chore(mcp): do not render page state when snapshot has not changed

Author: dgozman

packages/playwright/src/mcp/browser/response.ts

@@ -187,14 +187,16 @@ function renderTabSnapshot(tabSnapshot: TabSnapshot, options: { omitSnapshot?: b
     lines.push('');
   }
 
-  lines.push(`### Page state`);
-  lines.push(`- Page URL: ${tabSnapshot.url}`);
-  lines.push(`- Page Title: ${tabSnapshot.title}`);
-  lines.push(`- Page Snapshot:`);
-  lines.push('```yaml');
-  // TODO: perhaps not render page state when there are no changes?
-  lines.push(options.omitSnapshot ? '<snapshot>' : (tabSnapshot.ariaSnapshot || '<no changes>'));
-  lines.push('```');
+  if (tabSnapshot.ariaSnapshot) {
+    // Snapshot (diff) can be empty when nothing has changed.
+    lines.push(`### Page state`);
+    lines.push(`- Page URL: ${tabSnapshot.url}`);
+    lines.push(`- Page Title: ${tabSnapshot.title}`);
+    lines.push(`- Page Snapshot:`);
+    lines.push('```yaml');
+    lines.push(options.omitSnapshot ? '<snapshot>' : tabSnapshot.ariaSnapshot);
+    lines.push('```');
+  }
 
   return lines.join('\n');
 }

tests/mcp/snapshot-diff.spec.ts

@@ -63,10 +63,7 @@ test('should return aria snapshot diff', async ({ client, server }) => {
       ref: 'e3',
     },
   })).toHaveResponse({
-    pageState: expect.stringContaining(`Page Snapshot:
-\`\`\`yaml
-<no changes>
-\`\`\``),
+    pageState: expect.not.stringContaining(`Page Snapshot`),
   });
 
   expect(await client.callTool({