In Claude Managed Agents, cloud environments with limited networking now enforce their allowed_hosts list on the web_search and web_fetch tools: web_fetch returns a url_not_allowed error for non-matching hosts and web_search omits results from them. Session creation or updates fail with a 400 error if an enabled web tool's allowed_domains entry is not within allowed_hosts, and matching is per exact host unless the entry starts with *.
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What to doIf you use limited networking with web tools, add any hosts in allowed_domains to allowed_hosts (or remove those entries) to avoid 400 errors on session creation.
- Provider
- Anthropic
- Source
- platform.claude.com