re: the grouped pivot floor is not the blocker either -- anchor work plateaus at 98.7%

Sweeping XBG7_GROUPED_CONSISTENCY 0.85 -> 0.80 -> 0.75 decodes no additional
resources and leaves inconsistency at 39, while changing which geometry some
grouped models get -- strictly worse, so 0.85 stays. With the degeneracy/extent
fix already refuted, the remaining 82 misses are not a threshold away; they need
a structural answer (marker lists that do not map onto stored blocks), which
means a capture, not more tuning. Records the state of the four shipped changes.

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

crates/sylpheed-formats/src/mesh.rs

@@ -969,6 +969,13 @@ fn edge_cap() -> f32 {
     std::env::var("XBG7_EDGE_CAP").ok().and_then(|v| v.parse().ok()).unwrap_or(1.0)
 }
 
+/// Winding floor for the grouped-pool **pivot** (default `0.85`). The single-block
+/// path settled at 0.70 on measurement; this is the same question for the pivot,
+/// and `XBG7_GROUPED_CONSISTENCY` sweeps it.
+fn grouped_consistency() -> f32 {
+    std::env::var("XBG7_GROUPED_CONSISTENCY").ok().and_then(|v| v.parse().ok()).unwrap_or(0.85)
+}
+
 /// Smallest bounding-box extent a block may have (default `0.5`). An absolute
 /// floor on a format with no unit convention is a scale assumption, so it is a
 /// knob: `XBG7_MIN_EXTENT`.
@@ -1473,7 +1480,7 @@ fn anchor_grouped_meshes(
             // collapses well below 0.85, so only the true pad/pivot passes.
             let ib_k = ib0 + rel_ib[kmax];
             let vb_k = vb0 + off_v[kmax];
-            if !validate_block(bytes, ib_k, vb_k, vck, ick, decl, 0.85, true) {
+            if !validate_block(bytes, ib_k, vb_k, vck, ick, decl, grouped_consistency(), true) {
                 continue;
             }
 

docs/re/structures/xbg7-mesh.md

@@ -1042,6 +1042,29 @@ not obviously right, and both points are one env var apart
 (`XBG7_PAD0_CONSISTENCY`, `XBG7_EDGE_CAP`) for anyone who wants the conservative
 end.
 
+### The anchor work has plateaued at 98.7 % — state and what is left
+
+Four evidence-driven changes took the decoder from 5 480 to **6 212 of 6 294**
+resources (**98.7 %**), capture-verified anchors from 29/46 to **46/46**, and
+cross-container inconsistency from 125 to **39**:
+
+1. distinct anchor assignment (single-block, then grouped pools),
+2. the connectivity cap 0.28 → 0.42, then replaced entirely by
+3. the winding-consistency gate at 0.70, and
+4. structural requirements on pre-pivot sub-meshes (index range, pool coverage).
+
+**Two further threshold moves were tested and refuted**: the scale-free
+degeneracy test plus a lower extent floor (zero extra resources, inconsistency
+39 → 44), and lowering the grouped-pool **pivot** winding floor
+(`XBG7_GROUPED_CONSISTENCY`): 0.85 → 0.80 → 0.75 decodes **no more resources**
+and leaves inconsistency at 39, while quietly changing which geometry some
+grouped models get (the vertex total moves), i.e. strictly worse.
+
+So the remaining **82** misses are not a threshold away. They need a structural
+answer of the kind the `.dat` composites already showed — marker lists that do
+not map 1:1 onto stored blocks — and the honest next step is a capture of a stage
+containing them, not more tuning.
+
 ### Where the remaining 82 misses stand — and a refuted fix
 
 With the winding gate shipped, coverage is **6 212 / 6 294 = 98.7 %** and only