diff --git a/apps/sim/app/templates/components/template-card.tsx b/apps/sim/app/templates/components/template-card.tsx
index 0be5079e0..3c1c32a41 100644
--- a/apps/sim/app/templates/components/template-card.tsx
+++ b/apps/sim/app/templates/components/template-card.tsx
@@ -207,6 +207,7 @@ function TemplateCardInner({
             isPannable={false}
             defaultZoom={0.8}
             fitPadding={0.2}
+            lightweight
           />
         ) : (
           <div className='h-full w-full bg-[var(--surface-4)]' />
diff --git a/apps/sim/app/workspace/[workspaceId]/templates/components/template-card.tsx b/apps/sim/app/workspace/[workspaceId]/templates/components/template-card.tsx
index b32db3ff9..5bb5886d1 100644
--- a/apps/sim/app/workspace/[workspaceId]/templates/components/template-card.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/templates/components/template-card.tsx
@@ -214,6 +214,7 @@ function TemplateCardInner({
             defaultZoom={0.8}
             fitPadding={0.2}
             cursorStyle='pointer'
+            lightweight
           />
         ) : (
           <div className='h-full w-full bg-[var(--surface-4)] dark:bg-[var(--surface-5)]' />
diff --git a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/template/template.tsx b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/template/template.tsx
index 415c830f0..6ff75f6f6 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/template/template.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/deploy/components/deploy-modal/components/template/template.tsx
@@ -446,6 +446,7 @@ const OGCaptureContainer = forwardRef<HTMLDivElement>((_, ref) => {
         isPannable={false}
         defaultZoom={0.8}
         fitPadding={0.2}
+        lightweight
       />
     </div>
   )
diff --git a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/editor.tsx b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/editor.tsx
index 762ad1f2d..cc124bdd6 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/editor.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/panel/components/editor/editor.tsx
@@ -466,6 +466,7 @@ export function Editor() {
                               defaultZoom={0.6}
                               fitPadding={0.15}
                               cursorStyle='grab'
+                              lightweight
                             />
                           </div>
                           <Tooltip.Root>
diff --git a/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/block.tsx b/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/block.tsx
index a56e881de..84f53b415 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/block.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/block.tsx
@@ -1,6 +1,7 @@
 'use client'
 
 import { memo, useMemo } from 'react'
+import { RepeatIcon, SplitIcon } from 'lucide-react'
 import { Handle, type NodeProps, Position } from 'reactflow'
 import { HANDLE_POSITIONS } from '@/lib/workflows/blocks/block-dimensions'
 import {
@@ -10,14 +11,12 @@ import {
   isSubBlockVisibleForMode,
 } from '@/lib/workflows/subblocks/visibility'
 import { getDisplayValue } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-block/workflow-block'
+import type { ExecutionStatus } from '@/app/workspace/[workspaceId]/w/components/preview/preview'
 import { getBlock } from '@/blocks'
 import { SELECTOR_TYPES_HYDRATION_REQUIRED, type SubBlockConfig } from '@/blocks/types'
 import { useVariablesStore } from '@/stores/panel/variables/store'
 import { useWorkflowRegistry } from '@/stores/workflows/registry/store'
 
-/** Execution status for blocks in preview mode */
-type ExecutionStatus = 'success' | 'error' | 'not-executed'
-
 /** Subblock value structure matching workflow state */
 interface SubBlockValueEntry {
   value: unknown
@@ -35,6 +34,16 @@ interface WorkflowPreviewBlockData {
   executionStatus?: ExecutionStatus
   /** Subblock values from the workflow state */
   subBlockValues?: Record<string, SubBlockValueEntry | unknown>
+  /** Skips expensive subblock computations for thumbnails */
+  lightweight?: boolean
+  /** Whether this is a subflow container (loop/parallel) */
+  isSubflow?: boolean
+  /** Type of subflow container */
+  subflowKind?: 'loop' | 'parallel'
+  /** Width of subflow container */
+  width?: number
+  /** Height of subflow container */
+  height?: number
 }
 
 /**
@@ -204,21 +213,16 @@ function resolveToolsDisplay(
  * - Shows '-' for other selector types that need hydration
  */
 function SubBlockRow({ title, value, subBlock, rawValue }: SubBlockRowProps) {
-  // Mask password fields
   const isPasswordField = subBlock?.password === true
   const maskedValue = isPasswordField && value && value !== '-' ? '•••' : null
 
-  // Resolve various display names (synchronous access, matching WorkflowBlock priority)
   const dropdownLabel = resolveDropdownLabel(subBlock, rawValue)
   const variablesDisplay = resolveVariablesDisplay(subBlock, rawValue)
   const toolsDisplay = resolveToolsDisplay(subBlock, rawValue)
   const workflowName = resolveWorkflowName(subBlock, rawValue)
 
-  // Check if this is a selector type that needs hydration (show '-' for raw IDs)
   const isSelectorType = subBlock?.type && SELECTOR_TYPES_HYDRATION_REQUIRED.includes(subBlock.type)
 
-  // Compute final display value matching WorkflowBlock logic
-  // Priority order matches WorkflowBlock: masked > hydrated names > selector fallback > raw value
   const hydratedName = dropdownLabel || variablesDisplay || toolsDisplay || workflowName
   const displayValue = maskedValue || hydratedName || (isSelectorType && value ? '-' : value)
 
@@ -242,11 +246,115 @@ function SubBlockRow({ title, value, subBlock, rawValue }: SubBlockRowProps) {
   )
 }
 
+interface SubflowContainerProps {
+  name: string
+  width?: number
+  height?: number
+  kind: 'loop' | 'parallel'
+  isPreviewSelected?: boolean
+}
+
+/**
+ * Renders a subflow container (loop/parallel) for preview mode.
+ */
+function SubflowContainer({
+  name,
+  width = 500,
+  height = 300,
+  kind,
+  isPreviewSelected = false,
+}: SubflowContainerProps) {
+  const isLoop = kind === 'loop'
+  const BlockIcon = isLoop ? RepeatIcon : SplitIcon
+  const blockIconBg = isLoop ? '#2FB3FF' : '#FEE12B'
+  const blockName = name || (isLoop ? 'Loop' : 'Parallel')
+
+  const startHandleId = isLoop ? 'loop-start-source' : 'parallel-start-source'
+  const endHandleId = isLoop ? 'loop-end-source' : 'parallel-end-source'
+
+  const leftHandleClass =
+    '!z-[10] !border-none !bg-[var(--workflow-edge)] !h-5 !w-[7px] !rounded-l-[2px] !rounded-r-none'
+  const rightHandleClass =
+    '!z-[10] !border-none !bg-[var(--workflow-edge)] !h-5 !w-[7px] !rounded-r-[2px] !rounded-l-none'
+
+  return (
+    <div
+      className='relative select-none rounded-[8px] border border-[var(--border-1)]'
+      style={{ width, height }}
+    >
+      {/* Selection ring overlay */}
+      {isPreviewSelected && (
+        <div className='pointer-events-none absolute inset-0 z-40 rounded-[8px] ring-[1.75px] ring-[var(--brand-secondary)]' />
+      )}
+
+      {/* Target handle on left (input to the subflow) */}
+      <Handle
+        type='target'
+        position={Position.Left}
+        id='target'
+        className={leftHandleClass}
+        style={{
+          left: '-8px',
+          top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px`,
+          transform: 'translateY(-50%)',
+        }}
+      />
+
+      {/* Header - matches actual subflow header structure */}
+      <div className='flex items-center justify-between rounded-t-[8px] border-[var(--border)] border-b bg-[var(--surface-2)] py-[8px] pr-[12px] pl-[8px]'>
+        <div className='flex min-w-0 flex-1 items-center gap-[10px]'>
+          <div
+            className='flex h-[24px] w-[24px] flex-shrink-0 items-center justify-center rounded-[6px]'
+            style={{ backgroundColor: blockIconBg }}
+          >
+            <BlockIcon className='h-[16px] w-[16px] text-white' />
+          </div>
+          <span className='font-medium text-[16px]' title={blockName}>
+            {blockName}
+          </span>
+        </div>
+      </div>
+
+      {/* Content area - matches workflow structure */}
+      <div
+        className='h-[calc(100%-50px)] pt-[16px] pr-[80px] pb-[16px] pl-[16px]'
+        style={{ position: 'relative' }}
+      >
+        {/* Subflow Start - connects to first block in subflow */}
+        <div className='absolute top-[16px] left-[16px] flex items-center justify-center rounded-[8px] border border-[var(--border-1)] bg-[var(--surface-2)] px-[12px] py-[6px]'>
+          <span className='font-medium text-[14px] text-[var(--text-primary)]'>Start</span>
+          <Handle
+            type='source'
+            position={Position.Right}
+            id={startHandleId}
+            className={rightHandleClass}
+            style={{ right: '-8px', top: '50%', transform: 'translateY(-50%)' }}
+          />
+        </div>
+      </div>
+
+      {/* End source handle on right (output from the subflow) */}
+      <Handle
+        type='source'
+        position={Position.Right}
+        id={endHandleId}
+        className={rightHandleClass}
+        style={{
+          right: '-8px',
+          top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px`,
+          transform: 'translateY(-50%)',
+        }}
+      />
+    </div>
+  )
+}
+
 /**
  * Preview block component for workflow visualization.
  * Renders block header, subblock values, and handles without
  * hooks, store subscriptions, or interactive features.
  * Matches the visual structure of WorkflowBlock exactly.
+ * Also handles subflow containers (loop/parallel) when isSubflow is true.
  */
 function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>) {
   const {
@@ -258,53 +366,84 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
     isPreviewSelected = false,
     executionStatus,
     subBlockValues,
+    lightweight = false,
+    isSubflow = false,
+    subflowKind,
+    width,
+    height,
   } = data
 
+  if (isSubflow && subflowKind) {
+    return (
+      <SubflowContainer
+        name={name}
+        width={width}
+        height={height}
+        kind={subflowKind}
+        isPreviewSelected={isPreviewSelected}
+      />
+    )
+  }
+
   const blockConfig = getBlock(type)
 
   const canonicalIndex = useMemo(
-    () => buildCanonicalIndex(blockConfig?.subBlocks || []),
-    [blockConfig?.subBlocks]
+    () =>
+      lightweight
+        ? { groupsById: {}, canonicalIdBySubBlockId: {} }
+        : buildCanonicalIndex(blockConfig?.subBlocks || []),
+    [blockConfig?.subBlocks, lightweight]
   )
 
   const rawValues = useMemo(() => {
-    if (!subBlockValues) return {}
+    if (lightweight || !subBlockValues) return {}
     return Object.entries(subBlockValues).reduce<Record<string, unknown>>((acc, [key, entry]) => {
       acc[key] = extractValue(entry)
       return acc
     }, {})
-  }, [subBlockValues])
+  }, [subBlockValues, lightweight])
 
   const visibleSubBlocks = useMemo(() => {
-    if (!blockConfig?.subBlocks) return []
+    if (lightweight || !blockConfig?.subBlocks) return []
 
-    const isStarterOrTrigger =
-      blockConfig.category === 'triggers' || type === 'starter' || isTrigger
+    const isPureTriggerBlock = blockConfig.triggers?.enabled && blockConfig.category === 'triggers'
+
+    const effectiveTrigger = isTrigger || type === 'starter'
 
     return blockConfig.subBlocks.filter((subBlock) => {
       if (subBlock.hidden) return false
       if (subBlock.hideFromPreview) return false
       if (!isSubBlockFeatureEnabled(subBlock)) return false
 
-      // Handle trigger mode visibility
-      if (subBlock.mode === 'trigger' && !isStarterOrTrigger) return false
+      if (effectiveTrigger) {
+        const isValidTriggerSubblock = isPureTriggerBlock
+          ? subBlock.mode === 'trigger' || !subBlock.mode
+          : subBlock.mode === 'trigger'
+        if (!isValidTriggerSubblock) return false
+      } else {
+        if (subBlock.mode === 'trigger') return false
+      }
 
-      // Check advanced mode visibility
       if (!isSubBlockVisibleForMode(subBlock, false, canonicalIndex, rawValues, undefined)) {
         return false
       }
 
-      // Check condition visibility
       if (!subBlock.condition) return true
       return evaluateSubBlockCondition(subBlock.condition, rawValues)
     })
-  }, [blockConfig?.subBlocks, blockConfig?.category, type, isTrigger, canonicalIndex, rawValues])
+  }, [
+    lightweight,
+    blockConfig?.subBlocks,
+    blockConfig?.category,
+    blockConfig?.triggers?.enabled,
+    type,
+    isTrigger,
+    canonicalIndex,
+    rawValues,
+  ])
 
-  /**
-   * Compute condition rows for condition blocks
-   */
   const conditionRows = useMemo(() => {
-    if (type !== 'condition') return []
+    if (lightweight || type !== 'condition') return []
 
     const conditionsValue = rawValues.conditions
     const raw = typeof conditionsValue === 'string' ? conditionsValue : undefined
@@ -332,13 +471,10 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
       { id: 'if', title: 'if', value: '' },
       { id: 'else', title: 'else', value: '' },
     ]
-  }, [type, rawValues])
+  }, [lightweight, type, rawValues])
 
-  /**
-   * Compute router rows for router_v2 blocks
-   */
   const routerRows = useMemo(() => {
-    if (type !== 'router_v2') return []
+    if (lightweight || type !== 'router_v2') return []
 
     const routesValue = rawValues.routes
     const raw = typeof routesValue === 'string' ? routesValue : undefined
@@ -361,7 +497,7 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
     }
 
     return [{ id: 'route1', value: '' }]
-  }, [type, rawValues])
+  }, [lightweight, type, rawValues])
 
   if (!blockConfig) {
     return null
@@ -439,12 +575,10 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
       {hasContentBelowHeader && (
         <div className='flex flex-col gap-[8px] p-[8px]'>
           {type === 'condition' ? (
-            // Condition block: render condition rows
             conditionRows.map((cond) => (
               <SubBlockRow key={cond.id} title={cond.title} value={getDisplayValue(cond.value)} />
             ))
           ) : type === 'router_v2' ? (
-            // Router block: render context + route rows
             <>
               <SubBlockRow
                 key='context'
@@ -460,7 +594,6 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
               ))}
             </>
           ) : (
-            // Standard blocks: render visible subblocks
             visibleSubBlocks.map((subBlock) => {
               const rawValue = rawValues[subBlock.id]
               return (
@@ -479,18 +612,102 @@ function WorkflowPreviewBlockInner({ data }: NodeProps<WorkflowPreviewBlockData>
         </div>
       )}
 
-      {/* Source handle */}
-      <Handle
-        type='source'
-        position={horizontalHandles ? Position.Right : Position.Bottom}
-        id='source'
-        className={horizontalHandles ? horizontalHandleClass : verticalHandleClass}
-        style={
-          horizontalHandles
-            ? { right: '-7px', top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px` }
-            : { bottom: '-7px', left: '50%', transform: 'translateX(-50%)' }
-        }
-      />
+      {/* Condition block handles - one per condition branch + error */}
+      {type === 'condition' && (
+        <>
+          {conditionRows.map((cond, condIndex) => {
+            const topOffset =
+              HANDLE_POSITIONS.CONDITION_START_Y + condIndex * HANDLE_POSITIONS.CONDITION_ROW_HEIGHT
+            return (
+              <Handle
+                key={`handle-${cond.id}`}
+                type='source'
+                position={Position.Right}
+                id={`condition-${cond.id}`}
+                className={horizontalHandleClass}
+                style={{ right: '-7px', top: `${topOffset}px`, transform: 'translateY(-50%)' }}
+              />
+            )
+          })}
+          <Handle
+            type='source'
+            position={Position.Right}
+            id='error'
+            className='!border-none !bg-[var(--text-error)] !h-5 !w-[7px] !rounded-[2px]'
+            style={{
+              right: '-7px',
+              top: 'auto',
+              bottom: `${HANDLE_POSITIONS.ERROR_BOTTOM_OFFSET}px`,
+              transform: 'translateY(50%)',
+            }}
+          />
+        </>
+      )}
+
+      {/* Router block handles - one per route + error */}
+      {type === 'router_v2' && (
+        <>
+          {routerRows.map((route, routeIndex) => {
+            // +1 row offset for context row at the top
+            const topOffset =
+              HANDLE_POSITIONS.CONDITION_START_Y +
+              (routeIndex + 1) * HANDLE_POSITIONS.CONDITION_ROW_HEIGHT
+            return (
+              <Handle
+                key={`handle-${route.id}`}
+                type='source'
+                position={Position.Right}
+                id={`router-${route.id}`}
+                className={horizontalHandleClass}
+                style={{ right: '-7px', top: `${topOffset}px`, transform: 'translateY(-50%)' }}
+              />
+            )
+          })}
+          <Handle
+            type='source'
+            position={Position.Right}
+            id='error'
+            className='!border-none !bg-[var(--text-error)] !h-5 !w-[7px] !rounded-[2px]'
+            style={{
+              right: '-7px',
+              top: 'auto',
+              bottom: `${HANDLE_POSITIONS.ERROR_BOTTOM_OFFSET}px`,
+              transform: 'translateY(50%)',
+            }}
+          />
+        </>
+      )}
+
+      {/* Standard block handles - source + error (not for condition, router, or response) */}
+      {type !== 'condition' && type !== 'router_v2' && type !== 'response' && (
+        <>
+          <Handle
+            type='source'
+            position={horizontalHandles ? Position.Right : Position.Bottom}
+            id='source'
+            className={horizontalHandles ? horizontalHandleClass : verticalHandleClass}
+            style={
+              horizontalHandles
+                ? { right: '-7px', top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px` }
+                : { bottom: '-7px', left: '50%', transform: 'translateX(-50%)' }
+            }
+          />
+          {shouldShowDefaultHandles && (
+            <Handle
+              type='source'
+              position={Position.Right}
+              id='error'
+              className='!border-none !bg-[var(--text-error)] !h-5 !w-[7px] !rounded-[2px]'
+              style={{
+                right: '-7px',
+                top: 'auto',
+                bottom: `${HANDLE_POSITIONS.ERROR_BOTTOM_OFFSET}px`,
+                transform: 'translateY(50%)',
+              }}
+            />
+          )}
+        </>
+      )}
     </div>
   )
 }
@@ -499,7 +716,6 @@ function shouldSkipPreviewBlockRender(
   prevProps: NodeProps<WorkflowPreviewBlockData>,
   nextProps: NodeProps<WorkflowPreviewBlockData>
 ): boolean {
-  // Check primitive props first (fast path)
   if (
     prevProps.id !== nextProps.id ||
     prevProps.data.type !== nextProps.data.type ||
@@ -508,12 +724,16 @@ function shouldSkipPreviewBlockRender(
     prevProps.data.horizontalHandles !== nextProps.data.horizontalHandles ||
     prevProps.data.enabled !== nextProps.data.enabled ||
     prevProps.data.isPreviewSelected !== nextProps.data.isPreviewSelected ||
-    prevProps.data.executionStatus !== nextProps.data.executionStatus
+    prevProps.data.executionStatus !== nextProps.data.executionStatus ||
+    prevProps.data.lightweight !== nextProps.data.lightweight ||
+    prevProps.data.isSubflow !== nextProps.data.isSubflow ||
+    prevProps.data.subflowKind !== nextProps.data.subflowKind ||
+    prevProps.data.width !== nextProps.data.width ||
+    prevProps.data.height !== nextProps.data.height
   ) {
     return false
   }
 
-  // Compare subBlockValues by reference first
   const prevValues = prevProps.data.subBlockValues
   const nextValues = nextProps.data.subBlockValues
 
@@ -525,7 +745,6 @@ function shouldSkipPreviewBlockRender(
     return false
   }
 
-  // Shallow compare keys and values
   const prevKeys = Object.keys(prevValues)
   const nextKeys = Object.keys(nextValues)
 
diff --git a/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/subflow.tsx b/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/subflow.tsx
deleted file mode 100644
index a9aa913a2..000000000
--- a/apps/sim/app/workspace/[workspaceId]/w/components/preview/components/subflow.tsx
+++ /dev/null
@@ -1,113 +0,0 @@
-'use client'
-
-import { memo } from 'react'
-import { RepeatIcon, SplitIcon } from 'lucide-react'
-import { Handle, type NodeProps, Position } from 'reactflow'
-import { HANDLE_POSITIONS } from '@/lib/workflows/blocks/block-dimensions'
-
-interface WorkflowPreviewSubflowData {
-  name: string
-  width?: number
-  height?: number
-  kind: 'loop' | 'parallel'
-  /** Whether this subflow is selected in preview mode */
-  isPreviewSelected?: boolean
-}
-
-/**
- * Preview subflow component for workflow visualization.
- * Renders loop/parallel containers without hooks, store subscriptions,
- * or interactive features.
- */
-function WorkflowPreviewSubflowInner({ data }: NodeProps<WorkflowPreviewSubflowData>) {
-  const { name, width = 500, height = 300, kind, isPreviewSelected = false } = data
-
-  const isLoop = kind === 'loop'
-  const BlockIcon = isLoop ? RepeatIcon : SplitIcon
-  const blockIconBg = isLoop ? '#2FB3FF' : '#FEE12B'
-  const blockName = name || (isLoop ? 'Loop' : 'Parallel')
-
-  const startHandleId = isLoop ? 'loop-start-source' : 'parallel-start-source'
-  const endHandleId = isLoop ? 'loop-end-source' : 'parallel-end-source'
-
-  const leftHandleClass =
-    '!z-[10] !border-none !bg-[var(--workflow-edge)] !h-5 !w-[7px] !rounded-l-[2px] !rounded-r-none'
-  const rightHandleClass =
-    '!z-[10] !border-none !bg-[var(--workflow-edge)] !h-5 !w-[7px] !rounded-r-[2px] !rounded-l-none'
-
-  return (
-    <div
-      className='relative select-none rounded-[8px] border border-[var(--border-1)]'
-      style={{
-        width,
-        height,
-      }}
-    >
-      {/* Selection ring overlay */}
-      {isPreviewSelected && (
-        <div className='pointer-events-none absolute inset-0 z-40 rounded-[8px] ring-[1.75px] ring-[var(--brand-secondary)]' />
-      )}
-
-      {/* Target handle on left (input to the subflow) */}
-      <Handle
-        type='target'
-        position={Position.Left}
-        id='target'
-        className={leftHandleClass}
-        style={{
-          left: '-8px',
-          top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px`,
-          transform: 'translateY(-50%)',
-        }}
-      />
-
-      {/* Header - matches actual subflow header structure */}
-      <div className='flex items-center justify-between rounded-t-[8px] border-[var(--border)] border-b bg-[var(--surface-2)] py-[8px] pr-[12px] pl-[8px]'>
-        <div className='flex min-w-0 flex-1 items-center gap-[10px]'>
-          <div
-            className='flex h-[24px] w-[24px] flex-shrink-0 items-center justify-center rounded-[6px]'
-            style={{ backgroundColor: blockIconBg }}
-          >
-            <BlockIcon className='h-[16px] w-[16px] text-white' />
-          </div>
-          <span className='font-medium text-[16px]' title={blockName}>
-            {blockName}
-          </span>
-        </div>
-      </div>
-
-      {/* Content area - matches workflow structure */}
-      <div
-        className='h-[calc(100%-50px)] pt-[16px] pr-[80px] pb-[16px] pl-[16px]'
-        style={{ position: 'relative' }}
-      >
-        {/* Subflow Start - connects to first block in subflow */}
-        <div className='absolute top-[16px] left-[16px] flex items-center justify-center rounded-[8px] border border-[var(--border-1)] bg-[var(--surface-2)] px-[12px] py-[6px]'>
-          <span className='font-medium text-[14px] text-[var(--text-primary)]'>Start</span>
-          <Handle
-            type='source'
-            position={Position.Right}
-            id={startHandleId}
-            className={rightHandleClass}
-            style={{ right: '-8px', top: '50%', transform: 'translateY(-50%)' }}
-          />
-        </div>
-      </div>
-
-      {/* End source handle on right (output from the subflow) */}
-      <Handle
-        type='source'
-        position={Position.Right}
-        id={endHandleId}
-        className={rightHandleClass}
-        style={{
-          right: '-8px',
-          top: `${HANDLE_POSITIONS.DEFAULT_Y_OFFSET}px`,
-          transform: 'translateY(-50%)',
-        }}
-      />
-    </div>
-  )
-}
-
-export const WorkflowPreviewSubflow = memo(WorkflowPreviewSubflowInner)
diff --git a/apps/sim/app/workspace/[workspaceId]/w/components/preview/preview.tsx b/apps/sim/app/workspace/[workspaceId]/w/components/preview/preview.tsx
index a9d56c794..ec00e2c38 100644
--- a/apps/sim/app/workspace/[workspaceId]/w/components/preview/preview.tsx
+++ b/apps/sim/app/workspace/[workspaceId]/w/components/preview/preview.tsx
@@ -18,7 +18,6 @@ import { BLOCK_DIMENSIONS, CONTAINER_DIMENSIONS } from '@/lib/workflows/blocks/b
 import { WorkflowEdge } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-edge/workflow-edge'
 import { estimateBlockDimensions } from '@/app/workspace/[workspaceId]/w/[workflowId]/utils'
 import { WorkflowPreviewBlock } from '@/app/workspace/[workspaceId]/w/components/preview/components/block'
-import { WorkflowPreviewSubflow } from '@/app/workspace/[workspaceId]/w/components/preview/components/subflow'
 import type { BlockState, WorkflowState } from '@/stores/workflows/workflow/types'
 
 const logger = createLogger('WorkflowPreview')
@@ -53,13 +52,12 @@ function getPreviewBlockDimensions(block: BlockState): { width: number; height:
 /**
  * Calculates container dimensions based on child block positions and sizes.
  * Mirrors the logic from useNodeUtilities.calculateLoopDimensions.
+ * Accepts pre-filtered childBlocks for O(1) lookup instead of filtering all blocks.
  */
-function calculateContainerDimensions(
-  containerId: string,
-  blocks: Record<string, BlockState>
-): { width: number; height: number } {
-  const childBlocks = Object.values(blocks).filter((block) => block?.data?.parentId === containerId)
-
+function calculateContainerDimensions(childBlocks: BlockState[]): {
+  width: number
+  height: number
+} {
   if (childBlocks.length === 0) {
     return {
       width: CONTAINER_DIMENSIONS.DEFAULT_WIDTH,
@@ -113,8 +111,34 @@ export function getLeftmostBlockId(workflowState: WorkflowState | null | undefin
   return leftmostId
 }
 
+/**
+ * Recursively calculates the absolute position of a block,
+ * accounting for parent container offsets.
+ */
+function calculateAbsolutePosition(
+  block: BlockState,
+  blocks: Record<string, BlockState>
+): { x: number; y: number } {
+  if (!block.data?.parentId) {
+    return block.position
+  }
+
+  const parentBlock = blocks[block.data.parentId]
+  if (!parentBlock) {
+    logger.warn(`Parent block not found for child block: ${block.id}`)
+    return block.position
+  }
+
+  const parentAbsolutePosition = calculateAbsolutePosition(parentBlock, blocks)
+
+  return {
+    x: parentAbsolutePosition.x + block.position.x,
+    y: parentAbsolutePosition.y + block.position.y,
+  }
+}
+
 /** Execution status for edges/nodes in the preview */
-type ExecutionStatus = 'success' | 'error' | 'not-executed'
+export type ExecutionStatus = 'success' | 'error' | 'not-executed'
 
 interface WorkflowPreviewProps {
   workflowState: WorkflowState
@@ -136,6 +160,8 @@ interface WorkflowPreviewProps {
   executedBlocks?: Record<string, { status: string }>
   /** Currently selected block ID for highlighting */
   selectedBlockId?: string | null
+  /** Skips expensive computations for thumbnails/template previews */
+  lightweight?: boolean
 }
 
 /**
@@ -144,8 +170,6 @@ interface WorkflowPreviewProps {
  */
 const previewNodeTypes: NodeTypes = {
   workflowBlock: WorkflowPreviewBlock,
-  noteBlock: WorkflowPreviewBlock,
-  subflowNode: WorkflowPreviewSubflow,
 }
 
 // Define edge types
@@ -221,64 +245,30 @@ export function WorkflowPreview({
   cursorStyle = 'grab',
   executedBlocks,
   selectedBlockId,
+  lightweight = false,
 }: WorkflowPreviewProps) {
   const containerRef = useRef<HTMLDivElement>(null)
-  const nodeTypes = previewNodeTypes
   const isValidWorkflowState = workflowState?.blocks && workflowState.edges
 
-  const blocksStructure = useMemo(() => {
-    if (!isValidWorkflowState) return { count: 0, ids: '' }
-    return {
-      count: Object.keys(workflowState.blocks || {}).length,
-      ids: Object.keys(workflowState.blocks || {}).join(','),
-    }
-  }, [workflowState.blocks, isValidWorkflowState])
+  const workflowStructureIds = useMemo(() => {
+    if (!isValidWorkflowState) return ''
+    const blockIds = Object.keys(workflowState.blocks || {})
+    const edgeIds = (workflowState.edges || []).map((e) => e.id)
+    return [...blockIds, ...edgeIds].join(',')
+  }, [workflowState.blocks, workflowState.edges, isValidWorkflowState])
 
-  const loopsStructure = useMemo(() => {
-    if (!isValidWorkflowState) return { count: 0, ids: '' }
-    return {
-      count: Object.keys(workflowState.loops || {}).length,
-      ids: Object.keys(workflowState.loops || {}).join(','),
+  // Pre-compute parent-child relationships for O(1) lookups in container dimension calculations
+  const containerChildIndex = useMemo(() => {
+    const index: Record<string, BlockState[]> = {}
+    for (const block of Object.values(workflowState.blocks || {})) {
+      if (block?.data?.parentId) {
+        const parentId = block.data.parentId
+        if (!index[parentId]) index[parentId] = []
+        index[parentId].push(block)
+      }
     }
-  }, [workflowState.loops, isValidWorkflowState])
-
-  const parallelsStructure = useMemo(() => {
-    if (!isValidWorkflowState) return { count: 0, ids: '' }
-    return {
-      count: Object.keys(workflowState.parallels || {}).length,
-      ids: Object.keys(workflowState.parallels || {}).join(','),
-    }
-  }, [workflowState.parallels, isValidWorkflowState])
-
-  const edgesStructure = useMemo(() => {
-    if (!isValidWorkflowState) return { count: 0, ids: '' }
-    return {
-      count: workflowState.edges?.length || 0,
-      ids: workflowState.edges?.map((e) => e.id).join(',') || '',
-    }
-  }, [workflowState.edges, isValidWorkflowState])
-
-  const calculateAbsolutePosition = (
-    block: any,
-    blocks: Record<string, any>
-  ): { x: number; y: number } => {
-    if (!block.data?.parentId) {
-      return block.position
-    }
-
-    const parentBlock = blocks[block.data.parentId]
-    if (!parentBlock) {
-      logger.warn(`Parent block not found for child block: ${block.id}`)
-      return block.position
-    }
-
-    const parentAbsolutePosition = calculateAbsolutePosition(parentBlock, blocks)
-
-    return {
-      x: parentAbsolutePosition.x + block.position.x,
-      y: parentAbsolutePosition.y + block.position.y,
-    }
-  }
+    return index
+  }, [workflowState.blocks])
 
   const nodes: Node[] = useMemo(() => {
     if (!isValidWorkflowState) return []
@@ -293,21 +283,24 @@ export function WorkflowPreview({
 
       const absolutePosition = calculateAbsolutePosition(block, workflowState.blocks)
 
-      // Handle loop/parallel containers
+      // Handle loop/parallel containers - use unified workflowBlock with isSubflow flag
       if (block.type === 'loop' || block.type === 'parallel') {
         const isSelected = selectedBlockId === blockId
-        const dimensions = calculateContainerDimensions(blockId, workflowState.blocks)
+        const childBlocks = containerChildIndex[blockId] || []
+        const dimensions = calculateContainerDimensions(childBlocks)
         nodeArray.push({
           id: blockId,
-          type: 'subflowNode',
+          type: 'workflowBlock',
           position: absolutePosition,
           draggable: false,
           data: {
+            type: block.type,
             name: block.name,
+            isPreviewSelected: isSelected,
+            isSubflow: true,
+            subflowKind: block.type as 'loop' | 'parallel',
             width: dimensions.width,
             height: dimensions.height,
-            kind: block.type as 'loop' | 'parallel',
-            isPreviewSelected: isSelected,
           },
         })
         return
@@ -348,19 +341,20 @@ export function WorkflowPreview({
           isPreviewSelected: isSelected,
           executionStatus,
           subBlockValues: block.subBlocks,
+          lightweight,
         },
       })
     })
 
     return nodeArray
   }, [
-    blocksStructure,
-    loopsStructure,
-    parallelsStructure,
+    workflowStructureIds,
     workflowState.blocks,
+    containerChildIndex,
     isValidWorkflowState,
     executedBlocks,
     selectedBlockId,
+    lightweight,
   ])
 
   const edges: Edge[] = useMemo(() => {
@@ -395,7 +389,7 @@ export function WorkflowPreview({
         zIndex: executionStatus === 'success' ? 10 : 0,
       }
     })
-  }, [edgesStructure, workflowState.edges, isValidWorkflowState, executedBlocks])
+  }, [workflowStructureIds, workflowState.edges, isValidWorkflowState, executedBlocks])
 
   if (!isValidWorkflowState) {
     return (
@@ -449,7 +443,7 @@ export function WorkflowPreview({
         <ReactFlow
           nodes={nodes}
           edges={edges}
-          nodeTypes={nodeTypes}
+          nodeTypes={previewNodeTypes}
           edgeTypes={edgeTypes}
           connectionLineType={ConnectionLineType.SmoothStep}
           fitView
@@ -489,7 +483,7 @@ export function WorkflowPreview({
           onPaneClick={onPaneClick}
         />
         <FitViewOnChange
-          nodeIds={blocksStructure.ids}
+          nodeIds={workflowStructureIds}
           fitPadding={fitPadding}
           containerRef={containerRef}
         />