diff --git a/api/app/core/workflow/engine/graph_builder.py b/api/app/core/workflow/engine/graph_builder.py
index 674c45d0..c5cf3324 100644
--- a/api/app/core/workflow/engine/graph_builder.py
+++ b/api/app/core/workflow/engine/graph_builder.py
@@ -390,6 +390,8 @@ class GraphBuilder:
         for edge in self.edges:
             source = edge.get("source")
             target = edge.get("target")
+            if source not in self.reachable_nodes or target not in self.reachable_nodes:
+                continue
             condition = edge.get("condition")
             edge_type = edge.get("type")