Mutation gate: why one probe was not enough

The gate proved an assertion bites. It could not prove the file fails. Toggle a test file's shape below and watch the two probes disagree.

Build a security test file

assertion reaches a live hook
Off = the hook path was deleted in the TS migration, so the verdict is ERROR. || true after the assertion
Swallows the failure. One of the three root causes of the original 47 no-op functions. ends in [[ $FAIL -eq 0 ]]
Off = trailing exit 0. The file reports success whatever it observed.

What the gate sees

Probe A — early exit

ORK_MUTATE_INDEX flips the verdict; expect_decision exits 0 / 87 from inside itself. Fast, sed-free. Never returns to the file.

Probe B — no-exit

ORK_MUTATE_NOEXIT adopts the inverted expectation and lets the file finish, so the file's own gate decides the exit code.

Verdict matrix

file shape	probe A	probe B	gate verdict
live hook + real gate	DETECTED	file exits 1	CAN FAIL
live hook + \|\| true	DETECTED	file exits 0	SWALLOWED ← the hole
live hook + exit 0	DETECTED	file exits 0	SWALLOWED
dead hook path	ERROR	—	HOOK ERROR

ERROR is never a pass. A hook that cannot be reached differs from both the original and the inverted expectation, so a naive comparison would score the flip as “detected” for a file whose hook was deleted — the exact blindness the gate exists to end.