MCP startup reports interruption when server returns -32601 for optional resources/templates/list

Summary

Codex reports:

MCP startup interrupted. The following servers were not initialized: mintlify_index

The MCP server does initialize successfully, but Codex subsequently calls
resources/templates/list. The server returns the valid JSON-RPC response
-32601 Method not found because it does not advertise resource templates.
Codex treats this optional unsupported method as a startup failure.

Environment

• Codex CLI: 0.147.0
• macOS 26.6.1
• MCP transport: streamable HTTP
• Server: https://index.mintlify.com

Minimal reproduction

Configure:

[mcp_servers.mintlify_index]
url = "https://index.mintlify.com"

The server responds successfully to initialize:

{
  "result": {
    "protocolVersion": "2025-06-18",
    "capabilities": {
      "tools": {
        "listChanged": true
      }
    },
    "serverInfo": {
      "name": "mintlify-universal-search",
      "version": "1.0.0"
    }
  },
  "jsonrpc": "2.0",
  "id": 1
}

Codex then logs:

Failed to list resource templates for MCP server 'mintlify_index':
Mcp error: -32601: Method not found

Expected behavior

If the server does not advertise resources or resourceTemplates, Codex should skip those probes. If it probes anyway and receives -32601, it should treat that as an unsupported optional capability rather than failing MCP startup.

Actual behavior

Codex surfaces the unsupported optional method as an MCP startup interruption and reports the server as not initialized.

Workaround

Removing and re-adding the server does not change the behavior. The server itself is reachable and completes the initialize handshake.