diff --git a/ui/litellm-dashboard/e2e_tests/tests/agents/composer.spec.ts b/ui/litellm-dashboard/e2e_tests/tests/agents/composer.spec.ts
new file mode 100644
index 00000000000..ec706db70b1
--- /dev/null
+++ b/ui/litellm-dashboard/e2e_tests/tests/agents/composer.spec.ts
@@ -0,0 +1,26 @@
+/**
+ * LIT-2881 Validation #6 — Followup composer.
+ *
+ * Type message + send. user_message bubble appears (mock provider).
+ * (assistant_message follows in real proxy mode; the mock client only
+ * acks the user_message synchronously, which is enough to verify the
+ * composer plumbing.)
+ */
+import { test, expect } from "@playwright/test";
+import { AGENTS_DEV_URL, authenticateAgentsPage } from "./_helpers";
+
+test("composer send surfaces a user_message in the conversation pane", async ({ page }) => {
+  await authenticateAgentsPage(page);
+  await page.goto(`${AGENTS_DEV_URL}/agents/agt_01/sessions/ses_01`);
+  await expect(page.getByTestId("composer")).toBeVisible();
+
+  const userBubblesBefore = await page.getByTestId("message-bubble-user").count();
+
+  await page.getByTestId("composer-input").fill("ping from e2e");
+  await page.getByTestId("composer-send").click();
+
+  // user_message bubble count strictly grows
+  await expect
+    .poll(async () => page.getByTestId("message-bubble-user").count(), { timeout: 5_000 })
+    .toBeGreaterThan(userBubblesBefore);
+});