don't need to re-initialize when we reconnect a session

Author: ihrpr

src/client/index.ts

@@ -126,7 +126,11 @@ export class Client<
 
   override async connect(transport: Transport, options?: RequestOptions): Promise<void> {
     await super.connect(transport);
-
+    // When transport sessionId is already set this means we are trying to reconnect.
+    // In this case we don't need to initialize again.
+    if (transport.sessionId !== undefined) {
+      return;
+    }
     try {
       const result = await this.request(
         {

src/server/streamableHttp.ts

@@ -331,11 +331,10 @@ export class StreamableHTTPServerTransport implements Transport {
       const isInitializationRequest = messages.some(
         msg => 'method' in msg && msg.method === 'initialize'
       );
-      const mcpSessionId = req.headers["mcp-session-id"] as string | undefined;
       if (isInitializationRequest) {
         // If it's a server with session management and the session ID is already set we should reject the request
         // to avoid re-initialization.
-        if (this._initialized && this.sessionId !== undefined && mcpSessionId !== this.sessionId) {
+        if (this._initialized) {
           res.writeHead(400).end(JSON.stringify({
             jsonrpc: "2.0",
             error: {
@@ -357,7 +356,7 @@ export class StreamableHTTPServerTransport implements Transport {
           }));
           return;
         }
-        this.sessionId = mcpSessionId ?? this.sessionIdGenerator();
+        this.sessionId = this.sessionIdGenerator();
         this._initialized = true;
 
       }