feat(gateway): wire safe-point runtime cancellation for agent.cancel

src/backends/native/agent.ts

@@ -53,6 +53,8 @@ export class NativeAgent {
   private _attachmentCollector?: OutboundAttachmentCollector;
   private _thinking: boolean = false;
   private _lastToolFingerprint?: string;
+  private _cancelRequested = false;
+  private _runInProgress = false;
 
   constructor(config: NativeAgentConfig) {
     this.modelClient = config.modelClient;
@@ -71,31 +73,48 @@ export class NativeAgent {
   }
 
   async process(userMessage: string, attachments?: Attachment[]): Promise<string> {
+    this._cancelRequested = false;
+    this._runInProgress = true;
+
     // Detect and strip !!think prefix for per-message thinking mode
-    if (userMessage.startsWith('!!think ') || userMessage === '!!think') {
-      this._thinking = true;
-      userMessage = userMessage.replace(/^!!think\s*/, '').trim() || 'Think about this.';
-    } else {
-      this._thinking = false;
+    try {
+      if (userMessage.startsWith('!!think ') || userMessage === '!!think') {
+        this._thinking = true;
+        userMessage = userMessage.replace(/^!!think\s*/, '').trim() || 'Think about this.';
+      } else {
+        this._thinking = false;
+      }
+
+      const userMsg = buildUserMessage(userMessage, attachments);
+
+      if (this.session) {
+        this.session.addMessage(userMsg);
+      } else {
+        this.inMemoryHistory.push(userMsg);
+      }
+
+      // If no tools configured, use the simple single-turn path
+      if (!this.toolRegistry || !this.toolExecutor) {
+        return await this.singleTurn();
+      }
+
+      return await this.toolLoop();
+    } catch (error) {
+      if (this.isAbortError(error)) {
+        const cancelledMsg = 'Operation cancelled by user.';
+        this.addToHistory({ role: 'assistant', content: cancelledMsg });
+        return cancelledMsg;
+      }
+      throw error;
+    } finally {
+      this._runInProgress = false;
+      this._cancelRequested = false;
     }
-
-    const userMsg = buildUserMessage(userMessage, attachments);
-
-    if (this.session) {
-      this.session.addMessage(userMsg);
-    } else {
-      this.inMemoryHistory.push(userMsg);
-    }
-
-    // If no tools configured, use the simple single-turn path
-    if (!this.toolRegistry || !this.toolExecutor) {
-      return this.singleTurn();
-    }
-
-    return this.toolLoop();
   }
 
   private async singleTurn(): Promise<string> {
+    this.throwIfCancelled();
+
     const request: ChatRequest = {
       messages: this.history,
       system: this.systemPrompt,
@@ -103,6 +122,7 @@ export class NativeAgent {
     };
 
     const response = await this.chatWithRouter(request);
+    this.throwIfCancelled();
 
     this._totalUsage.inputTokens += response.usage.inputTokens;
     this._totalUsage.outputTokens += response.usage.outputTokens;
@@ -159,6 +179,8 @@ export class NativeAgent {
 
     for (let iteration = 0; iteration < this.maxIterations; iteration++) {
       try {
+        this.throwIfCancelled();
+
         // Build request — cast loopMessages to Message[] because the underlying
         // model client will pass them through to the API which accepts structured content.
         const request = {
@@ -169,6 +191,7 @@ export class NativeAgent {
         };
 
         const response = await this.chatWithRouter(request);
+        this.throwIfCancelled();
 
         this._totalUsage.inputTokens += response.usage.inputTokens;
         this._totalUsage.outputTokens += response.usage.outputTokens;
@@ -234,6 +257,8 @@ export class NativeAgent {
         const toolResultBlocks: unknown[] = [];
         lastToolResults = [];
         for (const tc of toolCalls) {
+          this.throwIfCancelled();
+
           const internalName = this.toolRegistry!.getByApiName(tc.name)?.name ?? tc.name;
           this.onToolUse?.({ type: 'start', tool: internalName, args: tc.args });
 
@@ -280,6 +305,13 @@ export class NativeAgent {
           return breakMsg;
         }
       } catch (error) {
+        if (this.isAbortError(error)) {
+          const cancelledMsg = 'Operation cancelled by user.';
+          const assistantMsg: Message = { role: 'assistant', content: cancelledMsg };
+          this.addToHistory(assistantMsg);
+          return cancelledMsg;
+        }
+
         const errorMsg = `Error in tool loop (iteration ${iteration + 1}): ${error instanceof Error ? error.message : String(error)}`;
         const assistantMsg: Message = { role: 'assistant', content: errorMsg };
         this.addToHistory(assistantMsg);
@@ -363,4 +395,28 @@ export class NativeAgent {
   getAttachmentCollector(): OutboundAttachmentCollector | undefined {
     return this._attachmentCollector;
   }
+
+  cancel(): void {
+    if (this._runInProgress) {
+      this._cancelRequested = true;
+    }
+  }
+
+  isCancellable(): boolean {
+    return this._runInProgress;
+  }
+
+  private throwIfCancelled(): void {
+    if (!this._cancelRequested) {
+      return;
+    }
+
+    const error = new Error('Operation cancelled by user.');
+    error.name = 'AbortError';
+    throw error;
+  }
+
+  private isAbortError(error: unknown): boolean {
+    return error instanceof Error && error.name === 'AbortError';
+  }
 }