Rendering huge pull requests in the GitHub Copilot app

GitHub rebuilt its Copilot app's pull request view to handle rendering pressure from huge diffs and comments, testing an open-source PR with 2,200 files, over 1 million changed lines and more than 400 inline comments. It separates document height into deterministic code geometry and dynamic block geometry: code line heights are computed precisely in advance, while comments and other dynamic blocks use bounded heights and deferred measurements, with corrections anchored to the user's current position.