docs(re): session log for 2026-08-11, and correct the capital-ship INDEX row

The capital-ship row still said placement was the open question. Today's work
says otherwise: placement is sound (hull static-exact, cross-id mounting is 2
pairs across 335 ships) and the user-reported "ships assemble wrong" is an XBG7
mis-decode instead. The row now says that and points at the backlog and the mesh
doc, and keeps the one-way-test problem visible.

SESSION-2026-08-11.md summarises the run for review, leading with the single item
that needs the user's decision (editing save slot 01, deliberately not done) and
separating findings, the two disc defects found, and the process notes.

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

docs/re/INDEX.md

@@ -20,7 +20,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | IXUD subtitle | 🟡/✅ | `sylpheed-formats/src/ixud.rs` + [movie link](movie-subtitle-link.md) | timed cues. **The movie↔subtitle↔voice link is solved — statically**, from the movie config record in `tables.pak` (schema `0x067025b9`), not from the running game as this row previously assumed: [101 movies mapped](captures/movie-subtitle-voice-map.csv), 94 with subtitles, 83 with voice, 21 with a telop overlay. 93 of 94 subtitle refs resolve in the language paks; **`SUBTITLE_S12B.tbl` is missing from all six languages** — a dangling reference on the disc. Naming is `SUBTITLE_<base>.tbl` / `VOICE_<base>` with six documented exceptions. The record's ~104 **script ids** are ❔ — positional pairing drifts by three because the IDXD pool dedupes repeated values |
 | Fonts (ttf/otf/ttc) | ✅ | `sylpheed-formats/src/font.rs` | standard OpenType, parsed via ttf-parser |
 | XBG7 mesh | 🟡/❔ | `sylpheed-formats/src/mesh.rs` + `tests/mesh_disc.rs` ([xbg7](structures/xbg7-mesh.md)) | weapons/props: declaration-driven variable stride (36 models), GPU-confirmed. **Stage containers: 5662 sub-models across 22 stages** via content-anchored grouped pools (`stage_models`). **Declined set now measured**: 6 294 resources, **5 480 decode (87.1 %), 814 declined** in 31/166 containers — and it is *not* "a few quantized hero bodies" but 492 `e*`, 142 `f*`, 73 `n*`, 23 `eff*` plus `*_dead` variants. The descriptor does **not** declare decodability (word[2] is a sub-mesh count; decoded and declined appear at every value), so the gap is the anchor scan, not an unread format flag — see [xbg7](structures/xbg7-mesh.md). **Silent mis-decodes also exist and are now measurable**: a resource shared across containers must decode to the same bounds, and **125 of 681 shared resources fail that check** with identical vertex/triangle counts — the decoder picked a different buffer of the same size. A majority vote across containers would resolve 104 of them (14 are 50/50), but that is 🟡 unvalidated beyond the one case with a render and a capture behind it |
-| Capital-ship part placement | 🟡 | `sylpheed-formats/src/ship.rs` (static) + [runtime capture](ship-placement-runtime-capture.md) | hull placement static-exact; external parts approximate statically. **Runtime capture** (Canary F10 → VS-constant WorldView) gives ground truth — validated on `e106` destroyer; not yet baked into the viewer |
+| Capital-ship part placement | ✅/🟡 | `sylpheed-formats/src/ship.rs` (static) + [runtime capture](ship-placement-runtime-capture.md) | Placement itself is **sound**: hull static-exact, validated against the `e106` runtime capture, and cross-id mounting is genuinely narrow (**2 pairs across 335 ships**). **The user-reported "ships assemble wrong" is NOT a placement bug** — it is an XBG7 **mis-decode** that makes one shared turret 100× too large in 3 of 14 containers ([backlog](BACKLOG.md), [xbg7](structures/xbg7-mesh.md)). Also open: `static_assembly_matches_runtime_capture` walks capture parts only, so **extra** static placements can never fail it |
 | Weapon fields defaulted on disc | ✅ | [runtime struct](structures/weapon-struct-runtime.md) · [DATA SHEET route](weapon-datasheet-runtime.md) | **Solved.** Canary maps guest RAM into `/dev/shm`, so the parsed `Weapon`/`Shell` objects are readable live; their layout is solved against disc ground truth (zero contradictions over 100+ records). All 126 weapons, exact numbers, no story progress needed — [4 393 values](captures/weapon-runtime-fields.csv) the disc does not carry. Supersedes the letter-bucket limit of the DATA SHEET route, which now serves as the independent cross-check |
 | Unit (craft/vessel) fields defaulted on disc | ✅/🟡 | [runtime struct](structures/unit-struct-runtime.md) | The parsed `unit\UN_*.tbl` definition object, vtable `0x820af844`, ≥`0x380` bytes, one per unit — **discovered, not assumed** (`unit_discover.py`), and distinguished from the spawned-entity class `0x820af030` by being one-per-ID and byte-constant within a run. Across runs only pointer words move — `--crosscheck` proves **no reported field offset is run-dependent** (two words, `+0x2c8`/`+0x2d0`, are stage-dependent and remain unidentified). 27 fields ✅ (21 units, 7 runs); the `Maneuver` block is **schema declaration order, 4 bytes/field, base `0x9c` with a two-slot gap after `AA_Roll_Min`** (29 anchors, 0 conflicts), which also pins 5 fields *no* disc record ever values. Angles are **radians at runtime, degrees on disc**. Unlike weapons, unit definitions are instantiated **per stage**, so coverage (21/110) grows by visiting missions — but a defaulted field is **not** a global constant: `Size_Y` provably inherits `Size_X` (7 independent units, 6 distinct values), and three more sibling rules are recorded ❔, recovering 65 values in units never visited — [values](captures/unit-runtime-fields.csv) |
 | Arsenal develop economy | ✅/❔ | [arsenal-develop-economy](arsenal-develop-economy.md) + [conditions](captures/arsenal-develop-conditions.csv) | The Arsenal reads `weapon.tbl` (item ids, in the 8-category display order) and `strings.tbl` (names, descriptions, and a **"Conditions to obtain"** block per item) out of `GP_HANGAR_ARSENAL.pak`. All **60** conditions are extracted: gates are stage completion, a predecessor item, or an **ace kill**; costs run 3 000–350 000 P and **20 items are free** once gated. `weapon.tbl`'s first record reproduces the in-game DATA SHEET exactly (Range D / Power E / Speed – / Weight 0.3 = Light / 4000 P) — later records are unreadable from the string pool alone because IDXD **dedupes repeated values**. Used to identify the save blob's index space, now **solved**: the blob follows **`strings.tbl`'s** order — the display order *plus* the cut items only the localisation file lists (`Adhesive Mine B2A`, `Ballista GSH`, …) — pinned by four hand-written probe saves (9 Stiletto, 21 Falcon, 39 Tomahawk, 48 Jamming System) and closing exactly at index 53. `weapon.tbl`'s id list is **not** the index space; that it is also 54 long is a coincidence, and the two agree only to index 32. The retail save's five unexplained owned entries are the cut items, shipped owned and never rendered |

docs/re/SESSION-2026-08-11.md

@@ -0,0 +1,69 @@
+# Session log — 2026-08-11 (autonomous run)
+
+What changed today, in the order a reviewer would want it, with the one item
+that needs **your decision** called out first.
+
+## Needs a decision from you
+
+**Editing save slot 01.** Save files can now be written back
+([savegame_edit.py](../../tools/re-capture/savegame_edit.py) re-wraps a real save
+**byte-identically**), and hand-written saves load. That unblocked several
+questions by probing throwaway slots. But the **title-menu screens read the
+auto-save (slot 01)**, so the remaining save-field questions (the difficulty
+enum, `SHAB.b`) need slot 01 itself edited — the only save with real progress.
+Not done. Recoverable (full content backup + slot 01's bytes archived), but it is
+your call. Everything else below was done in throwaway slots.
+
+## Findings, by area
+
+### Save format
+- **The develop differential**: buying one Arsenal weapon moves exactly three
+  fields — Points `+24` (which **separates it from `+28`**), clear ratio `+8`
+  (so the ratio counts *collection*, not stages), and two entries of the 54-byte
+  blob. Blob alphabet: `0` locked / `2` developable / `4` owned; only the `4`s
+  are stored, `2` is re-derived at load.
+- **The blob's index space is solved** — it follows `strings.tbl`'s item order,
+  **cut items included**, pinned by four probe saves and closing exactly at 53.
+- **`SHAB` is the per-stage record table**: record 0 = Stage 01, and `c` is its
+  best clear time in ms (`324773` = the `05:24.77` MISSION SELECT shows).
+- **Refuted**: every GHAD scalar as stage/difficulty (16 elements probed), and
+  "stage = filled `SHAB` count + 1".
+
+### Formats
+- **T8aD 96 % → 100 %** of the disc: a surface is a list of **sub-rectangles**
+  (`dst X, dst Y, w, h` per rectangle), not a 256 grid. The "~15 % variants" were
+  a wrong model.
+- **LSTA**: the count was never unreliable — it counts **sprites *and* `PRMD`
+  primitives** (64/64 exact).
+- **RATC**: "one level deep" is not a limitation; nested records are **leaves
+  that reference siblings by name** (10 144/10 148 resolve).
+- **UI screens are fully reconstructible from their bundle** — element list +
+  order (declaration table, with a **parent index**) and placement/animation
+  (keyframe region). **Validated against the running game to ±2 px.**
+- **Movie ↔ subtitle ↔ voice link solved statically** (101 movies) — `INDEX` had
+  it filed as needing the running game.
+- **XPR2 channel order confirmed** against the game (hue 23.3° vs 9.3°).
+
+### Meshes — the user-reported viewer bug
+- Root-caused, **after one wrong turn I corrected in place**: the giant slab on
+  `e106` is not a stray volume but an **XBG7 mis-decode** — the same resource is a
+  49×23×42 turret in 11 containers and 1600×2100×4800 in 3.
+- **New detector**: a resource shared across containers must decode to the same
+  bounds. **125 of 681** shared resources fail that check — a measured lower
+  bound on *silent* mis-decodes (distinct from the 814 honest declines).
+
+## Two disc defects found
+`SUBTITLE_S12B.tbl` (referenced by the movie table, present in **no** language)
+and `pmbase.t32` (placed by `pmbase.rat`, present **nowhere**). A reimplementation
+should skip a missing asset rather than treat it as a decode failure.
+
+## Process notes worth keeping
+- Several "the data is inconsistent" comments meant **our model was incomplete**
+  (T8aD variants, the LSTA count). Re-test such notes rather than routing around
+  them.
+- A test that walks the *oracle's* items and looks each up in our output **can
+  only fail one way** — it never sees extras. That shape hid the ship bug and,
+  earlier, `include_external`.
+- When a diagnosis has eliminated every hypothesis and the last step is *a
+  visual*, do the visual first. Three iterations went by before a 30-second
+  render showed it.