simstudioai · waleedlatif1 · May 16, 2026 · May 16, 2026 · May 16, 2026 · May 16, 2026
diff --git a/apps/sim/executor/execution/engine.test.ts b/apps/sim/executor/execution/engine.test.ts
@@ -4,9 +4,27 @@
 import { sleep } from '@sim/utils/helpers'
 import { afterEach, beforeEach, describe, expect, it, type Mock, vi } from 'vitest'
 
+const { mockCancellationSubscribers } = vi.hoisted(() => ({
+  mockCancellationSubscribers: new Set<(event: { executionId: string }) => void>(),
+}))
+
 vi.mock('@/lib/execution/cancellation', () => ({
   isExecutionCancelled: vi.fn(),
   isRedisCancellationEnabled: vi.fn(),
+  getCancellationChannel: () => ({
+    publish: (event: { executionId: string }) => {
+      for (const handler of mockCancellationSubscribers) handler(event)
+    },
+    subscribe: (handler: (event: { executionId: string }) => void) => {
+      mockCancellationSubscribers.add(handler)
+      return () => {
+        mockCancellationSubscribers.delete(handler)
+      }
+    },
+    dispose: () => {
+      mockCancellationSubscribers.clear()
+    },
+  }),
 }))
 
 import { isExecutionCancelled, isRedisCancellationEnabled } from '@/lib/execution/cancellation'
@@ -115,6 +133,7 @@ function createMockNodeOrchestrator(executeDelay = 0): MockNodeOrchestrator {
 describe('ExecutionEngine', () => {
   beforeEach(() => {
     vi.clearAllMocks()
+    mockCancellationSubscribers.clear()
     ;(isExecutionCancelled as Mock).mockResolvedValue(false)
     ;(isRedisCancellationEnabled as Mock).mockReturnValue(false)
   })
@@ -346,7 +365,93 @@ describe('ExecutionEngine', () => {
       expect(result.status).toBe('cancelled')
     })
 
-    it('should respect cancellation check interval', async () => {
+    it('wakes from a slow in-flight node when a pub/sub cancellation arrives', async () => {
+      ;(isRedisCancellationEnabled as Mock).mockReturnValue(true)
+      ;(isExecutionCancelled as Mock).mockResolvedValue(false)
+
+      const startNode = createMockNode('start', 'starter')
+      const slowNode = createMockNode('slow', 'function')
+      startNode.outgoingEdges.set('edge1', { target: 'slow' })
+
+      const dag = createMockDAG([startNode, slowNode])
+      const context = createMockContext({ executionId: 'pubsub-execution' })
+      const edgeManager = createMockEdgeManager((node) => (node.id === 'start' ? ['slow'] : []))
+      const nodeOrchestrator = createMockNodeOrchestrator(500)
+
+      const engine = new ExecutionEngine(context, dag, edgeManager, nodeOrchestrator)
+      const executionPromise = engine.run('start')
+
+      setTimeout(() => {
+        for (const handler of mockCancellationSubscribers) {
+          handler({ executionId: 'pubsub-execution' })
+        }
+      }, 5)
+
+      const startTime = Date.now()
+      const result = await executionPromise
+      const duration = Date.now() - startTime
+
+      expect(result.status).toBe('cancelled')
+      expect(duration).toBeLessThan(100)
+    })
+
+    it('ignores pub/sub events targeting other executions', async () => {
+      ;(isRedisCancellationEnabled as Mock).mockReturnValue(true)
+      ;(isExecutionCancelled as Mock).mockResolvedValue(false)
+
+      const startNode = createMockNode('start', 'starter')
+      const dag = createMockDAG([startNode])
+      const context = createMockContext({ executionId: 'execution-a' })
+      const edgeManager = createMockEdgeManager()
+      const nodeOrchestrator = createMockNodeOrchestrator()
+
+      const engine = new ExecutionEngine(context, dag, edgeManager, nodeOrchestrator)
+
+      for (const handler of mockCancellationSubscribers) {
+        handler({ executionId: 'execution-b' })
+      }
+
+      const result = await engine.run('start')
+      expect(result.status).toBeUndefined()
+      expect(result.success).toBe(true)
+    })
+
+    it('unsubscribes from the cancellation channel after run completes', async () => {
+      ;(isRedisCancellationEnabled as Mock).mockReturnValue(true)
+      ;(isExecutionCancelled as Mock).mockResolvedValue(false)
+
+      const startNode = createMockNode('start', 'starter')
+      const dag = createMockDAG([startNode])
+      const context = createMockContext({ executionId: 'cleanup-execution' })
+      const edgeManager = createMockEdgeManager()
+      const nodeOrchestrator = createMockNodeOrchestrator()
+
+      const engine = new ExecutionEngine(context, dag, edgeManager, nodeOrchestrator)
+      expect(mockCancellationSubscribers.size).toBe(1)
+
+      await engine.run('start')
+
+      expect(mockCancellationSubscribers.size).toBe(0)
+    })
+
+    it('honours the durable backstop when cancelled before subscribing', async () => {
+      ;(isRedisCancellationEnabled as Mock).mockReturnValue(true)
+      ;(isExecutionCancelled as Mock).mockResolvedValue(true)
+
+      const startNode = createMockNode('start', 'starter')
+      const dag = createMockDAG([startNode])
+      const context = createMockContext()
+      const edgeManager = createMockEdgeManager()
+      const nodeOrchestrator = createMockNodeOrchestrator()
+
+      const engine = new ExecutionEngine(context, dag, edgeManager, nodeOrchestrator)
+      const result = await engine.run('start')
+
+      expect(result.status).toBe('cancelled')
+      expect(nodeOrchestrator.executionCount).toBe(0)
+    })
+
+    it('calls isExecutionCancelled once as the startup backstop check', async () => {
       ;(isRedisCancellationEnabled as Mock).mockReturnValue(true)
       ;(isExecutionCancelled as Mock).mockResolvedValue(false)
 
@@ -359,7 +464,7 @@ describe('ExecutionEngine', () => {
       const engine = new ExecutionEngine(context, dag, edgeManager, nodeOrchestrator)
       await engine.run('start')
 
-      expect((isExecutionCancelled as Mock).mock.calls.length).toBeGreaterThanOrEqual(1)
+      expect((isExecutionCancelled as Mock).mock.calls.length).toBe(1)
     })
   })
 

diff --git a/apps/sim/executor/execution/engine.ts b/apps/sim/executor/execution/engine.ts
@@ -1,6 +1,10 @@
 import { createLogger, type Logger } from '@sim/logger'
 import { toError } from '@sim/utils/errors'
-import { isExecutionCancelled, isRedisCancellationEnabled } from '@/lib/execution/cancellation'
+import {
+  getCancellationChannel,
+  isExecutionCancelled,
+  isRedisCancellationEnabled,
+} from '@/lib/execution/cancellation'
 import { BlockType } from '@/executor/constants'
 import type { DAG } from '@/executor/dag/builder'
 import type { EdgeManager } from '@/executor/execution/edge-manager'
@@ -31,11 +35,9 @@ export class ExecutionEngine {
   private errorFlag = false
   private stoppedEarlyFlag = false
   private executionError: Error | null = null
-  private lastCancellationCheck = 0
-  private readonly useRedisCancellation: boolean
-  private readonly CANCELLATION_CHECK_INTERVAL_MS = 500
-  private abortPromise: Promise<void> | null = null
-  private abortResolve: (() => void) | null = null
+  private abortPromise!: Promise<void>
+  private abortResolve!: () => void
+  private cancellationUnsubscribe: (() => void) | null = null
   private execLogger: Logger
 
   constructor(
@@ -45,7 +47,6 @@ export class ExecutionEngine {
     private nodeOrchestrator: NodeExecutionOrchestrator
   ) {
     this.allowResumeTriggers = this.context.metadata.resumeFromSnapshot === true
-    this.useRedisCancellation = isRedisCancellationEnabled() && !!this.context.executionId
     this.execLogger = logger.withMetadata({
       workflowId: this.context.workflowId,
       workspaceId: this.context.workspaceId,
@@ -54,72 +55,64 @@ export class ExecutionEngine {
       requestId: this.context.metadata.requestId,
     })
     this.initializeAbortHandler()
+    this.subscribeToCancellationChannel()
+  }
+
+  private subscribeToCancellationChannel(): void {
+    if (!this.context.executionId) return
+    const executionId = this.context.executionId
+    this.cancellationUnsubscribe = getCancellationChannel().subscribe((event) => {
+      if (event.executionId !== executionId) return
+      this.execLogger.info('Execution cancelled via pub/sub', { executionId })
+      this.signalCancelled()
+    })
   }
 
-  /**
-   * Sets up a single abort promise that can be reused throughout execution.
-   * This avoids creating multiple event listeners and potential memory leaks.
-   */
   private initializeAbortHandler(): void {
+    this.abortPromise = new Promise<void>((resolve) => {
+      this.abortResolve = resolve
+    })
+
     if (!this.context.abortSignal) return
 
     if (this.context.abortSignal.aborted) {
-      this.cancelledFlag = true
-      this.abortPromise = Promise.resolve()
+      this.signalCancelled()
       return
     }
 
-    this.abortPromise = new Promise<void>((resolve) => {
-      this.abortResolve = resolve
-    })
-
-    this.context.abortSignal.addEventListener(
-      'abort',
-      () => {
-        this.cancelledFlag = true
-        this.abortResolve?.()
-      },
-      { once: true }
-    )
+    this.context.abortSignal.addEventListener('abort', () => this.signalCancelled(), { once: true })
   }
 
-  private async checkCancellation(): Promise<boolean> {
-    if (this.cancelledFlag) {
-      return true
-    }
-
-    if (this.useRedisCancellation) {
-      const now = Date.now()
-      if (now - this.lastCancellationCheck < this.CANCELLATION_CHECK_INTERVAL_MS) {
-        return false
-      }
-      this.lastCancellationCheck = now
+  private signalCancelled(): void {
+    if (this.cancelledFlag) return
+    this.cancelledFlag = true
+    this.abortResolve()
+  }
 
-      const cancelled = await isExecutionCancelled(this.context.executionId!)
-      if (cancelled) {
-        this.cancelledFlag = true
-        this.execLogger.info('Execution cancelled via Redis', {
-          executionId: this.context.executionId,
-        })
-      }
-      return cancelled
-    }
+  private checkCancellation(): boolean {
+    return this.cancelledFlag
+  }
 
-    if (this.context.abortSignal?.aborted) {
-      this.cancelledFlag = true
-      return true
+  /** Catches cancellations published before this engine subscribed (e.g. resume from snapshot). */
+  private async checkCancellationBackstop(): Promise<void> {
+    if (!this.context.executionId || !isRedisCancellationEnabled()) return
+    const cancelled = await isExecutionCancelled(this.context.executionId)
+    if (cancelled) {
+      this.execLogger.info('Execution already cancelled at engine start (Redis backstop)', {
+        executionId: this.context.executionId,
+      })
+      this.signalCancelled()
     }
-
-    return false
   }
 
   async run(triggerBlockId?: string): Promise<ExecutionResult> {
     const startTime = performance.now()
     try {
       this.initializeQueue(triggerBlockId)
+      await this.checkCancellationBackstop()
 
       while (this.hasWork()) {
-        if ((await this.checkCancellation()) || this.errorFlag || this.stoppedEarlyFlag) {
+        if (this.checkCancellation() || this.errorFlag || this.stoppedEarlyFlag) {
           break
         }
         await this.processQueue()
@@ -194,6 +187,15 @@ export class ExecutionEngine {
         attachExecutionResult(error, executionResult)
       }
       throw error
+    } finally {
+      this.cleanup()
+    }
+  }
+
+  private cleanup(): void {
+    if (this.cancellationUnsubscribe) {
+      this.cancellationUnsubscribe()
+      this.cancellationUnsubscribe = null
     }
   }
 
@@ -238,32 +240,17 @@ export class ExecutionEngine {
 
   private async waitForAnyExecution(): Promise<void> {
     if (this.executing.size > 0) {
-      const abortPromise = this.getAbortPromise()
-      if (abortPromise) {
-        await Promise.race([...this.executing, abortPromise])
-      } else {
-        await Promise.race(this.executing)
-      }
+      await Promise.race([...this.executing, this.abortPromise])
     }
   }
 
   private async waitForAllExecutions(): Promise<void> {
-    const abortPromise = this.getAbortPromise()
-    if (abortPromise) {
-      await Promise.race([Promise.all(this.executing), abortPromise])
-    } else {
-      await Promise.all(this.executing)
+    await Promise.race([Promise.all(this.executing), this.abortPromise])
+    if (this.executing.size > 0) {
+      await Promise.allSettled(this.executing)
     }
   }
 
-  /**
-   * Returns the cached abort promise. This is safe to call multiple times
-   * as it reuses the same promise instance created during initialization.
-   */
-  private getAbortPromise(): Promise<void> | null {
-    return this.abortPromise
-  }
-
   private async withQueueLock<T>(fn: () => Promise<T> | T): Promise<T> {
     const prevLock = this.queueLock
     let resolveLock: () => void
@@ -363,7 +350,7 @@ export class ExecutionEngine {
 
   private async processQueue(): Promise<void> {
     while (this.readyQueue.length > 0) {
-      if ((await this.checkCancellation()) || this.errorFlag) {
+      if (this.checkCancellation() || this.errorFlag) {
         break
       }
       const nodeId = this.dequeue()

diff --git a/apps/sim/executor/handlers/api/api-handler.test.ts b/apps/sim/executor/handlers/api/api-handler.test.ts
@@ -116,8 +116,7 @@ describe('ApiBlockHandler', () => {
         body: { key: 'value' }, // Expect parsed body
         _context: { workflowId: 'test-workflow-id' },
       },
-      false, // skipPostProcess
-      mockContext // execution context
+      { executionContext: mockContext }
     )
     expect(result).toEqual(expectedOutput)
   })
@@ -177,8 +176,7 @@ describe('ApiBlockHandler', () => {
     expect(mockExecuteTool).toHaveBeenCalledWith(
       'http_request',
       expect.objectContaining({ body: expectedParsedBody }),
-      false, // skipPostProcess
-      mockContext // execution context
+      { executionContext: mockContext }
     )
   })
 
@@ -193,8 +191,7 @@ describe('ApiBlockHandler', () => {
     expect(mockExecuteTool).toHaveBeenCalledWith(
       'http_request',
       expect.objectContaining({ body: 'This is plain text' }),
-      false, // skipPostProcess
-      mockContext // execution context
+      { executionContext: mockContext }
     )
   })
 
@@ -209,8 +206,7 @@ describe('ApiBlockHandler', () => {
     expect(mockExecuteTool).toHaveBeenCalledWith(
       'http_request',
       expect.objectContaining({ body: undefined }),
-      false, // skipPostProcess
-      mockContext // execution context
+      { executionContext: mockContext }
     )
   })
 

diff --git a/apps/sim/executor/handlers/api/api-handler.ts b/apps/sim/executor/handlers/api/api-handler.ts
@@ -78,8 +78,7 @@ export class ApiBlockHandler implements BlockHandler {
             callChain: ctx.callChain,
           },
         },
-        false,
-        ctx
+        { executionContext: ctx }
       )
 
       if (!result.success) {
-Original file line number
+Diff line change
@@ Expand Up / @@ -78,8 +78,7 @@ export class ApiBlockHandler implements BlockHandler { @@
                 callChain: ctx.callChain,
               },
             },
-            false,
-            ctx
+            { executionContext: ctx }
           )
           if (!result.success) {
@@ Expand Down @@