diff --git a/backend/workflow_executor.py b/backend/workflow_executor.py
index dbc398b..ad25033 100644
--- a/backend/workflow_executor.py
+++ b/backend/workflow_executor.py
@@ -816,17 +816,31 @@ def _get_edges_by_label(node_id: str, label: str, graph: WorkflowGraph) -> List[
     """
     Findet alle ausgehenden Edges mit bestimmtem Label.
 
+    Unterstützt beide Formate:
+    - Legacy: e.label == label (z.B. "then", "else")
+    - UI: e.source_handle == label (z.B. "true", "false")
+
     Args:
         node_id: Node-ID
-        label: Edge-Label (z.B. "then", "else", "uncertainty")
+        label: Edge-Label oder sourceHandle (z.B. "then"/"true", "else"/"false")
         graph: WorkflowGraph
 
     Returns:
         Liste von Edge-IDs
     """
+    # Map label to sourceHandle equivalents
+    label_to_handle = {
+        "then": "true",
+        "else": "false"
+    }
+    handle_equivalent = label_to_handle.get(label, label)
+
     matching_edges = [
         e.id for e in graph.edges
-        if e.from_node == node_id and e.label == label
+        if e.from_node == node_id and (
+            e.label == label or  # Legacy format
+            (hasattr(e, 'source_handle') and e.source_handle == handle_equivalent)  # UI format
+        )
     ]
     return matching_edges
 
diff --git a/backend/workflow_models.py b/backend/workflow_models.py
index 0b98ef2..0467285 100644
--- a/backend/workflow_models.py
+++ b/backend/workflow_models.py
@@ -230,6 +230,10 @@ class WorkflowEdge(BaseModel):
     to_node: str = Field(..., alias="to", description="Ziel-Knoten-ID")
     label: Optional[str] = Field(None, description="Label für visuelle Darstellung (z.B. 'then', 'else')")
 
+    # UI-Format fields (React Flow)
+    source_handle: Optional[str] = Field(None, alias="sourceHandle", description="Source handle ID (UI format: 'true', 'false', 'out')")
+    target_handle: Optional[str] = Field(None, alias="targetHandle", description="Target handle ID (UI format: 'in', 'path_1', etc.)")
+
 
 class WorkflowGraph(BaseModel):
     """