Duplicated-fact drift is the fourth error class and the only one with no
executable rule. No positive control catches it (both copies are
internally consistent) and re-derivation does not either (the copy
reproduces whatever it was copied from). It is caught only by reading a
copy against its source, which nothing in the loop required.
facts.toml holds 15 facts and is GENERATED by `make facts-gen` from
cb-cost, dep-weight and rule-coverage. The trap this task named — a
hand-maintained registry that becomes another drifting copy — is closed
by facts-check re-running the instruments and failing when the committed
registry disagrees with them. A stale registry cannot certify stale
artifacts.
An artifact quoting a fact tags it: **$93.15** <!-- fact --> with the key.
17 occurrences across 5 artifacts are now checked.
Falsified before being believed: changing CostAccounting.md line 158 from
$93.15 to $92.87 — the exact historical drift — produced exit 1 naming
the file, the line and the expected value. Tested against the class it
exists to catch, on a real artifact, not only in its self-test.
It then caught a live tag inside its own documentation example in
InnerLoop.md within the hour. Third time a gate has failed on its own
pass's work.
What it does not close is stated rather than implied: 22 untagged literal
copies remain and are reported, not failed. Tagging is opt-in, a number
can legitimately recur, and a gate that fires on coincidence gets routed
around. Naming the uncovered surface beats claiming the class is closed.
InnerLoop single-source-of-fact moves from prose to executable — v1.3.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Discharges the open item T07 raised. Values unchanged at 250,000 and
350,000; what was missing was a reviewed decision behind them, since
they had been set by the implementer in the commit that measured them
and that also changed the feature gating being measured.
The ADR supplies the argument T07's test requires -- why the targets
bind on FUTURE work rather than merely passing present work:
AM-4a leaves 3,750 lines of headroom (1.5%), about one small crate,
so any new shipped-runtime dependency breaches it almost immediately.
That is intended: the shipped runtime should be effectively frozen.
AM-4b leaves 32,979 lines (10.4%), deliberately looser -- dev tooling
should absorb one moderate dependency without a spec change, not two.
Both are ceilings on a quantity that only grows by choice. Nothing
drifts across them; only adding a dependency does.
Falsification condition stated: if a later pass raises AM-4a to
accommodate a dependency it wants, that is the failure the ceiling
exists to catch, and the answer is an ADR arguing for the dependency.
First ADR written under the correction/retarget test; sets the shape.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
