Let the running tool report its own progress, and KV eviction beats every published duration predictor.

arXiv 2609.18849 proves no estimate fixed before a tool call starts can even rank calls correctly, which kills the whole family of guessing from tool name, history, declared duration or engine occupancy. A census of four public agent corpora found a readable progress signal in most tool time once the tool is allowed to emit it, as fraction-of-work-remaining or an end-is-near flag. At the moments a KV-cache decision gets made, reported progress is several times to an order of magnitude more accurate than the best published predictors, holds under environment change, and cut p90 time-to-first-token in a production engine through a few small hints. If you own the tools, emitting progress is nearly free and it beats every predictor built on top of you.