From ec0fe62df572d68033b3e2daf27244fb99316c46 Mon Sep 17 00:00:00 2001
From: Jeremy Stretch <jstretch@netboxlabs.com>
Date: Wed, 4 Mar 2026 10:44:37 -0500
Subject: [PATCH] Include the current ETag in the 412 response

---
 netbox/netbox/api/viewsets/__init__.py | 8 +++++++-
 netbox/utilities/exceptions.py         | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/netbox/netbox/api/viewsets/__init__.py b/netbox/netbox/api/viewsets/__init__.py
index 42ae1caf9..f257e3966 100644
--- a/netbox/netbox/api/viewsets/__init__.py
+++ b/netbox/netbox/api/viewsets/__init__.py
@@ -61,7 +61,13 @@ class ETagMixin:
         if provided := self._get_if_match(request):
             current_etag = self._get_etag(instance)
             if current_etag and current_etag not in provided:
-                raise PreconditionFailed()
+                raise PreconditionFailed(etag=current_etag)
+
+    def handle_exception(self, exc):
+        response = super().handle_exception(exc)
+        if isinstance(exc, PreconditionFailed) and exc.etag:
+            response['ETag'] = exc.etag
+        return response
 
     def retrieve(self, request, *args, **kwargs):
         instance = self.get_object()
diff --git a/netbox/utilities/exceptions.py b/netbox/utilities/exceptions.py
index 8c95f844b..60ac7d26a 100644
--- a/netbox/utilities/exceptions.py
+++ b/netbox/utilities/exceptions.py
@@ -44,11 +44,16 @@ class PermissionsViolation(Exception):
 class PreconditionFailed(APIException):
     """
     Raised when an If-Match precondition is not satisfied (HTTP 412).
+    Optionally carries the current ETag so it can be included in the response.
     """
     status_code = status.HTTP_412_PRECONDITION_FAILED
     default_detail = 'Precondition failed.'
     default_code = 'precondition_failed'
 
+    def __init__(self, detail=None, code=None, etag=None):
+        super().__init__(detail=detail, code=code)
+        self.etag = etag
+
 
 class RQWorkerNotRunningException(APIException):
     """