You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
SandboxArea: what it touches
ImprovementsKind: in v2.1.284,
ImprovementsSection of the release
Unclear Exactly which alternative spellings are recognised is not fully settled.
What
Block rules in sandbox.network.deniedDomains are now checked against a standard form of the host as well as the host exactly as written. The standard form smooths out different ways of writing an IP address and a trailing dot. When a connection is blocked, the reason names both forms.
The sandbox's network relay (the SOCKS proxy that carries sandboxed network traffic) now answers "connection not allowed" when a rule blocks a connection, instead of "host unreachable".
Why
A blocked host can no longer be reached just by writing its address differently, and a blocked connection is now reported as blocked rather than as a host that could not be found.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed sinceAnthropic's documentation has since written up sandbox.network.deniedDomains, on Tools reference.Claude Code denies URLs that point at a private, link-local, or cloud-metadata address, including hostnames that resolve to one. It also denies hosts in `sandbox.network.deniedDomains`, and when [`allowManagedDomainsOnly`](https://code.cla…tools-referencesee the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtExactly which alternative spellings are recognised is not fully settled.
Anthropic's documentation agreesAnthropic's documentation has since written up sandbox.network.deniedDomains, on Tools reference.
