refactor(agent): consolidate harness session abstraction

2026-05-03 22:01:40 +02:00
parent e612149369
commit cdde2e893d
12 changed files with 599 additions and 397 deletions
--- a/packages/agent/src/harness/agent-harness.ts
+++ b/packages/agent/src/harness/agent-harness.ts
@@ -19,7 +19,7 @@ import type {
 	ExecutionEnv,
 	NavigateTreeResult,
 	PromptTemplate,
-	SessionTree,
+	Session,
 	Skill,
 	SystemPromptInputs,
 } from "./types.js";
@@ -56,7 +56,7 @@ export class DefaultAgentHarness implements AgentHarness {
 	readonly conversation: AgentHarnessConversationState;
 	readonly operation: AgentHarnessOperationState;

-	private sessionTree: SessionTree;
+	private session: Session;
 	private promptTemplates: PromptTemplate[];
 	private skills: Skill[];
 	private requestAuth?: AgentHarnessOptions["requestAuth"];
@@ -70,7 +70,7 @@ export class DefaultAgentHarness implements AgentHarness {
 	constructor(options: AgentHarnessOptions) {
 		this.agent = options.agent;
 		this.env = options.env;
-		this.sessionTree = options.sessionTree;
+		this.session = options.session;
 		this.promptTemplates = options.promptTemplates ?? [];
 		this.skills = options.skills ?? [];
 		this.requestAuth = options.requestAuth;
@@ -78,7 +78,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			this.toolRegistry.set(tool.name, tool);
 		}
 		this.conversation = {
-			sessionTree: options.sessionTree,
+			session: options.session,
 			model: options.initialModel ?? this.agent.state.model,
 			thinkingLevel: options.initialThinkingLevel ?? this.agent.state.thinkingLevel,
 			activeToolNames: options.initialActiveToolNames ?? this.agent.state.tools.map((tool) => tool.name),
@@ -191,7 +191,7 @@ export class DefaultAgentHarness implements AgentHarness {
 	}

 	private async syncFromTree(): Promise<void> {
-		const context = await this.sessionTree.buildContext();
+		const context = await this.session.buildContext();
 		this.agent.state.messages = context.messages;
 		if (context.model && this.conversation.model) {
 			// leave active model untouched; harness-level model is source of truth
@@ -201,7 +201,7 @@ export class DefaultAgentHarness implements AgentHarness {

 	private async applyPendingMutations(): Promise<void> {
 		for (const message of this.operation.pendingMutations.appendMessages) {
-			await this.sessionTree.appendMessage(message);
+			await this.session.appendMessage(message);
 		}
 		this.operation.pendingMutations.appendMessages = [];

@@ -210,7 +210,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			const previousModel = this.conversation.model;
 			this.conversation.model = model;
 			this.agent.state.model = model;
-			await this.sessionTree.appendModelChange(model.provider, model.id);
+			await this.session.appendModelChange(model.provider, model.id);
 			await this.emitOwn({ type: "model_select", model, previousModel, source: "set" });
 			this.operation.pendingMutations.model = undefined;
 		}
@@ -220,7 +220,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			const previousLevel = this.conversation.thinkingLevel;
 			this.conversation.thinkingLevel = level;
 			this.agent.state.thinkingLevel = level;
-			await this.sessionTree.appendThinkingLevelChange(level);
+			await this.session.appendThinkingLevelChange(level);
 			await this.emitOwn({ type: "thinking_level_select", level, previousLevel });
 			this.operation.pendingMutations.thinkingLevel = undefined;
 		}
@@ -258,7 +258,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			}
 		}
 		if (event.type === "message_end") {
-			await this.sessionTree.appendMessage(event.message);
+			await this.session.appendMessage(event.message);
 		}
 		if (event.type === "turn_end") {
 			const hadPendingMutations =
@@ -342,7 +342,7 @@ export class DefaultAgentHarness implements AgentHarness {

 	async appendMessage(message: AgentMessage): Promise<void> {
 		if (this.operation.idle) {
-			await this.sessionTree.appendMessage(message);
+			await this.session.appendMessage(message);
 			await this.syncFromTree();
 		} else {
 			this.operation.pendingMutations.appendMessages.push(message);
@@ -371,7 +371,7 @@ export class DefaultAgentHarness implements AgentHarness {
 		if (!model) throw new Error("No model set for compaction");
 		const auth = await this.requestAuth?.(model);
 		if (!auth) throw new Error("No auth available for compaction");
-		const branchEntries = await this.sessionTree.getBranch();
+		const branchEntries = await this.session.getBranch();
 		const preparation = prepareCompaction(branchEntries, DEFAULT_COMPACTION_SETTINGS);
 		if (!preparation) throw new Error("Nothing to compact");
 		const hookResult = await this.emitHook("session_before_compact", {
@@ -394,14 +394,14 @@ export class DefaultAgentHarness implements AgentHarness {
 				undefined,
 				this.conversation.thinkingLevel,
 			));
-		const entryId = await this.sessionTree.appendCompaction(
+		const entryId = await this.session.appendCompaction(
 			result.summary,
 			result.firstKeptEntryId,
 			result.tokensBefore,
 			result.details,
 			provided !== undefined,
 		);
-		const entry = await this.sessionTree.getEntry(entryId);
+		const entry = await this.session.getEntry(entryId);
 		await this.syncFromTree();
 		if (entry?.type === "compaction") {
 			await this.emitOwn({ type: "session_compact", compactionEntry: entry, fromHook: provided !== undefined });
@@ -414,11 +414,11 @@ export class DefaultAgentHarness implements AgentHarness {
 		options?: { summarize?: boolean; customInstructions?: string; replaceInstructions?: boolean; label?: string },
 	): Promise<NavigateTreeResult> {
 		if (!this.operation.idle) throw new Error("navigateTree() requires idle harness");
-		const oldLeafId = await this.sessionTree.getLeafId();
+		const oldLeafId = await this.session.getLeafId();
 		if (oldLeafId === targetId) return { cancelled: false };
-		const targetEntry = await this.sessionTree.getEntry(targetId);
+		const targetEntry = await this.session.getEntry(targetId);
 		if (!targetEntry) throw new Error(`Entry ${targetId} not found`);
-		const { entries, commonAncestorId } = await collectEntriesForBranchSummary(this.sessionTree, oldLeafId, targetId);
+		const { entries, commonAncestorId } = await collectEntriesForBranchSummary(this.session, oldLeafId, targetId);
 		const preparation = {
 			targetId,
 			oldLeafId,
@@ -469,7 +469,7 @@ export class DefaultAgentHarness implements AgentHarness {
 				typeof content === "string"
 					? content
 					: content
-							.filter((c): c is { type: "text"; text: string } => c.type === "text")
+							.filter((c): c is { readonly type: "text"; readonly text: string } => c.type === "text")
 							.map((c) => c.text)
 							.join("");
 		} else if (targetEntry.type === "custom_message") {
@@ -478,26 +478,29 @@ export class DefaultAgentHarness implements AgentHarness {
 				typeof targetEntry.content === "string"
 					? targetEntry.content
 					: targetEntry.content
-							.filter((c): c is { type: "text"; text: string } => c.type === "text")
+							.filter((c): c is { readonly type: "text"; readonly text: string } => c.type === "text")
 							.map((c) => c.text)
 							.join("");
 		} else {
 			newLeafId = targetId;
 		}
-		await this.sessionTree.moveTo(newLeafId);
-		if (summaryText) {
-			const summaryId = await this.sessionTree.appendBranchSummary(
-				newLeafId ?? "root",
-				summaryText,
-				summaryDetails,
-				hookResult?.summary !== undefined,
-			);
-			summaryEntry = await this.sessionTree.getEntry(summaryId);
+		const summaryId = await this.session.moveTo(
+			newLeafId,
+			summaryText
+				? {
+						summary: summaryText,
+						details: summaryDetails,
+						fromHook: hookResult?.summary !== undefined,
+					}
+				: undefined,
+		);
+		if (summaryId) {
+			summaryEntry = await this.session.getEntry(summaryId);
 		}
 		await this.syncFromTree();
 		await this.emitOwn({
 			type: "session_tree",
-			newLeafId: await this.sessionTree.getLeafId(),
+			newLeafId: await this.session.getLeafId(),
 			oldLeafId,
 			summaryEntry,
 			fromHook: hookResult?.summary !== undefined,
@@ -510,7 +513,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			const previousModel = this.conversation.model;
 			this.conversation.model = model;
 			this.agent.state.model = model;
-			await this.sessionTree.appendModelChange(model.provider, model.id);
+			await this.session.appendModelChange(model.provider, model.id);
 			await this.emitOwn({ type: "model_select", model, previousModel, source: "set" });
 		} else {
 			this.operation.pendingMutations.model = model;
@@ -522,7 +525,7 @@ export class DefaultAgentHarness implements AgentHarness {
 			const previousLevel = this.conversation.thinkingLevel;
 			this.conversation.thinkingLevel = level;
 			this.agent.state.thinkingLevel = level;
-			await this.sessionTree.appendThinkingLevelChange(level);
+			await this.session.appendThinkingLevelChange(level);
 			await this.emitOwn({ type: "thinking_level_select", level, previousLevel });
 		} else {
 			this.operation.pendingMutations.thinkingLevel = level;
--- a/packages/agent/src/harness/compaction/branch-summarization.ts
+++ b/packages/agent/src/harness/compaction/branch-summarization.ts
@@ -5,7 +5,7 @@
 * a summary of the branch being left so context isn't lost.
 */

-import type { Model } from "@mariozechner/pi-ai";
+import type { ImageContent, Model, TextContent } from "@mariozechner/pi-ai";
 import { completeSimple } from "@mariozechner/pi-ai";
 import type { AgentMessage } from "../../types.js";
 import {
@@ -14,7 +14,7 @@ import {
 	createCompactionSummaryMessage,
 	createCustomMessage,
 } from "../messages.js";
-import type { SessionTree, SessionTreeEntry } from "../types.js";
+import type { Session, SessionTreeEntry } from "../types.js";
 import { estimateTokens } from "./compaction.js";
 import {
 	computeFileLists,
@@ -96,7 +96,7 @@ export interface GenerateBranchSummaryOptions {
 * @returns Entries to summarize and the common ancestor
 */
 export async function collectEntriesForBranchSummary(
-	session: SessionTree,
+	session: Session,
 	oldLeafId: string | null,
 	targetId: string,
 ): Promise<CollectEntriesResult> {
@@ -125,7 +125,7 @@ export async function collectEntriesForBranchSummary(
 	while (current && current !== commonAncestorId) {
 		const entry = await session.getEntry(current);
 		if (!entry) break;
-		entries.push(entry);
+		entries.push(entry as SessionTreeEntry);
 		current = entry.parentId;
 	}

@@ -148,10 +148,16 @@ function getMessageFromEntry(entry: SessionTreeEntry): AgentMessage | undefined
 		case "message":
 			// Skip tool results - context is in assistant's tool call
 			if (entry.message.role === "toolResult") return undefined;
-			return entry.message;
+			return entry.message as AgentMessage;

 		case "custom_message":
-			return createCustomMessage(entry.customType, entry.content, entry.display, entry.details, entry.timestamp);
+			return createCustomMessage(
+				entry.customType,
+				entry.content as string | (TextContent | ImageContent)[],
+				entry.display,
+				entry.details,
+				entry.timestamp,
+			);

 		case "branch_summary":
 			return createBranchSummaryMessage(entry.summary, entry.fromId, entry.timestamp);
--- a/packages/agent/src/harness/compaction/compaction.ts
+++ b/packages/agent/src/harness/compaction/compaction.ts
@@ -5,7 +5,7 @@
 * and after compaction the session is reloaded.
 */

-import type { AssistantMessage, Model, Usage } from "@mariozechner/pi-ai";
+import type { AssistantMessage, ImageContent, Model, TextContent, Usage } from "@mariozechner/pi-ai";
 import { completeSimple } from "@mariozechner/pi-ai";
 import type { AgentMessage, ThinkingLevel } from "../../types.js";
 import {
@@ -79,10 +79,16 @@ function extractFileOperations(
 */
 function getMessageFromEntry(entry: SessionTreeEntry): AgentMessage | undefined {
 	if (entry.type === "message") {
-		return entry.message;
+		return entry.message as AgentMessage;
 	}
 	if (entry.type === "custom_message") {
-		return createCustomMessage(entry.customType, entry.content, entry.display, entry.details, entry.timestamp);
+		return createCustomMessage(
+			entry.customType,
+			entry.content as string | (TextContent | ImageContent)[],
+			entry.display,
+			entry.details,
+			entry.timestamp,
+		);
 	}
 	if (entry.type === "branch_summary") {
 		return createBranchSummaryMessage(entry.summary, entry.fromId, entry.timestamp);
@@ -158,7 +164,7 @@ export function getLastAssistantUsage(entries: SessionTreeEntry[]): Usage | unde
 	for (let i = entries.length - 1; i >= 0; i--) {
 		const entry = entries[i];
 		if (entry.type === "message") {
-			const usage = getAssistantUsage(entry.message);
+			const usage = getAssistantUsage(entry.message as AgentMessage);
 			if (usage) return usage;
 		}
 	}
@@ -405,7 +411,7 @@ export function findCutPoint(
 		if (entry.type !== "message") continue;

 		// Estimate this message's size
-		const messageTokens = estimateTokens(entry.message);
+		const messageTokens = estimateTokens(entry.message as AgentMessage);
 		accumulatedTokens += messageTokens;

 		// Check if we've exceeded the budget
--- a/packages/agent/src/harness/session/jsonl-session-repo.ts
+++ b/packages/agent/src/harness/session/jsonl-session-repo.ts
@@ -0,0 +1,142 @@
+import { constants } from "node:fs";
+import { access, mkdir, readdir, rm } from "node:fs/promises";
+import { join, resolve } from "node:path";
+import type {
+	JsonlSessionCreateOptions,
+	JsonlSessionListQuery,
+	JsonlSessionMetadata,
+	JsonlSessionRef,
+	JsonlSessionRepoApi,
+	JsonlSessionResolveOptions,
+	Session,
+} from "../types.js";
+import { JsonlSessionStorage, loadJsonlSessionMetadata } from "./jsonl-session-storage.js";
+import { createSessionId, createTimestamp, getPathEntriesToFork, toSession } from "./session-repo.js";
+
+async function exists(path: string): Promise<boolean> {
+	try {
+		await access(path, constants.F_OK);
+		return true;
+	} catch {
+		return false;
+	}
+}
+
+function encodeCwd(cwd: string): string {
+	return `--${cwd.replace(/^[/\\]/, "").replace(/[/\\:]/g, "-")}--`;
+}
+
+export class JsonlSessionRepo implements JsonlSessionRepoApi {
+	private sessionsRoot: string;
+
+	constructor(options: { sessionsRoot: string }) {
+		this.sessionsRoot = resolve(options.sessionsRoot);
+	}
+
+	private getSessionDir(cwd: string): string {
+		return join(this.sessionsRoot, encodeCwd(cwd));
+	}
+
+	private createSessionFilePath(cwd: string, sessionId: string, timestamp: string): string {
+		return join(this.getSessionDir(cwd), `${timestamp.replace(/[:.]/g, "-")}_${sessionId}.jsonl`);
+	}
+
+	private refPath(ref: JsonlSessionRef): string {
+		return resolve(ref.path);
+	}
+
+	async create(options: JsonlSessionCreateOptions): Promise<Session<JsonlSessionMetadata>> {
+		await mkdir(this.sessionsRoot, { recursive: true });
+		const id = options.id ?? createSessionId();
+		const createdAt = createTimestamp();
+		const filePath = this.createSessionFilePath(options.cwd, id, createdAt);
+		const storage = await JsonlSessionStorage.create(filePath, {
+			cwd: options.cwd,
+			sessionId: id,
+			parentSessionPath: options.parentSessionPath,
+		});
+		return toSession(storage);
+	}
+
+	async open(ref: JsonlSessionRef): Promise<Session<JsonlSessionMetadata>> {
+		const filePath = this.refPath(ref);
+		if (!(await exists(filePath))) {
+			throw new Error(`Session not found: ${filePath}`);
+		}
+		const storage = await JsonlSessionStorage.open(filePath);
+		return toSession(storage);
+	}
+
+	async list(query: JsonlSessionListQuery = {}): Promise<JsonlSessionMetadata[]> {
+		const dirs = query.cwd ? [this.getSessionDir(query.cwd)] : await this.listSessionDirs();
+		const sessions: JsonlSessionMetadata[] = [];
+		for (const dir of dirs) {
+			if (!(await exists(dir))) continue;
+			const files = (await readdir(dir)).filter((file) => file.endsWith(".jsonl")).map((file) => join(dir, file));
+			for (const filePath of files) {
+				try {
+					sessions.push(await loadJsonlSessionMetadata(filePath));
+				} catch {
+					// Ignore invalid session files when listing a directory.
+				}
+			}
+		}
+		sessions.sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime());
+		return sessions;
+	}
+
+	async resolve(ref: string, options: JsonlSessionResolveOptions = {}): Promise<JsonlSessionMetadata[]> {
+		if (ref.includes("/") || ref.includes("\\") || ref.endsWith(".jsonl")) {
+			try {
+				return [await loadJsonlSessionMetadata(resolve(ref))];
+			} catch {
+				return [];
+			}
+		}
+
+		const local = options.cwd
+			? (await this.list({ cwd: options.cwd })).filter((session) => session.id.startsWith(ref))
+			: [];
+		if (local.length > 0 || !options.searchAll) return local;
+		return (await this.list()).filter((session) => session.id.startsWith(ref));
+	}
+
+	async getMostRecent(query: JsonlSessionListQuery = {}): Promise<JsonlSessionMetadata | undefined> {
+		return (await this.list(query))[0];
+	}
+
+	async delete(ref: JsonlSessionRef): Promise<void> {
+		const filePath = this.refPath(ref);
+		await rm(filePath, { force: true });
+	}
+
+	async fork(
+		ref: JsonlSessionRef,
+		options: JsonlSessionCreateOptions & { entryId: string; position?: "before" | "at"; id?: string },
+	): Promise<Session<JsonlSessionMetadata>> {
+		const source = await this.open(ref);
+		const forkedEntries = await getPathEntriesToFork(
+			source.getStorage(),
+			options.entryId,
+			options.position ?? "before",
+		);
+		const sourceInfo = await source.getMetadata();
+		const id = options.id ?? createSessionId();
+		const createdAt = createTimestamp();
+		const storage = await JsonlSessionStorage.create(this.createSessionFilePath(options.cwd, id, createdAt), {
+			cwd: options.cwd,
+			sessionId: id,
+			parentSessionPath: options.parentSessionPath ?? sourceInfo.path,
+		});
+		for (const entry of forkedEntries) {
+			await storage.appendEntry(entry);
+		}
+		return toSession(storage);
+	}
+
+	private async listSessionDirs(): Promise<string[]> {
+		if (!(await exists(this.sessionsRoot))) return [];
+		const entries = await readdir(this.sessionsRoot, { withFileTypes: true });
+		return entries.filter((entry) => entry.isDirectory()).map((entry) => join(this.sessionsRoot, entry.name));
+	}
+}
--- a/packages/agent/src/harness/session/jsonl-session-storage.ts
+++ b/packages/agent/src/harness/session/jsonl-session-storage.ts
@@ -2,7 +2,7 @@ import { createReadStream } from "node:fs";
 import { appendFile, mkdir, readFile, writeFile } from "node:fs/promises";
 import { dirname, resolve } from "node:path";
 import { createInterface } from "node:readline";
-import type { JsonlSessionInfo, SessionTreeEntry, SessionTreeStorage } from "../types.js";
+import type { JsonlSessionMetadata, SessionStorage, SessionTreeEntry } from "../types.js";

 interface SessionHeader {
 	type: "session";
@@ -13,7 +13,25 @@ interface SessionHeader {
 	parentSession?: string;
 }

-function headerToSessionInfo(header: SessionHeader, path: string): JsonlSessionInfo {
+function updateLabelCache(labelsById: Map<string, string>, entry: SessionTreeEntry): void {
+	if (entry.type !== "label") return;
+	const label = entry.label?.trim();
+	if (label) {
+		labelsById.set(entry.targetId, label);
+	} else {
+		labelsById.delete(entry.targetId);
+	}
+}
+
+function buildLabelsById(entries: SessionTreeEntry[]): Map<string, string> {
+	const labelsById = new Map<string, string>();
+	for (const entry of entries) {
+		updateLabelCache(labelsById, entry);
+	}
+	return labelsById;
+}
+
+function headerToSessionMetadata(header: SessionHeader, path: string): JsonlSessionMetadata {
 	return {
 		id: header.id,
 		createdAt: header.timestamp,
@@ -23,7 +41,7 @@ function headerToSessionInfo(header: SessionHeader, path: string): JsonlSessionI
 	};
 }

-export async function loadJsonlSessionInfo(filePath: string): Promise<JsonlSessionInfo> {
+export async function loadJsonlSessionMetadata(filePath: string): Promise<JsonlSessionMetadata> {
 	const stream = createReadStream(filePath, { encoding: "utf8" });
 	const lines = createInterface({ input: stream, crlfDelay: Infinity });
 	try {
@@ -31,7 +49,7 @@ export async function loadJsonlSessionInfo(filePath: string): Promise<JsonlSessi
 			if (!line.trim()) break;
 			try {
 				const header = JSON.parse(line) as SessionHeader;
-				return headerToSessionInfo(header, resolve(filePath));
+				return headerToSessionMetadata(header, resolve(filePath));
 			} catch {
 				throw new Error(`Invalid JSONL session file ${filePath}: first line is not a valid session header`);
 			}
@@ -75,35 +93,27 @@ async function loadJsonlStorage(filePath: string): Promise<{
 	return { header, entries, leafId };
 }

-export class JsonlSessionTreeStorage implements SessionTreeStorage<JsonlSessionInfo> {
+export class JsonlSessionStorage implements SessionStorage<JsonlSessionMetadata> {
 	private readonly filePath: string;
-	private readonly header: SessionHeader;
-	private readonly sessionInfo: JsonlSessionInfo;
+	private readonly metadata: JsonlSessionMetadata;
 	private entries: SessionTreeEntry[];
 	private byId: Map<string, SessionTreeEntry>;
+	private labelsById: Map<string, string>;
 	private currentLeafId: string | null;
-	private headerWritten: boolean;

-	private constructor(
-		filePath: string,
-		header: SessionHeader,
-		entries: SessionTreeEntry[],
-		leafId: string | null,
-		headerWritten: boolean,
-	) {
+	private constructor(filePath: string, header: SessionHeader, entries: SessionTreeEntry[], leafId: string | null) {
 		this.filePath = resolve(filePath);
-		this.header = header;
-		this.sessionInfo = headerToSessionInfo(header, this.filePath);
+		this.metadata = headerToSessionMetadata(header, this.filePath);
 		this.entries = entries;
 		this.byId = new Map(entries.map((entry) => [entry.id, entry]));
+		this.labelsById = buildLabelsById(entries);
 		this.currentLeafId = leafId;
-		this.headerWritten = headerWritten;
 	}

-	static async open(filePath: string): Promise<JsonlSessionTreeStorage> {
+	static async open(filePath: string): Promise<JsonlSessionStorage> {
 		const resolvedPath = resolve(filePath);
 		const loaded = await loadJsonlStorage(resolvedPath);
-		return new JsonlSessionTreeStorage(resolvedPath, loaded.header, loaded.entries, loaded.leafId, true);
+		return new JsonlSessionStorage(resolvedPath, loaded.header, loaded.entries, loaded.leafId);
 	}

 	static async create(
@@ -113,7 +123,7 @@ export class JsonlSessionTreeStorage implements SessionTreeStorage<JsonlSessionI
 			sessionId: string;
 			parentSessionPath?: string;
 		},
-	): Promise<JsonlSessionTreeStorage> {
+	): Promise<JsonlSessionStorage> {
 		const resolvedPath = resolve(filePath);
 		const header: SessionHeader = {
 			type: "session",
@@ -123,11 +133,13 @@ export class JsonlSessionTreeStorage implements SessionTreeStorage<JsonlSessionI
 			cwd: options.cwd,
 			parentSession: options.parentSessionPath,
 		};
-		return new JsonlSessionTreeStorage(resolvedPath, header, [], null, false);
+		await mkdir(dirname(resolvedPath), { recursive: true });
+		await writeFile(resolvedPath, `${JSON.stringify(header)}\n`);
+		return new JsonlSessionStorage(resolvedPath, header, [], null);
 	}

-	async getSessionInfo(): Promise<JsonlSessionInfo> {
-		return this.sessionInfo;
+	async getMetadata(): Promise<JsonlSessionMetadata> {
+		return this.metadata;
 	}

 	async getLeafId(): Promise<string | null> {
@@ -142,14 +154,10 @@ export class JsonlSessionTreeStorage implements SessionTreeStorage<JsonlSessionI
 	}

 	async appendEntry(entry: SessionTreeEntry): Promise<void> {
-		if (!this.headerWritten) {
-			await mkdir(dirname(this.filePath), { recursive: true });
-			await writeFile(this.filePath, `${JSON.stringify(this.header)}\n`);
-			this.headerWritten = true;
-		}
 		await appendFile(this.filePath, `${JSON.stringify(entry)}\n`);
 		this.entries.push(entry);
 		this.byId.set(entry.id, entry);
+		updateLabelCache(this.labelsById, entry);
 		this.currentLeafId = entry.id;
 	}

@@ -157,6 +165,10 @@ export class JsonlSessionTreeStorage implements SessionTreeStorage<JsonlSessionI
 		return this.byId.get(id);
 	}

+	async getLabel(id: string): Promise<string | undefined> {
+		return this.labelsById.get(id);
+	}
+
 	async getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]> {
 		if (leafId === null) return [];
 		const path: SessionTreeEntry[] = [];
--- a/packages/agent/src/harness/session/memory-session-repo.ts
+++ b/packages/agent/src/harness/session/memory-session-repo.ts
@@ -0,0 +1,55 @@
+import type { Session, SessionMetadata, SessionRepo } from "../types.js";
+import { InMemorySessionStorage } from "./memory-session-storage.js";
+import { createSessionId, createTimestamp, getPathEntriesToFork, toSession } from "./session-repo.js";
+
+export class InMemorySessionRepo implements SessionRepo<SessionMetadata, { id?: string }, string, void> {
+	private sessions = new Map<string, Session<SessionMetadata>>();
+
+	async create(options: { id?: string } = {}): Promise<Session<SessionMetadata>> {
+		const info: SessionMetadata = {
+			id: options.id ?? createSessionId(),
+			createdAt: createTimestamp(),
+		};
+		const storage = new InMemorySessionStorage({ metadata: info });
+		const session = toSession(storage);
+		this.sessions.set(info.id, session);
+		return session;
+	}
+
+	async open(ref: string): Promise<Session<SessionMetadata>> {
+		const session = this.sessions.get(ref);
+		if (!session) {
+			throw new Error(`Session not found: ${ref}`);
+		}
+		return session;
+	}
+
+	async list(): Promise<SessionMetadata[]> {
+		return Promise.all([...this.sessions.values()].map((session) => session.getMetadata()));
+	}
+
+	async delete(ref: string): Promise<void> {
+		this.sessions.delete(ref);
+	}
+
+	async fork(
+		ref: string,
+		options: { entryId: string; position?: "before" | "at"; id?: string },
+	): Promise<Session<SessionMetadata>> {
+		const source = await this.open(ref);
+		const forkedEntries = await getPathEntriesToFork(
+			source.getStorage(),
+			options.entryId,
+			options.position ?? "before",
+		);
+		const info: SessionMetadata = {
+			id: options.id ?? createSessionId(),
+			createdAt: createTimestamp(),
+		};
+		const leafId = forkedEntries[forkedEntries.length - 1]?.id ?? null;
+		const storage = new InMemorySessionStorage({ metadata: info, entries: forkedEntries, leafId });
+		const session = toSession(storage);
+		this.sessions.set(info.id, session);
+		return session;
+	}
+}
--- a/packages/agent/src/harness/session/memory-session-storage.ts
+++ b/packages/agent/src/harness/session/memory-session-storage.ts
@@ -1,24 +1,44 @@
 import { v7 as uuidv7 } from "uuid";
-import type { SessionInfo, SessionTreeEntry, SessionTreeStorage } from "../types.js";
+import type { SessionMetadata, SessionStorage, SessionTreeEntry } from "../types.js";

-export class InMemorySessionTreeStorage implements SessionTreeStorage {
-	private readonly sessionInfo: SessionInfo;
+function updateLabelCache(labelsById: Map<string, string>, entry: SessionTreeEntry): void {
+	if (entry.type !== "label") return;
+	const label = entry.label?.trim();
+	if (label) {
+		labelsById.set(entry.targetId, label);
+	} else {
+		labelsById.delete(entry.targetId);
+	}
+}
+
+function buildLabelsById(entries: SessionTreeEntry[]): Map<string, string> {
+	const labelsById = new Map<string, string>();
+	for (const entry of entries) {
+		updateLabelCache(labelsById, entry);
+	}
+	return labelsById;
+}
+
+export class InMemorySessionStorage implements SessionStorage {
+	private readonly metadata: SessionMetadata;
 	private entries: SessionTreeEntry[];
 	private byId: Map<string, SessionTreeEntry>;
+	private labelsById: Map<string, string>;
 	private leafId: string | null;

-	constructor(options?: { entries?: SessionTreeEntry[]; leafId?: string | null; sessionInfo?: SessionInfo }) {
+	constructor(options?: { entries?: SessionTreeEntry[]; leafId?: string | null; metadata?: SessionMetadata }) {
 		this.entries = options?.entries ? [...options.entries] : [];
 		this.byId = new Map(this.entries.map((entry) => [entry.id, entry]));
+		this.labelsById = buildLabelsById(this.entries);
 		this.leafId = options?.leafId ?? this.entries[this.entries.length - 1]?.id ?? null;
 		if (this.leafId !== null && !this.byId.has(this.leafId)) {
 			throw new Error(`Entry ${this.leafId} not found`);
 		}
-		this.sessionInfo = options?.sessionInfo ?? { id: uuidv7(), createdAt: new Date().toISOString() };
+		this.metadata = options?.metadata ?? { id: uuidv7(), createdAt: new Date().toISOString() };
 	}

-	async getSessionInfo(): Promise<SessionInfo> {
-		return this.sessionInfo;
+	async getMetadata(): Promise<SessionMetadata> {
+		return this.metadata;
 	}

 	async getLeafId(): Promise<string | null> {
@@ -35,6 +55,7 @@ export class InMemorySessionTreeStorage implements SessionTreeStorage {
 	async appendEntry(entry: SessionTreeEntry): Promise<void> {
 		this.entries.push(entry);
 		this.byId.set(entry.id, entry);
+		updateLabelCache(this.labelsById, entry);
 		this.leafId = entry.id;
 	}

@@ -42,6 +63,10 @@ export class InMemorySessionTreeStorage implements SessionTreeStorage {
 		return this.byId.get(id);
 	}

+	async getLabel(id: string): Promise<string | undefined> {
+		return this.labelsById.get(id);
+	}
+
 	async getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]> {
 		if (leafId === null) return [];
 		const path: SessionTreeEntry[] = [];
--- a/packages/agent/src/harness/session/session-repo.ts
+++ b/packages/agent/src/harness/session/session-repo.ts
@@ -1,41 +1,25 @@
-import { existsSync, mkdirSync, readdirSync, rmSync } from "node:fs";
-import { join, resolve } from "node:path";
 import { v7 as uuidv7 } from "uuid";
-import type {
-	JsonlSessionInfo,
-	JsonlSessionRepo,
-	Session,
-	SessionInfo,
-	SessionRepo,
-	SessionTreeEntry,
-	SessionTreeStorage,
-} from "../types.js";
-import { JsonlSessionTreeStorage } from "./jsonl-session-storage.js";
-import { InMemorySessionTreeStorage } from "./memory-session-storage.js";
-import { DefaultSessionTree } from "./session-tree.js";
+import type { Session, SessionMetadata, SessionStorage, SessionTreeEntry } from "../types.js";
+import { DefaultSession } from "./session-tree.js";

-function createSessionId(): string {
+export function createSessionId(): string {
 	return uuidv7();
 }

-function createTimestamp(): string {
+export function createTimestamp(): string {
 	return new Date().toISOString();
 }

-function toSession<TInfo extends SessionInfo>(
-	storage: SessionTreeStorage<TInfo>,
-	tree: DefaultSessionTree<TInfo>,
-): Session<TInfo> {
-	return { storage, tree };
+export function toSession<TMetadata extends SessionMetadata>(storage: SessionStorage<TMetadata>): Session<TMetadata> {
+	return new DefaultSession(storage);
 }

-function getPathEntriesToFork(
-	entries: SessionTreeEntry[],
+export async function getPathEntriesToFork(
+	storage: SessionStorage,
 	entryId: string,
 	position: "before" | "at",
-): SessionTreeEntry[] {
-	const byId = new Map<string, SessionTreeEntry>(entries.map((entry) => [entry.id, entry]));
-	const target = byId.get(entryId);
+): Promise<SessionTreeEntry[]> {
+	const target = await storage.getEntry(entryId);
 	if (!target) {
 		throw new Error(`Entry ${entryId} not found`);
 	}
@@ -48,172 +32,5 @@ function getPathEntriesToFork(
 		}
 		effectiveLeafId = target.parentId;
 	}
-	if (effectiveLeafId === null) {
-		return [];
-	}
-	const path: SessionTreeEntry[] = [];
-	let current = byId.get(effectiveLeafId);
-	while (current) {
-		path.unshift(current);
-		current = current.parentId ? byId.get(current.parentId) : undefined;
-	}
-	return path;
-}
-
-export class InMemorySessionRepo implements SessionRepo<string> {
-	private sessions = new Map<string, Session<SessionInfo>>();
-
-	async create(options?: { id?: string }): Promise<Session<SessionInfo>> {
-		const info: SessionInfo = {
-			id: options?.id ?? createSessionId(),
-			createdAt: createTimestamp(),
-		};
-		const storage = new InMemorySessionTreeStorage({ sessionInfo: info });
-		const session = toSession(storage, new DefaultSessionTree(storage));
-		this.sessions.set(info.id, session);
-		return session;
-	}
-
-	async open(ref: string): Promise<Session<SessionInfo>> {
-		const session = this.sessions.get(ref);
-		if (!session) {
-			throw new Error(`Session not found: ${ref}`);
-		}
-		return session;
-	}
-
-	async list(): Promise<Array<Session<SessionInfo>>> {
-		return [...this.sessions.values()];
-	}
-
-	async delete(ref: string): Promise<void> {
-		this.sessions.delete(ref);
-	}
-
-	async fork(
-		ref: string,
-		options: { entryId: string; position?: "before" | "at"; id?: string },
-	): Promise<Session<SessionInfo>> {
-		const source = await this.open(ref);
-		const entries = await source.tree.getEntries();
-		const forkedEntries = getPathEntriesToFork(entries, options.entryId, options.position ?? "before");
-		const info: SessionInfo = {
-			id: options.id ?? createSessionId(),
-			createdAt: createTimestamp(),
-		};
-		const leafId = forkedEntries[forkedEntries.length - 1]?.id ?? null;
-		const storage = new InMemorySessionTreeStorage({ sessionInfo: info, entries: forkedEntries, leafId });
-		const session = toSession(storage, new DefaultSessionTree(storage));
-		this.sessions.set(info.id, session);
-		return session;
-	}
-}
-
-export class JsonlSessionFileRepo implements JsonlSessionRepo<string> {
-	private sessionDir: string;
-	private cwd: string;
-
-	constructor(options: { sessionDir: string; cwd: string }) {
-		this.sessionDir = resolve(options.sessionDir);
-		this.cwd = options.cwd;
-		mkdirSync(this.sessionDir, { recursive: true });
-	}
-
-	private createSessionFilePath(sessionId: string, timestamp: string): string {
-		return join(this.sessionDir, `${timestamp.replace(/[:.]/g, "-")}_${sessionId}.jsonl`);
-	}
-
-	async create(options?: { id?: string; parentSessionPath?: string }): Promise<Session<JsonlSessionInfo>> {
-		const id = options?.id ?? createSessionId();
-		const createdAt = createTimestamp();
-		const filePath = this.createSessionFilePath(id, createdAt);
-		const storage = await JsonlSessionTreeStorage.create(filePath, {
-			cwd: this.cwd,
-			sessionId: id,
-			parentSessionPath: options?.parentSessionPath,
-		});
-		return toSession(storage, new DefaultSessionTree(storage));
-	}
-
-	async open(ref: string): Promise<Session<JsonlSessionInfo>> {
-		const filePath = ref.includes("/") || ref.endsWith(".jsonl") ? resolve(ref) : join(this.sessionDir, ref);
-		if (!existsSync(filePath)) {
-			throw new Error(`Session not found: ${ref}`);
-		}
-		const storage = await JsonlSessionTreeStorage.open(filePath);
-		return toSession(storage, new DefaultSessionTree(storage));
-	}
-
-	async list(): Promise<Array<Session<JsonlSessionInfo>>> {
-		if (!existsSync(this.sessionDir)) {
-			return [];
-		}
-		const files = readdirSync(this.sessionDir)
-			.filter((file) => file.endsWith(".jsonl"))
-			.map((file) => join(this.sessionDir, file));
-		const sessions: Array<Session<JsonlSessionInfo>> = [];
-		for (const filePath of files) {
-			try {
-				const storage = await JsonlSessionTreeStorage.open(filePath);
-				sessions.push(toSession(storage, new DefaultSessionTree(storage)));
-			} catch {
-				// Ignore invalid session files when listing a directory.
-			}
-		}
-		return sessions;
-	}
-
-	async listByCwd(cwd: string): Promise<Array<Session<JsonlSessionInfo>>> {
-		const sessions = await this.list();
-		const result: Array<Session<JsonlSessionInfo>> = [];
-		for (const session of sessions) {
-			if ((await session.storage.getSessionInfo()).cwd === cwd) {
-				result.push(session);
-			}
-		}
-		return result;
-	}
-
-	async getMostRecentByCwd(cwd: string): Promise<Session<JsonlSessionInfo> | undefined> {
-		const sessionsWithInfo = await Promise.all(
-			(await this.listByCwd(cwd)).map(async (session) => ({
-				session,
-				info: await session.storage.getSessionInfo(),
-			})),
-		);
-		sessionsWithInfo.sort((a, b) => new Date(b.info.createdAt).getTime() - new Date(a.info.createdAt).getTime());
-		return sessionsWithInfo[0]?.session;
-	}
-
-	async delete(ref: string): Promise<void> {
-		const filePath = ref.includes("/") || ref.endsWith(".jsonl") ? resolve(ref) : join(this.sessionDir, ref);
-		if (existsSync(filePath)) {
-			rmSync(filePath, { force: true });
-		}
-	}
-
-	async fork(
-		ref: string,
-		options: { entryId: string; position?: "before" | "at"; id?: string },
-	): Promise<Session<JsonlSessionInfo>> {
-		const source = await this.open(ref);
-		const entries = await source.tree.getEntries();
-		const forkedEntries = getPathEntriesToFork(entries, options.entryId, options.position ?? "before");
-		const id = options.id ?? createSessionId();
-		const createdAt = createTimestamp();
-		const filePath = this.createSessionFilePath(id, createdAt);
-		const sourceInfo = await source.storage.getSessionInfo();
-		const storage = await JsonlSessionTreeStorage.create(filePath, {
-			cwd: sourceInfo.cwd,
-			sessionId: id,
-			parentSessionPath: sourceInfo.path,
-		});
-		for (const entry of forkedEntries) {
-			await storage.appendEntry(entry);
-		}
-		if (forkedEntries.length === 0) {
-			await storage.getSessionInfo();
-		}
-		return toSession(storage, new DefaultSessionTree(storage));
-	}
+	return storage.getPathToRoot(effectiveLeafId);
 }
--- a/packages/agent/src/harness/session/session-tree.ts
+++ b/packages/agent/src/harness/session/session-tree.ts
@@ -10,12 +10,12 @@ import type {
 	LabelEntry,
 	MessageEntry,
 	ModelChangeEntry,
+	Session,
 	SessionContext,
-	SessionInfo,
 	SessionInfoEntry,
-	SessionTree,
+	SessionMetadata,
+	SessionStorage,
 	SessionTreeEntry,
-	SessionTreeStorage,
 	ThinkingLevelChangeEntry,
 } from "../types.js";

@@ -27,12 +27,12 @@ function generateId(byId: { has(id: string): boolean }): string {
 	return randomUUID();
 }

-export function buildSessionContext(entries: SessionTreeEntry[]): SessionContext {
+export function buildSessionContext(pathEntries: SessionTreeEntry[]): SessionContext {
 	let thinkingLevel = "off";
 	let model: { provider: string; modelId: string } | null = null;
 	let compaction: CompactionEntry | null = null;

-	for (const entry of entries) {
+	for (const entry of pathEntries) {
 		if (entry.type === "thinking_level_change") {
 			thinkingLevel = entry.thinkingLevel;
 		} else if (entry.type === "model_change") {
@@ -47,10 +47,16 @@ export function buildSessionContext(entries: SessionTreeEntry[]): SessionContext
 	const messages: AgentMessage[] = [];
 	const appendMessage = (entry: SessionTreeEntry) => {
 		if (entry.type === "message") {
-			messages.push(entry.message);
+			messages.push(entry.message as AgentMessage);
 		} else if (entry.type === "custom_message") {
 			messages.push(
-				createCustomMessage(entry.customType, entry.content, entry.display, entry.details, entry.timestamp),
+				createCustomMessage(
+					entry.customType,
+					entry.content as string | (TextContent | ImageContent)[],
+					entry.display,
+					entry.details,
+					entry.timestamp,
+				),
 			);
 		} else if (entry.type === "branch_summary" && entry.summary) {
 			messages.push(createBranchSummaryMessage(entry.summary, entry.fromId, entry.timestamp));
@@ -59,18 +65,18 @@ export function buildSessionContext(entries: SessionTreeEntry[]): SessionContext

 	if (compaction) {
 		messages.push(createCompactionSummaryMessage(compaction.summary, compaction.tokensBefore, compaction.timestamp));
-		const compactionIdx = entries.findIndex((e) => e.type === "compaction" && e.id === compaction.id);
+		const compactionIdx = pathEntries.findIndex((e) => e.type === "compaction" && e.id === compaction.id);
 		let foundFirstKept = false;
 		for (let i = 0; i < compactionIdx; i++) {
-			const entry = entries[i]!;
+			const entry = pathEntries[i]!;
 			if (entry.id === compaction.firstKeptEntryId) foundFirstKept = true;
 			if (foundFirstKept) appendMessage(entry);
 		}
-		for (let i = compactionIdx + 1; i < entries.length; i++) {
-			appendMessage(entries[i]!);
+		for (let i = compactionIdx + 1; i < pathEntries.length; i++) {
+			appendMessage(pathEntries[i]!);
 		}
 	} else {
-		for (const entry of entries) {
+		for (const entry of pathEntries) {
 			appendMessage(entry);
 		}
 	}
@@ -78,13 +84,21 @@ export function buildSessionContext(entries: SessionTreeEntry[]): SessionContext
 	return { messages, thinkingLevel, model };
 }

-export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> implements SessionTree {
-	private storage: SessionTreeStorage<TInfo>;
+export class DefaultSession<TMetadata extends SessionMetadata = SessionMetadata> implements Session<TMetadata> {
+	private storage: SessionStorage<TMetadata>;

-	constructor(storage: SessionTreeStorage<TInfo>) {
+	constructor(storage: SessionStorage<TMetadata>) {
 		this.storage = storage;
 	}

+	getMetadata(): Promise<TMetadata> {
+		return this.storage.getMetadata();
+	}
+
+	getStorage(): SessionStorage<TMetadata> {
+		return this.storage;
+	}
+
 	getLeafId(): Promise<string | null> {
 		return this.storage.getLeafId();
 	}
@@ -106,19 +120,8 @@ export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> impleme
 		return buildSessionContext(await this.getBranch());
 	}

-	getSessionInfo(): Promise<TInfo> {
-		return this.storage.getSessionInfo();
-	}
-
-	async getLabel(id: string): Promise<string | undefined> {
-		const entries = await this.storage.getEntries();
-		for (let i = entries.length - 1; i >= 0; i--) {
-			const entry = entries[i]!;
-			if (entry.type === "label" && entry.targetId === id) {
-				return entry.label?.trim() || undefined;
-			}
-		}
-		return undefined;
+	getLabel(id: string): Promise<string | undefined> {
+		return this.storage.getLabel(id);
 	}

 	async getSessionName(): Promise<string | undefined> {
@@ -193,24 +196,6 @@ export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> impleme
 		} satisfies CompactionEntry<T>);
 	}

-	async appendBranchSummary<T = unknown>(
-		fromId: string,
-		summary: string,
-		details?: T,
-		fromHook?: boolean,
-	): Promise<string> {
-		return this.appendTypedEntry({
-			type: "branch_summary",
-			id: await this.makeEntryId(),
-			parentId: await this.storage.getLeafId(),
-			timestamp: new Date().toISOString(),
-			fromId,
-			summary,
-			details,
-			fromHook,
-		} satisfies BranchSummaryEntry<T>);
-	}
-
 	async appendCustomEntry(customType: string, data?: unknown): Promise<string> {
 		return this.appendTypedEntry({
 			type: "custom",
@@ -240,7 +225,10 @@ export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> impleme
 		} satisfies CustomMessageEntry<T>);
 	}

-	async appendLabelChange(targetId: string, label: string | undefined): Promise<string> {
+	async appendLabel(targetId: string, label: string | undefined): Promise<string> {
+		if (!(await this.storage.getEntry(targetId))) {
+			throw new Error(`Entry ${targetId} not found`);
+		}
 		return this.appendTypedEntry({
 			type: "label",
 			id: await this.makeEntryId(),
@@ -251,7 +239,7 @@ export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> impleme
 		} satisfies LabelEntry);
 	}

-	async appendSessionInfo(name: string): Promise<string> {
+	async appendSessionName(name: string): Promise<string> {
 		return this.appendTypedEntry({
 			type: "session_info",
 			id: await this.makeEntryId(),
@@ -261,10 +249,24 @@ export class DefaultSessionTree<TInfo extends SessionInfo = SessionInfo> impleme
 		} satisfies SessionInfoEntry);
 	}

-	async moveTo(entryId: string | null): Promise<void> {
+	async moveTo(
+		entryId: string | null,
+		summary?: { summary: string; details?: unknown; fromHook?: boolean },
+	): Promise<string | undefined> {
 		if (entryId !== null && !(await this.storage.getEntry(entryId))) {
 			throw new Error(`Entry ${entryId} not found`);
 		}
 		await this.storage.setLeafId(entryId);
+		if (!summary) return undefined;
+		return this.appendTypedEntry({
+			type: "branch_summary",
+			id: await this.makeEntryId(),
+			parentId: entryId,
+			timestamp: new Date().toISOString(),
+			fromId: entryId ?? "root",
+			summary: summary.summary,
+			details: summary.details,
+			fromHook: summary.fromHook,
+		} satisfies BranchSummaryEntry);
 	}
 }
--- a/packages/agent/src/harness/types.ts
+++ b/packages/agent/src/harness/types.ts
@@ -136,7 +136,7 @@ export interface LabelEntry extends SessionTreeEntryBase {
 }

 export interface SessionInfoEntry extends SessionTreeEntryBase {
-	type: "session_info";
+	type: "session_info"; // legacy name, kept for backwards compatibility
 	name?: string;
 }

@@ -157,28 +157,32 @@ export interface SessionContext {
 	model: { provider: string; modelId: string } | null;
 }

-export interface SessionInfo {
+export interface SessionMetadata {
 	id: string;
 	createdAt: string;
 }

-export interface JsonlSessionInfo extends SessionInfo {
+export interface JsonlSessionMetadata extends SessionMetadata {
 	cwd: string;
 	path: string;
 	parentSessionPath?: string;
 }

-export interface SessionTreeStorage<TInfo extends SessionInfo = SessionInfo> {
-	getSessionInfo(): Promise<TInfo>;
+export interface SessionStorage<TMetadata extends SessionMetadata = SessionMetadata> {
+	getMetadata(): Promise<TMetadata>;
 	getLeafId(): Promise<string | null>;
 	setLeafId(leafId: string | null): Promise<void>;
 	appendEntry(entry: SessionTreeEntry): Promise<void>;
 	getEntry(id: string): Promise<SessionTreeEntry | undefined>;
+	getLabel(id: string): Promise<string | undefined>;
 	getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]>;
 	getEntries(): Promise<SessionTreeEntry[]>;
 }

-export interface SessionTree {
+export interface Session<TMetadata extends SessionMetadata = SessionMetadata> {
+	getMetadata(): Promise<TMetadata>;
+	getStorage(): SessionStorage<TMetadata>;
+
 	getLeafId(): Promise<string | null>;
 	getEntry(id: string): Promise<SessionTreeEntry | undefined>;
 	getEntries(): Promise<SessionTreeEntry[]>;
@@ -197,7 +201,6 @@ export interface SessionTree {
 		details?: T,
 		fromHook?: boolean,
 	): Promise<string>;
-	appendBranchSummary<T = unknown>(fromId: string, summary: string, details?: T, fromHook?: boolean): Promise<string>;
 	appendCustomEntry(customType: string, data?: unknown): Promise<string>;
 	appendCustomMessageEntry<T = unknown>(
 		customType: string,
@@ -205,15 +208,13 @@ export interface SessionTree {
 		display: boolean,
 		details?: T,
 	): Promise<string>;
-	appendLabelChange(targetId: string, label: string | undefined): Promise<string>;
-	appendSessionInfo(name: string): Promise<string>;
+	appendLabel(targetId: string, label: string | undefined): Promise<string>;
+	appendSessionName(name: string): Promise<string>;

-	moveTo(entryId: string | null): Promise<void>;
-}
-
-export interface Session<TInfo extends SessionInfo = SessionInfo> {
-	storage: SessionTreeStorage<TInfo>;
-	tree: SessionTree;
+	moveTo(
+		entryId: string | null,
+		summary?: { summary: string; details?: unknown; fromHook?: boolean },
+	): Promise<string | undefined>;
 }

 export interface SessionCreateOptions {
@@ -227,25 +228,38 @@ export interface SessionForkOptions {
 }

 export interface SessionRepo<
-	TRef = string,
-	TInfo extends SessionInfo = SessionInfo,
+	TMetadata extends SessionMetadata = SessionMetadata,
 	TCreateOptions extends SessionCreateOptions = SessionCreateOptions,
+	TRef = string,
+	TListQuery = void,
 > {
-	create(options?: TCreateOptions): Promise<Session<TInfo>>;
-	open(ref: TRef): Promise<Session<TInfo>>;
-	list(): Promise<Array<Session<TInfo>>>;
+	create(options: TCreateOptions): Promise<Session<TMetadata>>;
+	open(ref: TRef): Promise<Session<TMetadata>>;
+	list(query?: TListQuery): Promise<TMetadata[]>;
 	delete(ref: TRef): Promise<void>;
-	fork(ref: TRef, options: SessionForkOptions): Promise<Session<TInfo>>;
+	fork(ref: TRef, options: SessionForkOptions & TCreateOptions): Promise<Session<TMetadata>>;
 }

 export interface JsonlSessionCreateOptions extends SessionCreateOptions {
+	cwd: string;
 	parentSessionPath?: string;
 }

-export interface JsonlSessionRepo<TRef = string>
-	extends SessionRepo<TRef, JsonlSessionInfo, JsonlSessionCreateOptions> {
-	listByCwd(cwd: string): Promise<Array<Session<JsonlSessionInfo>>>;
-	getMostRecentByCwd(cwd: string): Promise<Session<JsonlSessionInfo> | undefined>;
+export type JsonlSessionRef = { path: string } | JsonlSessionMetadata;
+
+export interface JsonlSessionListQuery {
+	cwd?: string;
+}
+
+export interface JsonlSessionResolveOptions {
+	cwd?: string;
+	searchAll?: boolean;
+}
+
+export interface JsonlSessionRepoApi
+	extends SessionRepo<JsonlSessionMetadata, JsonlSessionCreateOptions, JsonlSessionRef, JsonlSessionListQuery> {
+	resolve(ref: string, options?: JsonlSessionResolveOptions): Promise<JsonlSessionMetadata[]>;
+	getMostRecent(query?: JsonlSessionListQuery): Promise<JsonlSessionMetadata | undefined>;
 }

 export interface AgentHarnessPendingMutations {
@@ -257,7 +271,7 @@ export interface AgentHarnessPendingMutations {
 }

 export interface AgentHarnessConversationState {
-	sessionTree: SessionTree;
+	session: Session;
 	model: Model<any> | undefined;
 	thinkingLevel: ThinkingLevel;
 	activeToolNames: string[];
@@ -284,8 +298,8 @@ export interface SavePointSnapshot {

 export interface AgentHarnessContext {
 	env: ExecutionEnv;
-	conversation: Readonly<AgentHarnessConversationState>;
-	operation: Readonly<AgentHarnessOperationState>;
+	conversation: AgentHarnessConversationState;
+	operation: AgentHarnessOperationState;
 	abortSignal?: AbortSignal;
 }

@@ -549,7 +563,7 @@ export interface BranchSummaryResult {
 export interface AgentHarnessOptions {
 	agent: Agent;
 	env: ExecutionEnv;
-	sessionTree: SessionTree;
+	session: Session;
 	promptTemplates?: PromptTemplate[];
 	skills?: Skill[];
 	requestAuth?: (model: Model<any>) => Promise<{ apiKey: string; headers?: Record<string, string> } | undefined>;
@@ -562,8 +576,8 @@ export interface AgentHarnessOptions {
 export interface AgentHarness {
 	readonly agent: Agent;
 	readonly env: ExecutionEnv;
-	readonly conversation: Readonly<AgentHarnessConversationState>;
-	readonly operation: Readonly<AgentHarnessOperationState>;
+	readonly conversation: AgentHarnessConversationState;
+	readonly operation: AgentHarnessOperationState;

 	prompt(text: string, options?: AgentHarnessPromptOptions): Promise<void>;
 	skill(name: string, args?: string): Promise<void>;
--- a/packages/agent/src/index.ts
+++ b/packages/agent/src/index.ts
@@ -25,6 +25,8 @@ export {
 export * from "./harness/execution-env.js";
 export * from "./harness/messages.js";
 export * from "./harness/prompt-templates.js";
+export * from "./harness/session/jsonl-session-repo.js";
+export * from "./harness/session/memory-session-repo.js";
 export * from "./harness/session/session-repo.js";
 export * from "./harness/session/session-tree.js";
 // Harness
--- a/packages/agent/test/harness/session-tree.test.ts
+++ b/packages/agent/test/harness/session-tree.test.ts
@@ -3,10 +3,12 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import { afterEach, describe, expect, it } from "vitest";
-import { JsonlSessionTreeStorage, loadJsonlSessionInfo } from "../../src/harness/session/jsonl-session-storage.js";
-import { InMemorySessionTreeStorage } from "../../src/harness/session/memory-session-storage.js";
-import { DefaultSessionTree } from "../../src/harness/session/session-tree.js";
-import type { MessageEntry, SessionInfo, SessionTreeStorage } from "../../src/harness/types.js";
+import { JsonlSessionRepo } from "../../src/harness/session/jsonl-session-repo.js";
+import { JsonlSessionStorage, loadJsonlSessionMetadata } from "../../src/harness/session/jsonl-session-storage.js";
+import { InMemorySessionRepo } from "../../src/harness/session/memory-session-repo.js";
+import { InMemorySessionStorage } from "../../src/harness/session/memory-session-storage.js";
+import { DefaultSession } from "../../src/harness/session/session-tree.js";
+import type { MessageEntry, SessionMetadata, SessionStorage } from "../../src/harness/types.js";

 function createUserMessage(text: string): AgentMessage {
 	return {
@@ -56,12 +58,12 @@ afterEach(() => {

 async function runSessionTreeSuite(
 	name: string,
-	createStorage: () => SessionTreeStorage | Promise<SessionTreeStorage>,
+	createStorage: () => SessionStorage | Promise<SessionStorage>,
 	inspect?: () => void,
 ) {
 	describe(name, () => {
 		it("appends messages and builds context in order", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			await tree.appendMessage(createUserMessage("one"));
 			await tree.appendMessage(createAssistantMessage("two"));
 			const context = await tree.buildContext();
@@ -69,7 +71,7 @@ async function runSessionTreeSuite(
 		});

 		it("tracks model and thinking level changes", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			await tree.appendMessage(createUserMessage("one"));
 			await tree.appendModelChange("openai", "gpt-4.1");
 			await tree.appendThinkingLevelChange("high");
@@ -79,7 +81,7 @@ async function runSessionTreeSuite(
 		});

 		it("supports branching by moving the leaf and appending a new branch", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			const user1 = await tree.appendMessage(createUserMessage("one"));
 			const assistant1 = await tree.appendMessage(createAssistantMessage("two"));
 			await tree.appendMessage(createUserMessage("three"));
@@ -93,7 +95,7 @@ async function runSessionTreeSuite(
 		});

 		it("supports moving the leaf to root", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			await tree.appendMessage(createUserMessage("one"));
 			await tree.moveTo(null);
 			expect(await tree.getLeafId()).toBeNull();
@@ -101,7 +103,7 @@ async function runSessionTreeSuite(
 		});

 		it("reconstructs compaction summaries in context", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			await tree.appendMessage(createUserMessage("one"));
 			await tree.appendMessage(createAssistantMessage("two"));
 			const user2 = await tree.appendMessage(createUserMessage("three"));
@@ -113,16 +115,19 @@ async function runSessionTreeSuite(
 			expect(context.messages).toHaveLength(4);
 		});

-		it("supports branch summary entries in context", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+		it("supports moving with branch summary entries in context", async () => {
+			const tree = new DefaultSession(await createStorage());
 			const user1 = await tree.appendMessage(createUserMessage("one"));
-			await tree.appendBranchSummary(user1, "summary text");
+			const summaryId = await tree.moveTo(user1, { summary: "summary text" });
+			expect(summaryId).toBeTruthy();
+			const summaryEntry = await tree.getEntry(summaryId!);
+			expect(summaryEntry).toMatchObject({ type: "branch_summary", parentId: user1, fromId: user1 });
 			const context = await tree.buildContext();
 			expect(context.messages[1]?.role).toBe("branchSummary");
 		});

 		it("supports custom message entries in context", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			await tree.appendMessage(createUserMessage("one"));
 			await tree.appendCustomMessageEntry("custom", "hello", true, { ok: true });
 			const context = await tree.buildContext();
@@ -130,10 +135,10 @@ async function runSessionTreeSuite(
 		});

 		it("supports labels and session info entries without affecting context", async () => {
-			const tree = new DefaultSessionTree(await createStorage());
+			const tree = new DefaultSession(await createStorage());
 			const user1 = await tree.appendMessage(createUserMessage("one"));
-			await tree.appendLabelChange(user1, "checkpoint");
-			await tree.appendSessionInfo("name");
+			await tree.appendLabel(user1, "checkpoint");
+			await tree.appendSessionName("name");
 			const entries = await tree.getEntries();
 			expect(entries.some((entry) => entry.type === "label")).toBe(true);
 			expect(entries.some((entry) => entry.type === "session_info")).toBe(true);
@@ -142,16 +147,21 @@ async function runSessionTreeSuite(
 			expect((await tree.buildContext()).messages).toHaveLength(1);
 		});

+		it("rejects labels for missing entries", async () => {
+			const tree = new DefaultSession(await createStorage());
+			await expect(tree.appendLabel("missing", "checkpoint")).rejects.toThrow("Entry missing not found");
+		});
+
 		it("persists leaf changes and appended entries via storage", async () => {
 			const storage = await createStorage();
-			const tree = new DefaultSessionTree(storage);
+			const tree = new DefaultSession(storage);
 			const user1 = await tree.appendMessage(createUserMessage("one"));
 			await tree.appendMessage(createAssistantMessage("two"));
-			await tree.appendLabelChange(user1, "checkpoint");
-			await tree.appendSessionInfo("name");
+			await tree.appendLabel(user1, "checkpoint");
+			await tree.appendSessionName("name");
 			await tree.moveTo(user1);
 			await tree.appendMessage(createAssistantMessage("branched"));
-			const tree2 = new DefaultSessionTree(storage);
+			const tree2 = new DefaultSession(storage);
 			const context = await tree2.buildContext();
 			expect(context.messages.map((message) => message.role)).toEqual(["user", "assistant"]);
 			expect(await tree2.getLabel(user1)).toBe("checkpoint");
@@ -161,11 +171,11 @@ async function runSessionTreeSuite(
 	});
 }

-describe("InMemorySessionTreeStorage", () => {
+describe("InMemorySessionStorage", () => {
 	it("returns configured session info", async () => {
-		const sessionInfo: SessionInfo = { id: "session-1", createdAt: "2026-01-01T00:00:00.000Z" };
-		const storage = new InMemorySessionTreeStorage({ sessionInfo });
-		expect(await storage.getSessionInfo()).toEqual(sessionInfo);
+		const metadata: SessionMetadata = { id: "session-1", createdAt: "2026-01-01T00:00:00.000Z" };
+		const storage = new InMemorySessionStorage({ metadata });
+		expect(await storage.getMetadata()).toEqual(metadata);
 	});

 	it("copies initial entries and tracks leaf independently", async () => {
@@ -177,7 +187,7 @@ describe("InMemorySessionTreeStorage", () => {
 			message: createUserMessage("one"),
 		};
 		const initialEntries = [entry];
-		const storage = new InMemorySessionTreeStorage({ entries: initialEntries });
+		const storage = new InMemorySessionStorage({ entries: initialEntries });
 		initialEntries.push({ ...entry, id: "entry-2" });
 		expect((await storage.getEntries()).map((storedEntry) => storedEntry.id)).toEqual(["entry-1"]);
 		expect(await storage.getLeafId()).toBe("entry-1");
@@ -186,9 +196,39 @@ describe("InMemorySessionTreeStorage", () => {
 	});

 	it("rejects invalid leaf ids", async () => {
-		const storage = new InMemorySessionTreeStorage();
+		const storage = new InMemorySessionStorage();
 		await expect(storage.setLeafId("missing")).rejects.toThrow("Entry missing not found");
-		expect(() => new InMemorySessionTreeStorage({ leafId: "missing" })).toThrow("Entry missing not found");
+		expect(() => new InMemorySessionStorage({ leafId: "missing" })).toThrow("Entry missing not found");
+	});
+
+	it("maintains label lookup", async () => {
+		const entry: MessageEntry = {
+			type: "message",
+			id: "entry-1",
+			parentId: null,
+			timestamp: "2026-01-01T00:00:00.000Z",
+			message: createUserMessage("one"),
+		};
+		const storage = new InMemorySessionStorage({ entries: [entry] });
+		expect(await storage.getLabel("entry-1")).toBeUndefined();
+		await storage.appendEntry({
+			type: "label",
+			id: "label-1",
+			parentId: "entry-1",
+			timestamp: "2026-01-01T00:00:01.000Z",
+			targetId: "entry-1",
+			label: "checkpoint",
+		});
+		expect(await storage.getLabel("entry-1")).toBe("checkpoint");
+		await storage.appendEntry({
+			type: "label",
+			id: "label-2",
+			parentId: "label-1",
+			timestamp: "2026-01-01T00:00:02.000Z",
+			targetId: "entry-1",
+			label: undefined,
+		});
+		expect(await storage.getLabel("entry-1")).toBeUndefined();
 	});

 	it("walks paths to root", async () => {
@@ -205,26 +245,70 @@ describe("InMemorySessionTreeStorage", () => {
 			parentId: "root",
 			message: createAssistantMessage("child"),
 		};
-		const storage = new InMemorySessionTreeStorage({ entries: [root, child] });
+		const storage = new InMemorySessionStorage({ entries: [root, child] });
 		expect((await storage.getPathToRoot("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
 		expect(await storage.getPathToRoot(null)).toEqual([]);
 	});
 });

-runSessionTreeSuite("SessionTree with in-memory storage", () => new InMemorySessionTreeStorage());
+runSessionTreeSuite("Session with in-memory storage", () => new InMemorySessionStorage());

-describe("JsonlSessionTreeStorage", () => {
+describe("InMemorySessionRepo", () => {
+	it("lists session infos and forks via storage path traversal", async () => {
+		const repo = new InMemorySessionRepo();
+		const session = await repo.create({ id: "session-1" });
+		const user1 = await session.appendMessage(createUserMessage("one"));
+		const assistant1 = await session.appendMessage(createAssistantMessage("two"));
+		const user2 = await session.appendMessage(createUserMessage("three"));
+		const infos = await repo.list();
+		expect(infos.map((info) => info.id)).toEqual(["session-1"]);
+		const fork = await repo.fork("session-1", { entryId: user2, id: "session-2" });
+		expect((await fork.getEntries()).map((entry) => entry.id)).toEqual([user1, assistant1]);
+	});
+});
+
+describe("JsonlSessionRepo", () => {
+	it("stores sessions below encoded cwd directories and resolves prefixes", async () => {
+		const root = createTempDir();
+		const cwd = "/tmp/my-project";
+		const repo = new JsonlSessionRepo({ sessionsRoot: root });
+		const session = await repo.create({ cwd, id: "019de8c2-de29-73e9-ae0c-e134db34c447" });
+		const info = await session.getMetadata();
+		expect(info.path).toContain("--tmp-my-project--");
+		expect(existsSync(info.path)).toBe(true);
+		expect((await repo.list({ cwd })).map((sessionInfo) => sessionInfo.id)).toEqual([info.id]);
+		expect((await repo.resolve("019de8c2", { cwd })).map((sessionInfo) => sessionInfo.path)).toEqual([info.path]);
+	});
+
+	it("forks sessions and records the parent path", async () => {
+		const root = createTempDir();
+		const repo = new JsonlSessionRepo({ sessionsRoot: root });
+		const source = await repo.create({ cwd: "/tmp/source", id: "source-session" });
+		const sourceInfo = await source.getMetadata();
+		const user1 = await source.appendMessage(createUserMessage("one"));
+		const assistant1 = await source.appendMessage(createAssistantMessage("two"));
+		const user2 = await source.appendMessage(createUserMessage("three"));
+		const fork = await repo.fork(sourceInfo, { cwd: "/tmp/target", id: "fork-session", entryId: user2 });
+		const forkInfo = await fork.getMetadata();
+		expect(forkInfo.cwd).toBe("/tmp/target");
+		expect(forkInfo.parentSessionPath).toBe(sourceInfo.path);
+		expect((await fork.getEntries()).map((entry) => entry.id)).toEqual([user1, assistant1]);
+	});
+});
+
+describe("JsonlSessionStorage", () => {
 	it("throws for missing files when opening", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
-		await expect(JsonlSessionTreeStorage.open(filePath)).rejects.toMatchObject({ code: "ENOENT" });
+		await expect(JsonlSessionStorage.open(filePath)).rejects.toMatchObject({ code: "ENOENT" });
 	});

-	it("writes the header before the first appended entry", async () => {
+	it("writes the header on create", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
-		const storage = await JsonlSessionTreeStorage.create(filePath, { cwd: dir, sessionId: "session-1" });
-		expect(existsSync(filePath)).toBe(false);
+		const storage = await JsonlSessionStorage.create(filePath, { cwd: dir, sessionId: "session-1" });
+		expect(existsSync(filePath)).toBe(true);
+		expect(readFileSync(filePath, "utf8").trim().split("\n")).toHaveLength(1);
 		expect(await storage.getLeafId()).toBeNull();
 		expect(await storage.getEntries()).toEqual([]);
 		await storage.appendEntry({
@@ -245,7 +329,7 @@ describe("JsonlSessionTreeStorage", () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
 		writeFileSync(filePath, "not json\n");
-		await expect(JsonlSessionTreeStorage.open(filePath)).rejects.toThrow("first line is not a valid session header");
+		await expect(JsonlSessionStorage.open(filePath)).rejects.toThrow("first line is not a valid session header");
 	});

 	it("ignores malformed entry lines", async () => {
@@ -266,7 +350,7 @@ describe("JsonlSessionTreeStorage", () => {
 			message: createUserMessage("one"),
 		};
 		writeFileSync(filePath, `${JSON.stringify(header)}\nnot json\n${JSON.stringify(entry)}\n`);
-		const storage = await JsonlSessionTreeStorage.open(filePath);
+		const storage = await JsonlSessionStorage.open(filePath);
 		expect((await storage.getEntries()).map((loadedEntry) => loadedEntry.id)).toEqual(["entry-1"]);
 		expect(await storage.getLeafId()).toBe("entry-1");
 	});
@@ -274,19 +358,19 @@ describe("JsonlSessionTreeStorage", () => {
 	it("creates and reads session info from the header", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
-		const storage = await JsonlSessionTreeStorage.create(filePath, {
+		const storage = await JsonlSessionStorage.create(filePath, {
 			cwd: dir,
 			sessionId: "session-1",
 			parentSessionPath: "/tmp/parent.jsonl",
 		});
-		const info = await storage.getSessionInfo();
+		const info = await storage.getMetadata();
 		expect(info).toMatchObject({
 			id: "session-1",
 			cwd: dir,
 			path: filePath,
 			parentSessionPath: "/tmp/parent.jsonl",
 		});
-		expect(existsSync(filePath)).toBe(false);
+		expect(existsSync(filePath)).toBe(true);
 		await storage.appendEntry({
 			type: "message",
 			id: "user-1",
@@ -294,13 +378,13 @@ describe("JsonlSessionTreeStorage", () => {
 			timestamp: "2026-01-01T00:00:00.000Z",
 			message: createUserMessage("one"),
 		});
-		expect(await loadJsonlSessionInfo(filePath)).toEqual(info);
+		expect(await loadJsonlSessionMetadata(filePath)).toEqual(info);
 	});

 	it("loads existing entries and reconstructs leaf", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
-		const storage = await JsonlSessionTreeStorage.create(filePath, { cwd: dir, sessionId: "session-1" });
+		const storage = await JsonlSessionStorage.create(filePath, { cwd: dir, sessionId: "session-1" });
 		const root: MessageEntry = {
 			type: "message",
 			id: "root",
@@ -316,12 +400,46 @@ describe("JsonlSessionTreeStorage", () => {
 		};
 		await storage.appendEntry(root);
 		await storage.appendEntry(child);
-		const loaded = await JsonlSessionTreeStorage.open(filePath);
+		const loaded = await JsonlSessionStorage.open(filePath);
 		expect(await loaded.getLeafId()).toBe("child");
 		expect((await loaded.getEntries()).map((entry) => entry.id)).toEqual(["root", "child"]);
 		expect((await loaded.getPathToRoot("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
 	});

+	it("maintains label lookup", async () => {
+		const dir = createTempDir();
+		const filePath = join(dir, "session.jsonl");
+		const storage = await JsonlSessionStorage.create(filePath, { cwd: dir, sessionId: "session-1" });
+		await storage.appendEntry({
+			type: "message",
+			id: "entry-1",
+			parentId: null,
+			timestamp: "2026-01-01T00:00:00.000Z",
+			message: createUserMessage("one"),
+		});
+		expect(await storage.getLabel("entry-1")).toBeUndefined();
+		await storage.appendEntry({
+			type: "label",
+			id: "label-1",
+			parentId: "entry-1",
+			timestamp: "2026-01-01T00:00:01.000Z",
+			targetId: "entry-1",
+			label: "checkpoint",
+		});
+		expect(await storage.getLabel("entry-1")).toBe("checkpoint");
+		await storage.appendEntry({
+			type: "label",
+			id: "label-2",
+			parentId: "label-1",
+			timestamp: "2026-01-01T00:00:02.000Z",
+			targetId: "entry-1",
+			label: undefined,
+		});
+		expect(await storage.getLabel("entry-1")).toBeUndefined();
+		const loaded = await JsonlSessionStorage.open(filePath);
+		expect(await loaded.getLabel("entry-1")).toBeUndefined();
+	});
+
 	it("reads session info from only the first JSONL line", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
@@ -334,7 +452,7 @@ describe("JsonlSessionTreeStorage", () => {
 		};
 		const malformedSecondLine = "{".repeat(10000);
 		writeFileSync(filePath, `${JSON.stringify(header)}\n${malformedSecondLine}\n`);
-		expect(await loadJsonlSessionInfo(filePath)).toEqual({
+		expect(await loadJsonlSessionMetadata(filePath)).toEqual({
 			id: "session-1",
 			createdAt: "2026-01-01T00:00:00.000Z",
 			cwd: dir,
@@ -345,10 +463,10 @@ describe("JsonlSessionTreeStorage", () => {
 });

 runSessionTreeSuite(
-	"SessionTree with JSONL storage",
+	"Session with JSONL storage",
 	async () => {
 		const dir = createTempDir();
-		return await JsonlSessionTreeStorage.create(join(dir, "session.jsonl"), { cwd: dir, sessionId: "session-1" });
+		return await JsonlSessionStorage.create(join(dir, "session.jsonl"), { cwd: dir, sessionId: "session-1" });
 	},
 	() => {
 		const dir = tempDirs[tempDirs.length - 1]!;