From f4425fb717cddd441d1696ea021b22931d5590c4 Mon Sep 17 00:00:00 2001
From: Ryan Carroll <ryan.carroll@graylog.com>
Date: Thu, 2 Apr 2026 08:53:27 -0500
Subject: [PATCH 1/2] Handle case where event definition is missing

---
 .../events/events/hooks/useEventDefinition.tsx |  7 +++----
 .../events/EventsList/EventDetails.test.tsx    |  3 ++-
 .../events/filters/EventDefinitionName.tsx     | 18 +++++++-----------
 3 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/graylog2-web-interface/src/components/events/events/hooks/useEventDefinition.tsx b/graylog2-web-interface/src/components/events/events/hooks/useEventDefinition.tsx
index 65ac4fe8a373..6ec64381133e 100644
--- a/graylog2-web-interface/src/components/events/events/hooks/useEventDefinition.tsx
+++ b/graylog2-web-interface/src/components/events/events/hooks/useEventDefinition.tsx
@@ -19,21 +19,20 @@ import { keepPreviousData, useQuery } from '@tanstack/react-query';
 import fetch from 'logic/rest/FetchProvider';
 import { qualifyUrl } from 'util/URLUtils';
 import type { EventDefinition } from 'components/event-definitions/event-definitions-types';
-import { defaultOnError } from 'util/conditional/onError';
 
 export const fetchEventDefinitionDetails = async (eventDefinitionId: string): Promise<EventDefinition> =>
   fetch('GET', qualifyUrl(`/events/definitions/${eventDefinitionId}`));
 
 const useEventDefinition = (eventDefId: string, enabled = true) => {
-  const { data, isFetching, isInitialLoading } = useQuery({
+  const { data, isFetching, isInitialLoading, isError } = useQuery({
     queryKey: ['get-event-definition-details', eventDefId],
-    queryFn: () => defaultOnError(fetchEventDefinitionDetails(eventDefId), 'Loading archives failed with status'),
+    queryFn: () => fetchEventDefinitionDetails(eventDefId),
     retry: 0,
     placeholderData: keepPreviousData,
     enabled: !!eventDefId && enabled,
   });
 
-  return { data, isFetching, isInitialLoading };
+  return { data, isFetching, isInitialLoading, isError };
 };
 
 export default useEventDefinition;
diff --git a/graylog2-web-interface/src/views/components/widgets/events/EventsList/EventDetails.test.tsx b/graylog2-web-interface/src/views/components/widgets/events/EventsList/EventDetails.test.tsx
index 1568b9d0aa45..e597d4672cc5 100644
--- a/graylog2-web-interface/src/views/components/widgets/events/EventsList/EventDetails.test.tsx
+++ b/graylog2-web-interface/src/views/components/widgets/events/EventsList/EventDetails.test.tsx
@@ -52,7 +52,7 @@ describe('EventDetails', () => {
     );
 
     asMock(useCurrentUser).mockReturnValue(adminUser);
-    asMock(useEventDefinition).mockReturnValue({ data: undefined, isFetching: false, isInitialLoading: false });
+    asMock(useEventDefinition).mockReturnValue({ data: undefined, isFetching: false, isInitialLoading: false, isError: false });
 
     asMock(useEventById).mockImplementation(() => ({
       data: mockEventData.event,
@@ -86,6 +86,7 @@ describe('EventDetails', () => {
       data: mockEventDefinitionTwoAggregations,
       isFetching: false,
       isInitialLoading: false,
+      isError: false,
     });
 
     renderEventDetails();
diff --git a/graylog2-web-interface/src/views/components/widgets/events/filters/EventDefinitionName.tsx b/graylog2-web-interface/src/views/components/widgets/events/filters/EventDefinitionName.tsx
index 72f00ce9f7aa..4e48d168e040 100644
--- a/graylog2-web-interface/src/views/components/widgets/events/filters/EventDefinitionName.tsx
+++ b/graylog2-web-interface/src/views/components/widgets/events/filters/EventDefinitionName.tsx
@@ -30,26 +30,22 @@ type Props = {
 const EventDefinitionName = ({ eventDefinitionId, displayAsLink = true }: Props) => {
   const currentUser = useCurrentUser();
   const canViewDefinition = isPermitted(currentUser.permissions, `eventdefinitions:read:${eventDefinitionId}`);
-  const { data: eventDefinition, isFetching } = useEventDefinition(eventDefinitionId, canViewDefinition);
+  const { data: eventDefinition, isFetching, isError } = useEventDefinition(eventDefinitionId, canViewDefinition);
   const title = eventDefinition?.title ?? eventDefinitionId;
 
   if (isFetching) {
     return <Spinner />;
   }
 
-  if (!displayAsLink || !canViewDefinition) {
+  if (!displayAsLink || !canViewDefinition || !eventDefinition || isError) {
     return <>{title}</>;
   }
 
-  if (eventDefinition) {
-    return (
-      <Link to={Routes.ALERTS.DEFINITIONS.show(eventDefinition.id)} target="_blank">
-        {title}
-      </Link>
-    );
-  }
-
-  return null;
+  return (
+    <Link to={Routes.ALERTS.DEFINITIONS.show(eventDefinition.id)} target="_blank">
+      {title}
+    </Link>
+  );
 };
 
 export default EventDefinitionName;

From 1d55492d1a2daab26920ece7240d0f6ae8791ce9 Mon Sep 17 00:00:00 2001
From: Ryan Carroll <ryan.carroll@graylog.com>
Date: Thu, 2 Apr 2026 08:57:41 -0500
Subject: [PATCH 2/2] add cl entry

---
 changelog/unreleased/pr-25548.toml | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 changelog/unreleased/pr-25548.toml

diff --git a/changelog/unreleased/pr-25548.toml b/changelog/unreleased/pr-25548.toml
new file mode 100644
index 000000000000..88970122bc3e
--- /dev/null
+++ b/changelog/unreleased/pr-25548.toml
@@ -0,0 +1,5 @@
+type = "fixed"
+message = "Show event definition ID instead of throwing errors in the Events Overview widget when the event definition has been deleted"
+
+pulls = ["25548"]
+issues = ["graylog-plugin-enterprise#13756"]