From 0625976ed7bab3bb7016b4883477345e76e855ac Mon Sep 17 00:00:00 2001 From: "Claude (auto-RE)" Date: Wed, 12 Aug 2026 17:40:22 +0000 Subject: [PATCH] re: the coverage fix moved 29 anchors, 22 of which carried another resource's geometry Whole-disc comparison at XBG7_COVER_SLACK=4 vs =1: 29 resources changed anchor, 3 stopped decoding, 6207 unchanged. Of the moved ones present in several containers, 0 matched the sibling consensus before and 9 after -- it moved them onto the block their own copies agree on and none away. 22 of 29 were carrying ANOTHER resource's geometry under their own name, including a shift chain in Stage_S28 where n054_bdy_l held n056_bdy_l's mesh and n056_bdy_l held n055_bdy_l's. Confidently-wrong-under-the-right-name is invisible to every count-based metric; the coverage invariant is what separated them. Co-Authored-By: Claude Opus 5 (1M context) --- docs/re/structures/xbg7-mesh.md | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/docs/re/structures/xbg7-mesh.md b/docs/re/structures/xbg7-mesh.md index 9c7de02..40a3960 100644 --- a/docs/re/structures/xbg7-mesh.md +++ b/docs/re/structures/xbg7-mesh.md @@ -1097,6 +1097,33 @@ that carry it) and `t901_e01_D` is 58×59×3013 (a mast). And `f101_bdy_01` flag at 6× while being **capture-verified exact** in the truth table — a useful reminder that a bulky hull is not a bug. +### What the exact-coverage fix actually reached + +The fix was justified on one resource (`e106_bdy_03`) and one render. Comparing +whole-disc decodes at `XBG7_COVER_SLACK=4` and `=1` shows what else moved: + +- **29 resources changed anchor**, 3 stopped decoding, 6 207 unchanged. +- Of the moved ones that appear in several containers, **0 matched the sibling + consensus before the fix and 9 match it after** — the fix moved them onto the + block their own copies agree on, and moved none away from it. +- **22 of the 29 were carrying another resource's geometry** under their own + name. + +The clearest case is a **shift chain** in `Stage_S28`: `n054_bdy_l` was decoding +`n056_bdy_l`'s geometry, and `n056_bdy_l` was decoding `n055_bdy_l`'s — each +resource landing on a neighbour's block, all of them plausible-looking meshes of +the right vertex count. `n054_bdy_l` decoded `(396, 315, 328)` in four containers +where its own copies agree on `(439, 284, 270)`. + +That is the failure mode that matters for a reimplementation: not a missing +decode, but a **confidently wrong one under the right name** — and no +count-based metric can see it, because every count is correct. It took the +coverage invariant (real blocks reach their pool's last vertex) to separate them. + +(Seven of the 29 carried geometry no resource claims. And the `ptc_pack.xpr` +`eff_*` entries in the list are small effect quads that all share one span, so +their "owner" attribution is weak — noted rather than counted.) + ### The containment screen, and a correction: the assembler is NOT at fault `examples/envelope_screen.rs` is the metric the eye actually used: assemble a