DRNOISE: Benchmarking Deep Research Agents in Misleading Evidence Environments

Deep research agents increasingly operate over the open web, where relevant records coexist with redundant summaries, outdated reports, and misleading documents. Existing evaluations offer limited insight into whether agents preserve sound evidential standards when an ordinary-looking false document is deliberately seeded into a searchable environment and offers a direct shortcut to a conflicting answer. We introduce DRNOISE, a 100-task benchmark for answer recovery under misleading evidence. Each task has a unique gold answer supported by two corroborating indirect record chains; the paired noisy condition adds one plausible document that states a conflicting answer directly. The benchmark spans ten families of evidence operations. Among models with strong clean-task performance in the shared agent framework, this single intervention causes 66--88 percentage-point accuracy drops. Trace analyses reveal a pattern of verification inertia: agents often retrieve truthful records yet defer to the answer-like document without adequately checking its claim against the underlying evidence. Generic verification prompts reduce but do not close this gap. The setting is especially relevant to open-web deployment, where plausible falsehoods arrive through ordinary-looking pages without explicit adversarial instructions. Reliable deep research therefore requires more than retrieval and citation; it requires active reconciliation of direct claims with record-level evidence.