[BUG] Notion MCP blocked by proxy in Cowork sessions - mcp.notion.com not on allowlist

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Notion MCP tools show as "connected" in mcp-registry but are not available in Cowork sessions. When trying to use Notion MCP locally via claude mcp add, the connection fails because the Cowork proxy blocks mcp.notion.com.

What happens:

1. Run: claude mcp add --transport http notion https://mcp.notion.com/mcp
2. Run: claude mcp list → Shows notion: ✗ Failed to connect
3. Testing with curl shows the proxy blocks the connection:

curl -v https://mcp.notion.com/mcp
HTTP/1.1 403 Forbidden
X-Proxy-Error: blocked-by-allowlist

Expected behavior:
Notion MCP should work in Cowork sessions, similar to how "Claude in Chrome" MCP works (via SDK channel that bypasses proxy).

What Should Happen?

1. claude mcp add --transport http notion https://mcp.notion.com/mcp should successfully connect
2. claude mcp list should show notion: ✓ Connected
3. Notion MCP tools (search, create-pages, update-page, etc.) should be available in the Cowork session

Suggested solutions:

• Add mcp.notion.com to Cowork proxy allowlist
• Or implement Notion as SDK-type server (like "Claude in Chrome") that bypasses proxy

Error Messages/Logs

$ claude mcp list
Checking MCP server health...
notion: https://mcp.notion.com/mcp (HTTP) - ✗ Failed to connect

$ curl -v https://mcp.notion.com/mcp
* Uses proxy env variable https_proxy == 'http://localhost:3128'
* Trying 127.0.0.1:3128...
* Connected to (nil) (127.0.0.1) port 3128
> CONNECT mcp.notion.com:443 HTTP/1.1
< HTTP/1.1 403 Forbidden
< Content-Type: text/plain
< X-Proxy-Error: blocked-by-allowlist
* Received HTTP code 403 from proxy after CONNECT

Steps to Reproduce

1. Start a Cowork session
2. Run: claude mcp add --transport http notion https://mcp.notion.com/mcp
3. Run: claude mcp list
4. Observe: notion: ✗ Failed to connect
5. Test with curl: curl -v https://mcp.notion.com/mcp
6. Observe: HTTP/1.1 403 Forbidden with X-Proxy-Error: blocked-by-allowlist

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.8 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Important context:

Chrome MCP works in Cowork because it uses "type": "sdk" in the mcp-config, which goes through a special channel that bypasses the proxy. From the process list:

--mcp-config '{"mcpServers":{"Claude in Chrome":{"type":"sdk","name":"Claude in Chrome"},...}}'

Notion MCP uses HTTP transport which gets blocked by the Cowork proxy.

Environment details:

• Platform: Cowork (sandboxed container environment)
• mcp-registry shows Notion as "connected" but tools are not exposed to the session
• The proxy returns X-Proxy-Error: blocked-by-allowlist for mcp.notion.com