What they did
The poster, u/BeginningRealistic49, wanted 3D on two Nintendo 3DS games that never shipped with it: Minecraft and Terraria. Claude Code worked from the raw machine code alone, with no source, spending hours in disassembly. The run used Opus 5.5 at medium effort as an orchestrator directing Sonnet subagents. For Minecraft, it found that the first release carried a 3D renderer that was turned off after the first frame and later removed, recovered it from that old build and rebuilt 3D for the current version. Terraria had no 3D path at all, so it worked out which draw layer was which and gave each layer its own depth.
How it went
Both mods work and are published as open source on GitHub, and the poster says they hold close to the games' original performance targets. Terraria's mod even runs on the original 3DS with its smaller memory. The poster's own role was mostly testing on the console and reporting crashes; builds that ran in the emulator often crashed on real hardware. They also posted a video of the whole process.
Worth knowing
Usage would have cost about $670 at API prices for both mods; the poster ran it on the $100 Max plan. Expect the emulator to hide crashes, so test on real hardware. The poster notes the demo animations simplify the real layering. The thread had only a handful of comments, so there is no outside confirmation yet.