diff --git a/apps/worker/worker_app/tasks/generation.py b/apps/worker/worker_app/tasks/generation.py
index b5f1f9ea0..7d1a19261 100644
--- a/apps/worker/worker_app/tasks/generation.py
+++ b/apps/worker/worker_app/tasks/generation.py
@@ -863,6 +863,11 @@ def generate_video(self, task_id: str) -> dict:
             if gen_task:
                 gen_task.append_log("任务失败", "缺少 source_edit_plan_id", level="ERROR")
                 _flush_logs(task_id, gen_task)
+            _update_task_status(
+                task_id,
+                "mark_failed",
+                error_message="source_edit_plan_id is required. Please create a preview task first.",
+            )
             return {
                 "status": "failed",
                 "task_id": task_id,
diff --git a/tests/unit/test_empty_plan_id_marks_failed.py b/tests/unit/test_empty_plan_id_marks_failed.py
new file mode 100644
index 000000000..799ac3c84
--- /dev/null
+++ b/tests/unit/test_empty_plan_id_marks_failed.py
@@ -0,0 +1,63 @@
+"""回归测试：source_edit_plan_id 为空时，generate_video 必须调用 mark_failed。
+
+背景 (2026-08-24)：确认生成卡在 10% 永不结束。根因是 worker 在
+source_edit_plan_id 为空时直接 return failed 字典，但没有调用
+_update_task_status(task_id, "mark_failed")，导致 DB 状态永远停在
+running，前端轮询永远等不到完成。
+"""
+from __future__ import annotations
+import re
+from pathlib import Path
+
+
+GENERATION_PY = Path(__file__).resolve().parents[2] / "apps" / "worker" / "worker_app" / "tasks" / "generation.py"
+
+
+def _read_source() -> str:
+    return GENERATION_PY.read_text(encoding="utf-8")
+
+
+class TestEmptyPlanIdMarksFailed:
+    """验证 generation.py 在 source_edit_plan_id 为空的 else 分支中调用了 mark_failed。"""
+
+    def test_else_branch_has_mark_failed(self):
+        """else 分支（source_edit_plan_id 为空）必须在 return 之前调用 mark_failed。"""
+        source = _read_source()
+
+        # 找到 else 分支: 包含 source_edit_plan_id 为空 的日志
+        else_pattern = re.compile(
+            r"else:\s*\n"
+            r"\s+logger\.error\("
+            r"[^)]*source_edit_plan_id",
+            re.DOTALL,
+        )
+        assert else_pattern.search(source), "未找到 source_edit_plan_id 为空的 else 分支"
+
+        else_match = else_pattern.search(source)
+        else_start = else_match.start()
+        else_block = source[else_start:else_start + 800]
+
+        return_match = re.search(r'return\s*\{[^}]*"status"\s*:\s*"failed"', else_block, re.DOTALL)
+        assert return_match, "else 分支中未找到 return failed"
+
+        block_before_return = else_block[:return_match.start()]
+        assert "mark_failed" in block_before_return, (
+            "source_edit_plan_id 为空的 else 分支在 return 之前必须调用 mark_failed"
+        )
+
+    def test_mark_failed_before_return_in_else(self):
+        """mark_failed 调用必须在 return 之前，而非之后。"""
+        source = _read_source()
+
+        else_idx = source.find("source_edit_plan_id 为空，无法渲染")
+        assert else_idx != -1, "未找到 source_edit_plan_id 为空的日志"
+
+        after_else = source[else_idx:]
+        mark_failed_idx = after_else.find('"mark_failed"')
+        return_failed_idx = after_else.find('"status": "failed"')
+
+        assert mark_failed_idx != -1, "else 分支中没有 mark_failed 调用"
+        assert return_failed_idx != -1, "else 分支中没有 return failed"
+        assert mark_failed_idx < return_failed_idx, (
+            f"mark_failed (pos {mark_failed_idx}) 必须在 return failed (pos {return_failed_idx}) 之前"
+        )