fix(channels): account for group_override in the auto-sync range-conflict check

The range-conflict warning classified each channel in the configured range as either this config's own auto-sync output or a real conflict, comparing each occupant against the source group. When a group sets a group_override, auto-sync creates its channels in the override target group, so the config's own channels failed that comparison and were misclassified as a conflict.

- Add effectiveSyncGroupId to resolve the group the sync's channels actually land in (the group_override target when set, otherwise the source group).
- Compare occupants against that effective target, so the config's own output is recognized while genuine conflicts (manual channels, channels from another account, channels in a different group, user-pinned numbers) still warn.
- Add Vitest coverage for the helper, the override case, and an over-suppression guard, plus a backend test asserting the numbers-in-range endpoint reports the override target group.

apps/m3u/tests/test_sync_correctness.py

@@ -644,6 +644,34 @@ class NumbersInRangeLookupTests(TestCase):
         )
         self.assertFalse(occupant["has_channel_number_override"])
 
+    def test_group_override_channel_reports_target_group(self):
+        # When auto-sync routes channels into a different group via
+        # group_override, the occupant's channel_group_id is the override
+        # target, not the source group being configured. The frontend relies
+        # on this to recognize override-routed channels as the config's own
+        # output (effectiveSyncGroupId), so the warning does not flag them.
+        account = _make_account()
+        source = _make_group(name="SourceGrp")
+        target = _make_group(name="TargetGrp")
+        Channel.objects.create(
+            name="Routed",
+            channel_number=3210,
+            channel_group=target,
+            auto_created=True,
+            auto_created_by=account,
+        )
+        client = self._client()
+
+        response = client.get(
+            "/api/channels/channels/numbers-in-range/?start=3210&end=3210"
+        )
+
+        occupant = response.data["occupants"][0]
+        self.assertEqual(occupant["channel_group_id"], target.id)
+        self.assertNotEqual(occupant["channel_group_id"], source.id)
+        self.assertTrue(occupant["auto_created"])
+        self.assertEqual(occupant["auto_created_by_account_id"], account.id)
+
     def test_manual_channel_exposed_with_auto_created_false(self):
         # Manual channels are always a real collision worth surfacing.
         # The response must flag them with auto_created=False and a null

frontend/src/components/forms/LiveGroupFilter.jsx

@@ -34,6 +34,7 @@ import {
   getRegexOptions,
   getStreamsRegexPreview,
   isExpectedOccupantForGroup,
+  effectiveSyncGroupId,
   isGroupVisible,
   rangeFor,
 } from '../../utils/forms/LiveGroupFilterUtils.js';
@@ -131,7 +132,12 @@ const LiveGroupFilter = ({
   // (in-memory range overlap with sibling groups) sources so the sweep
   // can refresh form-overlap synchronously without firing HTTP for
   // groups that did not change.
-  const scheduleConflictScan = (groupId, rawStart, rawEnd) => {
+  const scheduleConflictScan = (
+    groupId,
+    rawStart,
+    rawEnd,
+    expectedGroupId = groupId
+  ) => {
     if (conflictTimersRef.current[groupId]) {
       clearTimeout(conflictTimersRef.current[groupId]);
     }
@@ -156,7 +162,7 @@ const LiveGroupFilter = ({
           ? result.occupants
           : [];
         const unexpected = occupants.filter(
-          (o) => !isExpectedOccupantForGroup(o, groupId, playlist)
+          (o) => !isExpectedOccupantForGroup(o, expectedGroupId, playlist)
         );
         setConflictSource(groupId, 'occupant', unexpected.length > 0);
       } catch (e) {
@@ -221,7 +227,8 @@ const LiveGroupFilter = ({
         scheduleConflictScan(
           g.channel_group,
           range.startRaw,
-          g.auto_sync_channel_end
+          g.auto_sync_channel_end,
+          effectiveSyncGroupId(g)
         );
       }
     }

frontend/src/utils/forms/LiveGroupFilterUtils.js

@@ -57,6 +57,18 @@ export const isExpectedOccupantForGroup = (
   );
 };
 
+// The group the sync's own channels actually land in. A group_override
+// routes auto-created channels into a different ChannelGroup, so the
+// conflict check must recognize occupants of that target group as this
+// config's own output rather than flagging them against the source group.
+export const effectiveSyncGroupId = (group) => {
+  const override = group?.custom_properties?.group_override;
+  if (override !== undefined && override !== null && override !== '') {
+    return Number(override);
+  }
+  return group?.channel_group;
+};
+
 export const rangeFor = (g) => {
   if (!g.enabled || !g.auto_channel_sync) return null;
   const mode = g.custom_properties?.channel_numbering_mode || 'fixed';

frontend/src/utils/forms/__tests__/LiveGroupFilterUtils.test.js

@@ -4,6 +4,7 @@ import {
   getChannelsInRange,
   getStreamsRegexPreview,
   isExpectedOccupantForGroup,
+  effectiveSyncGroupId,
   rangeFor,
   abortTimers,
   getRegexOptions,
@@ -227,6 +228,116 @@ describe('LiveGroupFilterUtils', () => {
     });
   });
 
+  // ── effectiveSyncGroupId ───────────────────────────────────────────────────
+  describe('effectiveSyncGroupId', () => {
+    it('returns the source channel_group when there is no override', () => {
+      expect(effectiveSyncGroupId(makeGroup({ channel_group: 7 }))).toBe(7);
+    });
+
+    it('returns the group_override target when set', () => {
+      const group = makeGroup({
+        channel_group: 7,
+        custom_properties: { group_override: 9 },
+      });
+      expect(effectiveSyncGroupId(group)).toBe(9);
+    });
+
+    it('coerces a string-stored group_override to a number', () => {
+      const group = makeGroup({
+        channel_group: 7,
+        custom_properties: { group_override: '9' },
+      });
+      expect(effectiveSyncGroupId(group)).toBe(9);
+    });
+
+    it('falls back to the source group when group_override is blank', () => {
+      const group = makeGroup({
+        channel_group: 7,
+        custom_properties: { group_override: '' },
+      });
+      expect(effectiveSyncGroupId(group)).toBe(7);
+    });
+
+    // Regression guard for the group-override range-conflict false positive:
+    // the auto-sync's own channels land in the override target group, so
+    // comparing against the source group (pre-fix) flags them as a conflict,
+    // while comparing against the effective target recognizes them as this
+    // config's own output.
+    it("makes group-override occupants count as this group's own", () => {
+      const group = makeGroup({
+        channel_group: 7,
+        custom_properties: { group_override: 9 },
+      });
+      const occupant = makeOccupant({ channel_group_id: 9 });
+      // Pre-fix comparison (source group) treats own channels as a conflict.
+      expect(
+        isExpectedOccupantForGroup(
+          occupant,
+          group.channel_group,
+          makePlaylist()
+        )
+      ).toBe(false);
+      // Comparing against the effective target recognizes them as expected.
+      expect(
+        isExpectedOccupantForGroup(
+          occupant,
+          effectiveSyncGroupId(group),
+          makePlaylist()
+        )
+      ).toBe(true);
+    });
+
+    // Guards against over-suppression: resolving the effective target group
+    // must still surface genuine collisions in an override config's range.
+    // Only the config's own output (auto-created, this account, in the
+    // target group, unpinned) is excluded.
+    it('still flags genuine collisions in a group-override config', () => {
+      const group = makeGroup({
+        channel_group: 7,
+        custom_properties: { group_override: 9 },
+      });
+      const target = effectiveSyncGroupId(group);
+      // Manual channel sitting in the range.
+      expect(
+        isExpectedOccupantForGroup(
+          makeOccupant({ channel_group_id: 9, auto_created: false }),
+          target,
+          makePlaylist()
+        )
+      ).toBe(false);
+      // Auto-created by a different account.
+      expect(
+        isExpectedOccupantForGroup(
+          makeOccupant({
+            channel_group_id: 9,
+            auto_created_by_account_id: 999,
+          }),
+          target,
+          makePlaylist()
+        )
+      ).toBe(false);
+      // A channel in a different group than the override target.
+      expect(
+        isExpectedOccupantForGroup(
+          makeOccupant({ channel_group_id: 123 }),
+          target,
+          makePlaylist()
+        )
+      ).toBe(false);
+      // A user-pinned channel number.
+      expect(
+        isExpectedOccupantForGroup(
+          makeOccupant({
+            channel_group_id: 9,
+            has_channel_number_override: true,
+          }),
+          target,
+          makePlaylist()
+        )
+      ).toBe(false);
+    });
+  });
+
   // ── rangeFor ──────────────────────────────────────────────────────────────
   describe('rangeFor', () => {
     it('returns null when group is disabled', () => {