diff --git a/api/core/workflow/graph_engine/domain/node_execution.py b/api/core/workflow/graph_engine/domain/node_execution.py
index 937ae0fb93..85700caa3a 100644
--- a/api/core/workflow/graph_engine/domain/node_execution.py
+++ b/api/core/workflow/graph_engine/domain/node_execution.py
@@ -3,7 +3,6 @@ NodeExecution entity representing a node's execution state.
 """
 
 from dataclasses import dataclass
-from typing import Optional
 
 from core.workflow.enums import NodeState
 
@@ -20,8 +19,8 @@ class NodeExecution:
     node_id: str
     state: NodeState = NodeState.UNKNOWN
     retry_count: int = 0
-    execution_id: Optional[str] = None
-    error: Optional[str] = None
+    execution_id: str | None = None
+    error: str | None = None
 
     def mark_started(self, execution_id: str) -> None:
         """Mark the node as started with an execution ID."""
diff --git a/api/core/workflow/graph_engine/entities/commands.py b/api/core/workflow/graph_engine/entities/commands.py
index a92ebf512d..7e25fc0866 100644
--- a/api/core/workflow/graph_engine/entities/commands.py
+++ b/api/core/workflow/graph_engine/entities/commands.py
@@ -6,7 +6,7 @@ instance to control its execution flow.
 """
 
 from enum import Enum
-from typing import Any, Optional
+from typing import Any
 
 from pydantic import BaseModel, Field
 
@@ -23,11 +23,11 @@ class GraphEngineCommand(BaseModel):
     """Base class for all GraphEngine commands."""
 
     command_type: CommandType = Field(..., description="Type of command")
-    payload: Optional[dict[str, Any]] = Field(default=None, description="Optional command payload")
+    payload: dict[str, Any] | None = Field(default=None, description="Optional command payload")
 
 
 class AbortCommand(GraphEngineCommand):
     """Command to abort a running workflow execution."""
 
     command_type: CommandType = Field(default=CommandType.ABORT, description="Type of command")
-    reason: Optional[str] = Field(default=None, description="Optional reason for abort")
+    reason: str | None = Field(default=None, description="Optional reason for abort")
diff --git a/api/core/workflow/graph_engine/graph_engine.py b/api/core/workflow/graph_engine/graph_engine.py
index 6f4f71bfe2..df194de909 100644
--- a/api/core/workflow/graph_engine/graph_engine.py
+++ b/api/core/workflow/graph_engine/graph_engine.py
@@ -9,7 +9,7 @@ import contextvars
 import logging
 import queue
 from collections.abc import Generator, Mapping
-from typing import Any, Optional
+from typing import Any
 
 from flask import Flask, current_app
 
@@ -210,7 +210,7 @@ class GraphEngine:
     def _setup_worker_management(self) -> None:
         """Initialize worker management subsystem."""
         # Capture context for workers
-        flask_app: Optional[Flask] = None
+        flask_app: Flask | None = None
         try:
             flask_app = current_app._get_current_object()  # type: ignore
         except RuntimeError:
diff --git a/api/core/workflow/graph_engine/graph_traversal/branch_handler.py b/api/core/workflow/graph_engine/graph_traversal/branch_handler.py
index 94771a55a4..4bc3bd1e0a 100644
--- a/api/core/workflow/graph_engine/graph_traversal/branch_handler.py
+++ b/api/core/workflow/graph_engine/graph_traversal/branch_handler.py
@@ -3,7 +3,6 @@ Branch node handling for graph traversal.
 """
 
 from collections.abc import Sequence
-from typing import Optional
 
 from core.workflow.graph import Graph
 from core.workflow.graph_events.node import NodeRunStreamChunkEvent
@@ -43,7 +42,7 @@ class BranchHandler:
         self.edge_state_manager = edge_state_manager
 
     def handle_branch_completion(
-        self, node_id: str, selected_handle: Optional[str]
+        self, node_id: str, selected_handle: str | None
     ) -> tuple[Sequence[str], Sequence[NodeRunStreamChunkEvent]]:
         """
         Handle completion of a branch node.
diff --git a/api/core/workflow/graph_engine/layers/base.py b/api/core/workflow/graph_engine/layers/base.py
index df8115c526..febdc3de6d 100644
--- a/api/core/workflow/graph_engine/layers/base.py
+++ b/api/core/workflow/graph_engine/layers/base.py
@@ -6,7 +6,6 @@ intercept and respond to GraphEngine events.
 """
 
 from abc import ABC, abstractmethod
-from typing import Optional
 
 from core.workflow.entities import GraphRuntimeState
 from core.workflow.graph_engine.protocols.command_channel import CommandChannel
@@ -28,8 +27,8 @@ class Layer(ABC):
 
     def __init__(self) -> None:
         """Initialize the layer. Subclasses can override with custom parameters."""
-        self.graph_runtime_state: Optional[GraphRuntimeState] = None
-        self.command_channel: Optional[CommandChannel] = None
+        self.graph_runtime_state: GraphRuntimeState | None = None
+        self.command_channel: CommandChannel | None = None
 
     def initialize(self, graph_runtime_state: GraphRuntimeState, command_channel: CommandChannel) -> None:
         """
@@ -73,7 +72,7 @@ class Layer(ABC):
         pass
 
     @abstractmethod
-    def on_graph_end(self, error: Optional[Exception]) -> None:
+    def on_graph_end(self, error: Exception | None) -> None:
         """
         Called when graph execution ends.
 
diff --git a/api/core/workflow/graph_engine/layers/debug_logging.py b/api/core/workflow/graph_engine/layers/debug_logging.py
index b5222c51d3..73db3260b1 100644
--- a/api/core/workflow/graph_engine/layers/debug_logging.py
+++ b/api/core/workflow/graph_engine/layers/debug_logging.py
@@ -7,7 +7,7 @@ graph execution for debugging purposes.
 
 import logging
 from collections.abc import Mapping
-from typing import Any, Optional
+from typing import Any
 
 from core.workflow.graph_events import (
     GraphEngineEvent,
@@ -221,7 +221,7 @@ class DebugLoggingLayer(Layer):
             # Log unknown events at debug level
             self.logger.debug("Event: %s", event_class)
 
-    def on_graph_end(self, error: Optional[Exception]) -> None:
+    def on_graph_end(self, error: Exception | None) -> None:
         """Log graph execution end with summary statistics."""
         self.logger.info("=" * 80)
 
diff --git a/api/core/workflow/graph_engine/layers/execution_limits.py b/api/core/workflow/graph_engine/layers/execution_limits.py
index 321a7df8c3..71b6e045fd 100644
--- a/api/core/workflow/graph_engine/layers/execution_limits.py
+++ b/api/core/workflow/graph_engine/layers/execution_limits.py
@@ -11,7 +11,6 @@ When limits are exceeded, the layer automatically aborts execution.
 import logging
 import time
 from enum import Enum
-from typing import Optional
 
 from core.workflow.graph_engine.entities.commands import AbortCommand, CommandType
 from core.workflow.graph_engine.layers import Layer
@@ -53,7 +52,7 @@ class ExecutionLimitsLayer(Layer):
         self.max_time = max_time
 
         # Runtime tracking
-        self.start_time: Optional[float] = None
+        self.start_time: float | None = None
         self.step_count = 0
         self.logger = logging.getLogger(__name__)
 
@@ -94,7 +93,7 @@ class ExecutionLimitsLayer(Layer):
             if self._reached_time_limitation():
                 self._send_abort_command(LimitType.TIME_LIMIT)
 
-    def on_graph_end(self, error: Optional[Exception]) -> None:
+    def on_graph_end(self, error: Exception | None) -> None:
         """Called when graph execution ends."""
         if self._execution_started and not self._execution_ended:
             self._execution_ended = True
diff --git a/api/core/workflow/graph_engine/manager.py b/api/core/workflow/graph_engine/manager.py
index a4f9cc7192..131006d1a7 100644
--- a/api/core/workflow/graph_engine/manager.py
+++ b/api/core/workflow/graph_engine/manager.py
@@ -6,7 +6,6 @@ using the new Redis command channel, without requiring user permission checks.
 Supports stop, pause, and resume operations.
 """
 
-from typing import Optional
 
 from core.workflow.graph_engine.command_channels.redis_channel import RedisChannel
 from core.workflow.graph_engine.entities.commands import AbortCommand
@@ -23,7 +22,7 @@ class GraphEngineManager:
     """
 
     @staticmethod
-    def send_stop_command(task_id: str, reason: Optional[str] = None) -> None:
+    def send_stop_command(task_id: str, reason: str | None = None) -> None:
         """
         Send a stop command to a running workflow.
 
diff --git a/api/core/workflow/graph_engine/orchestration/dispatcher.py b/api/core/workflow/graph_engine/orchestration/dispatcher.py
index bee4651def..87ad3d0117 100644
--- a/api/core/workflow/graph_engine/orchestration/dispatcher.py
+++ b/api/core/workflow/graph_engine/orchestration/dispatcher.py
@@ -6,7 +6,7 @@ import logging
 import queue
 import threading
 import time
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING
 
 from core.workflow.graph_events.base import GraphNodeEventBase
 
@@ -34,7 +34,7 @@ class Dispatcher:
         event_collector: EventCollector,
         execution_coordinator: ExecutionCoordinator,
         max_execution_time: int,
-        event_emitter: Optional[EventEmitter] = None,
+        event_emitter: EventEmitter | None = None,
     ) -> None:
         """
         Initialize the dispatcher.
@@ -54,9 +54,9 @@ class Dispatcher:
         self.max_execution_time = max_execution_time
         self.event_emitter = event_emitter
 
-        self._thread: Optional[threading.Thread] = None
+        self._thread: threading.Thread | None = None
         self._stop_event = threading.Event()
-        self._start_time: Optional[float] = None
+        self._start_time: float | None = None
 
     def start(self) -> None:
         """Start the dispatcher thread."""
diff --git a/api/core/workflow/graph_engine/output_registry/registry.py b/api/core/workflow/graph_engine/output_registry/registry.py
index 0f3e690eb1..42ccf51d62 100644
--- a/api/core/workflow/graph_engine/output_registry/registry.py
+++ b/api/core/workflow/graph_engine/output_registry/registry.py
@@ -7,7 +7,7 @@ thread-safe storage for node outputs.
 
 from collections.abc import Sequence
 from threading import RLock
-from typing import TYPE_CHECKING, Optional, Union
+from typing import TYPE_CHECKING, Union
 
 from core.variables import Segment
 from core.workflow.entities.variable_pool import VariablePool
@@ -47,7 +47,7 @@ class OutputRegistry:
         with self._lock:
             self._scalars.add(selector, value)
 
-    def get_scalar(self, selector: Sequence[str]) -> Optional["Segment"]:
+    def get_scalar(self, selector: Sequence[str]) -> "Segment" | None:
         """
         Get a scalar value for the given selector.
 
@@ -81,7 +81,7 @@ class OutputRegistry:
             except ValueError:
                 raise ValueError(f"Stream {'.'.join(selector)} is already closed")
 
-    def pop_chunk(self, selector: Sequence[str]) -> Optional["NodeRunStreamChunkEvent"]:
+    def pop_chunk(self, selector: Sequence[str]) -> "NodeRunStreamChunkEvent" | None:
         """
         Pop the next unread NodeRunStreamChunkEvent from the stream.
 
diff --git a/api/core/workflow/graph_engine/output_registry/stream.py b/api/core/workflow/graph_engine/output_registry/stream.py
index dc12e479a4..1e52d4efaa 100644
--- a/api/core/workflow/graph_engine/output_registry/stream.py
+++ b/api/core/workflow/graph_engine/output_registry/stream.py
@@ -5,7 +5,7 @@ This module contains the private Stream class used internally by OutputRegistry
 to manage streaming data chunks.
 """
 
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
     from core.workflow.graph_events import NodeRunStreamChunkEvent
@@ -41,7 +41,7 @@ class Stream:
             raise ValueError("Cannot append to a closed stream")
         self.events.append(event)
 
-    def pop_next(self) -> Optional["NodeRunStreamChunkEvent"]:
+    def pop_next(self) -> "NodeRunStreamChunkEvent" | None:
         """
         Pop the next unread NodeRunStreamChunkEvent from the stream.
 
diff --git a/api/core/workflow/graph_engine/response_coordinator/coordinator.py b/api/core/workflow/graph_engine/response_coordinator/coordinator.py
index 40c7d19102..380f5de04c 100644
--- a/api/core/workflow/graph_engine/response_coordinator/coordinator.py
+++ b/api/core/workflow/graph_engine/response_coordinator/coordinator.py
@@ -9,7 +9,7 @@ import logging
 from collections import deque
 from collections.abc import Sequence
 from threading import RLock
-from typing import Optional, TypeAlias
+from typing import TypeAlias
 from uuid import uuid4
 
 from core.workflow.enums import NodeExecutionType, NodeState
@@ -45,7 +45,7 @@ class ResponseStreamCoordinator:
         """
         self.registry = registry
         self.graph = graph
-        self.active_session: Optional[ResponseSession] = None
+        self.active_session: ResponseSession | None = None
         self.waiting_sessions: deque[ResponseSession] = deque()
         self.lock = RLock()
 
diff --git a/api/core/workflow/graph_engine/worker.py b/api/core/workflow/graph_engine/worker.py
index bc4025978a..b7eedbc871 100644
--- a/api/core/workflow/graph_engine/worker.py
+++ b/api/core/workflow/graph_engine/worker.py
@@ -11,7 +11,6 @@ import threading
 import time
 from collections.abc import Callable
 from datetime import datetime
-from typing import Optional
 from uuid import uuid4
 
 from flask import Flask
@@ -38,10 +37,10 @@ class Worker(threading.Thread):
         event_queue: queue.Queue[GraphNodeEventBase],
         graph: Graph,
         worker_id: int = 0,
-        flask_app: Optional[Flask] = None,
-        context_vars: Optional[contextvars.Context] = None,
-        on_idle_callback: Optional[Callable[[int], None]] = None,
-        on_active_callback: Optional[Callable[[int], None]] = None,
+        flask_app: Flask | None = None,
+        context_vars: contextvars.Context | None = None,
+        on_idle_callback: Callable[[int], None] | None = None,
+        on_active_callback: Callable[[int], None] | None = None,
     ) -> None:
         """
         Initialize worker thread.
diff --git a/api/core/workflow/graph_engine/worker_management/worker_factory.py b/api/core/workflow/graph_engine/worker_management/worker_factory.py
index 76cfc45b10..8714ee88d1 100644
--- a/api/core/workflow/graph_engine/worker_management/worker_factory.py
+++ b/api/core/workflow/graph_engine/worker_management/worker_factory.py
@@ -5,7 +5,6 @@ Factory for creating worker instances.
 import contextvars
 import queue
 from collections.abc import Callable
-from typing import Optional
 
 from flask import Flask
 
@@ -24,7 +23,7 @@ class WorkerFactory:
 
     def __init__(
         self,
-        flask_app: Optional[Flask],
+        flask_app: Flask | None,
         context_vars: contextvars.Context,
     ) -> None:
         """
@@ -43,8 +42,8 @@ class WorkerFactory:
         ready_queue: queue.Queue[str],
         event_queue: queue.Queue,
         graph: Graph,
-        on_idle_callback: Optional[Callable[[int], None]] = None,
-        on_active_callback: Optional[Callable[[int], None]] = None,
+        on_idle_callback: Callable[[int], None] | None = None,
+        on_active_callback: Callable[[int], None] | None = None,
     ) -> Worker:
         """
         Create a new worker instance.