Under the hood
Claude Code now tells apart real SSE connection failures from harmless error-looking responses
What
When posting to an MCP server's streaming endpoint (SSE, a way servers push data over an HTTP connection) fails with an HTTP 400, 404, or 405 status, Claude Code now looks inside the response body to check whether it's actually a harmless JSON-RPC response with a null ID, rather than a real connection failure.
Why
This avoids treating a technically error-coded but benign server response as a genuine connection problem, which should cut down on false failure reports for some MCP servers.