diff --git a/features/workbench/layout/workbench-layout.ts b/features/workbench/layout/workbench-layout.ts
index f29f9f1..0d8f512 100644
--- a/features/workbench/layout/workbench-layout.ts
+++ b/features/workbench/layout/workbench-layout.ts
@@ -3,7 +3,7 @@ export const WORKBENCH_LAYOUT = {
   desktopMinWidth: 1024,
   persistentConditionMinWidth: 1280,
   wideMinWidth: 1536,
-  collapsedAgentWidth: 136,
+  collapsedAgentWidth: 72,
   maxAgentViewportRatio: 0.5,
   mapEdgeGap: 24,
   desktop: {
diff --git a/tests/browser/agent-panel-resize.e2e.ts b/tests/browser/agent-panel-resize.e2e.ts
index dbb1090..063afb6 100644
--- a/tests/browser/agent-panel-resize.e2e.ts
+++ b/tests/browser/agent-panel-resize.e2e.ts
@@ -25,6 +25,21 @@ test("Agent panel resizes by drag without exceeding half the viewport", async ({
   await expect.poll(async () => (await panel.boundingBox())?.width).toBe(476);
 });
 
+test("collapsed Agent rail is compact and expands as one clear action", async ({ page }) => {
+  await page.goto("/", { waitUntil: "networkidle" });
+
+  await page.getByRole("button", { name: "折叠 Agent 面板" }).click();
+
+  const rail = page.locator('aside[aria-label="Agent 折叠栏"]');
+  const expandButton = page.getByRole("button", { name: /展开排水助手面板/ });
+  await expect(rail).toBeVisible();
+  await expect(rail).toHaveCSS("width", "72px");
+  await expect(expandButton).toHaveAttribute("title", /当前|正在/);
+
+  await expandButton.click();
+  await expect(page.locator('aside[aria-label="Agent 命令面板"]')).toBeVisible();
+});
+
 test("Agent resize handle stays hidden in the mobile layout", async ({ page }) => {
   await page.setViewportSize({ width: 375, height: 812 });
   await page.goto("/", { waitUntil: "domcontentloaded" });