Aura
Aura is a codebase framework for Multiplayer games on the GoldSrc engine, created by The Phoenix Project Software. It is the successor to Grey Source and debuted in 2021 with the release of Half-Life: Cross Product Multiplayer version 2.4.
It is a heavily modified fork of Adrenaline Gamer and uses OpenAG for the clientside library.
Features & technologies
Though it has a lot of inherited features from Adrenaline Gamer, Aura introduces many features of its own to make the games using it unique.
Shield system
For Cross Product Multiplayer, Half-Life's damage system was overhauled and replaced with regenerating HEV suit armor, known as shield regeneration.
Expanded gametypes
Expanding upon the features from AG, Aura adds a "HLDM" and "SWAT" gametype.
Music Playback System
Aura uses GoldSrc's built-in MP3 playback system and adapts it for multiplayer in certain gametypes.
Expanded weapons
With more to come, Aura backports the weapons from Half-Life: Opposing Force.
Source SDK & Steamworks integration
Aura's clientside binary leverages an adapted version of the Source 2013 libraries - VGUI2, Tier1, and Tier2. It also uses the Steamworks API. This allows for the following features:
- Steam Workshop
- New Server Browser
- Smooth viewbobbing
- Steam Input features (lightbar, vibration)
- Steam Achievements
- Steam Stats
Aura SDK
To benefit creators and authors, particularly for the Steam Workshop, The Phoenix Project Software released the Aura SDK on Steam in 2025. It is a comprehensive set of tools, source files, and resources, aimed to help enable the creation of custom content.
It also comes with a set of Tools to help authors get started quickly, some created by TPPS, and some which are forks of other community-made tools as per their license:
- Harbinger - Steam Workshop publishing tool for Cross Product Multiplayer
- Helix - a fork of Half-Life Asset Manager
- Sapien - a fork of newbspguy
- Spectra - used for converting images to TGA for VGUI panels
- Tessera - a fork of Half-Life Texture Tools
The Phoenix Project Software has plans to expand the forks with features of their own to compliment Cross Product Multiplayer, but for now has distributed them per their licenses for convenience.