diff --git a/docs/re/structures/xbg7-mesh.md b/docs/re/structures/xbg7-mesh.md
index 5b12d85..9e5cd60 100644
--- a/docs/re/structures/xbg7-mesh.md
+++ b/docs/re/structures/xbg7-mesh.md
@@ -339,6 +339,43 @@ majority is the turret the render and the runtime capture both support.
 15) and nothing yet says which is right. Use the detector to flag; do not silently
 rewrite geometry on a vote.
 
+### ROOT CAUSE: the candidate list is container-global
+
+Traced 2026-08-12. `anchor_pool_mesh` (the **per-block** path, which is the one
+that handles single-sub-mesh resources like `e303_wep_01`) walks a candidate list
+built by `vertex_run_starts(bytes, data_base, stride)` — **one scan of the whole
+container per stride**, shared by every resource of that stride. It accepts the
+**first** candidate that validates.
+
+So a resource is anchored to *whatever block matches its signature first in file
+order*, and nothing ties that block to the resource it belongs to. Two resources
+sharing `(stride, vertex count, index count)` are interchangeable to this search.
+
+**The wrong block is not distinguishable by quality.** Tracing the accept for
+`e303_wep_01`:
+
+```
+Stage_S01   ACCEPT vb=4600480   pad=0  span=  49 ×  23 ×  42   passes 0.85 = true
+Stage_S02   ACCEPT vb=18403456  pad=0  span=1600 × 2100 × 4800 passes 0.85 = true
+```
+
+Both clear the strict winding-consistency gate, because the wrongly-taken block
+**is** real, coherent geometry — just another resource's. That rules out a whole
+family of fixes: no threshold, no scoring, no "pick the best candidate" changes
+this, and the earlier attempt to add best-of-N selection in the grouped-pool
+anchor duly changed nothing.
+
+**The search space has to be constrained instead.** Two candidates, in order of
+how much new format knowledge they need:
+
+1. **Per-resource data extents.** The XPR2 resource table gives each resource a
+   descriptor; if the geometry extent can be derived from it, restrict `starts`
+   to that range and the theft becomes impossible.
+2. **Monotonic anchoring.** If resources' data blocks follow descriptor order,
+   then resource *k*'s `vb` must lie after resource *k−1*'s — a cheap constraint
+   needing no new format knowledge. Testable against the 556 resources that
+   already decode consistently across containers.
+
 ### Where the mis-decode is *not*: the grouped-pool anchor
 
 An attempt to fix it by making `anchor_grouped_meshes` choose the **best-scoring**