fix(queue-limit): P1修复 - 阈值抽常量 + 边界统一 + 入队后兜底校验

- 阈值统一管理：USER_PENDING_LIMIT/GLOBAL_PENDING_LIMIT 抽到 task_enqueue.py 常量，所有入口引用
- 边界判断统一：预检查用 >=（任务创建前），入队检查用 >（包含当前任务），语义一致
- 并发竞态兜底：发送Celery后再查一次DB计数，超限则回滚任务为failed
- 新增 12 个单元测试（入队后兜底5个 + 边界验证7个）

apps/api/app/api/routes/edit_plans.py

@@ -24,6 +24,7 @@ from typing import Any, List, Optional
 
 from app.auth import AuthenticatedUser, get_current_user
 from app.core.celery_app import celery_app
+from app.core.task_enqueue import GLOBAL_PENDING_LIMIT, USER_PENDING_LIMIT
 from app.dependencies import get_asset_library_repository, get_asset_repository, get_db_session, get_project_repository
 from app.schemas.generation_task import GenerationTaskResponse
 from app.services import EditPlanService, PlanGeneratorService
@@ -644,6 +645,31 @@ def generate_plan(
 
         # 创建 GenerationTask
         gen_task_repo = SQLAlchemyGenerationTaskRepository(db)
+
+        # 队列限流预检查（repository 不支持计数时跳过）
+        user_id = current_user.user.id
+        try:
+            has_count = hasattr(gen_task_repo, "count_pending_by_user") and hasattr(
+                gen_task_repo, "count_pending_total"
+            )
+            if has_count:
+                user_pending = gen_task_repo.count_pending_by_user(user_id)
+                global_pending = gen_task_repo.count_pending_total()
+                if user_pending >= USER_PENDING_LIMIT:
+                    raise HTTPException(
+                        status_code=429,
+                        detail=f"您的待处理任务过多（当前 {user_pending}/{USER_PENDING_LIMIT}），请等待完成后再提交",
+                    )
+                if global_pending >= GLOBAL_PENDING_LIMIT:
+                    raise HTTPException(
+                        status_code=503,
+                        detail="系统繁忙，请稍后再试",
+                    )
+        except HTTPException:
+            raise
+        except Exception as e:
+            logger.warning("[队列限流] 剪辑计划限流检查失败，跳过: %s", e)
+
         gen_task_use_case = CreateGenerationTaskUseCase(gen_task_repo)
         plan = svc.get_plan_or_raise(plan_id)
         gen_task = gen_task_use_case.execute(

apps/api/app/api/routes/generation_tasks.py

@@ -5,7 +5,14 @@ from typing import Any
 
 from app.auth import AuthenticatedUser, get_current_user
 from app.core.storage import OSSStorageService, get_storage_service
-from app.core.task_enqueue import safe_enqueue_generation_task
+from app.core.task_enqueue import (
+    GLOBAL_PENDING_LIMIT,
+    USER_PENDING_LIMIT,
+    GlobalQueueFull,
+    UserPendingLimitExceeded,
+    check_queue_limits,
+    safe_enqueue_generation_task,
+)
 from app.dependencies import (
     get_asset_library_repository,
     get_asset_repository,
@@ -228,9 +235,31 @@ def create_generation_task(
     count = request.count
     created_tasks = []
     failed_tasks = []
+    user_id = authenticated_user.user.id
     # 同批次任务共享 batch_id，用于视频查重时批次内比对
     batch_id = uuid.uuid4().hex if count > 1 else ""
 
+    # 预检查：批量提交前先看会不会超限，避免建一半才拒
+    try:
+        user_pending = generation_task_repository.count_pending_by_user(user_id)
+        global_pending = generation_task_repository.count_pending_total()
+        if user_pending + count > USER_PENDING_LIMIT:
+            raise UserPendingLimitExceeded(
+                user_id=user_id, pending_count=user_pending + count, limit=USER_PENDING_LIMIT
+            )
+        if global_pending + count > GLOBAL_PENDING_LIMIT:
+            raise GlobalQueueFull(pending_count=global_pending + count, limit=GLOBAL_PENDING_LIMIT)
+    except UserPendingLimitExceeded as e:
+        raise HTTPException(
+            status_code=429,
+            detail=f"您的待处理任务过多（当前 {e.pending_count - count}/{e.limit}，本次提交 {count} 个），请等待完成后再提交",
+        ) from e
+    except GlobalQueueFull as e:
+        raise HTTPException(
+            status_code=503,
+            detail="系统繁忙，请稍后再试",
+        ) from e
+
     try:
         for _ in range(count):
             task = use_case.execute(
@@ -243,16 +272,42 @@ def create_generation_task(
                     asset_ids=resolved_asset_ids,
                     title_ids=request.title_ids,
                     voice_ids=request.voice_ids,
-                    created_by_user_id=authenticated_user.user.id,
+                    created_by_user_id=user_id,
                     source_edit_plan_id=request.source_edit_plan_id,
                     asset_select_mode=request.asset_select_mode,
                     batch_id=batch_id,
                 )
             )
-            if safe_enqueue_generation_task(task, generation_task_repository, log_prefix="[生成任务]", log_task_status=True):
-                created_tasks.append(task)
-            else:
+            try:
+                if safe_enqueue_generation_task(
+                    task,
+                    generation_task_repository,
+                    user_id=user_id,
+                    log_prefix="[生成任务]",
+                    log_task_status=True,
+                ):
+                    created_tasks.append(task)
+                else:
+                    failed_tasks.append(task)
+            except UserPendingLimitExceeded:
+                # 兜底：如果预检查后又并发提交了，在这里也拦住
                 failed_tasks.append(task)
+                if not created_tasks:
+                    raise HTTPException(
+                        status_code=429,
+                        detail="您的待处理任务过多，请等待完成后再提交",
+                    )
+                break
+            except GlobalQueueFull:
+                failed_tasks.append(task)
+                if not created_tasks:
+                    raise HTTPException(
+                        status_code=503,
+                        detail="系统繁忙，请稍后再试",
+                    )
+                break
+    except HTTPException:
+        raise
     except Exception as e:
         logger.error("[生成任务] 创建失败: %s", e, exc_info=True)
         raise HTTPException(status_code=500, detail="创建生成任务失败，请稍后重试或查看任务日志")
@@ -327,6 +382,21 @@ def retry_generation_task(
     if status_val != "failed":
         raise HTTPException(status_code=409, detail="Only failed tasks can be retried")
 
+    user_id = authenticated_user.user.id
+    # 预检查：创建前判断，>= 上限就拒绝
+    user_pending = generation_task_repository.count_pending_by_user(user_id)
+    global_pending = generation_task_repository.count_pending_total()
+    if user_pending >= USER_PENDING_LIMIT:
+        raise HTTPException(
+            status_code=429,
+            detail=f"您的待处理任务过多（当前 {user_pending}/{USER_PENDING_LIMIT}），请等待完成后再提交",
+        )
+    if global_pending >= GLOBAL_PENDING_LIMIT:
+        raise HTTPException(
+            status_code=503,
+            detail="系统繁忙，请稍后再试",
+        )
+
     use_case = CreateGenerationTaskUseCase(generation_task_repository)
     retried = use_case.execute(
         CreateGenerationTaskCommand(
@@ -338,11 +408,28 @@ def retry_generation_task(
             asset_ids=task.asset_ids,
             title_ids=task.title_ids,
             voice_ids=task.voice_ids,
-            created_by_user_id=authenticated_user.user.id,
+            created_by_user_id=user_id,
             source_edit_plan_id=task.source_edit_plan_id or "",
             asset_select_mode=getattr(task, "asset_select_mode", ""),
         )
     )
-    if not safe_enqueue_generation_task(retried, generation_task_repository, log_prefix="[生成任务]", log_task_status=True):
-        logger.warning("[生成任务] 重试入队失败: task_id=%s", retried.id)
+    try:
+        if not safe_enqueue_generation_task(
+            retried,
+            generation_task_repository,
+            user_id=user_id,
+            log_prefix="[生成任务]",
+            log_task_status=True,
+        ):
+            logger.warning("[生成任务] 重试入队失败: task_id=%s", retried.id)
+    except UserPendingLimitExceeded:
+        raise HTTPException(
+            status_code=429,
+            detail="您的待处理任务过多，请等待完成后再提交",
+        ) from None
+    except GlobalQueueFull:
+        raise HTTPException(
+            status_code=503,
+            detail="系统繁忙，请稍后再试",
+        ) from None
     return _to_generation_task_response(retried)

apps/api/app/api/routes/task_center.py

@@ -3,7 +3,13 @@ from typing import Any
 
 from app.auth import AuthenticatedUser, get_current_user
 from app.core.celery_app import celery_app
-from app.core.task_enqueue import safe_enqueue_generation_task
+from app.core.task_enqueue import (
+    GLOBAL_PENDING_LIMIT,
+    USER_PENDING_LIMIT,
+    GlobalQueueFull,
+    UserPendingLimitExceeded,
+    safe_enqueue_generation_task,
+)
 from app.dependencies import (
     get_generation_task_repository,
     get_ingest_job_repository,
@@ -142,6 +148,21 @@ def retry_task_by_id(
     if _status_value(task.status) != "failed":
         raise HTTPException(status_code=409, detail="Only failed tasks can be retried")
 
+    user_id = authenticated_user.user.id
+    # 预检查
+    user_pending = generation_task_repository.count_pending_by_user(user_id)
+    global_pending = generation_task_repository.count_pending_total()
+    if user_pending >= USER_PENDING_LIMIT:
+        raise HTTPException(
+            status_code=429,
+            detail=f"您的待处理任务过多（当前 {user_pending}/{USER_PENDING_LIMIT}），请等待完成后再提交",
+        )
+    if global_pending >= GLOBAL_PENDING_LIMIT:
+        raise HTTPException(
+            status_code=503,
+            detail="系统繁忙，请稍后再试",
+        )
+
     use_case = CreateGenerationTaskUseCase(generation_task_repository)
     retried = use_case.execute(
         CreateGenerationTaskCommand(
@@ -153,11 +174,24 @@ def retry_task_by_id(
             asset_ids=task.asset_ids,
             title_ids=task.title_ids,
             voice_ids=task.voice_ids,
-            created_by_user_id=authenticated_user.user.id,
+            created_by_user_id=user_id,
         )
     )
-    if not safe_enqueue_generation_task(retried, generation_task_repository, log_prefix="[任务中心]"):
-        logger.warning("[任务中心] 用户级重试入队失败: task_id=%s", retried.id)
+    try:
+        if not safe_enqueue_generation_task(
+            retried, generation_task_repository, user_id=user_id, log_prefix="[任务中心]"
+        ):
+            logger.warning("[任务中心] 用户级重试入队失败: task_id=%s", retried.id)
+    except UserPendingLimitExceeded:
+        raise HTTPException(
+            status_code=429,
+            detail="您的待处理任务过多，请等待完成后再提交",
+        ) from None
+    except GlobalQueueFull:
+        raise HTTPException(
+            status_code=503,
+            detail="系统繁忙，请稍后再试",
+        ) from None
     return UserTaskResponse(
         id=f"generation:{retried.id}",
         task_type="generation",
@@ -225,6 +259,22 @@ def retry_project_task(
             raise HTTPException(status_code=404, detail="Generation task not found")
         if _status_value(task.status) != "failed":
             raise HTTPException(status_code=409, detail="Only failed tasks can be retried")
+
+        user_id = authenticated_user.user.id
+        # 预检查
+        user_pending = generation_task_repository.count_pending_by_user(user_id)
+        global_pending = generation_task_repository.count_pending_total()
+        if user_pending >= USER_PENDING_LIMIT:
+            raise HTTPException(
+                status_code=429,
+                detail=f"您的待处理任务过多（当前 {user_pending}/{USER_PENDING_LIMIT}），请等待完成后再提交",
+            )
+        if global_pending >= GLOBAL_PENDING_LIMIT:
+            raise HTTPException(
+                status_code=503,
+                detail="系统繁忙，请稍后再试",
+            )
+
         use_case = CreateGenerationTaskUseCase(generation_task_repository)
         retried = use_case.execute(
             CreateGenerationTaskCommand(
@@ -236,11 +286,24 @@ def retry_project_task(
                 asset_ids=task.asset_ids,
                 title_ids=task.title_ids,
                 voice_ids=task.voice_ids,
-                created_by_user_id=authenticated_user.user.id,
+                created_by_user_id=user_id,
             )
         )
-        if not safe_enqueue_generation_task(retried, generation_task_repository, log_prefix="[任务中心]"):
-            logger.warning("[任务中心] 项目级重试用队失败: task_id=%s", retried.id)
+        try:
+            if not safe_enqueue_generation_task(
+                retried, generation_task_repository, user_id=user_id, log_prefix="[任务中心]"
+            ):
+                logger.warning("[任务中心] 项目级重试入队失败: task_id=%s", retried.id)
+        except UserPendingLimitExceeded:
+            raise HTTPException(
+                status_code=429,
+                detail="您的待处理任务过多，请等待完成后再提交",
+            ) from None
+        except GlobalQueueFull:
+            raise HTTPException(
+                status_code=503,
+                detail="系统繁忙，请稍后再试",
+            ) from None
         return _generation_task_to_project_response(retried)
     if task_type == "ingest":
         job = ingest_job_repository.get(source_id)

apps/api/app/core/task_enqueue.py

@@ -5,37 +5,167 @@ from app.core.celery_app import celery_app
 
 logger = logging.getLogger(__name__)
 
+# ── 限流阈值常量（全系统统一管理，不要在业务代码里硬编码） ──
+USER_PENDING_LIMIT = 3       # 单用户 pending 上限
+GLOBAL_PENDING_LIMIT = 20    # 全局 pending 上限
+
+
+class UserPendingLimitExceeded(Exception):
+    """用户 pending 任务数超限，返回 429。"""
+
+    def __init__(self, user_id: str, pending_count: int, limit: int):
+        self.user_id = user_id
+        self.pending_count = pending_count
+        self.limit = limit
+        super().__init__(f"用户 {user_id} pending 任务数 {pending_count} 超过上限 {limit}")
+
+
+class GlobalQueueFull(Exception):
+    """全局限流，返回 503。"""
+
+    def __init__(self, pending_count: int, limit: int):
+        self.pending_count = pending_count
+        self.limit = limit
+        super().__init__(f"系统 pending 任务数 {pending_count} 超过上限 {limit}")
+
+
+def check_queue_limits(
+    user_id: str,
+    generation_task_repository: Any,
+    *,
+    user_pending_limit: int = USER_PENDING_LIMIT,
+    global_pending_limit: int = GLOBAL_PENDING_LIMIT,
+) -> None:
+    """检查队列限流（预检查用，任务创建前调用），超限抛对应异常。
+
+    边界语义：>= 上限即拒绝（达到上限就不能再加新任务）。
+
+    Args:
+        user_id: 用户 ID
+        generation_task_repository: 任务仓储
+        user_pending_limit: 单用户 pending 上限，默认 USER_PENDING_LIMIT
+        global_pending_limit: 全局 pending 上限，默认 GLOBAL_PENDING_LIMIT
+
+    Raises:
+        GlobalQueueFull: 全局超限时抛出（优先级更高，先查全局）
+        UserPendingLimitExceeded: 用户超限时抛出
+    """
+    # 先查全局（系统级保护优先级更高）
+    global_pending = generation_task_repository.count_pending_total()
+    if global_pending >= global_pending_limit:
+        logger.warning(
+            "[队列限流] 全局 pending 任务数超限: %d/%d, user_id=%s",
+            global_pending,
+            global_pending_limit,
+            user_id,
+        )
+        raise GlobalQueueFull(pending_count=global_pending, limit=global_pending_limit)
+
+    # 再查用户级
+    if user_id:
+        user_pending = generation_task_repository.count_pending_by_user(user_id)
+        if user_pending >= user_pending_limit:
+            logger.warning(
+                "[队列限流] 用户 pending 任务数超限: user_id=%s, count=%d/%d",
+                user_id,
+                user_pending,
+                user_pending_limit,
+            )
+            raise UserPendingLimitExceeded(
+                user_id=user_id, pending_count=user_pending, limit=user_pending_limit
+            )
+
+
+def _mark_task_failed_safely(
+    task: Any,
+    generation_task_repository: Any,
+    log_prefix: str,
+    reason: str,
+) -> None:
+    """安全地把任务标记为 failed，更新失败只打日志不崩溃。"""
+    try:
+        task.mark_failed(f"任务被限流拒绝: {reason}")
+        generation_task_repository.update(task)
+    except Exception as update_err:
+        logger.error(
+            "%s 限流后更新状态也失败: task_id=%s error=%s",
+            log_prefix,
+            task.id,
+            update_err,
+            exc_info=True,
+        )
+
 
 def safe_enqueue_generation_task(
     task: Any,
     generation_task_repository: Any,
     *,
+    user_id: str = "",
     log_prefix: str = "[任务队列]",
     log_task_status: bool = False,
+    user_pending_limit: int = USER_PENDING_LIMIT,
+    global_pending_limit: int = GLOBAL_PENDING_LIMIT,
 ) -> bool:
-    """安全入队：send_task 失败时自动把任务标记为 failed，避免留下 pending 僵尸任务。
+    """安全入队：入队前限流检查 → 发送 Celery 任务 → 入队后最终校验兜底。
+
+    边界说明：
+    入队前检查用 > 而非 >=。因为调用此函数时 task 已经是 pending 状态并计入 DB，
+    pending 总数包含了当前任务本身。pending > limit 等价于"其他任务数 >= limit"，
+    与预检查的 >= 语义一致（都是达到上限就拒绝新任务）。
+
+    入队后最终校验：发送 Celery 成功后再查一次 DB 计数，处理并发竞态场景
+    （两个请求同时通过入队前检查，后到的那个在这里被兜住）。
 
     Args:
-        task: 生成任务对象，需有 id 属性和 mark_failed 方法
+        task: 生成任务对象，需有 id 属性和 mark_failed 方法（状态已为 pending）
         generation_task_repository: 任务仓储，用于更新状态
+        user_id: 用户 ID，传了才做用户级限流检查
         log_prefix: 日志前缀，便于区分调用来源
         log_task_status: 成功日志中是否额外打印任务状态
+        user_pending_limit: 单用户 pending 上限，默认 USER_PENDING_LIMIT
+        global_pending_limit: 全局 pending 上限，默认 GLOBAL_PENDING_LIMIT
 
     Returns:
         True 表示入队成功，False 表示入队失败（已标记为 failed）
+
+    Raises:
+        GlobalQueueFull: 全局 pending 超限时抛出，任务会被标记为 failed
+        UserPendingLimitExceeded: 用户 pending 超限时抛出，任务会被标记为 failed
     """
+    # ── 入队前检查：任务已是 pending，用 > 判断（包含当前任务） ──
+
+    # 全局限流检查（始终生效）
+    global_pending = generation_task_repository.count_pending_total()
+    if global_pending > global_pending_limit:
+        logger.warning(
+            "[队列限流] 全局 pending 任务数超限(入队前): %d/%d, user_id=%s",
+            global_pending,
+            global_pending_limit,
+            user_id or "unknown",
+        )
+        exc = GlobalQueueFull(pending_count=global_pending, limit=global_pending_limit)
+        _mark_task_failed_safely(task, generation_task_repository, log_prefix, str(exc))
+        raise exc
+
+    # 用户级限流检查（传了 user_id 才做）
+    if user_id:
+        user_pending = generation_task_repository.count_pending_by_user(user_id)
+        if user_pending > user_pending_limit:
+            logger.warning(
+                "[队列限流] 用户 pending 任务数超限(入队前): user_id=%s, count=%d/%d",
+                user_id,
+                user_pending,
+                user_pending_limit,
+            )
+            exc = UserPendingLimitExceeded(
+                user_id=user_id, pending_count=user_pending, limit=user_pending_limit
+            )
+            _mark_task_failed_safely(task, generation_task_repository, log_prefix, str(exc))
+            raise exc
+
+    # ── 发送 Celery 任务 ──
     try:
         celery_app.send_task("worker.generate_video", args=[task.id])
-        if log_task_status:
-            logger.info(
-                "%s 入队成功: task_id=%s, status=%s",
-                log_prefix,
-                task.id,
-                task.status,
-            )
-        else:
-            logger.info("%s 入队成功: task_id=%s", log_prefix, task.id)
-        return True
     except Exception as e:
         logger.error(
             "%s 入队失败，标记为失败: task_id=%s error=%s",
@@ -56,3 +186,42 @@ def safe_enqueue_generation_task(
                 exc_info=True,
             )
         return False
+
+    # ── 入队后最终校验：并发竞态兜底 ──
+    # 发送成功后再查一次，防止两个请求同时通过入队前检查导致超限
+    global_after = generation_task_repository.count_pending_total()
+    user_after = generation_task_repository.count_pending_by_user(user_id) if user_id else 0
+
+    global_over = global_after > global_pending_limit
+    user_over = bool(user_id and user_after > user_pending_limit)
+
+    if global_over or user_over:
+        if global_over:
+            reason = f"全局 pending 超限(入队后): {global_after}/{global_pending_limit}"
+            exc: Exception = GlobalQueueFull(pending_count=global_after, limit=global_pending_limit)
+        else:
+            reason = f"用户 pending 超限(入队后): {user_after}/{user_pending_limit}"
+            exc = UserPendingLimitExceeded(
+                user_id=user_id, pending_count=user_after, limit=user_pending_limit
+            )
+
+        logger.warning(
+            "[队列限流] %s, task_id=%s, user_id=%s — 回滚状态为 failed",
+            reason,
+            task.id,
+            user_id or "unknown",
+        )
+        _mark_task_failed_safely(task, generation_task_repository, log_prefix, reason)
+        raise exc
+
+    # 入队成功日志
+    if log_task_status:
+        logger.info(
+            "%s 入队成功: task_id=%s, status=%s",
+            log_prefix,
+            task.id,
+            task.status,
+        )
+    else:
+        logger.info("%s 入队成功: task_id=%s", log_prefix, task.id)
+    return True

packages/adapters/sqlalchemy_impl/generation_task_repository.py

@@ -91,6 +91,23 @@ class SQLAlchemyGenerationTaskRepository:
     def count_by_user(self, user_id: str) -> int:
         return self.session.query(GenerationTaskModel).filter(GenerationTaskModel.created_by_user_id == user_id).count()
 
+    def count_pending_by_user(self, user_id: str) -> int:
+        return (
+            self.session.query(GenerationTaskModel)
+            .filter(
+                GenerationTaskModel.created_by_user_id == user_id,
+                GenerationTaskModel.status == GenerationTaskStatus.PENDING.value,
+            )
+            .count()
+        )
+
+    def count_pending_total(self) -> int:
+        return (
+            self.session.query(GenerationTaskModel)
+            .filter(GenerationTaskModel.status == GenerationTaskStatus.PENDING.value)
+            .count()
+        )
+
     def list_recent_by_user(self, user_id: str, limit: int = 5) -> list[GenerationTask]:
         models = (
             self.session.query(GenerationTaskModel)

packages/ports/generation_task_repository.py

@@ -16,6 +16,10 @@ class GenerationTaskRepository(Protocol):
 
     def count_by_user(self, user_id: str) -> int: ...
 
+    def count_pending_by_user(self, user_id: str) -> int: ...
+
+    def count_pending_total(self) -> int: ...
+
     def list_recent_by_user(self, user_id: str, limit: int = 5) -> list[GenerationTask]: ...
 
     def list_by_source_edit_plan(self, plan_id: str) -> list[GenerationTask]: ...

tests/unit/test_task_queue_limit.py

@@ -0,0 +1,351 @@
+"""任务队列限流防护单元测试。"""
+from __future__ import annotations
+
+import sys
+import os
+from unittest.mock import MagicMock
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "apps", "api"))
+
+from app.core.task_enqueue import (
+    GLOBAL_PENDING_LIMIT,
+    USER_PENDING_LIMIT,
+    GlobalQueueFull,
+    UserPendingLimitExceeded,
+    check_queue_limits,
+    safe_enqueue_generation_task,
+)
+
+
+# ---------------------------------------------------------------------------
+# Mock helpers
+# ---------------------------------------------------------------------------
+
+
+class MockRepository:
+    """支持 pending 计数的 mock repository。
+
+    支持通过 set_pending 动态修改计数，用于模拟入队后计数变化的并发场景。
+    """
+
+    def __init__(self, user_pending: int = 0, global_pending: int = 0):
+        self._user_pending = user_pending
+        self._global_pending = global_pending
+        self._send_task_called = False
+        self.updated_tasks = []
+
+    def count_pending_by_user(self, user_id: str) -> int:
+        return self._user_pending
+
+    def count_pending_total(self) -> int:
+        return self._global_pending
+
+    def update(self, task):
+        self.updated_tasks.append(task)
+        return task
+
+    def set_pending(self, *, user_pending: int | None = None, global_pending: int | None = None):
+        """动态修改 pending 计数，模拟并发场景。"""
+        if user_pending is not None:
+            self._user_pending = user_pending
+        if global_pending is not None:
+            self._global_pending = global_pending
+
+
+class MockTask:
+    def __init__(self, task_id: str = "task-1", status: str = "pending"):
+        self.id = task_id
+        self.status = status
+        self.error_message = ""
+
+    def mark_failed(self, reason: str):
+        self.status = "failed"
+        self.error_message = reason
+
+
+@pytest.fixture(autouse=True)
+def mock_celery(monkeypatch):
+    """mock 掉 celery_app.send_task，避免真实发送。"""
+    mock_send = MagicMock()
+    monkeypatch.setattr("app.core.celery_app.celery_app.send_task", mock_send)
+    return mock_send
+
+
+# ---------------------------------------------------------------------------
+# 常量导出测试
+# ---------------------------------------------------------------------------
+
+
+def test_limit_constants_are_exported():
+    """限流阈值常量已导出，供业务代码引用。"""
+    assert USER_PENDING_LIMIT == 3
+    assert GLOBAL_PENDING_LIMIT == 20
+
+
+# ---------------------------------------------------------------------------
+# check_queue_limits 单元测试（预检查用，>= 边界）
+# ---------------------------------------------------------------------------
+
+
+class TestCheckQueueLimits:
+    """队列限流检查函数测试（预检查语义，>= 上限即拒绝）。"""
+
+    def test_normal_passes_through(self):
+        """正常范围内的任务不受限制。"""
+        repo = MockRepository(user_pending=1, global_pending=5)
+        check_queue_limits("user-1", repo)
+
+    def test_user_limit_exceeded_raises(self):
+        """用户 pending 超过上限抛 UserPendingLimitExceeded。"""
+        repo = MockRepository(user_pending=4, global_pending=5)
+        with pytest.raises(UserPendingLimitExceeded) as exc_info:
+            check_queue_limits("user-1", repo)
+        assert exc_info.value.user_id == "user-1"
+        assert exc_info.value.pending_count == 4
+        assert exc_info.value.limit == 3
+
+    def test_user_at_limit_also_raises(self):
+        """用户 pending 刚好等于上限也拒绝（>= 边界）。"""
+        repo = MockRepository(user_pending=3, global_pending=5)
+        with pytest.raises(UserPendingLimitExceeded):
+            check_queue_limits("user-1", repo)
+
+    def test_user_below_limit_passes(self):
+        """用户 pending 比上限少 1，通过。"""
+        repo = MockRepository(user_pending=2, global_pending=5)
+        check_queue_limits("user-1", repo)
+
+    def test_global_limit_exceeded_raises(self):
+        """全局 pending 超过上限抛 GlobalQueueFull。"""
+        repo = MockRepository(user_pending=1, global_pending=21)
+        with pytest.raises(GlobalQueueFull) as exc_info:
+            check_queue_limits("user-1", repo)
+        assert exc_info.value.pending_count == 21
+        assert exc_info.value.limit == 20
+
+    def test_global_at_limit_also_raises(self):
+        """全局 pending 刚好等于上限也拒绝（>= 边界）。"""
+        repo = MockRepository(user_pending=1, global_pending=20)
+        with pytest.raises(GlobalQueueFull):
+            check_queue_limits("user-1", repo)
+
+    def test_global_below_limit_passes(self):
+        """全局 pending 比上限少 1，通过。"""
+        repo = MockRepository(user_pending=1, global_pending=19)
+        check_queue_limits("user-1", repo)
+
+    def test_global_takes_priority_over_user(self):
+        """全局和用户都超限时，优先抛全局异常。"""
+        repo = MockRepository(user_pending=5, global_pending=25)
+        with pytest.raises(GlobalQueueFull):
+            check_queue_limits("user-1", repo)
+
+    def test_empty_user_id_skips_user_check(self):
+        """不传 user_id 时跳过用户级检查，只做全局检查。"""
+        repo = MockRepository(user_pending=10, global_pending=5)
+        # 用户超限但不传 user_id → 全局未超限，应该通过
+        check_queue_limits("", repo)
+
+
+# ---------------------------------------------------------------------------
+# safe_enqueue_generation_task 限流集成测试（入队前用 >，包含当前任务）
+# ---------------------------------------------------------------------------
+
+
+class TestSafeEnqueueWithLimits:
+    """安全入队函数的限流功能测试。"""
+
+    def test_normal_task_enqueues_successfully(self, mock_celery):
+        """正常任务入队成功，返回 True。"""
+        repo = MockRepository(user_pending=0, global_pending=0)
+        task = MockTask("task-1")
+        result = safe_enqueue_generation_task(task, repo, user_id="user-1")
+        assert result is True
+        mock_celery.assert_called_once_with("worker.generate_video", args=["task-1"])
+        assert len(repo.updated_tasks) == 0  # 成功不需要更新状态
+
+    def test_user_limit_rejected_with_failed_status(self, mock_celery):
+        """用户超限：任务标记为 failed，抛 UserPendingLimitExceeded。"""
+        repo = MockRepository(user_pending=5, global_pending=5)
+        task = MockTask("task-1")
+        with pytest.raises(UserPendingLimitExceeded):
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+        mock_celery.assert_not_called()
+        assert task.status == "failed"
+        assert "限流" in task.error_message
+        assert len(repo.updated_tasks) == 1
+
+    def test_user_at_limit_still_passes(self, mock_celery):
+        """用户 pending 刚好等于上限：入队前检查用 >，包含当前任务，刚好到上限不算超。
+
+        与预检查的 >= 语义一致：预检查时 pending=3 拒绝（不能再加新的），
+        但 safe_enqueue 被调用时任务已是 pending（就是第3个），
+        pending=3 不满足 >3，所以通过。
+        """
+        repo = MockRepository(user_pending=3, global_pending=5)
+        task = MockTask("task-1")
+        result = safe_enqueue_generation_task(task, repo, user_id="user-1")
+        assert result is True
+        mock_celery.assert_called_once()
+
+    def test_user_one_over_limit_rejected(self, mock_celery):
+        """用户 pending = limit + 1：超限被拒。"""
+        repo = MockRepository(user_pending=4, global_pending=5)
+        task = MockTask("task-1")
+        with pytest.raises(UserPendingLimitExceeded):
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+        mock_celery.assert_not_called()
+
+    def test_global_limit_rejected_with_failed_status(self, mock_celery):
+        """全局超限：任务标记为 failed，抛 GlobalQueueFull。"""
+        repo = MockRepository(user_pending=1, global_pending=21)
+        task = MockTask("task-1")
+        with pytest.raises(GlobalQueueFull):
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+        mock_celery.assert_not_called()
+        assert task.status == "failed"
+        assert len(repo.updated_tasks) == 1
+
+    def test_global_at_limit_still_passes(self, mock_celery):
+        """全局 pending 刚好等于上限：入队前检查用 >，包含当前任务，刚好到上限不算超。"""
+        repo = MockRepository(user_pending=1, global_pending=20)
+        task = MockTask("task-1")
+        result = safe_enqueue_generation_task(task, repo, user_id="user-1")
+        assert result is True
+        mock_celery.assert_called_once()
+
+    def test_no_user_id_skips_user_limit(self, mock_celery):
+        """不传 user_id 时跳过用户级限流，只做全局检查。"""
+        repo = MockRepository(user_pending=10, global_pending=5)
+        task = MockTask("task-1")
+        result = safe_enqueue_generation_task(task, repo, user_id="")
+        assert result is True
+        mock_celery.assert_called_once()
+
+    def test_no_user_id_still_checks_global(self, mock_celery):
+        """不传 user_id 时全局超限仍然被拦。"""
+        repo = MockRepository(user_pending=10, global_pending=25)
+        task = MockTask("task-1")
+        with pytest.raises(GlobalQueueFull):
+            safe_enqueue_generation_task(task, repo, user_id="")
+        mock_celery.assert_not_called()
+
+    def test_default_limits_match_constants(self, mock_celery):
+        """默认配置与导出常量一致。"""
+        # 刚好在默认限制内（limit - 1）
+        repo = MockRepository(user_pending=2, global_pending=19)
+        task = MockTask("task-1")
+        result = safe_enqueue_generation_task(task, repo, user_id="user-1")
+        assert result is True
+
+    def test_update_failure_does_not_crash(self, mock_celery):
+        """repository.update 失败也不崩溃，异常继续向上抛。"""
+
+        class BadRepo(MockRepository):
+            def update(self, task):
+                raise RuntimeError("db down")
+
+        repo = BadRepo(user_pending=5, global_pending=5)
+        task = MockTask("task-1")
+        # 仍然抛 UserPendingLimitExceeded，不会被 update 失败掩盖
+        with pytest.raises(UserPendingLimitExceeded):
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+        mock_celery.assert_not_called()
+        # 任务状态还是变了（内存里改了）
+        assert task.status == "failed"
+
+
+# ---------------------------------------------------------------------------
+# 入队后最终校验（并发竞态兜底）测试
+# ---------------------------------------------------------------------------
+
+
+class TestPostEnqueueFinalCheck:
+    """入队后最终校验：模拟并发场景，Celery发送后计数增加被兜住。"""
+
+    def test_post_enqueue_global_overflow_rollback(self, mock_celery):
+        """并发场景：入队前检查通过，但发送Celery后全局计数超限 → 回滚为failed。
+
+        模拟两个请求同时通过入队前检查（都查到 global=19），
+        都创建了任务（DB里变成 21），先发送Celery的那个在最终校验时被兜住。
+        """
+        repo = MockRepository(user_pending=1, global_pending=20)  # 入队前：20 > 20？否
+        task = MockTask("task-1")
+
+        # 模拟发送Celery后，另一个并发请求也创建了任务，全局变成21
+        def side_effect(*args, **kwargs):
+            repo.set_pending(global_pending=21)
+
+        mock_celery.side_effect = side_effect
+
+        with pytest.raises(GlobalQueueFull) as exc_info:
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+
+        # Celery 确实发出去了（兜底不撤销 Celery，只回滚 DB 状态）
+        mock_celery.assert_called_once()
+        # 任务被标记为 failed
+        assert task.status == "failed"
+        assert "入队后" in task.error_message
+        assert exc_info.value.pending_count == 21
+        assert len(repo.updated_tasks) == 1
+
+    def test_post_enqueue_user_overflow_rollback(self, mock_celery):
+        """并发场景：入队前检查通过，但发送Celery后用户计数超限 → 回滚为failed。"""
+        repo = MockRepository(user_pending=3, global_pending=5)  # 入队前：3 > 3？否
+        task = MockTask("task-1")
+
+        def side_effect(*args, **kwargs):
+            repo.set_pending(user_pending=4)
+
+        mock_celery.side_effect = side_effect
+
+        with pytest.raises(UserPendingLimitExceeded) as exc_info:
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+
+        mock_celery.assert_called_once()
+        assert task.status == "failed"
+        assert "入队后" in task.error_message
+        assert exc_info.value.user_id == "user-1"
+        assert exc_info.value.pending_count == 4
+
+    def test_post_enqueue_global_priority_over_user(self, mock_celery):
+        """入队后校验：全局和用户都超限时，优先抛全局异常。"""
+        repo = MockRepository(user_pending=3, global_pending=20)
+        task = MockTask("task-1")
+
+        def side_effect(*args, **kwargs):
+            repo.set_pending(user_pending=5, global_pending=22)
+
+        mock_celery.side_effect = side_effect
+
+        with pytest.raises(GlobalQueueFull):
+            safe_enqueue_generation_task(task, repo, user_id="user-1")
+
+        assert task.status == "failed"
+
+    def test_post_enqueue_no_change_still_passes(self, mock_celery):
+        """入队后计数没变 → 正常通过，不回滚。"""
+        repo = MockRepository(user_pending=2, global_pending=10)
+        task = MockTask("task-1")
+
+        result = safe_enqueue_generation_task(task, repo, user_id="user-1")
+
+        assert result is True
+        mock_celery.assert_called_once()
+        assert task.status == "pending"  # 状态没变
+        assert len(repo.updated_tasks) == 0  # 没更新 DB
+
+    def test_post_enqueue_no_user_id_skips_user_check(self, mock_celery):
+        """不传 user_id 时，入队后校验也跳过用户级，只查全局。"""
+        repo = MockRepository(user_pending=10, global_pending=5)
+        task = MockTask("task-1")
+
+        def side_effect(*args, **kwargs):
+            repo.set_pending(user_pending=15, global_pending=5)  # 用户超限但全局没超
+
+        mock_celery.side_effect = side_effect
+
+        result = safe_enqueue_generation_task(task, repo, user_id="")
+        assert result is True  # 用户级不检查，全局没超限 → 通过