diff --git a/internal/apps/oauth/logics.go b/internal/apps/oauth/logics.go
index e527ed0..b2e6030 100644
--- a/internal/apps/oauth/logics.go
+++ b/internal/apps/oauth/logics.go
@@ -111,14 +111,13 @@ func doOAuth(ctx context.Context, code string, nonce string) (*model.User, error
 	err = db.DB(ctx).Transaction(func(tx *gorm.DB) error {
 		var holder model.User
 		if conflictErr := tx.Where("username = ? AND id != ?", userInfo.Username, userInfo.GetID()).First(&holder).Error; conflictErr == nil {
-			// 存在冲突 -> 将占用者改名并注销
-			newParams := map[string]interface{}{
-				"username":  fmt.Sprintf("%s已注销: %s", holder.Username, uuid.NewString()),
-				"is_active": false,
-			}
-			if updateErr := tx.Model(&holder).Updates(newParams).Error; updateErr != nil {
+			// 用户名来自 OAuth 且可能被改名复用；冲突时只释放旧用户名，不禁用原账号。
+			newUsername := fmt.Sprintf("__released_username__:%d:%s", holder.ID, uuid.NewString())
+			if updateErr := tx.Model(&holder).Update("username", newUsername).Error; updateErr != nil {
 				return updateErr
 			}
+		} else if !errors.Is(conflictErr, gorm.ErrRecordNotFound) {
+			return conflictErr
 		}
 
 		// 根据 ID 处理当前用户的 更新 或 创建
diff --git a/internal/model/users.go b/internal/model/users.go
index 1f6470c..bec0daa 100644
--- a/internal/model/users.go
+++ b/internal/model/users.go
@@ -92,7 +92,7 @@ type LeaderboardUser struct {
 
 type User struct {
 	ID               uint64          `json:"id" gorm:"primaryKey;index:idx_users_active_bal_id,priority:3"`
-	Username         string          `json:"username" gorm:"size:64;uniqueIndex"`
+	Username         string          `json:"username" gorm:"size:255;uniqueIndex"`
 	Nickname         string          `json:"nickname" gorm:"size:255"`
 	AvatarUrl        string          `json:"avatar_url" gorm:"size:255"`
 	TrustLevel       TrustLevel      `json:"trust_level" gorm:"index"`