changes

fusion_shipping/models/fusion_shipment.py

@@ -267,10 +267,22 @@ class FusionShipment(models.Model):
         }
 
     def _action_open_attachment(self, attachment):
-        """Open an attachment PDF in the browser viewer (new tab)."""
+        """Open an attachment for the operator.
+
+        Delegates to ir.attachment.action_fusion_preview — PDFs render
+        in the preview dialog, anything else (ZPL, etc.) downloads.
+        Helper falls back gracefully when fusion_pdf_preview isn't
+        installed. See CLAUDE.md "PDF Preview" for the contract.
+        """
         self.ensure_one()
         if not attachment:
             return False
+        if hasattr(attachment, 'action_fusion_preview'):
+            return attachment.action_fusion_preview(
+                title=attachment.name or 'Shipping Label',
+                model_name=self._name,
+                record_ids=self.id,
+            )
         return {
             'type': 'ir.actions.act_url',
             'url': '/web/content/%s?download=false' % attachment.id,