fix(tasks): 任务取消 - 禁止取消已开始的生成任务

backend/internal/service/service.go

@@ -691,16 +691,18 @@ func (s *Service) RetryTask(userID string, id string) (*model.Task, error) {
 	return taskForOutput(*task), nil
 }
 
-func (s *Service) CancelTask(ctx context.Context, userID string, id string) (*model.Task, error) {
+func (s *Service) CancelTask(_ context.Context, userID string, id string) (*model.Task, error) {
 	task, err := s.repo.TaskForUser(userID, id)
 	if err != nil {
 		return nil, err
 	}
+	if task.Status == model.TaskStatusRunning {
+		return nil, errors.New("任务已开始生成，无法取消")
+	}
 	if task.Status == model.TaskStatusSucceeded {
 		return nil, errors.New("completed task cannot be cancelled")
 	}
 	now := time.Now()
-	cancelledRunningTask := false
 	if task.Status == model.TaskStatusQueued {
 		cancelled, err := s.repo.CancelTaskIfStatus(userID, task.ID, model.TaskStatusQueued, now)
 		if err != nil {
@@ -721,31 +723,9 @@ func (s *Service) CancelTask(ctx context.Context, userID string, id string) (*mo
 			}
 		}
 	}
+	// 排队任务可能在条件更新前被 worker 抢占，重新读取后必须再次阻止取消。
 	if task.Status == model.TaskStatusRunning {
-		cancelled, err := s.repo.CancelTaskIfStatus(userID, task.ID, model.TaskStatusRunning, now)
-		if err != nil {
-			return nil, err
-		}
-		if !cancelled {
-			latest, latestErr := s.repo.TaskForUser(userID, id)
-			if latestErr != nil {
-				return nil, latestErr
-			}
-			if latest.Status == model.TaskStatusSucceeded {
-				return nil, errors.New("completed task cannot be cancelled")
-			}
-			task = latest
-		} else {
-			cancelledRunningTask = true
-			s.cancelActiveTask(task.ID)
-			if err := s.MarkBillingUncertain(task.BillingOrderID, "运行中的上游请求被用户取消，费用状态待核对"); err != nil {
-				return nil, err
-			}
-			task, err = s.repo.TaskForUser(userID, id)
-			if err != nil {
-				return nil, err
-			}
-		}
+		return nil, errors.New("任务已开始生成，无法取消")
 	}
 	if task.Status != model.TaskStatusCancelled {
 		return nil, errors.New("task cannot be cancelled in its current state")
@@ -753,15 +733,6 @@ func (s *Service) CancelTask(ctx context.Context, userID string, id string) (*mo
 	if task.SessionID != "" {
 		_ = s.markSessionFailed(*task, "会话任务已取消。")
 	}
-	if cancelledRunningTask {
-		if err := s.requestProviderCancellation(ctx, task); err != nil {
-			return nil, err
-		}
-		task, err = s.repo.TaskForUser(userID, id)
-		if err != nil {
-			return nil, err
-		}
-	}
 	if err := s.finalizeTaskTextReplay(task.ID, model.TaskStatusCancelled); err != nil {
 		_ = s.log(userID, task.ID, "error", "文本回放草稿归并失败", err.Error())
 	}

backend/internal/service/task_cancellation_test.go

@@ -0,0 +1,47 @@
+package service
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"infinite-canvas/backend/internal/model"
+	"infinite-canvas/backend/internal/repository"
+
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+)
+
+func TestCancelTaskRejectsRunningTask(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open("file:"+newID()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := db.AutoMigrate(&model.Task{}); err != nil {
+		t.Fatal(err)
+	}
+	startedAt := time.Now()
+	task := model.Task{
+		ID:        "running-task",
+		UserID:    "user-1",
+		Status:    model.TaskStatusRunning,
+		Stage:     "调用生成模型",
+		StartedAt: &startedAt,
+	}
+	if err := db.Create(&task).Error; err != nil {
+		t.Fatal(err)
+	}
+
+	svc := &Service{repo: repository.New(db)}
+	if _, err := svc.CancelTask(context.Background(), task.UserID, task.ID); err == nil || err.Error() != "任务已开始生成，无法取消" {
+		t.Fatalf("CancelTask() error = %v", err)
+	}
+
+	stored, err := svc.repo.TaskForUser(task.UserID, task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if stored.Status != model.TaskStatusRunning || stored.CompletedAt != nil {
+		t.Fatalf("running task changed after cancellation attempt: status=%s completedAt=%v", stored.Status, stored.CompletedAt)
+	}
+}