Sorting: stable tiebreak so group frames don't reshuffle mid-M+

Features/Sort.lua

@@ -194,7 +194,13 @@ function Sort:CompareUnits(unitA, unitB, db)
             return nameA < nameB
         end
     end
-
+
+    -- Deterministic final tiebreak: equal-key units need a stable order, or the
+    -- unstable Lua table.sort reshuffles them on each re-sort (group-frame shuffle
+    -- during M+ pulls). Mirrors Headers.lua SortMembers.
+    local tieA = UnitName(unitA) or ""
+    local tieB = UnitName(unitB) or ""
+    if tieA ~= tieB then return tieA < tieB end
     return false
 end
 
@@ -267,7 +273,12 @@ function Sort:CompareTestData(dataA, dataB, db)
             return nameA < nameB
         end
     end
-
+
+    -- Deterministic final tiebreak (see CompareUnits) so test-mode sorting is
+    -- stable across re-sorts too.
+    local tieA = dataA.name or ""
+    local tieB = dataB.name or ""
+    if tieA ~= tieB then return tieA < tieB end
     return false
 end
 

Frames/Headers.lua

@@ -4878,9 +4878,19 @@ function DF:BuildSortedNameList(members, db, selfPosition, includesPlayer)
                 return a.name < b.name
             end
         end
+        -- Deterministic final tiebreak. Without one, members with equal sort keys
+        -- (same role, Alphabetical off) have no defined order, and Lua's table.sort
+        -- is NOT stable — so a roster-driven re-sort mid-encounter reshuffles
+        -- same-role players, making the group frames rearrange during M+ pulls.
+        -- Break ties by name (invariant for the session, and realm-qualified in the
+        -- nameList so cross-realm names don't collide) so every re-sort of the same
+        -- roster produces an identical order and the secure header never reorders.
+        if a.name ~= b.name then
+            return a.name < b.name
+        end
         return false
     end
-    
+
     -- Sort non-player members
     table.sort(sortedMembers, SortMembers)