diff --git a/airflow-core/src/airflow/api_fastapi/execution_api/routes/hitl.py b/airflow-core/src/airflow/api_fastapi/execution_api/routes/hitl.py
index 8a6606bd28028..85d8e008990da 100644
--- a/airflow-core/src/airflow/api_fastapi/execution_api/routes/hitl.py
+++ b/airflow-core/src/airflow/api_fastapi/execution_api/routes/hitl.py
@@ -116,7 +116,7 @@ def update_hitl_detail(
             f"Human-in-the-loop detail for Task Instance with id {ti_id_str} already exists.",
         )
 
-    hitl_detail_model.responded_by = HITLDetail.DEFAULT_USER
+    hitl_detail_model.responded_by = None
     hitl_detail_model.response_at = datetime.now(timezone.utc)
     hitl_detail_model.chosen_options = payload.chosen_options
     hitl_detail_model.params_input = payload.params_input
diff --git a/airflow-core/src/airflow/models/hitl.py b/airflow-core/src/airflow/models/hitl.py
index e2055344bc3ec..7f0069688c1ab 100644
--- a/airflow-core/src/airflow/models/hitl.py
+++ b/airflow-core/src/airflow/models/hitl.py
@@ -167,8 +167,3 @@ def responded_by_user(self) -> HITLUser | None:
             id=self.responded_by["id"],
             name=self.responded_by["name"],
         )
-
-    DEFAULT_USER = HITLUser(
-        id="Fallback to defaults",
-        name="Fallback to defaults",
-    )
diff --git a/airflow-core/tests/unit/api_fastapi/execution_api/versions/head/test_hitl.py b/airflow-core/tests/unit/api_fastapi/execution_api/versions/head/test_hitl.py
index 764d5a48ccdc6..33a1b3e79bcab 100644
--- a/airflow-core/tests/unit/api_fastapi/execution_api/versions/head/test_hitl.py
+++ b/airflow-core/tests/unit/api_fastapi/execution_api/versions/head/test_hitl.py
@@ -93,7 +93,7 @@ def expected_sample_hitl_detail_dict(sample_ti: TaskInstance) -> dict[str, Any]:
                 "params_input": {"input_1": 2},
                 "response_at": convert_to_utc(datetime(2025, 7, 3, 0, 0, 0)),
                 "chosen_options": ["Reject"],
-                "responded_by": {"id": "Fallback to defaults", "name": "Fallback to defaults"},
+                "responded_by": None,
             },
         },
     ],
@@ -174,10 +174,7 @@ def test_update_hitl_detail(client: Client, sample_ti: TaskInstance) -> None:
         "response_at": "2025-07-03T00:00:00Z",
         "chosen_options": ["Reject"],
         "response_received": True,
-        "responded_by_user": {
-            "id": "Fallback to defaults",
-            "name": "Fallback to defaults",
-        },
+        "responded_by_user": None,
     }
 
 
diff --git a/providers/standard/src/airflow/providers/standard/triggers/hitl.py b/providers/standard/src/airflow/providers/standard/triggers/hitl.py
index a9299ae240756..bdaa84b01f6dd 100644
--- a/providers/standard/src/airflow/providers/standard/triggers/hitl.py
+++ b/providers/standard/src/airflow/providers/standard/triggers/hitl.py
@@ -44,7 +44,7 @@ class HITLTriggerEventSuccessPayload(TypedDict, total=False):
 
     chosen_options: list[str]
     params_input: dict[str, Any]
-    responded_by_user: HITLUser
+    responded_by_user: HITLUser | None
     timedout: bool
 
 
@@ -148,10 +148,7 @@ async def run(self) -> AsyncIterator[TriggerEvent]:
                     HITLTriggerEventSuccessPayload(
                         chosen_options=self.defaults,
                         params_input=self.params,
-                        responded_by_user=HITLUser(
-                            id="Fallback to defaults",
-                            name="Fallback to defaults",
-                        ),
+                        responded_by_user=None,
                         timedout=True,
                     )
                 )
diff --git a/providers/standard/tests/unit/standard/triggers/test_hitl.py b/providers/standard/tests/unit/standard/triggers/test_hitl.py
index ef82f9e09d9b0..118bcb77dc1d6 100644
--- a/providers/standard/tests/unit/standard/triggers/test_hitl.py
+++ b/providers/standard/tests/unit/standard/triggers/test_hitl.py
@@ -125,7 +125,7 @@ async def test_run_fallback_to_default_due_to_timeout(self, mock_update, mock_lo
             HITLTriggerEventSuccessPayload(
                 chosen_options=["1"],
                 params_input={"input": 1},
-                responded_by_user={"id": "Fallback to defaults", "name": "Fallback to defaults"},
+                responded_by_user=None,
                 timedout=True,
             )
         )