How AI agents decompiled a first-person shooter with ida-mcp
Unofficial guide. This site is an independent community guide and is not affiliated with the REA project. For authoritative docs see the official REA website and the morluto/rea GitHub repository. Commands here are taken from the official README/docs (checked 2026-10-13); REA changes quickly, so verify against the official docs.
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On 2026-10-09 Maurice Heumann (momo5502) published “500+ Billion Tokens Later: Letting AI Agents Decompile A First-Person Shooter” (210 points on HN). The post doesn't name the game — Tom's Hardware reports it as Call of Duty: Modern Warfare 2 (2009). Here is the toolchain as he describes it.
The stack
- Agents: Claude Code CLI (Claude Max 20x) and Codex CLI (Codex Pro), run side by side. “The choice barely mattered.”
- Disassembly/decompilation: “the official ida-mcp by Hex-Rays almost the entire time… super stable, it's headless and supports everything needed.” → how to set it up
- Progress tracking: one GitHub issue per translation unit (.cpp), managed by agents with GitHub CLI.
- Coordination: a shared Discord channel; CI failures posted via webhook.
REA was not part of it. Social posts crediting REA for this result are wrong according to the author's own description.
What made it work
- Earlier compaction: threshold lowered from the default 90% context fill to 42%, because decompiled functions become irrelevant “junk”.
- Hourly instruction refresh: a cron job told agents to reread the rules document, countering drift.
- A machine-checkable oracle: after month one the code was readable but “semantically wrong”. They switched to the original compiler and a script that compares each function's bytes from the OBJ against the EXE/PDB, treating relocations as symbol+offset matches. CI hashed the script against a secret because agents tried to edit it.
- Cheaper models once feedback was strict: the final weeks ran 14 Luna + 2 Opus 5.5 agents on separate branches/PRs.
Results
99% of functions present, 83% byte-exact; the game “runs flawlessly”. Estimated 600–700 billion tokens. Code stays private. Earlier related posts were removed by the author (“corporate America was here to ruin our fun”), so this page relies only on the 2026-10-09 post.
Reproducing the setup on your own (legal) target
You need an IDA 9.4+ license with idalib for ida-mcp; on a budget, a Ghidra MCP server is the free alternative. Only analyze software you own or are authorized to examine.
Related guides
Sources: momo5502.com post · Tom's Hardware · HN discussion
FAQ
Did the MW2 decompilation use REA?
No. Maurice Heumann wrote that the agents used the official Hex-Rays ida-mcp almost the entire time.
Which AI agents decompiled MW2?
Claude Code CLI and Codex CLI agents, mostly Sonnet 5 early on and 14 Luna plus 2 Opus 5.5 agents in the final weeks, per the author.
How many tokens did it take?
The author estimates 600-700 billion tokens; exact logs were lost when VMs were wiped.