What a publication-date filter can prove
Date filters can enforce retrieval eligibility, but historical claims need a separate check of what each result contained at the cutoff.
AWS has announced domain and publication-date filters for Web Search on AgentCore. Connector version 1.2.0 accepts per-request domain include and exclude lists plus inclusive ISO-8601 publication-date bounds. AWS says those filters constrain eligible results server-side, and results without a recognized publication date are excluded while date filtering is active (AWS announcement).
For operators, the immediate question is what that control proves. It can establish that a result met the connector’s domain and recognized-date rules. Based on the announcement alone, it cannot establish that the page contained the cited information at a requested historical cutoff.
That difference matters when an agent must answer what was published, disclosed, or knowable by a particular date.
Start with the claim the answer must support
Current-source research and retrospective research require different evidence.
For current-source research, an operator can inspect the live page, capture its reported publication or update date, and state that the evidence reflects the page as retrieved now.
A retrospective claim is stronger. It says the cited content itself was available by the cutoff. A page can retain an early publication date while its body, navigation, related-content modules, or other visible material changes later.
A 2026 ACL paper examined this problem in retrospective forecasting. Across roughly 390 resolved forecasting questions per search engine, the researchers found at least one result with major post-cutoff information for 71% of Google questions and 81.2% of DuckDuckGo questions. They identified later page updates, related-content modules, unreliable timestamps, and absence-based signals as leakage mechanisms. The authors explicitly caution that these rates may not generalize to other retrieval systems (ACL study).
Those findings do not measure AgentCore Web Search. They show the relevant failure mode in the systems studied: result-date eligibility and page-content timing can diverge.
Match the evidence path to the time claim
Our operating judgment is to make retrieval admission and historical verification separate review decisions.
At admission, configure the allowed or excluded domains, set the inclusive date bounds, and record the exact request parameters. If the active date filter excludes results without recognized dates, retain that behavior in the retrieval record rather than silently broadening the query. This stage answers whether the connector recognized a result as eligible under the configured rules (AWS announcement).
Verification begins after admission and depends on the intended claim:
- For current-source research, inspect the live page and identify the retrieval time and any reported publication or update date.
- For a defensible historical cutoff, prefer a frozen snapshot or another versioned artifact captured at or before that cutoff, then verify that the quoted passage exists in the artifact.
- If only a live page is available, label the historical status unresolved unless the page provides evidence sufficient to establish when the relevant passage appeared.
This is an SGL protocol. AWS does not claim this verification capability for the connector, and the ACL paper does not validate the protocol for AgentCore. The protocol keeps two questions explicit: did the result satisfy the retrieval rules, and does the available artifact support the time claim?
Preserve the distinction in the retrieval record
A compact record can store the query, connector version, domain rules, inclusive date bounds, retrieval timestamp, result URL, recognized publication date, and any verification artifact.
The resulting claim should name its evidence level. “Returned under a publication-date filter” describes admission. “Present in a snapshot captured before the cutoff” describes historical verification. When the second fact is unknown, the record should say so.
The same distinction clarifies evaluation failures. A forbidden domain in the result set points to admission or configuration. Post-cutoff text on an otherwise eligible page points to historical verification. Each requires a different review even when both appear in one answer.
Teams that build agent workflows around search can use date and domain rules as an early control. The remaining decision is set by the claim: a current page may support a current-source answer, while a historical answer needs evidence tied to the cutoff.