{"version":"2.1.305","anchor":"cloud-only-mcp-host-allowdeny-list-via-tengu-gleaming-creek","canonical_anchor":"cloud-only-mcp-host-allowdeny-list-via-tengu-gleaming-creek","heading":"Cloud sessions can allow or block MCP servers by host","tier":"soon","area":"MCP","scope":"org","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.305\/e\/cloud-only-mcp-host-allowdeny-list-via-tengu-gleaming-creek","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.305","markdown":"### Cloud sessions can allow or block MCP servers by host\n\nIn Anthropic cloud sessions, Claude Code can check each MCP server's host against an allow or deny list sent by the server\n\n**Unclear.** It is not confirmed that the default lets every host through, or where a blocked result actually stops a connection.\n\n**What**\n\nMCP servers are add-on tools that Claude Code connects to, and each one lives at a host, the address of the machine it runs on. In cloud sessions, Claude Code now checks an MCP server's host against a list it receives from Anthropic's server. The list can be in one of three modes:\n\n- `allow`: only the listed hosts are permitted\n\n- `deny`: the listed hosts are blocked\n\n- `all`: every host is permitted\n\nIf the list it receives is malformed, Claude Code treats it as an empty allow list, which blocks every host. A server whose host cannot be worked out is blocked too.\n\nThis applies only when `CLAUDE_CODE_REMOTE` is true and `CLAUDE_CODE_ENVIRONMENT_KIND` is unset or set to `anthropic_cloud`.\n\n**Why**\n\nThis gives Anthropic a way to limit which MCP servers a cloud session can reach. It has no effect when you run Claude Code on your own machine.\n\n- Flag `tengu_gleaming_creek`: Not enough to say (read for one account on one subscription tier against v2.1.305; this account: no value returned, anonymous baseline: no value returned, compiled default: not a boolean we can read) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.\n- Area: MCP\n- Tier: Nothing to try yet\n- Useful: 4\/5\n- Signal: 4\/5\n- Scope: org\n- Heads-up: no\n- Present in the build but not switched on"}