diff --git a/apps/api/migrations/phase23_risklevel_add_high.sql b/apps/api/migrations/phase23_risklevel_add_high.sql
new file mode 100644
index 000000000..44fe16da9
--- /dev/null
+++ b/apps/api/migrations/phase23_risklevel_add_high.sql
@@ -0,0 +1,23 @@
+-- =============================================================================
+-- Phase 23: risklevel ENUM 新增 HIGH 值
+-- =============================================================================
+-- 執行日期: 2026-04-01
+-- 執行者: ogt
+-- 背景: Sentry Webhook 送入 risk_level="HIGH" 時 DB 拋 InvalidTextRepresentation
+--       已在 prod/dev 緊急執行，此檔固化為正式 migration record
+-- =============================================================================
+
+-- PostgreSQL ENUM 不支援 IF NOT EXISTS，使用 DO 塊避免重複執行錯誤
+DO $$
+BEGIN
+    IF NOT EXISTS (
+        SELECT 1 FROM pg_enum
+        WHERE enumtypid = 'risklevel'::regtype
+          AND enumlabel = 'high'
+    ) THEN
+        ALTER TYPE risklevel ADD VALUE 'high';
+    END IF;
+END
+$$;
+
+COMMENT ON TYPE risklevel IS 'Risk level enum: low | medium | high | critical. HIGH added Phase 23 (2026-04-01)';