diff --git a/src/storage/mod.rs b/src/storage/mod.rs
index 1326709..28c37a3 100644
--- a/src/storage/mod.rs
+++ b/src/storage/mod.rs
@@ -1729,6 +1729,26 @@ fn ensure_scheduler_schema(conn: &Connection) -> Result<(), StorageError> {
 }
 
 fn ensure_memory_scope_key_migration(conn: &Connection) -> Result<(), StorageError> {
+    // 步骤1：去重。多条记录 scope_key 不同，改为 "default" 后会违反唯一约束。
+    // 对每个 (scope_kind, namespace, memory_key) 组合保留 updated_at 最新的一条。
+    conn.execute(
+        "
+        DELETE FROM memories
+        WHERE rowid NOT IN (
+            SELECT rowid FROM (
+                SELECT rowid, ROW_NUMBER() OVER (
+                    PARTITION BY scope_kind, namespace, memory_key
+                    ORDER BY updated_at DESC
+                ) AS rn
+                FROM memories
+            )
+            WHERE rn = 1
+        )
+        ",
+        [],
+    )?;
+
+    // 步骤2：统一 scope_key
     conn.execute(
         "UPDATE memories SET scope_key = 'default' WHERE scope_key != 'default'",
         [],