A compliance-research subagent queries a regulatory filings database. When the database times out, the subagent catches the error and returns an empty results list with a success status. Final reports state "no relevant filings found" for companies whose filings were never retrieved. What is the root cause?

Answer: B — The subagent reports an access failure the same way as a valid empty result

Returning an empty success for a timeout suppresses the error, so the coordinator can't tell "we couldn't look" from "we looked and found nothing." Access failures and valid empty results must be reported distinctly. (A) matters downstream, but the information was already lost. (C) may reduce timeouts but leaves the reporting flaw. (D) is the opposite anti-pattern, terminating on a single failure.