session_token_refused
This code is raised on a non-customer surface (the /internal voice-runtime audience or telephony provider callbacks). It is excluded from the customer OpenAPI document and is registered here so an operator reading a log line has one place to look.
The call-session token is not redeemable. Forged, expired, unknown-key, malformed, and already-spent are one indistinguishable refusal on purpose: a leaked Media Streams URL must not be usable to learn why it failed.
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/session_token_refused",
"title": "…",
"status": 401,
"detail": "…",
"instance": "/v1/…"
}