BFM-decomp/cookbook/C0112.md

§101 — The STALE DEFAULT class: a guard whose cause was removed is a silent skip wearing a safety label (Phase 29 SESSION-22, three instances in one session)

Three separate tools were suppressing real, already-correct work — not by being wrong, but by defaulting to a protection whose cause had since been fixed, opt-out only if you remember a flag:

tool	the guard	cause, and when it died	measured cost
family_sweep	skip any pinned exemplar (§42e cc1 SIGABRT)	the SIGABRT was extract_unit dropping file-scope macros — our bug, fixed in Phase 27 (_carry_macros)	137 skipped, 133 of them bank
family_sweep	gate serially; the parallel farm is opt-in via --stage-only → sweep_parallel	sweep_parallel.py was built in SESSION-20 after measuring the loss, and never wired to the caller	~8-16× throughput; 3 sweeps (543 members) ran serially this session
conform_decls	REFUSE when 0-arg call sites exist	correct — but it printed the exact remedy and could not perform it	func_801789AC blocked two sessions; unblocked by --cast-zero-arg-calls

The shape, every time: correct when written · the cause was later removed or the remedy became available · the default never changed · and the tool reports the skip as a clean, quiet number (skipped {'pinned-exemplar': 137}) that reads exactly like "nothing to do."

The law (R32/R35, pointed at defaults): a guard is a claim about the world. When the thing it guards against is fixed, the guard becomes a silent skip — and a skip is invisible in exactly the way R32 warns about, because nobody counts what a protection declined to attempt. When you fix a wall, grep for the guard that was erected against it and retire it in the same change. Phase 27's roadmap delta did say the PINS class was "back on the mechanical-harvest table" — the knowledge was recorded and the default still wasn't flipped, which is why this needs to be a mechanical habit and not a note.

Corollary — how to spot one: any run reporting a large skipped {...} bucket deserves the same suspicion as a 0/N (§59, §94). Both are the tool declining to try, and neither is evidence about the compiler.