A One-Shot 39,000-Line C to Three.js Port Put Qwen 3.8 27B Against Opus 5, and Both Local Runs Came Out Broken
r/LocalLLaMA (409 upvotes, 93 comments)·medium signal
A builder gave three agents one prompt to port a 2.1MB single-file C shooter, roughly 600k tokens, far past any of their context windows, into a single-file HTML/three.js game with no follow-ups. Claude Code on Opus 5 finished in 21 minutes at 1,759 lines and was rated 'okay'; Qwen 3.8 27B in FP8 on vLLM with FP8 KV cache and full 262,144 context on an RTX 6000 Pro 96GB produced 949 lines in 4h18m under the hermes harness and 1,056 lines in 1h40m under codehamr, both rated 'bad.' The author's own read is that the same weights under two very different harnesses failed the same way, so the harness was not the variable, the one-shot prompt was.