The residual applies angle_rad * |rot_vec| and rot_vec is a free three-vector, so the first pass has
been fitting a goniometer rotation SCALE nobody asked for. GoniometerAxis::Axis() then normalises it
away on write-back, and RotationIndexer scores the candidate with the normalised axis - so the cell
that won the fit is judged under a rotation model the fit did not use. Measured over 43 rotation
datasets: the length reaches 1.2%, and the fit-vs-score disagreement a median 0.124 deg and up to
6.19 deg of goniometer angle, against rocking widths of 0.05-0.36 deg. That score picks the lattice
class, which nothing later revisits.
The fitted length is not a usable measurement of anything either: on synthetic data it recovers 54%
of a known scale error, repeated first passes on one dataset disagree with each other in sign, 26 of
43 datasets disagree with themselves, and on the one dataset with a proven 1.3% stage fault it comes
out negative. It is absorbing other systematics. The rotation scale is measured properly, once, with
cross-validation and gates, in PostRefine.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EFEJG6WBQv8th4UJFNe53N
leonarski_fandClaude Opus 5
9c19646f6a