diff --git a/database/migrations/2026_07_18_060001_add_ring_id_unique_index_to_devices.php b/database/migrations/2026_07_18_060001_add_ring_id_unique_index_to_devices.php
index 3c62149..ad1cd4c 100644
--- a/database/migrations/2026_07_18_060001_add_ring_id_unique_index_to_devices.php
+++ b/database/migrations/2026_07_18_060001_add_ring_id_unique_index_to_devices.php
@@ -7,6 +7,23 @@ return new class extends Migration
 {
     public function up(): void
     {
+        // Reconcile any duplicates the pre-index race may already have created, otherwise the
+        // CREATE UNIQUE INDEX below would abort on existing data. Keep the earliest row per
+        // ring_id; the rest cascade-delete their entities/state (both FKs cascadeOnDelete).
+        // Portable subquery form (works on Postgres in prod and SQLite in tests).
+        DB::statement(<<<'SQL'
+            DELETE FROM devices
+            WHERE config->>'ring_id' IS NOT NULL
+              AND id NOT IN (
+                  SELECT min_id FROM (
+                      SELECT MIN(id) AS min_id
+                      FROM devices
+                      WHERE config->>'ring_id' IS NOT NULL
+                      GROUP BY config->>'ring_id'
+                  ) keep
+              )
+        SQL);
+
         // Concurrent first-sight Ring messages (retained info + motion on bridge startup) must not
         // create two rows for one device. A partial unique index on the JSON ring_id lets the
         // second concurrent insert fail so the ingest job can re-fetch the winner (race-safe).