# Claude Managed Agents now applies host rules to search and fetch

By Steven Van · 2026-10-07

Blocked hosts produce fetch errors and disappear from search results; unrestricted networking and self-hosted environments are unaffected.

The host list for limited cloud networking now governs web search and fetching in [Anthropic](<https://creatorstoolbox.com/tools/anthropic>)'s Claude Managed Agents, even though those tools run on Anthropic's servers.

## How blocked hosts are handled

A web\_fetch call to a host outside allowed\_hosts returns an error result to the agent, while web\_search omits results from those hosts. If allowed\_hosts is empty, neither tool returns a page or a search result.

## Configuring access

Add a host to allowed\_hosts to let the tools reach it. That also opens the host to the sandbox. The allow\_package\_managers and allow\_mcp\_servers settings do not grant these tools access to additional hosts.

Bare hostnames match only the exact host: example.com does not include docs.example.com. A wildcard such as \*.example.com matches subdomains, but not example.com itself. The tools can be restricted further through allowed\_domains or blocked\_domains in the agent toolset.

## Session validation and scope

With limited networking, creating a session or updating it to add an enabled web tool's allowed\_domains entry outside allowed\_hosts fails with a 400 error. To resolve it, add the host to allowed\_hosts or remove the entry from allowed\_domains.

Unrestricted networking and self-hosted environments do not impose these limits on the web tools. The [environment networking documentation](<https://platform.claude.com/docs/en/managed-agents/environments#networking>) explains the host settings.

![Anthropic](<https://www.google.com/s2/favicons?domain=anthropic.com&sz=128>)

Anthropic

Anthropic is an AI safety and research company that's working to build reliable, interpretable, and steerable AI systems.

[View Anthropic →](<https://creatorstoolbox.com/tools/anthropic>)

[Original source](<https://platform.claude.com/docs/en/release-notes/overview#october-7-2026>)

[Read Claude Managed Agents now applies host rules to search and fetch on Creators Toolbox](<https://creatorstoolbox.com/blog/anthropic-managed-agents-applies-host-rules-to-search-and-fetch>)

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Canonical source: https://creatorstoolbox.com/blog/anthropic-managed-agents-applies-host-rules-to-search-and-fetch