re: CORRECTION -- the e106 slab is a container-dependent mis-decode, not a stray volume

One iteration ago I concluded assemble_ship was drawing a non-renderable
collision volume. That named the wrong cause, and decoding the same resource from
every container that holds it settles it:

  Stage_S01  172 verts 110 tris  49 x 23 x 42        <- a turret, correct
  Stage_S02  172 verts 110 tris  1600 x 2100 x 4800  <- wrong
  Stage_S08  same                1600 x 2100 x 4800  <- wrong
  Stage_S26  same                1600 x 2100 x 4800  <- wrong
  eleven others                  49 x 23 x 42        <- correct

Same resource, same vertex and triangle counts, correct in eleven containers and
wrong in three. So the placement is legitimate (e303_wep_01 is a small shared
turret cross-mounted on e101/e106), the original author's vbase-dedup explanation
of the capture's silence stands, and my "dedup would show one, not zero"
objection does not survive -- at its true size the turret is ordinary geometry.
The defect is in the mesh decoder.

The wider point: the decoder can produce wrong geometry WITHOUT declining. The
XBG7 audit counted 814 honest refusals; this is the other kind, silently 100x too
large. A screen for the signature (bounds exact multiples of 50, span > 1000)
flags 22-32 models each in S02/S03/S08/S26/S27, but it also catches legitimate
e_rou_* composite proxies, so that is a candidate list and not a bug count.

Next: diff the anchor scan's chosen vb0 for this resource between Stage_S01 and
Stage_S02 -- same resource, two outcomes -- and turn whatever distinguishes them
into a post-decode sanity check so a silent mis-decode becomes a decline.

Kept from the previous entry: the test can only fail one way, and cross-id
placement is genuinely narrow (2 pairs across 335 ships).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/re/BACKLOG.md

@@ -153,7 +153,7 @@ report needs re-grounding against a specific ship and a specific expectation.
 
 ---
 
-## ⚠️ The format layer is NOT exonerated — `assemble_ship` draws a non-renderable volume
+## ⚠️ The format layer is NOT exonerated — but the cause is a MIS-DECODE, not a stray volume
 
 **Found 2026-08-11 by finally doing the visual**, which the notes above kept
 naming as the next step. It overturns their conclusion.
@@ -177,9 +177,50 @@ e106_brg_01     202 verts, 202 tris   105 x  76 x 305
 ```
 
 **110 triangles, perfectly round axis-aligned bounds, and bigger than the ship it
-is mounted on.** That is not a turret. 🟡 It reads as a collision / trigger
-volume, and ✅ whatever it is, **the game does not draw it**: the runtime capture
-of e106 contains no `e303_wep_01` at all.
+is mounted on.**
+
+### CORRECTION (same day, one iteration later): it is not a volume — it is a bad decode
+
+The first reading of this was that `e303_wep_01` is a collision/trigger volume
+the assembler wrongly draws. **That is wrong, and the evidence that settles it is
+decoding the same resource from every container that holds it:**
+
+```
+Stage_S01   172 verts 110 tris   X[-24.5, 24.5] Y[0.0, 23.4] Z[-20.8, 20.8]   ← 49 × 23 × 42, a turret
+Stage_S02   172 verts 110 tris   X[-1000, 600] Y[±1050]      Z[±2400]         ← 1600 × 2100 × 4800
+Stage_S03…  172 verts 110 tris   49 × 23 × 42  (correct)
+Stage_S08   …                    1600 × 2100 × 4800
+Stage_S26   …                    1600 × 2100 × 4800
+```
+
+Same resource, same vertex and triangle count, **decoding correctly in eleven
+containers and wrongly in exactly three** (`Stage_S02`, `S08`, `S26`). So:
+
+- the **placement is legitimate** — `e303_wep_01` is a small shared turret,
+  cross-mounted on `e101` and `e106`, and at its true size it is unremarkable;
+- the original author's explanation of the capture's silence (**vbase dedup**)
+  stands, and my "dedup would show one, not zero" objection does not survive:
+  with the correct decode the turret is small, ordinary geometry;
+- **the defect is in the mesh decoder**, which resolved this resource's vertex
+  data differently in three containers.
+
+The render and the symptom are real; the cause named in the first version of this
+entry was not.
+
+### The part that matters more than this one resource
+
+**The decoder can produce wrong geometry without declining.** The
+[XBG7 audit](structures/xbg7-mesh.md) counted 814 resources it *refuses* — a
+visible, honest failure. This is the other kind: `e303_wep_01` decodes "fine" in
+`Stage_S02` and is silently 100× too large. Screening for the signature (bounds
+that are exact multiples of 50 with a span over 1000) flags 22–32 models in each
+of `S02`, `S03`, `S08`, `S26`, `S27` — **but that screen also catches legitimate
+`e_rou_*` composite proxies**, so it is a candidate list, not a count of bugs.
+
+**Next:** diff the anchor scan's chosen `vb0` for `e303_wep_01` between
+`Stage_S01` (correct) and `Stage_S02` (wrong) — same resource, two outcomes, so
+the divergence is directly observable — then use whatever distinguishes them to
+add a post-decode sanity check, so a silent 100× mis-decode becomes a decline.
 
 ### Why this was missed
 
@@ -205,6 +246,12 @@ Sweeping all 335 assembled ships for the signature *ship-scale span with under
 by capture absence, and by geometry. Some of the others may be legitimately large
 low-poly parts, and each needs the same three checks before being called a bug.
 
-**Next:** decide the rule that separates drawable parts from volumes (candidates:
-the node-name suffix, a descriptor flag, or the triangle-density heuristic), then
-re-point `static_assembly_matches_runtime_capture` so it also fails on extras.
+**Still true, and independent of the correction above:**
+`static_assembly_matches_runtime_capture` walks the capture's parts and looks each
+up in the static output, so **extra static placements can never fail it**. That is
+worth fixing regardless — it is the same one-way-test shape as the earlier
+`include_external` hypothesis.
+
+Also unchanged: only **two** cross-id placements exist fleet-wide (`e303_wep_01`
+on `e101` ×24 and `e106` ×36, across 335 assembled ships), so cross-id mounting is
+a narrow, real feature rather than a systemic guess.