test(agent-sdk): add agent-reuse multi-session test

sdks/typescript-agent-sdk/tests/agent-reuse.test.ts

@@ -0,0 +1,59 @@
+/**
+ * Validation #3 — Agent reuse across sessions.
+ *
+ * Creates ONE agent, then 3 sessions under it. Asserts: same agentId,
+ * distinct sessionIds, distinct VMs.
+ */
+
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { Agent } from "../src/index.js";
+import { MockProxy } from "./mock-proxy.js";
+
+describe("agent reuse across sessions", () => {
+  let proxy: MockProxy;
+  let baseUrl: string;
+
+  beforeEach(async () => {
+    proxy = new MockProxy();
+    baseUrl = await proxy.start();
+  });
+
+  afterEach(async () => {
+    await proxy.stop();
+  });
+
+  it("creates 3 sessions under one agent with distinct IDs and distinct VMs", async () => {
+    const agent = await Agent.create({
+      apiKey: "test-key",
+      baseUrl,
+      name: "shared",
+      model: { id: "test-model" },
+    });
+
+    const sessions = await Promise.all([
+      agent.createSession(),
+      agent.createSession(),
+      agent.createSession(),
+    ]);
+
+    // All sessions share the agent ID.
+    for (const s of sessions) {
+      expect(s.agentId).toBe(agent.id);
+    }
+
+    // Session IDs are unique.
+    const ids = sessions.map((s) => s.id);
+    expect(new Set(ids).size).toBe(3);
+
+    // Mock proxy assigns each session a distinct VM ID.
+    const proxyAgent = proxy.agents.get(agent.id);
+    expect(proxyAgent).toBeDefined();
+    const vmIds = [...proxyAgent!.sessions.values()].map((s) => s.vmId);
+    expect(new Set(vmIds).size).toBe(3);
+
+    // listSessions reflects all 3.
+    const listed = await agent.listSessions();
+    expect(listed.items.length).toBe(3);
+    expect(new Set(listed.items.map((i) => i.id))).toEqual(new Set(ids));
+  });
+});