Row 7 left three mutants standing after v1.1 (11 of 14, bar 13): the passage
signal reading no body, the field signal weighing no title and no path, and a
flattened fusion (bm25.RRF_K = 10 000). Each switches off a mechanism the
default ranking runs, and each moved 0 ranks, because every synthetic concept
was short and opened with its own title -- none of the three ever decided a
delivery here.
Three bundles, one per mechanism, and one pinned set (set-mechanisms.json):
- PASSAGE: a long concept answered in one window of its body, against ten
short concepts whose titles carry the question's words. Rank 1; with no
body windows it falls out of k (class b).
- PATH: a concept named by its path alone, against ten decoys denser in the
body. Rank 4 at k = 6; with no title/path weight it falls out of k.
- FUSION: gold 1st in the passage signal and 21st in the field signal, one
decoy 10th and 11th (rank sum 19 < 20). At RRF_K = 60 the gold leads, and
it keeps the lead through K = 180 (measured in steps of 10); flattened, the
decoy wins k = 1.
Chose separate fixtures over one combined one because each fixture's comment
can then name the single mechanism it pins. Verified per question against all
14 mutants: no previously felled mutant is lost. src/ is untouched, MUTANT_BAR
and the roster are unchanged, the corpus pin moved with the corpus.
Gate: rows 1 and 6 go 10/10 -> 13/13, row 7 11/14 -> 14/14 GREEN, rows 2/3/4
unchanged, GATE RED: rows 5, 8. Suite: 2444 passed, 1 skipped (+3), measured
with FORCE_COLOR unset -- with FORCE_COLOR=3 in the environment Python 3.14
colours argparse help and test_each_arm_flag_carries_its_attribution fails,
independently of this change.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
