The port checked my pivot claim rather than taking it and found the nuance: the
sprite is odd-width, 399, so its true centre is 199.5 against a declared pivot of
200. Half a pixel, far inside the 0.70 and 0.48 px agreement, so it changes
nothing -- but "the pivot IS the centre" is the kind of sentence somebody leans on
for a sub-pixel claim later, so the page now says it is the centre rounded up.
And records the general form of the two bugs this exchange produced, which share
one cause. First, a leaf-composition rule was checked against alpha, which moves
about 0.3 levels per keyframe unit, so a one-keyframe association error barely
shifted it and the rule looked confirmed -- while the same span moved x by
1560 px. Second, fitting t from that same alpha manufactured an 11.5 px position
residual that did not exist and sent the consumer hunting a pivot rule to explain
it, because one byte of alpha quantisation is worth 1.5 to 1.9 keyframe units.
Solve on the fastest-moving field and check the slow one, never the reverse. The
second failure is the more expensive: failing to falsify leaves you falsely
reassured, but inventing a residual sends you looking for a mechanism.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QsEPXWVaEpyfudtR6re1Pd
258e1e63f7