diff --git a/web/src/pages/flow/categorize-form/hooks.ts b/web/src/pages/flow/categorize-form/hooks.ts
index 7c6544a087..80df0cf53e 100644
--- a/web/src/pages/flow/categorize-form/hooks.ts
+++ b/web/src/pages/flow/categorize-form/hooks.ts
@@ -78,9 +78,11 @@ const buildCategorizeObjectFromList = (list: Array<ICategorizeItem>) => {
 export const useHandleFormValuesChange = ({
   onValuesChange,
   form,
-  node,
+  nodeId,
 }: IOperatorForm) => {
   const edges = useGraphStore((state) => state.edges);
+  const getNode = useGraphStore((state) => state.getNode);
+  const node = getNode(nodeId);
 
   const handleValuesChange = useCallback(
     (changedValues: any, values: any) => {
@@ -94,12 +96,13 @@ export const useHandleFormValuesChange = ({
   );
 
   useEffect(() => {
+    const items = buildCategorizeListFromObject(
+      get(node, 'data.form.category_description', {}),
+      edges,
+      node,
+    );
     form?.setFieldsValue({
-      items: buildCategorizeListFromObject(
-        get(node, 'data.form.category_description', {}),
-        edges,
-        node,
-      ),
+      items,
     });
   }, [form, node, edges]);
 
@@ -107,19 +110,29 @@ export const useHandleFormValuesChange = ({
 };
 
 export const useHandleToSelectChange = (nodeId?: string) => {
-  const { addEdge } = useGraphStore((state) => state);
+  const { addEdge, deleteEdgeBySourceAndSourceHandle } = useGraphStore(
+    (state) => state,
+  );
   const handleSelectChange = useCallback(
     (name?: string) => (value?: string) => {
-      if (nodeId && value && name) {
-        addEdge({
-          source: nodeId,
-          target: value,
-          sourceHandle: name,
-          targetHandle: null,
-        });
+      if (nodeId && name) {
+        if (value) {
+          addEdge({
+            source: nodeId,
+            target: value,
+            sourceHandle: name,
+            targetHandle: null,
+          });
+        } else {
+          // clear selected value
+          deleteEdgeBySourceAndSourceHandle({
+            source: nodeId,
+            sourceHandle: name,
+          });
+        }
       }
     },
-    [addEdge, nodeId],
+    [addEdge, nodeId, deleteEdgeBySourceAndSourceHandle],
   );
 
   return { handleSelectChange };
diff --git a/web/src/pages/flow/categorize-form/index.tsx b/web/src/pages/flow/categorize-form/index.tsx
index 5f1192a696..de0fc5a359 100644
--- a/web/src/pages/flow/categorize-form/index.tsx
+++ b/web/src/pages/flow/categorize-form/index.tsx
@@ -10,7 +10,7 @@ const CategorizeForm = ({ form, onValuesChange, node }: IOperatorForm) => {
   const { t } = useTranslate('flow');
   const { handleValuesChange } = useHandleFormValuesChange({
     form,
-    node,
+    nodeId: node?.id,
     onValuesChange,
   });
   useSetLlmSetting(form);
diff --git a/web/src/pages/flow/constant.tsx b/web/src/pages/flow/constant.tsx
index cfe8a0ce07..12579bd508 100644
--- a/web/src/pages/flow/constant.tsx
+++ b/web/src/pages/flow/constant.tsx
@@ -101,13 +101,7 @@ export const CategorizeAnchorPointPositions = [
 // key is the source of the edge, value is the target of the edge
 // no connection lines are allowed between key and value
 export const RestrictedUpstreamMap = {
-  [Operator.Begin]: [
-    Operator.Begin,
-    Operator.Answer,
-    Operator.Categorize,
-    Operator.Generate,
-    Operator.Retrieval,
-  ],
+  [Operator.Begin]: [],
   [Operator.Categorize]: [Operator.Begin, Operator.Categorize, Operator.Answer],
   [Operator.Answer]: [],
   [Operator.Retrieval]: [],
diff --git a/web/src/pages/flow/interface.ts b/web/src/pages/flow/interface.ts
index 73eca14d14..55042647e1 100644
--- a/web/src/pages/flow/interface.ts
+++ b/web/src/pages/flow/interface.ts
@@ -10,6 +10,7 @@ export interface IOperatorForm {
   onValuesChange?(changedValues: any, values: any): void;
   form?: FormInstance;
   node?: Node<NodeData>;
+  nodeId?: string;
 }
 
 export interface IBeginForm {
diff --git a/web/src/pages/flow/mock.tsx b/web/src/pages/flow/mock.tsx
index af0129ba5c..0f9a4ad579 100644
--- a/web/src/pages/flow/mock.tsx
+++ b/web/src/pages/flow/mock.tsx
@@ -37,7 +37,7 @@ export const dsl = {
   graph: {
     nodes: [
       {
-        id: 'begin',
+        id: 'Begin',
         type: 'beginNode',
         position: {
           x: 50,
diff --git a/web/src/pages/flow/store.ts b/web/src/pages/flow/store.ts
index 8d2edf0f4b..f20cc31344 100644
--- a/web/src/pages/flow/store.ts
+++ b/web/src/pages/flow/store.ts
@@ -35,7 +35,7 @@ export type RFState = {
   updateNodeForm: (nodeId: string, values: any) => void;
   onSelectionChange: OnSelectionChangeFunc;
   addNode: (nodes: Node) => void;
-  getNode: (id: string) => Node | undefined;
+  getNode: (id?: string) => Node | undefined;
   addEdge: (connection: Connection) => void;
   getEdge: (id: string) => Edge | undefined;
   deletePreviousEdgeOfClassificationNode: (connection: Connection) => void;
@@ -43,7 +43,7 @@ export type RFState = {
   deleteEdge: () => void;
   deleteEdgeById: (id: string) => void;
   deleteNodeById: (id: string) => void;
-  deleteEdgeBySourceAndTarget: (source: string, target: string) => void;
+  deleteEdgeBySourceAndSourceHandle: (connection: Partial<Connection>) => void;
   findNodeByName: (operatorName: Operator) => Node | undefined;
   updateMutableNodeFormItem: (id: string, field: string, value: any) => void;
 };
@@ -87,7 +87,7 @@ const useGraphStore = create<RFState>()(
       addNode: (node: Node) => {
         set({ nodes: get().nodes.concat(node) });
       },
-      getNode: (id: string) => {
+      getNode: (id?: string) => {
         return get().nodes.find((x) => x.id === id);
       },
       addEdge: (connection: Connection) => {
@@ -150,12 +150,17 @@ const useGraphStore = create<RFState>()(
           edges: edges.filter((edge) => edge.id !== id),
         });
       },
-      deleteEdgeBySourceAndTarget: (source: string, target: string) => {
+      deleteEdgeBySourceAndSourceHandle: ({
+        source,
+        sourceHandle,
+      }: Partial<Connection>) => {
         const { edges } = get();
+        const nextEdges = edges.filter(
+          (edge) =>
+            edge.source !== source || edge.sourceHandle !== sourceHandle,
+        );
         set({
-          edges: edges.filter(
-            (edge) => edge.target !== target && edge.source !== source,
-          ),
+          edges: nextEdges,
         });
       },
       deleteNodeById: (id: string) => {
diff --git a/web/src/pages/flow/utils.ts b/web/src/pages/flow/utils.ts
index 404f4d1447..b2a6916168 100644
--- a/web/src/pages/flow/utils.ts
+++ b/web/src/pages/flow/utils.ts
@@ -173,7 +173,8 @@ export const getOperatorTypeFromId = (id: string | null) => {
 
 // restricted lines cannot be connected successfully.
 export const isValidConnection = (connection: Connection) => {
-  return RestrictedUpstreamMap[
+  const ret = RestrictedUpstreamMap[
     getOperatorTypeFromId(connection.source) as Operator
   ]?.every((x) => x !== getOperatorTypeFromId(connection.target));
+  return ret;
 };