What would you look for in a framework-agnostic virtual scrolling engine?

The tricky part isn't just keeping the DOM small. I'd want to understand how the viewport anchor behaves when item heights change, especially when measurements arrive after the initial render.

Try showing what happens when content above the visible area grows or shrinks, and how the engine decides which item stays in place. A demo with variable-height content would make the architecture much easier to evaluate.

I'd compare it with virtualization approaches used in large code viewers and diff tools, even if those products solve a different problem. They can be useful reference points for handling lots of data and for seeing which responsibilities belong in the engine versus the component built on top.

For adoption, show a minimal integration without a framework alongside examples using framework wrappers. I'd also want a clear description of what the engine owns and what the consuming component has to supply, such as rendering and item measurements.

Performance claims would be more useful with reproducible scenarios than a huge item count alone. Show the data size, item height variation, browser, and what you're measuring. Include scrolling and updates to existing items, since those can stress different parts of the system.

I'd focus feedback on the implementation and its behavior rather than trying to infer how it was written from a commit history. A project can span a long period without having activity every day, and that history alone doesn't establish whether a tool was used.