What they did
The poster set out to remaster Rainbow Six Vegas 2, a 2007 shooter built on Unreal Engine 3. Years earlier they had spent weeks with GPT-4 building a rough map exporter for the old game files. When newer OpenAI models arrived they returned to it, first polishing the exporter and then, with the Astra model in Codex, porting the entire game into Unreal Engine 5. They work on it in spare moments during the day from their phone. They ran the heavier model for complicated pieces and a cheaper model for quick fixes, and are now importing the maps from the first Vegas game as well.
How it went
The poster says the port works and feels almost identical to the original, and shared a side-by-side screenshot of the old and new versions. The project is still in progress: the working folder had reached about 90 GB, with a built game of about 1.7 GB. They offered playable builds to commenters and say they have videos showing it running. Online play is a goal, not done yet. They found the cheaper model poor for this project and the heavier one worth its cost.
Worth knowing
A commenter doubted it could be done without the biggest plan, since a project this size burns through usage limits fast. The poster leaned on the plan's usage resets to keep going. The game's assets belong to its publisher, so a port like this is a personal project, not something to distribute.