Phase 0 of scheduler-hardening-plan.md: a cross-file structural regression
test locking the invariant whose three observed violations were bug-1799
(charge without reset-skip), bug-1801 (the complement) and bug-1814
(rusage delta without the skip): every w->resInUse/core->sharedInUse-
mutating path shares ONE identical skip condition for UNAVAIL/RECONCILING
workers.
test_res_account_symmetry.c drives all three paths in one core per round
-- core_reset_workers() (core_session.c, bug-1751 skip),
sched_charge_account()/sched_update_account() (resource.c, bug-1801 skip)
and sched_reconcile_host_resource_usage() (resource.c, bug-1814 skip) --
using the real sched_account_jobs() from scheduler.c, and asserts the
accounts do not drift across consecutive rounds. A per-path test cannot
see asymmetry by construction; bug-1799's live shape was asymmetry
compounding across rounds (resInUse grew one full charge per round for
two weeks).
Three cases: two-round zero drift with a RECONCILING worker (B frozen at
its seeded value, both host entries named by the job's account so the
skips are active decisions, not vacuous); UNAVAIL worker plus a real
usage climb 2.0->5.0->0.0 proving the reconcile delta still applies on
the healthy host while the excluded host's account-entry used baseline
never advances (bug-1814's half-damage); and a status-clear round
proving the freeze is per-round status-gated, never permanent.
Link technique: the separate-compiled-sources shape of
sched_trace_error_paths_test -- the test white-box #includes
core.c/core_session.c/resource.c/schedobj.c + the four hooked trace
sources, and meson compiles every other scheduler_srcs entry (minus
main.c) as its own TU, which resolves sched_account_jobs() from
scheduler.c's own object without white-box including scheduler.c (and
without the plugin_* stubs test_resource_accounting.c needs: real
plugin.c is one of those TUs).
Red proof: temporarily removing resource.c's bug-1801 skip trips the
zero-drift assertion immediately (2.5 -> 4.5, exactly one extra charge
per round -- bug-1799's live shape); mutation reverted, suite green.
Full scheduler suite: 102/102 OK.
Co-Authored-By: Claude Code <noreply@anthropic.com>
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