Single-page Claude writes beautifully. At 5 pages it drifts. Here's the harness I built.

TL;DR

I gave Claude / Codex a Figma file + a PRD and asked for 5-10 React pages of a working app. Single-page output is great. Multi-page output drifts in 4 specific ways. I spent ~3 months building a harness with 14 gates × auto-retry × handoff JSON to stop the drift. 10 demos, 54 screens, 4 unrelated business domains, build-green rate 100%.

Code: https://github.com/JiuwenDragon/harness-mini

The honest opening

Every "Figma to code with AI" demo on Twitter shows one screen. That's a real result — Claude vision is genuinely good at single-page UI. I verified this many times during my research: giving Claude a screenshot + a paragraph of PRD produces a 70-80 point page in 30 seconds.