fix(templates-page): loading issue due to loading extensive workflow block in preview for all listings

apps/sim/app/templates/components/template-card.tsx

@@ -210,6 +210,7 @@ function TemplateCardInner({
             isPannable={false}
             defaultZoom={0.8}
             fitPadding={0.2}
+            lightweight
           />
         ) : (
           <div className='h-full w-full bg-[#2A2A2A]' />

apps/sim/app/workspace/[workspaceId]/templates/components/template-card.tsx

@@ -211,6 +211,7 @@ function TemplateCardInner({
             isPannable={false}
             defaultZoom={0.8}
             fitPadding={0.2}
+            lightweight
           />
         ) : (
           <div className='h-full w-full bg-[#2A2A2A]' />

apps/sim/app/workspace/[workspaceId]/w/components/workflow-preview/workflow-preview-block.tsx

@@ -0,0 +1,118 @@
+'use client'
+
+import { memo, useMemo } from 'react'
+import { Handle, type NodeProps, Position } from 'reactflow'
+import { getBlock } from '@/blocks/registry'
+
+interface WorkflowPreviewBlockData {
+  type: string
+  name: string
+  isTrigger?: boolean
+}
+
+/**
+ * Lightweight block component for workflow previews.
+ * Renders block header, dummy subblocks skeleton, and horizontal handles.
+ * No hooks, store subscriptions, or interactive features.
+ * Used in template cards and other preview contexts for performance.
+ */
+function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>) {
+  const { type, name, isTrigger = false } = data
+
+  const blockConfig = getBlock(type)
+  if (!blockConfig) {
+    return null
+  }
+
+  const IconComponent = blockConfig.icon
+  // Hide input handle for triggers, starters, or blocks in trigger mode
+  const isStarterOrTrigger = blockConfig.category === 'triggers' || type === 'starter' || isTrigger
+
+  // Get visible subblocks from config (no fetching, just config structure)
+  const visibleSubBlocks = useMemo(() => {
+    if (!blockConfig.subBlocks) return []
+
+    return blockConfig.subBlocks.filter((subBlock) => {
+      if (subBlock.hidden) return false
+      if (subBlock.hideFromPreview) return false
+      if (subBlock.mode === 'trigger') return false
+      if (subBlock.mode === 'advanced') return false
+      return true
+    })
+  }, [blockConfig.subBlocks])
+
+  const hasSubBlocks = visibleSubBlocks.length > 0
+  const showErrorRow = !isStarterOrTrigger
+
+  // Handle styles - always horizontal
+  const handleClass = '!border-none !bg-[var(--surface-12)] !h-5 !w-[7px] !rounded-[2px]'
+
+  return (
+    <div className='relative w-[250px] select-none rounded-[8px] border border-[var(--border)] bg-[var(--surface-2)]'>
+      {/* Target handle - not shown for triggers/starters */}
+      {!isStarterOrTrigger && (
+        <Handle
+          type='target'
+          position={Position.Left}
+          id='target'
+          className={handleClass}
+          style={{ left: '-7px', top: '24px' }}
+        />
+      )}
+
+      {/* Header */}
+      <div
+        className={`flex items-center gap-[10px] p-[8px] ${hasSubBlocks || showErrorRow ? 'border-[var(--divider)] border-b' : ''}`}
+      >
+        <div
+          className='flex h-[24px] w-[24px] flex-shrink-0 items-center justify-center rounded-[6px]'
+          style={{ background: blockConfig.bgColor }}
+        >
+          <IconComponent className='h-[16px] w-[16px] text-white' />
+        </div>
+        <span className='truncate font-medium text-[16px]' title={name}>
+          {name}
+        </span>
+      </div>
+
+      {/* Subblocks skeleton */}
+      {(hasSubBlocks || showErrorRow) && (
+        <div className='flex flex-col gap-[8px] p-[8px]'>
+          {visibleSubBlocks.slice(0, 4).map((subBlock) => (
+            <div key={subBlock.id} className='flex items-center gap-[8px]'>
+              <span className='min-w-0 truncate text-[14px] text-[var(--text-tertiary)] capitalize'>
+                {subBlock.title ?? subBlock.id}
+              </span>
+              <span className='flex-1 truncate text-right text-[14px] text-[var(--white)]'>-</span>
+            </div>
+          ))}
+          {visibleSubBlocks.length > 4 && (
+            <div className='flex items-center gap-[8px]'>
+              <span className='text-[14px] text-[var(--text-tertiary)]'>
+                +{visibleSubBlocks.length - 4} more
+              </span>
+            </div>
+          )}
+          {showErrorRow && (
+            <div className='flex items-center gap-[8px]'>
+              <span className='min-w-0 truncate text-[14px] text-[var(--text-tertiary)] capitalize'>
+                error
+              </span>
+            </div>
+          )}
+        </div>
+      )}
+
+      {/* Source handle */}
+      <Handle
+        type='source'
+        position={Position.Right}
+        id='source'
+        className={handleClass}
+        style={{ right: '-7px', top: '24px' }}
+      />
+    </div>
+  )
+}
+
+export const WorkflowPreviewBlock = memo(WorkflowPreviewBlockInner)

apps/sim/app/workspace/[workspaceId]/w/components/workflow-preview/workflow-preview-subflow.tsx

@@ -0,0 +1,90 @@
+'use client'
+
+import { memo } from 'react'
+import { RepeatIcon, SplitIcon } from 'lucide-react'
+import { Handle, type NodeProps, Position } from 'reactflow'
+
+interface WorkflowPreviewSubflowData {
+  name: string
+  width?: number
+  height?: number
+  kind: 'loop' | 'parallel'
+}
+
+/**
+ * Lightweight subflow component for workflow previews.
+ * Matches the styling of the actual SubflowNodeComponent but without
+ * hooks, store subscriptions, or interactive features.
+ * Used in template cards and other preview contexts for performance.
+ */
+function WorkflowPreviewSubflowInner({ data }: NodeProps<WorkflowPreviewSubflowData>) {
+  const { name, width = 500, height = 300, kind } = data
+
+  const isLoop = kind === 'loop'
+  const BlockIcon = isLoop ? RepeatIcon : SplitIcon
+  const blockIconBg = isLoop ? '#2FB3FF' : '#FEE12B'
+  const blockName = name || (isLoop ? 'Loop' : 'Parallel')
+
+  // Handle IDs matching the actual subflow component
+  const startHandleId = isLoop ? 'loop-start-source' : 'parallel-start-source'
+  const endHandleId = isLoop ? 'loop-end-source' : 'parallel-end-source'
+
+  // Handle styles matching the actual subflow component
+  const handleClass =
+    '!border-none !bg-[var(--surface-12)] !h-5 !w-[7px] !rounded-l-[2px] !rounded-r-[2px]'
+
+  return (
+    <div
+      className='relative select-none rounded-[8px] border border-[var(--divider)]'
+      style={{
+        width,
+        height,
+      }}
+    >
+      {/* Target handle on left (input to the subflow) */}
+      <Handle
+        type='target'
+        position={Position.Left}
+        id='target'
+        className={handleClass}
+        style={{ left: '-7px', top: '20px', transform: 'translateY(-50%)' }}
+      />
+
+      {/* Header - matches actual subflow header */}
+      <div className='flex items-center gap-[10px] rounded-t-[8px] border-[var(--divider)] border-b bg-[var(--surface-2)] py-[8px] pr-[12px] pl-[8px]'>
+        <div
+          className='flex h-[24px] w-[24px] flex-shrink-0 items-center justify-center rounded-[6px]'
+          style={{ backgroundColor: blockIconBg }}
+        >
+          <BlockIcon className='h-[16px] w-[16px] text-white' />
+        </div>
+        <span className='font-medium text-[16px]' title={blockName}>
+          {blockName}
+        </span>
+      </div>
+
+      {/* Start handle inside - connects to first block in subflow */}
+      <div className='absolute top-[56px] left-[16px] flex items-center justify-center rounded-[8px] bg-[var(--surface-2)] px-[12px] py-[6px]'>
+        <span className='font-medium text-[14px] text-white'>Start</span>
+        <Handle
+          type='source'
+          position={Position.Right}
+          id={startHandleId}
+          className={handleClass}
+          style={{ right: '-7px', top: '50%', transform: 'translateY(-50%)' }}
+        />
+      </div>
+
+      {/* End source handle on right (output from the subflow) */}
+      <Handle
+        type='source'
+        position={Position.Right}
+        id={endHandleId}
+        className={handleClass}
+        style={{ right: '-7px', top: '20px', transform: 'translateY(-50%)' }}
+      />
+    </div>
+  )
+}
+
+export const WorkflowPreviewSubflow = memo(WorkflowPreviewSubflowInner)

apps/sim/app/workspace/[workspaceId]/w/components/workflow-preview/workflow-preview.tsx

@@ -1,7 +1,6 @@
 'use client'
 
 import { useMemo } from 'react'
-import { cloneDeep } from 'lodash'
 import ReactFlow, {
   ConnectionLineType,
   type Edge,
@@ -18,6 +17,8 @@ import { NoteBlock } from '@/app/workspace/[workspaceId]/w/[workflowId]/componen
 import { SubflowNodeComponent } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/subflows/subflow-node'
 import { WorkflowBlock } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-block/workflow-block'
 import { WorkflowEdge } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-edge/workflow-edge'
+import { WorkflowPreviewBlock } from '@/app/workspace/[workspaceId]/w/components/workflow-preview/workflow-preview-block'
+import { WorkflowPreviewSubflow } from '@/app/workspace/[workspaceId]/w/components/workflow-preview/workflow-preview-subflow'
 import { getBlock } from '@/blocks'
 import type { WorkflowState } from '@/stores/workflows/workflow/types'
 
@@ -34,15 +35,29 @@ interface WorkflowPreviewProps {
   defaultZoom?: number
   fitPadding?: number
   onNodeClick?: (blockId: string, mousePosition: { x: number; y: number }) => void
+  /** Use lightweight blocks for better performance in template cards */
+  lightweight?: boolean
 }
 
-// Define node types - the components now handle preview mode internally
-const nodeTypes: NodeTypes = {
+/**
+ * Full node types with interactive WorkflowBlock for detailed previews
+ */
+const fullNodeTypes: NodeTypes = {
   workflowBlock: WorkflowBlock,
   noteBlock: NoteBlock,
   subflowNode: SubflowNodeComponent,
 }
 
+/**
+ * Lightweight node types for template cards and other high-volume previews.
+ * Uses minimal components without hooks or store subscriptions.
+ */
+const lightweightNodeTypes: NodeTypes = {
+  workflowBlock: WorkflowPreviewBlock,
+  noteBlock: WorkflowPreviewBlock,
+  subflowNode: WorkflowPreviewSubflow,
+}
+
 // Define edge types
 const edgeTypes: EdgeTypes = {
   default: WorkflowEdge,
@@ -59,7 +74,10 @@ export function WorkflowPreview({
   defaultZoom = 0.8,
   fitPadding = 0.25,
   onNodeClick,
+  lightweight = false,
 }: WorkflowPreviewProps) {
+  // Use lightweight node types for better performance in template cards
+  const nodeTypes = lightweight ? lightweightNodeTypes : fullNodeTypes
   // Check if the workflow state is valid
   const isValidWorkflowState = workflowState?.blocks && workflowState.edges
 
@@ -130,6 +148,41 @@ export function WorkflowPreview({
 
       const absolutePosition = calculateAbsolutePosition(block, workflowState.blocks)
 
+      // Lightweight mode: create minimal node data for performance
+      if (lightweight) {
+        // Handle loops and parallels as subflow nodes
+        if (block.type === 'loop' || block.type === 'parallel') {
+          nodeArray.push({
+            id: blockId,
+            type: 'subflowNode',
+            position: absolutePosition,
+            draggable: false,
+            data: {
+              name: block.name,
+              width: block.data?.width || 500,
+              height: block.data?.height || 300,
+              kind: block.type as 'loop' | 'parallel',
+            },
+          })
+          return
+        }
+
+        // Regular blocks
+        nodeArray.push({
+          id: blockId,
+          type: 'workflowBlock',
+          position: absolutePosition,
+          draggable: false,
+          data: {
+            type: block.type,
+            name: block.name,
+            isTrigger: block.triggerMode === true,
+          },
+        })
+        return
+      }
+
+      // Full mode: create detailed node data for interactive previews
       if (block.type === 'loop') {
         nodeArray.push({
           id: block.id,
@@ -178,8 +231,6 @@ export function WorkflowPreview({
         return
       }
 
-      const subBlocksClone = block.subBlocks ? cloneDeep(block.subBlocks) : {}
-
       const nodeType = block.type === 'note' ? 'noteBlock' : 'workflowBlock'
 
       nodeArray.push({
@@ -194,7 +245,7 @@ export function WorkflowPreview({
           blockState: block,
           canEdit: false,
           isPreview: true,
-          subBlockValues: subBlocksClone,
+          subBlockValues: block.subBlocks ?? {},
         },
       })
 
@@ -242,6 +293,7 @@ export function WorkflowPreview({
     showSubBlocks,
     workflowState.blocks,
     isValidWorkflowState,
+    lightweight,
   ])
 
   const edges: Edge[] = useMemo(() => {