gate_main is the only trustworthy EXE verifier and is strictly serial: one
flock, one tree, a full clean rebuild per bisect step. The serialization is
an artifact of the SHARED TREE, not of the verification, so this runs the
REAL gate_main inside N git worktrees and hands the union of what they prove
to ONE authoritative gate_main in the real tree. Workers discover; only the
final serial pass banks. Two chunks that each pass alone can still fail
together, which is exactly why that pass exists (G3 — the arbiter never moved).
The non-obvious hazard is asm/: parallel_gate symlinks all 442 MB because an
overlay gate only reads it, but main's verification RUNS make extract, which
writes it. main owns 6.2 MB of that, so this copies main's subtree per worker
and symlinks the other 214 binaries read-only.
Two defects the negative control caught, both mine:
* .run/obj40 (11 MB of SDK objects) was never provisioned. The Makefile says
a tree without them 'builds byte-identically via the stubs'; that is no
longer true for main, whose decompiled src/800_c.c CALLS CdReadyCallback —
the link failed outright with an empty build/psyq/.
* make_worktree reads parallel_gate's module-level WT_ROOT, so the first run
put its worktree in .run/pgate/wt0 — the slots parallel_gate force-removes.
Measured: one gate cycle is 16s in both trees, so MAX_STEPS=24 is ~6.4 min
serial and ~90s across four workers. The docstring's original '1-2 min per
step' was my assertion, not a measurement, and is corrected in the file.
Drew T