diff --git a/src/pages/Viewer.tsx b/src/pages/Viewer.tsx
index b3b9bc8..d1282ba 100644
--- a/src/pages/Viewer.tsx
+++ b/src/pages/Viewer.tsx
@@ -44,7 +44,22 @@ const Viewer = () => {
       toast.error('Formato inválido. Selecione .GLB, .OBJ, .STL ou .IFC');
       return;
     }
+    const sizeCheck = validateModelFile(file.name, file.size, ext);
+    if (!sizeCheck.ok) {
+      toast.error(sizeCheck.reason!);
+      return;
+    }
     if (ext === 'glb') {
+      try {
+        const head = await file.slice(0, 16).arrayBuffer();
+        const sig = validateModelFile(file.name, file.size, ext, head);
+        if (!sig.ok) {
+          toast.error(sig.reason!);
+          return;
+        }
+      } catch (err) {
+        console.error('[upload] header read failed', err);
+      }
       const url = URL.createObjectURL(file);
       addModel({ fileName: file.name, fileSize: file.size, url });
       toast.success(`"${file.name}" adicionado à cena`);
@@ -53,6 +68,12 @@ const Viewer = () => {
     setConverting(true);
     try {
       const buffer = await file.arrayBuffer();
+      const sig = validateModelFile(file.name, file.size, ext, buffer);
+      if (!sig.ok) {
+        toast.error(sig.reason!);
+        if (sig.detail) console.warn('[validateModelFile]', sig.detail);
+        return;
+      }
       const result = ext === 'ifc'
         ? await convertIFCtoGLB(buffer, file.name)
         : await convertToGLB(buffer, ext, file.name);
@@ -60,8 +81,9 @@ const Viewer = () => {
       addModel({ fileName: result.fileName, fileSize: result.fileSize, url });
       toast.success(`"${file.name}" convertido e adicionado!`);
     } catch (err) {
-      console.error(err);
-      toast.error(`Falha ao converter "${file.name}"`);
+      console.error('[upload] conversion failed', err);
+      const msg = err instanceof Error ? err.message : 'erro desconhecido';
+      toast.error(`Falha ao converter "${file.name}": ${msg}`);
     } finally {
       setConverting(false);
     }