diff --git a/docs/re/BACKLOG.md b/docs/re/BACKLOG.md
index 9cabdf1..3536d12 100644
--- a/docs/re/BACKLOG.md
+++ b/docs/re/BACKLOG.md
@@ -6677,3 +6677,33 @@ conclusion follows for `eff_e0044`/`eff_h308`, and the earlier "no mesh" remarks
 about `eff_e0058`/`_e0059`/`_e0060` are weaker than written. ❔ **Open: how an
 effect mesh is actually reached**, since `eff_n0071` is not a plain name string
 in any of the 166 packages.
+
+---
+
+## 🔑 2026-08-28 — effects split into two families by digit-width; `ptc_pack.xpr` holds one
+
+Item (a). The corpus already held the pointer — [[xbg7-mesh]] names
+**`ptc_pack.xpr`**, a 20 MB shared particle package listing **532 distinct
+`eff_*` resources** (527 three-digit, 3 four-digit, 2 unnumbered).
+
+Joined against the 137 effect names the datasheets bind:
+
+| bound name | in `ptc_pack` | not |
+|---|---|---|
+| **3-digit** | **71** | 39 |
+| **4-digit** | **0** | **27** |
+
+🔑 **Zero partials on the four-digit cell**, and that series is a closed
+three-letter set — `e` 10, `f` 12, `n` 5. Since `eff_e0033` was found in
+`Base.xpr`, the reading is **two effect families**: a shared three-digit library
+in `ptc_pack.xpr`, and a four-digit series living in per-model/base packages.
+
+⚠️ Unlike last iteration's refuted search, **this instrument passes its own
+control** — the same kind of byte search demonstrably reads 532 names out of
+this file, so a zero *within it* carries weight. The 39 three-digit misses
+cluster on `j` (22) and `t` (14); `ptc_pack` holds just one `j` name, so
+`eff_j###` is a third grouping elsewhere.
+
+🟡 **Not closed**: 66 of 137 bound effects still have no located home,
+`eff_n0071` included. ❔ Next: the `eff_j###` family and the four-digit series —
+not another disc-wide grep.
diff --git a/docs/re/structures/unit-substructure-records.md b/docs/re/structures/unit-substructure-records.md
index 28345b0..8657844 100644
--- a/docs/re/structures/unit-substructure-records.md
+++ b/docs/re/structures/unit-substructure-records.md
@@ -271,3 +271,40 @@ A known-live name the test cannot find means the test has no power here. So:
 Whatever ships `eff_n0071` is not a plain name string inside those 166 files,
 so effect meshes must be reached some other way. Finding that route is the open
 question; until then, only the positive half of this test counts.
+
+### 🔑 Effects live in two families, split by digit-width — `ptc_pack.xpr` holds one
+
+The open question from the last iteration was how an effect mesh is reached at
+all. The corpus already had the pointer: [[xbg7-mesh]] mentions **`ptc_pack.xpr`**
+and its `eff_*` entries. It is a 20 MB shared particle package in
+`hidden/resource3d/`, and it names **532 distinct `eff_*` resources** — 527 of
+them with a **three-digit** number, 3 with four digits, 2 unnumbered.
+
+Joining it against the effect names the datasheets actually bind:
+
+| bound name | in `ptc_pack` | not |
+|---|---|---|
+| **3-digit** (`eff_h308`, `eff_m…`) | **71** | 39 |
+| **4-digit** (`eff_e0033`, `eff_n0071`) | **0** | **27** |
+
+🔑 **Zero of the 27 four-digit names resolve in `ptc_pack`, and the four-digit
+series is a closed three-letter set** — `e` (10), `f` (12), `n` (5). Meanwhile
+`eff_e0033` *was* found in `Base.xpr`. So the disc carries **two effect
+families**: a shared three-digit particle library in `ptc_pack.xpr`, and a
+four-digit series that lives in the per-model and base packages instead.
+
+⚠️ **The instrument passes its own control this time.** The previous iteration's
+`.xpr` byte search was refuted because a known-live name returned nothing. Here
+the same kind of search **demonstrably reads names out of this file — 532 of
+them** — so a zero *within `ptc_pack`* is meaningful in a way the earlier
+disc-wide zero was not. That is the difference between a search that has been
+shown to work on the population being searched and one that has not.
+
+Among the 39 three-digit misses the letters cluster hard: `j` 22, `t` 14, `m` 2,
+`h` 1 — and `ptc_pack` contains just **one** `j` name against 149 `m` and 81 `s`.
+So `eff_j###` is a third grouping that is almost entirely elsewhere.
+
+🟡 This does not yet close the question — 66 of the 137 bound effects still have
+no located home, `eff_n0071` among them. But the route is now a real one with a
+number on it, and the next step is the `eff_j###` family and the four-digit
+series rather than another disc-wide grep.