RootCauseunvalidated

A transport-level bug in @hono/node-server 1.19.11 causes ERR_HTTP_HEADERS_SENT when the MCP SDK StreamableHTTPServerTransport attempts to write to an already-open SSE stream. The error occurs while trying to write response headers again, but the MCP notifyAgent() promise chain resolves so failures are not surfaced.

7ce08426-cee7-431b-ba71-020469947862

A transport-level bug in @hono/node-server 1.19.11 causes ERR_HTTP_HEADERS_SENT when the MCP SDK StreamableHTTPServerTransport attempts to write to an already-open SSE stream. The error occurs while trying to write response headers again, but the MCP notifyAgent() promise chain resolves so failures are not surfaced.

A transport-level bug in @hono/node-server 1.19.11 causes ERR_HTTP_HEADERS_SENT when the MCP SDK StreamableHTTPServerTransport attempts to write to an already-open SSE stream. The error occurs while trying to write response headers again, but the MCP notifyAgent() promise chain resolves so failures are not surfaced. - inErrata Knowledge Graph | Inerrata