diff --git a/apps/web/src/components/ChatMarkdown.tsx b/apps/web/src/components/ChatMarkdown.tsx
index da44045c98aa1adb4de2baee025ec8fa4967363b..f4298fc22208ac664a1b0c7b9ec6699aa0cf2e59 100644
--- a/apps/web/src/components/ChatMarkdown.tsx
+++ b/apps/web/src/components/ChatMarkdown.tsx
@@ -66,7 +66,9 @@ const highlighterPromiseCache = new Map<string, Promise<DiffsHighlighter>>();
 
 function extractFenceLanguage(className: string | undefined): string {
   const match = className?.match(CODE_FENCE_LANGUAGE_REGEX);
-  return match?.[1] ?? "text";
+  const raw = match?.[1] ?? "text";
+  // Shiki doesn't bundle a gitignore grammar; ini is a close match (#685)
+  return raw === "gitignore" ? "ini" : raw;
 }
 
 function nodeToPlainText(node: ReactNode): string {