diff --git a/app/repositories/postgres.py b/app/repositories/postgres.py
index b8e691c..4422097 100644
--- a/app/repositories/postgres.py
+++ b/app/repositories/postgres.py
@@ -1190,6 +1190,7 @@ class PostgresPortfolioRepository:
                 raise ValueError("포트폴리오를 찾을 수 없습니다")
             if clear_ledger:
                 cur.execute("DELETE FROM portfolio_ledger WHERE portfolio_id = %s", (portfolio_id,))
+            # Comments are always removed with the portfolio (no FK constraint, handled in application layer)
             cur.execute("DELETE FROM portfolio_comments WHERE portfolio_id = %s", (portfolio_id,))
             cur.execute("DELETE FROM portfolios WHERE portfolio_id = %s", (portfolio_id,))
 
diff --git a/docs/db-schema-spec.md b/docs/db-schema-spec.md
index 532fde5..0f1f9ed 100644
--- a/docs/db-schema-spec.md
+++ b/docs/db-schema-spec.md
@@ -306,6 +306,8 @@ Current baseline intentionally has no DB-level FK constraints.
 
 - Logical relations are managed by application/repository logic.
 - When adding FK constraints in future migrations, update this document and include migration IDs.
+- Cascade behavior implemented in application layer:
+  - Deleting a portfolio also deletes all associated `portfolio_comments` rows (hard delete, no FK constraint).
 
 ## 8. Change Management Rule