Telltale Modding Studio

A modern desktop app for modding Telltale games: browse the contents of .ttarch / .ttarch2 archives, extract just the assets you want, swap in replacements (character models, textures, animations…), and build a minimal patch archive the game loads over its originals — no full rebuild needed.

Built on ttarchext by Luigi Auriemma, which does the actual byte-level extraction/rebuilding (for learning purposes only). This project wraps it in a workflow that makes asset swapping practical.

How the swap workflow works

1. Pick your game — this selects the per-game encryption key ttarchext uses.
2. Open an archive — the app sniffs the header (ECTT/ZCTT/NCTT/3ATT vs classic version numbers) and auto-detects the right format version, then lists the contents without extracting anything.
3. Find your asset — filter by name or category (Model, Skeleton, Animation, Texture, …) and extract just that file if you want to inspect or edit it.
4. Add swaps — point each target asset at your replacement file. Save the whole set as a .ttmod project you can reopen later.
5. Build patch — the app stages only your swapped files and builds a tiny 0.ttarch / 0.ttarch2. Drop it in the game's archive folder; the game reads it as a patch that overrides the originals.

Plus: in-app DDS texture preview (DXT1/3/5 and 32-bit RGBA) so you can eyeball a texture before you ship it.

Repository layout

Path	What it is
src/TelltaleModding.Core	Cross-platform .NET 8 library: game database, archive header detection, async ttarchext wrapper, listing parser, mod-project model, minimal-patch builder, DDS decoder
src/TelltaleModding.App	Avalonia 11 desktop UI (MVVM)
tests/TelltaleModding.Core.Tests	xUnit suite, including detection against real sample archives
engine/ttarchext	The ttarchext CLI (source + Windows exe) — the extraction/build engine
samples/	Real .ttarch2 archives used by the tests
legacy/winforms	The original WinForms GUI, kept for reference

Building

dotnet build TelltaleModding.sln
dotnet test                      # runs the Core test suite (works on any OS)
dotnet run --project src/TelltaleModding.App

Everything builds and runs cross-platform. The engine comes in two flavours:

• ttarchext.exe (shipped) — the Windows binary. Required for Oodle-compressed archives (lowercase zCTT/eCTT tags), because Oodle decompression works by loading the game's own oo2core DLL.
• Native build — make -C engine/ttarchext (needs zlib1g-dev) produces a Linux/macOS ttarchext that handles encrypted, zlib-compressed, and plain archives. This repo carries a small portability fix for it (the original Blowfish code assumed 32-bit unsigned long).

The app picks whichever flavour runs on your OS automatically, or you can point the TTARCHEXT_PATH environment variable at a specific binary. When only the .exe is present on a non-Windows host, engine actions are disabled with an explanatory status message.

With a native engine present, dotnet test also runs end-to-end integration tests: listing and extracting from the real sample archives and round-tripping a built patch. CI does this on every push.

Notes

• Don't enable the "-m" meta decode option for files you plan to rebuild into a patch — decoded DDS/OGG files are not valid archive members.
• If the game crashes loading a rebuilt v7+ archive, rebuild with ttarchext's compatibility mode (-x).
• ttarchext is © Luigi Auriemma, GPL-2.0. Game archives and their contents belong to their respective owners; mod responsibly.