feat(agent): add harness factory helpers

packages/agent/src/harness/factory.ts

@@ -0,0 +1,13 @@
+import { DefaultAgentHarness } from "./agent-harness.js";
+import { DefaultSession } from "./session/session.js";
+import type { AgentHarness, AgentHarnessOptions, Session, SessionMetadata, SessionStorage } from "./types.js";
+
+export function createSession<TMetadata extends SessionMetadata>(
+	storage: SessionStorage<TMetadata>,
+): Session<TMetadata> {
+	return new DefaultSession(storage);
+}
+
+export function createAgentHarness(options: AgentHarnessOptions): AgentHarness {
+	return new DefaultAgentHarness(options);
+}

packages/agent/src/index.ts

@@ -23,6 +23,7 @@ export {
 	shouldCompact,
 } from "./harness/compaction/compaction.js";
 export * from "./harness/execution-env.js";
+export * from "./harness/factory.js";
 export * from "./harness/messages.js";
 export * from "./harness/prompt-templates.js";
 export * from "./harness/session/repo/jsonl.js";

packages/agent/test/harness/factory.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+import { Agent } from "../../src/agent.js";
+import { NodeExecutionEnv } from "../../src/harness/execution-env.js";
+import { createAgentHarness, createSession } from "../../src/harness/factory.js";
+import { InMemorySessionStorage } from "../../src/harness/session/storage/memory.js";
+
+describe("harness factories", () => {
+	it("creates sessions from storage", async () => {
+		const storage = new InMemorySessionStorage({
+			metadata: { id: "session-1", createdAt: "2026-01-01T00:00:00.000Z" },
+		});
+		const session = createSession(storage);
+		expect(session.getStorage()).toBe(storage);
+		expect(await session.getMetadata()).toEqual({ id: "session-1", createdAt: "2026-01-01T00:00:00.000Z" });
+	});
+
+	it("creates agent harnesses", () => {
+		const session = createSession(new InMemorySessionStorage());
+		const env = new NodeExecutionEnv({ cwd: process.cwd() });
+		const agent = new Agent();
+		const harness = createAgentHarness({ agent, env, session });
+		expect(harness.agent).toBe(agent);
+		expect(harness.conversation.session).toBe(session);
+	});
+});