The v0.4.51 stack dump named the OCR pod freeze. chat_completions called
multi_model_manager.get_model_for_request() on the loop. For a model not
loaded yet that goes _load_default_model -> load_model ->
vllm_worker.ensure_service(), which waits for vLLM in a time.sleep(2) loop.
On a pod it froze the whole process for 324 s at boot, /healthz included,
and for minutes whenever it decided to (re)start vLLM, so the orchestrator
took busy pods for dead ones.

chat_completions and completions now resolve the model in a thread. The
manager's load lock already prevents duplicate loads. The no-blocking-calls
AST guard now also forbids get_model_for_request, _load_default_model and
ensure_service in a coroutine; it fails on the old code and passes on the new.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KnfkxBpcZ1v6ypRFFyhrVM