diff --git a/apps/edr-freight-api/src/migrations/3080000000000-BackfillDireDawaMilestone.ts b/apps/edr-freight-api/src/migrations/3080000000000-BackfillDireDawaMilestone.ts
index ee44e5971..78c44c0ce 100644
--- a/apps/edr-freight-api/src/migrations/3080000000000-BackfillDireDawaMilestone.ts
+++ b/apps/edr-freight-api/src/migrations/3080000000000-BackfillDireDawaMilestone.ts
@@ -41,9 +41,17 @@ export class BackfillDireDawaMilestone3080000000000 implements MigrationInterfac
                               WHERE m.route_id = rt.id AND m.yard_id = dire
                                 AND m.deleted_at IS NULL)
         LOOP
+          -- Two-phase shift: uq_route_milestones_route_sequence isn't deferrable,
+          -- so a direct +1 UPDATE can collide mid-scan (seq 2 -> 3 while seq 3 still live).
+          -- Route through negative sequence_no first to avoid any interim collision.
+          -- Soft-deleted rows shift too: the constraint counts them, so a dead row
+          -- left at a target sequence would still collide.
           UPDATE freight.route_milestones
-             SET sequence_no = sequence_no + 1
-           WHERE route_id = r.id AND deleted_at IS NULL AND sequence_no >= 2;
+             SET sequence_no = -sequence_no
+           WHERE route_id = r.id AND sequence_no >= 2;
+          UPDATE freight.route_milestones
+             SET sequence_no = -sequence_no + 1
+           WHERE route_id = r.id AND sequence_no < 0;
           INSERT INTO freight.route_milestones (route_id, yard_id, sequence_no)
           VALUES (r.id, dire, 2);
         END LOOP;