# Corpus-wide validation of the merged final-quad bounds fix

In July I reported and fixed an off-by-one boundary condition in Villa's shared
`loc_valid` geometry helper. PR #1264 was reviewed, approved, and merged by a
Villa maintainer. The original submission included a four-build ablation on one
PHerc1447 surface. This August follow-up measures the merged fix across the
entire frozen public TIFXYZ registry.

I surveyed all 450 registered roots, then downloaded and hashed every `z.tif`.
The scan completed 450/450 with zero failures. Ninety-six roots contain at
least one all-positive quad on the final row or column that the former bound
suppressed. The fixed domain admits 24,757 additional quads, corresponding to
49,514 OBJ triangles and 25,094 newly referenced vertices.

I then downloaded X and Y for all 96 candidates. The confirmation completed
96/96 with zero failures: all 24,757 candidate quads have finite X, Y, and Z at
all four corners; none were rejected.

The measured effect is systematic but sparse: 0.01206% of 205,330,341 valid
quads corpus-wide. It is concentrated in original surfaces—23,465 quads across
54/188 original roots (0.04852%)—with a maximum per-root fraction of 0.6145%.
I do not claim that every recovered point is correct papyrus or that this
changes downstream reading.

Evidence, scripts, tests, object URLs, hashes, and machine-readable results:
https://huggingface.co/datasets/AviadCoh/vesuvius-august-evidence/tree/main/boundary-corpus

Merged fix: https://github.com/ScrollPrize/villa/pull/1264