OpenMaidEngine/docs/sys4-format-notes.md

SYS4 Binary Format Notes (hex-first)

The script sections were derived initially from byte-pattern analysis of the 481 DATA1 .BIN files, before Ghidra work on AGE.EXE; their probe scripts live in tools/probe_*.py. The persistence sections combine native-code reconstruction, shipped-script consumers, installed read-only files, and port codec round trips. Confidence and remaining semantic limits are stated per format.

UPDATE 2026-07-05 — opcode set solved via Kelebek1's table. Everything below under "Instruction stream — PARTIAL" is now resolved: code = instructions of <opcode:u32> + argc*(<argtype:u32><value:u32>), length 1+2*argc; inline strings live after code inside [0,F8), so stop decoding at the first type-2/0x64 arg offset. 476/476 scripts decode clean (0 unknown opcodes). Header fields F0–F5 are local-variable counts (F0=local_integer_1, F1=local_floats, F2=local_strings_1, F3=local_integer_2, F4=unknown, F5=local_strings_2). See vm-mapping-plan.md and vm-map/opcodes.toml. The tag values below (0x71/0x03/0x8F etc.) are the opcodes at table targets: 0x8F=call, 0x03=call-script, 0x71=u0041A7B0.

SYS4INI directory and per-game settings trailer — CONFIRMED

SYS4INI.BIN is not only the asset catalog. Its S4IC LZSS stream begins with the archive names and 80-byte file records documented in asset-resolution-re.md, then continues with VM-bank metadata and a NUL-delimited per-game engine-settings trailer. tools/parse_sys4ini.py currently consumes only the directory prefix.

After the directory prefix, Himegari's decompressed stream has this tail:

decompressed offset  field
0x102488             vm_metadata_bytes:u32 = 0x90
0x10248c             vm_metadata[0x90]
0x10251c             settings_string_bytes:u32 = 0x2bb
0x102520             setting_pair_count:u32 = 36
0x102524             repeated { key:cstring, value:cstring }[36]
0x1027df             end of decompressed stream

The string-byte count covers only the concatenated key/value strings, not the preceding pair count. Keys are ASCII, values are CP932, and every key and value is individually NUL-terminated. Native engine_settings_import_sys4ini_pairs@0x46da80 matches keys case-insensitively and rejects an unrecognized key rather than silently retaining it.

Himegari's complete serialized list, in file order, is:

#	Key	Value
1	CREATEOBJECT	2
2	DRAWMODE	1
3	DEPENDMOVIESOUND	1
4	SCREENX	800
5	SCREENY	600
6	FONT	ＭＳ 明朝
7	ENABLEANTIFONT	1
8	ANTIFONTVERSION	3
9	FULLSCREENBIT	32
10	SCREENWARNING	1
11	NOSETMUSIC	3
12	MENU_SAVE	0
13	MENU_MESWINA	0
14	MENU_RCLICK	0
15	MENU_MESSPEED	0
16	MENU_USEANTIFONT	0
17	MENU_MESSAGE	1
18	MENU_SOUNDONOFF	0
19	ENABLEMEMFLIP	0
20	CLICKONUP	1
21	ALWAYSBACKUPSURFACE	0
22	CANCELMESSKIPONCLICK	2
23	CONTROLDISIBLECURSOR	1
24	COEXISTMESSKIP	1
25	REDRAWTEXTONKEY	0
26	WHEELKEYUP	8
27	WHEELKEYDOWN	9
28	USEAPPDATAFOLDER	1
29	SAVEPATH	Eushully\姫狩りダンジョンマイスター\SAVE
30	REGFILEPATH	Eushully\姫狩りダンジョンマイスター
31	COPYRIGHT	Copyright (c) Eushully 2009
32	SAVEVERSION	310
33	GAMEVERSION	1.00
34	RCVERSION	23
35	VERREGPOS	70724B91-F673-40FB-9EC4-5DE21EA68367
36	REGKEY	1886538641

This list is the canonical serialized-data inventory. Native consumers, compiled fallbacks, settings that are inert under Himegari's selected renderer, and current port coverage are cataloged in engine-re.md under "SYS4INI startup-settings catalog."

SCREENX=800 and SCREENY=600 are independently corroborated by Kamidori's 1024x576 pair, proving that the authored logical canvas is per-game data. Fullscreen/display-mode settings are separate from these logical dimensions. USEAPPDATAFOLDER and SAVEPATH select the native Windows save root; fixed save filenames remain AGE policy rather than trailer or script strings.

Native persistence files — Himegari 3.10

This section is the canonical binary-format specification for the persistence files used by Himegari. Native function provenance, opcode behavior, filesystem policy, and restore control flow remain in engine-re.md; game-global meanings remain sourced from vm-map/globals.toml and its generated global-reference.md.

Unless noted otherwise, offsets are byte offsets, integers are little-endian DWORDs, and strings are NUL-terminated CP932. Himegari separates four physical domains:

File	Scope	Structural owner	Semantic owner
SAVE.DAT / SAVE.BAK	whole profile	AGE's typed selected-cell payload inside the common save container	scripts choose which integer/string global cells to persist
RT.DAT / RT.BAK	whole profile	AGE's standalone S3RT ReadTextDB	script resource ids and T1 message boundaries identify the flags
SAVE%02d.DAT	one numbered slot	AGE's common container, full VM-state layout, and appended text-history tail	scripts populate live state, choose the frame cutoff, and request a slot save
SAVE%02d.STH	one numbered slot	AGE's BMP writer/reader	scripts choose the captured surface and slot

The menu-preview record is not read from RT.DAT. Its timestamp/playtime comes from the numbered .DAT header, its screenshot comes from .STH, and its title/location/name/stats/difficulty/ending history come from slot-indexed selected cells in shared SAVE.DAT. The numbered .DAT still contains the full restorable VM state; SAVE.DAT holds presentation-oriented copies so SAVE.BIN can list slots without decoding every numbered body.

Common S3SD / S4SD .DAT container — CONFIRMED

Shared SAVE.DAT and numbered SAVE%02d.DAT use the same wrapper. RT.DAT does not: it has the standalone S3RT layout documented below. The fixed .DAT header is 0x124 bytes:

Offset	Size	Field
0x000	4	ASCII magic S3SD or S4SD
0x004	4	compatibility id
0x008	0x100	NUL-terminated CP932 game id area
0x108	0x10	Win32 SYSTEMTIME: eight little-endian WORDs
0x118	4	accumulated playtime in seconds
0x11c	4	signed SaveVersion1, selecting the logical state layout
0x120	4	signed SaveVersion2, selecting the payload-codec subversion

Himegari uses game id 姫狩りダンジョンマイスター and versions 3.10. Shared SAVE.DAT uses compatibility id 0x4a343234; installed numbered files use the distinct id 0x42323234.

A 0x14-byte codec frame begins at file offset 0x124, and expanded data begins at 0x138:

Frame offset	File offset	Size	Field
+0x00	0x124	4	expanded-data DWORD count; always even
+0x04	0x128	4	MSB-first CRC-32 of expanded bytes
+0x08	0x12c	4	reflected CRC-32 of expanded bytes
+0x0c	0x130	4	rolling XOR seed
+0x10	0x134	4	nonzero odd multiplier; only the low 16 bits are valid

The logical payload is protected in this order:

1. Prefix the payload with two DWORD CRCs over the payload: MSB-first CRC-32, then reflected CRC-32.
2. For SaveVersion2 >= 2, optionally compress that checked buffer with the 4 KiB LZSS dialect and wrap it as {original_bytes, consumed_bytes, stored_bytes, stored_data, padding}. The first two lengths agree. If compression does not shrink the data, stored_bytes == original_bytes and the bytes are verbatim.
3. XOR each source DWORD with the current seed. Multiply its high and low 16-bit halves separately by the current odd multiplier, emitting two DWORD products. Advance the seed by 0x0b0b0b0b and the 16-bit multiplier by 0x0b02 for each source DWORD.
4. Store CRCs of the expanded products in the outer codec frame.

The inverse requires both products to divide exactly by the current multiplier and both quotients to fit 16 bits. This supplies an integrity check in addition to the two outer and two inner CRCs.

The LZSS stream uses a zero-filled 4096-byte ring starting at 0xfee. Each LSB-first flag byte controls eight tokens (1=literal); a match token stores a 12-bit ring offset and four-bit length-3, allowing lengths 3 through 18. The container's expanded-data count determines where it ends. Numbered files may append another domain after that boundary, so a reader must retain the consumed byte count rather than assuming the container occupies the entire physical file.

Shared SAVE.DAT logical payload — CONFIRMED

After decoding the common container, the shared payload is sequential:

Order	Field
1	catalog_count:u32, then the encrypted base-catalog unlock table
2	integer_count:u32, then integer_entries[integer_count], 16 bytes each
3	string_count:u32, string_blob_dwords:u32, then the DWORD-padded string blob
4	for version 3.10 or later, selector_counts[256]:u32 for append-catalog unlock tables
5	for version 3.10 or later, extended_count:u32, then the flattened encrypted append tables
6	reserved_tail[9]:u32

An integer entry is:

Entry offset	Size	Field
+0x00	0x0c	typed key field
+0x0c	4	raw integer value

The meaningful key bytes are {type_tag, address_hex[8], NUL}. Integer cells use raw type byte 0x03; the address is eight ASCII hexadecimal digits naming the resolved VM global-bank index. Bytes 10 and 11 in the fixed integer key field are unused native stack residue and cannot be required to be zero when importing original data.

The string blob repeats {typed_key_cstring, value_cstring} string_count times. String keys use raw type byte 0x05 plus the same eight-digit address and NUL; values are CP932. The stored blob length is a DWORD count. AGE rounds with (unpadded_bytes / 4) + 1, deliberately adding a whole zero DWORD when the last value already ends on a DWORD boundary.

The catalog sections are AGE's profile-wide resource-seen/unlock database. Each encrypted table begins with two header DWORDs:

Table word	Meaning
0	private exponent XOR 0x87912345
1	modular-exponentiation modulus
index + 2	zero when locked/unseen; otherwise the encrypted resource marker

Loading computes plain = cipher^private_exponent mod modulus. A marker is available when its low word equals low16(index * 0x053d6f99 + 0xb0b0b0b0). Native asset_open_indexed_entry writes that marker only after successfully opening the resource, and opcode 0x19d queries it. Thus ordinary CG assets unlock when their AGF is opened and H-scene entries unlock when their SP script is opened.

The base table maps universal resource ids whose high byte is zero. For version 3.10 or later, selector_counts[selector] gives the slot count of each append catalog; the extended array has its own two-word crypto header followed by those selector tables concatenated in selector order. Packed resource ids use the high byte as selector and the low 24 bits as the per-catalog index. Runtime lookup accepts selectors 1 through 127.

The nine-DWORD tail consists of one explicit terminator plus eight DWORDs produced by the native allocation formula. It remains compatibility-owned rather than mod storage.

The installed Himegari profile is a complete oracle: version 3.10 decodes to 13,210 base-table DWORDs (13,208 resource slots), 24,070 integer cells, 605 string cells, selector entry 1 equal to 81, 83 extended-table DWORDs (two header plus 81 resource slots), and nine tail DWORDs. The port copy contains 7,966 valid base markers and 75 valid append markers. Those include all 851 CGINIT gallery images and all 118 SPINIT H-scene scripts; a different encryption key can change every nonzero stored DWORD without changing the decoded unlock set.

The integer/string maps are AGE's generic selected-cell service, not copies of whole global banks. Himegari scripts assign their meanings through opcodes 0x1a2/0x1a3 and 0x1a9/0x1aa. Known slot-preview banks include chapter/title, location, protagonist name, portrait entity, level, training count, growth, personality, difficulty, cleared-ending mask, and installed-append mask. Their canonical addresses and semantics are generated in global-reference.md from vm-map/globals.toml; the cleared-ending value is a 15-bit NG+/inheritance mask whose set bits select the displayed ending badges.

Shared RT.DAT (S3RT) — CONFIRMED

RT.DAT is not wrapped, transformed, compressed, or checksummed like the .DAT save container. It is a standalone ReadTextDB with a 0x114-byte header:

Offset	Size	Field
0x000	4	ASCII magic S3RT
0x004	4	compatibility id (0x4a343234 for Himegari)
0x008	0x100	NUL-terminated CP932 game id area
0x108	4	major version (1)
0x10c	4	minor version (0)
0x110	4	script-record count

At 0x114 are all 12-byte script records:

Record offset	Size	Field
+0x00	4	raw packed SYS4/AAI script resource id
+0x04	4	message count
+0x08	4	serialized native heap pointer residue

After the complete record table, each record's message_count DWORD flags follows in record order. Zero means unread and nonzero means read. The third record word is process-local residue rather than a portable offset; AGE allocates and replaces it on load. Readers accept original nonzero values, while portable writers emit zero.

Message indices are positions in that script's T1/F7 table, whose entries point to op-0x71 read-message boundaries. Thus the file is profile-wide engine state derived from game scripts, not an arbitrary script-selected persistence table and not numbered-slot state.

The installed Himegari file is exactly 76,752 bytes: 192 records plus 18,543 flag DWORDs consume it without trailing data. Base script SC0000 has packed id 0x22 and 320 flags, exactly matching its T1 count.

Numbered SAVE%02d.DAT, logical layout 3 — CONFIRMED FOR HIMEGARI

Himegari's numbered file begins with the common container using compatibility id 0x42323234, SaveVersion1=3, and SaveVersion2=10. The header supplies the save-menu timestamp and accumulated playtime without decoding the body.

The decoded layout-3 body begins:

Offset	Size	Field
0x000	4	terminal saved-frame index, called cutoff; frame count is cutoff + 1
0x004	4	saved frame-owner/context word
0x008	4	current direct-name BGM track id
0x00c	0x28	ten packed SFX resource ids, one per retained channel
0x034	0x4b0	100 resource-reload records of three DWORDs
0x4e4	0x4e20	1,000 surface-reload records of 20 bytes
0x5304	(cutoff + 1) * 0x414	saved script-frame records
0x5718 + cutoff * 0x414	variable	global banks and retained graphics

Each 0x414-byte frame is:

Frame offset	Size	Field
+0x000	4	parent context
+0x004	4	packed script resource id
+0x008	4	saved local-return count, at most 256
+0x00c	up to 0x400	T3 local-return indices
+0x40c	4	T1 resume/message-boundary index
+0x410	4	T2 resumable call-script index; forced to -1 on the cutoff frame

The T1/T2/T3 indices refer to the three footer tables in the saved SYS4 script. T1 restores the active message boundary, T2 restores the inter-script call site, and T3 entries restore local returns as T3[index] + 3.

The variable section starts with six DWORD counts in this order:

1. integer globals;
2. raw float storage;
3. string globals;
4. integer-pointer globals;
5. string-pointer globals;
6. local pointer scratch.

The integer and float arrays follow their counts. String count comes from bank count 3, but its storage begins with an additional string_blob_dwords followed by that many bytes of concatenated NUL-terminated CP932 strings and DWORD padding. The three pointer-family DWORD arrays follow.

These counts are serialized mutable-prefix lengths, not declarations that every typed runtime bank ends there. Native deserialization zeroes and replaces only each counted prefix. Initialization-authored definitions after the prefix remain live: in Himegari the saved integer prefix ends at 0x6241b, before unit/stage definition tables such as 0x66716 and 0xe8275, while the saved string prefix ends at 0x315, exactly where unit_story_display_names begins. Clearing the whole runtime dictionary during import therefore destroys data that is intentionally absent from the numbered file.

Retained graphics then uses:

0x00  gfx_record_size:u32              # 0x2d4
+0x04  gfx_object_count:u32
+0x08  repeated sparse entries:
         handle:u32
         record[0x2d4]                 # 0xb5 meaningful DWORDs
         padding[0x87c]
       entry stride = 0x2d5 DWORDs = 0xb54 bytes
...    range_first:u32
...    range_count:i32
...    range_transform_record[0x2d4]
...    native allocation slack

The sparse stride is not an allocator-only artifact. Both native writer and reader hold a DWORD pointer: after the handle, they copy 0x2d4 bytes but advance by 0x2d4 DWORDs. Consecutive handles are therefore 0x2d5 DWORDs apart. Early experimental port saves incorrectly packed {handle,record} contiguously; compatibility import recognizes that layout, while all new output uses the native sparse form.

The 1,000 surface records preserve the native 20-byte metadata cells verbatim:

Offset	Size	Meaning
+0x00	4	signed resource id; -1 means no reloadable asset
+0x04	4	packed color key
+0x08	4	reload-on-restore flag
+0x0c	4	unknown lifecycle field; cleared with +0x08 at script entry
+0x10	4	blank/mutable created-surface flag

Initialization writes resource id -1 to every otherwise-zero record. Ordinary asset load, blank-surface creation, and release do not synthesize or clear the reload flag; opcode 0x259 clears +0x08 and +0x0c across both live/saved tables at script entry. During normal layout-3 restoration AGE reopens only records whose reload flag is one and whose resource id is nonnegative. Flag-zero records describe surfaces expected to remain live across the load. The installed file is decisive: all 1,000 reload flags are zero, while SYSTEM4's reusable choice-frame atlas remains recorded as resource 0x3383 in slot 15. A separate configuration-gated path can release all 1,000 surfaces before this loop, but Himegari's registered CreateObject=1, AutoFreeTex=0 defaults leave it inactive. A retained 0x2d4 record is structurally complete but not every internal graphics field is semantically named. Native gfx_object_init_default initializes six embedded 4x4 matrices (current/target scale, rotation, and translation) to identity, packed colors at +0x60/+0x64/+0x240 to 0xffffffff, and other fields to zero. Deserialization initializes an object and then overwrites all 0x2d4 bytes, so a compatibility writer must emit or preserve those defaults rather than zero-fill unnamed fields. The graphics sizing term remains larger than the meaningful sparse entries and range record (0x2e1 + object_count * 0x2d8 DWORDs), leaving final allocation slack as well.

The installed SAVE00.DAT validates the complete layout-3 decode: cutoff 1, global-bank counts [402459,1,789,1,1,1], current BGM id 0x18, retained SFX ids 0x3321 (channel 1) and 0x2aea (channel 2), and 211 retained graphics objects.

Appended text-history tail

The common container's expanded-data count ends before the numbered file ends. Layout 3 appends a separate text-history stream immediately at that consumed boundary:

Tail offset	Size	Field
+0x00	4	logical byte length
+0x04	4	duplicate logical byte length
+0x08	4	stored byte length
+0x0c	variable	the same 4 KiB-ring LZSS stream, or verbatim bytes when lengths match

The decoded history data is:

1. entry_count:u32, then entry_count pairs {layout_slot:i32, first_record_index:i32};
2. record_count:u32, then record_count records of 11 DWORDs;
3. string_blob_dwords:u32, then a DWORD-aligned CP932 string blob whose DWORDs are bitwise inverted.

Each 11-DWORD record stores layout slot, origin X/Y, width/height, primary value, auxiliary value, primary font size, text color, cursor Y, and flags. The string blob contains one NUL-terminated string per record. The installed save has a 21-byte physical history tail, and container plus tail consume the file exactly.

Numbered SAVE%02d.STH thumbnail — CONFIRMED

The thumbnail is a separate ordinary BMP under a nonstandard extension:

• BM file signature and 0x36 pixel offset;
• 14-byte bitmap file header plus 40-byte BITMAPINFOHEADER;
• uncompressed 24-bit BGR pixels;
• bottom-up positive height;
• rows padded to four-byte boundaries.

Installed Himegari thumbnails are 112x84 and 28,278 physical bytes. The native writer stores bfSize=28,264, omitting the physically present 14-byte file header from that field while retaining the correct physical header and pixel offset. Compatibility writers reproduce this harmless historical quirk.

Copy, move, and delete operations treat .DAT and .STH as a pair, but neither file contains the other.

Scope and remaining uncertainty

The following are complete enough for compatible import/export:

• the common S3SD/S4SD header, CRCs, optional LZSS wrapper, and DWORD transform;
• Himegari's shared SAVE.DAT 3.10 section boundaries and typed selected cells;
• RT.DAT 1.0 records and flag arrays;
• Himegari's numbered layout-3 fixed state, global banks, frames, graphics region, and history tail;
• .STH BMP encoding.

The remaining uncertainty is deliberately narrower:

• numbered layouts 1 and 2 are structurally identified but are not the implemented or installed Himegari compatibility target;
• some shared selected cells and the nine-DWORD tail remain opaque at the game-semantic level;
• the 0x2d4 retained-graphics record is byte-bounded, but not every field is named.

This distinction is important: AGE owns most numbered-save and ReadTextDB structure, while Himegari scripts primarily own the values in live VM globals, the save cutoff/invocation, and the semantic choice of selected SAVE.DAT cells.

Header — CONFIRMED

Fixed 60-byte (0x3C) header: 8-byte magic + thirteen little-endian u32 fields. Verified across all 481 files.

off   field  meaning                                    evidence
0x00  magic  "SYS4422 " (0x53 59 53 34 34 32 32 20)     481/481 identical
0x08  F0     local integer count
0x0C  F1     local float count
0x10  F2     local string count
0x14  F3     local integer-pointer count
0x18  F4     second pointer-family count (exact subtype unresolved)
0x1C  F5     local string-pointer count
0x20  F6     = 0x1C always                              481/481 == 0x1C  (header-size marker)
0x24  F7     table-1 entry count                        see below
0x28  F8     table-1 offset  == code-section length     ordering F8<=F10<=F12<=EOF
0x2C  F9     table-2 entry count
0x30  F10    table-2 offset
0x34  F11    table-3 entry count
0x38  F12    table-3 offset
0x3C  body   dword stream (code + 3 tables + strings)

All offsets/counts are in DWORDS (×4 bytes), relative to body start (0x3C). The 0x1C in F6 is the only byte count — it's the offset from F6's own position (0x20) back-referenced, i.e. a self-describing "28 bytes of descriptor follow" marker consistent with the SYS4/SYS5 family.

Section layout (CONFIRMED — 0 ordering violations, 481/481)

body[0        .. F8)    CODE          bytecode instruction stream
body[F8       .. F10)   TABLE-1  (F7 entries, 1 dword each)  -> read-message boundaries (op 0x71)
body[F10      .. F12)   TABLE-2  (F9 entries, 1 dword each)  -> call-script sites (op 0x03)
body[F12      .. EOF)   TABLE-3  (F11 entries, 1 dword each) -> local-call sites (op 0x8F)

Every table entry is exactly 1 dword — a pointer (dword index into body). Solved algebraically across the whole corpus: (F10-F8)/F7 == (F12-F10)/F9 == (EOF-F12)/F11 == 1 with zero non-integer results.

The three tables are typed pointer indexes (CONFIRMED)

Each table points at body locations, and the dword at every target is a constant tag identifying the pointed-to construct:

Table	count/off	Target dword tag	Hits	Meaning (inferred)
T1	F7 / F8	0x71	26,445/26,445	per-script read-message boundary index
T2	F9 / F10	0x03	3,018/3,018	resumable call-script sites
T3	F11 / F12	0x8F	72,941/72,941	local-call sites used to reconstruct return stacks

100% type purity — not a single target had a different tag. Native read_text_db_find_message_index@0x468f50 searches T1 for the code DWORD coordinate most recently snapshotted by op 0x71; its zero-based entry index and F7 count are the message index/count stored in shared RT.DAT. Thus T1 is not a generic label table even though every entry is a control-structure site. Numbered layout-3 frame serialization proves the remaining roles: saved d259 indexes T1, d260 indexes T2, and each intra-script return maps through T3 (restored as T3[index]+3).

Instruction stream — PARTIAL

The code section is a flat dword stream. Recurring "type/opcode" dwords observed: 0x03, 0x55, 0x6E, 0x6F, 0x71, 0x72, 0x8F. These read as operand-type tags in a tagged-operand VM rather than raw opcodes, e.g. the repeating shape:

... <TAG> <value> ...        tag 0x02 => string pointer (see below)
... 0x71 0x00 0x01 0x55 ...  label marker + following instruction

• First body dword is 0x259 (601) in 301/481 files — likely a standard "script entry" / prologue opcode. Second-most-common openers are small ints.
• 0x55 appears pervasively as an instruction lead — probably the most common opcode (statement / expression separator).

Full opcode semantics need the VM dispatch loop in AGE.EXE — that's the Ghidra task. These tags give a head start on labeling the disassembly.

Strings — CONFIRMED

• Stored inline in the body as byte-complement (XOR 0xFF) cp932 / Shift-JIS, packed 4 bytes per dword, NUL-terminated (a \0 byte, i.e. 0xFF after XOR, ends the string), then padded to the next dword.
• Referenced by a tagged operand: the dword 0x02 immediately followed by the dword-offset of the string. Confirmed directly by xref:
  • MENU.BIN: ...2 30b... @0x2A9 → offset 0x30B = "ＭＳ 明朝"; ...2 30e... → "loadmesskip menu"
  • SC0030.BIN: ...2 ef80... → "▼G0030　２章マップ０２１クリア"; ...2 ef89... → "「よし、素晴らしい成果だな」"
• Decoder (validated — pulls clean Japanese dialogue):

  raw = bytes(b ^ 0xFF for b in body[off*4:])   # until a 0x00 appears
  text = raw.split(b"\0")[0].decode("cp932")
  

• Scene scripts hold the full dialogue; e.g. SC0030.BIN decodes to readable story text, choice-branch labels ("本来の分岐", "チェック用"), font names ("ＭＳ 明朝"), and engine directives ("loadmesskip advset", "ＡＤＶパート").
• Non-scene scripts (MENU, ADDEXP) contain only a handful of control strings — consistent with the inventory's subsystem/data-table categorization.

Inline integer arrays — CONFIRMED

Opcode 0x64 operand 2 points to a footer blob in the same body-dword coordinate space as strings. The blob is [count:u32, value0:u32, ... valueN:u32]; these dwords are stored plainly in the original SYS4 file. For example, HISTORY.BIN@0x13d4 is [4, 0, 5, 0, 538], and its fifteen blobs initialize the backlog UI's rectangle, coordinate, and lookup arrays. An op-0x64 reference lowers the executable-code boundary just like a type-2 string reference.

Native AGE.EXE applies a per-context rotate/XOR representation after loading script data and reverses it inside the opcode handler. That transformation is not part of the on-disk format: file readers and the port must copy the footer's plain dwords, including two's-complement negative values, without applying the native memory-cookie transform.

Patch-override caveat (re-confirmed)

49 loose script .BIN files in the game root shadow DATA1 copies at runtime and differ slightly in size; two additional root-only engine BINs bring the root total to 51. The disassembler should target the root copies where present. The header format is identical (same magic/layout) so tooling is copy-agnostic.

What's solid vs. what needs Ghidra

Solid (byte-verified, build a loader now):

• 60-byte header, all 13 fields, dword units, section boundaries
• 3 typed pointer tables (0x71 / 0x03 / 0x8F), 1 dword each, 100% pure
• String encoding (XOR-0xFF cp932) + reference mechanism (tag 0x02 + offset)

Needs the VM (Ghidra on AGE.EXE):

• Opcode dispatch — confirm tagged-operand model, enumerate opcodes
• Meaning of F0/F2/F3/F5 flag fields
• Exact operand grammar per instruction (how many dwords each opcode consumes)

Loader — DONE

tools/sys4load.py parses the header, splits the 4 sections, resolves the 3 tables, decodes inline strings, and emits an assembly-ish listing with strings inlined at their 2 <off> refs (opcodes not yet named — code is chunked by the T3 line-index). Importable API (load() → Sys4Script) plus CLI:

sys4load.py <file.BIN>              full listing
sys4load.py <file.BIN> --summary    header + section sizes + table/string counts
sys4load.py <file.BIN> --strings    decoded string pool
sys4load.py <file.BIN> --json       machine-readable structure
sys4load.py <dir> --validate        re-check invariants across a folder

--validate over all 481 DATA1 scripts: 481 parsed clean, 0 failures, 0 impure table tags — the format spec above is fully machine-verified. This listing is the artifact to diff against Ghidra output once the VM dispatch loop is mapped.

Observations surfaced by the listing (leads for the VM work)

• String-display sites look like <opcode> 0x02 <str-off> — e.g. opcodes 0x1A7 and 0x1A5 immediately precede string refs in MENU.BIN. Candidate text/message ops.
• T3 entries are 3-dword records [0x8F, 0x00, value]; T1 labels are [0x71, 0x00, value]. T3 acts as a per-statement line index (editor metadata) — note scene scripts even carry editor annotation strings like "LABEL", "ループ開始" (loop start).
• 0x55 is the most frequent code lead (likely statement/expr separator); 0x09 recurs as an operand-type prefix (register/var reference?).