Do not deserialize trigger_kwargs when loading serialized DAGs

airflow-core/src/airflow/models/taskinstance.py

@@ -1658,7 +1658,9 @@ def defer_task(self, session: Session = NEW_SESSION) -> bool:
             self.state = TaskInstanceState.DEFERRED
             self.trigger_id = trigger_row.id
             self.next_method = start_trigger_args.next_method
-            self.next_kwargs = start_trigger_args.next_kwargs or {}
+            from airflow.serialization.enums import stringify_encoding_keys
+
+            self.next_kwargs = stringify_encoding_keys(start_trigger_args.next_kwargs or {})
             self.start_date = timezone.utcnow()
 
             # If an execution_timeout is set, set the timeout to the minimum of

airflow-core/src/airflow/models/trigger.py

@@ -35,6 +35,7 @@
 from airflow.models.asset import AssetWatcherModel
 from airflow.models.base import Base
 from airflow.models.taskinstance import TaskInstance
+from airflow.serialization.enums import stringify_encoding_keys as _stringify_encoding_keys
 from airflow.triggers.base import BaseTaskEndEvent
 from airflow.utils.retries import run_with_db_retries
 from airflow.utils.session import NEW_SESSION, provide_session
@@ -146,7 +147,7 @@ def encrypt_kwargs(kwargs: dict[str, Any]) -> str:
         from airflow.models.crypto import get_fernet
         from airflow.sdk.serde import serialize
 
-        serialized_kwargs = serialize(kwargs)
+        serialized_kwargs = serialize(_stringify_encoding_keys(kwargs))
         return get_fernet().encrypt(json.dumps(serialized_kwargs).encode("utf-8")).decode("utf-8")
 
     @staticmethod

airflow-core/src/airflow/serialization/enums.py

@@ -20,6 +20,7 @@
 from __future__ import annotations
 
 from enum import Enum, unique
+from typing import Any
 
 
 # Fields of an encoded object in serialization.
@@ -31,6 +32,26 @@ class Encoding(str, Enum):
     VAR = "__var"
 
 
+def stringify_encoding_keys(d: Any) -> Any:
+    """
+    Convert BaseSerialization Encoding enum keys to their string values recursively.
+
+    Python 3.10 compatibility: str(Encoding.TYPE) returns "Encoding.TYPE" on 3.10
+    instead of "__type__" (3.10 is still the default CI target). serde.serialize
+    uses str(k) for dict keys, so without this conversion the encrypted blob ends up
+    with "Encoding.TYPE" keys that neither serde._convert nor the BaseSerialization
+    fallback can read back.
+    """
+    if isinstance(d, dict):
+        return {
+            (k.value if isinstance(k, Encoding) else str(k)): stringify_encoding_keys(v) for k, v in d.items()
+        }
+    if isinstance(d, (list, tuple)):
+        converted = [stringify_encoding_keys(i) for i in d]
+        return type(d)(converted)
+    return d
+
+
 # Supported types for encoding. primitives and list are not encoded.
 @unique
 class DagAttributeTypes(str, Enum):

airflow-core/src/airflow/serialization/serialized_objects.py

@@ -251,17 +251,11 @@ def serialize_kwargs(key: str) -> Any:
 
 def _decode_start_trigger_args(var: dict[str, Any]) -> StartTriggerArgs:
     """Decode a StartTriggerArgs."""
-
-    def deserialize_kwargs(key: str) -> Any:
-        if (val := var[key]) is None:
-            return None
-        return BaseSerialization.deserialize(val)
-
     return StartTriggerArgs(
         trigger_cls=var["trigger_cls"],
-        trigger_kwargs=deserialize_kwargs("trigger_kwargs"),
+        trigger_kwargs=var["trigger_kwargs"],
         next_method=var["next_method"],
-        next_kwargs=deserialize_kwargs("next_kwargs"),
+        next_kwargs=var["next_kwargs"],
         timeout=datetime.timedelta(seconds=var["timeout"]) if var["timeout"] else None,
     )
 

airflow-core/src/airflow/triggers/base.py

@@ -120,9 +120,16 @@ def task_instance(self, value: TaskInstance | None) -> None:
             # does not build a template context, so render_template_fields is
             # never called and empty template_fields is safe.
             start_trigger_args = getattr(self.task, "start_trigger_args", None)
-            trigger_kwarg_keys = (
-                set((start_trigger_args.trigger_kwargs or {}).keys()) if start_trigger_args else set()
-            )
+            if start_trigger_args:
+                from airflow.serialization.enums import Encoding
+
+                raw = start_trigger_args.trigger_kwargs or {}
+                # trigger_kwargs may be BaseSerialization-encoded; extract inner dict keys
+                if isinstance(raw, dict) and Encoding.TYPE in raw:
+                    raw = raw.get(Encoding.VAR) or {}
+                trigger_kwarg_keys = set(raw.keys())
+            else:
+                trigger_kwarg_keys = set()
             if trigger_kwarg_keys:
                 self.template_fields = tuple(
                     f for f in self.task.template_fields if f in trigger_kwarg_keys and hasattr(self, f)
@@ -256,9 +263,11 @@ def hash(classpath: str, kwargs: dict[str, Any]) -> int:
         We do not want to have this logic in ``BaseTrigger`` because, when used to defer tasks, 2 triggers
         can have the same classpath and kwargs. This is not true for event driven scheduling.
         """
+        from airflow.serialization.encoders import encode_trigger
         from airflow.serialization.serialized_objects import BaseSerialization
 
-        return hash((classpath, json.dumps(BaseSerialization.serialize(kwargs)).encode("utf-8")))
+        normalized = encode_trigger({"classpath": classpath, "kwargs": kwargs})["kwargs"]
+        return hash((classpath, json.dumps(BaseSerialization.serialize(normalized)).encode("utf-8")))
 
 
 class TriggerEvent(BaseModel):

airflow-core/tests/unit/jobs/test_triggerer_job.py

@@ -646,15 +646,7 @@ async def test_trigger_kwargs_serialization_cleanup(self, session):
         session.commit()
 
         stored_kwargs = trigger_orm.kwargs
-        assert stored_kwargs == {
-            "Encoding.TYPE": "dict",
-            "Encoding.VAR": {
-                "dict": {"Encoding.TYPE": "dict", "Encoding.VAR": {}},
-                "list": [],
-                "simple": "test",
-                "tuple": {"Encoding.TYPE": "tuple", "Encoding.VAR": []},
-            },
-        }
+        assert stored_kwargs == kw
 
         runner = TriggerRunner()
         runner.to_create.append(

airflow-core/tests/unit/models/test_dagrun.py

@@ -2295,6 +2295,41 @@ def execute_complete(self):
     assert ti.state == TaskInstanceState.DEFERRED
 
 
+@pytest.mark.need_serialized_dag
+def test_schedule_tis_start_trigger_next_kwargs_round_trip(dag_maker, session):
+    """next_kwargs with encoded values (timedelta) must survive the defer_task round-trip."""
+    import datetime
+
+    from airflow.sdk.serde import deserialize
+
+    class TestOperator(BaseOperator):
+        start_trigger_args = StartTriggerArgs(
+            trigger_cls="airflow.triggers.testing.SuccessTrigger",
+            trigger_kwargs={},
+            next_method="execute_complete",
+            next_kwargs={"delay": datetime.timedelta(seconds=30)},
+            timeout=None,
+        )
+        start_from_trigger = True
+
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+
+        def execute_complete(self):
+            pass
+
+    with dag_maker(session=session):
+        TestOperator(task_id="test_task")
+
+    dr: DagRun = dag_maker.create_dagrun()
+    ti = dr.get_task_instance("test_task")
+    ti.task = dr.dag.get_task("test_task")
+    dr.schedule_tis((ti,), session=session)
+
+    assert ti.state == TaskInstanceState.DEFERRED
+    assert deserialize(ti.next_kwargs) == {"delay": datetime.timedelta(seconds=30)}
+
+
 def test_schedule_tis_empty_operator_try_number(dag_maker, session: Session):
     """
     When empty operator is not actually run, then we need to increment the try_number,

airflow-core/tests/unit/serialization/test_dag_serialization.py

@@ -815,6 +815,8 @@ def validate_deserialized_task(
                 "on_failure_fail_dagrun",
                 "_needs_expansion",
                 "_is_sensor",
+                # trigger_kwargs is kept as raw JSON after deserialization; checked separately
+                "start_trigger_args",
             }
         else:  # Promised to be mapped by the assert above.
             assert isinstance(serialized_task, SerializedMappedOperator)
@@ -855,6 +857,20 @@ def validate_deserialized_task(
         else:
             assert serialized_task.resources == task.resources
 
+        # start_trigger_args: trigger_kwargs is kept as raw BaseSerialization-encoded form
+        # after deserialization. Compare the encoded forms directly — s.trigger_kwargs is
+        # exactly BaseSerialization.serialize(o.trigger_kwargs) since _encode_start_trigger_args
+        # serializes it and _decode_start_trigger_args keeps it raw.
+        if task.start_trigger_args is not None:
+            from airflow.serialization.serialized_objects import BaseSerialization
+
+            s = serialized_task.start_trigger_args
+            o = task.start_trigger_args
+            assert s.trigger_cls == o.trigger_cls
+            assert s.next_method == o.next_method
+            assert s.timeout == o.timeout
+            assert s.trigger_kwargs == BaseSerialization.serialize(o.trigger_kwargs or {})
+
         assert [ensure_serialized_asset(i) for i in task.inlets] == serialized_task.inlets
         assert [ensure_serialized_asset(o) for o in task.outlets] == serialized_task.outlets
 
@@ -2627,6 +2643,42 @@ def execute_complete(self):
         }
         assert tasks[1]["__var"]["start_from_trigger"] is True
 
+    def test_trigger_kwargs_not_deserialised_through_serdag(self):
+        """trigger_kwargs and next_kwargs are kept as raw BaseSerialization JSON when loading a serialized DAG."""
+
+        class TestOperator(BaseOperator):
+            start_trigger_args = StartTriggerArgs(
+                trigger_cls="airflow.providers.standard.triggers.temporal.TimeDeltaTrigger",
+                trigger_kwargs={"delta": timedelta(seconds=2)},
+                next_method="execute_complete",
+                next_kwargs={"resume_after": timedelta(seconds=5)},
+                timeout=None,
+            )
+            start_from_trigger = True
+
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+
+            def execute_complete(self):
+                pass
+
+        dag = DAG(dag_id="test_dag_kwargs_raw", schedule=None, start_date=datetime(2023, 11, 9))
+        with dag:
+            TestOperator(task_id="test_task")
+
+        serialized = DagSerialization.to_dict(dag)
+        deserialized_dag = DagSerialization.from_dict(serialized)
+
+        task = deserialized_dag.get_task("test_task")
+        assert task.start_trigger_args.trigger_kwargs == {
+            "__type": "dict",
+            "__var": {"delta": {"__type": "timedelta", "__var": 2.0}},
+        }
+        assert task.start_trigger_args.next_kwargs == {
+            "__type": "dict",
+            "__var": {"resume_after": {"__type": "timedelta", "__var": 5.0}},
+        }
+
 
 def test_kubernetes_optional():
     """Test that serialization module loads without kubernetes, but deserialization of PODs requires it"""