agentHost: polish: skip side-chat rename round-trip

Keep the deterministic side-question title while avoiding an unnecessary model-tool-model cycle before the answer.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: f48399f6-8524-4cb1-b187-d7f3eb899620

src/vs/platform/agentHost/node/agentHostSessionTitleController.ts

@@ -11,6 +11,7 @@ import { ILogService } from '../../log/common/log.js';
 import { ISessionDataService } from '../common/sessionDataService.js';
 import { SessionServerToolName } from '../common/serverToolNames.js';
 import { ActionType } from '../common/state/sessionActions.js';
+import { ChatOriginKind } from '../common/state/protocol/state.js';
 import { buildDefaultChatUri, isAhpChatChannel, isDefaultChatUri, type Turn, type URI as ProtocolURI } from '../common/state/sessionState.js';
 import { buildConversationContext, renderResponseMarkdown, truncateMiddle } from '../common/agentHostConversationContext.js';
 import { AgentHostStateManager } from './agentHostStateManager.js';
@@ -448,6 +449,9 @@ export class AgentHostSessionTitleController extends Disposable {
 			return undefined;
 		}
 		const independentChat = this._independentChatChannel(channel, chatChannel);
+		if (independentChat && this._stateManager.getChatOrigin(independentChat)?.kind === ChatOriginKind.SideChat) {
+			return undefined;
+		}
 		const key = independentChat ?? channel;
 		if (this._renamedTitles.has(key)) {
 			return undefined;

src/vs/platform/agentHost/test/node/agentHostSessionTitleController.test.ts

@@ -13,6 +13,7 @@ import { NullLogService } from '../../../log/common/log.js';
 import { AgentHostStateManager } from '../../node/agentHostStateManager.js';
 import { AgentHostSessionTitleController } from '../../node/agentHostSessionTitleController.js';
 import { ActionType } from '../../common/state/sessionActions.js';
+import { ChatOriginKind } from '../../common/state/protocol/state.js';
 import { buildChatUri, buildDefaultChatUri, MessageKind, ResponsePartKind, SessionStatus, ToolCallConfirmationReason, ToolCallStatus, TurnState, type ResponsePart, type SessionSummary, type ToolCallCompletedState, type Turn } from '../../common/state/sessionState.js';
 import { type AutoMergeMethod, type CreatedPullRequest, type GitHubIssueOrPullRequest, type IAgentHostOctoKitService } from '../../node/shared/agentHostOctoKitService.js';
 import { type ICopilotApiService, type ICopilotApiServiceRequestOptions, type ICopilotUtilityChatCompletionRequest } from '../../node/shared/copilotApiService.js';
@@ -269,6 +270,27 @@ suite('AgentHostSessionTitleController', () => {
 		});
 	});
 
+	test('active-agent mode keeps the fallback title without a rename reminder for side chats', async () => {
+		const { controller, stateManager, session } = setup(undefined, 'Session title', undefined, undefined, undefined, undefined, undefined, true);
+		const chat = buildChatUri(session.toString(), 'side-chat');
+		stateManager.addChat(session.toString(), chat, {
+			origin: {
+				kind: ChatOriginKind.SideChat,
+				chat: buildDefaultChatUri(session),
+				turnId: 'turn-1',
+			},
+		});
+		controller.seedTitleFromFirstMessage(session.toString(), 'salut', chat);
+
+		assert.deepStrictEqual({
+			title: stateManager.getChatState(chat)?.title,
+			instruction: await controller.prepareInstructionForAgent(session.toString(), chat),
+		}, {
+			title: 'salut',
+			instruction: undefined,
+		});
+	});
+
 	test('clearSession releases session and peer-chat rename state', async () => {
 		const { controller, stateManager, session, db } = setup(undefined, '', undefined, undefined, undefined, undefined, undefined, true);
 		const defaultChat = buildDefaultChatUri(session);