Fix transport session id mismatch with sessionId

mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/server/transport/WebFluxSseServerTransportProvider.java

@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.util.Map;
+import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
 import com.fasterxml.jackson.core.type.TypeReference;
@@ -261,8 +262,8 @@ private Mono<ServerResponse> handleSseConnection(ServerRequest request) {
 			.body(Flux.<ServerSentEvent<?>>create(sink -> {
 				WebFluxMcpSessionTransport sessionTransport = new WebFluxMcpSessionTransport(sink);
 
-				McpServerSession session = sessionFactory.create(sessionTransport);
-				String sessionId = session.getId();
+				String sessionId = UUID.randomUUID().toString();
+				McpServerSession session = sessionFactory.create(sessionId, sessionTransport);
 
 				logger.debug("Created new SSE connection for session: {}", sessionId);
 				sessions.put(sessionId, session);

mcp-spring/mcp-spring-webmvc/src/main/java/io/modelcontextprotocol/server/transport/WebMvcSseServerTransportProvider.java

@@ -263,7 +263,7 @@ private ServerResponse handleSseConnection(ServerRequest request) {
 				});
 
 				WebMvcMcpSessionTransport sessionTransport = new WebMvcMcpSessionTransport(sessionId, sseBuilder);
-				McpServerSession session = sessionFactory.create(sessionTransport);
+				McpServerSession session = sessionFactory.create(sessionId, sessionTransport);
 				this.sessions.put(sessionId, session);
 
 				try {

mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

@@ -340,9 +340,9 @@ private static class AsyncServerImpl extends McpAsyncServer {
 			notificationHandlers.put(McpSchema.METHOD_NOTIFICATION_ROOTS_LIST_CHANGED,
 					asyncRootsListChangedNotificationHandler(rootsChangeConsumers));
 
-			mcpTransportProvider.setSessionFactory(
-					transport -> new McpServerSession(UUID.randomUUID().toString(), requestTimeout, transport,
-							this::asyncInitializeRequestHandler, Mono::empty, requestHandlers, notificationHandlers));
+			mcpTransportProvider
+				.setSessionFactory((id, transport) -> new McpServerSession(id, requestTimeout, transport,
+						this::asyncInitializeRequestHandler, Mono::empty, requestHandlers, notificationHandlers));
 		}
 
 		// ---------------------------------------

mcp/src/main/java/io/modelcontextprotocol/server/transport/HttpServletSseServerTransportProvider.java

@@ -219,7 +219,7 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
 				writer);
 
 		// Create a new session using the session factory
-		McpServerSession session = sessionFactory.create(sessionTransport);
+		McpServerSession session = sessionFactory.create(sessionId, sessionTransport);
 		this.sessions.put(sessionId, session);
 
 		// Send initial endpoint event

mcp/src/main/java/io/modelcontextprotocol/server/transport/StdioServerTransportProvider.java

@@ -12,6 +12,7 @@
 import java.io.Reader;
 import java.nio.charset.StandardCharsets;
 import java.util.Map;
+import java.util.UUID;
 import java.util.concurrent.Executors;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Function;
@@ -94,7 +95,8 @@ public StdioServerTransportProvider(ObjectMapper objectMapper, InputStream input
 	public void setSessionFactory(McpServerSession.Factory sessionFactory) {
 		// Create a single session for the stdio connection
 		var transport = new StdioMcpSessionTransport();
-		this.session = sessionFactory.create(transport);
+		String sessionId = UUID.randomUUID().toString();
+		this.session = sessionFactory.create(sessionId, transport);
 		transport.initProcessing();
 	}
 

mcp/src/main/java/io/modelcontextprotocol/spec/McpServerSession.java

@@ -342,10 +342,11 @@ public interface Factory {
 
 		/**
 		 * Creates a new 1:1 representation of the client-server interaction.
+		 * @param sessionId the id of the session.
 		 * @param sessionTransport the transport to use for communication with the client.
 		 * @return a new server session.
 		 */
-		McpServerSession create(McpServerTransport sessionTransport);
+		McpServerSession create(String sessionId, McpServerTransport sessionTransport);
 
 	}
 

mcp/src/test/java/io/modelcontextprotocol/MockMcpServerTransportProvider.java

@@ -16,6 +16,7 @@
 package io.modelcontextprotocol;
 
 import java.util.Map;
+import java.util.UUID;
 
 import io.modelcontextprotocol.spec.McpSchema;
 import io.modelcontextprotocol.spec.McpServerSession;
@@ -43,7 +44,8 @@ public MockMcpServerTransport getTransport() {
 	@Override
 	public void setSessionFactory(Factory sessionFactory) {
 
-		session = sessionFactory.create(transport);
+		String sessionId = UUID.randomUUID().toString();
+		session = sessionFactory.create(sessionId, transport);
 	}
 
 	@Override

mcp/src/test/java/io/modelcontextprotocol/server/transport/StdioServerTransportProviderTests.java

@@ -71,7 +71,7 @@ void setUp() {
 		sessionFactory = mock(McpServerSession.Factory.class);
 
 		// Configure mock behavior
-		when(sessionFactory.create(any(McpServerTransport.class))).thenReturn(mockSession);
+		when(sessionFactory.create(any(), any(McpServerTransport.class))).thenReturn(mockSession);
 		when(mockSession.closeGracefully()).thenReturn(Mono.empty());
 		when(mockSession.sendNotification(any(), any())).thenReturn(Mono.empty());
 
@@ -110,7 +110,7 @@ void shouldHandleIncomingMessages() throws Exception {
 		AtomicReference<McpSchema.JSONRPCMessage> capturedMessage = new AtomicReference<>();
 		CountDownLatch messageLatch = new CountDownLatch(1);
 
-		McpServerSession.Factory realSessionFactory = transport -> {
+		McpServerSession.Factory realSessionFactory = (id, transport) -> {
 			McpServerSession session = mock(McpServerSession.class);
 			when(session.handle(any())).thenAnswer(invocation -> {
 				capturedMessage.set(invocation.getArgument(0));