diff --git a/index.html b/index.html
index 6d76fef..8b6bd53 100644
--- a/index.html
+++ b/index.html
@@ -213,6 +213,60 @@
       };
     }
 
+    function safeJsonStringify(v) {
+      try { return JSON.stringify(v); } catch (_) { return String(v); }
+    }
+
+    function extractApiErrorDetails(payload) {
+      if (!payload) return '';
+      var err = payload.error || payload;
+      var parts = [];
+
+      if (typeof err === 'string') parts.push(err);
+      if (err && typeof err.message === 'string') parts.push(err.message);
+      if (err && typeof err.code === 'string') parts.push('code: ' + err.code);
+      if (err && typeof err.type === 'string') parts.push('type: ' + err.type);
+
+      if (err && err.metadata) {
+        var md = err.metadata;
+        if (md.provider_name) parts.push('provider: ' + md.provider_name);
+        if (md.raw && typeof md.raw === 'string') parts.push(md.raw);
+        if (md.reason) parts.push(md.reason);
+      }
+
+      if (err && err.details) {
+        if (typeof err.details === 'string') parts.push(err.details);
+        else parts.push(safeJsonStringify(err.details));
+      }
+
+      if (!parts.length) return '';
+      var seen = {};
+      var deduped = [];
+      for (var i = 0; i < parts.length; i++) {
+        var p = (parts[i] || '').trim();
+        if (!p || seen[p]) continue;
+        seen[p] = true;
+        deduped.push(p);
+      }
+      return deduped.join(' | ');
+    }
+
+    function parseErrorResponse(res) {
+      return res.text().then(function(raw) {
+        var json = null;
+        if (raw) {
+          try { json = JSON.parse(raw); } catch (_) {}
+        }
+
+        var detail = extractApiErrorDetails(json);
+        if (!detail && raw) detail = raw.trim();
+        if (!detail) detail = 'Unknown API error';
+
+        var statusPart = 'HTTP ' + res.status + (res.statusText ? ' ' + res.statusText : '');
+        return statusPart + ' — ' + detail;
+      });
+    }
+
     function generateFrame(opts) {
       var model = opts.model;
       var messages = opts.messages;
@@ -246,9 +300,7 @@
       })
       .then(function(res) {
         if (!res.ok) {
-          return res.json().catch(function() { return {}; }).then(function(e) {
-            throw new Error((e && e.error && e.error.message) || 'API error ' + res.status);
-          });
+          return parseErrorResponse(res).then(function(msg) { throw new Error(msg); });
         }
         return res.json();
       })
@@ -408,7 +460,8 @@
           setProgress(100, 'done! 🎉');
         })
         .catch(function(err) {
-          setProgress(0, 'error: ' + err.message);
+          var msg = (err && err.message) ? err.message : String(err);
+          setProgress(0, 'error: ' + msg);
           console.error('vibegif error:', err);
         })
         .then(function() {