6988e5ace14d52914ae957028cf417446e5120b4
Tier 2 slice 1 from COMPOSER-NOTES.md 3.4. A read-only, deterministic, headless measurement of a built strate: sample a coarse grid once, flood-fill the air once, derive every metric from that same grid. What it answers today: air fraction, air component count and largest component share (the swiss-cheese signal), walkable fraction, median feature scale, median vertical clearance -- and whether two points are actually connected. The connectivity verdict is the point. Coarse sampling LIES about it in the dangerous direction: a wall thinner than the sample step vanishes and two sealed caverns read as joined. So VF_AreConnected recovers the actual BFS route and re-walks that one corridor at one-voxel spacing; a true verdict is never returned on coarse evidence alone. It fired: 2 of 21 routes were coarse false positives. The test carries a negative control, because a green suite that cannot fail is what hid the last defect. Two of them, in fact: a direct probe of the known-solid inter-strate gap (AirFraction 0.00042), and -- Codex's improvement on the spec -- a diff-layer box filled solid and measured through VF_MeasureStrate itself, so an inverted sign is caught end to end rather than around the function under test. Build clean, 18 succeeded / 0 warnings / 0 failed. KNOWN, fix in flight: the interior window excludes a whole chunk (32 voxels) at each end to avoid a 4-voxel seal band -- 8x too much. On the fixture's 4-chunk strates that discards the floor, so the reported FlatPlain/CrystalChamber air fractions of 0.999 describe the open band above the floor, not the strate. The engine is right; the window is not. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Bp7FxoQcSoiuhxjuLr6aBM
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