diff --git a/packages/ui/stories/toast.stories.tsx b/packages/ui/stories/toast.stories.tsx
index 58ebeaa7f2..90916e5b4d 100644
--- a/packages/ui/stories/toast.stories.tsx
+++ b/packages/ui/stories/toast.stories.tsx
@@ -111,3 +111,130 @@ export const ConfirmQueued: Story = {
     await expect(opener).toHaveFocus();
   },
 };
+
+// The diagnostics affordance the provider wires onto every error toast — and
+// the branch where opening it also fails, so the provider raises its own
+// failure toast instead of swallowing the rejection.
+const DIAGNOSTICS_ERROR_ACTION = {
+  label: '查看详情',
+  failureTitle: '无法打开诊断',
+  failureDescription: '日志服务未响应，请稍后重试。',
+  onClick: async () => {
+    throw new Error('diagnostics unavailable');
+  },
+};
+
+// Real trigger: any failed operation surfaced through `toast.error` (a failed
+// save, an offline sync, an unauthorised request — this surface has one error
+// affordance, so they all share its shape). A bare `error` variant never
+// exercises the action button or its own failure path.
+export const ErrorWithDiagnostics: Story = {
+  decorators: [
+    (Story) => (
+      <ToastProvider errorAction={DIAGNOSTICS_ERROR_ACTION}>
+        <Story />
+      </ToastProvider>
+    ),
+  ],
+  render: () => {
+    const toast = useToast();
+    useEffect(() => {
+      toast.toast({
+        title: '保存失败',
+        description: '网络中断，更改未同步。',
+        variant: 'error',
+        duration: 0,
+      });
+    }, [toast]);
+    return <div style={{ minHeight: 360 }} />;
+  },
+  play: async () => {
+    const page = within(document.body);
+    // The error toast carries the provider's diagnostics action…
+    const diagnostics = await page.findByRole('button', { name: '查看详情' });
+    await userEvent.click(diagnostics);
+    // …and when that action itself fails, the provider surfaces its own
+    // failure toast rather than dropping the rejection on the floor.
+    await page.findByText('无法打开诊断');
+  },
+};
+
+function DestructiveConfirmExample() {
+  const toast = useToast();
+  return (
+    <div style={{ display: 'grid', gap: 12, padding: 24, width: 360 }}>
+      <Button
+        variant="secondary"
+        label="删除项目"
+        onClick={() => {
+          void toast.confirm({
+            title: '删除项目？',
+            description: '此操作会移除该项目的全部本地记录，且不可撤销。',
+            confirmLabel: '删除',
+            cancelLabel: '取消',
+            destructive: true,
+          });
+        }}
+      />
+    </div>
+  );
+}
+
+// Real trigger: an irreversible action (delete a project / task). The confirm
+// button wears the destructive variant and initial focus rests on cancel, so
+// the dangerous path is never the default.
+export const DestructiveConfirm: Story = {
+  render: () => <DestructiveConfirmExample />,
+  play: async ({ canvasElement }) => {
+    const canvas = within(canvasElement);
+    const page = within(document.body);
+    await userEvent.click(canvas.getByRole('button', { name: '删除项目' }));
+    const dialog = await page.findByRole('alertdialog', { name: '删除项目？' });
+    await expect(within(dialog).getByRole('button', { name: '删除' })).toBeInTheDocument();
+    // The least-destructive choice holds initial focus.
+    await expect(within(dialog).getByRole('button', { name: '取消' })).toHaveFocus();
+  },
+};
+
+const LONG_TOAST_TITLE =
+  '同步到远程工作区时发生了一个需要你注意的、标题本身就相当冗长的问题';
+const LONG_TOAST_DESCRIPTION =
+  '远程主机在多次重试后仍未确认写入：连接在握手阶段被重置，随后的退避重试也接连超时。' +
+  '本地更改已安全保留，你可以稍后重新同步；这段说明刻意写得很长，用来检验 toast 卡片在多行文本下是否仍然清晰，而不会把操作区挤出可视范围。';
+
+// Very long title and body: the card must wrap legibly rather than clip text
+// or shove the layout off-screen.
+export const LongContent: Story = {
+  render: () => {
+    const toast = useToast();
+    useEffect(() => {
+      toast.toast({
+        title: LONG_TOAST_TITLE,
+        description: LONG_TOAST_DESCRIPTION,
+        variant: 'warning',
+        duration: 0,
+      });
+    }, [toast]);
+    return <div style={{ minHeight: 360 }} />;
+  },
+};
+
+// Many notifications at once — a burst of background results stacking up.
+// Exercises the stack's density and whatever cap or scroll the layer applies,
+// which a single seeded toast never shows.
+export const ManyStacked: Story = {
+  render: () => {
+    const toast = useToast();
+    useEffect(() => {
+      for (let i = 1; i <= 8; i += 1) {
+        toast.toast({
+          title: `后台任务 ${i} 已完成`,
+          description: `第 ${i} 条通知的说明文字。`,
+          variant: VARIANTS[i % VARIANTS.length]!,
+          duration: 0,
+        });
+      }
+    }, [toast]);
+    return <div style={{ minHeight: 360 }} />;
+  },
+};