diff --git a/api/core/app/apps/advanced_chat/app_generator.py b/api/core/app/apps/advanced_chat/app_generator.py
index 5d974335ff..da9d7916f7 100644
--- a/api/core/app/apps/advanced_chat/app_generator.py
+++ b/api/core/app/apps/advanced_chat/app_generator.py
@@ -186,6 +186,7 @@ class AdvancedChatAppGenerator(MessageBasedAppGenerator):
             files=list(file_objs),
             parent_message_id=args.get("parent_message_id") if invoke_from != InvokeFrom.SERVICE_API else UUID_NIL,
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=invoke_from,
             extras=extras,
@@ -298,6 +299,7 @@ class AdvancedChatAppGenerator(MessageBasedAppGenerator):
             query="",
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             extras={"auto_generate_conversation_name": False},
@@ -384,6 +386,7 @@ class AdvancedChatAppGenerator(MessageBasedAppGenerator):
             query="",
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             extras={"auto_generate_conversation_name": False},
@@ -595,13 +598,13 @@ class AdvancedChatAppGenerator(MessageBasedAppGenerator):
                     InvokeFrom.SERVICE_API,
                 }
 
-                if is_external_api_call:
-                    # For external API calls, use end user's session ID
-                    end_user = session.scalar(select(EndUser).where(EndUser.id == application_generate_entity.user_id))
-                    system_user_id = end_user.session_id if end_user else ""
-                else:
-                    # For internal calls, use the original user ID
-                    system_user_id = application_generate_entity.user_id
+                # For external API calls, use end user's session ID
+                # For internal calls, use the original user ID
+                system_user_id = (
+                    application_generate_entity.user_session_id
+                    if is_external_api_call
+                    else application_generate_entity.user_id
+                )
 
                 app = session.scalar(select(App).where(App.id == application_generate_entity.app_config.app_id))
                 if app is None:
diff --git a/api/core/app/apps/pipeline/pipeline_generator.py b/api/core/app/apps/pipeline/pipeline_generator.py
index 19d67eb108..1144f3f440 100644
--- a/api/core/app/apps/pipeline/pipeline_generator.py
+++ b/api/core/app/apps/pipeline/pipeline_generator.py
@@ -188,6 +188,7 @@ class PipelineGenerator(BaseAppGenerator):
                 ),
                 files=[],
                 user_id=user.id,
+                user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
                 stream=streaming,
                 invoke_from=invoke_from,
                 call_depth=call_depth,
@@ -392,6 +393,7 @@ class PipelineGenerator(BaseAppGenerator):
             inputs={},
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             call_depth=0,
@@ -489,6 +491,7 @@ class PipelineGenerator(BaseAppGenerator):
             inputs={},
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             extras={"auto_generate_conversation_name": False},
@@ -576,15 +579,14 @@ class PipelineGenerator(BaseAppGenerator):
                         InvokeFrom.SERVICE_API,
                     }
 
-                    if is_external_api_call:
-                        # For external API calls, use end user's session ID
-                        end_user = session.scalar(
-                            select(EndUser).where(EndUser.id == application_generate_entity.user_id)
-                        )
-                        system_user_id = end_user.session_id if end_user else ""
-                    else:
-                        # For internal calls, use the original user ID
-                        system_user_id = application_generate_entity.user_id
+                    # For external API calls, use end user's session ID
+                    # For internal calls, use the original user ID
+                    system_user_id = (
+                        application_generate_entity.user_session_id
+                        if is_external_api_call
+                        else application_generate_entity.user_id
+                    )
+
                     # workflow app
                     runner = PipelineRunner(
                         application_generate_entity=application_generate_entity,
diff --git a/api/core/app/apps/workflow/app_generator.py b/api/core/app/apps/workflow/app_generator.py
index 6fbe19a3b2..d0823ebf72 100644
--- a/api/core/app/apps/workflow/app_generator.py
+++ b/api/core/app/apps/workflow/app_generator.py
@@ -180,6 +180,7 @@ class WorkflowAppGenerator(BaseAppGenerator):
             inputs=inputs,
             files=list(system_files),
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=invoke_from,
             call_depth=call_depth,
@@ -384,6 +385,7 @@ class WorkflowAppGenerator(BaseAppGenerator):
             inputs={},
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             extras={"auto_generate_conversation_name": False},
@@ -470,6 +472,7 @@ class WorkflowAppGenerator(BaseAppGenerator):
             inputs={},
             files=[],
             user_id=user.id,
+            user_session_id=user.session_id if isinstance(user, EndUser) else user.id,
             stream=streaming,
             invoke_from=InvokeFrom.DEBUGGER,
             extras={"auto_generate_conversation_name": False},
@@ -557,13 +560,13 @@ class WorkflowAppGenerator(BaseAppGenerator):
                     InvokeFrom.SERVICE_API,
                 }
 
-                if is_external_api_call:
-                    # For external API calls, use end user's session ID
-                    end_user = session.scalar(select(EndUser).where(EndUser.id == application_generate_entity.user_id))
-                    system_user_id = end_user.session_id if end_user else ""
-                else:
-                    # For internal calls, use the original user ID
-                    system_user_id = application_generate_entity.user_id
+                # For external API calls, use end user's session ID
+                # For internal calls, use the original user ID
+                system_user_id = (
+                    application_generate_entity.user_session_id
+                    if is_external_api_call
+                    else application_generate_entity.user_id
+                )
 
             runner = WorkflowAppRunner(
                 application_generate_entity=application_generate_entity,
diff --git a/api/core/app/entities/app_invoke_entities.py b/api/core/app/entities/app_invoke_entities.py
index ecbb1cf2f3..9369622336 100644
--- a/api/core/app/entities/app_invoke_entities.py
+++ b/api/core/app/entities/app_invoke_entities.py
@@ -118,6 +118,11 @@ class AppGenerateEntity(BaseModel):
     # Note: The `user_id` field does not indicate whether the user is a platform user or an end user.
     user_id: str
 
+    # Session identifier used as system_user_id in workflow execution.
+    # For external API calls (SERVICE_API / WEB_APP): holds EndUser.session_id.
+    # For internal calls (DEBUGGER / EXPLORE): holds Account.id (same as user_id).
+    user_session_id: str = ""
+
     # extras
     stream: bool
     invoke_from: InvokeFrom
diff --git a/api/tests/unit_tests/core/app/apps/pipeline/test_pipeline_generator.py b/api/tests/unit_tests/core/app/apps/pipeline/test_pipeline_generator.py
index 06face41fe..5f57ad595d 100644
--- a/api/tests/unit_tests/core/app/apps/pipeline/test_pipeline_generator.py
+++ b/api/tests/unit_tests/core/app/apps/pipeline/test_pipeline_generator.py
@@ -283,10 +283,11 @@ def test_generate_worker_handles_errors(generator, mocker):
         app_config=SimpleNamespace(tenant_id="tenant", app_id="pipe", workflow_id="wf"),
         invoke_from=InvokeFrom.WEB_APP,
         user_id="user",
+        user_session_id="session",
     )
 
     session = DummySession()
-    session.scalar.side_effect = [MagicMock(), MagicMock(session_id="session")]
+    session.scalar.side_effect = [MagicMock()]
     _patch_session(mocker, session)
 
     runner_instance = MagicMock()
@@ -318,10 +319,11 @@ def test_generate_worker_sets_system_user_id_for_external_call(generator, mocker
         app_config=SimpleNamespace(tenant_id="tenant", app_id="pipe", workflow_id="wf"),
         invoke_from=InvokeFrom.WEB_APP,
         user_id="user",
+        user_session_id="session",
     )
 
     session = DummySession()
-    session.scalar.side_effect = [MagicMock(), MagicMock(session_id="session")]
+    session.scalar.side_effect = [MagicMock()]
     _patch_session(mocker, session)
 
     runner_instance = MagicMock()
diff --git a/api/tests/unit_tests/core/app/apps/test_workflow_app_generator.py b/api/tests/unit_tests/core/app/apps/test_workflow_app_generator.py
index 7e8367c6c4..561cc745fd 100644
--- a/api/tests/unit_tests/core/app/apps/test_workflow_app_generator.py
+++ b/api/tests/unit_tests/core/app/apps/test_workflow_app_generator.py
@@ -146,13 +146,12 @@ def test_resume_path_runs_worker_with_runtime_state(mocker):
     workflow = SimpleNamespace(
         id="workflow", tenant_id="tenant", app_id="app", graph_dict={}, type="workflow", version="1"
     )
-    end_user = SimpleNamespace(session_id="end-user-session")
     app_record = SimpleNamespace(id="app")
 
     session = MagicMock()
     session.__enter__.return_value = session
     session.__exit__.return_value = False
-    session.scalar.side_effect = [workflow, end_user, app_record]
+    session.scalar.side_effect = [workflow, app_record]
     mocker.patch("core.app.apps.workflow.app_generator.session_factory", return_value=session)
 
     runner_instance = MagicMock()
@@ -188,6 +187,7 @@ def test_resume_path_runs_worker_with_runtime_state(mocker):
     application_generate_entity = SimpleNamespace(
         task_id="task",
         user_id="user",
+        user_session_id="end-user-session",
         invoke_from="service-api",
         app_config=app_config,
         files=[],