diff --git a/api/app/core/workflow/engine/graph_builder.py b/api/app/core/workflow/engine/graph_builder.py
index 8c1a799c..5ecf41d2 100644
--- a/api/app/core/workflow/engine/graph_builder.py
+++ b/api/app/core/workflow/engine/graph_builder.py
@@ -21,6 +21,7 @@ from app.core.workflow.nodes import NodeFactory
 from app.core.workflow.nodes.enums import NodeType, BRANCH_NODES
 from app.core.workflow.utils.expression_evaluator import evaluate_condition
 from app.core.workflow.validator import WorkflowValidator
+from app.core.workflow.variable.base_variable import VariableType
 
 logger = logging.getLogger(__name__)
 
@@ -194,7 +195,7 @@ class GraphBuilder:
                 outputs_list = config.get("outputs", [])
                 output = "\n".join(
                     item.get("value", "") for item in outputs_list
-                    if item.get("value") and item.get("type", "string") == "string"
+                    if item.get("value") and item.get("type", VariableType.STRING) == VariableType.STRING
                 ) or None
             else:
                 output = config.get("output")
diff --git a/api/app/core/workflow/validator.py b/api/app/core/workflow/validator.py
index 36a90be6..962291d4 100644
--- a/api/app/core/workflow/validator.py
+++ b/api/app/core/workflow/validator.py
@@ -135,7 +135,7 @@ class WorkflowValidator:
                 # 2. 验证 主图end 节点（至少一个，output 节点也可作为终止节点）
                 end_nodes = [n for n in nodes if n.get("type") in [NodeType.END, NodeType.OUTPUT]]
                 if len(end_nodes) == 0:
-                    errors.append("工作流必须至少有一个 end 节点 或 output节点")
+                    errors.append("工作流必须至少有一个 end 节点 或 output 节点")
 
             # 3. 验证节点 ID 唯一性
             node_ids = [n.get("id") for n in nodes if n.get("type") != NodeType.NOTES]