Do not regenerate prompt summary when only timestamp changes

Bug: 502891604
Change-Id: I04637039ec69f534de56c49e3e826fd3276fd421
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7761678
Auto-Submit: Kateryna Prokopenko <kprokopenko@chromium.org>
Commit-Queue: Kateryna Prokopenko <kprokopenko@chromium.org>
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>

Author: Kateryna Prokopenko

front_end/panels/ai_assistance/components/ChatView.test.ts

@@ -99,4 +99,39 @@ describeWithEnvironment('ChatView', () => {
       assert.exists(sideEffect);
     });
   });
+
+  describe('Caching', () => {
+    it('should cache the summary and not regenerate it if only the timestamp changes', async () => {
+      const generateSummaryStub = sinon.stub().resolves('Summary');
+      let capturedExportClick: (() => void)|undefined;
+      const customView = (input: AiAssistancePanel.ChatWidgetInput) => {
+        capturedExportClick = input.exportForAgentsClick;
+      };
+
+      const props = getProp({
+        generateConversationSummary: generateSummaryStub,
+        conversationMarkdown: '# Conversation\n\n**Export Timestamp (UTC):** 2026-04-15T10:00:00.000Z\n\n---\nContent',
+      });
+
+      const chat = new AiAssistancePanel.ChatView(props, customView);
+      renderElementIntoDOM(chat);
+
+      assert.exists(capturedExportClick);
+
+      // Trigger export first time
+      await capturedExportClick!();
+      sinon.assert.callCount(generateSummaryStub, 1);
+
+      // Update props with a new timestamp but same content
+      chat.props = getProp({
+        generateConversationSummary: generateSummaryStub,
+        conversationMarkdown: '# Conversation\n\n**Export Timestamp (UTC):** 2026-04-15T11:00:00.000Z\n\n---\nContent',
+      });
+
+      // Trigger export second time
+      await capturedExportClick!();
+      // Should still be 1 because of cache
+      sinon.assert.callCount(generateSummaryStub, 1);
+    });
+  });
 });

front_end/panels/ai_assistance/components/ChatView.ts

@@ -96,7 +96,7 @@ export interface Props {
   };
 }
 
-interface ChatWidgetInput extends Props {
+export interface ChatWidgetInput extends Props {
   handleScroll: (ev: Event) => void;
   handleSuggestionClick: (title: string) => void;
   handleMessageContainerRef: (el: Element|undefined) => void;
@@ -367,12 +367,13 @@ export class ChatView extends HTMLElement {
   };
 
   async #getSummary(): Promise<string> {
-    if (this.#cachedSummary?.markdown === this.#props.conversationMarkdown) {
+    const cacheKey = this.#props.conversationMarkdown.replace(/\*\*Export Timestamp \(UTC\):\*\* .*\n\n/, '');
+    if (this.#cachedSummary?.markdown === cacheKey) {
       return this.#cachedSummary.summary;
     }
     try {
       const summary = await this.#props.generateConversationSummary(this.#props.conversationMarkdown);
-      this.#cachedSummary = {markdown: this.#props.conversationMarkdown, summary};
+      this.#cachedSummary = {markdown: cacheKey, summary};
       return summary;
     } catch (err) {
       console.error(err);