diff --git a/backend/internal/repository/api_key_repo.go b/backend/internal/repository/api_key_repo.go
index 859eefd5..667193a6 100644
--- a/backend/internal/repository/api_key_repo.go
+++ b/backend/internal/repository/api_key_repo.go
@@ -3,6 +3,7 @@ package repository
 import (
 	"context"
 	"database/sql"
+	"fmt"
 	"time"
 
 	dbent "github.com/Wei-Shaw/sub2api/ent"
@@ -257,9 +258,12 @@ func (r *apiKeyRepository) Update(ctx context.Context, key *service.APIKey) erro
 }
 
 func (r *apiKeyRepository) Delete(ctx context.Context, id int64) error {
+	// 存在唯一键约束 生成tombstone key 用来释放原key，长度远小于 128，满足 schema 限制
+	tombstoneKey := fmt.Sprintf("__deleted__%d__%d", id, time.Now().UnixNano())
 	// 显式软删除：避免依赖 Hook 行为，确保 deleted_at 一定被设置。
 	affected, err := r.client.APIKey.Update().
 		Where(apikey.IDEQ(id), apikey.DeletedAtIsNil()).
+		SetKey(tombstoneKey).
 		SetDeletedAt(time.Now()).
 		Save(ctx)
 	if err != nil {
diff --git a/backend/internal/repository/api_key_repo_integration_test.go b/backend/internal/repository/api_key_repo_integration_test.go
index a8989ff2..7d5c1826 100644
--- a/backend/internal/repository/api_key_repo_integration_test.go
+++ b/backend/internal/repository/api_key_repo_integration_test.go
@@ -151,6 +151,31 @@ func (s *APIKeyRepoSuite) TestDelete() {
 	s.Require().Error(err, "expected error after delete")
 }
 
+func (s *APIKeyRepoSuite) TestCreate_AfterSoftDelete_AllowsSameKey() {
+	user := s.mustCreateUser("recreate-after-soft-delete@test.com")
+	const reusedKey = "sk-reuse-after-soft-delete"
+
+	first := &service.APIKey{
+		UserID: user.ID,
+		Key:    reusedKey,
+		Name:   "First Key",
+		Status: service.StatusActive,
+	}
+	s.Require().NoError(s.repo.Create(s.ctx, first), "create first key")
+
+	s.Require().NoError(s.repo.Delete(s.ctx, first.ID), "soft delete first key")
+
+	second := &service.APIKey{
+		UserID: user.ID,
+		Key:    reusedKey,
+		Name:   "Second Key",
+		Status: service.StatusActive,
+	}
+	s.Require().NoError(s.repo.Create(s.ctx, second), "create second key with same key")
+	s.Require().NotZero(second.ID)
+	s.Require().NotEqual(first.ID, second.ID, "recreated key should be a new row")
+}
+
 // --- ListByUserID / CountByUserID ---
 
 func (s *APIKeyRepoSuite) TestListByUserID() {