Network access - Terrapin

Most setups need nothing here. This page matters only if your assistant runs somewhere with restricted outbound network access: a container, an agent sandbox with a domain allowlist, or a corporate proxy.

Hosts to allow

Host	Used for
`terrapinfinance.com`	The MCP endpoint and every API call made through it.
`s3.eu-central-003.backblazeb2.com`	Document downloads, which return short-lived presigned URLs on this host.

Both are needed. Over MCP, download_document returns a presigned URL rather than the file bytes, and fetching that URL is an ordinary network request that the sandbox’s egress rules apply to. Allowing only terrapinfinance.com produces the most common symptom we see: the assistant finds and lists documents happily, then reports that it located them but cannot read them.

Allowlist both hosts by name. Presigned URLs carry a signature bound to the host in the URL, so routing them through a rewriting proxy or a different S3 endpoint invalidates the signature and returns 403.

Where to set it

In Claude Desktop, the allowed-domains list is under Settings → Capabilities → Network access on Free, Pro, and Max. On Team and Enterprise it is an administrator policy under Organization settings → Capabilities → Code execution → Allow network egress, and the in-app setting will not override it. In Claude Code, run /sandbox to inspect the current policy, or add the hosts to sandbox.network.allowedDomains in ~/.claude/settings.json:

settings.json

{
  "sandbox": {
    "network": {
      "allowedDomains": [
        "terrapinfinance.com",
        "s3.eu-central-003.backblazeb2.com"
      ]
    }
  }
}

Network policy is read when a session starts, so open a new conversation before testing. A corporate proxy also has to let POST https://terrapinfinance.com/mcp through with the Authorization header intact; proxies that strip it make every call fail with 401.

​Hosts to allow

​Where to set it

Hosts to allow

Where to set it