diff --git a/tests/e2e/process-end-once.e2e.ts b/tests/e2e/process-end-once.e2e.ts
new file mode 100644
index 0000000..e75f052
--- /dev/null
+++ b/tests/e2e/process-end-once.e2e.ts
@@ -0,0 +1,29 @@
+import { expect } from "vitest";
+import { getManager } from "../../src/get-manager";
+import { test } from "./fixtures";
+import { collectEvents, waitForEnd } from "./utils";
+
+/**
+ * A process that exits on its own must emit exactly one `process_ended`.
+ * A duplicate emit reaches the notification service twice and the agent
+ * receives the same lifecycle notification twice.
+ */
+test("emits process_ended once for a process that exits on its own", async ({
+  cwd,
+}) => {
+  using manager = getManager();
+  const events = collectEvents(manager);
+
+  const info = manager.start("short-lived", "sleep 0.2; echo done", cwd);
+
+  await waitForEnd(manager, info.id);
+  // The liveness tick runs every 5s; give it a chance to re-classify a
+  // record that the close handler already finalized.
+  await new Promise((resolve) => setTimeout(resolve, 6000));
+
+  const ended = events.filter(
+    (event) => event.type === "process_ended" && event.info.id === info.id,
+  );
+
+  expect(ended).toHaveLength(1);
+}, 15000);