fix(workflow): throw 4xx on variable resolution failures (#4325)

* fix(workflow): throw 4xx on variable resolution failures

* Switch spread order

Author: TheodoreSpeaks

apps/sim/app/api/workflows/[id]/execute/route.ts

@@ -61,7 +61,7 @@ import type {
   SerializableExecutionState,
 } from '@/executor/execution/types'
 import type { NormalizedBlockOutput, StreamingExecution } from '@/executor/types'
-import { hasExecutionResult } from '@/executor/utils/errors'
+import { getExecutionErrorStatus, hasExecutionResult } from '@/executor/utils/errors'
 import { Serializer } from '@/serializer'
 import { CORE_TRIGGER_TYPES, type CoreTriggerType } from '@/stores/logs/filters/types'
 
@@ -821,6 +821,7 @@ async function handleExecutePost(
         reqLogger.error(`Non-SSE execution failed: ${errorMessage}`)
 
         const executionResult = hasExecutionResult(error) ? error.executionResult : undefined
+        const status = getExecutionErrorStatus(error)
 
         return NextResponse.json(
           {
@@ -835,7 +836,7 @@ async function handleExecutePost(
                 }
               : undefined,
           },
-          { status: 500 }
+          { status }
         )
       } finally {
         timeoutController.cleanup()

apps/sim/executor/utils/block-reference.test.ts

@@ -293,6 +293,7 @@ describe('InvalidFieldError', () => {
     expect(error.fieldPath).toBe('invalid.path')
     expect(error.availableFields).toEqual(['field1', 'field2'])
     expect(error.name).toBe('InvalidFieldError')
+    expect(error.statusCode).toBe(400)
   })
 
   it('should format message correctly', () => {

apps/sim/executor/utils/block-reference.ts

@@ -27,6 +27,8 @@ export interface BlockReferenceResult {
 }
 
 export class InvalidFieldError extends Error {
+  readonly statusCode = 400
+
   constructor(
     public readonly blockName: string,
     public readonly fieldPath: string,

apps/sim/executor/utils/errors.ts

@@ -49,13 +49,16 @@ export function buildBlockExecutionError(details: BlockExecutionErrorDetails): E
 
   const error = new Error(`${blockName}: ${errorMessage}`)
 
+  const innerStatusCode = readStatusCode(details.error)
+
   Object.assign(error, {
     blockId: details.block.id,
     blockName,
     blockType,
     workflowId: details.context?.workflowId,
     timestamp: new Date().toISOString(),
     ...details.additionalInfo,
+    ...(innerStatusCode !== undefined ? { statusCode: innerStatusCode } : {}),
   })
 
   return error
@@ -89,6 +92,25 @@ export function buildHTTPError(config: {
   return error
 }
 
+function readStatusCode(value: unknown): number | undefined {
+  if (!(value instanceof Error)) return undefined
+  const status = (value as unknown as { statusCode?: unknown }).statusCode
+  return typeof status === 'number' ? status : undefined
+}
+
+/**
+ * Maps an execution error to an HTTP status code. Errors thrown from the
+ * executor that represent workflow-author mistakes (invalid field references,
+ * etc.) carry a 4xx `statusCode`; everything else is a 500.
+ */
+export function getExecutionErrorStatus(error: unknown): number {
+  const status = readStatusCode(error)
+  if (status !== undefined && status >= 400 && status < 500) {
+    return status
+  }
+  return 500
+}
+
 export function normalizeError(error: unknown): string {
   if (error instanceof Error) {
     return error.message

apps/sim/executor/variables/resolvers/block.ts

@@ -97,7 +97,6 @@ export class BlockResolver implements Resolver {
         if (fallback !== undefined) {
           return fallback
         }
-        throw new Error(error.message)
       }
       throw error
     }