diff --git a/addons/osfstorage/models.py b/addons/osfstorage/models.py
index 46da2662d65..0da2e02ac0e 100644
--- a/addons/osfstorage/models.py
+++ b/addons/osfstorage/models.py
@@ -314,9 +314,6 @@ def serialize(self, include_full=None, version=None):
         version = self.get_version(version)
         earliest_version = self.versions.order_by('created').first()
         ret.update({
-            # Must be the resolved version's own identifier, not versions.count() -- after a
-            # non-latest version is deleted, count() no longer matches any existing identifier,
-            # which breaks osfstorage_download's file_node.get_version(identifier=..., required=True).
             'version': int(version.identifier) if version else 0,
             'md5': version.metadata.get('md5') if version else None,
             'sha256': version.metadata.get('sha256') if version else None,
diff --git a/osf/migrations/0051_alter_fileversion_options.py b/osf/migrations/0051_alter_fileversion_options.py
new file mode 100644
index 00000000000..1fd084d4e51
--- /dev/null
+++ b/osf/migrations/0051_alter_fileversion_options.py
@@ -0,0 +1,17 @@
+# Generated by Django 4.2.26 on 2026-08-04 13:39
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('osf', '0050_downloadevent_user_agent'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='fileversion',
+            options={'ordering': ('-created', '-id')},
+        ),
+    ]
diff --git a/osf/models/files.py b/osf/models/files.py
index 0609f801034..4d353f62506 100644
--- a/osf/models/files.py
+++ b/osf/models/files.py
@@ -883,7 +883,10 @@ def serialize_waterbutler_settings(self, node_id, root_id):
         })
 
     class Meta:
-        ordering = ('-created',)
+        # '-id' is a deterministic tiebreak for versions created within the same instant (e.g. a
+        # version attached directly via add_version() right after another, in the same test/request) --
+        # without it, .first()/.last() on ties is undefined and can flip between identical queries.
+        ordering = ('-created', '-id')
 
 
 class BaseFileVersionsThrough(models.Model):