feat(issues): Fallback to case insensitive short id lookup

src/sentry/models/group.py

@@ -369,6 +369,41 @@ def by_qualified_short_id_bulk(
             ).filter(short_id_lookup, project__organization=organization_id)
         )
         group_lookup: set[int] = {group.short_id for group in groups}
+
+        # If any requested short_ids are missing after the exact slug match,
+        # fallback to a case-insensitive slug lookup to handle legacy/mixed-case slugs.
+        missing_short_ids = [sid.short_id for sid in short_ids if sid.short_id not in group_lookup]
+        if missing_short_ids:
+            # Build a lookup only for the missing short_ids per slug
+            missing_by_slug = defaultdict(list)
+            for sid in short_ids:
+                if sid.short_id in missing_short_ids:
+                    missing_by_slug[sid.project_slug].append(sid.short_id)
+
+            ci_short_id_lookup = reduce(
+                or_,
+                [
+                    Q(project__slug__iexact=slug, short_id__in=sids)
+                    for slug, sids in missing_by_slug.items()
+                ],
+            )
+
+            fallback_groups = list(
+                self.exclude(
+                    status__in=[
+                        GroupStatus.PENDING_DELETION,
+                        GroupStatus.DELETION_IN_PROGRESS,
+                        GroupStatus.PENDING_MERGE,
+                    ]
+                ).filter(ci_short_id_lookup, project__organization=organization_id)
+            )
+
+            if fallback_groups:
+                # Merge unique groups from fallback
+                existing_ids = {g.id for g in groups}
+                groups.extend(g for g in fallback_groups if g.id not in existing_ids)
+                group_lookup = {group.short_id for group in groups}
+
         for short_id in short_ids:
             if short_id.short_id not in group_lookup:
                 raise Group.DoesNotExist()

tests/sentry/models/test_group.py

@@ -15,6 +15,7 @@
 from sentry.models.groupredirect import GroupRedirect
 from sentry.models.grouprelease import GroupRelease
 from sentry.models.groupsnooze import GroupSnooze
+from sentry.models.project import Project
 from sentry.models.release import Release, _get_cache_key
 from sentry.replays.testutils import mock_replay
 from sentry.testutils.cases import ReplaysSnubaTestCase, SnubaTestCase, TestCase
@@ -169,6 +170,21 @@ def test_qualified_share_id_bulk(self) -> None:
                 group.organization.id, [group_short_id, group_2_short_id]
             )
 
+    def test_by_qualified_short_id_bulk_case_insensitive_project_slug(self) -> None:
+        project = self.create_project(slug="mixedcaseslug")
+        group = self.create_group(project=project, short_id=project.next_short_id())
+
+        Project.objects.filter(id=project.id).update(slug="MixedCaseSlug")
+        assert Project.objects.get(id=project.id).slug == "MixedCaseSlug"
+
+        # Re-fetch to ensure updated relation is used when computing qualified_short_id
+        group = Group.objects.get(id=group.id)
+        short_id = group.qualified_short_id
+
+        # Should resolve via case-insensitive slug fallback
+        resolved = Group.objects.by_qualified_short_id_bulk(group.organization.id, [short_id])
+        assert resolved == [group]
+
     def test_first_last_release(self) -> None:
         project = self.create_project()
         release = Release.objects.create(version="a", organization_id=project.organization_id)