fix: close SSE stream immediately

Author: paoloricciuti

README.md

@@ -12,6 +12,9 @@ pnpm dev
 
 1. Set the VOYAGE_API_KEY for embeddings support
 
+> [!NOTE]
+> Currently to prevent having a bunch of Timeout logs on vercel we shut down the SSE channel immediately. This means that we can't use `server.log` and we are not sending `list-changed` notifications. We can use elicitation and sampling since those are sent on the same stream of the POST request
+
 ### Local dev tools
 
 #### MCP inspector

package.json

@@ -64,7 +64,7 @@
 		"@eslint/compat": "^1.2.5",
 		"@eslint/js": "^9.18.0",
 		"@tmcp/adapter-valibot": "^0.1.4",
-		"@tmcp/transport-http": "^0.6.0",
+		"@tmcp/transport-http": "^0.6.1",
 		"@tmcp/transport-stdio": "^0.1.3",
 		"@typescript-eslint/parser": "^8.43.0",
 		"eslint": "^9.36.0",

pnpm-lock.yaml

@@ -1,5 +1,20 @@
 import { http_transport } from '$lib/mcp';
 
 export async function handle({ event, resolve }) {
-	return (await http_transport.respond(event.request)) ?? resolve(event);
+	const mcp_response = await http_transport.respond(event.request);
+	// we are deploying on vercel the SSE connection will timeout after 5 minutes...for
+	// the moment we are not sending back any notifications (logs, or list changed notifications)
+	// so it's a waste of resources to keep a connection open that will error
+	// after 5 minutes making the logs dirty. For this reason if we have a response from
+	// the MCP server and it's a GET request we just return an empty response (it has to be
+	// 200 or the MCP client will complain)
+	if (mcp_response && event.request.method === 'GET') {
+		try {
+			await mcp_response.body?.cancel();
+		} catch {
+			// ignore
+		}
+		return new Response('', { status: 200 });
+	}
+	return mcp_response ?? resolve(event);
 }