diff --git a/docs/plan/level-assets.md b/docs/plan/level-assets.md
index 41f80e5..278ee1a 100644
--- a/docs/plan/level-assets.md
+++ b/docs/plan/level-assets.md
@@ -1445,3 +1445,44 @@ and the value set is quantised. The bounding-box reading does not survive.
 
 **Not decoded:** what the three floats are, what `0x100` at `+0x00` counts,
 and what the 83 values at `+0x0c` are.
+
+## Tie geometry: no GS packet framing, and a control that nearly fooled me
+
+**Range measured:** level 0, the 73 tie span bodies (bytes `+0x40` onward),
+**2,585,856 bytes** pooled. Per-position distinct counts, an autocorrelation
+scan against a shuffled control, and a GS GIF tag test.
+
+**Result 1 -- the bodies are dense.** Every one of the 16 slot positions takes
+245 to 256 distinct values, with byte 15 zero on 81.3% and byte 7 zero on 78.8%.
+The best stride peak is 48 at +0.097, barely above 16 at +0.095 -- no period.
+
+**Result 2 -- no GS GIF framing at 16-byte alignment.** Testing whether byte 15's
+low three bits fall in 0..4, the GS tag range, gives **97.0%**.
+
+That looked like a strong hit until the control was done properly. A uniform
+shuffle gives **62.6%** -- which is exactly 5/8, what a random byte predicts --
+so the naive comparison reads as a 34-point excess.
+
+**The distribution-matched null is 97.0%, identical to the observation.** The
+whole "excess" was that byte 15 is 81% zero, and `(0 & 7) <= 4` is always true.
+Recomputed per alignment, the null tracks the observation everywhere:
+
+| align | matched null |
+|---|---|
+| 0 | 97.0% |
+| 2 | 75.5% |
+| 4 | 75.7% |
+| 8 | 96.7% |
+| 12 | 89.3% |
+
+**This is the control rule earning its place a second time.** A uniform shuffle
+is not a matched control when the data is skewed, and `AGENTS.md` already says
+so; the near-miss here was reading the 62.6% as a baseline without checking
+what the data's own distribution predicts. The tie bytes are concentrated on
+0, 1, 2, 3 and 63 -- suggestive in isolation -- and still carry no framing.
+
+**What this rules out.** The tie bodies are not GS GIF packet streams at 16-byte
+alignment, and they carry no measurable periodicity. With every slot position
+taking ~256 distinct values they are dense data -- fat vertices, as the roadmap
+expects -- and locating the vertex layout inside them needs a reference for this
+game's instanced-geometry format, not another stride scan.