From 07be260245454c7dc84c44ef9b092ab81df6b5e3 Mon Sep 17 00:00:00 2001
From: imccyu <cc.yu@deepseek.com>
Date: Mon, 31 Aug 2026 22:11:39 +0800
Subject: [PATCH] test(ui-primitives): cover lazy viewport highlighting

---
 .../tests/highlight-viewport.client.spec.tsx        | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/packages/client/ui-primitives/tests/highlight-viewport.client.spec.tsx b/packages/client/ui-primitives/tests/highlight-viewport.client.spec.tsx
index 6dfdb1bd3a..5c7e8816e8 100644
--- a/packages/client/ui-primitives/tests/highlight-viewport.client.spec.tsx
+++ b/packages/client/ui-primitives/tests/highlight-viewport.client.spec.tsx
@@ -125,6 +125,19 @@ describe('viewport-activated syntax highlighting', () => {
     expect(view.container.querySelector('pre.shiki')).not.toBeNull()
   })
 
+  it('keeps an intersecting streaming block plain until its lazy grammar loads', async () => {
+    const view = render(
+      <CodeBlock code="print(1)" lang="python" streaming {...markdownLabels.code} />,
+    )
+    const block = view.container.querySelector('.md-code-block')!
+    const observer = IntersectionObserverStub.instances[0]!
+
+    act(() => { observer.intersect(block, true) })
+    expect(block.querySelector('pre.shiki')).toBeNull()
+
+    await waitFor(() => { expect(block.querySelector('pre.shiki')).not.toBeNull() }, { timeout: 5_000 })
+  })
+
   it('keeps a read card plain until that card intersects', async () => {
     const view = render(
       <ReadBlock