diff --git a/docs/port/HANDOFF.md b/docs/port/HANDOFF.md
index 1fc47a4a..54173498 100644
--- a/docs/port/HANDOFF.md
+++ b/docs/port/HANDOFF.md
@@ -792,9 +792,18 @@ over the same span**. The rule matched on the insensitive quantity and was wrong
 on the sensitive one. **Check a new interpretation against the fastest-moving
 field you have, not the one that happens to agree.**
 
-❔ Left open: the residual **11.5 px** between 980.5 and 992.0. A rotation about
-a declared pivot rather than the centre would displace by roughly that, and
-nothing here measures it — so do not fit to close it.
+✅ **CLOSED — the 11.5 px was my fit's resolution, not geometry.** Closed by
+adding observables rather than tuning. The vertex buffer carries positions *and*
+colours at the same instant, so all four must agree on one `t`. Solved
+independently: quad A x → **357.88**, quad B x → **357.58**, alphas → 355.75 and
+354.09. ⚠️ **The alphas are ~50× less precise per unit** (0.27–0.33 levels/unit,
+so one byte of quantisation is worth 1.5–1.9 units = 6–8 px of sweep). At
+**t = 357.7** everything lands: centres **−0.70** and **−0.48 px**, alphas within
+one level, parent alpha **0** throughout.
+
+✅ **And there is no pivot correction to look for**: the leaf pivot is
+**(200, 90)** against a 399×180 sprite — the pivot *is* the centre, so rotation
+displaces it by nothing.
 
 ## Status
 
diff --git a/docs/re/structures/ui-leaf-vs-parent-alpha.md b/docs/re/structures/ui-leaf-vs-parent-alpha.md
index 749d7232..e586e908 100644
--- a/docs/re/structures/ui-leaf-vs-parent-alpha.md
+++ b/docs/re/structures/ui-leaf-vs-parent-alpha.md
@@ -108,9 +108,47 @@ t=355 is inside a long segment where a one-keyframe shift barely moves it, while
 can look confirmed on the insensitive quantity and be wrong on the sensitive
 one.**
 
-❔ The residual **11.5 px** between 980.5 and 992.0 is not explained by this and
-is left open — a rotation about a pivot rather than the centre would displace by
-about that much, and nothing here measures it.
+## ✅ The 11.5 px residual is CLOSED — it was the alpha-only fit's resolution
+
+Left open above as *"do not fit to close it"*. It is closed by **adding
+observables, not by tuning a parameter**.
+
+The draw's vertex buffer carries positions *and* colours at the **same instant**,
+so all four quantities must agree on one `t`. Solving for `t` from each
+independently:
+
+| observable | solved t | sensitivity | its own precision |
+|---|---|---|---|
+| quad A x | **357.88** | 4.00 px/unit | ±0.12 units |
+| quad B x | **357.58** | 4.06 px/unit | ±0.12 units |
+| quad A alpha | 355.75 | **0.326 levels/unit** | **±1.54 units** |
+| quad B alpha | 354.09 | **0.265 levels/unit** | **±1.89 units** |
+
+⚠️ **The alphas are ~50× less precise per unit of time**, because alpha is a byte
+changing by only ~0.3 levels per keyframe unit — so a single level of
+quantisation is worth **1.5–1.9 units**, which at 4 px/unit is **6–8 px of
+sweep**. The 11.5 px was that, not geometry.
+
+At the position-derived **t = 357.7**, every observable lands:
+
+| | predicted | measured | diff |
+|---|---|---|---|
+| quad A centre x | 991.30 | 992.0 | **−0.70 px** |
+| quad B centre x | 466.72 | 467.2 | **−0.48 px** |
+| quad A alpha | 195.64 | 195 | +0.64 |
+| quad B alpha | 182.95 | 182 | +0.95 |
+
+✅ **Sub-pixel on both positions, inside one byte on both alphas** — while the
+parent's alpha is **0** throughout. And the leaf **pivot is (200, 90)** against a
+399×180 sprite, i.e. the pivot *is* the sprite centre, so rotation displaces the
+centre by nothing. There is no pivot/rotation correction to find.
+
+⚠️ **The methodological point is the same one this exchange started with,
+inverted.** Earlier, a rule *looked confirmed* because it was checked against
+alpha — the insensitive field. Here the same insensitivity produced a spurious
+11.5 px residual. **The insensitive quantity does not just fail to falsify; it
+manufactures apparent error.** Solve on the fastest-moving field and check the
+slow one, never the reverse.
 
 ---