Both rows were unmutatable for the same stated reason. They resolved
differently, and the difference is the point.
AM-2 is instrumented and enforced — tools/size-metrics.py, in `make all`:
AM-2: 27.2 LOC/rule [ok target <= 40] (1.47x headroom)
1,575 impl lines / 58 rules
Tests are excluded because AM-2 asks what a rule costs, not how much it is
exercised; lib.rs is ~18% test code and including it would have flattered
the number. This matters because AM-2 is AM-1's anti-gaming pair: 100%
rule coverage means nothing if the rules are trivially small, and AM-1 has
been reported met since CB-WP-0001 with its pair uninstrumented.
Verified red by a property mutation — ~800 lines of filler injected into
the impl, pushing the ratio past 40 — not a threshold tweak. The expect
string is the precise failure signature "FAIL target <= 40"; my first
attempt used "AM-2", which also matches passing output and would have
made the FA guard vacuous.
AM-3 is BLOCKED, not uninstrumented, and that is a finding rather than a
deferral. It measures LOC to express the CB-RES-0001 synthetic game on our
kernel, against a boardgame.io baseline of ~36 LOC for a declarative 3p
commit/reveal game object. That artifact has never been built: games/
contains only ground, and benches/synthetic.rs drives GROUND rather than
defining a synthetic game. Measuring GROUND's 1,575 impl lines against a
36-line synthetic game object would compare two different games and call
the difference a D1 result.
So the tool ships the measurement — a marker-delimited region, self-tested
— and reports the row blocked, naming the missing artifact. A number would
have been worse than a blank. It stays unmutatable and still counts
against M-D1-MUT per ADR-0005 §1: a row that cannot fail asserts nothing,
however good the reason.
M-D1-MUT: 5 -> 6 of 14.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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