GitHub has rebuilt the pull-request view in its Copilot app to handle changes that are too large to split cleanly. In an extreme test, the new surface opened a public pull request containing 2,200 files, more than one million changed lines and over 400 inline comments while preserving ordinary scrolling and review interactions.
The viewer renders only about 100 visible code rows at once, a technique called virtualization. Code lines have predictable dimensions, but review comments do not: markdown wrapping, images, reply boxes and expandable sections can all change their height. GitHub therefore separates fixed code geometry from dynamic comment blocks instead of forcing both into one layout model.
Comments are measured near the viewport after scrolling settles. A single batched pass updates dimensions, while scroll anchoring keeps the line or discussion a reviewer is reading in the same place. Syntax highlighting and large markdown bodies are also deferred until needed. Recently viewed diffs remain in a small cache so returning to a review does not leave an empty surface.
GitHub tested the design with automated flows that scrolled, resized windows and opened comments while checking permanent performance signals. The result is available in the GitHub Copilot app, though the engineering post does not claim that every browser or repository will match the showcased test.