diff --git a/web/app/components/app/app-publisher/index.tsx b/web/app/components/app/app-publisher/index.tsx
index 32cd739849..64ce869c5d 100644
--- a/web/app/components/app/app-publisher/index.tsx
+++ b/web/app/components/app/app-publisher/index.tsx
@@ -105,6 +105,7 @@ export type AppPublisherProps = {
   onRefreshData?: () => void
   workflowToolAvailable?: boolean
   missingStartNode?: boolean
+  hasTriggerNode?: boolean // Whether workflow currently contains any trigger nodes (used to hide missing-start CTA when triggers exist).
 }
 
 const PUBLISH_SHORTCUT = ['ctrl', '⇧', 'P']
@@ -125,6 +126,7 @@ const AppPublisher = ({
   onRefreshData,
   workflowToolAvailable = true,
   missingStartNode = false,
+  hasTriggerNode = false,
 }: AppPublisherProps) => {
   const { t } = useTranslation()
 
@@ -350,84 +352,88 @@ const AppPublisher = ({
                   </div>
                   {!isAppAccessSet && <p className='system-xs-regular mt-1 text-text-warning'>{t('app.publishApp.notSetDesc')}</p>}
                 </div>}
-                <div className='flex flex-col gap-y-1 border-t-[0.5px] border-t-divider-regular p-4 pt-3'>
-                  <Tooltip triggerClassName='flex' disabled={!disabledFunctionButton} popupContent={disabledFunctionTooltip} asChild={false}>
-                    <SuggestedAction
-                      className='flex-1'
-                      disabled={disabledFunctionButton}
-                      link={appURL}
-                      icon={<RiPlayCircleLine className='h-4 w-4' />}
-                    >
-                      {t('workflow.common.runApp')}
-                    </SuggestedAction>
-                  </Tooltip>
-                  {appDetail?.mode === AppModeEnum.WORKFLOW || appDetail?.mode === AppModeEnum.COMPLETION
-                    ? (
+                {
+                  // Hide run/batch run app buttons when there is a trigger node.
+                  !hasTriggerNode && (
+                    <div className='flex flex-col gap-y-1 border-t-[0.5px] border-t-divider-regular p-4 pt-3'>
                       <Tooltip triggerClassName='flex' disabled={!disabledFunctionButton} popupContent={disabledFunctionTooltip} asChild={false}>
                         <SuggestedAction
                           className='flex-1'
                           disabled={disabledFunctionButton}
-                          link={`${appURL}${appURL.includes('?') ? '&' : '?'}mode=batch`}
-                          icon={<RiPlayList2Line className='h-4 w-4' />}
+                          link={appURL}
+                          icon={<RiPlayCircleLine className='h-4 w-4' />}
                         >
-                          {t('workflow.common.batchRunApp')}
+                          {t('workflow.common.runApp')}
                         </SuggestedAction>
                       </Tooltip>
-                    )
-                    : (
-                      <SuggestedAction
-                        onClick={() => {
-                          setEmbeddingModalOpen(true)
-                          handleTrigger()
-                        }}
-                        disabled={!publishedAt}
-                        icon={<CodeBrowser className='h-4 w-4' />}
-                      >
-                        {t('workflow.common.embedIntoSite')}
-                      </SuggestedAction>
-                    )}
-                  <Tooltip triggerClassName='flex' disabled={!disabledFunctionButton} popupContent={disabledFunctionTooltip} asChild={false}>
-                    <SuggestedAction
-                      className='flex-1'
-                      onClick={() => {
-                        if (publishedAt)
-                          handleOpenInExplore()
-                      }}
-                      disabled={disabledFunctionButton}
-                      icon={<RiPlanetLine className='h-4 w-4' />}
-                    >
-                      {t('workflow.common.openInExplore')}
-                    </SuggestedAction>
-                  </Tooltip>
-                  <Tooltip triggerClassName='flex' disabled={!!publishedAt && !missingStartNode} popupContent={!publishedAt ? t('app.notPublishedYet') : t('app.noUserInputNode')} asChild={false}>
-                    <SuggestedAction
-                      className='flex-1'
-                      disabled={!publishedAt || missingStartNode}
-                      link='./develop'
-                      icon={<RiTerminalBoxLine className='h-4 w-4' />}
-                    >
-                      {t('workflow.common.accessAPIReference')}
-                    </SuggestedAction>
-                  </Tooltip>
-                  {appDetail?.mode === AppModeEnum.WORKFLOW && (
-                    <WorkflowToolConfigureButton
-                      disabled={workflowToolDisabled}
-                      published={!!toolPublished}
-                      detailNeedUpdate={!!toolPublished && published}
-                      workflowAppId={appDetail?.id}
-                      icon={{
-                        content: (appDetail.icon_type === 'image' ? '🤖' : appDetail?.icon) || '🤖',
-                        background: (appDetail.icon_type === 'image' ? appDefaultIconBackground : appDetail?.icon_background) || appDefaultIconBackground,
-                      }}
-                      name={appDetail?.name}
-                      description={appDetail?.description}
-                      inputs={inputs}
-                      handlePublish={handlePublish}
-                      onRefreshData={onRefreshData}
-                      disabledReason={workflowToolMessage}
-                    />
+                      {appDetail?.mode === AppModeEnum.WORKFLOW || appDetail?.mode === AppModeEnum.COMPLETION
+                        ? (
+                          <Tooltip triggerClassName='flex' disabled={!disabledFunctionButton} popupContent={disabledFunctionTooltip} asChild={false}>
+                            <SuggestedAction
+                              className='flex-1'
+                              disabled={disabledFunctionButton}
+                              link={`${appURL}${appURL.includes('?') ? '&' : '?'}mode=batch`}
+                              icon={<RiPlayList2Line className='h-4 w-4' />}
+                            >
+                              {t('workflow.common.batchRunApp')}
+                            </SuggestedAction>
+                          </Tooltip>
+                        )
+                        : (
+                          <SuggestedAction
+                            onClick={() => {
+                              setEmbeddingModalOpen(true)
+                              handleTrigger()
+                            }}
+                            disabled={!publishedAt}
+                            icon={<CodeBrowser className='h-4 w-4' />}
+                          >
+                            {t('workflow.common.embedIntoSite')}
+                          </SuggestedAction>
+                        )}
+                      <Tooltip triggerClassName='flex' disabled={!disabledFunctionButton} popupContent={disabledFunctionTooltip} asChild={false}>
+                        <SuggestedAction
+                          className='flex-1'
+                          onClick={() => {
+                            if (publishedAt)
+                              handleOpenInExplore()
+                          }}
+                          disabled={disabledFunctionButton}
+                          icon={<RiPlanetLine className='h-4 w-4' />}
+                        >
+                          {t('workflow.common.openInExplore')}
+                        </SuggestedAction>
+                      </Tooltip>
+                      <Tooltip triggerClassName='flex' disabled={!!publishedAt && !missingStartNode} popupContent={!publishedAt ? t('app.notPublishedYet') : t('app.noUserInputNode')} asChild={false}>
+                        <SuggestedAction
+                          className='flex-1'
+                          disabled={!publishedAt || missingStartNode}
+                          link='./develop'
+                          icon={<RiTerminalBoxLine className='h-4 w-4' />}
+                        >
+                          {t('workflow.common.accessAPIReference')}
+                        </SuggestedAction>
+                      </Tooltip>
+                      {appDetail?.mode === AppModeEnum.WORKFLOW && (
+                        <WorkflowToolConfigureButton
+                          disabled={workflowToolDisabled}
+                          published={!!toolPublished}
+                          detailNeedUpdate={!!toolPublished && published}
+                          workflowAppId={appDetail?.id}
+                          icon={{
+                            content: (appDetail.icon_type === 'image' ? '🤖' : appDetail?.icon) || '🤖',
+                            background: (appDetail.icon_type === 'image' ? appDefaultIconBackground : appDetail?.icon_background) || appDefaultIconBackground,
+                          }}
+                          name={appDetail?.name}
+                          description={appDetail?.description}
+                          inputs={inputs}
+                          handlePublish={handlePublish}
+                          onRefreshData={onRefreshData}
+                          disabledReason={workflowToolMessage}
+                        />
+                      )}
+                    </div>
                   )}
-                </div>
               </>}
           </div>
         </PortalToFollowElemContent>
diff --git a/web/app/components/workflow-app/components/workflow-header/features-trigger.tsx b/web/app/components/workflow-app/components/workflow-header/features-trigger.tsx
index 444d2e7b01..c81f9aacbf 100644
--- a/web/app/components/workflow-app/components/workflow-header/features-trigger.tsx
+++ b/web/app/components/workflow-app/components/workflow-header/features-trigger.tsx
@@ -40,6 +40,12 @@ import { useIsChatMode } from '../../hooks'
 import type { StartNodeType } from '@/app/components/workflow/nodes/start/types'
 import type { Node } from '@/app/components/workflow/types'
 
+const TRIGGER_NODE_TYPES: BlockEnum[] = [
+  BlockEnum.TriggerSchedule,
+  BlockEnum.TriggerWebhook,
+  BlockEnum.TriggerPlugin,
+]
+
 const FeaturesTrigger = () => {
   const { t } = useTranslation()
   const { theme } = useTheme()
@@ -89,6 +95,10 @@ const FeaturesTrigger = () => {
       return false
     return edges.some(edge => startNodeIds.includes(edge.source))
   }, [edges, startNodeIds])
+  // Track trigger presence so the publisher can adjust UI (e.g. hide missing start section).
+  const hasTriggerNode = useMemo(() => (
+    nodes.some(node => TRIGGER_NODE_TYPES.includes(node.data.type as BlockEnum))
+  ), [nodes])
 
   const resetWorkflowVersionHistory = useResetWorkflowVersionHistory()
   const invalidateAppTriggers = useInvalidateAppTriggers()
@@ -189,6 +199,7 @@ const FeaturesTrigger = () => {
           workflowToolAvailable: lastPublishedHasUserInput,
           crossAxisOffset: 4,
           missingStartNode: !startNode,
+          hasTriggerNode,
         }}
       />
     </>
diff --git a/web/app/components/workflow/block-selector/all-start-blocks.tsx b/web/app/components/workflow/block-selector/all-start-blocks.tsx
index 892501301e..a089978bdd 100644
--- a/web/app/components/workflow/block-selector/all-start-blocks.tsx
+++ b/web/app/components/workflow/block-selector/all-start-blocks.tsx
@@ -32,6 +32,7 @@ type AllStartBlocksProps = {
   onSelect: (type: BlockEnum, trigger?: TriggerDefaultValue) => void
   availableBlocksTypes?: BlockEnum[]
   tags?: string[]
+  allowUserInputSelection?: boolean // Allow user input option even when trigger node already exists (e.g. when no Start node yet or changing node type).
 }
 
 const AllStartBlocks = ({
@@ -40,6 +41,7 @@ const AllStartBlocks = ({
   onSelect,
   availableBlocksTypes,
   tags = [],
+  allowUserInputSelection = false,
 }: AllStartBlocksProps) => {
   const { t } = useTranslation()
   const [hasStartBlocksContent, setHasStartBlocksContent] = useState(false)
@@ -122,6 +124,7 @@ const AllStartBlocks = ({
               searchText={trimmedSearchText}
               onSelect={onSelect as OnSelectBlock}
               availableBlocksTypes={entryNodeTypes as unknown as BlockEnum[]}
+              hideUserInput={!allowUserInputSelection}
               onContentStateChange={handleStartBlocksContentChange}
             />
 
diff --git a/web/app/components/workflow/block-selector/hooks.ts b/web/app/components/workflow/block-selector/hooks.ts
index d595f8fd09..e2dd14e16c 100644
--- a/web/app/components/workflow/block-selector/hooks.ts
+++ b/web/app/components/workflow/block-selector/hooks.ts
@@ -1,4 +1,6 @@
 import {
+  useCallback,
+  useEffect,
   useMemo,
   useState,
 } from 'react'
@@ -31,16 +33,28 @@ export const useStartBlocks = () => {
   })
 }
 
-export const useTabs = ({ noBlocks, noSources, noTools, noStart = true, defaultActiveTab }: {
+export const useTabs = ({
+  noBlocks,
+  noSources,
+  noTools,
+  noStart = true,
+  defaultActiveTab,
+  hasUserInputNode = false,
+  forceEnableStartTab = false, // When true, Start tab remains enabled even if trigger/user input nodes already exist.
+}: {
   noBlocks?: boolean
   noSources?: boolean
   noTools?: boolean
   noStart?: boolean
   defaultActiveTab?: TabsEnum
+  hasUserInputNode?: boolean
+  forceEnableStartTab?: boolean
 }) => {
   const { t } = useTranslation()
+  const shouldShowStartTab = !noStart
+  const shouldDisableStartTab = !forceEnableStartTab && hasUserInputNode
   const tabs = useMemo(() => {
-    return [{
+    const tabConfigs = [{
       key: TabsEnum.Blocks,
       name: t('workflow.tabs.blocks'),
       show: !noBlocks,
@@ -56,25 +70,54 @@ export const useTabs = ({ noBlocks, noSources, noTools, noStart = true, defaultA
     {
       key: TabsEnum.Start,
       name: t('workflow.tabs.start'),
-      show: !noStart,
-    }].filter(tab => tab.show)
-  }, [t, noBlocks, noSources, noTools, noStart])
+      show: shouldShowStartTab,
+      disabled: shouldDisableStartTab,
+    }]
+
+    return tabConfigs.filter(tab => tab.show)
+  }, [t, noBlocks, noSources, noTools, shouldShowStartTab, shouldDisableStartTab])
+
+  const getValidTabKey = useCallback((targetKey?: TabsEnum) => {
+    if (!targetKey)
+      return undefined
+    const tab = tabs.find(tabItem => tabItem.key === targetKey)
+    if (!tab || tab.disabled)
+      return undefined
+    return tab.key
+  }, [tabs])
 
   const initialTab = useMemo(() => {
-    // If a default tab is specified, use it
-    if (defaultActiveTab)
-      return defaultActiveTab
+    const fallbackTab = tabs.find(tab => !tab.disabled)?.key ?? TabsEnum.Blocks
+    const preferredDefault = getValidTabKey(defaultActiveTab)
+    if (preferredDefault)
+      return preferredDefault
 
-    if (noBlocks)
-      return noTools ? TabsEnum.Sources : TabsEnum.Tools
+    const preferredOrder: TabsEnum[] = []
+    if (!noBlocks)
+      preferredOrder.push(TabsEnum.Blocks)
+    if (!noTools)
+      preferredOrder.push(TabsEnum.Tools)
+    if (!noSources)
+      preferredOrder.push(TabsEnum.Sources)
+    if (!noStart)
+      preferredOrder.push(TabsEnum.Start)
 
-    if (noTools)
-      return noBlocks ? TabsEnum.Sources : TabsEnum.Blocks
+    for (const tabKey of preferredOrder) {
+      const validKey = getValidTabKey(tabKey)
+      if (validKey)
+        return validKey
+    }
 
-    return TabsEnum.Blocks
-  }, [noBlocks, noSources, noTools, defaultActiveTab])
+    return fallbackTab
+  }, [defaultActiveTab, noBlocks, noSources, noTools, noStart, tabs, getValidTabKey])
   const [activeTab, setActiveTab] = useState(initialTab)
 
+  useEffect(() => {
+    const currentTab = tabs.find(tab => tab.key === activeTab)
+    if (!currentTab || currentTab.disabled)
+      setActiveTab(initialTab)
+  }, [tabs, activeTab, initialTab])
+
   return {
     tabs,
     activeTab,
diff --git a/web/app/components/workflow/block-selector/main.tsx b/web/app/components/workflow/block-selector/main.tsx
index 661c2072a0..5f8480d9f5 100644
--- a/web/app/components/workflow/block-selector/main.tsx
+++ b/web/app/components/workflow/block-selector/main.tsx
@@ -9,16 +9,18 @@ import {
   useState,
 } from 'react'
 import { useTranslation } from 'react-i18next'
+import { useNodes } from 'reactflow'
 import type {
   OffsetOptions,
   Placement,
 } from '@floating-ui/react'
 import type {
-  BlockEnum,
+  CommonNodeType,
   NodeDefault,
   OnSelectBlock,
   ToolWithProvider,
 } from '../types'
+import { BlockEnum } from '../types'
 import Tabs from './tabs'
 import { TabsEnum } from './types'
 import { useTabs } from './hooks'
@@ -33,6 +35,12 @@ import {
 } from '@/app/components/base/icons/src/vender/line/general'
 import SearchBox from '@/app/components/plugins/marketplace/search-box'
 
+const TRIGGER_NODE_TYPES: BlockEnum[] = [
+  BlockEnum.TriggerSchedule,
+  BlockEnum.TriggerWebhook,
+  BlockEnum.TriggerPlugin,
+]
+
 export type NodeSelectorProps = {
   open?: boolean
   onOpenChange?: (open: boolean) => void
@@ -54,6 +62,9 @@ export type NodeSelectorProps = {
   showStartTab?: boolean
   defaultActiveTab?: TabsEnum
   forceShowStartContent?: boolean
+  ignoreNodeIds?: string[]
+  forceEnableStartTab?: boolean // Force enabling Start tab regardless of existing trigger/user input nodes (e.g., when changing Start node type).
+  allowUserInputSelection?: boolean // Override user-input availability; default logic blocks it when triggers exist.
 }
 const NodeSelector: FC<NodeSelectorProps> = ({
   open: openFromProps,
@@ -76,11 +87,44 @@ const NodeSelector: FC<NodeSelectorProps> = ({
   showStartTab = false,
   defaultActiveTab,
   forceShowStartContent = false,
+  ignoreNodeIds = [],
+  forceEnableStartTab = false,
+  allowUserInputSelection,
 }) => {
   const { t } = useTranslation()
+  const nodes = useNodes()
   const [searchText, setSearchText] = useState('')
   const [tags, setTags] = useState<string[]>([])
   const [localOpen, setLocalOpen] = useState(false)
+  // Exclude nodes explicitly ignored (such as the node currently being edited) when checking canvas state.
+  const filteredNodes = useMemo(() => {
+    if (!ignoreNodeIds.length)
+      return nodes
+    const ignoreSet = new Set(ignoreNodeIds)
+    return nodes.filter(node => !ignoreSet.has(node.id))
+  }, [nodes, ignoreNodeIds])
+
+  const { hasTriggerNode, hasUserInputNode } = useMemo(() => {
+    const result = {
+      hasTriggerNode: false,
+      hasUserInputNode: false,
+    }
+    for (const node of filteredNodes) {
+      const nodeType = (node.data as CommonNodeType | undefined)?.type
+      if (!nodeType)
+        continue
+      if (nodeType === BlockEnum.Start)
+        result.hasUserInputNode = true
+      if (TRIGGER_NODE_TYPES.includes(nodeType))
+        result.hasTriggerNode = true
+      if (result.hasTriggerNode && result.hasUserInputNode)
+        break
+    }
+    return result
+  }, [filteredNodes])
+  // Default rule: user input option is only available when no Start node nor Trigger node exists on canvas.
+  const defaultAllowUserInputSelection = !hasUserInputNode && !hasTriggerNode
+  const canSelectUserInput = allowUserInputSelection ?? defaultAllowUserInputSelection
   const open = openFromProps === undefined ? localOpen : openFromProps
   const handleOpenChange = useCallback((newOpen: boolean) => {
     setLocalOpen(newOpen)
@@ -107,7 +151,15 @@ const NodeSelector: FC<NodeSelectorProps> = ({
     activeTab,
     setActiveTab,
     tabs,
-  } = useTabs({ noBlocks, noSources: !dataSources.length, noTools, noStart: !showStartTab, defaultActiveTab })
+  } = useTabs({
+    noBlocks,
+    noSources: !dataSources.length,
+    noTools,
+    noStart: !showStartTab,
+    defaultActiveTab,
+    hasUserInputNode,
+    forceEnableStartTab,
+  })
 
   const handleActiveTabChange = useCallback((newActiveTab: TabsEnum) => {
     setActiveTab(newActiveTab)
@@ -146,7 +198,7 @@ const NodeSelector: FC<NodeSelectorProps> = ({
             : (
               <div
                 className={`
-                  z-10 flex h-4 
+                  z-10 flex h-4
                   w-4 cursor-pointer items-center justify-center rounded-full bg-components-button-primary-bg text-text-primary-on-surface hover:bg-components-button-primary-bg-hover
                   ${triggerClassName?.(open)}
                 `}
@@ -163,6 +215,7 @@ const NodeSelector: FC<NodeSelectorProps> = ({
             tabs={tabs}
             activeTab={activeTab}
             blocks={blocks}
+            allowStartNodeSelection={canSelectUserInput}
             onActiveTabChange={handleActiveTabChange}
             filterElem={
               <div className='relative m-2' onClick={e => e.stopPropagation()}>
diff --git a/web/app/components/workflow/block-selector/start-blocks.tsx b/web/app/components/workflow/block-selector/start-blocks.tsx
index 4fdfd475d9..31b6abce6c 100644
--- a/web/app/components/workflow/block-selector/start-blocks.tsx
+++ b/web/app/components/workflow/block-selector/start-blocks.tsx
@@ -20,6 +20,7 @@ type StartBlocksProps = {
   onSelect: (type: BlockEnum, triggerDefaultValue?: TriggerDefaultValue) => void
   availableBlocksTypes?: BlockEnum[]
   onContentStateChange?: (hasContent: boolean) => void
+  hideUserInput?: boolean
 }
 
 const StartBlocks = ({
@@ -27,6 +28,7 @@ const StartBlocks = ({
   onSelect,
   availableBlocksTypes = [],
   onContentStateChange,
+  hideUserInput = false, // Allow parent to explicitly hide Start node option (e.g. when one already exists).
 }: StartBlocksProps) => {
   const { t } = useTranslation()
   const nodes = useNodes()
@@ -45,8 +47,8 @@ const StartBlocks = ({
     }
 
     return START_BLOCKS.filter((block) => {
-      // Hide User Input (Start) if it already exists in workflow
-      if (block.type === BlockEnumValues.Start && hasStartNode)
+      // Hide User Input (Start) if it already exists in workflow or if hideUserInput is true
+      if (block.type === BlockEnumValues.Start && (hasStartNode || hideUserInput))
         return false
 
       // Filter by search text
@@ -57,7 +59,7 @@ const StartBlocks = ({
       // availableBlocksTypes now contains properly filtered entry node types from parent
       return availableBlocksTypes.includes(block.type)
     })
-  }, [searchText, availableBlocksTypes, nodes, t])
+  }, [searchText, availableBlocksTypes, nodes, t, hideUserInput])
 
   const isEmpty = filteredBlocks.length === 0
 
diff --git a/web/app/components/workflow/block-selector/tabs.tsx b/web/app/components/workflow/block-selector/tabs.tsx
index a1b2839b45..ecdb8797c0 100644
--- a/web/app/components/workflow/block-selector/tabs.tsx
+++ b/web/app/components/workflow/block-selector/tabs.tsx
@@ -1,5 +1,6 @@
 import type { Dispatch, FC, SetStateAction } from 'react'
 import { memo, useEffect, useMemo } from 'react'
+import { useTranslation } from 'react-i18next'
 import { useAllBuiltInTools, useAllCustomTools, useAllMCPTools, useAllWorkflowTools, useInvalidateAllBuiltInTools } from '@/service/use-tools'
 import type {
   BlockEnum,
@@ -17,6 +18,7 @@ import { useFeaturedToolsRecommendations } from '@/service/use-plugins'
 import { useGlobalPublicStore } from '@/context/global-public-context'
 import { useWorkflowStore } from '../store'
 import { basePath } from '@/utils/var'
+import Tooltip from '@/app/components/base/tooltip'
 
 export type TabsProps = {
   activeTab: TabsEnum
@@ -31,11 +33,13 @@ export type TabsProps = {
   tabs: Array<{
     key: TabsEnum
     name: string
+    disabled?: boolean
   }>
   filterElem: React.ReactNode
   noBlocks?: boolean
   noTools?: boolean
   forceShowStartContent?: boolean // Force show Start content even when noBlocks=true
+  allowStartNodeSelection?: boolean // Allow user input option even when trigger node already exists (e.g. change-node flow or when no Start node yet).
 }
 const Tabs: FC<TabsProps> = ({
   activeTab,
@@ -52,7 +56,9 @@ const Tabs: FC<TabsProps> = ({
   noBlocks,
   noTools,
   forceShowStartContent = false,
+  allowStartNodeSelection = false,
 }) => {
+  const { t } = useTranslation()
   const { data: buildInTools } = useAllBuiltInTools()
   const { data: customTools } = useAllCustomTools()
   const { data: workflowTools } = useAllWorkflowTools()
@@ -125,20 +131,46 @@ const Tabs: FC<TabsProps> = ({
         !noBlocks && (
           <div className='relative flex bg-background-section-burn pl-1 pt-1'>
             {
-              tabs.map(tab => (
-                <div
-                  key={tab.key}
-                  className={cn(
-                    'system-sm-medium relative mr-0.5 flex h-8 cursor-pointer  items-center rounded-t-lg px-3 ',
-                    activeTab === tab.key
-                      ? 'sm-no-bottom cursor-default bg-components-panel-bg text-text-accent'
-                      : 'text-text-tertiary',
-                  )}
-                  onClick={() => onActiveTabChange(tab.key)}
-                >
-                  {tab.name}
-                </div>
-              ))
+              tabs.map((tab) => {
+                const commonProps = {
+                  'className': cn(
+                    'system-sm-medium relative mr-0.5 flex h-8 items-center rounded-t-lg px-3',
+                    tab.disabled
+                      ? 'cursor-not-allowed text-text-disabled opacity-60'
+                      : activeTab === tab.key
+                        ? 'sm-no-bottom cursor-default bg-components-panel-bg text-text-accent'
+                        : 'cursor-pointer text-text-tertiary',
+                  ),
+                  'aria-disabled': tab.disabled,
+                  'onClick': () => {
+                    if (tab.disabled || activeTab === tab.key)
+                      return
+                    onActiveTabChange(tab.key)
+                  },
+                } as const
+                if (tab.disabled) {
+                  return (
+                    <Tooltip
+                      key={tab.key}
+                      position='top'
+                      popupClassName='max-w-[200px]'
+                      popupContent={t('workflow.tabs.startDisabledTip')}
+                    >
+                      <div {...commonProps}>
+                        {tab.name}
+                      </div>
+                    </Tooltip>
+                  )
+                }
+                return (
+                  <div
+                    key={tab.key}
+                    {...commonProps}
+                  >
+                    {tab.name}
+                  </div>
+                )
+              })
             }
           </div>
         )
@@ -148,6 +180,7 @@ const Tabs: FC<TabsProps> = ({
         activeTab === TabsEnum.Start && (!noBlocks || forceShowStartContent) && (
           <div className='border-t border-divider-subtle'>
             <AllStartBlocks
+              allowUserInputSelection={allowStartNodeSelection}
               searchText={searchText}
               onSelect={onSelect}
               availableBlocksTypes={availableBlocksTypes}
diff --git a/web/app/components/workflow/nodes/_base/components/panel-operator/change-block.tsx b/web/app/components/workflow/nodes/_base/components/panel-operator/change-block.tsx
index 4a6bb824ff..86c346f2ab 100644
--- a/web/app/components/workflow/nodes/_base/components/panel-operator/change-block.tsx
+++ b/web/app/components/workflow/nodes/_base/components/panel-operator/change-block.tsx
@@ -5,6 +5,7 @@ import {
 } from 'react'
 import { useTranslation } from 'react-i18next'
 import { intersection } from 'lodash-es'
+import { useNodes } from 'reactflow'
 import BlockSelector from '@/app/components/workflow/block-selector'
 import {
   useAvailableBlocks,
@@ -13,9 +14,17 @@ import {
 } from '@/app/components/workflow/hooks'
 import { useHooksStore } from '@/app/components/workflow/hooks-store'
 import type {
+  CommonNodeType,
   Node,
   OnSelectBlock,
 } from '@/app/components/workflow/types'
+import { BlockEnum } from '@/app/components/workflow/types'
+
+const TRIGGER_NODE_TYPES: BlockEnum[] = [
+  BlockEnum.TriggerSchedule,
+  BlockEnum.TriggerWebhook,
+  BlockEnum.TriggerPlugin,
+]
 import { FlowType } from '@/types/common'
 
 type ChangeBlockProps = {
@@ -30,6 +39,7 @@ const ChangeBlock = ({
 }: ChangeBlockProps) => {
   const { t } = useTranslation()
   const { handleNodeChange } = useNodesInteractions()
+  const nodes = useNodes<CommonNodeType>()
   const {
     availablePrevBlocks,
     availableNextBlocks,
@@ -37,6 +47,30 @@ const ChangeBlock = ({
   const isChatMode = useIsChatMode()
   const flowType = useHooksStore(s => s.configsMap?.flowType)
   const showStartTab = flowType !== FlowType.ragPipeline && !isChatMode
+  // Count total trigger nodes
+  const totalTriggerNodes = useMemo(() => (
+    nodes.filter(node => TRIGGER_NODE_TYPES.includes(node.data.type as BlockEnum)).length
+  ), [nodes])
+  // Check if there is a User Input node
+  const hasUserInputNode = useMemo(() => (
+    nodes.some(node => node.data.type === BlockEnum.Start)
+  ), [nodes])
+  // Check if the current node is a trigger node
+  const isTriggerNode = TRIGGER_NODE_TYPES.includes(nodeData.type as BlockEnum)
+  // Force enabling Start tab regardless of existing trigger/user input nodes (e.g., when changing Start node type).
+  const forceEnableStartTab = isTriggerNode || nodeData.type === BlockEnum.Start
+  // Only allow converting a trigger into User Input when it's the sole trigger and no User Input exists yet.
+  const canChangeTriggerToUserInput = isTriggerNode && !hasUserInputNode && totalTriggerNodes === 1
+  // Ignore current node when it's a trigger so the Start tab logic doesn't treat it as existing trigger.
+  const ignoreNodeIds = useMemo(() => {
+    if (TRIGGER_NODE_TYPES.includes(nodeData.type as BlockEnum))
+      return [nodeId]
+    return undefined
+  }, [nodeData.type, nodeId])
+  // Determine user input selection based on node type and trigger/user input node presence.
+  const allowUserInputSelection = forceEnableStartTab
+    ? (nodeData.type === BlockEnum.Start ? false : canChangeTriggerToUserInput)
+    : undefined
 
   const availableNodes = useMemo(() => {
     if (availablePrevBlocks.length && availableNextBlocks.length)
@@ -71,6 +105,10 @@ const ChangeBlock = ({
       popupClassName='min-w-[240px]'
       availableBlocksTypes={availableNodes}
       showStartTab={showStartTab}
+      ignoreNodeIds={ignoreNodeIds}
+      // When changing Start/Trigger nodes, force-enable Start tab to allow switching among entry nodes.
+      forceEnableStartTab={forceEnableStartTab}
+      allowUserInputSelection={allowUserInputSelection}
     />
   )
 }
diff --git a/web/app/components/workflow/nodes/start/default.ts b/web/app/components/workflow/nodes/start/default.ts
index 9780549c5a..60584b5144 100644
--- a/web/app/components/workflow/nodes/start/default.ts
+++ b/web/app/components/workflow/nodes/start/default.ts
@@ -9,7 +9,7 @@ const metaData = genNodeMetaData({
   isStart: true,
   isRequired: false,
   isSingleton: true,
-  isTypeFixed: true,
+  isTypeFixed: false, // support node type change for start node(user input)
   helpLinkUri: 'user-input',
 })
 const nodeDefault: NodeDefault<StartNodeType> = {
diff --git a/web/i18n/en-US/workflow.ts b/web/i18n/en-US/workflow.ts
index 77e71b0973..92a0b110c7 100644
--- a/web/i18n/en-US/workflow.ts
+++ b/web/i18n/en-US/workflow.ts
@@ -287,6 +287,7 @@ const translation = {
     'hideActions': 'Hide tools',
     'noFeaturedPlugins': 'Discover more tools in Marketplace',
     'noFeaturedTriggers': 'Discover more triggers in Marketplace',
+    'startDisabledTip': 'Trigger node and user input node are mutually exclusive.',
   },
   blocks: {
     'start': 'User Input',
diff --git a/web/i18n/ja-JP/workflow.ts b/web/i18n/ja-JP/workflow.ts
index d55f12fc8b..07241b8c4f 100644
--- a/web/i18n/ja-JP/workflow.ts
+++ b/web/i18n/ja-JP/workflow.ts
@@ -276,6 +276,7 @@ const translation = {
     'searchDataSource': 'データソースを検索',
     'sources': 'ソース',
     'start': '始める',
+    'startDisabledTip': 'トリガーノードとユーザー入力ノードは互いに排他です。',
   },
   blocks: {
     'start': 'ユーザー入力',
diff --git a/web/i18n/zh-Hans/workflow.ts b/web/i18n/zh-Hans/workflow.ts
index 53ec625160..18e76caa64 100644
--- a/web/i18n/zh-Hans/workflow.ts
+++ b/web/i18n/zh-Hans/workflow.ts
@@ -286,6 +286,7 @@ const translation = {
     'hideActions': '收起工具',
     'noFeaturedPlugins': '前往插件市场查看更多工具',
     'noFeaturedTriggers': '前往插件市场查看更多触发器',
+    'startDisabledTip': '触发节点与用户输入节点互斥。',
   },
   blocks: {
     'start': '用户输入',