test(e2e): expand ChatThread reasoning and tool parts

Author: TheGreatAxios

tests/e2e/chat-thread.spec.ts

@@ -0,0 +1,19 @@
+import { expect, test } from "@playwright/test";
+
+test("an agent turn renders its reasoning and tool parts, each expanding on click", async ({ page }) => {
+  await page.goto("/chat-thread");
+  const turn = page.getByRole("article", { name: "Scout replied" });
+  await expect(turn.getByText("Three commits landed today.")).toBeVisible();
+
+  const reasoning = turn.locator("details");
+  await expect(reasoning).not.toHaveAttribute("open");
+  await reasoning.locator("summary").click();
+  await expect(reasoning).toHaveAttribute("open");
+  await expect(reasoning.getByText("Check the commit log first.")).toBeVisible();
+
+  const tool = turn.getByRole("button", { name: /Read today's commits/ });
+  await expect(tool).toHaveAttribute("aria-expanded", "false");
+  await tool.click();
+  await expect(tool).toHaveAttribute("aria-expanded", "true");
+  await expect(turn.getByText("3 commits")).toBeVisible();
+});