Hammer Addons

A native add-on framework for CS2 Workshop Tools, with a versioned C SDK and a shared add-on manager. It loads once through Asset Browser and hosts add-ons in the Workshop Tools process.

The framework provides native DLL loading, lifecycle callbacks, logging, interface-request observations, and a manager for viewing add-on status and filtering by supported tool. Use it to install compatible add-ons or build your own against the included SDK.

This is an unofficial project, independent of Valve.

Build

Requires Windows x64, Python 3.11+ and Visual Studio 2022 or 2026 with Desktop development with C++ and CMake tools.

.\build.bat -Test

The first build downloads the matching Qt 5.15.2 development package (33 MiB) from Qt's official archive, verifies its pinned SHA256, and caches it under build/deps. Later builds use the cache. The distribution contains our assetbrowser.dll proxy, UI DLL, standalone host, SDK and hello sample. It uses Workshop Tools' existing Qt runtime; no Qt DLLs are installed. Tests use fixture DLLs and temporary folders, so CS2 is not required.

Related MCP server: Roblox AI Agents

Install into Workshop Tools

Close CS2 and Workshop Tools, then substitute your Steam installation path:

python scripts/loader.py inspect --cs2 "E:\SteamLibrary\steamapps\common\Counter-Strike Global Offensive"
python scripts/loader.py install --cs2 "E:\SteamLibrary\steamapps\common\Counter-Strike Global Offensive" --apply

Omit --apply to preview. The installer checks the supported Asset Browser binary, backs it up byte-for-byte, then installs the proxy. Start Workshop Tools normally: the Workshop Add-ons panel appears in the Asset Browser. In Hammer, open it through Help > Workshop Add-ons > Show add-ons.

The panel shows Loader active, loaded/disabled/failed counts, and each add-on's version and status. Dock, float or close each panel independently. In Asset Browser, use Workshop Add-ons > Show add-ons to reopen it. In Hammer, the menu lives under Help, with no extra top-level menu or automatically opened dock. Both menus also offer About Hammer Addons, which opens the About tab with the framework version and project link. Open add-ons folder opens your installed add-ons.

The Tool filter and Tools column distinguish Asset Browser, Hammer, ModelDoc / Model Viewer, Material Editor and Particle Editor add-ons. Hammer defaults to its own filter. Counts reflect the displayed list; changing a filter does not load or unload DLLs.

game/bin/win64/
  assetbrowser.dll                 Framework entry point
  assetbrowser_original.dll        Verified original Valve DLL
  tools/
    hammer.dll                     Original Valve Hammer
    hammer-addons/
      install.json                 Module and ownership hashes
      loader.log
      hammer_addons_ui.dll         Shared add-on manager
      addons/hello/
        addon.ini
        hello.dll

Each add-on has its own folder under tools/hammer-addons/addons/. Drop compatible add-ons there and restart Workshop Tools. Set enabled=false in a manifest to disable one add-on, or create tools/hammer-addons/disabled to disable all add-ons while keeping original tools forwarding and the manager. Native add-ons run with Workshop Tools' permissions; they are not sandboxed.

Upgrading an earlier Hammer-only installation

Run the current uninstaller first, then install again. It recognizes old installation records, restores the original Hammer DLL, and preserves add-on folders. The new installation starts from Asset Browser. Only one loader entry point should be installed at a time.

python scripts/loader.py uninstall --cs2 "E:\SteamLibrary\steamapps\common\Counter-Strike Global Offensive" --apply
python scripts/loader.py install --cs2 "E:\SteamLibrary\steamapps\common\Counter-Strike Global Offensive" --apply

The installer preserves differing existing add-on files by refusing to overwrite them. To keep a customized sample during an update, omit its folder from your new distribution before installing.

Uninstall verifies hashes, restores the recorded original module, removes an unchanged framework UI DLL, and preserves add-ons. After a Steam update, inspect again. The tool refuses to overwrite a new Valve DLL with an older backup. Only module-specific builds in compatibility.json are accepted.

Write an add-on

python scripts/new-addon.py my_addon --output ../my_addon --tools hammer,modeldoc
cmake -S ../my_addon -B ../my_addon/build -A x64 -DHAMMER_ADDONS_SDK="$PWD/sdk"
cmake --build ../my_addon/build --config Release
cmake --install ../my_addon/build --config Release --prefix ../my_addon/package

Copy package/my_addon/ into the loader's addons/ directory. See the format and API contract, sample and C header. ABI 1 add-ons remain compatible; add an optional tools=asset_browser,hammer manifest field to declare supported tools, or tools=all for a general add-on. Untagged older add-ons appear as Unspecified. These tags describe intended tools for discovery; they do not assert that an editor is open or delay DLL startup. The Asset Browser entry point emits tools.factory.request observations.

Current capabilities and limitations

The manager is available in Asset Browser and through Hammer's Help menu. Tool tags identify an add-on's intended use; they do not provide editor APIs or imply that an integration exists for every listed tool.

The SDK currently exposes logging and factory-request observations. Document editing APIs, add-on-owned panels, command registration and hot reload are not implemented. Add-on changes require restarting Workshop Tools.

See the API contract for callback and threading rules, architecture for implementation details, and validation for tested builds and behavior.