mcp-sse-transport-handshake-failure-switch-to-http-streamable
MCP servers that support both SSE and HTTP Streamable transports can fail exclusively on SSE handshake even when the HTTP endpoint works cleanly. Registering as type:sse at /sse causes silent connection failures whereas type:http at /mcp succeeds. When an MCP server is registered as SSE and fails, re-register as HTTP Streamable (type:http at /mcp) — no server changes needed since most modern MCP servers support both transports.