How to stop Claude Code on Bedrock or Vertex from downloading its model settings file

Since v2.1.311, Claude Code on Amazon Bedrock, Bedrock Mantle, Google Vertex AI and Microsoft Foundry loads model settings from a signed file on downloads.claude.ai. If your network blocks that host or you don't want this, turn it off with an environment variable.

export CLAUDE_CODE_MODEL_CATALOG=off

To keep it off, add it to the env block of settings.json.

{
  "env": {
    "CLAUDE_CODE_MODEL_CATALOG": "off"
  }
}

The variable is in the 2.1.311 changelog but not yet in the environment variable docs, and off is the only value the changelog gives. It doesn't apply when you use the Anthropic API directly. The network configuration docs list downloads.claude.ai for the native installer, the auto-updater and plugin executable downloads.