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Description
Is your feature request related to a problem? Please describe.
Right now, scrolling up in a room which heavily uses threads is really slow and feels broken as most /messages results are not for the main timeline and instead are events from threads.
Describe the solution you'd like
/messages filter which lets the client paginate the main timeline where the responses only include events for that timeline
Describe alternatives you've considered
Making the server go faster so this is less painful but it is still quite wasteful of data and worst case could still result in many pages of content which cannot be rendered in that timeline.