PROVEN: from 14:57:01 to 18:43:23 today HEAD built main to 307aa45d… against the
expected 143dbb89…, with NO draft substituted (measured under gate.main.lock, no
gate_main alive). Auto-commit commit:2693 had adopted a mid-flight gate_main
substitution — its carve-out reverted main's TUs, gate_main re-wrote them, and
`git add -A src/` swept the unverified bodies in (a TOCTOU race, 14 s after a
bisect chunk banked). Every main batch after it was doomed before its first
draft was judged: m00–m03 card cycles drafted ~737, slated 160, banked 0, and
burned ~50 clean rebuilds bisecting innocent slates. commit:2712 restored the
green content by accident (it swept this investigation's diagnostic checkout).
gate_main: on any batch failure, ONE try_batch([]) control runs first — if HEAD
itself is red it prints BASELINE RED, leaves the slate reusable, exits 3 (R40).
clean_build no longer reports a linked-but-mismatched build as "no binary" (the
build target embeds the SHA check), the compile-conflict shortcut fires only on
error-shaped lines naming a symbol some draft in the slate actually uses (the
baseline's own func_800143AC implicit-decl WARNING was matching — every m04
chunk died with "drafts declaring it: []"), reverts narrow to top-level src/*.c
(main_tus) so a main gate can never destroy overlay lanes' in-flight work, and
--assert-baseline is a first-class mode.
main_lane: every cycle opens with gate_main --assert-baseline and REFUSES to
draft or gate against a red baseline (R43) — BaselineRed parks nothing, burns
no tries, writes .run/main_lane.BASELINE_RED, re-checks every 30 min.
Adopters (ox_campaign ×3, maintenance.sh, gate_stage, gate_lane, idiom_serial):
main's TUs (top-level src/*.c) are never staged and never reverted by an
overlay/maintenance lane — one writer (gate_main), one committer (main_lane,
after the whole-EXE SHA re-checks green). Unstage-after-add is race-free where
the old revert-then-add was the losing half of the TOCTOU.
Diagnosis, evidence and the full timeline: docs/tool-designs/main-lane-fix-s59.md
Drew T
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