Bethesda BA2 Binary Header (BTDX)

Offset 0x00 - 0x18

Bethesda Archive 2 (BA2) files begin with a strict 24-byte header. Any non-BTDX magic signature causes instant engine load rejections.

Offset	Type	Field Name	FO76 Vanilla Value	Description
0x00 (0)	uint32 LE	Magic Signature	0x58445442 ("BTDX")	Fixed Bethesda identifier. Must match exactly.
0x04 (4)	uint32 LE	Version	0x00000001 (1)	Version 1 is mandatory for FO76. Next-Gen (v7/v8) crashes FO76.
0x08 (8)	uint32 LE	Archive Subtype	GNRL or DX10	0x4C524E47 (GNRL) or 0x30315844 (DX10 textures).
0x0C (12)	uint32 LE	File Count	Varies	Total number of file records packed inside the archive.
0x10 (16)	uint64 LE	Name Table Offset	Offset (bytes)	Byte pointer to raw filename strings table.

Fallout 4 Next-Gen Downgrade Rule (April 2024+) Zero-Data-Loss

Fallout 4 Next-Gen update (CK v1.10.943) introduced version 7 and 8 BA2s. The internal compression and chunk structure remain identical to version 1. To use Next-Gen archives in Fallout 76, patch byte offset 4 to uint32 1:

python3 -c "import sys; f=open(sys.argv[1],'r+b'); f.seek(4); f.write(b'\x01\x00\x00\x00'); f.close()" target.ba2

NIF Mesh Header

BS v155 / Gamebryo

1. ASCII Magic String: Gamebryo File Format, Version 20.2.0.7\n Read sequentially from offset 0x00 to newline (0x0A).

2. Binary Header Fields:

Version Bin: 0x14020007 (uint32 LE)
Endianness: 0x01 (Little-Endian)
User Version: 131 (Creation Engine)
BS Version: 155 (Fallout 76 Mesh)

DDS 128-Byte Reconstruction:

DX10 texture entries do not store raw headers. Devs must prepend a 128-byte DDS header (Magic 0x20534444, Size 124, Flags 0x00021007) before piping chunks.

Launch In-Browser BA2 Inspector

Scaleform GFx 4.x ActionScript 3 Invariants

AVM2 Bytecode

Fallout 76 executes on Autodesk Scaleform GFx 4.x. UI screens (PipboyMenu.swf, HUDMenu.swf) run in a modified ActionScript 3 virtual machine. Violating garbage collection or bytecode limits causes main-thread micro-stutters and CTDs.

SWF Version Byte Rule (13 vs 43)

Vanilla F76 SWFs use version 13 (Flash 11) or 43 (Flash 32). The AVM2 bytecode structure is identical. When recompiling in JPEXS, target SWF Version 13 to prevent injecting modern stage commands unsupported by GFx.

60 FPS & GPU Blit Flags

Vanilla UI files are often locked to 24 or 30 FPS. Patching the header frame rate to 60 FPS and enabling UseDirectBlit / UseGPU=true forces hardware acceleration pathways in the Creation Engine compositor.

Zero-GC Vectorization

Scaleform's MMgc garbage collector is aggressive. Never pass arrays of dynamic Object from C++ to AS3. Always serialize into primitive typed vectors: Vector.<int>, Vector.<Number>.

Native JSON Mandate

Always use built-in JSON.parse() (~0.05ms, 0B GC). Avoid pure-AS3 binary deserializers (as3-msgpack, as3pb) which trigger 1.4–4.2ms CPU spikes during fast weapon switches.

JPEXS Free Flash Decompiler (FFDec) CLI Automation

1. Export AS3 Scripts from Vanilla SWF:

java -jar ffdec.jar -format script:as3 -export script ./src/ HUDMenu.swf

2. Inject Modified AS3 Scripts into New SWF:

java -jar ffdec.jar -importScript HUDMenu.swf HUDMenu_modded.swf ./src/

3. Replace Sprite / Icon via Character ID (Lossless PNG):

java -jar ffdec.jar -replace HUDMenu.swf HUDMenu_modded.swf 142 custom_icon.png

Engine Interface

BGSExternalInterface

The Creation Engine communicates with UI layers via synchronous BGSExternalInterface calls. Custom listeners must match exact vanilla parameter types:

public function onDataUpdate(
  ids:Vector.<int>, 
  counts:Vector.<int>
):void {
  // Process zero-alloc vector
}

Persistent UI Daemon:

Dynamic UI screens (Pip-Boy, Trade) are destroyed and garbage-collected upon cell transition. Only overlay.swf persists continuously. Anchor cross-scene IPC bridges here.

Launch F76+ Configuration Studio

fo76-dumps Data Mining Orchestration

xEdit & SQLite

The fo76-dumps pipeline automates extraction of records, form IDs, crafting recipes, weapon curves, and vendor catalogs directly from Bethesda ESM files into high-performance SQLite databases.

Extraction & Compilation Workflow

1. Environment Initialization (uv / Python 3.12+):

git clone https://github.com/fwdekker/fo76-dumps.git && cd fo76-dumps && uv sync

2. Configure Game Root & Tools in config_local.py:

game_root = "/mnt/steam/steamapps/common/Fallout76"
xedit_path = "/usr/local/bin/fo76edit.exe"
ba2extract_path = "/usr/local/bin/ba2extract.exe"
dump_root = "./dumps/"

3. Execute Orchestrator:

uv run fo76dumps.py

Output Target	Format	Description
tabular.*.csv	CSV	Structured tables of weapon damage curves, armor ratings, and quest rewards.
fo76.sqlite	SQLite 3	Master relational database indexed for instant SQL querying.
wiki.*.wiki	MediaWiki	Pre-formatted wikitext tables ready for Fandom/wiki community publication.

PTS Diff Watcher

Systemd Timer

Monitor Bethesda PTS releases and auto-diff new database records. Install a daily user timer on Linux:

~/.config/systemd/user/fo76-watcher.timer

[Unit]
Description=Daily FO76 PTS Diff Watcher
[Timer]
OnCalendar=daily
Persistent=true
[Install]
WantedBy=timers.target

Activation Command: systemctl --user daemon-reload && systemctl --user enable --now fo76-watcher.timer

Explore Atomic Datamines

Creation Engine DXGI Hooks & IPC Architecture

Project+ Spec

The Project+ architecture decouples UI rendering from heavy engine logic using DLL search order hijacking, Direct3D 12 barrier transitions, and sub-microsecond memory-mapped IPC.

DXGI Present Hooking

Proxy dxgi.dll hooks IDXGISwapChain::Present. On DirectX 12, back-buffers must transition from D3D12_RESOURCE_STATE_PRESENT to RENDER_TARGET before drawing ImGui overlays.

64-Byte Cache Aligned IPC

Inter-process communication uses Memory-Mapped Files (MMF) aligned to 64-byte CPU cache boundaries with Single-Producer Multi-Consumer (SPMC) ring buffers and lock-free CAS operations.

RFC 6455 AS3 WebSocket Framing

Connects AS3 directly to 127.0.0.1 via raw flash.net.Socket in Little-Endian. Performs 4-byte XOR client-to-server masking, Ping/Pong heartbeats, and frame-sliced rendering.

Request Smuggling Defenses

Strict regex stripping (/[\r\n\x00]/g) on all URLRequest headers to prevent CRLF injection, CL.TE desync, and socket buffer poisoning across reverse proxy chains.

Universal .NET 10 Native AOT Smart-Hub Daemon:

The background daemon compiles to Native AOT (<PublishAot>true</PublishAot>) for <10ms startup times, zero runtime dependencies, and seamless execution across Windows, Linux, and Steam Deck (SteamOS).

Economy Math

Fixed Formulas

Minerva's 25% Discount Formula: discounted = Math.ceil(original * 0.75) Fallout 76 game engine pricing rule.

Reversing Discount Invariant:

DO NOT multiply by 1.333 or 1.333333 (induces off-by-one errors like 251 instead of 250). ALWAYS use:

original = Math.floor(discounted / 0.75)

Minerva Schedule Pipeline:

NukaKnights data provides 24 pre-merged lists. Never apply dynamic Big Sale concatenation, or inventory sizes will duplicate. Pipe the 24 lists 1:1.

View Live Minerva Radar

CREATION ENGINE MODDING DEVHUB