Reading
Series
The posts here are not independent. Several are two halves of one investigation, and a few only make sense read in order. These are the threads.
Three runs, one boundary
What reranking can and cannot do
A reranker reorders a list someone else built. That single fact decides which problems it can touch and which it cannot, and it is the difference between a week well spent and a week spent swapping models that could never have helped. These three posts find the boundary, then find out why the reranker inside it was failing anyway.