diff --git a/src/features/workbench/components/presentation-history-menu.tsx b/src/features/workbench/components/presentation-history-menu.tsx
index 1d652cd..d2072cf 100644
--- a/src/features/workbench/components/presentation-history-menu.tsx
+++ b/src/features/workbench/components/presentation-history-menu.tsx
@@ -15,7 +15,7 @@ function subscribeCompact(listener: () => void) {
   media.addEventListener("change", listener);
   return () => media.removeEventListener("change", listener);
 }
-const rowClass = "min-h-8 gap-2 text-xs active:bg-accent";
+const rowClass = "min-h-8 gap-2 text-xs transition-none active:bg-accent";
 
 export function PresentationHistoryMenu({ entries, selectedId, mergedEntry, mergedEntries, onSelect }: PresentationHistoryControls) {
   const [open, setOpen] = useState(false);
diff --git a/tests/browser/button-system.e2e.ts b/tests/browser/button-system.e2e.ts
index 4835042..f678dd9 100644
--- a/tests/browser/button-system.e2e.ts
+++ b/tests/browser/button-system.e2e.ts
@@ -6,6 +6,40 @@ test.beforeEach(async ({ page }) => {
   await prepareWorkbench(page);
 });
 
+for (const width of [1440, 1024, 375, 320]) {
+  test(`header hides and restores the expanded timeline at ${width}px`, async ({ page }, testInfo) => {
+    await page.setViewportSize({ width, height: 900 });
+    await page.goto("/", { waitUntil: "domcontentloaded" });
+    const header = page.locator(".workbench-top-bar");
+    const timeline = page.getByRole("region", {
+      name: width >= 1024 ? "运行时间轴" : "移动端运行时间轴摘要", exact: true
+    });
+    const hide = header.getByRole("button", { name: "隐藏运行时间轴", exact: true });
+    await expect(timeline).toBeVisible();
+    await expect(hide).toHaveAttribute("aria-pressed", "true");
+    const bounds = (await hide.boundingBox())!;
+    expect(bounds.x).toBeGreaterThanOrEqual(0);
+    expect(bounds.x + bounds.width).toBeLessThanOrEqual(width);
+    if (width >= 1024) await timeline.getByRole("button", { name: "展开时间轴", exact: true }).click();
+    else {
+      await timeline.getByRole("button", { name: "打开完整运行时间轴", exact: true }).click();
+      await expect(page.getByRole("region", { name: "运行时间轴抽屉", exact: true })).toBeVisible();
+    }
+    await hide.click();
+    await expect(timeline).toBeHidden();
+    await expect(page.getByRole("region", { name: "运行时间轴抽屉", exact: true })).toBeHidden();
+    const show = header.getByRole("button", { name: "显示运行时间轴", exact: true });
+    await expect(show).toHaveAttribute("aria-pressed", "false");
+    await show.click();
+    await expect(timeline).toBeVisible();
+    await expect(hide).toHaveAttribute("aria-pressed", "true");
+    if (width >= 1024) await expect(timeline.getByRole("button", { name: "收起时间轴", exact: true })).toBeVisible();
+    await testInfo.attach(`header-timeline-${width}`, {
+      body: await header.screenshot(), contentType: "image/png"
+    });
+  });
+}
+
 test("desktop controls share focus, hover, press and open states", async ({ page }) => {
   await page.setViewportSize({ width: 1440, height: 900 });
   await page.goto("/", { waitUntil: "domcontentloaded" });
diff --git a/tests/browser/investigation-merged-history.e2e.ts b/tests/browser/investigation-merged-history.e2e.ts
index 8109326..d82dc4f 100644
--- a/tests/browser/investigation-merged-history.e2e.ts
+++ b/tests/browser/investigation-merged-history.e2e.ts
@@ -1,9 +1,25 @@
-import { expect, test, type Page, type TestInfo } from "@playwright/test";
+import { expect, test, type Locator, type Page, type TestInfo } from "@playwright/test";
 import { investigationFixture, mockInvestigationPresentation, selectInvestigation, showInvestigationMap } from "./support/mock-investigation-presentation";
+import { readThemeColor } from "./support/theme-colors";
 
 const chart = (id: string, title: string) => ({ action: "open_chart", chart_id: id, evidence_refs: ["synthetic:reading"],
   chart: { title, chart_type: "line", x_data: ["08:00", "08:15"], series: [{ name: "压力（m）", data: [30, 28] }] } });
 
+async function sampleFastHoverBackground(items: Locator[]) {
+  const samples: Array<{ actual: string; expected: string }> = [];
+  for (let repeat = 0; repeat < 3; repeat++) {
+    for (const item of items) {
+      const expected = await readThemeColor(item, "--action-selection-soft");
+      await item.hover();
+      const actual = await item.evaluate((node) => new Promise<string>((resolve) => {
+        requestAnimationFrame(() => resolve(getComputedStyle(node).backgroundColor));
+      }));
+      samples.push({ actual, expected });
+    }
+  }
+  return samples;
+}
+
 async function captureMenus(page: Page, testInfo: TestInfo, name: string) {
   for (const menu of await page.getByRole("menu").all()) {
     await menu.evaluate((node) => Promise.all(node.getAnimations().map((animation) => animation.finished.catch(() => undefined))));
@@ -56,8 +72,18 @@ test("hover keeps an expanded category stable across its title, arrow and origin
   const arrow = root.getByRole("menuitem", { name: "展开图表步骤", exact: true });
   const title = root.getByRole("menuitem", { name: "图表", exact: true });
   const steps = page.getByRole("menu", { name: "图表展示步骤", exact: true });
+  const firstLevel = await sampleFastHoverBackground([title, root.getByRole("menuitem", { name: "覆盖层", exact: true })]);
   await arrow.hover();
   await expect(steps).toBeVisible();
+  const secondLevel = await sampleFastHoverBackground([
+    steps.getByRole("menuitem", { name: "1. 测点 P1 压力趋势", exact: true }),
+    steps.getByRole("menuitem", { name: "2. 测点 P2 压力趋势", exact: true })
+  ]);
+  const backgrounds = [...firstLevel, ...secondLevel];
+  await testInfo.attach("fast-hover-backgrounds", { body: JSON.stringify({ firstLevel, secondLevel }), contentType: "application/json" });
+  expect(backgrounds).toHaveLength(12);
+  expect(backgrounds.every((sample) => sample.expected !== "rgba(0, 0, 0, 0)")).toBe(true);
+  expect(backgrounds.map((sample) => sample.actual)).toEqual(backgrounds.map((sample) => sample.expected));
   await page.evaluate(() => {
     const changes: string[] = [];
     const observer = new MutationObserver((records) => {