Fix markdown highlight render stability

apps/web/src/components/ChatMarkdown.tsx

@@ -211,6 +211,32 @@ function SuspenseShikiCodeBlock({
     );
   }
 
+  return (
+    <UncachedShikiCodeBlock
+      code={code}
+      language={language}
+      themeName={themeName}
+      cacheKey={cacheKey}
+      isStreaming={isStreaming}
+    />
+  );
+}
+
+interface UncachedShikiCodeBlockProps {
+  code: string;
+  language: string;
+  themeName: DiffThemeName;
+  cacheKey: string;
+  isStreaming: boolean;
+}
+
+function UncachedShikiCodeBlock({
+  code,
+  language,
+  themeName,
+  cacheKey,
+  isStreaming,
+}: UncachedShikiCodeBlockProps) {
   const highlighter = use(getHighlighterPromise(language));
   const highlightedHtml = useMemo(() => {
     try {

apps/web/src/components/chat/MessagesTimeline.tsx

@@ -87,6 +87,8 @@ interface TimelineRowSharedState {
 }
 
 const TimelineRowCtx = createContext<TimelineRowSharedState>(null!);
+const TIMELINE_LIST_HEADER = <div className="h-3 sm:h-4" />;
+const TIMELINE_LIST_FOOTER = <div className="h-3 sm:h-4" />;
 
 // ---------------------------------------------------------------------------
 // Props (public API)
@@ -261,8 +263,8 @@ export const MessagesTimeline = memo(function MessagesTimeline({
         maintainVisibleContentPosition
         onScroll={handleScroll}
         className="h-full overflow-x-hidden overscroll-y-contain px-3 sm:px-5"
-        ListHeaderComponent={<div className="h-3 sm:h-4" />}
-        ListFooterComponent={<div className="h-3 sm:h-4" />}
+        ListHeaderComponent={TIMELINE_LIST_HEADER}
+        ListFooterComponent={TIMELINE_LIST_FOOTER}
       />
     </TimelineRowCtx.Provider>
   );