re: what the game actually reads at boot -- config.ini, and which

GameParts exist at all

Q6's second half, advanced but not closed, and the negative is the point.

config.ini is the disc's ONLY config file -- one find over the whole
extract -- and its own Shift-JIS header calls it the "Application /
GamePart initial settings table". Its [SYSTEM] section, which that same
comment says holds what the game and every game part share, is EMPTY. So
the boot order is not in disc-side configuration at all, and that search
space is now closed rather than merely unexplored.

What the file DOES carry is the language: XC_LANGUAGE_* -> eng/jpn/deu/
fra/esp/ita, defaulting to eng. That is the mechanism behind the EN/JP
build pairs in GP_TITLE and the <lang>.pak families -- a question the
corpus had described but never traced to its input.

Then the registry. Pulling every RegisterToFactory diagnostic string
binds 24 of the 29 GamePart ids to a C++ class, and five ids have no
registration site: 1, 2, 16, 18, 28. Id 1 is GP_ADVERTISE_DEMO, which
agrees with what I measured two iterations ago -- the attract loop is the
TITLE replaying ADV.wmv, not a transition into an advertise part. Marked
amber, not green: it is an argument from an error message, not from code.

Two things fall out for Q4: ids 3 and 4 are the same class
(GamePart_SaveLoad, one part with two ids), and the menu buttons' ids now
match the executable's own class names rather than a list of table names.
Still a name match, one level closer to the code.

What is still missing is the transitions themselves, and I say so: the
manifest gives the boot-side assets, config.ini the language, the
registry which parts exist. What decides to advance is in
GamePart_Title's code and that dig has not been started.

docs/port/HANDOFF.md

@@ -32,7 +32,7 @@ authored version can be deleted.
 | Q3 | paint order for the six screens | ✅ answered | **decoded**: a `u16` layer key at `+0x0A` of each `T8aD` sprite header, stable-sorted with declaration index; unkeyed elements get an implied key. Confirmed on 5 measured orders + `EXTRAS` vs a capture. One residual: the **tie-break** is unknown and bites on one element of the title — [`structures/ui-paint-order-key.md`](../re/structures/ui-paint-order-key.md) |
 | Q4 | button → GamePart | ✅ answered | **measured** which screen all **5** buttons open — `NEW GAME` → `DIFFICULTY` → `SELECT DATA`, not a hang. The **GamePart id is still a name match**, not a measurement — [`menu-navigation-semantics.md`](../re/menu-navigation-semantics.md) |
 | Q5 | navigation semantics | ✅ answered | **measured**: initial focus varies boot to boot (2× `TUTORIAL`, 1× `NEW GAME`); ⬆⬇ one step, **wraps both ends**; ⬅➡ do nothing; Ⓑ returns to the parent **with focus restored**; Ⓑ on the main menu → title; Ⓑ on the title → nothing — [`menu-navigation-semantics.md`](../re/menu-navigation-semantics.md) |
-| Q6 | boot sequence + what drives it | 🟡 partial | order observed and the attract cycle timed: ~8–10 s idle → fade to black → **`ADV.wmv` in full (137 s)** → title again. The **movie manifest** supplies the boot-side asset order (slot key = role); the code that decides to advance is still not decoded |
+| Q6 | boot sequence + what drives it | 🟡 partial | order observed and timed; the **manifest** gives the boot-side assets, **`config.ini`** the language, the **registration strings** which parts exist — but the *transitions* are in `GamePart_Title`'s code and are not decoded — [`boot-config-and-gamepart-registry.md`](../re/boot-config-and-gamepart-registry.md) |
 | Q7 | transitions | ✅ answered | a **fade through black**, drawn by the screen's own last-painting `.prm` quad. Fade-in ramp is **decoded** from its keyframes; the ~0.4 s fade-out is **measured** (not in the file) — [`screen-transitions.md`](../re/screen-transitions.md) |
 | Q8 | menu audio bindings | 🟡 mostly answered | the **UI cue vocabulary is decoded** (`SE_UI_CURSOR`/`DECIDE`/`CANSEL`/`IMPOSI`, all in `Static.slb` per `BANK_SE`); the event binding is a **name match**, and the SE audio is **not extractable yet** — [`menu-audio-cues.md`](../re/menu-audio-cues.md) |
 | Q9 | video binding + playback rules | ✅ answered | **decoded** from the movie manifest: `ADVERTISE_MOVIE`→`ADV.wmv` (boot intro *and* attract are one asset), `MS00A`→`S00A.wmv` is the new-game intro, `STAFF_ROLL`→the credits reel. ✅ **one Ⓐ skips a movie** (title at 57 s vs a 193 s baseline) — [`movie-binding.md`](../re/movie-binding.md) |
@@ -161,6 +161,25 @@ authored version can be deleted.
   for all 7 620 other banks is simply absent, so an individual cue's wave is not
   locatable. Next step is `Pj_Silph.xgs` (in `sound.pak`, TOC 9454).
 
+* **`config.ini` picks the language, and that is what picks the EN/JP build.**
+  The disc's **only** config file (400 bytes, at the root; one `find` over the
+  whole extract). Its `[LANGUAGE]` section maps the console's `XC_LANGUAGE_*`
+  value to `eng`/`jpn`/`deu`/`fra`/`esp`/`ita`, defaulting to `eng` — that code
+  selects `GP_TITLE`'s English or Japanese build and the `<lang>.pak` families.
+  ✅ decoded.
+  ❔ Its `[SYSTEM]` section — which the file's own comment says holds what the
+  game and every game part share — is **empty**, so the boot *order* is not in
+  disc-side configuration at all.
+* **Five GameParts are named but never registered.** Pulling every
+  `RegisterToFactory<N, class silph::GamePart_X>` diagnostic string binds **24 of
+  the 29 ids to a C++ class**
+  ([`data/gamepart-class-ids.txt`](../re/data/gamepart-class-ids.txt)). Ids `1`,
+  `2`, `16`, `18`, `28` have no registration site — including
+  **`GP_ADVERTISE_DEMO` (1)**, which agrees with the measurement that the attract
+  loop is the *title* replaying `ADV.wmv` rather than a separate part. 🟡 an
+  argument from a diagnostic string, not from the code.
+  Also: **`3` and `4` are both `GamePart_SaveLoad`** — one part, two ids.
+
 * **The GamePart id table** — 29 entries at `.rdata 0x820A1630`, confirmed by the
   executable's own registration strings. ✅ This is the screen vocabulary; which
   button reaches which entry is Q4 and is *not* part of it.