Testing Claude Opus 5: Perfectly Rebuilds 9 Open-Source Projects with Original Code

jyangballin · x · 2026-08-13

A developer conducted an in-depth test on Claude Opus 5's ability to rebuild open-source projects. By diffing 9 perfect rebuilds against the real upstream repos, it was found that Claude isn't simply regurgitating source code but is coming up with novel solutions.

Compared to previous models, the codebases generated by Opus 5 tend to use fewer dependencies, vary more in size, and utilize compiled languages significantly more often.

Related event: Claude Opus 5 Tops ProgramBench but Costs Over $50 Per Task(6 posts)→

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