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Installing the Half-Life Unified SDK mod places a ready-to-run hlu directory inside your Half-Life game folder and copies, converts, and upgrades all required campaign maps from Half-Life, Opposing Force, and Blue Shift. The process takes about ten minutes and requires a working Steam installation of Half-Life (plus Opposing Force and Blue Shift if you want their campaign content).
The current release is a pre-alpha build. Pre-alpha builds are work-in-progress and are likely to be unstable and buggy. They are intended for testing individual features, not for general play or as a mod development base.

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Installation Steps

1

Download the latest release

Download the latest mod archive from the Releases page on GitHub.
2

Extract to your Half-Life directory

Extract the archive into your Half-Life game directory (e.g. C:\Program Files (x86)\Steam\steamapps\common\Half-Life). The archive will create an hlu subdirectory inside the Half-Life folder automatically.
3

Install the Visual Studio 2022 redistributable

Run the Visual Studio 2022 C++ redistributable installer found in the hlu/redist directory. This provides the runtime libraries required by the mod’s game DLLs.
4

Install the .NET 6 SDK

Install the .NET 6 SDK. Make sure to install the latest version, as the runtime receives regular updates. The .NET SDK is required to run the ContentInstaller tool in the next step.
5

Switch Half-Life to the steam_legacy branch

The Unified SDK requires the steam_legacy version of Half-Life and has not yet been updated for the anniversary edition. In Steam, right-click Half-Life → Properties → Betas and select steam_legacy from the dropdown.
You only need to remain on steam_legacy during the installation step. Once the ContentInstaller has finished you can switch Half-Life back to the default (anniversary) branch.
6

Run the ContentInstaller

Open a command prompt, change to your Half-Life directory, and run the ContentInstaller tool:
cd "C:\Program Files (x86)\Steam\steamapps\common\Half-Life"
dotnet "hlu/tools/ContentInstaller.dll" --mod-directory hlu
The tool will copy, convert, and upgrade maps from Half-Life, Opposing Force, and Blue Shift into the mod directory. This may take several minutes on the first run.
7

Restart Steam

Restart Steam so that the hlu mod is detected and added to your games list.

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Running the Game

Once installed you can launch the mod in either of two ways:
  • Via Steam — find Half-Life Unified SDK in your Steam library and click Play.
  • Via launch parameter — launch Half-Life with the command-line argument -game hlu.
While playing you may see a project info overlay displayed on-screen. This overlay is used for in-game diagnostics and shows the current build’s release type and version. See the Hud Project Info documentation for more details.

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Pre-Alpha Builds

In addition to tagged releases, automated pre-alpha builds are produced for every successful CI run.
Pre-alpha builds can be downloaded from the Artifacts section of each run on the GitHub Actions page. Artifacts are retained for up to 90 days after the run finishes. After that window the artifact is no longer available.
Pre-alpha builds are work-in-progress builds that are likely to be unstable and buggy. Use them only for testing specific features, not as a stable playing or development base.

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