What was done
Gustavo Canepa runs Claude agents against objdiff and a link check to match PS2 Gran Turismo 4 functions byte for byte, and reuses the work for Tourist Trophy and Gran Turismo 3.
Gustavo Canepa is rebuilding the engine of Gran Turismo 4 (PS2) as C++ that the original compiler turns into the same instructions as the game, with Claude agents doing most of the matching. His README reports 29,428 of 30,962 functions matched, 95.0%, as of October 2026.
How it was done
He first identified the compiler, Sony's ee-gcc 2.96 at -O2. A pilot matched 13 of 20 random functions by hand. After that, Claude agents drive the project's tools, and every match is checked by the compiler and a judge script, not by eye. About 14% of functions are exact copies of another, so one match settles a group. The same tools were reused for Tourist Trophy and Gran Turismo 3.
Results
The README says 82.8% of the code bytes match, and the full build still reproduces the original executable. 84.9% of the function sources are free of decompiler macros and raw casts. The repository holds no game data, and the work is in progress.