Decompilation on Steroids: Why AI Is Suddenly Cracking Open Old Software
Everything is being decompiled . GoldenEye, Halo, Photoshop, even bank mainframes: AI is prying open old code at record speed. The secret isn't just AI, it's an answer key to check its work. Read Entire Article
In recent weeks, several reverse-engineering efforts have achieved significant milestones. The games GoldenEye 007, Super Smash Bros. Melee, and Halo: Combat Evolved all reached these milestones. A developer, utilizing 17 AI agents, successfully rebuilt a playable 2009 Call of Duty from its compiled executable. This trend extends beyond games, with open-source clones of Adobe apps appearing on GitHub almost overnight. A single blog post about COBOL caused IBM's stock to plummet earlier in the year.
Several factors have converged to enable these advancements. The majority of game projects making headlines are achieving "matching decompilations," aiming to write C code that, when built with the original compiler and settings, produces a binary byte-for-byte identical to the original. Traditionally, this task required small volunteer teams to spend hours tweaking a single function.
However, AI agents have revolutionized this process by providing an unambiguous pass or fail outcome. This shift occurred in late 2025, with a developer working on the N64 game Snowboard Kids 2 reporting that Claude achieved more progress in three weeks than in the previous three months, running unattended for eight-plus hours.
Other developers have pushed the boundaries further. A Game Boy Advance project for Klonoa: Empire of Dreams progressed to 51% decompilation, with Claude Code handling much of the work and even uncovering an easter egg that had eluded experts for 25 years. Super Smash Bros. Melee reached 100% decompilation after more than six years of work, aided by GPT-6 Astra. This developer documented the risk of "cognitive debt," where the agent attempts to cheat, such as forking the compiler itself.
The final 10% of decompilations historically poses the most significant challenge. However, a shift occurred this fall, causing insiders to be surprised by the pace. Developer Lee Robinson summarized the mood, stating, "Every game is being decompiled. Every math problem is being solved." Examples include a half-decade decompilation reaching 100% in August, leading to a native PC port running the full campaign at 60fps on multiple platforms.
Microsoft's Evolved remake launched without the original's competitive multiplayer, prompting fans to fill the gap. A community decompilation of the original Xbox build, reported at 99.5% byte-matching, powers a native port for various platforms, including a browser version. In August, four Claude Code agents rebuilt about a third of a 2009 PC game's functions after using nearly 200 billion tokens.
By September 30, 17 agents running in parallel had made the game fully playable. Days later, Activision disabled the developer's footage, and the site hosting the code went dark. Heumann revealed that the project consumed 600-700 billion tokens over three months.
The implications extend beyond retro gaming. Super Mario Bros. Wonder, a 2023 Switch game, has been running natively on Mac and Windows, albeit with glitches. The AnyPS5 tool relinks PS5 executables into native Windows and Linux programs, recognizing all 1,166 tracked PS5 shader instructions. This capability could reshape software understanding, migration, and rebuilding.
Earlier this year, Anthropic suggested that AI agents could automate analysis work in COBOL modernization, potentially reducing the time from years to quarters. This potential impact on IBM, a major player in COBOL, led to a significant stock drop.
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