v0.5.106: condition block and legacy kbs fixes, GPT 5.4

* fix(condition): consecutive error logging + execution dequeuing

* fix snapshot highlighting

* address minor gaps

* fix incomplete case

* remove activatedEdges path

* cleanup tests

* address greptile comments

* update tests:

.github/workflows/test-build.yml

@@ -90,6 +90,16 @@ jobs:
 
           echo "✅ All feature flags are properly configured"
 
+      - name: Check subblock ID stability
+        run: |
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            BASE_REF="origin/${{ github.base_ref }}"
+            git fetch --depth=1 origin "${{ github.base_ref }}" 2>/dev/null || true
+          else
+            BASE_REF="HEAD~1"
+          fi
+          bun run apps/sim/scripts/check-subblock-id-stability.ts "$BASE_REF"
+
       - name: Lint code
         run: bun run lint:check
 

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/hooks/use-workflow-execution.ts

@@ -20,7 +20,10 @@ import {
   TriggerUtils,
 } from '@/lib/workflows/triggers/triggers'
 import { useCurrentWorkflow } from '@/app/workspace/[workspaceId]/w/[workflowId]/hooks/use-current-workflow'
-import { updateActiveBlockRefCount } from '@/app/workspace/[workspaceId]/w/[workflowId]/utils/workflow-execution-utils'
+import {
+  markOutgoingEdgesFromOutput,
+  updateActiveBlockRefCount,
+} from '@/app/workspace/[workspaceId]/w/[workflowId]/utils/workflow-execution-utils'
 import { getBlock } from '@/blocks'
 import type { SerializableExecutionState } from '@/executor/execution/types'
 import type {
@@ -63,7 +66,7 @@ interface DebugValidationResult {
 interface BlockEventHandlerConfig {
   workflowId?: string
   executionIdRef: { current: string }
-  workflowEdges: Array<{ id: string; target: string; sourceHandle?: string | null }>
+  workflowEdges: Array<{ id: string; source: string; target: string; sourceHandle?: string | null }>
   activeBlocksSet: Set<string>
   activeBlockRefCounts: Map<string, number>
   accumulatedBlockLogs: BlockLog[]
@@ -335,13 +338,9 @@ export function useWorkflowExecution() {
         setActiveBlocks(workflowId, new Set(activeBlocksSet))
       }
 
-      const markIncomingEdges = (blockId: string) => {
+      const markOutgoingEdges = (blockId: string, output: Record<string, any> | undefined) => {
         if (!workflowId) return
-        const incomingEdges = workflowEdges.filter((edge) => edge.target === blockId)
-        incomingEdges.forEach((edge) => {
-          const status = edge.sourceHandle === 'error' ? 'error' : 'success'
-          setEdgeRunStatus(workflowId, edge.id, status)
-        })
+        markOutgoingEdgesFromOutput(blockId, output, workflowEdges, workflowId, setEdgeRunStatus)
       }
 
       const isContainerBlockType = (blockType?: string) => {
@@ -460,7 +459,6 @@ export function useWorkflowExecution() {
       const onBlockStarted = (data: BlockStartedData) => {
         if (isStaleExecution()) return
         updateActiveBlocks(data.blockId, true)
-        markIncomingEdges(data.blockId)
 
         if (!includeStartConsoleEntry || !workflowId) return
 
@@ -487,6 +485,7 @@ export function useWorkflowExecution() {
         if (isStaleExecution()) return
         updateActiveBlocks(data.blockId, false)
         if (workflowId) setBlockRunStatus(workflowId, data.blockId, 'success')
+        markOutgoingEdges(data.blockId, data.output as Record<string, any> | undefined)
         executedBlockIds.add(data.blockId)
         accumulatedBlockStates.set(data.blockId, {
           output: data.output,
@@ -505,7 +504,9 @@ export function useWorkflowExecution() {
         }
 
         if (isContainerBlockType(data.blockType) && !data.iterationContainerId) {
-          return
+          const output = data.output as Record<string, any> | undefined
+          const isEmptySubflow = Array.isArray(output?.results) && output.results.length === 0
+          if (!isEmptySubflow) return
         }
 
         accumulatedBlockLogs.push(createBlockLogEntry(data, { success: true, output: data.output }))
@@ -527,6 +528,7 @@ export function useWorkflowExecution() {
         if (isStaleExecution()) return
         updateActiveBlocks(data.blockId, false)
         if (workflowId) setBlockRunStatus(workflowId, data.blockId, 'error')
+        markOutgoingEdges(data.blockId, { error: data.error })
 
         executedBlockIds.add(data.blockId)
         accumulatedBlockStates.set(data.blockId, {

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/utils/workflow-execution-utils.ts

@@ -29,6 +29,62 @@ export function updateActiveBlockRefCount(
   }
 }
 
+/**
+ * Determines if a workflow edge should be marked as active based on its handle and the block output.
+ * Mirrors the executor's EdgeManager.shouldActivateEdge logic on the client side.
+ * Exclude sentinel handles here
+ */
+function shouldActivateEdgeClient(
+  handle: string | null | undefined,
+  output: Record<string, any> | undefined
+): boolean {
+  if (!handle) return true
+
+  if (handle.startsWith('condition-')) {
+    return output?.selectedOption === handle.substring('condition-'.length)
+  }
+
+  if (handle.startsWith('router-')) {
+    return output?.selectedRoute === handle.substring('router-'.length)
+  }
+
+  switch (handle) {
+    case 'error':
+      return !!output?.error
+    case 'source':
+      return !output?.error
+    case 'loop-start-source':
+    case 'loop-end-source':
+    case 'parallel-start-source':
+    case 'parallel-end-source':
+      return true
+    default:
+      return true
+  }
+}
+
+export function markOutgoingEdgesFromOutput(
+  blockId: string,
+  output: Record<string, any> | undefined,
+  workflowEdges: Array<{
+    id: string
+    source: string
+    target: string
+    sourceHandle?: string | null
+  }>,
+  workflowId: string,
+  setEdgeRunStatus: (wfId: string, edgeId: string, status: 'success' | 'error') => void
+): void {
+  const outgoing = workflowEdges.filter((edge) => edge.source === blockId)
+  for (const edge of outgoing) {
+    const handle = edge.sourceHandle
+    if (shouldActivateEdgeClient(handle, output)) {
+      const status = handle === 'error' ? 'error' : output?.error ? 'error' : 'success'
+      setEdgeRunStatus(workflowId, edge.id, status)
+    }
+  }
+}
+
 export interface WorkflowExecutionOptions {
   workflowInput?: any
   onStream?: (se: StreamingExecution) => Promise<void>
@@ -135,13 +191,6 @@ export async function executeWorkflowWithFullLogging(
                 true
               )
               setActiveBlocks(wfId, new Set(activeBlocksSet))
-
-              const incomingEdges = workflowEdges.filter(
-                (edge) => edge.target === event.data.blockId
-              )
-              incomingEdges.forEach((edge) => {
-                setEdgeRunStatus(wfId, edge.id, 'success')
-              })
               break
             }
 
@@ -155,6 +204,13 @@ export async function executeWorkflowWithFullLogging(
               setActiveBlocks(wfId, new Set(activeBlocksSet))
 
               setBlockRunStatus(wfId, event.data.blockId, 'success')
+              markOutgoingEdgesFromOutput(
+                event.data.blockId,
+                event.data.output,
+                workflowEdges,
+                wfId,
+                setEdgeRunStatus
+              )
 
               addConsole({
                 input: event.data.input || {},
@@ -194,6 +250,13 @@ export async function executeWorkflowWithFullLogging(
               setActiveBlocks(wfId, new Set(activeBlocksSet))
 
               setBlockRunStatus(wfId, event.data.blockId, 'error')
+              markOutgoingEdgesFromOutput(
+                event.data.blockId,
+                { error: event.data.error },
+                workflowEdges,
+                wfId,
+                setEdgeRunStatus
+              )
 
               addConsole({
                 input: event.data.input || {},

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

@@ -145,7 +145,7 @@ interface PreviewWorkflowProps {
   /** Cursor style to show when hovering the canvas */
   cursorStyle?: 'default' | 'pointer' | 'grab'
   /** Map of executed block IDs to their status for highlighting the execution path */
-  executedBlocks?: Record<string, { status: string }>
+  executedBlocks?: Record<string, { status: string; output?: unknown }>
   /** Currently selected block ID for highlighting */
   selectedBlockId?: string | null
   /** Skips expensive subblock computations for thumbnails/template previews */
@@ -274,9 +274,9 @@ export function PreviewWorkflow({
 
   /** Maps base block IDs to execution data, handling parallel iteration variants (blockId₍n₎). */
   const blockExecutionMap = useMemo(() => {
-    if (!executedBlocks) return new Map<string, { status: string }>()
+    if (!executedBlocks) return new Map<string, { status: string; output?: unknown }>()
 
-    const map = new Map<string, { status: string }>()
+    const map = new Map<string, { status: string; output?: unknown }>()
     for (const [key, value] of Object.entries(executedBlocks)) {
       // Extract base ID (remove iteration suffix like ₍0₎)
       const baseId = key.includes('₍') ? key.split('₍')[0] : key
@@ -451,7 +451,6 @@ export function PreviewWorkflow({
   const edges: Edge[] = useMemo(() => {
     if (!isValidWorkflowState) return []
 
-    /** Edge is green if target executed and source condition met by edge type. */
     const getEdgeExecutionStatus = (edge: {
       source: string
       target: string
@@ -463,17 +462,40 @@ export function PreviewWorkflow({
       if (!targetStatus?.executed) return 'not-executed'
 
       const sourceStatus = getBlockExecutionStatus(edge.source)
-      const { sourceHandle } = edge
+      if (!sourceStatus?.executed) return 'not-executed'
 
-      if (sourceHandle === 'error') {
-        return sourceStatus?.status === 'error' ? 'success' : 'not-executed'
+      const handle = edge.sourceHandle
+      if (!handle) {
+        return sourceStatus.status === 'success' ? 'success' : 'not-executed'
       }
 
-      if (sourceHandle === 'loop-start-source' || sourceHandle === 'parallel-start-source') {
-        return 'success'
+      const sourceOutput = blockExecutionMap.get(edge.source)?.output as
+        | Record<string, any>
+        | undefined
+
+      if (handle.startsWith('condition-')) {
+        const conditionValue = handle.substring('condition-'.length)
+        return sourceOutput?.selectedOption === conditionValue ? 'success' : 'not-executed'
       }
 
-      return sourceStatus?.status === 'success' ? 'success' : 'not-executed'
+      if (handle.startsWith('router-')) {
+        const routeId = handle.substring('router-'.length)
+        return sourceOutput?.selectedRoute === routeId ? 'success' : 'not-executed'
+      }
+
+      switch (handle) {
+        case 'error':
+          return sourceStatus.status === 'error' ? 'error' : 'not-executed'
+        case 'source':
+          return sourceStatus.status === 'success' ? 'success' : 'not-executed'
+        case 'loop-start-source':
+        case 'loop-end-source':
+        case 'parallel-start-source':
+        case 'parallel-end-source':
+          return 'success'
+        default:
+          return sourceStatus.status === 'success' ? 'success' : 'not-executed'
+      }
     }
 
     return (workflowState.edges || []).map((edge) => {

apps/sim/executor/execution/edge-manager.test.ts

@@ -66,11 +66,15 @@ describe('EdgeManager', () => {
       const dag = createMockDAG(nodes)
       const edgeManager = new EdgeManager(dag)
 
-      const readyAfterA = edgeManager.processOutgoingEdges(blockANode, { result: 'done' })
+      const readyAfterA = edgeManager.processOutgoingEdges(blockANode, {
+        result: 'done',
+      })
       expect(readyAfterA).toContain(blockBId)
       expect(readyAfterA).not.toContain(blockCId)
 
-      const readyAfterB = edgeManager.processOutgoingEdges(blockBNode, { result: 'done' })
+      const readyAfterB = edgeManager.processOutgoingEdges(blockBNode, {
+        result: 'done',
+      })
       expect(readyAfterB).toContain(blockCId)
     })
 
@@ -591,7 +595,9 @@ describe('EdgeManager', () => {
 
       function1Node.incomingEdges.add(conditionId)
 
-      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'if' })
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'if',
+      })
       expect(readyNodes).toContain(function1Id)
     })
   })
@@ -977,11 +983,15 @@ describe('EdgeManager', () => {
       const dag = createMockDAG(nodes)
       const edgeManager = new EdgeManager(dag)
 
-      const ready1 = edgeManager.processOutgoingEdges(condition1Node, { selectedOption: 'if' })
+      const ready1 = edgeManager.processOutgoingEdges(condition1Node, {
+        selectedOption: 'if',
+      })
       expect(ready1).toContain(condition2Id)
       expect(ready1).not.toContain(target1Id)
 
-      const ready2 = edgeManager.processOutgoingEdges(condition2Node, { selectedOption: 'else' })
+      const ready2 = edgeManager.processOutgoingEdges(condition2Node, {
+        selectedOption: 'else',
+      })
       expect(ready2).toContain(target1Id)
       expect(ready2).not.toContain(target2Id)
     })
@@ -1394,10 +1404,14 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Path: condition1(if) → condition2(else) → nodeC → sentinel_end
-      const ready1 = edgeManager.processOutgoingEdges(condition1Node, { selectedOption: 'if' })
+      const ready1 = edgeManager.processOutgoingEdges(condition1Node, {
+        selectedOption: 'if',
+      })
       expect(ready1).toContain(condition2Id)
 
-      const ready2 = edgeManager.processOutgoingEdges(condition2Node, { selectedOption: 'else' })
+      const ready2 = edgeManager.processOutgoingEdges(condition2Node, {
+        selectedOption: 'else',
+      })
       expect(ready2).toContain(nodeCId)
 
       const ready3 = edgeManager.processOutgoingEdges(nodeCNode, {})
@@ -1448,7 +1462,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Test else path through diamond
-      const ready1 = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'else' })
+      const ready1 = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else',
+      })
       expect(ready1).toContain(nodeBId)
       expect(ready1).not.toContain(nodeAId)
 
@@ -1509,7 +1525,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Select else - triggers deep cascade deactivation of if path
-      const ready1 = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'else' })
+      const ready1 = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else',
+      })
       expect(ready1).toContain(nodeDId)
 
       const ready2 = edgeManager.processOutgoingEdges(nodeDNode, {})
@@ -1566,7 +1584,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Test middle branch (elseif2)
-      const ready1 = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'elseif2' })
+      const ready1 = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'elseif2',
+      })
       expect(ready1).toContain(nodeCId)
       expect(ready1).not.toContain(nodeAId)
       expect(ready1).not.toContain(nodeBId)
@@ -1629,7 +1649,7 @@ describe('EdgeManager', () => {
       // Scenario: Loop with Function 1 → Condition 1 → Function 2
       // Condition has "if" branch → Function 2
       // Condition has "else" branch → NO connection (dead end)
-      // When else is selected (selectedOption: null), the loop should continue
+      // When else is selected, the loop sentinel should still fire
       //
       // DAG structure:
       //   sentinel_start → func1 → condition → (if) → func2 → sentinel_end
@@ -1637,11 +1657,12 @@ describe('EdgeManager', () => {
       //   sentinel_end → (loop_continue) → sentinel_start
       //
       // When condition takes else with no edge:
-      // - selectedOption: null (no condition matches)
+      // - selectedOption is set (condition made a routing decision)
       // - The "if" edge gets deactivated
       // - func2 has no other active incoming edges, so edge to sentinel_end gets deactivated
-      // - sentinel_end has no active incoming edges and should become ready
+      // - sentinel_end is the enclosing loop's sentinel and should become ready
 
+      const loopId = 'loop-1'
       const sentinelStartId = 'sentinel-start'
       const sentinelEndId = 'sentinel-end'
       const func1Id = 'func1'
@@ -1649,14 +1670,21 @@ describe('EdgeManager', () => {
       const func2Id = 'func2'
 
       const sentinelStartNode = createMockNode(sentinelStartId, [{ target: func1Id }])
+      sentinelStartNode.metadata = { isSentinel: true, sentinelType: 'start', loopId }
+
       const func1Node = createMockNode(func1Id, [{ target: conditionId }], [sentinelStartId])
-      // Condition only has "if" branch, no "else" edge (dead end)
+      func1Node.metadata = { loopId, isLoopNode: true }
+
       const conditionNode = createMockNode(
         conditionId,
         [{ target: func2Id, sourceHandle: 'condition-if' }],
         [func1Id]
       )
+      conditionNode.metadata = { loopId, isLoopNode: true }
+
       const func2Node = createMockNode(func2Id, [{ target: sentinelEndId }], [conditionId])
+      func2Node.metadata = { loopId, isLoopNode: true }
+
       const sentinelEndNode = createMockNode(
         sentinelEndId,
         [
@@ -1665,6 +1693,8 @@ describe('EdgeManager', () => {
         ],
         [func2Id]
       )
+      sentinelEndNode.metadata = { isSentinel: true, sentinelType: 'end', loopId }
+
       const afterLoopNode = createMockNode('after-loop', [], [sentinelEndId])
 
       const nodes = new Map<string, DAGNode>([
@@ -1679,22 +1709,17 @@ describe('EdgeManager', () => {
       const dag = createMockDAG(nodes)
       const edgeManager = new EdgeManager(dag)
 
-      // Simulate execution: sentinel_start → func1 → condition
-      // Clear incoming edges as execution progresses (simulating normal flow)
       func1Node.incomingEdges.clear()
       conditionNode.incomingEdges.clear()
 
-      // Condition takes "else" but there's no else edge
-      // selectedOption: null means no condition branch matches
+      // Condition selects dead-end else (selectedOption is set — routing decision made)
+      // but it's inside the loop, so the enclosing sentinel should still fire
       const ready = edgeManager.processOutgoingEdges(conditionNode, {
-        selectedOption: null,
-        conditionResult: false,
+        selectedOption: 'else-id',
+        conditionResult: true,
         selectedPath: null,
       })
 
-      // The "if" edge to func2 should be deactivated
-      // func2 has no other incoming edges, so its edge to sentinel_end gets deactivated
-      // sentinel_end has no active incoming edges and should be ready
       expect(ready).toContain(sentinelEndId)
     })
 
@@ -1763,11 +1788,12 @@ describe('EdgeManager', () => {
       //                      → (else) → [nothing]
       //                                            → (else) → [nothing]
       //
-      // When condition1 takes if, then condition2 takes else:
+      // When condition1 takes if, then condition2 takes else (dead-end):
       // - condition2's "if" edge to func gets deactivated
       // - func's edge to sentinel_end gets deactivated
-      // - sentinel_end should become ready
+      // - sentinel_end is the enclosing loop's sentinel and should become ready
 
+      const loopId = 'loop-1'
       const sentinelStartId = 'sentinel-start'
       const sentinelEndId = 'sentinel-end'
       const condition1Id = 'condition1'
@@ -1775,22 +1801,31 @@ describe('EdgeManager', () => {
       const funcId = 'func'
 
       const sentinelStartNode = createMockNode(sentinelStartId, [{ target: condition1Id }])
+      sentinelStartNode.metadata = { isSentinel: true, sentinelType: 'start', loopId }
+
       const condition1Node = createMockNode(
         condition1Id,
         [{ target: condition2Id, sourceHandle: 'condition-if' }],
         [sentinelStartId]
       )
+      condition1Node.metadata = { loopId, isLoopNode: true }
+
       const condition2Node = createMockNode(
         condition2Id,
         [{ target: funcId, sourceHandle: 'condition-if' }],
         [condition1Id]
       )
+      condition2Node.metadata = { loopId, isLoopNode: true }
+
       const funcNode = createMockNode(funcId, [{ target: sentinelEndId }], [condition2Id])
+      funcNode.metadata = { loopId, isLoopNode: true }
+
       const sentinelEndNode = createMockNode(
         sentinelEndId,
         [{ target: sentinelStartId, sourceHandle: 'loop_continue' }],
         [funcId]
       )
+      sentinelEndNode.metadata = { isSentinel: true, sentinelType: 'end', loopId }
 
       const nodes = new Map<string, DAGNode>([
         [sentinelStartId, sentinelStartNode],
@@ -1803,22 +1838,95 @@ describe('EdgeManager', () => {
       const dag = createMockDAG(nodes)
       const edgeManager = new EdgeManager(dag)
 
-      // Clear incoming edges as execution progresses
       condition1Node.incomingEdges.clear()
 
-      // condition1 takes "if" - condition2 becomes ready
-      const ready1 = edgeManager.processOutgoingEdges(condition1Node, { selectedOption: 'if' })
+      const ready1 = edgeManager.processOutgoingEdges(condition1Node, {
+        selectedOption: 'if',
+      })
       expect(ready1).toContain(condition2Id)
 
       condition2Node.incomingEdges.clear()
 
-      // condition2 takes "else" (dead end)
-      const ready2 = edgeManager.processOutgoingEdges(condition2Node, { selectedOption: null })
+      // condition2 selects dead-end else (selectedOption set — routing decision made)
+      const ready2 = edgeManager.processOutgoingEdges(condition2Node, {
+        selectedOption: 'else-id',
+      })
 
-      // sentinel_end should be ready because all paths to it are deactivated
+      // sentinel_end is the enclosing loop's sentinel and should be ready
       expect(ready2).toContain(sentinelEndId)
     })
 
+    it('should not fire nested subflow sentinel when condition inside outer loop hits dead-end', () => {
+      // Scenario: outer loop contains condition → (if) → inner loop → sentinel_end
+      //                                        → (else) → [dead end]
+      //
+      // When condition selects dead-end else:
+      // - The outer loop's sentinel should fire (enclosing subflow)
+      // - The inner loop's sentinel should NOT fire (downstream subflow)
+
+      const outerLoopId = 'outer-loop'
+      const innerLoopId = 'inner-loop'
+      const outerStartId = 'outer-start'
+      const outerEndId = 'outer-end'
+      const conditionId = 'condition'
+      const innerStartId = 'inner-start'
+      const innerBodyId = 'inner-body'
+      const innerEndId = 'inner-end'
+
+      const outerStartNode = createMockNode(outerStartId, [{ target: conditionId }])
+      outerStartNode.metadata = { isSentinel: true, sentinelType: 'start', loopId: outerLoopId }
+
+      const conditionNode = createMockNode(
+        conditionId,
+        [{ target: innerStartId, sourceHandle: 'condition-if' }],
+        [outerStartId]
+      )
+      conditionNode.metadata = { loopId: outerLoopId, isLoopNode: true }
+
+      const innerStartNode = createMockNode(innerStartId, [{ target: innerBodyId }], [conditionId])
+      innerStartNode.metadata = { isSentinel: true, sentinelType: 'start', loopId: innerLoopId }
+
+      const innerBodyNode = createMockNode(innerBodyId, [{ target: innerEndId }], [innerStartId])
+      innerBodyNode.metadata = { loopId: innerLoopId, isLoopNode: true }
+
+      const innerEndNode = createMockNode(
+        innerEndId,
+        [{ target: outerEndId, sourceHandle: 'loop_exit' }],
+        [innerBodyId]
+      )
+      innerEndNode.metadata = { isSentinel: true, sentinelType: 'end', loopId: innerLoopId }
+
+      const outerEndNode = createMockNode(
+        outerEndId,
+        [{ target: outerStartId, sourceHandle: 'loop_continue' }],
+        [innerEndId]
+      )
+      outerEndNode.metadata = { isSentinel: true, sentinelType: 'end', loopId: outerLoopId }
+
+      const nodes = new Map<string, DAGNode>([
+        [outerStartId, outerStartNode],
+        [conditionId, conditionNode],
+        [innerStartId, innerStartNode],
+        [innerBodyId, innerBodyNode],
+        [innerEndId, innerEndNode],
+        [outerEndId, outerEndNode],
+      ])
+
+      const dag = createMockDAG(nodes)
+      const edgeManager = new EdgeManager(dag)
+
+      conditionNode.incomingEdges.clear()
+
+      const ready = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else-id',
+      })
+
+      // Outer loop sentinel should fire (condition is inside outer loop)
+      expect(ready).toContain(outerEndId)
+      // Inner loop sentinel should NOT fire (it's a downstream subflow)
+      expect(ready).not.toContain(innerEndId)
+    })
+
     it('should NOT execute intermediate nodes in long cascade chains (2+ hops)', () => {
       // Regression test: When condition hits dead-end with 2+ intermediate nodes,
       // only sentinel_end should be ready, NOT the intermediate nodes.
@@ -1922,7 +2030,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Select else path
-      const ready1 = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'else' })
+      const ready1 = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else',
+      })
       expect(ready1).toContain(nodeBId)
       expect(ready1).not.toContain(nodeAId)
 
@@ -1968,7 +2078,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // When selectedOption is null, the cascade deactivation makes parallel_end ready
-      const ready = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: null })
+      const ready = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: null,
+      })
       expect(ready).toContain(parallelEndId)
     })
 
@@ -2039,11 +2151,15 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Branch 1: condition1 selects else
-      const ready1 = edgeManager.processOutgoingEdges(condition1Node, { selectedOption: 'else' })
+      const ready1 = edgeManager.processOutgoingEdges(condition1Node, {
+        selectedOption: 'else',
+      })
       expect(ready1).toContain(nodeBId)
 
       // Branch 2: condition2 selects if
-      const ready2 = edgeManager.processOutgoingEdges(condition2Node, { selectedOption: 'if' })
+      const ready2 = edgeManager.processOutgoingEdges(condition2Node, {
+        selectedOption: 'if',
+      })
       expect(ready2).toContain(nodeCId)
 
       // Both complete
@@ -2200,7 +2316,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // nodeA errors
-      const ready1 = edgeManager.processOutgoingEdges(nodeANode, { error: 'Something failed' })
+      const ready1 = edgeManager.processOutgoingEdges(nodeANode, {
+        error: 'Something failed',
+      })
       expect(ready1).toContain(errorNodeId)
       expect(ready1).not.toContain(successNodeId)
 
@@ -2289,7 +2407,9 @@ describe('EdgeManager', () => {
       edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'if' })
       edgeManager.processOutgoingEdges(nodeANode, {})
 
-      const ready2 = edgeManager.processOutgoingEdges(loopEndNode, { selectedRoute: 'loop_exit' })
+      const ready2 = edgeManager.processOutgoingEdges(loopEndNode, {
+        selectedRoute: 'loop_exit',
+      })
       expect(ready2).toContain(parallelEndId)
 
       const ready3 = edgeManager.processOutgoingEdges(parallelEndNode, {
@@ -2413,7 +2533,9 @@ describe('EdgeManager', () => {
       const dag = createMockDAG(nodes)
       const edgeManager = new EdgeManager(dag)
 
-      const successReady = edgeManager.processOutgoingEdges(sourceNode, { result: 'ok' })
+      const successReady = edgeManager.processOutgoingEdges(sourceNode, {
+        result: 'ok',
+      })
       expect(successReady).toContain(targetId)
     })
   })
@@ -2472,7 +2594,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Condition selects "else" branch, deactivating the "if" branch (which contains the loop)
-      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'else' })
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else',
+      })
 
       // Only otherBranch should be ready
       expect(readyNodes).toContain(otherBranchId)
@@ -2539,7 +2663,9 @@ describe('EdgeManager', () => {
       const edgeManager = new EdgeManager(dag)
 
       // Condition selects "else" branch
-      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, { selectedOption: 'else' })
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else',
+      })
 
       expect(readyNodes).toContain(otherBranchId)
       expect(readyNodes).not.toContain(parallelStartId)
@@ -2626,6 +2752,171 @@ describe('EdgeManager', () => {
       expect(readyNodes).not.toContain(afterLoopId)
     })
 
+    it('should not queue sentinel-end when condition selects no-edge path (loop)', () => {
+      // Bug scenario: condition → (if) → sentinel_start → body → sentinel_end → (loop_exit) → after_loop
+      //                         → (else) → [NO outgoing edge]
+      // Condition evaluates false, else is selected but has no edge.
+      // With selectedOption set (routing decision made), cascadeTargets should NOT be queued.
+      // Previously sentinel_end was queued via cascadeTargets, causing downstream blocks to execute.
+
+      const conditionId = 'condition'
+      const sentinelStartId = 'sentinel-start'
+      const loopBodyId = 'loop-body'
+      const sentinelEndId = 'sentinel-end'
+      const afterLoopId = 'after-loop'
+
+      const conditionNode = createMockNode(conditionId, [
+        { target: sentinelStartId, sourceHandle: 'condition-if-id' },
+      ])
+
+      const sentinelStartNode = createMockNode(
+        sentinelStartId,
+        [{ target: loopBodyId }],
+        [conditionId]
+      )
+
+      const loopBodyNode = createMockNode(
+        loopBodyId,
+        [{ target: sentinelEndId }],
+        [sentinelStartId]
+      )
+
+      const sentinelEndNode = createMockNode(
+        sentinelEndId,
+        [
+          { target: sentinelStartId, sourceHandle: 'loop_continue' },
+          { target: afterLoopId, sourceHandle: 'loop_exit' },
+        ],
+        [loopBodyId]
+      )
+
+      const afterLoopNode = createMockNode(afterLoopId, [], [sentinelEndId])
+
+      const nodes = new Map<string, DAGNode>([
+        [conditionId, conditionNode],
+        [sentinelStartId, sentinelStartNode],
+        [loopBodyId, loopBodyNode],
+        [sentinelEndId, sentinelEndNode],
+        [afterLoopId, afterLoopNode],
+      ])
+
+      const dag = createMockDAG(nodes)
+      const edgeManager = new EdgeManager(dag)
+
+      // Condition selected else, but else has no outgoing edge.
+      // selectedOption is set (routing decision was made).
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else-id',
+      })
+
+      // Nothing should be queued -- the entire branch is intentionally dead
+      expect(readyNodes).not.toContain(sentinelStartId)
+      expect(readyNodes).not.toContain(loopBodyId)
+      expect(readyNodes).not.toContain(sentinelEndId)
+      expect(readyNodes).not.toContain(afterLoopId)
+      expect(readyNodes).toHaveLength(0)
+    })
+
+    it('should not queue sentinel-end when condition selects no-edge path (parallel)', () => {
+      // Same scenario with parallel instead of loop
+      const conditionId = 'condition'
+      const parallelStartId = 'parallel-start'
+      const branchId = 'branch-0'
+      const parallelEndId = 'parallel-end'
+      const afterParallelId = 'after-parallel'
+
+      const conditionNode = createMockNode(conditionId, [
+        { target: parallelStartId, sourceHandle: 'condition-if-id' },
+      ])
+
+      const parallelStartNode = createMockNode(
+        parallelStartId,
+        [{ target: branchId }],
+        [conditionId]
+      )
+
+      const branchNode = createMockNode(
+        branchId,
+        [{ target: parallelEndId, sourceHandle: 'parallel_exit' }],
+        [parallelStartId]
+      )
+
+      const parallelEndNode = createMockNode(
+        parallelEndId,
+        [{ target: afterParallelId, sourceHandle: 'parallel_exit' }],
+        [branchId]
+      )
+
+      const afterParallelNode = createMockNode(afterParallelId, [], [parallelEndId])
+
+      const nodes = new Map<string, DAGNode>([
+        [conditionId, conditionNode],
+        [parallelStartId, parallelStartNode],
+        [branchId, branchNode],
+        [parallelEndId, parallelEndNode],
+        [afterParallelId, afterParallelNode],
+      ])
+
+      const dag = createMockDAG(nodes)
+      const edgeManager = new EdgeManager(dag)
+
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: 'else-id',
+      })
+
+      expect(readyNodes).not.toContain(parallelStartId)
+      expect(readyNodes).not.toContain(branchId)
+      expect(readyNodes).not.toContain(parallelEndId)
+      expect(readyNodes).not.toContain(afterParallelId)
+      expect(readyNodes).toHaveLength(0)
+    })
+
+    it('should still queue sentinel-end inside loop when no condition matches (true dead-end)', () => {
+      // Contrast: condition INSIDE a loop with selectedOption null (no match, no routing decision).
+      // This is a true dead-end where cascadeTargets SHOULD fire so the loop sentinel can handle exit.
+
+      const sentinelStartId = 'sentinel-start'
+      const sentinelEndId = 'sentinel-end'
+      const conditionId = 'condition'
+      const nodeAId = 'node-a'
+
+      const sentinelStartNode = createMockNode(sentinelStartId, [{ target: conditionId }])
+      const conditionNode = createMockNode(
+        conditionId,
+        [{ target: nodeAId, sourceHandle: 'condition-if' }],
+        [sentinelStartId]
+      )
+      const nodeANode = createMockNode(nodeAId, [{ target: sentinelEndId }], [conditionId])
+      const sentinelEndNode = createMockNode(
+        sentinelEndId,
+        [
+          { target: sentinelStartId, sourceHandle: 'loop_continue' },
+          { target: 'after-loop', sourceHandle: 'loop_exit' },
+        ],
+        [nodeAId]
+      )
+
+      const nodes = new Map<string, DAGNode>([
+        [sentinelStartId, sentinelStartNode],
+        [conditionId, conditionNode],
+        [nodeAId, nodeANode],
+        [sentinelEndId, sentinelEndNode],
+      ])
+
+      const dag = createMockDAG(nodes)
+      const edgeManager = new EdgeManager(dag)
+
+      conditionNode.incomingEdges.clear()
+
+      // selectedOption: null → no routing decision, true dead-end
+      const readyNodes = edgeManager.processOutgoingEdges(conditionNode, {
+        selectedOption: null,
+      })
+
+      // sentinel-end SHOULD be queued (true dead-end inside loop)
+      expect(readyNodes).toContain(sentinelEndId)
+    })
+
     it('should still correctly handle normal loop exit (not deactivate when loop runs)', () => {
       // When a loop actually executes and exits normally, after_loop should become ready
       const sentinelStartId = 'sentinel-start'

apps/sim/executor/execution/edge-manager.ts

@@ -69,15 +69,23 @@ export class EdgeManager {
       }
     }
 
+    const isDeadEnd = activatedTargets.length === 0
+    const isRoutedDeadEnd = isDeadEnd && !!(output.selectedOption || output.selectedRoute)
+
     for (const targetId of cascadeTargets) {
       if (!readyNodes.includes(targetId) && !activatedTargets.includes(targetId)) {
-        // Only queue cascade terminal control nodes when ALL outgoing edges from the
-        // current node were deactivated (dead-end scenario). When some edges are
-        // activated, terminal control nodes on deactivated branches should NOT be
-        // queued - they will be reached through the normal activated path's completion.
-        // This prevents loop/parallel sentinels on fully deactivated paths (e.g., an
-        // upstream condition took a different branch) from being spuriously executed.
-        if (activatedTargets.length === 0 && this.isTargetReady(targetId)) {
+        if (!isDeadEnd || !this.isTargetReady(targetId)) continue
+
+        if (isRoutedDeadEnd) {
+          // A condition/router deliberately selected a dead-end path.
+          // Only queue the sentinel if it belongs to the SAME subflow as the
+          // current node (the condition is inside the loop/parallel and the
+          // loop still needs to continue/exit). Downstream subflow sentinels
+          // should NOT fire.
+          if (this.isEnclosingSentinel(node, targetId)) {
+            readyNodes.push(targetId)
+          }
+        } else {
           readyNodes.push(targetId)
         }
       }
@@ -145,6 +153,27 @@ export class EdgeManager {
     return targetNode ? this.isNodeReady(targetNode) : false
   }
 
+  /**
+   * Checks if the cascade target sentinel belongs to the same subflow as the source node.
+   * A condition inside a loop that hits a dead-end should still allow the enclosing
+   * loop's sentinel to fire so the loop can continue or exit.
+   */
+  private isEnclosingSentinel(sourceNode: DAGNode, sentinelId: string): boolean {
+    const sentinel = this.dag.nodes.get(sentinelId)
+    if (!sentinel?.metadata.isSentinel) return false
+
+    const sourceLoopId = sourceNode.metadata.loopId
+    const sourceParallelId = sourceNode.metadata.parallelId
+    const sentinelLoopId = sentinel.metadata.loopId
+    const sentinelParallelId = sentinel.metadata.parallelId
+
+    if (sourceLoopId && sentinelLoopId && sourceLoopId === sentinelLoopId) return true
+    if (sourceParallelId && sentinelParallelId && sourceParallelId === sentinelParallelId)
+      return true
+
+    return false
+  }
+
   private isLoopEdge(handle?: string): boolean {
     return (
       handle === EDGE.LOOP_CONTINUE ||

apps/sim/executor/handlers/condition/condition-handler.test.ts

@@ -555,7 +555,7 @@ describe('ConditionBlockHandler', () => {
   })
 
   describe('Condition with no outgoing edge', () => {
-    it('should return null path when condition matches but has no edge', async () => {
+    it('should set selectedOption when condition matches but has no edge', async () => {
       const conditions = [
         { id: 'cond1', title: 'if', value: 'true' },
         { id: 'else1', title: 'else', value: '' },
@@ -570,9 +570,52 @@ describe('ConditionBlockHandler', () => {
 
       const result = await handler.execute(mockContext, mockBlock, inputs)
 
-      // Condition matches but no edge for it
-      expect((result as any).conditionResult).toBe(false)
+      expect((result as any).conditionResult).toBe(true)
       expect((result as any).selectedPath).toBeNull()
+      expect((result as any).selectedOption).toBe('cond1')
+      expect(mockContext.decisions.condition.get(mockBlock.id)).toBe('cond1')
+    })
+
+    it('should set selectedOption when else is selected but has no edge', async () => {
+      const conditions = [
+        { id: 'cond1', title: 'if', value: 'false' },
+        { id: 'else1', title: 'else', value: '' },
+      ]
+      const inputs = { conditions: JSON.stringify(conditions) }
+
+      // Only the if branch has an edge; else has no outgoing connection
+      mockContext.workflow!.connections = [
+        { source: mockSourceBlock.id, target: mockBlock.id },
+        { source: mockBlock.id, target: mockTargetBlock1.id, sourceHandle: 'condition-cond1' },
+      ]
+
+      const result = await handler.execute(mockContext, mockBlock, inputs)
+
+      expect((result as any).conditionResult).toBe(true)
+      expect((result as any).selectedPath).toBeNull()
+      expect((result as any).selectedOption).toBe('else1')
+      expect(mockContext.decisions.condition.get(mockBlock.id)).toBe('else1')
+    })
+
+    it('should deactivate if-path when else is selected with no edge', async () => {
+      const conditions = [
+        { id: 'cond1', title: 'if', value: 'context.value > 100' },
+        { id: 'else1', title: 'else', value: '' },
+      ]
+      const inputs = { conditions: JSON.stringify(conditions) }
+
+      // Only the if branch has an edge to a loop; else has nothing
+      mockContext.workflow!.connections = [
+        { source: mockSourceBlock.id, target: mockBlock.id },
+        { source: mockBlock.id, target: mockTargetBlock1.id, sourceHandle: 'condition-cond1' },
+      ]
+
+      const result = await handler.execute(mockContext, mockBlock, inputs)
+
+      // Else was selected (value 10 is not > 100), so selectedOption should be 'else1'
+      // This allows the edge manager to deactivate the cond1 edge
+      expect((result as any).selectedOption).toBe('else1')
+      expect((result as any).conditionResult).toBe(true)
     })
   })
 
@@ -602,6 +645,67 @@ describe('ConditionBlockHandler', () => {
     })
   })
 
+  describe('Source output filtering', () => {
+    it('should not propagate error field from source block output', async () => {
+      ;(mockContext.blockStates as any).set(mockSourceBlock.id, {
+        output: { value: 10, text: 'hello', error: 'upstream block failed' },
+        executed: true,
+        executionTime: 100,
+      })
+
+      const conditions = [
+        { id: 'cond1', title: 'if', value: 'context.value > 5' },
+        { id: 'else1', title: 'else', value: '' },
+      ]
+      const inputs = { conditions: JSON.stringify(conditions) }
+
+      const result = await handler.execute(mockContext, mockBlock, inputs)
+
+      expect((result as any).conditionResult).toBe(true)
+      expect((result as any).selectedOption).toBe('cond1')
+      expect(result).not.toHaveProperty('error')
+    })
+
+    it('should not propagate _pauseMetadata from source block output', async () => {
+      ;(mockContext.blockStates as any).set(mockSourceBlock.id, {
+        output: { value: 10, _pauseMetadata: { contextId: 'abc' } },
+        executed: true,
+        executionTime: 100,
+      })
+
+      const conditions = [
+        { id: 'cond1', title: 'if', value: 'context.value > 5' },
+        { id: 'else1', title: 'else', value: '' },
+      ]
+      const inputs = { conditions: JSON.stringify(conditions) }
+
+      const result = await handler.execute(mockContext, mockBlock, inputs)
+
+      expect((result as any).conditionResult).toBe(true)
+      expect(result).not.toHaveProperty('_pauseMetadata')
+    })
+
+    it('should still pass through non-control fields from source output', async () => {
+      ;(mockContext.blockStates as any).set(mockSourceBlock.id, {
+        output: { value: 10, text: 'hello', customData: { nested: true } },
+        executed: true,
+        executionTime: 100,
+      })
+
+      const conditions = [
+        { id: 'cond1', title: 'if', value: 'context.value > 5' },
+        { id: 'else1', title: 'else', value: '' },
+      ]
+      const inputs = { conditions: JSON.stringify(conditions) }
+
+      const result = await handler.execute(mockContext, mockBlock, inputs)
+
+      expect((result as any).value).toBe(10)
+      expect((result as any).text).toBe('hello')
+      expect((result as any).customData).toEqual({ nested: true })
+    })
+  })
+
   describe('Virtual block ID handling', () => {
     it('should use currentVirtualBlockId for decision key when available', async () => {
       mockContext.currentVirtualBlockId = 'virtual-block-123'

apps/sim/executor/handlers/condition/condition-handler.ts

@@ -108,9 +108,7 @@ export class ConditionBlockHandler implements BlockHandler {
     const evalContext = this.buildEvaluationContext(ctx, sourceBlockId)
     const rawSourceOutput = sourceBlockId ? ctx.blockStates.get(sourceBlockId)?.output : null
 
-    // Filter out _pauseMetadata from source output to prevent the engine from
-    // thinking this block is pausing (it was already resumed by the HITL block)
-    const sourceOutput = this.filterPauseMetadata(rawSourceOutput)
+    const sourceOutput = this.filterSourceOutput(rawSourceOutput)
 
     const outgoingConnections = ctx.workflow?.connections.filter(
       (conn) => conn.source === baseBlockId
@@ -124,7 +122,7 @@ export class ConditionBlockHandler implements BlockHandler {
       block.id
     )
 
-    if (!selectedConnection || !selectedCondition) {
+    if (!selectedCondition) {
       return {
         ...((sourceOutput as any) || {}),
         conditionResult: false,
@@ -133,6 +131,17 @@ export class ConditionBlockHandler implements BlockHandler {
       }
     }
 
+    if (!selectedConnection) {
+      const decisionKey = ctx.currentVirtualBlockId || block.id
+      ctx.decisions.condition.set(decisionKey, selectedCondition.id)
+      return {
+        ...((sourceOutput as any) || {}),
+        conditionResult: true,
+        selectedPath: null,
+        selectedOption: selectedCondition.id,
+      }
+    }
+
     const targetBlock = ctx.workflow?.blocks.find((b) => b.id === selectedConnection?.target)
     if (!targetBlock) {
       throw new Error(`Target block ${selectedConnection?.target} not found`)
@@ -153,11 +162,11 @@ export class ConditionBlockHandler implements BlockHandler {
     }
   }
 
-  private filterPauseMetadata(output: any): any {
+  private filterSourceOutput(output: any): any {
     if (!output || typeof output !== 'object') {
       return output
     }
-    const { _pauseMetadata, ...rest } = output
+    const { _pauseMetadata, error, ...rest } = output
     return rest
   }
 
@@ -223,8 +232,7 @@ export class ConditionBlockHandler implements BlockHandler {
           if (connection) {
             return { selectedConnection: connection, selectedCondition: condition }
           }
-          // Condition is true but has no outgoing edge - branch ends gracefully
-          return { selectedConnection: null, selectedCondition: null }
+          return { selectedConnection: null, selectedCondition: condition }
         }
       } catch (error: any) {
         logger.error(`Failed to evaluate condition "${condition.title}": ${error.message}`)
@@ -238,7 +246,7 @@ export class ConditionBlockHandler implements BlockHandler {
       if (elseConnection) {
         return { selectedConnection: elseConnection, selectedCondition: elseCondition }
       }
-      return { selectedConnection: null, selectedCondition: null }
+      return { selectedConnection: null, selectedCondition: elseCondition }
     }
 
     return { selectedConnection: null, selectedCondition: null }

apps/sim/executor/orchestrators/loop.ts

@@ -21,6 +21,7 @@ import {
   buildParallelSentinelStartId,
   buildSentinelEndId,
   buildSentinelStartId,
+  emitEmptySubflowEvents,
   extractBaseBlockId,
   resolveArrayInput,
   validateMaxCount,
@@ -596,6 +597,7 @@ export class LoopOrchestrator {
       if (!scope.items || scope.items.length === 0) {
         logger.info('ForEach loop has empty collection, skipping loop body', { loopId })
         this.state.setBlockOutput(loopId, { results: [] }, DEFAULTS.EXECUTION_TIME)
+        emitEmptySubflowEvents(ctx, loopId, 'loop', this.contextExtensions)
         return false
       }
       return true
@@ -605,6 +607,7 @@ export class LoopOrchestrator {
       if (scope.maxIterations === 0) {
         logger.info('For loop has 0 iterations, skipping loop body', { loopId })
         this.state.setBlockOutput(loopId, { results: [] }, DEFAULTS.EXECUTION_TIME)
+        emitEmptySubflowEvents(ctx, loopId, 'loop', this.contextExtensions)
         return false
       }
       return true
@@ -617,6 +620,8 @@ export class LoopOrchestrator {
     if (scope.loopType === 'while') {
       if (!scope.condition) {
         logger.warn('No condition defined for while loop', { loopId })
+        this.state.setBlockOutput(loopId, { results: [] }, DEFAULTS.EXECUTION_TIME)
+        emitEmptySubflowEvents(ctx, loopId, 'loop', this.contextExtensions)
         return false
       }
 
@@ -627,6 +632,11 @@ export class LoopOrchestrator {
         result,
       })
 
+      if (!result) {
+        this.state.setBlockOutput(loopId, { results: [] }, DEFAULTS.EXECUTION_TIME)
+        emitEmptySubflowEvents(ctx, loopId, 'loop', this.contextExtensions)
+      }
+
       return result
     }
 

apps/sim/executor/orchestrators/parallel.ts

@@ -13,6 +13,7 @@ import { buildContainerIterationContext } from '@/executor/utils/iteration-conte
 import { ParallelExpander } from '@/executor/utils/parallel-expansion'
 import {
   addSubflowErrorLog,
+  emitEmptySubflowEvents,
   extractBranchIndex,
   resolveArrayInput,
   validateMaxCount,
@@ -108,6 +109,8 @@ export class ParallelOrchestrator {
 
       this.state.setBlockOutput(parallelId, { results: [] })
 
+      emitEmptySubflowEvents(ctx, parallelId, 'parallel', this.contextExtensions)
+
       logger.info('Parallel scope initialized with empty distribution, skipping body', {
         parallelId,
         branchCount: 0,

apps/sim/executor/utils/subflow-utils.ts

@@ -1,6 +1,7 @@
-import { LOOP, PARALLEL, REFERENCE } from '@/executor/constants'
+import { DEFAULTS, LOOP, PARALLEL, REFERENCE } from '@/executor/constants'
 import type { ContextExtensions } from '@/executor/execution/types'
 import { type BlockLog, type ExecutionContext, getNextExecutionOrder } from '@/executor/types'
+import { buildContainerIterationContext } from '@/executor/utils/iteration-context'
 import type { VariableResolver } from '@/executor/variables/resolver'
 
 const BRANCH_PATTERN = new RegExp(`${PARALLEL.BRANCH.PREFIX}\\d+${PARALLEL.BRANCH.SUFFIX}$`)
@@ -309,3 +310,54 @@ export function addSubflowErrorLog(
     })
   }
 }
+
+/**
+ * Emits block log + SSE events for a loop/parallel that was skipped due to an
+ * empty collection or false initial condition. This ensures the container block
+ * appears in terminal logs, execution snapshots, and edge highlighting.
+ */
+export function emitEmptySubflowEvents(
+  ctx: ExecutionContext,
+  blockId: string,
+  blockType: 'loop' | 'parallel',
+  contextExtensions: ContextExtensions | null
+): void {
+  const now = new Date().toISOString()
+  const executionOrder = getNextExecutionOrder(ctx)
+  const output = { results: [] }
+  const block = ctx.workflow?.blocks.find((b) => b.id === blockId)
+  const blockName = block?.metadata?.name ?? blockType
+  const iterationContext = buildContainerIterationContext(ctx, blockId)
+
+  ctx.blockLogs.push({
+    blockId,
+    blockName,
+    blockType,
+    startedAt: now,
+    endedAt: now,
+    durationMs: DEFAULTS.EXECUTION_TIME,
+    success: true,
+    output,
+    executionOrder,
+  })
+
+  if (contextExtensions?.onBlockStart) {
+    contextExtensions.onBlockStart(blockId, blockName, blockType, executionOrder)
+  }
+
+  if (contextExtensions?.onBlockComplete) {
+    contextExtensions.onBlockComplete(
+      blockId,
+      blockName,
+      blockType,
+      {
+        output,
+        executionTime: DEFAULTS.EXECUTION_TIME,
+        startedAt: now,
+        executionOrder,
+        endedAt: now,
+      },
+      iterationContext
+    )
+  }
+}

apps/sim/lib/logs/execution/trace-spans/trace-spans.ts

@@ -761,9 +761,17 @@ function groupIterationBlocksRecursive(
     }
   }
 
-  // Non-iteration spans that aren't consumed container sentinels go straight to result
+  const containerIdsWithIterations = new Set<string>()
+  for (const span of iterationSpans) {
+    const outermost = getOutermostContainer(span)
+    if (outermost) containerIdsWithIterations.add(outermost.containerId)
+  }
+
   const nonContainerSpans = nonIterationSpans.filter(
-    (span) => (span.type !== 'parallel' && span.type !== 'loop') || span.status === 'error'
+    (span) =>
+      (span.type !== 'parallel' && span.type !== 'loop') ||
+      span.status === 'error' ||
+      (span.blockId && !containerIdsWithIterations.has(span.blockId))
   )
 
   if (iterationSpans.length === 0) {

apps/sim/lib/workflows/migrations/subblock-migrations.test.ts

@@ -0,0 +1,183 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import type { BlockState } from '@/stores/workflows/workflow/types'
+import { migrateSubblockIds } from './subblock-migrations'
+
+function makeBlock(overrides: Partial<BlockState> & { type: string }): BlockState {
+  return {
+    id: 'block-1',
+    name: 'Test',
+    position: { x: 0, y: 0 },
+    subBlocks: {},
+    outputs: {},
+    enabled: true,
+    ...overrides,
+  } as BlockState
+}
+
+describe('migrateSubblockIds', () => {
+  describe('knowledge block', () => {
+    it('should rename knowledgeBaseId to knowledgeBaseSelector', () => {
+      const input: Record<string, BlockState> = {
+        b1: makeBlock({
+          type: 'knowledge',
+          subBlocks: {
+            operation: { id: 'operation', type: 'dropdown', value: 'search' },
+            knowledgeBaseId: {
+              id: 'knowledgeBaseId',
+              type: 'knowledge-base-selector',
+              value: 'kb-uuid-123',
+            },
+          },
+        }),
+      }
+
+      const { blocks, migrated } = migrateSubblockIds(input)
+
+      expect(migrated).toBe(true)
+      expect(blocks['b1'].subBlocks['knowledgeBaseSelector']).toEqual({
+        id: 'knowledgeBaseSelector',
+        type: 'knowledge-base-selector',
+        value: 'kb-uuid-123',
+      })
+      expect(blocks['b1'].subBlocks['knowledgeBaseId']).toBeUndefined()
+      expect(blocks['b1'].subBlocks['operation'].value).toBe('search')
+    })
+
+    it('should prefer new key when both old and new exist', () => {
+      const input: Record<string, BlockState> = {
+        b1: makeBlock({
+          type: 'knowledge',
+          subBlocks: {
+            knowledgeBaseId: {
+              id: 'knowledgeBaseId',
+              type: 'knowledge-base-selector',
+              value: 'stale-kb',
+            },
+            knowledgeBaseSelector: {
+              id: 'knowledgeBaseSelector',
+              type: 'knowledge-base-selector',
+              value: 'fresh-kb',
+            },
+          },
+        }),
+      }
+
+      const { blocks, migrated } = migrateSubblockIds(input)
+
+      expect(migrated).toBe(true)
+      expect(blocks['b1'].subBlocks['knowledgeBaseSelector'].value).toBe('fresh-kb')
+      expect(blocks['b1'].subBlocks['knowledgeBaseId']).toBeUndefined()
+    })
+
+    it('should not touch blocks that already use the new key', () => {
+      const input: Record<string, BlockState> = {
+        b1: makeBlock({
+          type: 'knowledge',
+          subBlocks: {
+            knowledgeBaseSelector: {
+              id: 'knowledgeBaseSelector',
+              type: 'knowledge-base-selector',
+              value: 'kb-uuid',
+            },
+          },
+        }),
+      }
+
+      const { blocks, migrated } = migrateSubblockIds(input)
+
+      expect(migrated).toBe(false)
+      expect(blocks['b1'].subBlocks['knowledgeBaseSelector'].value).toBe('kb-uuid')
+    })
+  })
+
+  it('should not mutate the input blocks', () => {
+    const input: Record<string, BlockState> = {
+      b1: makeBlock({
+        type: 'knowledge',
+        subBlocks: {
+          knowledgeBaseId: {
+            id: 'knowledgeBaseId',
+            type: 'knowledge-base-selector',
+            value: 'kb-uuid',
+          },
+        },
+      }),
+    }
+
+    const { blocks } = migrateSubblockIds(input)
+
+    expect(input['b1'].subBlocks['knowledgeBaseId']).toBeDefined()
+    expect(blocks['b1'].subBlocks['knowledgeBaseSelector']).toBeDefined()
+    expect(blocks).not.toBe(input)
+  })
+
+  it('should skip blocks with no registered migrations', () => {
+    const input: Record<string, BlockState> = {
+      b1: makeBlock({
+        type: 'function',
+        subBlocks: {
+          code: { id: 'code', type: 'code', value: 'console.log("hi")' },
+        },
+      }),
+    }
+
+    const { blocks, migrated } = migrateSubblockIds(input)
+
+    expect(migrated).toBe(false)
+    expect(blocks['b1'].subBlocks['code'].value).toBe('console.log("hi")')
+  })
+
+  it('should migrate multiple blocks in one pass', () => {
+    const input: Record<string, BlockState> = {
+      b1: makeBlock({
+        id: 'b1',
+        type: 'knowledge',
+        subBlocks: {
+          knowledgeBaseId: {
+            id: 'knowledgeBaseId',
+            type: 'knowledge-base-selector',
+            value: 'kb-1',
+          },
+        },
+      }),
+      b2: makeBlock({
+        id: 'b2',
+        type: 'knowledge',
+        subBlocks: {
+          knowledgeBaseId: {
+            id: 'knowledgeBaseId',
+            type: 'knowledge-base-selector',
+            value: 'kb-2',
+          },
+        },
+      }),
+      b3: makeBlock({
+        id: 'b3',
+        type: 'function',
+        subBlocks: {
+          code: { id: 'code', type: 'code', value: '' },
+        },
+      }),
+    }
+
+    const { blocks, migrated } = migrateSubblockIds(input)
+
+    expect(migrated).toBe(true)
+    expect(blocks['b1'].subBlocks['knowledgeBaseSelector'].value).toBe('kb-1')
+    expect(blocks['b2'].subBlocks['knowledgeBaseSelector'].value).toBe('kb-2')
+    expect(blocks['b3'].subBlocks['code']).toBeDefined()
+  })
+
+  it('should handle blocks with empty subBlocks', () => {
+    const input: Record<string, BlockState> = {
+      b1: makeBlock({ type: 'knowledge', subBlocks: {} }),
+    }
+
+    const { migrated } = migrateSubblockIds(input)
+
+    expect(migrated).toBe(false)
+  })
+})

apps/sim/lib/workflows/migrations/subblock-migrations.ts

@@ -0,0 +1,90 @@
+import { createLogger } from '@sim/logger'
+import type { BlockState } from '@/stores/workflows/workflow/types'
+
+const logger = createLogger('SubblockMigrations')
+
+/**
+ * Maps old subblock IDs to their current equivalents per block type.
+ *
+ * When a subblock is renamed in a block definition, old deployed/saved states
+ * still carry the value under the previous key. Without this mapping the
+ * serializer silently drops the value, breaking execution.
+ *
+ * Format: { blockType: { oldSubblockId: newSubblockId } }
+ */
+export const SUBBLOCK_ID_MIGRATIONS: Record<string, Record<string, string>> = {
+  knowledge: {
+    knowledgeBaseId: 'knowledgeBaseSelector',
+  },
+}
+
+/**
+ * Migrates legacy subblock IDs inside a single block's subBlocks map.
+ * Returns a new subBlocks record if anything changed, or the original if not.
+ */
+function migrateBlockSubblockIds(
+  subBlocks: Record<string, BlockState['subBlocks'][string]>,
+  renames: Record<string, string>
+): { subBlocks: Record<string, BlockState['subBlocks'][string]>; migrated: boolean } {
+  let migrated = false
+
+  for (const oldId of Object.keys(renames)) {
+    if (oldId in subBlocks) {
+      migrated = true
+      break
+    }
+  }
+
+  if (!migrated) return { subBlocks, migrated: false }
+
+  const result = { ...subBlocks }
+
+  for (const [oldId, newId] of Object.entries(renames)) {
+    if (!(oldId in result)) continue
+
+    if (newId in result) {
+      delete result[oldId]
+      continue
+    }
+
+    const oldEntry = result[oldId]
+    result[newId] = { ...oldEntry, id: newId }
+    delete result[oldId]
+  }
+
+  return { subBlocks: result, migrated: true }
+}
+
+/**
+ * Applies subblock-ID migrations to every block in a workflow.
+ * Returns a new blocks record with migrated subBlocks where needed.
+ */
+export function migrateSubblockIds(blocks: Record<string, BlockState>): {
+  blocks: Record<string, BlockState>
+  migrated: boolean
+} {
+  let anyMigrated = false
+  const result: Record<string, BlockState> = {}
+
+  for (const [blockId, block] of Object.entries(blocks)) {
+    const renames = SUBBLOCK_ID_MIGRATIONS[block.type]
+    if (!renames || !block.subBlocks) {
+      result[blockId] = block
+      continue
+    }
+
+    const { subBlocks, migrated } = migrateBlockSubblockIds(block.subBlocks, renames)
+    if (migrated) {
+      logger.info('Migrated legacy subblock IDs', {
+        blockId: block.id,
+        blockType: block.type,
+      })
+      anyMigrated = true
+      result[blockId] = { ...block, subBlocks }
+    } else {
+      result[blockId] = block
+    }
+  }
+
+  return { blocks: result, migrated: anyMigrated }
+}

apps/sim/lib/workflows/persistence/utils.ts

@@ -14,6 +14,7 @@ import { and, desc, eq, inArray, sql } from 'drizzle-orm'
 import type { Edge } from 'reactflow'
 import { v4 as uuidv4 } from 'uuid'
 import type { DbOrTx } from '@/lib/db/types'
+import { migrateSubblockIds } from '@/lib/workflows/migrations/subblock-migrations'
 import { sanitizeAgentToolsInBlocks } from '@/lib/workflows/sanitization/validation'
 import type { BlockState, Loop, Parallel, WorkflowState } from '@/stores/workflows/workflow/types'
 import { SUBFLOW_TYPES } from '@/stores/workflows/workflow/types'
@@ -113,10 +114,10 @@ export async function loadDeployedWorkflowState(
       resolvedWorkspaceId = wfRow?.workspaceId ?? undefined
     }
 
-    const resolvedBlocks = state.blocks || {}
-    const { blocks: migratedBlocks } = resolvedWorkspaceId
-      ? await migrateCredentialIds(resolvedBlocks, resolvedWorkspaceId)
-      : { blocks: resolvedBlocks }
+    const { blocks: migratedBlocks } = await applyBlockMigrations(
+      state.blocks || {},
+      resolvedWorkspaceId
+    )
 
     return {
       blocks: migratedBlocks,
@@ -133,6 +134,50 @@ export async function loadDeployedWorkflowState(
   }
 }
 
+interface MigrationContext {
+  blocks: Record<string, BlockState>
+  workspaceId?: string
+  migrated: boolean
+}
+
+type BlockMigration = (ctx: MigrationContext) => MigrationContext | Promise<MigrationContext>
+
+function createMigrationPipeline(migrations: BlockMigration[]) {
+  return async (
+    blocks: Record<string, BlockState>,
+    workspaceId?: string
+  ): Promise<{ blocks: Record<string, BlockState>; migrated: boolean }> => {
+    let ctx: MigrationContext = { blocks, workspaceId, migrated: false }
+    for (const migration of migrations) {
+      ctx = await migration(ctx)
+    }
+    return { blocks: ctx.blocks, migrated: ctx.migrated }
+  }
+}
+
+const applyBlockMigrations = createMigrationPipeline([
+  (ctx) => {
+    const { blocks } = sanitizeAgentToolsInBlocks(ctx.blocks)
+    return { ...ctx, blocks }
+  },
+
+  (ctx) => ({
+    ...ctx,
+    blocks: migrateAgentBlocksToMessagesFormat(ctx.blocks),
+  }),
+
+  async (ctx) => {
+    if (!ctx.workspaceId) return ctx
+    const { blocks, migrated } = await migrateCredentialIds(ctx.blocks, ctx.workspaceId)
+    return { ...ctx, blocks, migrated: ctx.migrated || migrated }
+  },
+
+  (ctx) => {
+    const { blocks, migrated } = migrateSubblockIds(ctx.blocks)
+    return { ...ctx, blocks, migrated: ctx.migrated || migrated }
+  },
+])
+
 /**
  * Migrates agent blocks from old format (systemPrompt/userPrompt) to new format (messages array)
  * This ensures backward compatibility for workflows created before the messages-input refactor.
@@ -356,22 +401,16 @@ export async function loadWorkflowFromNormalizedTables(
       blocksMap[block.id] = assembled
     })
 
-    // Sanitize any invalid custom tools in agent blocks to prevent client crashes
-    const { blocks: sanitizedBlocks } = sanitizeAgentToolsInBlocks(blocksMap)
+    const { blocks: finalBlocks, migrated } = await applyBlockMigrations(
+      blocksMap,
+      workflowRow?.workspaceId ?? undefined
+    )
 
-    // Migrate old agent block format (systemPrompt/userPrompt) to new messages array format
-    const migratedBlocks = migrateAgentBlocksToMessagesFormat(sanitizedBlocks)
-
-    // Migrate legacy account.id → credential.id in OAuth subblocks
-    const { blocks: credMigratedBlocks, migrated: credentialsMigrated } = workflowRow?.workspaceId
-      ? await migrateCredentialIds(migratedBlocks, workflowRow.workspaceId)
-      : { blocks: migratedBlocks, migrated: false }
-
-    if (credentialsMigrated) {
+    if (migrated) {
       Promise.resolve().then(async () => {
         try {
-          for (const [blockId, block] of Object.entries(credMigratedBlocks)) {
-            if (block.subBlocks !== migratedBlocks[blockId]?.subBlocks) {
+          for (const [blockId, block] of Object.entries(finalBlocks)) {
+            if (block.subBlocks !== blocksMap[blockId]?.subBlocks) {
               await db
                 .update(workflowBlocks)
                 .set({ subBlocks: block.subBlocks, updatedAt: new Date() })
@@ -381,7 +420,7 @@ export async function loadWorkflowFromNormalizedTables(
             }
           }
         } catch (err) {
-          logger.warn('Failed to persist credential ID migration', { workflowId, error: err })
+          logger.warn('Failed to persist block migrations', { workflowId, error: err })
         }
       })
     }
@@ -422,13 +461,13 @@ export async function loadWorkflowFromNormalizedTables(
           forEachItems: (config as Loop).forEachItems ?? '',
           whileCondition: (config as Loop).whileCondition ?? '',
           doWhileCondition: (config as Loop).doWhileCondition ?? '',
-          enabled: credMigratedBlocks[subflow.id]?.enabled ?? true,
+          enabled: finalBlocks[subflow.id]?.enabled ?? true,
         }
         loops[subflow.id] = loop
 
-        if (credMigratedBlocks[subflow.id]) {
-          const block = credMigratedBlocks[subflow.id]
-          credMigratedBlocks[subflow.id] = {
+        if (finalBlocks[subflow.id]) {
+          const block = finalBlocks[subflow.id]
+          finalBlocks[subflow.id] = {
             ...block,
             data: {
               ...block.data,
@@ -449,7 +488,7 @@ export async function loadWorkflowFromNormalizedTables(
             (config as Parallel).parallelType === 'collection'
               ? (config as Parallel).parallelType
               : 'count',
-          enabled: credMigratedBlocks[subflow.id]?.enabled ?? true,
+          enabled: finalBlocks[subflow.id]?.enabled ?? true,
         }
         parallels[subflow.id] = parallel
       } else {
@@ -458,7 +497,7 @@ export async function loadWorkflowFromNormalizedTables(
     })
 
     return {
-      blocks: credMigratedBlocks,
+      blocks: finalBlocks,
       edges: edgesArray,
       loops,
       parallels,

apps/sim/providers/models.ts

@@ -122,6 +122,40 @@ export const PROVIDER_DEFINITIONS: Record<string, ProviderDefinition> = {
         },
         contextWindow: 128000,
       },
+      {
+        id: 'gpt-5.4',
+        pricing: {
+          input: 2.5,
+          cachedInput: 0.25,
+          output: 15.0,
+          updatedAt: '2026-03-05',
+        },
+        capabilities: {
+          reasoningEffort: {
+            values: ['none', 'low', 'medium', 'high', 'xhigh'],
+          },
+          verbosity: {
+            values: ['low', 'medium', 'high'],
+          },
+          maxOutputTokens: 128000,
+        },
+        contextWindow: 1050000,
+      },
+      {
+        id: 'gpt-5.4-pro',
+        pricing: {
+          input: 30.0,
+          output: 180.0,
+          updatedAt: '2026-03-05',
+        },
+        capabilities: {
+          reasoningEffort: {
+            values: ['medium', 'high', 'xhigh'],
+          },
+          maxOutputTokens: 128000,
+        },
+        contextWindow: 1050000,
+      },
       {
         id: 'gpt-5.2',
         pricing: {
@@ -493,6 +527,25 @@ export const PROVIDER_DEFINITIONS: Record<string, ProviderDefinition> = {
         },
         contextWindow: 128000,
       },
+      {
+        id: 'azure/gpt-5.4',
+        pricing: {
+          input: 2.5,
+          cachedInput: 0.25,
+          output: 15.0,
+          updatedAt: '2026-03-05',
+        },
+        capabilities: {
+          reasoningEffort: {
+            values: ['none', 'low', 'medium', 'high', 'xhigh'],
+          },
+          verbosity: {
+            values: ['low', 'medium', 'high'],
+          },
+          maxOutputTokens: 128000,
+        },
+        contextWindow: 1050000,
+      },
       {
         id: 'azure/gpt-5.2',
         pricing: {

apps/sim/providers/utils.test.ts

@@ -523,13 +523,16 @@ describe('Model Capabilities', () => {
 
     it.concurrent('should have GPT-5 models in both reasoning effort and verbosity arrays', () => {
       const gpt5ModelsWithReasoningEffort = MODELS_WITH_REASONING_EFFORT.filter(
-        (m) => m.includes('gpt-5') && !m.includes('chat-latest')
+        (m) => m.includes('gpt-5') && !m.includes('chat-latest') && !m.includes('gpt-5.4-pro')
       )
       const gpt5ModelsWithVerbosity = MODELS_WITH_VERBOSITY.filter(
         (m) => m.includes('gpt-5') && !m.includes('chat-latest')
       )
       expect(gpt5ModelsWithReasoningEffort.sort()).toEqual(gpt5ModelsWithVerbosity.sort())
 
+      expect(MODELS_WITH_REASONING_EFFORT).toContain('gpt-5.4-pro')
+      expect(MODELS_WITH_VERBOSITY).not.toContain('gpt-5.4-pro')
+
       expect(MODELS_WITH_REASONING_EFFORT).toContain('o1')
       expect(MODELS_WITH_VERBOSITY).not.toContain('o1')
     })

apps/sim/scripts/check-subblock-id-stability.ts

@@ -0,0 +1,170 @@
+#!/usr/bin/env bun
+
+/**
+ * CI check: detect subblock ID renames that would break deployed workflows.
+ *
+ * Compares the current block registry against the parent commit.
+ * If any subblock ID was removed from a block, it must have a corresponding
+ * entry in SUBBLOCK_ID_MIGRATIONS — otherwise this script exits non-zero.
+ *
+ * Usage:
+ *   bun run apps/sim/scripts/check-subblock-id-stability.ts [base-ref]
+ *
+ * base-ref defaults to HEAD~1.  In a PR CI pipeline, pass the merge base:
+ *   bun run apps/sim/scripts/check-subblock-id-stability.ts origin/main
+ */
+
+import { execSync } from 'child_process'
+import { SUBBLOCK_ID_MIGRATIONS } from '@/lib/workflows/migrations/subblock-migrations'
+import { getAllBlocks } from '@/blocks/registry'
+
+const baseRef = process.argv[2] || 'HEAD~1'
+
+const gitRoot = execSync('git rev-parse --show-toplevel', { encoding: 'utf-8' }).trim()
+const gitOpts = { encoding: 'utf-8' as const, cwd: gitRoot }
+
+type IdMap = Record<string, Set<string>>
+
+/**
+ * Extracts subblock IDs from the `subBlocks: [ ... ]` section of a block
+ * definition. Only grabs the top-level `id:` of each subblock object —
+ * ignores nested IDs inside `options`, `columns`, etc.
+ */
+function extractSubBlockIds(source: string): string[] {
+  const startIdx = source.indexOf('subBlocks:')
+  if (startIdx === -1) return []
+
+  const bracketStart = source.indexOf('[', startIdx)
+  if (bracketStart === -1) return []
+
+  const ids: string[] = []
+  let braceDepth = 0
+  let bracketDepth = 0
+  let i = bracketStart + 1
+  bracketDepth = 1
+
+  while (i < source.length && bracketDepth > 0) {
+    const ch = source[i]
+
+    if (ch === '[') bracketDepth++
+    else if (ch === ']') {
+      bracketDepth--
+      if (bracketDepth === 0) break
+    } else if (ch === '{') {
+      braceDepth++
+      if (braceDepth === 1) {
+        const ahead = source.slice(i, i + 200)
+        const idMatch = ahead.match(/{\s*(?:\/\/[^\n]*\n\s*)*id:\s*['"]([^'"]+)['"]/)
+        if (idMatch) {
+          ids.push(idMatch[1])
+        }
+      }
+    } else if (ch === '}') {
+      braceDepth--
+    }
+
+    i++
+  }
+
+  return ids
+}
+
+function getCurrentIds(): IdMap {
+  const map: IdMap = {}
+  for (const block of getAllBlocks()) {
+    map[block.type] = new Set(block.subBlocks.map((sb) => sb.id))
+  }
+  return map
+}
+
+function getPreviousIds(): IdMap {
+  const registryPath = 'apps/sim/blocks/registry.ts'
+  const blocksDir = 'apps/sim/blocks/blocks'
+
+  let hasChanges = false
+  try {
+    const diff = execSync(
+      `git diff --name-only ${baseRef} HEAD -- ${registryPath} ${blocksDir}`,
+      gitOpts
+    ).trim()
+    hasChanges = diff.length > 0
+  } catch {
+    console.log('⚠ Could not diff against base ref — skipping check')
+    process.exit(0)
+  }
+
+  if (!hasChanges) {
+    console.log('✓ No block definition changes detected — nothing to check')
+    process.exit(0)
+  }
+
+  const map: IdMap = {}
+
+  try {
+    const blockFiles = execSync(`git ls-tree -r --name-only ${baseRef} -- ${blocksDir}`, gitOpts)
+      .trim()
+      .split('\n')
+      .filter((f) => f.endsWith('.ts') && !f.endsWith('.test.ts'))
+
+    for (const filePath of blockFiles) {
+      let content: string
+      try {
+        content = execSync(`git show ${baseRef}:${filePath}`, gitOpts)
+      } catch {
+        continue
+      }
+
+      const typeMatch = content.match(/BlockConfig\s*=\s*\{[\s\S]*?type:\s*['"]([^'"]+)['"]/)
+      if (!typeMatch) continue
+      const blockType = typeMatch[1]
+
+      const ids = extractSubBlockIds(content)
+      if (ids.length === 0) continue
+
+      map[blockType] = new Set(ids)
+    }
+  } catch (err) {
+    console.log(`⚠ Could not read previous block files from ${baseRef} — skipping check`, err)
+    process.exit(0)
+  }
+
+  return map
+}
+
+const previous = getPreviousIds()
+const current = getCurrentIds()
+const errors: string[] = []
+
+for (const [blockType, prevIds] of Object.entries(previous)) {
+  const currIds = current[blockType]
+  if (!currIds) continue
+
+  const migrations = SUBBLOCK_ID_MIGRATIONS[blockType] ?? {}
+
+  for (const oldId of prevIds) {
+    if (currIds.has(oldId)) continue
+
+    if (oldId in migrations) continue
+
+    errors.push(
+      `Block "${blockType}": subblock ID "${oldId}" was removed.\n` +
+        `  → Add a migration in SUBBLOCK_ID_MIGRATIONS (lib/workflows/migrations/subblock-migrations.ts)\n` +
+        `    mapping "${oldId}" to its replacement ID.`
+    )
+  }
+}
+
+if (errors.length > 0) {
+  console.error('✗ Subblock ID stability check FAILED\n')
+  console.error(
+    'Removing subblock IDs breaks deployed workflows.\n' +
+      'Either revert the rename or add a migration entry.\n'
+  )
+  for (const err of errors) {
+    console.error(`  ${err}\n`)
+  }
+  process.exit(1)
+} else {
+  console.log('✓ Subblock ID stability check passed')
+  process.exit(0)
+}