Can you describe the architecture you envision for this feature? Also beware, as is evident from other PRs, I haven't really got the time or motivation to deep dive into complex topics with Phpactor.

Well my main goal is to reduce the dependency on the index as a constructor argument and move it to the methods that actually need it. Furthermore I'm trying to split up the IndexAgentBuilder as it currently is also very intertwined with the Index. But as for the steps needed to take, I'm not sure myself yet.

So I don't think this is necessarily the way to go, I need to know what this will look like before knowing how to refactor it.

I've dumped some research here: https://github.com/phpactor/phpactor/blob/645e8e8fd167352a96e8184a2554f14601d245da/doc/adr/0004-indexer.md

Looks like a good idea. In the end I was thinking of the same thing. But I wasn't sure where to best place to put the distinction which index to use was.

But I think the lower the better. So that the amount of classes having to actually deal with an index is as small as possible.