Show HN: Formally verified polygon intersection – Opus 4.8 oneshots, prev failed

The update

To my knowledge, this is the first formally verified implementation of an intersection algorithm for polygons. The experience of working with AI agents on this project changed a lot with recent model releases, as I describe in the readme.

The significance

8 is able to provide algorithm implementation with formal proof in one shot, whereas previous models required me to provide proof strategies in multiple steps. Trust in the correctness comes entirely from the Lean checker and human review of a small specification, not from the LLM.

The context

Also check out the web demo built around the verified core linked in the readme: https://schildep

Where this fits in Signal Ledger

Related coverage from the Technology desk.

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The read

Trust in the correctness comes entirely from the Lean checker and human review of a small specification, not from the LLM. It supports multipolygons including holes, self intersections, and overlapping edges.