feat(satellite): enhance MCP protocol to handle initialized notifications

Author: Lasim

services/satellite/src/core/streamable-http-handler.ts

@@ -309,35 +309,14 @@ export class StreamableHTTPHandler {
     // Set session ID header in response
     reply.header('Mcp-Session-Id', actualSessionId);
 
-    // Determine response mode
-    const wantsStreaming = acceptHeader.includes('text/event-stream');
+    // ALWAYS return JSON for initialize, even if Accept includes text/event-stream
+    // The SSE stream is established via separate GET request
+    reply.code(200).send(initResponse);
 
-    if (wantsStreaming) {
-      // Return SSE stream
-      reply.raw.writeHead(200, {
-        'Content-Type': 'text/event-stream',
-        'Cache-Control': 'no-cache',
-        'Connection': 'keep-alive',
-        'Mcp-Session-Id': actualSessionId
-      });
-
-      const eventId = this.generateEventId();
-      reply.raw.write(`id: ${eventId}\nevent: message\ndata: ${JSON.stringify(initResponse)}\n\n`);
-      
-      this.logger.debug({
-        operation: 'mcp_initialize_sse_response_sent',
-        sessionId: actualSessionId,
-        eventId
-      }, 'Initialize SSE response sent');
-    } else {
-      // Return standard JSON response
-      reply.code(200).send(initResponse);
-      
-      this.logger.debug({
-        operation: 'mcp_initialize_json_response_sent',
-        sessionId: actualSessionId
-      }, 'Initialize JSON response sent');
-    }
+    this.logger.debug({
+      operation: 'mcp_initialize_json_response_sent',
+      sessionId: actualSessionId
+    }, 'Initialize JSON response sent');
   }
 
   /**
@@ -383,6 +362,17 @@ export class StreamableHTTPHandler {
       // Process the message using the MCP protocol handler
       const response = await mcpProtocolHandler.handleMcpRequest(message, sessionId);
 
+      // Handle notifications (null response)
+      if (response === null) {
+        this.logger.debug({
+          operation: 'mcp_notification_handled',
+          sessionId,
+          method: message.method
+        }, 'MCP notification handled - no response sent');
+        // Don't send anything for notifications
+        return;
+      }
+      
       this.logger.debug({
         operation: 'mcp_streaming_response_before_send',
         sessionId,
@@ -461,6 +451,18 @@ export class StreamableHTTPHandler {
       // Process the message using the MCP protocol handler
       const response = await mcpProtocolHandler.handleMcpRequest(message, sessionId);
 
+      // Handle notifications (null response)
+      if (response === null) {
+        this.logger.debug({
+          operation: 'mcp_notification_handled',
+          sessionId,
+          method: message.method
+        }, 'MCP notification handled - no response sent');
+        // Don't send anything for notifications
+        reply.code(204).send(); // 204 No Content
+        return;
+      }
+      
       this.logger.debug({
         operation: 'mcp_response_before_send',
         sessionId,

services/satellite/src/server.ts

@@ -247,6 +247,9 @@ export async function createServer() {
   runtimeState.listenToProcessManager(processManager);
 
   // Initialize Remote Tool Discovery Manager for HTTP/SSE remote servers (EventBus will be added after registration)
+  // NOTE: Do NOT call initialize() here - it will be called automatically after initial config is fetched
+  // The RemoteToolDiscoveryManager has smart fallback: handleConfigurationUpdate() will trigger
+  // full initialization if not yet initialized (see line 423-429 in remote-tool-discovery-manager.ts)
   const remoteToolDiscoveryManager = new RemoteToolDiscoveryManager(server.log);
   remoteToolDiscoveryManager.setConfigManager(dynamicConfigManager);
 

services/satellite/src/services/mcp-protocol-handler.ts

@@ -48,6 +48,14 @@ export class McpProtocolHandler {
           result = await this.handleInitialize(params);
           break;
 
+        case 'notifications/initialized':
+          // MCP notification - no response needed, just log and return null
+          this.logger.debug({
+            operation: 'mcp_notification_initialized',
+            session_id: sessionId
+          }, 'MCP client sent initialized notification');
+          return null; // Notifications don't get responses
+        
         case 'tools/list':
           result = await this.handleToolsList();
           break;
@@ -440,6 +448,7 @@ export class McpProtocolHandler {
   isSupportedMethod(method: string): boolean {
     const supportedMethods = [
       'initialize',
+      'notifications/initialized',
       'tools/list',
       'tools/call',
       'resources/list',
@@ -459,6 +468,7 @@ export class McpProtocolHandler {
     return {
       supported_methods: [
         'initialize',
+        'notifications/initialized',
         'tools/list',
         'tools/call',
         'resources/list',