feat: Add AbortSignal support for retry logic and tool execution (#9196)

Co-authored-by: Sandy Tao <sandytao520@icloud.com>

packages/core/src/core/coreToolScheduler.ts

@@ -1078,17 +1078,25 @@ export class CoreToolScheduler {
             }
           })
           .catch((executionError: Error) => {
-            this.setStatusInternal(
-              callId,
-              'error',
-              createErrorResponse(
-                scheduledCall.request,
-                executionError instanceof Error
-                  ? executionError
-                  : new Error(String(executionError)),
-                ToolErrorType.UNHANDLED_EXCEPTION,
-              ),
-            );
+            if (signal.aborted) {
+              this.setStatusInternal(
+                callId,
+                'cancelled',
+                'User cancelled tool execution.',
+              );
+            } else {
+              this.setStatusInternal(
+                callId,
+                'error',
+                createErrorResponse(
+                  scheduledCall.request,
+                  executionError instanceof Error
+                    ? executionError
+                    : new Error(String(executionError)),
+                  ToolErrorType.UNHANDLED_EXCEPTION,
+                ),
+              );
+            }
           });
       });
     }

packages/core/src/tools/mcp-tool.test.ts

@@ -572,6 +572,161 @@ describe('DiscoveredMCPTool', () => {
         'Here is a resource.\n[Link to My Resource: file:///path/to/resource]\nEmbedded text content.\n[Image: image/jpeg]',
       );
     });
+
+    describe('AbortSignal support', () => {
+      it('should abort immediately if signal is already aborted', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        controller.abort();
+
+        const invocation = tool.build(params);
+
+        await expect(invocation.execute(controller.signal)).rejects.toThrow(
+          'Tool call aborted',
+        );
+
+        // Tool should not be called if signal is already aborted
+        expect(mockCallTool).not.toHaveBeenCalled();
+      });
+
+      it('should abort during tool execution', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+
+        // Mock a delayed response to simulate long-running tool
+        mockCallTool.mockImplementation(
+          () =>
+            new Promise((resolve) => {
+              setTimeout(() => {
+                resolve([
+                  {
+                    functionResponse: {
+                      name: serverToolName,
+                      response: {
+                        content: [{ type: 'text', text: 'Success' }],
+                      },
+                    },
+                  },
+                ]);
+              }, 1000);
+            }),
+        );
+
+        const invocation = tool.build(params);
+        const promise = invocation.execute(controller.signal);
+
+        // Abort after a short delay to simulate cancellation during execution
+        setTimeout(() => controller.abort(), 50);
+
+        await expect(promise).rejects.toThrow('Tool call aborted');
+      });
+
+      it('should complete successfully if not aborted', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        const successResponse = [
+          {
+            functionResponse: {
+              name: serverToolName,
+              response: {
+                content: [{ type: 'text', text: 'Success' }],
+              },
+            },
+          },
+        ];
+
+        mockCallTool.mockResolvedValue(successResponse);
+
+        const invocation = tool.build(params);
+        const result = await invocation.execute(controller.signal);
+
+        expect(result.llmContent).toEqual([{ text: 'Success' }]);
+        expect(result.returnDisplay).toBe('Success');
+        expect(mockCallTool).toHaveBeenCalledWith([
+          { name: serverToolName, args: params },
+        ]);
+      });
+
+      it('should handle tool error even when abort signal is provided', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        const errorResponse = [
+          {
+            functionResponse: {
+              name: serverToolName,
+              response: { error: { isError: true } },
+            },
+          },
+        ];
+
+        mockCallTool.mockResolvedValue(errorResponse);
+
+        const invocation = tool.build(params);
+        const result = await invocation.execute(controller.signal);
+
+        expect(result.error?.type).toBe(ToolErrorType.MCP_TOOL_ERROR);
+        expect(result.returnDisplay).toContain(
+          `Error: MCP tool '${serverToolName}' reported an error.`,
+        );
+      });
+
+      it('should handle callTool rejection with abort signal', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        const expectedError = new Error('Network error');
+
+        mockCallTool.mockRejectedValue(expectedError);
+
+        const invocation = tool.build(params);
+
+        await expect(invocation.execute(controller.signal)).rejects.toThrow(
+          expectedError,
+        );
+      });
+
+      it('should cleanup event listeners properly on successful completion', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        const successResponse = [
+          {
+            functionResponse: {
+              name: serverToolName,
+              response: {
+                content: [{ type: 'text', text: 'Success' }],
+              },
+            },
+          },
+        ];
+
+        mockCallTool.mockResolvedValue(successResponse);
+
+        const invocation = tool.build(params);
+        await invocation.execute(controller.signal);
+
+        controller.abort();
+        expect(controller.signal.aborted).toBe(true);
+      });
+
+      it('should cleanup event listeners properly on error', async () => {
+        const params = { param: 'test' };
+        const controller = new AbortController();
+        const expectedError = new Error('Tool execution failed');
+
+        mockCallTool.mockRejectedValue(expectedError);
+
+        const invocation = tool.build(params);
+
+        try {
+          await invocation.execute(controller.signal);
+        } catch (error) {
+          expect(error).toBe(expectedError);
+        }
+
+        // Verify cleanup by aborting after error
+        controller.abort();
+        expect(controller.signal.aborted).toBe(true);
+      });
+    });
   });
 
   describe('shouldConfirmExecute', () => {

packages/core/src/tools/mcp-tool.ts

@@ -131,7 +131,7 @@ class DiscoveredMCPToolInvocation extends BaseToolInvocation<
     return false;
   }
 
-  async execute(): Promise<ToolResult> {
+  async execute(signal: AbortSignal): Promise<ToolResult> {
     const functionCalls: FunctionCall[] = [
       {
         name: this.serverToolName,
@@ -139,7 +139,36 @@ class DiscoveredMCPToolInvocation extends BaseToolInvocation<
       },
     ];
 
-    const rawResponseParts = await this.mcpTool.callTool(functionCalls);
+    // Race MCP tool call with abort signal to respect cancellation
+    const rawResponseParts = await new Promise<Part[]>((resolve, reject) => {
+      if (signal.aborted) {
+        const error = new Error('Tool call aborted');
+        error.name = 'AbortError';
+        reject(error);
+        return;
+      }
+      const onAbort = () => {
+        cleanup();
+        const error = new Error('Tool call aborted');
+        error.name = 'AbortError';
+        reject(error);
+      };
+      const cleanup = () => {
+        signal.removeEventListener('abort', onAbort);
+      };
+      signal.addEventListener('abort', onAbort, { once: true });
+
+      this.mcpTool
+        .callTool(functionCalls)
+        .then((res) => {
+          cleanup();
+          resolve(res);
+        })
+        .catch((err) => {
+          cleanup();
+          reject(err);
+        });
+    });
 
     // Ensure the response is not an error
     if (this.isMCPToolError(rawResponseParts)) {