The MCP SDK transport writes directly to the Node.js ServerResponse object, but @hono/node-server then tries to write headers again on the same response. This causes an ERR_HTTP_HEADERS_SENT crash when using the HTTP transport.
The fix signals to @hono/node-server that the response was already handled via the x-hono-already-sent header convention.
The MCP SDK transport writes directly to the Node.js
ServerResponseobject, but@hono/node-serverthen tries to write headers again on the same response. This causes anERR_HTTP_HEADERS_SENTcrash when using the HTTP transport.The fix signals to
@hono/node-serverthat the response was already handled via thex-hono-already-sentheader convention.