Portalcraft (Minecraft in Portal 2)

Portalcraft runs the real Portal 2 and a hidden Minecraft: Java Edition 26.3 side by side. Portal 2 draws everything and runs its own puzzles, while Minecraft supplies the player, hand, hotbar, health and blocks. Mining into a chamber wall reveals Minecraft ground behind it, and holding G while Chell fires a portal opens its partner onto a Minecraft landscape generated from your own seed. J switches between the Minecraft player and Chell.

A bundled launcher finds Portal 2 in your Steam libraries and sets up a portable Prism Launcher profile with Fabric and the Portalcraft mod. You sign in with your own Microsoft account, and the launcher downloads Minecraft and Java. The Portal 2 plugin goes into the launcher's own folder, and nothing is added to your Portal 2 install.

The author describes it as early, experimental and still quite broken. The Minecraft world shows visual artifacts (smearing, stretched edges) on all builds. On Linux it needs the normal Steam package (Flatpak Steam can't load the plugin yet) and the native Linux version of Portal 2, not Proton. It builds on the SkyCraft idea and the SourceAutoRecord plugin framework.