Don't reclassify an emptied chat session as never-used

src/vs/workbench/contrib/chat/common/model/chatSessionStore.ts

@@ -396,7 +396,7 @@ export class ChatSessionStore extends Disposable {
 
 			// Write succeeded, update index
 			const newMetadata = await getSessionMetadata(session);
-			index.entries[session.sessionId] = newMetadata;
+			index.entries[session.sessionId] = preserveNonEmpty(index.entries[session.sessionId], newMetadata);
 		} catch (e) {
 			this.reportError('sessionWrite', 'Error writing chat session', e);
 		}
@@ -413,7 +413,7 @@ export class ChatSessionStore extends Disposable {
 
 			// TODO get this class on sessionResource
 			const externalSessionId = session.sessionResource.toString();
-			index.entries[externalSessionId] = await getSessionMetadata(session);
+			index.entries[externalSessionId] = preserveNonEmpty(index.entries[externalSessionId], await getSessionMetadata(session));
 		} catch (e) {
 			this.reportError('sessionMetadataWrite', 'Error writing chat session metadata', e);
 		}
@@ -759,11 +759,11 @@ export class ChatSessionStore extends Disposable {
 	updateAndFlushIndexSync(localSessions: ChatModel[], externalSessions: ChatModel[]): void {
 		const index = this.internalGetIndex();
 		for (const session of localSessions) {
-			index.entries[session.sessionId] = getSessionMetadataSync(session);
+			index.entries[session.sessionId] = preserveNonEmpty(index.entries[session.sessionId], getSessionMetadataSync(session));
 		}
 		for (const session of externalSessions) {
 			const externalSessionId = session.sessionResource.toString();
-			index.entries[externalSessionId] = getSessionMetadataSync(session);
+			index.entries[externalSessionId] = preserveNonEmpty(index.entries[externalSessionId], getSessionMetadataSync(session));
 		}
 		try {
 			this.storageService.store(ChatIndexStorageKey, index, this.getIndexStorageScope(), StorageTarget.MACHINE);
@@ -893,6 +893,23 @@ function getSessionMetadataSync(session: ChatModel): IChatSessionEntryMetadata {
 	};
 }
 
+/**
+ * `isEmpty` exists to keep never-used sessions out of the history list, which
+ * filters on it. Removing every request from a session that *did* have them —
+ * restoring the checkpoint on the first request, for example — must therefore
+ * not re-classify it as never-used: doing so drops it from the list permanently
+ * even though its title and full transcript are still on disk, and makes it
+ * flicker in and out beforehand, since the live-model path applies no such
+ * filter.
+ */
+function preserveNonEmpty(previous: IChatSessionEntryMetadata | undefined, next: IChatSessionEntryMetadata): IChatSessionEntryMetadata {
+	if (next.isEmpty && previous && !previous.isEmpty) {
+		next.isEmpty = false;
+	}
+
+	return next;
+}
+
 async function getSessionMetadata(session: ChatModel | ISerializableChatData): Promise<IChatSessionEntryMetadata> {
 	if (session instanceof ChatModel) {
 		const metadata = getSessionMetadataSync(session);

src/vs/workbench/contrib/chat/test/common/model/chatSessionStore.test.ts

@@ -29,7 +29,7 @@ import { MockChatModel } from './mockChatModel.js';
 import { IConfigurationService } from '../../../../../../platform/configuration/common/configuration.js';
 import { TestConfigurationService } from '../../../../../../platform/configuration/test/common/testConfigurationService.js';
 
-function createMockChatModel(sessionResource: URI, options?: { customTitle?: string }): ChatModel {
+function createMockChatModel(sessionResource: URI, options?: { customTitle?: string; requestCount?: number }): ChatModel {
 	const sessionId = LocalChatSessionUri.parseLocalSessionId(sessionResource);
 	if (!sessionId) {
 		throw new Error('createMockChatModel requires a local session URI');
@@ -39,10 +39,18 @@ function createMockChatModel(sessionResource: URI, options?: { customTitle?: str
 	if (options?.customTitle) {
 		model.customTitle = options.customTitle;
 	}
+	if (options?.requestCount) {
+		setRequestCount(model, options.requestCount);
+	}
 	// Cast to ChatModel - the mock implements enough of the interface for testing
 	return model as unknown as ChatModel;
 }
 
+/** Only the request count matters for the index metadata under test. */
+function setRequestCount(model: MockChatModel, count: number): void {
+	model.requests = Array.from({ length: count }, () => ({} as MockChatModel['requests'][number]));
+}
+
 class MockWorkspaceEditingService extends Disposable implements Partial<IWorkspaceEditingService> {
 	private readonly _onDidEnterWorkspace = this._register(new Emitter<IDidEnterWorkspaceEvent>());
 	readonly onDidEnterWorkspace = this._onDidEnterWorkspace.event;
@@ -183,6 +191,32 @@ suite('ChatSessionStore', () => {
 		assert.strictEqual(index['session-1'].title, 'My Custom Title');
 	});
 
+	test('storeSessions marks a session with no requests as empty', async () => {
+		const store = createChatSessionStore();
+		const model = testDisposables.add(createMockChatModel(LocalChatSessionUri.forSession('session-1')));
+
+		await store.storeSessions([model]);
+
+		const index = await store.getIndex();
+		assert.strictEqual(index['session-1'].isEmpty, true);
+	});
+
+	test('storeSessions keeps a session non-empty after all of its requests are removed', async () => {
+		const store = createChatSessionStore();
+		const model = testDisposables.add(createMockChatModel(LocalChatSessionUri.forSession('session-1'), { requestCount: 2 }));
+
+		await store.storeSessions([model]);
+		assert.strictEqual((await store.getIndex())['session-1'].isEmpty, false);
+
+		// Restoring the checkpoint on the first request removes every request.
+		// The session still has its title and transcript on disk, so it must not
+		// be reclassified as never-used and filtered out of the history list.
+		setRequestCount(model as unknown as MockChatModel, 0);
+		await store.storeSessions([model]);
+
+		assert.strictEqual((await store.getIndex())['session-1'].isEmpty, false);
+	});
+
 	test('readSession returns stored session data', async () => {
 		const store = createChatSessionStore();
 		const model = testDisposables.add(createMockChatModel(LocalChatSessionUri.forSession('session-1')));

src/vs/workbench/contrib/chat/test/common/model/mockChatModel.ts

@@ -19,6 +19,7 @@ export class MockChatModel extends Disposable implements IChatModel {
 	readonly timestamp = 0;
 	readonly timing: IChatSessionTiming = { created: Date.now(), lastRequestStarted: undefined, lastRequestEnded: undefined };
 	readonly initialLocation = ChatAgentLocation.Chat;
+	readonly sessionTypeSelectionReason = undefined;
 	readonly title = '';
 	readonly hasCustomTitle = false;
 	customTitle: string | undefined;
@@ -67,7 +68,7 @@ export class MockChatModel extends Disposable implements IChatModel {
 	}
 
 	startEditingSession(isGlobalEditingSession?: boolean, transferFromSession?: IChatEditingSession): void { }
-	getRequests(): IChatRequestModel[] { return []; }
+	getRequests(): IChatRequestModel[] { return this.requests; }
 	setCheckpoint(requestId: string | undefined): void { }
 	setRepoData(data: IExportableRepoData | undefined): void { this.repoData = data; }
 	workingDirectory: URI | undefined = undefined;