fix: handle errors due to open dialogs during tool calls

src/WaitForHelper.ts

@@ -128,8 +128,10 @@ export class WaitForHelper {
     action: () => Promise<unknown>,
     options?: {timeout?: number; handleDialog?: 'accept' | 'dismiss' | string},
   ): Promise<void> {
+    let dialogOpened = false;
     if (options?.handleDialog) {
       const dialogHandler = (dialog: Pick<Dialog, 'accept' | 'dismiss'>) => {
+        dialogOpened = true;
         if (options.handleDialog === 'dismiss') {
           void dialog.dismiss();
         } else if (options.handleDialog === 'accept') {
@@ -167,6 +169,10 @@ export class WaitForHelper {
     try {
       await navigationFinished;
 
+      if (dialogOpened) {
+        return;
+      }
+
       // Wait for stable dom after navigation so we execute in
       // the correct context
       await this.waitForStableDom();

src/index.ts

@@ -240,14 +240,25 @@ export async function createMcpServer(
                 ? context.getPageById(params.pageId)
                 : context.getSelectedMcpPage();
             response.setPage(page);
-            await tool.handler(
-              {
-                params,
-                page,
-              },
-              response,
-              context,
-            );
+            try {
+              await tool.handler(
+                {
+                  params,
+                  page,
+                },
+                response,
+                context,
+              );
+            } catch (error) {
+              const dialog = page.getDialog();
+              if (dialog) {
+                response.appendResponseLine(
+                  `[Blocked] Action triggered a dialog.`,
+                );
+              } else {
+                throw error;
+              }
+            }
           } else {
             await tool.handler(
               // @ts-expect-error types do not match.

tests/index.test.ts

@@ -245,6 +245,38 @@ describe('e2e', () => {
       },
     );
   });
+
+  it('returns blocked message when dialog is opened during tool execution', async () => {
+    await withClient(async client => {
+      // Navigate to a page with a button that triggers a dialog on click
+      await client.callTool({
+        name: 'new_page',
+        arguments: {
+          url: `data:text/html,<button id="test" onclick="alert('test dialog')">Click me</button>`,
+        },
+      });
+
+      const snapshotResult = await client.callTool({
+        name: 'take_snapshot',
+        arguments: {},
+      });
+
+      const snapshotText = (snapshotResult.content as TextContent[])[0].text;
+      const match = snapshotText.match(/uid=(\d+_\d+)\s+button "Click me"/);
+      const uid = match ? match[1] : '1_1';
+
+      // Trigger the dialog
+      const result = await client.callTool({
+        name: 'click',
+        arguments: {
+          uid,
+        },
+      });
+
+      const content = result.content as TextContent[];
+      assert.match(content[0].text, /\[Blocked\] Action triggered a dialog\./);
+    });
+  });
 });
 
 async function getToolsWithFilteredCategories(