Add chatSessionId to chat.modelChange telemetry

src/vs/workbench/contrib/chat/browser/widget/input/chatInputPart.ts

@@ -91,7 +91,7 @@ import { ILanguageModelChatMetadata, ILanguageModelChatMetadataAndIdentifier, IL
 import { ChatModelConfigurationStore } from './chatModelConfigurationStore.js';
 import { IChatModelInputState, IChatRequestModeInfo, IInputModel, logChangesToStateModel } from '../../../common/model/chatModel.js';
 import { filterModelsForSession, findBestMatchingModel, findDefaultModel, hasModelsTargetingSession, isModelValidForSession, mergeModelsWithCache, resolveModelFromSyncState, shouldResetModelToDefault, shouldResetOnModelListChange, shouldRestoreLateArrivingModel, shouldRestorePersistedModel } from './chatModelSelectionLogic.js';
-import { getChatSessionType, LocalChatSessionUri } from '../../../common/model/chatUri.js';
+import { chatSessionResourceToId, getChatSessionType, LocalChatSessionUri } from '../../../common/model/chatUri.js';
 import { IChatResponseViewModel, isResponseVM } from '../../../common/model/chatViewModel.js';
 import { IChatAgentService } from '../../../common/participants/chatAgents.js';
 import { ILanguageModelToolsService } from '../../../common/tools/languageModelToolsService.js';
@@ -1044,6 +1044,10 @@ export class ChatInputPart extends Disposable implements IHistoryNavigationWidge
 				return !sessionType || sessionType === localChatSessionType || isAgentHostTarget(sessionType);
 			},
 			showAutoModel: () => this._showAutoModel(),
+			getChatSessionId: () => {
+				const sessionResource = this._widget?.viewModel?.model.sessionResource;
+				return sessionResource ? chatSessionResourceToId(sessionResource) : undefined;
+			},
 			modelConfiguration: this._modelConfigStore,
 		};
 	}

src/vs/workbench/contrib/chat/browser/widget/input/chatModelPicker.ts

@@ -154,11 +154,13 @@ type ChatModelChangeClassification = {
 	comment: 'Reporting when the model picker is switched';
 	fromModel?: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The previous chat model' };
 	toModel: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The new chat model' };
+	chatSessionId?: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'The id of the current chat session, used to correlate the model switch with the session.' };
 };
 
 type ChatModelChangeEvent = {
 	fromModel: string | TelemetryTrustedValue<string> | undefined;
 	toModel: string | TelemetryTrustedValue<string>;
+	chatSessionId?: string;
 };
 
 type ChatModelPickerInteraction = 'disabledModelContactAdminClicked' | 'premiumModelUpgradePlanClicked' | 'otherModelsExpanded' | 'otherModelsCollapsed';
@@ -1104,7 +1106,8 @@ export class ModelPickerWidget extends Disposable {
 		const onSelect = (model: ILanguageModelChatMetadataAndIdentifier) => {
 			this._telemetryService.publicLog2<ChatModelChangeEvent, ChatModelChangeClassification>('chat.modelChange', {
 				fromModel: previousModel?.metadata.vendor === 'copilot' ? new TelemetryTrustedValue(previousModel.identifier) : 'unknown',
-				toModel: model.metadata.vendor === 'copilot' ? new TelemetryTrustedValue(model.identifier) : 'unknown'
+				toModel: model.metadata.vendor === 'copilot' ? new TelemetryTrustedValue(model.identifier) : 'unknown',
+				chatSessionId: this._delegate.getChatSessionId?.()
 			});
 			this._selectedModel = model;
 			this._renderLabel();

src/vs/workbench/contrib/chat/browser/widget/input/modelPickerActionItem.ts

@@ -55,6 +55,13 @@ export interface IModelPickerDelegate {
 	 * Student users) instead of an Auto entry.
 	 */
 	showAutoModel?(): boolean;
+	/**
+	 * The id of the current chat session, used to correlate model-picker
+	 * changes with the session in telemetry. Matches the `chatSessionId`
+	 * reported by other chat telemetry events (e.g. the chat request event).
+	 * Returns `undefined` when no session is active.
+	 */
+	getChatSessionId?(): string | undefined;
 	/**
 	 * Per-editor model configuration access. When omitted, the picker reads and
 	 * writes configuration through the global {@link ILanguageModelsService}.