diff --git a/packages/server/src/server/agent/providers/codex/stdin-close.local.test.ts b/packages/server/src/server/agent/providers/codex/stdin-close.local.test.ts
new file mode 100644
index 0000000000..3a92cf273c
--- /dev/null
+++ b/packages/server/src/server/agent/providers/codex/stdin-close.local.test.ts
@@ -0,0 +1,19 @@
+import { spawn } from "node:child_process";
+import { once } from "node:events";
+import { test, expect } from "vitest";
+import { createTestLogger } from "../../../../test-utils/test-logger.js";
+import { CodexAppServerClient } from "./app-server-transport.js";
+
+test("a provider that closes stdin rejects initialization without an uncaught stream error", async () => {
+  const child = spawn("/bin/sh", ["-c", "exec 0<&-; printf READY; sleep 0.2; exit 86"], {
+    stdio: "pipe",
+  });
+  const ready = once(child.stdout, "data");
+  const client = new CodexAppServerClient(child, createTestLogger());
+  try {
+    await ready;
+    await expect(client.request("initialize", {})).rejects.toThrow(/86/);
+  } finally {
+    await client.dispose();
+  }
+});