Demote repo exploration to a cheap model, keep 78-94% of localization quality for 5-16% of the tokens.

IssueLoc-Bench evaluated five explorer models under an identical read-only interface on 499 SWE-bench Verified tasks plus 500 from 153 other repositories, measuring file-finding separately from patching (arXiv 2608.29675). Lower-cost explorers retained 78-94% of reference Hit@3 and 73-92% of F1 while cutting mean agent time 41-88% and tokens 84-95%. Which metric you optimize depends on the handoff: ranking matters if the next stage re-reads candidates, F1 and exact match matter if localization is a hard file gate.