Can we sum the text_match and custom rank score?

No that can't be done. You will have to do the re-ranking then on the client if you want a lot of custom logic like this. In any case, for vector search pagination is not recommended because of the approximate nature of the search. When you paginate, the larger search radius could produce better results that didn't show up with the smaller

k

used for the first page, and this can cause the order of results to seemingly repeat. So I recommend just doing a single request with a large

k

like

100

and then apply your custom ranking on the client side.