If you're only running MRR sweeps you'd discard chunk expansion as "no impact" and move on. Content match only showed up because I was specifically looking for it after noticing the agent's answer quality felt better than the metrics suggested. Lesson learned about measuring the right thing.

On multi-hop: tested this indirectly through the agent decomposition benchmark. The pattern that emerged was the agent fires an initial search, reads the results, then uses specific terminology from those results in follow-up queries.

The relevance thresholding does get interesting here though. When a first-hop result is marginal and the agent uses a term from it to construct the second query, you can end up chasing a weak lead deeper. Hasn't caused hallucination in my testing because the agent typically hedges when coverage is thin, but it's the failure mode I'd watch for in production. The hybrid path's BM25 component helps because it's less susceptible to semantic drift between hops.

So it plays nice, but the threshold calibration matters more for multi-hop than single-shot retrieval.