max_operator_h_ratio was 1.25. Instrumented over the rotation battery, the statistic it bounds reads
0.85-1.57 on GENUINE promotions - and 2.48 on a genuine orthorhombic step in an arm left short of
pairs - while the two real merohedral twins read 1.82 and 4.01. There is a wide empty gap between the
two populations and 1.25 was not in it: it sat inside the genuine range.
Four genuine promotions already exceeded it and survived only because the two-arm rule happened to
offer cover from the other arm; a cubic case with no such cover was refused outright, by a margin of
0.4%, and merged in the orthorhombic subgroup with twice the unique reflections. That refusal is
invisible to the standard battery, which passes an explicit resolution limit: the limit also
constrains the merge the search's internal cutoff is derived from, and lands it just under the
crossing. It appears only when the automatic cutoff runs.
Set the bound to 1.70, in the gap. On the automatic-cutoff arm the cubic case returns to its true
group (unique reflections 49277 -> 23330, CC1/2 in the outermost shell 25.7 -> 50.4) and no other
crystal changes symmetry. The 38-crystal battery at matched limits is unchanged, space group included.
All ten SearchSpaceGroup test cases pass, including the twin decision table and the H-margin case -
worth checking explicitly, because a looser bound also confirms the operator agreement more often and
so suppresses the systematic-absence veto more often.
The header note already predicted this failure mode: the test's known limit is angular coverage, not
data quality, and a refusal on a lopsided merge says more about the coverage than the symmetry.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
7523c67655