Implement agent busy state

src/agent.ts

@@ -435,6 +435,20 @@ export class AgentManager {
     return this._tokenUsageChanged;
   }
 
+  /**
+   * Signal emitted when the agent's busy state changes.
+   */
+  get busyChanged(): ISignal<this, boolean> {
+    return this._busyChanged;
+  }
+
+  /**
+   * Whether the agent is currently generating a response or executing tools
+   */
+  get busy(): boolean {
+    return this._busy;
+  }
+
   /**
    * Refresh the skills snapshot and rebuild the agent if resources are ready.
    */
@@ -592,6 +606,7 @@ export class AgentManager {
    * @param message The user message to respond to (may include processed attachment content)
    */
   async generateResponse(message: string): Promise<void> {
+    this._setBusy(true);
     this._controller = new AbortController();
 
     try {
@@ -659,6 +674,7 @@ export class AgentManager {
       }
     } finally {
       this._controller = null;
+      this._setBusy(false);
     }
   }
 
@@ -1191,6 +1207,16 @@ WEB RETRIEVAL POLICY:
     return `Supported MIME types in this session: ${safeMimeTypes.join(', ')}`;
   }
 
+  /**
+   * Set busy state and emit signal
+   */
+  private _setBusy(busy: boolean): void {
+    if (this._busy !== busy) {
+      this._busy = busy;
+      this._busyChanged.emit(busy);
+    }
+  }
+
   // Private attributes
   private _settingsModel: AISettingsModel;
   private _toolRegistry?: IToolRegistry;
@@ -1201,6 +1227,8 @@ WEB RETRIEVAL POLICY:
   private _agent: ToolLoopAgent<never, ToolMap> | null;
   private _history: ModelMessage[];
   private _mcpTools: ToolMap;
+  private _busy: boolean = false;
+  private _busyChanged = new Signal<this, boolean>(this);
   private _controller: AbortController | null;
   private _agentEvent: Signal<this, IAgentEvent>;
   private _tokenUsage: ITokenUsage;

src/chat-model.ts

@@ -109,11 +109,21 @@ export class AIChatModel extends AbstractChatModel {
     this._agentManager = options.agentManager;
     this._trans = options.trans;
 
-    // Listen for agent events
+    // Listen for agent events and busy state
     this._agentManager.agentEvent.connect(this._onAgentEvent, this);
 
     // Listen for settings changes to update chat behavior
     this._settingsModel.stateChanged.connect(this._onSettingsChanged, this);
+
+    // Prevent clearing input field when user sends a message while agent is busy
+    const originalSend = this.input.send;
+    this.input.send = (content: string) => {
+      if (this._agentManager.busy) {
+        return;
+      }
+      originalSend(content);
+    };
+
     this.setReady();
   }
 
@@ -214,6 +224,11 @@ export class AIChatModel extends AbstractChatModel {
       return;
     }
 
+    // Prevent sending multiple messages concurrently
+    if (this._agentManager.busy) {
+      return;
+    }
+
     // Add user message to chat
     const userMessage: IMessageContent = {
       body: message.body,