re: cross-validate the code-derived layout against the earlier RAM-binding solver

Two independent derivations of the unit definition layout -- the earlier
disc-value-to-RAM-word solver and this session's extraction from the loader's own
key strings -- agree on 25 of 25 shared offsets, 0 disagreements. The code-derived
table covers 159 fields against 27 confirmed, while the earlier one uniquely holds
ScorePoint (+0x08c) and MassScore (+0x094).

Also flags a tentative entry as an artefact: Slalom_CutoffRatio at +0x00c records
2.8026e-45 / 1.4013e-45, which are the denormal readings of the integers 2 and 1 --
the same trap that produced a false YawDragFactor hit while building the new map.
INDEX updated.

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

docs/re/INDEX.md

@@ -22,7 +22,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | XBG7 mesh | ✅/🟡 | `sylpheed-formats/src/mesh.rs` + `tests/mesh_disc.rs` ([xbg7](structures/xbg7-mesh.md)) | **6 294 resources, 6 209 decode (98.7 %), 82 searched-and-missed** (2026-08-12, up from 5 480 / 87.1 %). Five evidence-driven fixes got there: **distinct anchor assignment** (no two resources may claim one buffer — proved by a capture showing the container holds both mirrored `e106` hull halves), the connectivity cap replaced by a **winding-consistency gate at 0.70**, **structural requirements on pre-pivot sub-meshes** (index range, then exact pool coverage), and **filtering after the assignment** so a subset query cannot differ from the full decode. Validated against a runtime capture that names the file offset of every buffer the engine drew: **46/46 drawn buffers claimed, 45 anchored exactly**. **No real mesh now decodes differently in different containers** — all 89 remaining cross-container disagreements are interchangeable 24-vertex bounding boxes, which no anchoring rule can pin (monotone order re-tested and refuted). Remaining misses attribute to the degeneracy/extent gate (42), winding (31) and coverage (9); the first was probed and its "obvious" fix refuted. Every decoded sub-mesh covers its own vertex pool |
 | Capital-ship part placement | ✅ | `sylpheed-formats/src/ship.rs` (static) + [runtime capture](ship-placement-runtime-capture.md) | Placement is **sound** (hull static-exact against the `e106` capture; cross-id mounting genuinely narrow, 2 pairs across 335 ships). The XBG7 mis-decode this row used to blame for "ships assemble wrong" — a shared turret ~100× too large in some containers — is **fixed** (2026-08-12, the exact-coverage requirement): `e303_wep_01` now decodes 49×23×42 everywhere and places at ±179 on the `e106` hull, and no real mesh disagrees across containers. A composite-node audit confirmed the assembler itself never applied a bad scale (all nodes scale 1.0, orthonormal). Still open: `static_assembly_matches_runtime_capture` walks capture parts only, so **extra** static placements cannot 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) |
+| 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**. **Re-derived independently 2026-08-13 from the loader's own key strings** (`sub_82341A20`; the field name for each store is a string in the image): **159 fields**, agreeing with this solver on **25 of 25 shared offsets**, verified at **406 values matching the disc and 0 disagreeing** over 11 live objects spanning UNIT and VESSEL — landed as `data/unit_definition_layout.txt` + `sylpheed_formats::unit_layout` + a no-emulator test, with **121 defaulted fields** read out ([live-unit-definitions](live-unit-definitions.md)). 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 |
 | UI screen layout (`.rat`) | ✅/🟡 | [ui-rat-layout](structures/ui-rat-layout.md) | One pak per UI screen; each RATC = one (context × language) build; every `<name>.t32` sprite has a `<name>.rat` **layout record** (BE u32; 1280×720 design space; scale/tint/X/Y, keyframes for animated elements, `opt ` link to the focused state). **The tutorial PAUSE menu and the title main menu both rebuild pixel-accurately from the disc.** `loop1.rat` is decoded — it is a **looping sprite animation**, not a composition. The **screen's draw list is the RATC bundle's own declaration table** (elements in back-to-front order, including the `eff*`/`deli*`/`msg` sprites that have no `.rat`, and excluding focused button variants reached via `opt `); its entry also carries a **parent element index** at `+32`. **A screen is fully reconstructible from its bundle**: the placement region right after the declaration table gives every element a keyframe group (header = element index + keyframe count, then 40-byte blocks of scale/tint/X/Y), including the `.rat`-less sprites — verified 11/11 on the tutorial pause bundle, with `pgp_ttrl_btn10`'s inline (546,288) matching its own record exactly |
 | Save file (`savedata`) | ✅/❔ | [savegame-format](structures/savegame-format.md) + [`tools/re-capture/savegame.py`](../../tools/re-capture/savegame.py) | `GDHA` container, zlib payload, chunk stream (`GDAA` / phase name / `GHAD` 122 B progress block / 16×20 B slot table / trailer). **Container and layout read off the title's own serializer `0x822C00E8` and verified by a byte-identical round-trip**; the whole save is 545 B. Payload offsets are also the live save object's offsets (`save+8` GHAD, `save+136` slots). A second save made in-game names **Points** (+24), **flight time in ms** (+4) and **clear ratio %** (+8) off the game's own Details panel; the payload is a **pure function of game state** (same state saved twice = byte-identical, only the header FILETIME and its uninitialised pointer padding move), and the 16 `SHAB` records are **not** the UI's 20 save slots. Difficulty vs stage is undecided — three fields hold 2. **A third save, taken after developing exactly one Arsenal weapon** (Light Machine Gun MG I, 4000 P), moves exactly three things: `+24` Points 4101→101 (which **separates it from `+28`**, that did not move), `+8` clear ratio 5→6 (so the ratio counts *collection*, not only stages), and two entries of the 54-byte blob — `2→4` for the item bought and `0→2` for the successor the game announced as newly developable, giving the blob its alphabet ✅ *0 locked / 2 developable / 4 developed* (only the `4`s are stored — `2` is re-derived at load). **Saves can also be written back**: three derived header fields (length at `+0x30`, payload length at `+0x8c`, `adler32` at `+0x8e`) are all that stand between a parse and a hand-written save that the title loads, and [`savegame_edit.py`](../../tools/re-capture/savegame_edit.py) re-wraps a real save byte-identically. That turned the blob's index space from blocked-on-story-progress into four probe saves — see the [economy note](arsenal-develop-economy.md) |

docs/re/structures/unit-struct-runtime.md

@@ -353,3 +353,27 @@ are the same numbers their already-captured base variants gave, so it would
 re-measure rather than test. A real test needs a stage with unfamiliar classes,
 i.e. story progress — which is now the *only* thing story progress is needed for
 here.
+
+## Cross-validated against the loader itself (2026-08-13)
+
+This layout was solved by binding disc values to RAM words. It has now been
+derived a second time, independently, **from the game's own code**: the loader
+`sub_82341A20` builds every key as `addi r4, r30, -N` (`r30 = 0x82088f94`), so the
+field *name* for each store is a string in the executable, and pairing each key
+with the first store after its accessor call gives the offset without any value
+matching. See [`live-unit-definitions.md`](../live-unit-definitions.md).
+
+**The two agree completely where they overlap: 25 shared offsets, 25 agree, 0
+disagree.** Each also covers what the other misses — the code-derived table has
+**159 fields** (vs 27 confirmed here) and is checked in as
+`crates/sylpheed-formats/data/unit_definition_layout.txt` with
+`sylpheed_formats::unit_layout` and a no-emulator regression test; this table
+still uniquely holds **`ScorePoint` (`+0x08c`)** and **`MassScore` (`+0x094`)**,
+which the key-string extraction did not pick up.
+
+⚠️ **One tentative entry here is an artefact and should not be trusted.**
+`Slalom_CutoffRatio` at `+0x00c` is recorded with values like `2.8026e-45` and
+`1.4013e-45` — those are the **denormal float readings of the integers 2 and 1**.
+`+0x00c` is below the first field the loader ever names (`+0x018`), and the same
+trap produced a false `YawDragFactor → +0x0c` hit when the code-derived map was
+being built. It is an int-typed word, not a ratio.