chat_turn_limit_reached
The posted conversation exceeds the draft's guardrails.max_turns (or the platform default). Start a new conversation; the server keeps no transcript to trim.
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/chat_turn_limit_reached",
"title": "…",
"status": 409,
"detail": "…",
"instance": "/v1/…"
}