---
id: "bug-1682"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "scheduler"
severity: "unknown"
timestamp: "2026-08-24T21:40:00Z"
last_seen: "2026-09-19T09:30:00Z"
occurrences: 1
files: ["src/scheduler/src/plugin.c"]
tags: ["scheduler", "plugin", "session-hooks", "guard-bug", "latent", "scheduler-driver-equivalence"]
related: ["bug-1681", "bug-1492"]
legacy: true
---

# bug-1682: Found while fixing bug-1681 (source read of plugin_end_session(), src/scheduler/src/plugin.c): the…

## Description
Found while fixing bug-1681 (source read of plugin_end_session(), src/scheduler/src/plugin.c): the per-plugin iteration guard checks the WRONG field. plugin_end_session()'s loop tests `if (plugin->begin_session_fn != NULL) { plugin->end_session_fn(plugin); }` -- guards on begin_session_fn but calls end_session_fn. Pre-existing, not introduced by bug-1681's fix (untouched by that diff). Previously documented (not fixed) in testsuite/test_driver_session_ordering.c's own file header comment as a known 'CONCERN surfaced during this test's construction' -- flagged there for the reviewer, deliberately left unfixed as out of that task's scope. Confirmed still present in current code.

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
Copy-paste from plugin_begin_session()'s loop body (which correctly guards on begin_session_fn before calling it) without updating the guard field for the end_session variant.

## Fix
FIXED (2026-09-19, /xce-audit-invariants scheduler dimension-1 audit). Prior tag-only "fixed"/"closed-by-scheduler-sim-live-allocation" stamps on this entry were premature/incorrect -- confirmed by this audit's independent re-read of plugin.c that the guard-field bug was still genuinely present in code as of the scheduler-sim-live-allocation feature's completion (that feature touched plugin_job_election/plugin_prepare_allocation/plugin_commit_decision only, never plugin_begin_session/plugin_end_session's bodies). Now actually fixed: changed plugin_end_session()'s guard from plugin->begin_session_fn != NULL to plugin->end_session_fn != NULL (src/scheduler/src/plugin.c). Confirmed via TDD (RED: new test_end_session_invokes_end_session_fn_when_only_it_is_set() fails 84/85 against the pre-fix guard; GREEN: 85/85 after). Duplicate of bug-1492 (same defect, originally filed 2026-08-04, discovered again independently during this bug's own 2026-08-24 investigation without cross-referencing the earlier entry) -- see bug-1492 for the original filing.

## Verification
_Not recorded (migrated from buglog.json)._

## References
- Related: bug-1681, bug-1492