/xce-audit-invariants scheduler (dimension 1, driver state-equivalence,
re-run after scheduler-sim-live-allocation) found plugin_end_session()
still checked `plugin->begin_session_fn != NULL` before invoking
`plugin->end_session_fn(plugin)` -- a copy-paste of
plugin_begin_session()'s own (correct) guard. Two failure modes: a
plugin registering only end_session_fn silently never has it invoked;
a plugin registering only begin_session_fn crashes via a NULL
function-pointer call. Currently inert in production (no live plugin
hits either shape) but a real latent defect in exactly the
session-boundary code the driver-equivalence invariant governs.
This exact defect had been independently filed twice: bug-1492
(2026-08-04, scheduler-core task 5.2's review) and bug-1682
(2026-08-24, found adjacent to bug-1681's fix) -- neither investigation
cross-referenced the other. Both entries also carried a "fixed" tag
inconsistent with their own "not yet fixed" narrative text, caught by
this audit's independent code+text cross-check.
Fixed the one-line guard; added test_end_session_invokes_end_session_fn_
when_only_it_is_set() (test_plugin_hook_dispatch.c) proving the silent
non-invocation, confirmed RED (84/85) against the buggy guard and GREEN
(85/85) after the fix. Updated both buglog entries to FIXED with
cross-references, and corrected bug-1611's stale narrative to reflect
its narrowing (not elimination) by scheduler-sim-live-allocation.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLSNJhNoULvVcUhXEFafQC
Rongsong Shen
a643966f50