It's using layout code from my library (Taffy) for Flexbox and CSS Grid. Servo uses Taffy for CSS Grid, and another open source engine that I work on (Blitz) uses it for Flexbox, CSS Grid, Block and float layout.

The older block/inline layout modes seem to be custom code that looks to me similar but not exactly the same as Servo code. But I haven't compared this closely.

I would note that the AI does not seem to have matched either Servo or Blitz in terms of layout: both can layout Google.com better than the posted screenshot.

It seemingly did but after I saw it define a VerticalAlign twice in different files[1][2][3] I concluded that it's probably not coherent enough to waste time on checking the correctness.

Would be interesting if someone who has managed to run it tries it on some actually complicated text layout edge cases (like RTL breaking that splits a ligature necessitating re-shaping, also add some right-padding in there to spice things up).

[1] https://github.com/wilsonzlin/fastrender/blob/main/src/layou...

[2] https://github.com/wilsonzlin/fastrender/blob/main/src/layou...

[3] Neither being the right place for defining a struct that should go into computed style imo.

Cursor didn't write anything, they used ChatGPT 5.2.