chat: persist timing for contiguous reasoning runs

src/vs/platform/agentHost/common/sessionDataService.ts

@@ -9,7 +9,7 @@ import { URI } from '../../../base/common/uri.js';
 import { createDecorator } from '../../instantiation/common/instantiation.js';
 import { Event } from '../../../base/common/event.js';
 import { getLargeFileConfirmationLimit } from '../../files/common/files.js';
-import type { FileEditKind, Message } from './state/sessionState.js';
+import type { FileEditKind, MarkdownResponsePart, Message, ReasoningResponsePart, ResponsePartKind } from './state/sessionState.js';
 
 export const ISessionDataService = createDecorator<ISessionDataService>('sessionDataService');
 
@@ -98,6 +98,9 @@ export interface IReviewedFileRecord {
 
 // ---- Session database ---------------------------------------------------
 
+/** Ordered response text with stable reasoning-run identities and references to provider-owned tool results. */
+export type StoredAssistantResponsePart = MarkdownResponsePart | ReasoningResponsePart | { readonly kind: ResponsePartKind.ToolCall; readonly toolCallId: string };
+
 /** A host-persisted turn that is absent from the provider transcript. */
 export interface IPersistedTurnRecord {
 	/** Whether this is host-local or a provider turn that failed before persistence. */
@@ -266,6 +269,12 @@ export interface ISessionDatabase extends IDisposable {
 	 */
 	getTurnUsages(): Promise<Map<string, string>>;
 
+	/** Records a response's observed part ordering and reasoning timings with the owning turn's pruning lifecycle. */
+	setAssistantResponseParts(turnId: string, responseId: string, parts: readonly StoredAssistantResponsePart[]): Promise<void>;
+
+	/** Reads recorded parts keyed by durable provider response id, after all previously submitted writes. */
+	getAssistantResponseParts(): Promise<Map<string, readonly StoredAssistantResponsePart[]>>;
+
 	/**
 	 * Persists the JSON-serialized delegation metadata for an agent-authored turn.
 	 * Idempotent — last writer wins per turn.

src/vs/platform/agentHost/common/state/protocol/.ahp-version

@@ -1 +1 @@
-5872a476
+d7a5579b

src/vs/platform/agentHost/common/state/protocol/channels-chat/actions.ts

@@ -678,7 +678,8 @@ export interface ChatUsageAction {
  * Reasoning/thinking text from the model, appended to a specific reasoning response part.
  *
  * The server MUST first emit a `chat/responsePart` to create the target
- * reasoning part, then use this action to append text to it.
+ * reasoning part, then use this action to append text or record its timing.
+ * An empty `content` updates only the supplied timing fields.
  *
  * @category Chat Actions
  * @version 1
@@ -691,6 +692,10 @@ export interface ChatReasoningAction {
 	partId: string;
 	/** Reasoning text chunk */
 	content: string;
+	/** Producer-recorded ISO 8601 start of the reasoning interval; omitted to preserve the existing value. */
+	startedAt?: string;
+	/** Final elapsed reasoning time in non-negative integer milliseconds, measured by the producer's clock; omitted to preserve the existing value. Zero is a recorded duration, not unknown. */
+	duration?: number;
 	/**
 	 * Additional provider-specific metadata for this action.
 	 *

src/vs/platform/agentHost/common/state/protocol/channels-chat/reducer.ts

@@ -763,7 +763,12 @@ export function chatReducer(state: ChatState, action: ChatAction, log?: (msg: st
 		case ActionType.ChatReasoning:
 			return updateResponsePart(state, action.turnId, action.partId, part => {
 				if (part.kind === ResponsePartKind.Reasoning) {
-					return { ...part, content: part.content + action.content };
+					return {
+						...part,
+						content: part.content + action.content,
+						...(action.startedAt !== undefined ? { startedAt: action.startedAt } : {}),
+						...(action.duration !== undefined ? { duration: action.duration } : {}),
+					};
 				}
 				return part;
 			});

src/vs/platform/agentHost/common/state/protocol/channels-chat/state.ts

@@ -1131,6 +1131,10 @@ export interface ReasoningResponsePart {
 	id: string;
 	/** Accumulated reasoning text */
 	content: string;
+	/** Producer-recorded ISO 8601 start of this reasoning interval; absent when unknown. */
+	startedAt?: string;
+	/** Final elapsed reasoning time in non-negative integer milliseconds, measured by the producer's clock; absent while unfinished or unknown. Clients MUST NOT derive it from their own clock. */
+	duration?: number;
 }
 
 /**

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

@@ -72,6 +72,14 @@ export class CompatibleSessionDatabase implements ISessionDatabase {
 		return result;
 	}
 
+	async setAssistantResponseParts(...args: Parameters<ISessionDatabase['setAssistantResponseParts']>): ReturnType<ISessionDatabase['setAssistantResponseParts']> {
+		return this.raw.setAssistantResponseParts(...args);
+	}
+
+	async getAssistantResponseParts(): ReturnType<ISessionDatabase['getAssistantResponseParts']> {
+		return this.raw.getAssistantResponseParts();
+	}
+
 	async getTurnDelegations(...[]: Parameters<ISessionDatabase['getTurnDelegations']>): ReturnType<ISessionDatabase['getTurnDelegations']> {
 		const result = await this.raw.getTurnDelegations();
 		return new Map([...result].map(([key, value]) => [key, this.identity.metadata('agentHost.turnDelegation', value, 'runtime')!]));

src/vs/platform/agentHost/node/copilot/buildSessionEvents.ts

@@ -6,7 +6,7 @@
 import type { JsonValue, SessionEvent } from '@github/copilot-sdk';
 import { isObject } from '../../../../base/common/types.js';
 import { generateUuid, isUUID } from '../../../../base/common/uuid.js';
-import { getInlineToolInput, ResponsePartKind, ToolCallStatus, ToolResultContentType, TurnState, type ToolCallCompletedState, type ToolResultContent, type ToolResultSubagentContent, type Turn } from '../../common/state/sessionState.js';
+import { getInlineToolInput, ResponsePartKind, ToolCallStatus, ToolResultContentType, TurnState, type MarkdownResponsePart, type ReasoningResponsePart, type ToolCallCompletedState, type ToolResultContent, type ToolResultSubagentContent, type Turn } from '../../common/state/sessionState.js';
 
 /**
  * Default schema version stamped on the synthesized `session.start` event.
@@ -44,6 +44,8 @@ export interface IBuildSessionEventsOptions {
 	readonly schemaVersion?: number;
 	/** Base time for the synthesized (monotonically increasing) event timestamps. Defaults to now. */
 	readonly startTime?: Date;
+	/** Associates original response parts with their synthesized user-turn and assistant-event IDs. */
+	readonly onAssistantMessage?: (turnId: string, responseId: string, parts: readonly (MarkdownResponsePart | ReasoningResponsePart)[]) => void;
 }
 
 /**
@@ -167,8 +169,9 @@ export function buildSessionEventsFromTurns(turns: readonly Turn[], options: IBu
 		// UUID (the runtime rejects non-UUID event ids) so the reconstructed turn
 		// keeps the id the SDK's fork/truncate RPCs address and a caller can seed
 		// a matching protocol turn; otherwise mint a fresh UUID.
+		const turnId = isUUID(turn.id) ? turn.id : generateUuid();
 		push({
-			id: isUUID(turn.id) ? turn.id : generateUuid(),
+			id: turnId,
 			parentId,
 			timestamp: nextTimestamp(),
 			type: 'user.message',
@@ -180,12 +183,14 @@ export function buildSessionEventsFromTurns(turns: readonly Turn[], options: IBu
 
 		let markdown = '';
 		let reasoning = '';
+		let parts: (MarkdownResponsePart | ReasoningResponsePart)[] = [];
 		const flushAssistantMessage = (): void => {
 			if (!markdown && !reasoning) {
 				return;
 			}
+			const responseId = generateUuid();
 			push({
-				id: generateUuid(),
+				id: responseId,
 				parentId,
 				timestamp: nextTimestamp(),
 				type: 'assistant.message',
@@ -196,8 +201,10 @@ export function buildSessionEventsFromTurns(turns: readonly Turn[], options: IBu
 					...(options.model ? { model: options.model } : {}),
 				},
 			});
+			options.onAssistantMessage?.(turnId, responseId, parts);
 			markdown = '';
 			reasoning = '';
+			parts = [];
 		};
 
 		for (const part of turn.responseParts) {
@@ -210,11 +217,13 @@ export function buildSessionEventsFromTurns(turns: readonly Turn[], options: IBu
 					flushAssistantMessage();
 				}
 				markdown += part.content;
+				parts.push({ ...part });
 			} else if (part.kind === ResponsePartKind.Reasoning) {
 				if (markdown) {
 					flushAssistantMessage();
 				}
 				reasoning += part.content;
+				parts.push({ ...part });
 			} else if (part.kind === ResponsePartKind.ToolCall && part.toolCall.status === ToolCallStatus.Completed) {
 				// Flush accumulated assistant text before the tool call so the
 				// reconstructed part order matches the original interleaving.

src/vs/platform/agentHost/node/copilot/copilotAgent.ts

@@ -69,7 +69,7 @@ import { AhpErrorCodes, AHP_SESSION_NOT_FOUND, JsonRpcErrorCodes, ProtocolError
 import { ICopilotConfigSlashCommandState } from '../../common/copilotConfigSlashCommands.js';
 import { ICopilotHomeService } from '../../../environment/common/copilotHome.js';
 import { CopilotCustomizationInstallations } from './customizations/copilotCustomizationInstallations.js';
-import { ISessionDataService, SESSION_DB_FILENAME, type ISessionDatabase } from '../../common/sessionDataService.js';
+import { ISessionDataService, SESSION_DB_FILENAME, type ISessionDatabase, type StoredAssistantResponsePart } from '../../common/sessionDataService.js';
 import { IAgentHostProxyResolver } from '../agentHostProxyResolver.js';
 import { writeUserDataCertificatesFile } from '../../../request/node/certificates.js';
 import { MODEL_REFRESH_BASE_DELAY_MS, MODEL_REFRESH_MAX_ATTEMPTS, MODEL_REFRESH_MAX_DELAY_MS, modelRefreshBackoff } from '../shared/modelRefreshRetry.js';
@@ -79,7 +79,7 @@ import { ProtectedResourceMetadata, type AgentCustomization, type AgentSelection
 import { ActionType, AuthRequiredReason, type AuthRequiredParams, type SessionAction } from '../../common/state/sessionActions.js';
 import { areAdditionalWorkingDirectoriesEqual } from '../../common/state/sessionWorkingDirectories.js';
 import { getRepositoryRootFromWorktree } from '../../common/worktreePaths.js';
-import { CustomizationLoadStatus, CustomizationType, ChatInputResponseKind, customizationId, buildChatUri, AH_META_WORKSPACELESS_DB_KEY, AH_META_IS_ARCHIVED_DB_KEY, AH_META_IS_DONE_DB_KEY, AH_META_EHCLI_ADOPTED_DB_KEY, AH_META_EHCLI_LAST_TURN_DB_KEY, AH_META_IS_READ_DB_KEY, SessionStatus, withSessionEhcliAdoptable, withSessionStatusFlag, withSessionWorkspaceless, type ChildCustomization, type ClientPluginCustomization, type Customization, type DirectoryCustomization, type ISessionFolderPickerDecision, type MessageAttachment, type PendingMessage, type PluginCustomization, type PolicyState, type ChatInputAnswer, type ToolCallResult, type Turn, type UsageInfo } from '../../common/state/sessionState.js';
+import { CustomizationLoadStatus, CustomizationType, ChatInputResponseKind, customizationId, buildChatUri, AH_META_WORKSPACELESS_DB_KEY, AH_META_IS_ARCHIVED_DB_KEY, AH_META_IS_DONE_DB_KEY, AH_META_EHCLI_ADOPTED_DB_KEY, AH_META_EHCLI_LAST_TURN_DB_KEY, AH_META_IS_READ_DB_KEY, ResponsePartKind, SessionStatus, withSessionEhcliAdoptable, withSessionStatusFlag, withSessionWorkspaceless, type ChildCustomization, type ClientPluginCustomization, type Customization, type DirectoryCustomization, type ISessionFolderPickerDecision, type MessageAttachment, type PendingMessage, type PluginCustomization, type PolicyState, type ChatInputAnswer, type ToolCallResult, type Turn, type UsageInfo } from '../../common/state/sessionState.js';
 import { CopilotChatDiscovery, ICopilotChatDiscoveryScan } from './copilotChatDiscovery.js';
 import { getByokLmAgentModelId, resolveByokLmEnablement } from '../../common/agentHostByokLm.js';
 import { isCustomizationEnabled } from '../../common/customizationEnablement.js';
@@ -6031,13 +6031,29 @@ export class CopilotAgent extends Disposable implements IAgent {
 			// so the git probe and file I/O overlap on the session-creation path.
 			const projectPromise = projectFromCopilotContext({ cwd: workingDirectory.fsPath }, this._gitService);
 			const eventsPath = resourceJoinPath(this._copilotHomeService.home, 'session-state', sessionId, 'events.jsonl').fsPath;
+			const responses: { turnId: string; responseId: string; parts: readonly StoredAssistantResponsePart[] }[] = [];
 			const jsonl = buildSessionEventLogFromTurns(importConfig.turns, {
 				sessionId,
 				workingDirectory: workingDirectory.fsPath,
 				model: model?.id,
+				onAssistantMessage: (turnId, responseId, parts) => {
+					if (parts.some(part => part.kind === ResponsePartKind.Reasoning)) {
+						responses.push({ turnId, responseId, parts });
+					}
+				},
 			});
 			await fs.mkdir(dirname(eventsPath), { recursive: true });
 			await fs.writeFile(eventsPath, jsonl, 'utf8');
+			if (responses.length) {
+				const reference = this._sessionDataService.openDatabase(this._resolveChatStorageScope(chat));
+				try {
+					for (const response of responses) {
+						await reference.object.setAssistantResponseParts(response.turnId, response.responseId, response.parts);
+					}
+				} finally {
+					reference.dispose();
+				}
+			}
 
 			// Persist metadata before resume so `_resumeSession` can resolve the
 			// working directory and model.
@@ -7654,6 +7670,7 @@ export class CopilotAgent extends Disposable implements IAgent {
 			try {
 				const backing = this._chatBackings.get(context.chatKey);
 				const result = await mapSessionEvents(context.resource, reference.object, events, context.chat, context.ownerSession, {
+					logService: this._logService,
 					workingDirectory: metadata.workingDirectory,
 					clientToolNames: new Set(this._activeClients.get(context.ownerSession)?.toolSet.merged().map(tool => tool.name) ?? []),
 					model: backing?.model ?? metadata.model,