diff --git a/sdks/typescript-agent-sdk/tests/noop-roundtrip.test.ts b/sdks/typescript-agent-sdk/tests/noop-roundtrip.test.ts
new file mode 100644
index 00000000000..db565cd993d
--- /dev/null
+++ b/sdks/typescript-agent-sdk/tests/noop-roundtrip.test.ts
@@ -0,0 +1,73 @@
+/**
+ * Validation #2 — Round-trip against noop proxy.
+ *
+ * Verifies: Agent.create -> agent.createSession -> session.send -> for await
+ * stream -> session.getRun.
+ */
+
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { Agent } from "../src/index.js";
+import { MockProxy } from "./mock-proxy.js";
+
+describe("noop round-trip", () => {
+  let proxy: MockProxy;
+  let baseUrl: string;
+
+  beforeEach(async () => {
+    proxy = new MockProxy();
+    baseUrl = await proxy.start();
+  });
+
+  afterEach(async () => {
+    await proxy.stop();
+  });
+
+  it("creates an agent, opens a session, runs a prompt, and streams events to completion", async () => {
+    const agent = await Agent.create({
+      apiKey: "test-key",
+      baseUrl,
+      name: "round-tripper",
+      model: { id: "test-model" },
+    });
+
+    expect(agent.id).toMatch(/^agt_/);
+    expect(agent.name).toBe("round-tripper");
+
+    const session = await agent.createSession({
+      repos: [{ url: "https://github.com/example/repo", startingRef: "main" }],
+    });
+    expect(session.id).toMatch(/^ses_/);
+    expect(session.agentId).toBe(agent.id);
+
+    const run = await session.send("hello world");
+    expect(run.id).toMatch(/^run_/);
+    expect(run.sessionId).toBe(session.id);
+
+    // Drive the run from the proxy side.
+    const driver = (async () => {
+      // Tiny delay so the SDK is connected to /events before we emit.
+      await new Promise((r) => setTimeout(r, 25));
+      proxy.emit(run.id, "delta", { text: "hi " });
+      proxy.emit(run.id, "delta", { text: "there" });
+      proxy.complete(run.id, "hi there");
+    })();
+
+    const collected: { type: string; data: unknown; seq: number }[] = [];
+    for await (const ev of run.stream()) {
+      collected.push({ type: ev.type, data: ev.data, seq: ev.seq });
+    }
+    await driver;
+
+    // Sanity: at least both deltas + done arrived in seq order.
+    expect(collected.map((e) => e.type)).toContain("delta");
+    expect(collected.at(-1)?.type).toBe("done");
+    const seqs = collected.map((e) => e.seq);
+    expect(seqs).toEqual([...seqs].sort((a, b) => a - b));
+
+    // Re-fetch the run by ID and confirm the terminal status.
+    const fetched = await session.getRun(run.id);
+    expect(fetched.id).toBe(run.id);
+    expect(fetched.status).toBe("completed");
+    expect(fetched.result).toBe("hi there");
+  });
+});