Vibe-coded a CAD app in 72 hours with Opus: hand-estimate was 2 years, Opus said 8-12

Maleficent-Release61 · reddit · 2026-09-28

A developer built a Solidworks-like CAD application from scratch in 72 hours using Opus 5.5 (Medium Effort, High Effort for hard bugs), with no external dependencies — the model chose to write the CAD kernel in JavaScript. He spent 50% of his weekly usage limit, steered with a few prompts and hand-fed bugs. He estimates manual implementation would take 2 years; Opus itself estimated 8-12. Next steps: a multithreaded Rust kernel, proper tolerant modelling, and real NURBS surfaces.

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