virtualized chat

text is measured with pretext — pure canvas arithmetic, zero DOM reads. code blocks, tables, images, and embeds are measured by plugins that own their dimensions.

predicted heights feed into the virtualizer. only visible messages are in the DOM. scroll position is preserved across width changes. strategies are cached — streaming only recomputes 1 message per frame.

after paint, a ResizeObserver measures the real DOM height. any drift between prediction and reality is corrected automatically. the result: accurate layout with zero layout thrashing.