diff --git a/ui/litellm-dashboard/src/components/playground/chat_ui/ResponsesImageUtils.tsx b/ui/litellm-dashboard/src/components/playground/chat_ui/ResponsesImageUtils.tsx
index 6d327f41bf0..b36d05c10aa 100644
--- a/ui/litellm-dashboard/src/components/playground/chat_ui/ResponsesImageUtils.tsx
+++ b/ui/litellm-dashboard/src/components/playground/chat_ui/ResponsesImageUtils.tsx
@@ -21,9 +21,11 @@ export const sanitizeImageSrc = (url: string | undefined): string => {
     ) {
       return parsed.href;
     }
-    // Restrict data: URIs to image and PDF MIME types only
+    // Restrict data: URIs to image and PDF MIME types only.
+    // Split on both ';' and ',' to handle both `data:type;base64,...`
+    // and `data:type,...` (non-base64 inline) formats.
     if (proto === "data:") {
-      const mime = parsed.pathname.split(";")[0].toLowerCase();
+      const mime = parsed.pathname.split(/[;,]/)[0].toLowerCase();
       if (mime.startsWith("image/") || mime === "application/pdf") {
         return parsed.href;
       }
diff --git a/ui/litellm-dashboard/src/utils/storageUtils.ts b/ui/litellm-dashboard/src/utils/storageUtils.ts
index b7db5a2c614..d723c4bdc94 100644
--- a/ui/litellm-dashboard/src/utils/storageUtils.ts
+++ b/ui/litellm-dashboard/src/utils/storageUtils.ts
@@ -14,11 +14,13 @@
  */
 function utf8ToBase64(str: string): string {
   const bytes = new TextEncoder().encode(str);
-  let binary = "";
-  for (const b of bytes) {
-    binary += String.fromCharCode(b);
+  // Use chunked String.fromCharCode to avoid O(n²) string concatenation
+  const chunks: string[] = [];
+  const chunkSize = 8192;
+  for (let i = 0; i < bytes.length; i += chunkSize) {
+    chunks.push(String.fromCharCode(...bytes.subarray(i, i + chunkSize)));
   }
-  return btoa(binary);
+  return btoa(chunks.join(""));
 }
 
 /**