Decompilation toolchain

Question

What tool turns Source 2 compiled resources (*_c) into readable data, and what is the exact invocation for the files we care about?

Summary

• ValveResourceFormat (VRF / Source 2 Viewer) is the tool. Open source, actively maintained, explicitly supports Deadlock. Version 19.2 was used here.
• Use the CLI (cli-windows-x64.zip and equivalents), not the GUI, for anything repeatable.
• Extracting + decompiling all 77 scripts/*.vdata_c takes seconds and produces readable KV3 text.
• VRF is not vendored in this repo — it is a 48 MB download and its own project. tools/vendor/ is gitignored for this purpose.
• Reading the VPK index needs no tooling at all — tools/vpk_list.py is stdlib Python.

Findings

Obtaining the CLI

Release assets at https://github.com/ValveResourceFormat/ValveResourceFormat/releases/latest:

Unzipping cli-windows-x64.zip gives Source2Viewer-CLI.exe plus four native dependencies (libSkiaSharp.dll, spirv-cross.dll, TinyEXRNative.dll, blake3_dotnet.dll). Keep them together.

The .nupkg is the library — relevant if we ever want to call VRF in-process from C# instead of shelling out.

Flags that matter

Verified invocation

Source2Viewer-CLI.exe \
  -i "<game>/citadel/pak01_dir.vpk" \
  -o out \
  -f "scripts/" -e "vdata_c" -d --threads 4

Produces out/scripts/*.vdata as KV3 text. Sizes at build 6679:

Output begins with a KV3 header line naming the encoding and format GUIDs:

<!-- kv3 encoding:text:version{e21c7f3c-8a33-41c5-9977-a76d3a32aa0d} format:generic:version{7412167c-06e9-4698-aff2-e63eb59037e7} -->

Reproduce

# 1. Fetch the CLI into the gitignored vendor dir (adjust asset for your OS)
mkdir -p tools/vendor
curl -L -o tools/vendor/cli.zip \
  https://github.com/ValveResourceFormat/ValveResourceFormat/releases/download/19.2/cli-windows-x64.zip
unzip -o tools/vendor/cli.zip -d tools/vendor/vrf

# 2. Confirm the install and build stamp
python tools/find_game.py

# 3. Extract + decompile gameplay data
tools/vendor/vrf/Source2Viewer-CLI.exe \
  -i "$(python tools/find_game.py --json | python -c 'import json,sys;print(json.load(sys.stdin)["game_dir"])')/citadel/pak01_dir.vpk" \
  -o out -f "scripts/" -e "vdata_c" -d --threads 4

# 4. Sanity check
ls -la out/scripts/heroes.vdata out/scripts/abilities.vdata
head -3 out/scripts/heroes.vdata

On Windows PowerShell, invoke the exe with & and quote the path.

Gotchas

• Pin the VRF version in notes. VRF output format has changed across major versions; a note that does not say which version produced its output is hard to re-verify.
• out/ is gitignored — decompiled game data must not be committed.
• The GUI and CLI are separate downloads. The GUI is fine for exploration but useless for a reproducible pipeline.
• -e vdata_c is the compiled extension, but the output files are .vdata (no _c). Filters apply to input names, not output names.
• Texture extraction is a different order of magnitude. .vtex_c is 24 GB packed; do not run an unfiltered extract casually.
• VRF is third-party. It can lag a Deadlock patch that changes a format. If decompilation suddenly fails after a patch, check for a VRF release before assuming the game changed something fundamental.

Open questions

• Not tested: --vpk_cache behaviour across an actual game patch.
• Not tested: the .nupkg library path (in-process C# usage).
• Not tested: --vpk_verify on this install.
• Not tested: whether VRF resolves KV3 _multibase inheritance in any mode. Observed output suggests it does not, but no flag was searched for specifically.
• Not tested: .vtex_c → PNG for item/hero icons.

Sources

• ValveResourceFormat on GitHub
• Source 2 Viewer — Valve Developer Community