diff --git a/api/core/workflow/graph_engine/command_source.py b/api/core/workflow/graph_engine/command_source.py
index 1cafcf20f9..2d0d4b8211 100644
--- a/api/core/workflow/graph_engine/command_source.py
+++ b/api/core/workflow/graph_engine/command_source.py
@@ -21,7 +21,9 @@ class _CommandTag(StrEnum):
     CONTINUE = "continue"
 
 
-class Command(BaseModel, abc.ABC):
+# Note: Avoid using the `_Command` class directly.
+# Instead, use `CommandTypes` for type annotations.
+class _Command(BaseModel, abc.ABC):
     model_config = ConfigDict(frozen=True)
 
     tag: _CommandTag
@@ -35,21 +37,21 @@ class Command(BaseModel, abc.ABC):
 
 
 @final
-class StopCommand(Command):
+class StopCommand(_Command):
     tag: _CommandTag = _CommandTag.STOP
 
 
 @final
-class SuspendCommand(Command):
+class SuspendCommand(_Command):
     tag: _CommandTag = _CommandTag.SUSPEND
 
 
 @final
-class ContinueCommand(Command):
+class ContinueCommand(_Command):
     tag: _CommandTag = _CommandTag.CONTINUE
 
 
-def _get_command_tag(command: Command):
+def _get_command_tag(command: _Command):
     return command.tag
 
 
diff --git a/api/core/workflow/graph_engine/graph_engine.py b/api/core/workflow/graph_engine/graph_engine.py
index b89aee7712..d930b6a923 100644
--- a/api/core/workflow/graph_engine/graph_engine.py
+++ b/api/core/workflow/graph_engine/graph_engine.py
@@ -57,7 +57,14 @@ from core.workflow.utils import variable_utils
 from libs.flask_utils import preserve_flask_contexts
 from models.workflow import WorkflowType
 
-from .command_source import Command, CommandParams, CommandSource, ContinueCommand, StopCommand, SuspendCommand
+from .command_source import (
+    CommandParams,
+    CommandSource,
+    CommandTypes,
+    ContinueCommand,
+    StopCommand,
+    SuspendCommand,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -89,7 +96,7 @@ class GraphEngineThreadPool(ThreadPoolExecutor):
             raise ValueError(f"Max submit count {self.max_submit_count} of workflow thread pool reached.")
 
 
-def _default_source(params: CommandParams) -> Command:
+def _default_source(_: CommandParams) -> CommandTypes:
     return ContinueCommand()