refactor: remove support for legacy SSE protocol

Author: sinedied

README.md

@@ -218,8 +218,8 @@ You can test the MCP server using the MCP Inspector:
 2. In your browser, open the MCP Inspector (the URL will be shown in the terminal)
 
 3. Configure the connection:
-   - **Transport**: Streamable HTTP or SSE
-   - **URL**: `http://localhost:3000/mcp` (for Streamable HTTP) or `http://localhost:3000/sse` (for legacy SSE)
+   - **Transport**: Streamable HTTP
+   - **URL**: `http://localhost:3000/mcp`
 
 4. Click **Connect** and explore the available tools
 

docs/blog/01-release/release.md

@@ -63,7 +63,7 @@ Before we play a bit with the sample, let's have a look at the main services imp
 | ------- | ---- | ---- |
 | Agent Web App (`agent-webapp`) | Chat UI + streaming + session history | Azure Static Web Apps, Lit web components |
 | Agent API (`agent-api`) | LangChain.js v1 agent orchestration + auth + history | Azure Functions, Node.js |
-| Burger MCP Server (`burger-mcp`) | Exposes burger API as tools over MCP (Streamable HTTP + SSE) | Azure Functions, Express, MCP SDK |
+| Burger MCP Server (`burger-mcp`) | Exposes burger API as tools over MCP (Streamable HTTP) | Azure Functions, Express, MCP SDK |
 | Burger API (`burger-api`) | Business logic: burgers, toppings, orders lifecycle | Azure Functions, Cosmos DB |
 
 Here's a simplified view of how they interact:

packages/burger-mcp/README.md

@@ -18,7 +18,6 @@ This is the Burger MCP server, exposing the Burger API as a Model Context Protoc
 This server supports the following transport types:
 
 - **Streamable HTTP**
-- **SSE** (legacy protocol, for backward compatibility)
 - **Stdio** (currently only supported when starting the server locally with `npm start:local`)
 
 The remote server is deployed with [Azure Functions](https://learn.microsoft.com/azure/azure-functions/functions-overview).
@@ -56,9 +55,6 @@ First, you need to start the Burger API and Burger MCP server locally.
 4. Put `http://localhost:3000/mcp` in the URL field and click on the **Connect** button.
 5. In the **Tools** tab, select **List Tools**. Click on a tool and select **Run Tool**.
 
-> [!NOTE]
-> This application also provides an SSE endpoint if you use `/sse` instead of `/mcp` in the URL field.
-
 ## Development
 
 ### Getting started
@@ -73,7 +69,7 @@ You can run the following command to run the application server:
 npm start
 ```
 
-This will start the application server. The MCP server is then available at `http://localhost:3000/mcp` or `http://localhost:3000/sse` for the streamable HTTP and SSE endpoints, respectively.
+This will start the application server. The MCP server is then available at `http://localhost:3000/mcp` for the streamable HTTP endpoints.
 
 Alternatively, you can run the MCP server with stdio transport using:
 

packages/burger-mcp/src/server.ts

@@ -1,8 +1,5 @@
 import process from 'node:process';
-import { randomUUID } from 'node:crypto';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
-import { SSEServerTransport } from '@modelcontextprotocol/sdk/server/sse.js';
-import { isInitializeRequest } from '@modelcontextprotocol/sdk/types.js';
 import express, { Request, Response } from 'express';
 import { burgerApiUrl } from './config.js';
 import { getMcpServer } from './mcp.js';
@@ -14,77 +11,42 @@ app.get('/', (_request: Request, response: Response) => {
   response.send({ status: 'up', message: `Burger MCP server running (Using burger API URL: ${burgerApiUrl})` });
 });
 
-// Store transports by session ID
-const transports: Record<string, StreamableHTTPServerTransport | SSEServerTransport> = {};
-
-// ----------------------------------------------------------------------------
-// New streamable HTTP transport
-// ----------------------------------------------------------------------------
-
 // Handle all MCP Streamable HTTP requests (GET, POST, DELETE) on a single endpoint
 app.all('/mcp', async (request: Request, response: Response) => {
   console.log(`Received ${request.method} request to /mcp`);
 
-  try {
-    // Check for existing session ID
-    const sessionId = request.headers['mcp-session-id'] as string | undefined;
-    let transport: StreamableHTTPServerTransport;
-
-    if (sessionId && transports[sessionId]) {
-      // Check if the transport is of the correct type
-      const existingTransport = transports[sessionId];
-      if (existingTransport instanceof StreamableHTTPServerTransport) {
-        // Reuse existing transport
-        transport = existingTransport;
-      } else {
-        // Transport exists but is not a StreamableHTTPServerTransport (could be SSEServerTransport)
-        response.status(400).json({
-          jsonrpc: '2.0',
-          error: {
-            code: -32_000,
-            message: 'Bad Request: Session exists but uses a different transport protocol',
-          },
-          id: null,
-        });
-        return;
-      }
-    } else if (!sessionId && request.method === 'POST' && isInitializeRequest(request.body)) {
-      transport = new StreamableHTTPServerTransport({
-        sessionIdGenerator: () => randomUUID(),
-        onsessioninitialized(sessionId) {
-          // Store the transport by session ID when session is initialized
-          console.log(`StreamableHTTP session initialized with ID: ${sessionId}`);
-          transports[sessionId] = transport;
-        },
-      });
-
-      // Set up onclose handler to clean up transport when closed
-      transport.onclose = () => {
-        const sid = transport.sessionId;
-        if (sid && transports[sid]) {
-          console.log(`Transport closed for session ${sid}, removing from transports map`);
-          delete transports[sid];
-        }
-      };
-
-      // Connect the transport to the MCP server
-      const server = getMcpServer();
-      await server.connect(transport);
-    } else {
-      // Invalid request - no session ID or not initialization request
-      response.status(400).json({
+  // Reject unsupported methods (these are only needed for stateful sessions)
+  if (request.method === 'GET' || request.method === 'DELETE') {
+    response.writeHead(405).end(
+      JSON.stringify({
         jsonrpc: '2.0',
         error: {
           code: -32_000,
-          message: 'Bad Request: No valid session ID provided',
+          message: 'Method not allowed.',
         },
         id: null,
-      });
-      return;
-    }
+      }),
+    );
+    return;
+  }
+
+  try {
+    const transport = new StreamableHTTPServerTransport({
+      sessionIdGenerator: undefined,
+    });
+
+    // Connect the transport to the MCP server
+    const server = getMcpServer();
+    await server.connect(transport);
 
     // Handle the request with the transport
     await transport.handleRequest(request, response, request.body);
+
+    // Clean up when the response is closed
+    response.on('close', async () => {
+      await transport.close();
+      await server.close();
+    });
   } catch (error) {
     console.error('Error handling MCP request:', error);
     if (!response.headersSent) {
@@ -100,48 +62,6 @@ app.all('/mcp', async (request: Request, response: Response) => {
   }
 });
 
-// ----------------------------------------------------------------------------
-// Deprecated SSE transport
-// ----------------------------------------------------------------------------
-
-app.get('/sse', async (request: Request, response: Response) => {
-  console.log('Received GET request to /sse (deprecated SSE transport)');
-  const transport = new SSEServerTransport('/messages', response);
-  transports[transport.sessionId] = transport;
-  response.on('close', () => {
-    delete transports[transport.sessionId];
-  });
-  const server = getMcpServer();
-  await server.connect(transport);
-});
-
-app.post('/messages', async (request: Request, response: Response) => {
-  const sessionId = request.query.sessionId as string;
-  let transport: SSEServerTransport;
-  const existingTransport = transports[sessionId];
-  if (existingTransport instanceof SSEServerTransport) {
-    // Reuse existing transport
-    transport = existingTransport;
-  } else {
-    // Transport exists but is not a SSEServerTransport (could be StreamableHTTPServerTransport)
-    response.status(400).json({
-      jsonrpc: '2.0',
-      error: {
-        code: -32_000,
-        message: 'Bad Request: Session exists but uses a different transport protocol',
-      },
-      id: null,
-    });
-    return;
-  }
-
-  if (transport) {
-    await transport.handlePostMessage(request, response, request.body);
-  } else {
-    response.status(400).send('No transport found for sessionId');
-  }
-});
-
 // Start the server
 const PORT = process.env.FUNCTIONS_CUSTOMHANDLER_PORT || process.env.PORT || 3000;
 app.listen(PORT, () => {
@@ -151,21 +71,5 @@ app.listen(PORT, () => {
 // Handle server shutdown
 process.on('SIGINT', async () => {
   console.log('Shutting down server...');
-
-  // Close all active transports to properly clean up resources
-  for (const sessionId in transports) {
-    if (Object.hasOwn(transports, sessionId)) {
-      try {
-        console.log(`Closing transport for session ${sessionId}`);
-        // eslint-disable-next-line no-await-in-loop
-        await transports[sessionId].close();
-        delete transports[sessionId];
-      } catch (error) {
-        console.error(`Error closing transport for session ${sessionId}:`, error);
-      }
-    }
-  }
-
-  console.log('Server shutdown complete');
   process.exit(0);
 });