I do not know how FastHTML works with AI, but for the recent Svelte 5, which has a similar llms.txt file, it's clear to me that actual usage patterns are required over explanatory llms.txt content with instructions. In Svelte 5 usage, it's consistent at certain things which the docs spell out for version 5 and would not be in the training data (runes) but not in their placement, reactivity, or usage changes implied by the system (e.g. changes of information flow outside of props/states)

It seems similar to a cheat sheet which has formulas, vs a cheat sheet with worked through sample problems that align perfectly with the test.

The latter exists for historic modules - the former is the best you can do for recent libraries/versions.

I am not sure where React stands as I know they have changed their reactivity model and introduced patterns which reduce boilerplate code. Can anyone comment on the latest react version used with AI?