The logical LLM scope close in ``relay_llm._complete_logical`` popped its handle with
the unguarded ``pop_relay_scope``. Two consecutive calls in one session share a physical
scope stack, so when the sibling turn's live scope sat above the handle the native
binding raised::
RuntimeError: invalid argument: scope handle is not at the top of the stack
``_complete_logical`` catches that, logs "logical LLM finalization failed" with a
traceback and returns early, so the early-return path also skips the
``turn.logical_llm_calls`` cleanup until the handle is retried. Observed in production as
one traceback per overlapping turn (~14/day on a busy local profile).
``pop_relay_scope_if_top`` already exists for exactly this case and is used by the
shared-metrics task close (PR #116685, #115471); the logical-LLM seam was missed. Guarding
``pop_relay_scope`` itself is NOT an option — ``_pop_with_drain`` relies on that raise to
detect a stacked sibling and drain it.
The skipped scope is reclaimed by the existing session-close drain
(``RelayRuntime._close_scope_handle``), so the handle still leaves
``logical_llm_calls`` and the session unwinds without an orphan.
Test: ``test_logical_close_skips_pop_under_concurrent_turn_scope`` pushes a sibling scope
in the session context, completes the logical call, and asserts the sibling (not ours) is
still on top and that the sibling's scope survives. It fails on upstream ``main`` with the
exact ``RuntimeError`` above and passes with the guard.
Fixes#115471 (the remaining call site).
857e651b5f