The question was whether M-D1-MUT is a real instrument or a name-counter
with extra steps, given that writing a weak mutation is as easy as writing
a strong one.
It is real, but only because it was hardened three times in one pass. Five
controls now stand between a mutation and a red verdict — the mutation
must apply, the baseline must be green, the tree must be restored and
verified, the failure must match a stated reason, and that stated reason
must be absent from passing output — and every one of them exists because
its failure actually occurred. The last is the sharpest: the FA guard
needed a guard, because my first AM-2 expect was "AM-2", which the passing
report contains.
Generalizable: an instrument that measures whether other instruments work
needs more controls than the instruments it measures. M-D1-MUT carries
five; dep-weight and rule-coverage carry one each. That asymmetry is the
cost of a meta-instrument, and a project adding one should budget for it.
A worse failure mode than CB-WP-0005 predicted: a mutation can become weak
without anyone touching it. AM-6's went SURVIVED when T04 moved its gate
from debug to release — nothing about the row, the mutation or the code
changed, only the headroom. Mutation strength is coupled to measurement
conditions, so a mutation is not a write-once artifact. CB-WP-0005 T08's
stronger remedy — mutations written by someone other than the author — was
NOT tested and should not be assumed unnecessary: EXPECT-VACUOUS covers
the cheap failure, not the expensive one AM-6 demonstrated.
The "removes the manual path" test is settled as a predictor of cost, not
of worth. mutation-check fails it outright and produced six defects
nothing else would have found.
Prediction error collapsed: 4-5x, then 2.5x, now small — because this pass
predicted per task, as a mechanism, with the alternative named. Both
branches are outcomes someone must defend, so the prediction cannot be
dodged. AM-3 and AM-4c took the second branch and are better resolved for
it than if a number had been forced.
No InnerLoop change. v1.4's mutation requirement is one pass old and
changing it before a second use would be the invention-in-isolation INTENT
warns about — the same argument used to amend K14 four hours earlier.
Named next candidate: specs/SessionShape.md. SS-01..SS-05 have been stated
since CB-WP-0003 and none has ever been enforced. This pass ran at 2.5x
the context ceiling its own spec sets and nothing said a word.
CB-WP-0006 status -> done, 9/9.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
tegwick
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