fix(workflow): lock chatflow start node from type change

web/app/components/workflow-app/hooks/use-available-nodes-meta-data.spec.ts

@@ -102,6 +102,7 @@ describe('workflow-app/useAvailableNodesMetaData', () => {
     expect(nodeTypes).toContain(BlockEnum.TriggerPlugin)
     expect(nodeTypes).not.toContain(BlockEnum.Answer)
     expect(startNode?.metaData.isUndeletable).toBe(false)
+    expect(startNode?.metaData.isTypeFixed).toBe(false)
   })
 
   it('should include chatflow-only nodes when chat mode is enabled', () => {
@@ -117,6 +118,7 @@ describe('workflow-app/useAvailableNodesMetaData', () => {
     expect(nodeTypes).not.toContain(BlockEnum.TriggerSchedule)
     expect(nodeTypes).not.toContain(BlockEnum.TriggerPlugin)
     expect(startNode?.metaData.isUndeletable).toBe(true)
+    expect(startNode?.metaData.isTypeFixed).toBe(true)
   })
 
   it('should hide sandbox-only nodes and keep agent when sandbox is disabled', () => {

web/app/components/workflow-app/hooks/use-available-nodes-meta-data.ts

@@ -57,6 +57,7 @@ export const useAvailableNodesMetaData = () => {
     metaData: {
       ...StartDefault.metaData,
       isUndeletable: isChatMode, // start node is undeletable in chat mode, @use-nodes-interactions: handleNodeDelete function
+      isTypeFixed: isChatMode, // start node (user input) is immutable in chatflow mode
     },
   }), [isChatMode])
 

web/app/components/workflow/hooks/use-nodes-interactions.ts

@@ -63,6 +63,7 @@ import { checkMakeGroupAvailability } from './use-make-group'
 import { useNodesMetaData } from './use-nodes-meta-data'
 import { useNodesSyncDraft } from './use-nodes-sync-draft'
 import {
+  useIsChatMode,
   useNodesReadOnly,
   useWorkflow,
   useWorkflowReadOnly,
@@ -326,6 +327,7 @@ export const useNodesInteractions = () => {
   const { store: workflowHistoryStore } = useWorkflowHistoryStore()
   const { handleSyncWorkflowDraft } = useNodesSyncDraft()
   const { getAfterNodesInSameBranch } = useWorkflow()
+  const isChatMode = useIsChatMode()
   const { getNodesReadOnly } = useNodesReadOnly()
   const { getWorkflowReadOnly } = useWorkflowReadOnly()
   const { handleSetHelpline } = useHelpline()
@@ -1963,7 +1965,14 @@ export const useNodesInteractions = () => {
         return
 
       const { nodes, setNodes, edges, setEdges } = collaborativeWorkflow.getState()
-      const currentNode = nodes.find(node => node.id === currentNodeId)!
+      const currentNode = nodes.find(node => node.id === currentNodeId)
+      if (!currentNode)
+        return
+
+      // In chatflow mode, the Start (user input) node is immutable.
+      if (isChatMode && currentNode.data.type === BlockEnum.Start)
+        return
+
       const connectedEdges = getConnectedEdges([currentNode], edges)
       const nodesWithSameType = nodes.filter(
         node => node.data.type === nodeType,
@@ -2051,6 +2060,7 @@ export const useNodesInteractions = () => {
       })
     },
     [
+      isChatMode,
       getNodesReadOnly,
       collaborativeWorkflow,
       handleSyncWorkflowDraft,