Six Years to Decompile Melee. The Last Mile Took Days.

The Last Mile Took Days, Not Years

Decompiling a game is a selection process, simple in principle and extremely difficult in practice: take the binary, rewrite it as source, and see whether the result recompiles to the same bytes, bit for bit, as the original. If it does, the project continues. If not, it collapses. Started in July 2020, Melee's own decompilation crawled for years. By September 7, 2026, it had reached 100 percent decompiled, fully linked. In its final stretch, LLMs entered the picture, and the pace of the work accelerated hugely. Days before the project was declared finished, OpenAI released GPT-6 Astra. The team put it to work, and within days the project was complete. With the same model, they also built a working 120fps Mac port of the game: higher resolution, upscalable textures, finished in about six hours. The reaction was mixed: some called the timing remarkable, others were frustrated that an AI model had touched a project this beloved at all.

A Decade of Running Down Every Instruction

Zelda Reverse Engineering Team volunteers, ZRET, spent close to two years decompiling Ocarina of Time, finishing in November 2021. Majora's Mask reached a full byte-match decompile of its US cartridge in December 2024, though the project lead noted even then that other regional versions and documentation were still a work in progress. Super Mario 64 was fully decompiled and put on GitHub in August 2019. Programmer Ryan Dwyer decompiled Perfect Dark entirely from scratch in 2022. Banjo-Kazooie reached a 100 percent byte-match decompile in August 2024. Paper Mario (N64) reached 100 percent completion of its US version. Every one of these projects runs toward the same single test: does the rebuilt source compile down to the original bytes, or not? If it does, it's done. If it doesn't, it isn't. There is no other criterion: not whether it's fun to play, not whether it's complete in spirit. Nothing else counts: it is complete when it is byte-match, and not before.

What the Work Turns Into

Decompilation is an exit: you leave a closed, compiled system, and re-enter it as open, editable source. Everything that happens downstream (ports, mods, co-op modes) is only possible because the exit was completed.

The Harbour Masters team built their native PC port of Ocarina of Time, Ship of Harkinian, on the decompiled source. Windows got it first, in March 2022; the port now also runs on Linux, macOS, Switch, Wii U, and Android. Later updates added widescreen support, uncapped framerates, save states, and, in 2025, a randomizer mode. I downloaded it myself and played through Ocarina of Time on it. For Majora's Mask, the same team has done the equivalent with 2 Ship 2 Harkinian, which has logged over 150,000 downloads since its 2024 debut.

Developer Eukaryot built Sonic 3 A.I.R. on top of the Sonic Retro community's disassembly of Sonic 3 & Knuckles. Sonic 3 & Knuckles now runs at 60fps, in widescreen, with a mod ecosystem built around it. The sm64coopdx mod takes the Super Mario 64 decompile and turns it into a sixteen-player online co-op game.

The decompile is the exit, not strictly a destination, though the fact that it exists is a destination of sorts. Once open, the game stops being a sealed object of consumption and becomes malleable material instead, and the people doing the building tend to tell the whole process as a heroic legend: games locked up in binary, inaccessible to all but a few, and the decompiler as the one who breaks the lock and opens them back up.

Where the Models Actually Help

Decompilation is, at least in some cases, an especially well-suited task for AI. There is exactly one right answer: either the bytes match, or they don't. There is no partial credit.

Developer Chris Lewis, for example, spent three months hand-decompiling the N64 game Snowboard Kids 2. He got 25 percent of the way through by hand before switching to Claude Opus 4.5, then reached 45 percent in three weeks. His workflow was simple. He'd send Claude a file, ask it to decompile a specific function, then try the code to see if it matched.

Lewis has said that Claude can often match a function in under ten attempts. He also noted that OpenAI's Codex was "disappointing" on this task. Claude Code also did a good job at a from-scratch decompile of the Game Boy Advance game Klonoa: Empire of Dreams. In that case, the AI surfaced a hidden minigame that had been sitting undiscovered in the original 2001 release for 25 years.

However, there is a limit to how far this approach works. Lewis has found that Claude almost immediately gives up on functions longer than 1,000 instructions. One function with only 86 instructions held out for months. An independent benchmark ran Claude Sonnet 4.6 against 60 real decompilation functions and measured an average match rate of 74 percent, with a fifth of the functions failing consistently across every run.

AI suits the task. Solving it is a different matter entirely.

A Line Some of the Scene Won't Cross

Not everyone wants this kind of help. Building a PC port of Donkey Kong 64, the DK64: Recompiled team states explicitly that "no generative AI was used at any point in the process" of its work. One of its developers said a rival, AI-leaning DK64 project was "progressively harder to manage" as it went on. A Mario Kart Wii recompilation, Wiicompiled, drew comments calling it "AI slop" after its creator used AI tooling to help build it. shadPS4, an emulator project holding itself to the same discipline of matching hardware behavior, adopted formal AI-disclosure rules in August 2026. One contributor's AI-assisted bug hunt there generated 15,668 lines of code across 31 phases and fixed nothing: the actual bug was a single pre-existing setting. Under those same disclosure rules, Claude has also been credited with a real fix: a texture bug that left Uncharted: Drake's Fortune Remastered rendering as a gray void.

The ROM Stays Yours to Dump

Nothing in this story crosses the one line the system itself draws. None of these projects distribute any copyrighted asset; the user is expected to supply their own ROM, dumped from a cartridge or disc they already own. Ship of Harkinian's FAQ states this plainly: "We are not distributing any Nintendo owned IP." 2 Ship 2 Harkinian goes a step further and verifies a SHA1 hash against the user's own dump before it will run. Neither project goes any further than that.

Nintendo itself has not done much to blur the line. In 2020, it filed DMCA takedowns against compiled Super Mario 64 PC-port binaries circulating on file-sharing sites. The decompiled source code repository itself, the actual subject of this whole piece, was never touched, and stayed up on GitHub throughout. Nintendo's own enforcement draws the same line every project here already draws: source code on one side, a build that bundles the game's assets on the other. Nothing in this story crosses it.