PATCH participant attributes returns 404 mid-call

Getting 404 when trying to write supervision_flag during a live voice call. The conversation ID looks valid in the debug logs, but the REST Proxy fails.

  • Endpoint: PATCH /api/v2/conversations/voice/{id}/participants
  • Payload: { "attributes": { "supervision_flag": "true" } }
  • Timing: Tried immediately after call connect and 30s later. Both fail.

Is there a delay before attributes are writable? Or am I missing a required header in the config?