diff --git a/app/question_gen/pipeline_v2.py b/app/question_gen/pipeline_v2.py
index 26ae198..8f95c48 100644
--- a/app/question_gen/pipeline_v2.py
+++ b/app/question_gen/pipeline_v2.py
@@ -468,7 +468,7 @@ async def _process_one_slot(
             try:
                 report = await run_gates(
                     candidate=candidate,
-                    tree=tree,
+                    tree=current_tree,
                     llm=llm,
                     leak_probe_template=strategy.leak_probe_template,
                     postprocess=pp,
diff --git a/tests/unit/test_pipeline_v2_tree_fix.py b/tests/unit/test_pipeline_v2_tree_fix.py
new file mode 100644
index 0000000..9b81675
--- /dev/null
+++ b/tests/unit/test_pipeline_v2_tree_fix.py
@@ -0,0 +1,25 @@
+"""守卫 gate tree 错配 bug：run_gates 必须用 current_tree（换视频后的当前树）。"""
+
+import ast
+from pathlib import Path
+
+_PIPELINE = Path(__file__).resolve().parents[2] / "app" / "question_gen" / "pipeline_v2.py"
+
+
+def _find_run_gates_tree_arg() -> str:
+    """解析 pipeline_v2.py，返回 run_gates 调用中 tree= 关键字实参的变量名。"""
+    tree_src = ast.parse(_PIPELINE.read_text(encoding="utf-8"))
+    for node in ast.walk(tree_src):
+        if isinstance(node, ast.Call):
+            func = node.func
+            name = getattr(func, "id", None) or getattr(func, "attr", None)
+            if name == "run_gates":
+                for kw in node.keywords:
+                    if kw.arg == "tree":
+                        assert isinstance(kw.value, ast.Name)
+                        return kw.value.id
+    raise AssertionError("未找到 run_gates 的 tree= 关键字实参")
+
+
+def test_run_gates_uses_current_tree():
+    assert _find_run_gates_tree_arg() == "current_tree"