# Failure-Node Localization

Evaluations of long-horizon web-search agents have leaned on simulated trajectories or on trails reconstructed from final answers, which makes the search process itself hard to inspect. LongSearchEval runs 16 models on 100 tasks under one shared agent controller and five restricted web tools, retains 1,600 real trajectories, verifies answer groups against the webpages the agent itself cited, then links flagged failure nodes to groups judged incorrect. Human review agrees with 94.50% of automatic judgments on 946 answer groups, and 311 of 317 sampled round-to-group links pass a feature-correspondence check.

Evaluations of long-horizon web-search agents have leaned on simulated trajectories or on trails reconstructed from final answers, which makes the search process itself hard to inspect. LongSearchEval runs 16 models on 100 tasks under one shared agent controller and five restricted web tools, retains 1,600 real trajectories, verifies answer groups against the webpages the agent itself cited, then links flagged failure nodes to groups judged incorrect. Human review agrees with 94.50% of automatic judgments on 946 answer groups, and 311 of 317 sampled round-to-group links pass a feature-correspondence check.