diff --git a/migrations/2025-12-17-230100_unique_favorites/down.sql b/migrations/2025-12-17-230100_unique_favorites/down.sql
new file mode 100644
index 0000000..b42819b
--- /dev/null
+++ b/migrations/2025-12-17-230100_unique_favorites/down.sql
@@ -0,0 +1,3 @@
+-- Rollback unique constraint on favorites
+
+DROP INDEX IF EXISTS idx_favorites_unique;
diff --git a/migrations/2025-12-17-230100_unique_favorites/up.sql b/migrations/2025-12-17-230100_unique_favorites/up.sql
new file mode 100644
index 0000000..b123617
--- /dev/null
+++ b/migrations/2025-12-17-230100_unique_favorites/up.sql
@@ -0,0 +1,12 @@
+-- Add unique constraint to prevent duplicate favorites per user
+
+-- First, remove any existing duplicates (keep the oldest one)
+DELETE FROM favorites
+WHERE rowid NOT IN (
+    SELECT MIN(rowid)
+    FROM favorites
+    GROUP BY userid, path
+);
+
+-- Add unique index to enforce constraint
+CREATE UNIQUE INDEX idx_favorites_unique ON favorites(userid, path);