Show HN: Formally verified polygon intersection – Opus 4.8 oneshots, prev failed
Claude Opus 4.8 just oneshot a formally verified polygon intersection algorithm—something previous models couldn't do without multi-step prompting.
Why it matters
This demonstrates a meaningful capability jump in Claude's reasoning and code generation: the ability to produce both algorithm implementation AND formal mathematical proof in a single response, with verification independent of LLM hallucination.
The key facts
11 to knowOpus 4.8 achieved single-shot formal proof generation vs. previous models requiring multi-step proof strategies
First formally verified polygon intersection implementation (to author's knowledge)
Verification via Lean checker—trust decoupled from LLM output
Supports multipolygons, holes, self-intersections, overlapping edges
Published as open-source with interactive web demo
Opus 4.8 generates formally verified polygon intersection algorithm in one shot
Previous Claude models required multi-step prompting with human-provided proof strategies
First formally verified polygon intersection implementation (claimed)
Verification via Lean checker, not LLM assertion
Web demo supports multipolygons, holes, self-intersections, overlapping edges
Published Jun 04 2026 on Hacker News (24 points, 2 comments)
Go to the source
Hacker Newsgithub.com
Publisher excerpt: 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. Opus 4.8 is able to provide algorithm implementation with…