fix(workflow): sanitize condition expression building and cache assigner node inputs

- Sanitize condition expression construction in graph_builder.py using json.dumps to prevent potential injection vulnerabilities.
- Cache input data prior to assigner node execution to ensure variable values are correctly captured before processing.

api/app/core/workflow/engine/graph_builder.py

@@ -2,6 +2,7 @@
 # Author: Eternity
 # @Email: 1533512157@qq.com
 # @Time : 2026/2/10 13:33
+import json
 import logging
 import re
 import uuid
@@ -318,7 +319,9 @@ class GraphBuilder:
                     # For LLM nodes, use branch_signal field for routing (output is dynamic text)
                     # For other branch nodes (e.g. HTTP), use output field
                     route_field = "branch_signal" if node_type == NodeType.LLM else "output"
-                    related_edge[idx]['condition'] = f"node['{node_id}']['{route_field}'] == '{related_edge[idx]['label']}'"
+                    related_edge[idx]['condition'] = (
+                        f"node[{json.dumps(node_id)}][{json.dumps(route_field)}] == {json.dumps(related_edge[idx]['label'])}"
+                    )
 
             if node_instance:
                 # Wrap node's run method to avoid closure issues

api/app/core/workflow/nodes/assigner/node.py

@@ -18,10 +18,17 @@ class AssignerNode(BaseNode):
         super().__init__(node_config, workflow_config, down_stream_nodes)
         self.variable_updater = True
         self.typed_config: AssignerNodeConfig | None = None
+        self._input_data: dict[str, Any] | None = None
 
     def _output_types(self) -> dict[str, VariableType]:
         return {}
 
+    def _extract_input(self, state: WorkflowState, variable_pool: VariablePool) -> dict[str, Any]:
+        """提取节点输入，如果有缓存的执行前数据则使用缓存"""
+        if self._input_data is not None:
+            return self._input_data
+        return {"config": self._resolve_config(self.config, variable_pool)}
+
     async def execute(self, state: WorkflowState, variable_pool: VariablePool) -> Any:
         """
         Execute the assignment operation defined by this node.
@@ -34,6 +41,9 @@ class AssignerNode(BaseNode):
         Returns:
             None or the result of the assignment operation.
         """
+        # 在执行前提取并缓存输入数据（捕获执行前的变量值）
+        self._input_data = {"config": self._resolve_config(self.config, variable_pool)}
+        
         # Initialize a variable pool for accessing conversation, node, and system variables
         self.typed_config = AssignerNodeConfig(**self.config)
         logger.info(f"节点 {self.node_id} 开始执行")