New safeguards automatically disconnect MCP servers that produce excessive non-protocol data, preventing unbounded memory growth:
HttpBodyOverflowError: An HTTP SSE transport disconnects when a response body exceeds the size limit without an SSE event boundary. The server is likely returning logs or non-protocol data in the response stream.StdoutOverflowError: A stdio transport disconnects when the server writes too much to stdout without a JSON-RPC message boundary. This catches servers writing debug logs to stdout instead of stderr.
Both errors produce a clear diagnostic message including the size at which disconnection occurred.
Evidence
New error classes (search for "without an SSE event boundary" and "without a JSON-RPC message boundary")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.