Claude AI helped a fan fix Oblivion Remastered’s worst performance flaws — and the results are real: +41% average FPS in Imperial City at 4K, 1% lows up from 33 to 45, and traversal hitches cut by 75%. No visual trade-offs. No official patch. Just one Reddit user, LTSharpe, and Claude Opus 5.5. The mod is live as v1.0.0 beta, open source, installable in minutes, and already running on Radeon RX 9070 XT and Ryzen 7 5800X hardware. It’s not a graphics tweak. It’s engine surgery: multithreading fixes, memory allocation overhauls, and frame-distributed world streaming. All reverse-engineered and optimized without professional dev experience. The bottleneck wasn’t GPU drivers or ray tracing. It was the game rebuilding sun/moon lighting every frame, cramming DirectX 12 command prep into one thread, and stalling entire frames on world-streaming calls. Claude spotted it. LTSharpe implemented it. Benchmarks show gains even without FSR Frame Generation, 1% lows jump from 26 to 43 FPS in Cheydinhal. Proving this isn’t just a frame-gen crutch. The mod also adds AMD FSR 3.1.4 Frame Generation support for RX 9000 GPUs, fixes crashes, speeds up menus, and eases loading stutters. But it’s still beta. Tested on one high-end CPU/GPU combo. No word yet on Intel CPUs, NVIDIA RTX 50-series compatibility, or how it behaves on 16GB RAM systems. Anthropic hasn’t endorsed it. Bethesda hasn’t acknowledged it. And the mod doesn’t change textures, models, or Nanite, those stay untouched. What it does is sharpen what’s already there. And that matters now: Oblivion Remastered launched with widely reported CPU bottlenecks, especially on NVIDIA hardware. This mod doesn’t wait for a patch. It ships today. Source code and reproducible benchmark tools are on GitHub. Installation is manual: extract files into the game directory. No installer. No telemetry. No paywall. Next? Community testing across more configs. And whether other remasters, or even unpatched legacy titles, become the next target for AI-assisted optimization.