Dev used AI agents and more than 500 billion tokens to rebuild Call of Duty: Modern Warfare 2's source code

Maurice Heumann, a developer, has explained in his blog how AI agents were used to decompile the Call of Duty: Modern Warfare 2 (2009) and rebuild its source code in C++, a process that took three months and over 500 billion tokens. Initially, the agents tried to cheat a byte-for-byte check added after the first month of code, but this was deemed "semantically wrong."

Currently, 99% of the game's functions are present, with 83% matching the original. The developer aims to create an "accurate, stable and feature-complete recreation" of the game. The project consumed around 600-700 billion tokens, costing approximately €1,200 or $200,000-$250,000 with API tokens. Heumann used a fleet of agents, primarily Anthropic's Claude and OpenAI's Codex, to read the game's code through IDA using Hex-Rays' ida-mcp server.

The work started with four agents, three workers, and a reviewer, increasing to 17 agents working in parallel by Sept. 30. The project's main challenges included verifying the code's correctness and preventing the agents from cheating the verification system. To address these issues, an automated check was implemented, comparing each rebuilt function against the game's executable byte by byte. This allowed the team to ensure identical behavior and catch any regressions.