The native Relay pipeline binds its Futures to the event loop that
entered run_in_session_async. While a managed tool callback executes,
that loop is blocked until the callback returns — so a nested managed
relay call made from inside the callback (vision_analyze's auxiliary
LLM call on a worker-thread loop) awaits a Future that can never
complete: 'RuntimeError: Future attached to a different loop', or a
deadlock, plus 'Event loop is closed' at shutdown when the orphaned
future completes late. (#77244)
Fix: managed_callback_guard, a ContextVar depth marker set around every
Hermes callback the relay adapters hand to the native pipeline
(relay_tools.execute invoke, relay_llm execute/execute_async invoke,
ManagedLlmStream run_callback). resolve_execution_context returns the
no-relay triple while the marker is set, so nested calls run unmanaged.
The marker propagates through contextvars.copy_context() into the
worker threads tools use for their internal async work.
Top-level turn LLM calls and tool wraps stay fully managed — verified
live: vision_analyze works under active shared metrics while the main
turn still records managed llm.execute events.
Alternative fixes considered and rejected: removing
retain_managed_execution (kills the shared-metrics managed pipeline)
and gating on main-thread identity (managed tool wraps legitimately
run on the run_agent thread, so that gate disables relay everywhere).
Teknium
961f7481a7