing caller's current handoff cannot safely be rendered from its custody record. Reconcile the winning offer and its physical leg; do not join a stale room or invent a replacement call.
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/shared_phone_continuation_unavailable",
"title": "…",
"status": 503,
"detail": "…",
"instance": "/v1/…"
}