fix: forbid closing the last page

docs/tool-reference.md

@@ -116,7 +116,7 @@
 
 ### `close_page`
 
-**Description:** Closes the page by its index.
+**Description:** Closes the page by its index. The last open page cannot be closed.
 
 **Parameters:**
 

src/McpContext.ts

@@ -131,6 +131,16 @@ export class McpContext implements Context {
     this.#consoleCollector.addPage(page);
     return page;
   }
+  async closePage(pageIdx: number): Promise<void> {
+    if (this.#pages.length === 1) {
+      throw new Error(
+        'Unable to close the last page in the browser. It is fine to keep the last page open.',
+      );
+    }
+    const page = this.getPageByIdx(pageIdx);
+    this.setSelectedPageIdx(0);
+    await page.close({runBeforeUnload: false});
+  }
 
   getNetworkRequestByUrl(url: string): HTTPRequest {
     const requests = this.getNetworkRequests();

src/tools/ToolDefinition.ts

@@ -62,6 +62,7 @@ export type Context = Readonly<{
   clearDialog(): void;
   getPageByIdx(idx: number): Page;
   newPage(): Promise<Page>;
+  closePage(pageIdx: number): Promise<void>;
   setSelectedPageIdx(idx: number): void;
   getElementByUid(uid: string): Promise<ElementHandle<Element>>;
   setNetworkConditions(conditions: string | null): void;

src/tools/pages.ts

@@ -45,7 +45,7 @@ export const selectPage = defineTool({
 
 export const closePage = defineTool({
   name: 'close_page',
-  description: `Closes the page by its index.`,
+  description: `Closes the page by its index. The last open page cannot be closed.`,
   annotations: {
     category: ToolCategories.NAVIGATION_AUTOMATION,
     readOnlyHint: false,
@@ -58,9 +58,7 @@ export const closePage = defineTool({
       ),
   },
   handler: async (request, response, context) => {
-    const page = context.getPageByIdx(request.params.pageIdx);
-    context.setSelectedPageIdx(0);
-    await page.close({runBeforeUnload: false});
+    await context.closePage(request.params.pageIdx);
     response.setIncludePages(true);
   },
 });

tests/tools/pages.test.ts

@@ -53,6 +53,21 @@ describe('pages', () => {
         assert.ok(response.includePages);
       });
     });
+    it('cannot close the last page', async () => {
+      await withBrowser(async (response, context) => {
+        const page = context.getSelectedPage();
+        try {
+          await closePage.handler({params: {pageIdx: 0}}, response, context);
+          assert.fail('not reached');
+        } catch (err) {
+          assert.strictEqual(
+            err.message,
+            'Unable to close the last page in the browser. It is fine to keep the last page open.',
+          );
+        }
+        assert.ok(!page.isClosed());
+      });
+    });
   });
   describe('browser_select_page', () => {
     it('selects a page', async () => {