fix(resolver): consolidate reference resolution (#2941)

* fix(resolver): consolidate code to resolve references

* fix edge cases

* use already formatted error

* fix multi index

* fix backwards compat reachability

* handle backwards compatibility accurately

* use shared constant correctly

apps/sim/app/api/function/execute/route.test.ts

@@ -313,7 +313,7 @@ describe('Function Execute API Route', () => {
           'block-2': 'world',
         },
         blockNameMapping: {
-          validVar: 'block-1',
+          validvar: 'block-1',
           another_valid: 'block-2',
         },
       })
@@ -539,7 +539,7 @@ describe('Function Execute API Route', () => {
           'block-complex': complexData,
         },
         blockNameMapping: {
-          complexData: 'block-complex',
+          complexdata: 'block-complex',
         },
       })
 

apps/sim/app/api/function/execute/route.ts

@@ -6,11 +6,11 @@ import { executeInE2B } from '@/lib/execution/e2b'
 import { executeInIsolatedVM } from '@/lib/execution/isolated-vm'
 import { CodeLanguage, DEFAULT_CODE_LANGUAGE, isValidCodeLanguage } from '@/lib/execution/languages'
 import { escapeRegExp, normalizeName, REFERENCE } from '@/executor/constants'
+import { type OutputSchema, resolveBlockReference } from '@/executor/utils/block-reference'
 import {
   createEnvVarPattern,
   createWorkflowVariablePattern,
 } from '@/executor/utils/reference-validation'
-import { navigatePath } from '@/executor/variables/resolvers/reference'
 export const dynamic = 'force-dynamic'
 export const runtime = 'nodejs'
 
@@ -470,14 +470,17 @@ function resolveEnvironmentVariables(
 
 function resolveTagVariables(
   code: string,
-  blockData: Record<string, any>,
+  blockData: Record<string, unknown>,
   blockNameMapping: Record<string, string>,
-  contextVariables: Record<string, any>
+  blockOutputSchemas: Record<string, OutputSchema>,
+  contextVariables: Record<string, unknown>,
+  language = 'javascript'
 ): string {
   let resolvedCode = code
+  const undefinedLiteral = language === 'python' ? 'None' : 'undefined'
 
   const tagPattern = new RegExp(
-    `${REFERENCE.START}([a-zA-Z_][a-zA-Z0-9_${REFERENCE.PATH_DELIMITER}]*[a-zA-Z0-9_])${REFERENCE.END}`,
+    `${REFERENCE.START}([a-zA-Z_](?:[a-zA-Z0-9_${REFERENCE.PATH_DELIMITER}]*[a-zA-Z0-9_])?)${REFERENCE.END}`,
     'g'
   )
   const tagMatches = resolvedCode.match(tagPattern) || []
@@ -486,41 +489,37 @@ function resolveTagVariables(
     const tagName = match.slice(REFERENCE.START.length, -REFERENCE.END.length).trim()
     const pathParts = tagName.split(REFERENCE.PATH_DELIMITER)
     const blockName = pathParts[0]
+    const fieldPath = pathParts.slice(1)
 
-    const blockId = blockNameMapping[blockName]
-    if (!blockId) {
+    const result = resolveBlockReference(blockName, fieldPath, {
+      blockNameMapping,
+      blockData,
+      blockOutputSchemas,
+    })
+
+    if (!result) {
       continue
     }
 
-    const blockOutput = blockData[blockId]
-    if (blockOutput === undefined) {
-      continue
-    }
-
-    let tagValue: any
-    if (pathParts.length === 1) {
-      tagValue = blockOutput
-    } else {
-      tagValue = navigatePath(blockOutput, pathParts.slice(1))
-    }
+    let tagValue = result.value
 
     if (tagValue === undefined) {
+      resolvedCode = resolvedCode.replace(new RegExp(escapeRegExp(match), 'g'), undefinedLiteral)
       continue
     }
 
-    if (
-      typeof tagValue === 'string' &&
-      tagValue.length > 100 &&
-      (tagValue.startsWith('{') || tagValue.startsWith('['))
-    ) {
-      try {
-        tagValue = JSON.parse(tagValue)
-      } catch {
-        // Keep as-is
+    if (typeof tagValue === 'string') {
+      const trimmed = tagValue.trimStart()
+      if (trimmed.startsWith('{') || trimmed.startsWith('[')) {
+        try {
+          tagValue = JSON.parse(tagValue)
+        } catch {
+          // Keep as string if not valid JSON
+        }
       }
     }
 
-    const safeVarName = `__tag_${tagName.replace(/[^a-zA-Z0-9_]/g, '_')}`
+    const safeVarName = `__tag_${tagName.replace(/_/g, '_1').replace(/\./g, '_0')}`
     contextVariables[safeVarName] = tagValue
     resolvedCode = resolvedCode.replace(new RegExp(escapeRegExp(match), 'g'), safeVarName)
   }
@@ -537,18 +536,27 @@ function resolveTagVariables(
  */
 function resolveCodeVariables(
   code: string,
-  params: Record<string, any>,
+  params: Record<string, unknown>,
   envVars: Record<string, string> = {},
-  blockData: Record<string, any> = {},
+  blockData: Record<string, unknown> = {},
   blockNameMapping: Record<string, string> = {},
-  workflowVariables: Record<string, any> = {}
-): { resolvedCode: string; contextVariables: Record<string, any> } {
+  blockOutputSchemas: Record<string, OutputSchema> = {},
+  workflowVariables: Record<string, unknown> = {},
+  language = 'javascript'
+): { resolvedCode: string; contextVariables: Record<string, unknown> } {
   let resolvedCode = code
-  const contextVariables: Record<string, any> = {}
+  const contextVariables: Record<string, unknown> = {}
 
   resolvedCode = resolveWorkflowVariables(resolvedCode, workflowVariables, contextVariables)
   resolvedCode = resolveEnvironmentVariables(resolvedCode, params, envVars, contextVariables)
-  resolvedCode = resolveTagVariables(resolvedCode, blockData, blockNameMapping, contextVariables)
+  resolvedCode = resolveTagVariables(
+    resolvedCode,
+    blockData,
+    blockNameMapping,
+    blockOutputSchemas,
+    contextVariables,
+    language
+  )
 
   return { resolvedCode, contextVariables }
 }
@@ -585,6 +593,7 @@ export async function POST(req: NextRequest) {
       envVars = {},
       blockData = {},
       blockNameMapping = {},
+      blockOutputSchemas = {},
       workflowVariables = {},
       workflowId,
       isCustomTool = false,
@@ -601,20 +610,21 @@ export async function POST(req: NextRequest) {
       isCustomTool,
     })
 
-    // Resolve variables in the code with workflow environment variables
+    const lang = isValidCodeLanguage(language) ? language : DEFAULT_CODE_LANGUAGE
+
     const codeResolution = resolveCodeVariables(
       code,
       executionParams,
       envVars,
       blockData,
       blockNameMapping,
-      workflowVariables
+      blockOutputSchemas,
+      workflowVariables,
+      lang
     )
     resolvedCode = codeResolution.resolvedCode
     const contextVariables = codeResolution.contextVariables
 
-    const lang = isValidCodeLanguage(language) ? language : DEFAULT_CODE_LANGUAGE
-
     let jsImports = ''
     let jsRemainingCode = resolvedCode
     let hasImports = false
@@ -670,7 +680,11 @@ export async function POST(req: NextRequest) {
         prologue += `const environmentVariables = JSON.parse(${JSON.stringify(JSON.stringify(envVars))});\n`
         prologueLineCount++
         for (const [k, v] of Object.entries(contextVariables)) {
-          prologue += `const ${k} = JSON.parse(${JSON.stringify(JSON.stringify(v))});\n`
+          if (v === undefined) {
+            prologue += `const ${k} = undefined;\n`
+          } else {
+            prologue += `const ${k} = JSON.parse(${JSON.stringify(JSON.stringify(v))});\n`
+          }
           prologueLineCount++
         }
 
@@ -741,7 +755,11 @@ export async function POST(req: NextRequest) {
       prologue += `environmentVariables = json.loads(${JSON.stringify(JSON.stringify(envVars))})\n`
       prologueLineCount++
       for (const [k, v] of Object.entries(contextVariables)) {
-        prologue += `${k} = json.loads(${JSON.stringify(JSON.stringify(v))})\n`
+        if (v === undefined) {
+          prologue += `${k} = None\n`
+        } else {
+          prologue += `${k} = json.loads(${JSON.stringify(JSON.stringify(v))})\n`
+        }
         prologueLineCount++
       }
       const wrapped = [

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

@@ -305,7 +305,7 @@ export class AgentBlockHandler implements BlockHandler {
       base.executeFunction = async (callParams: Record<string, any>) => {
         const mergedParams = mergeToolParameters(userProvidedParams, callParams)
 
-        const { blockData, blockNameMapping } = collectBlockData(ctx)
+        const { blockData, blockNameMapping, blockOutputSchemas } = collectBlockData(ctx)
 
         const result = await executeTool(
           'function_execute',
@@ -317,6 +317,7 @@ export class AgentBlockHandler implements BlockHandler {
             workflowVariables: ctx.workflowVariables || {},
             blockData,
             blockNameMapping,
+            blockOutputSchemas,
             isCustomTool: true,
             _context: {
               workflowId: ctx.workflowId,

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

@@ -26,7 +26,7 @@ export async function evaluateConditionExpression(
     const contextSetup = `const context = ${JSON.stringify(evalContext)};`
     const code = `${contextSetup}\nreturn Boolean(${conditionExpression})`
 
-    const { blockData, blockNameMapping } = collectBlockData(ctx)
+    const { blockData, blockNameMapping, blockOutputSchemas } = collectBlockData(ctx)
 
     const result = await executeTool(
       'function_execute',
@@ -37,6 +37,7 @@ export async function evaluateConditionExpression(
         workflowVariables: ctx.workflowVariables || {},
         blockData,
         blockNameMapping,
+        blockOutputSchemas,
         _context: {
           workflowId: ctx.workflowId,
           workspaceId: ctx.workspaceId,

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

@@ -75,7 +75,12 @@ describe('FunctionBlockHandler', () => {
       workflowVariables: {},
       blockData: {},
       blockNameMapping: {},
-      _context: { workflowId: mockContext.workflowId, workspaceId: mockContext.workspaceId },
+      blockOutputSchemas: {},
+      _context: {
+        workflowId: mockContext.workflowId,
+        workspaceId: mockContext.workspaceId,
+        isDeployedContext: mockContext.isDeployedContext,
+      },
     }
     const expectedOutput: any = { result: 'Success' }
 
@@ -84,8 +89,8 @@ describe('FunctionBlockHandler', () => {
     expect(mockExecuteTool).toHaveBeenCalledWith(
       'function_execute',
       expectedToolParams,
-      false, // skipPostProcess
-      mockContext // execution context
+      false,
+      mockContext
     )
     expect(result).toEqual(expectedOutput)
   })
@@ -107,7 +112,12 @@ describe('FunctionBlockHandler', () => {
       workflowVariables: {},
       blockData: {},
       blockNameMapping: {},
-      _context: { workflowId: mockContext.workflowId, workspaceId: mockContext.workspaceId },
+      blockOutputSchemas: {},
+      _context: {
+        workflowId: mockContext.workflowId,
+        workspaceId: mockContext.workspaceId,
+        isDeployedContext: mockContext.isDeployedContext,
+      },
     }
     const expectedOutput: any = { result: 'Success' }
 
@@ -116,8 +126,8 @@ describe('FunctionBlockHandler', () => {
     expect(mockExecuteTool).toHaveBeenCalledWith(
       'function_execute',
       expectedToolParams,
-      false, // skipPostProcess
-      mockContext // execution context
+      false,
+      mockContext
     )
     expect(result).toEqual(expectedOutput)
   })
@@ -132,7 +142,12 @@ describe('FunctionBlockHandler', () => {
       workflowVariables: {},
       blockData: {},
       blockNameMapping: {},
-      _context: { workflowId: mockContext.workflowId, workspaceId: mockContext.workspaceId },
+      blockOutputSchemas: {},
+      _context: {
+        workflowId: mockContext.workflowId,
+        workspaceId: mockContext.workspaceId,
+        isDeployedContext: mockContext.isDeployedContext,
+      },
     }
 
     await handler.execute(mockContext, mockBlock, inputs)

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

@@ -23,7 +23,7 @@ export class FunctionBlockHandler implements BlockHandler {
       ? inputs.code.map((c: { content: string }) => c.content).join('\n')
       : inputs.code
 
-    const { blockData, blockNameMapping } = collectBlockData(ctx)
+    const { blockData, blockNameMapping, blockOutputSchemas } = collectBlockData(ctx)
 
     const result = await executeTool(
       'function_execute',
@@ -35,6 +35,7 @@ export class FunctionBlockHandler implements BlockHandler {
         workflowVariables: ctx.workflowVariables || {},
         blockData,
         blockNameMapping,
+        blockOutputSchemas,
         _context: {
           workflowId: ctx.workflowId,
           workspaceId: ctx.workspaceId,

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

@@ -1,24 +1,43 @@
+import { getBlockOutputs } from '@/lib/workflows/blocks/block-outputs'
 import { normalizeName } from '@/executor/constants'
 import type { ExecutionContext } from '@/executor/types'
+import type { OutputSchema } from '@/executor/utils/block-reference'
 
 export interface BlockDataCollection {
-  blockData: Record<string, any>
+  blockData: Record<string, unknown>
   blockNameMapping: Record<string, string>
+  blockOutputSchemas: Record<string, OutputSchema>
 }
 
 export function collectBlockData(ctx: ExecutionContext): BlockDataCollection {
-  const blockData: Record<string, any> = {}
+  const blockData: Record<string, unknown> = {}
   const blockNameMapping: Record<string, string> = {}
+  const blockOutputSchemas: Record<string, OutputSchema> = {}
 
   for (const [id, state] of ctx.blockStates.entries()) {
     if (state.output !== undefined) {
       blockData[id] = state.output
-      const workflowBlock = ctx.workflow?.blocks?.find((b) => b.id === id)
-      if (workflowBlock?.metadata?.name) {
-        blockNameMapping[normalizeName(workflowBlock.metadata.name)] = id
+    }
+
+    const workflowBlock = ctx.workflow?.blocks?.find((b) => b.id === id)
+    if (!workflowBlock) continue
+
+    if (workflowBlock.metadata?.name) {
+      blockNameMapping[normalizeName(workflowBlock.metadata.name)] = id
+    }
+
+    const blockType = workflowBlock.metadata?.id
+    if (blockType) {
+      const params = workflowBlock.config?.params as Record<string, unknown> | undefined
+      const subBlocks = params
+        ? Object.fromEntries(Object.entries(params).map(([k, v]) => [k, { value: v }]))
+        : undefined
+      const schema = getBlockOutputs(blockType, subBlocks)
+      if (schema && Object.keys(schema).length > 0) {
+        blockOutputSchemas[id] = schema
       }
     }
   }
 
-  return { blockData, blockNameMapping }
+  return { blockData, blockNameMapping, blockOutputSchemas }
 }

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

@@ -0,0 +1,255 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import {
+  type BlockReferenceContext,
+  InvalidFieldError,
+  resolveBlockReference,
+} from './block-reference'
+
+describe('resolveBlockReference', () => {
+  const createContext = (
+    overrides: Partial<BlockReferenceContext> = {}
+  ): BlockReferenceContext => ({
+    blockNameMapping: { start: 'block-1', agent: 'block-2' },
+    blockData: {},
+    blockOutputSchemas: {},
+    ...overrides,
+  })
+
+  describe('block name resolution', () => {
+    it('should return undefined when block name does not exist', () => {
+      const ctx = createContext()
+      const result = resolveBlockReference('unknown', ['field'], ctx)
+      expect(result).toBeUndefined()
+    })
+
+    it('should normalize block name before lookup', () => {
+      const ctx = createContext({
+        blockNameMapping: { myblock: 'block-1' },
+        blockData: { 'block-1': { value: 'test' } },
+      })
+
+      const result = resolveBlockReference('MyBlock', ['value'], ctx)
+      expect(result).toEqual({ value: 'test', blockId: 'block-1' })
+    })
+
+    it('should handle block names with spaces', () => {
+      const ctx = createContext({
+        blockNameMapping: { myblock: 'block-1' },
+        blockData: { 'block-1': { value: 'test' } },
+      })
+
+      const result = resolveBlockReference('My Block', ['value'], ctx)
+      expect(result).toEqual({ value: 'test', blockId: 'block-1' })
+    })
+  })
+
+  describe('field resolution', () => {
+    it('should return entire block output when no path specified', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { input: 'hello', other: 'data' } },
+      })
+
+      const result = resolveBlockReference('start', [], ctx)
+      expect(result).toEqual({
+        value: { input: 'hello', other: 'data' },
+        blockId: 'block-1',
+      })
+    })
+
+    it('should resolve simple field path', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { input: 'hello' } },
+      })
+
+      const result = resolveBlockReference('start', ['input'], ctx)
+      expect(result).toEqual({ value: 'hello', blockId: 'block-1' })
+    })
+
+    it('should resolve nested field path', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { response: { data: { name: 'test' } } } },
+      })
+
+      const result = resolveBlockReference('start', ['response', 'data', 'name'], ctx)
+      expect(result).toEqual({ value: 'test', blockId: 'block-1' })
+    })
+
+    it('should resolve array index path', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { items: ['a', 'b', 'c'] } },
+      })
+
+      const result = resolveBlockReference('start', ['items', '1'], ctx)
+      expect(result).toEqual({ value: 'b', blockId: 'block-1' })
+    })
+
+    it('should return undefined value when field exists but has no value', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { input: undefined } },
+        blockOutputSchemas: {
+          'block-1': { input: { type: 'string' } },
+        },
+      })
+
+      const result = resolveBlockReference('start', ['input'], ctx)
+      expect(result).toEqual({ value: undefined, blockId: 'block-1' })
+    })
+
+    it('should return null value when field has null', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { input: null } },
+      })
+
+      const result = resolveBlockReference('start', ['input'], ctx)
+      expect(result).toEqual({ value: null, blockId: 'block-1' })
+    })
+  })
+
+  describe('schema validation', () => {
+    it('should throw InvalidFieldError when field not in schema', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { existing: 'value' } },
+        blockOutputSchemas: {
+          'block-1': {
+            input: { type: 'string' },
+            conversationId: { type: 'string' },
+          },
+        },
+      })
+
+      expect(() => resolveBlockReference('start', ['invalid'], ctx)).toThrow(InvalidFieldError)
+      expect(() => resolveBlockReference('start', ['invalid'], ctx)).toThrow(
+        /"invalid" doesn't exist on block "start"/
+      )
+    })
+
+    it('should include available fields in error message', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': {} },
+        blockOutputSchemas: {
+          'block-1': {
+            input: { type: 'string' },
+            conversationId: { type: 'string' },
+            files: { type: 'files' },
+          },
+        },
+      })
+
+      try {
+        resolveBlockReference('start', ['typo'], ctx)
+        expect.fail('Should have thrown')
+      } catch (error) {
+        expect(error).toBeInstanceOf(InvalidFieldError)
+        const fieldError = error as InvalidFieldError
+        expect(fieldError.availableFields).toContain('input')
+        expect(fieldError.availableFields).toContain('conversationId')
+        expect(fieldError.availableFields).toContain('files')
+      }
+    })
+
+    it('should allow valid field even when value is undefined', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': {} },
+        blockOutputSchemas: {
+          'block-1': { input: { type: 'string' } },
+        },
+      })
+
+      const result = resolveBlockReference('start', ['input'], ctx)
+      expect(result).toEqual({ value: undefined, blockId: 'block-1' })
+    })
+
+    it('should validate path when block has no output yet', () => {
+      const ctx = createContext({
+        blockData: {},
+        blockOutputSchemas: {
+          'block-1': { input: { type: 'string' } },
+        },
+      })
+
+      expect(() => resolveBlockReference('start', ['invalid'], ctx)).toThrow(InvalidFieldError)
+    })
+
+    it('should return undefined for valid field when block has no output', () => {
+      const ctx = createContext({
+        blockData: {},
+        blockOutputSchemas: {
+          'block-1': { input: { type: 'string' } },
+        },
+      })
+
+      const result = resolveBlockReference('start', ['input'], ctx)
+      expect(result).toEqual({ value: undefined, blockId: 'block-1' })
+    })
+  })
+
+  describe('without schema (pass-through mode)', () => {
+    it('should return undefined value without throwing when no schema', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { existing: 'value' } },
+      })
+
+      const result = resolveBlockReference('start', ['missing'], ctx)
+      expect(result).toEqual({ value: undefined, blockId: 'block-1' })
+    })
+  })
+
+  describe('file type handling', () => {
+    it('should allow file property access', () => {
+      const ctx = createContext({
+        blockData: {
+          'block-1': {
+            files: [{ name: 'test.txt', url: 'http://example.com/file' }],
+          },
+        },
+        blockOutputSchemas: {
+          'block-1': { files: { type: 'files' } },
+        },
+      })
+
+      const result = resolveBlockReference('start', ['files', '0', 'name'], ctx)
+      expect(result).toEqual({ value: 'test.txt', blockId: 'block-1' })
+    })
+
+    it('should validate file property names', () => {
+      const ctx = createContext({
+        blockData: { 'block-1': { files: [] } },
+        blockOutputSchemas: {
+          'block-1': { files: { type: 'files' } },
+        },
+      })
+
+      expect(() => resolveBlockReference('start', ['files', '0', 'invalid'], ctx)).toThrow(
+        InvalidFieldError
+      )
+    })
+  })
+})
+
+describe('InvalidFieldError', () => {
+  it('should have correct properties', () => {
+    const error = new InvalidFieldError('myBlock', 'invalid.path', ['field1', 'field2'])
+
+    expect(error.blockName).toBe('myBlock')
+    expect(error.fieldPath).toBe('invalid.path')
+    expect(error.availableFields).toEqual(['field1', 'field2'])
+    expect(error.name).toBe('InvalidFieldError')
+  })
+
+  it('should format message correctly', () => {
+    const error = new InvalidFieldError('start', 'typo', ['input', 'files'])
+
+    expect(error.message).toBe(
+      '"typo" doesn\'t exist on block "start". Available fields: input, files'
+    )
+  })
+
+  it('should handle empty available fields', () => {
+    const error = new InvalidFieldError('start', 'field', [])
+
+    expect(error.message).toBe('"field" doesn\'t exist on block "start". Available fields: none')
+  })
+})

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

@@ -0,0 +1,210 @@
+import { USER_FILE_ACCESSIBLE_PROPERTIES } from '@/lib/workflows/types'
+import { normalizeName } from '@/executor/constants'
+import { navigatePath } from '@/executor/variables/resolvers/reference'
+
+export type OutputSchema = Record<string, { type?: string; description?: string } | unknown>
+
+export interface BlockReferenceContext {
+  blockNameMapping: Record<string, string>
+  blockData: Record<string, unknown>
+  blockOutputSchemas?: Record<string, OutputSchema>
+}
+
+export interface BlockReferenceResult {
+  value: unknown
+  blockId: string
+}
+
+export class InvalidFieldError extends Error {
+  constructor(
+    public readonly blockName: string,
+    public readonly fieldPath: string,
+    public readonly availableFields: string[]
+  ) {
+    super(
+      `"${fieldPath}" doesn't exist on block "${blockName}". ` +
+        `Available fields: ${availableFields.length > 0 ? availableFields.join(', ') : 'none'}`
+    )
+    this.name = 'InvalidFieldError'
+  }
+}
+
+function isFileType(value: unknown): boolean {
+  if (typeof value !== 'object' || value === null) return false
+  const typed = value as { type?: string }
+  return typed.type === 'file[]' || typed.type === 'files'
+}
+
+function isArrayType(value: unknown): value is { type: 'array'; items?: unknown } {
+  if (typeof value !== 'object' || value === null) return false
+  return (value as { type?: string }).type === 'array'
+}
+
+function getArrayItems(schema: unknown): unknown {
+  if (typeof schema !== 'object' || schema === null) return undefined
+  return (schema as { items?: unknown }).items
+}
+
+function getProperties(schema: unknown): Record<string, unknown> | undefined {
+  if (typeof schema !== 'object' || schema === null) return undefined
+  const props = (schema as { properties?: unknown }).properties
+  return typeof props === 'object' && props !== null
+    ? (props as Record<string, unknown>)
+    : undefined
+}
+
+function lookupField(schema: unknown, fieldName: string): unknown | undefined {
+  if (typeof schema !== 'object' || schema === null) return undefined
+  const typed = schema as Record<string, unknown>
+
+  if (fieldName in typed) {
+    return typed[fieldName]
+  }
+
+  const props = getProperties(schema)
+  if (props && fieldName in props) {
+    return props[fieldName]
+  }
+
+  return undefined
+}
+
+function isPathInSchema(schema: OutputSchema | undefined, pathParts: string[]): boolean {
+  if (!schema || pathParts.length === 0) {
+    return true
+  }
+
+  let current: unknown = schema
+
+  for (let i = 0; i < pathParts.length; i++) {
+    const part = pathParts[i]
+
+    if (current === null || current === undefined) {
+      return false
+    }
+
+    if (/^\d+$/.test(part)) {
+      if (isFileType(current)) {
+        const nextPart = pathParts[i + 1]
+        return (
+          !nextPart ||
+          USER_FILE_ACCESSIBLE_PROPERTIES.includes(
+            nextPart as (typeof USER_FILE_ACCESSIBLE_PROPERTIES)[number]
+          )
+        )
+      }
+      if (isArrayType(current)) {
+        current = getArrayItems(current)
+      }
+      continue
+    }
+
+    const arrayMatch = part.match(/^([^[]+)\[(\d+)\]$/)
+    if (arrayMatch) {
+      const [, prop] = arrayMatch
+      const fieldDef = lookupField(current, prop)
+      if (!fieldDef) return false
+
+      if (isFileType(fieldDef)) {
+        const nextPart = pathParts[i + 1]
+        return (
+          !nextPart ||
+          USER_FILE_ACCESSIBLE_PROPERTIES.includes(
+            nextPart as (typeof USER_FILE_ACCESSIBLE_PROPERTIES)[number]
+          )
+        )
+      }
+
+      current = isArrayType(fieldDef) ? getArrayItems(fieldDef) : fieldDef
+      continue
+    }
+
+    if (
+      isFileType(current) &&
+      USER_FILE_ACCESSIBLE_PROPERTIES.includes(
+        part as (typeof USER_FILE_ACCESSIBLE_PROPERTIES)[number]
+      )
+    ) {
+      return true
+    }
+
+    const fieldDef = lookupField(current, part)
+    if (fieldDef !== undefined) {
+      if (isFileType(fieldDef)) {
+        const nextPart = pathParts[i + 1]
+        if (!nextPart) return true
+        if (/^\d+$/.test(nextPart)) {
+          const afterIndex = pathParts[i + 2]
+          return (
+            !afterIndex ||
+            USER_FILE_ACCESSIBLE_PROPERTIES.includes(
+              afterIndex as (typeof USER_FILE_ACCESSIBLE_PROPERTIES)[number]
+            )
+          )
+        }
+        return USER_FILE_ACCESSIBLE_PROPERTIES.includes(
+          nextPart as (typeof USER_FILE_ACCESSIBLE_PROPERTIES)[number]
+        )
+      }
+      current = fieldDef
+      continue
+    }
+
+    if (isArrayType(current)) {
+      const items = getArrayItems(current)
+      const itemField = lookupField(items, part)
+      if (itemField !== undefined) {
+        current = itemField
+        continue
+      }
+    }
+
+    return false
+  }
+
+  return true
+}
+
+function getSchemaFieldNames(schema: OutputSchema | undefined): string[] {
+  if (!schema) return []
+  return Object.keys(schema)
+}
+
+export function resolveBlockReference(
+  blockName: string,
+  pathParts: string[],
+  context: BlockReferenceContext
+): BlockReferenceResult | undefined {
+  const normalizedName = normalizeName(blockName)
+  const blockId = context.blockNameMapping[normalizedName]
+
+  if (!blockId) {
+    return undefined
+  }
+
+  const blockOutput = context.blockData[blockId]
+  const schema = context.blockOutputSchemas?.[blockId]
+
+  if (blockOutput === undefined) {
+    if (schema && pathParts.length > 0) {
+      if (!isPathInSchema(schema, pathParts)) {
+        throw new InvalidFieldError(blockName, pathParts.join('.'), getSchemaFieldNames(schema))
+      }
+    }
+    return { value: undefined, blockId }
+  }
+
+  if (pathParts.length === 0) {
+    return { value: blockOutput, blockId }
+  }
+
+  const value = navigatePath(blockOutput, pathParts)
+
+  if (value === undefined && schema) {
+    if (!isPathInSchema(schema, pathParts)) {
+      throw new InvalidFieldError(blockName, pathParts.join('.'), getSchemaFieldNames(schema))
+    }
+  }
+
+  return { value, blockId }
+}

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

@@ -1,11 +1,15 @@
 import { getBlockOutputs } from '@/lib/workflows/blocks/block-outputs'
-import { USER_FILE_ACCESSIBLE_PROPERTIES } from '@/lib/workflows/types'
 import {
   isReference,
   normalizeName,
   parseReferencePath,
   SPECIAL_REFERENCE_PREFIXES,
 } from '@/executor/constants'
+import {
+  InvalidFieldError,
+  type OutputSchema,
+  resolveBlockReference,
+} from '@/executor/utils/block-reference'
 import {
   navigatePath,
   type ResolutionContext,
@@ -14,123 +18,6 @@ import {
 import type { SerializedBlock, SerializedWorkflow } from '@/serializer/types'
 import { getTool } from '@/tools/utils'
 
-function isPathInOutputSchema(
-  outputs: Record<string, any> | undefined,
-  pathParts: string[]
-): boolean {
-  if (!outputs || pathParts.length === 0) {
-    return true
-  }
-
-  const isFileArrayType = (value: any): boolean =>
-    value?.type === 'file[]' || value?.type === 'files'
-
-  let current: any = outputs
-  for (let i = 0; i < pathParts.length; i++) {
-    const part = pathParts[i]
-
-    const arrayMatch = part.match(/^([^[]+)\[(\d+)\]$/)
-    if (arrayMatch) {
-      const [, prop] = arrayMatch
-      let fieldDef: any
-
-      if (prop in current) {
-        fieldDef = current[prop]
-      } else if (current.properties && prop in current.properties) {
-        fieldDef = current.properties[prop]
-      } else if (current.type === 'array' && current.items) {
-        if (current.items.properties && prop in current.items.properties) {
-          fieldDef = current.items.properties[prop]
-        } else if (prop in current.items) {
-          fieldDef = current.items[prop]
-        }
-      }
-
-      if (!fieldDef) {
-        return false
-      }
-
-      if (isFileArrayType(fieldDef)) {
-        if (i + 1 < pathParts.length) {
-          return USER_FILE_ACCESSIBLE_PROPERTIES.includes(pathParts[i + 1] as any)
-        }
-        return true
-      }
-
-      if (fieldDef.type === 'array' && fieldDef.items) {
-        current = fieldDef.items
-        continue
-      }
-
-      current = fieldDef
-      continue
-    }
-
-    if (/^\d+$/.test(part)) {
-      if (isFileArrayType(current)) {
-        if (i + 1 < pathParts.length) {
-          const nextPart = pathParts[i + 1]
-          return USER_FILE_ACCESSIBLE_PROPERTIES.includes(nextPart as any)
-        }
-        return true
-      }
-      continue
-    }
-
-    if (current === null || current === undefined) {
-      return false
-    }
-
-    if (part in current) {
-      const nextCurrent = current[part]
-      if (nextCurrent?.type === 'file[]' && i + 1 < pathParts.length) {
-        const nextPart = pathParts[i + 1]
-        if (/^\d+$/.test(nextPart) && i + 2 < pathParts.length) {
-          const propertyPart = pathParts[i + 2]
-          return USER_FILE_ACCESSIBLE_PROPERTIES.includes(propertyPart as any)
-        }
-      }
-      current = nextCurrent
-      continue
-    }
-
-    if (current.properties && part in current.properties) {
-      current = current.properties[part]
-      continue
-    }
-
-    if (current.type === 'array' && current.items) {
-      if (current.items.properties && part in current.items.properties) {
-        current = current.items.properties[part]
-        continue
-      }
-      if (part in current.items) {
-        current = current.items[part]
-        continue
-      }
-    }
-
-    if (isFileArrayType(current) && USER_FILE_ACCESSIBLE_PROPERTIES.includes(part as any)) {
-      return true
-    }
-
-    if ('type' in current && typeof current.type === 'string') {
-      if (!current.properties && !current.items) {
-        return false
-      }
-    }
-
-    return false
-  }
-
-  return true
-}
-
-function getSchemaFieldNames(outputs: Record<string, any> | undefined): string[] {
-  if (!outputs) return []
-  return Object.keys(outputs)
-}
-
 export class BlockResolver implements Resolver {
   private nameToBlockId: Map<string, string>
   private blockById: Map<string, SerializedBlock>
@@ -170,83 +57,94 @@ export class BlockResolver implements Resolver {
       return undefined
     }
 
-    const block = this.blockById.get(blockId)
+    const block = this.blockById.get(blockId)!
     const output = this.getBlockOutput(blockId, context)
 
-    if (output === undefined) {
+    const blockData: Record<string, unknown> = {}
+    const blockOutputSchemas: Record<string, OutputSchema> = {}
+
+    if (output !== undefined) {
+      blockData[blockId] = output
+    }
+
+    const blockType = block.metadata?.id
+    const params = block.config?.params as Record<string, unknown> | undefined
+    const subBlocks = params
+      ? Object.fromEntries(Object.entries(params).map(([k, v]) => [k, { value: v }]))
+      : undefined
+    const toolId = block.config?.tool
+    const toolConfig = toolId ? getTool(toolId) : undefined
+    const outputSchema =
+      toolConfig?.outputs ?? (blockType ? getBlockOutputs(blockType, subBlocks) : block.outputs)
+
+    if (outputSchema && Object.keys(outputSchema).length > 0) {
+      blockOutputSchemas[blockId] = outputSchema
+    }
+
+    try {
+      const result = resolveBlockReference(blockName, pathParts, {
+        blockNameMapping: Object.fromEntries(this.nameToBlockId),
+        blockData,
+        blockOutputSchemas,
+      })!
+
+      if (result.value !== undefined) {
+        return result.value
+      }
+
+      return this.handleBackwardsCompat(block, output, pathParts)
+    } catch (error) {
+      if (error instanceof InvalidFieldError) {
+        const fallback = this.handleBackwardsCompat(block, output, pathParts)
+        if (fallback !== undefined) {
+          return fallback
+        }
+        throw new Error(error.message)
+      }
+      throw error
+    }
+  }
+
+  private handleBackwardsCompat(
+    block: SerializedBlock,
+    output: unknown,
+    pathParts: string[]
+  ): unknown {
+    if (output === undefined || pathParts.length === 0) {
       return undefined
     }
-    if (pathParts.length === 0) {
-      return output
-    }
 
-    // Try the original path first
-    let result = navigatePath(output, pathParts)
-
-    // If successful, return it immediately
-    if (result !== undefined) {
-      return result
-    }
-
-    // Response block backwards compatibility:
-    // Old: <responseBlock.response.data> -> New: <responseBlock.data>
-    // Only apply fallback if:
-    // 1. Block type is 'response'
-    // 2. Path starts with 'response.'
-    // 3. Output doesn't have a 'response' key (confirming it's the new format)
     if (
-      block?.metadata?.id === 'response' &&
+      block.metadata?.id === 'response' &&
       pathParts[0] === 'response' &&
-      output?.response === undefined
+      (output as Record<string, unknown>)?.response === undefined
     ) {
       const adjustedPathParts = pathParts.slice(1)
       if (adjustedPathParts.length === 0) {
         return output
       }
-      result = navigatePath(output, adjustedPathParts)
-      if (result !== undefined) {
-        return result
+      const fallbackResult = navigatePath(output, adjustedPathParts)
+      if (fallbackResult !== undefined) {
+        return fallbackResult
       }
     }
 
-    // Workflow block backwards compatibility:
-    // Old: <workflowBlock.result.response.data> -> New: <workflowBlock.result.data>
-    // Only apply fallback if:
-    // 1. Block type is 'workflow' or 'workflow_input'
-    // 2. Path starts with 'result.response.'
-    // 3. output.result.response doesn't exist (confirming child used new format)
     const isWorkflowBlock =
-      block?.metadata?.id === 'workflow' || block?.metadata?.id === 'workflow_input'
+      block.metadata?.id === 'workflow' || block.metadata?.id === 'workflow_input'
+    const outputRecord = output as Record<string, Record<string, unknown> | undefined>
     if (
       isWorkflowBlock &&
       pathParts[0] === 'result' &&
       pathParts[1] === 'response' &&
-      output?.result?.response === undefined
+      outputRecord?.result?.response === undefined
     ) {
       const adjustedPathParts = ['result', ...pathParts.slice(2)]
-      result = navigatePath(output, adjustedPathParts)
-      if (result !== undefined) {
-        return result
+      const fallbackResult = navigatePath(output, adjustedPathParts)
+      if (fallbackResult !== undefined) {
+        return fallbackResult
       }
     }
 
-    const blockType = block?.metadata?.id
-    const params = block?.config?.params as Record<string, unknown> | undefined
-    const subBlocks = params
-      ? Object.fromEntries(Object.entries(params).map(([k, v]) => [k, { value: v }]))
-      : undefined
-    const toolId = block?.config?.tool
-    const toolConfig = toolId ? getTool(toolId) : undefined
-    const outputSchema =
-      toolConfig?.outputs ?? (blockType ? getBlockOutputs(blockType, subBlocks) : block?.outputs)
-    const schemaFields = getSchemaFieldNames(outputSchema)
-    if (schemaFields.length > 0 && !isPathInOutputSchema(outputSchema, pathParts)) {
-      throw new Error(
-        `"${pathParts.join('.')}" doesn't exist on block "${blockName}". ` +
-          `Available fields: ${schemaFields.join(', ')}`
-      )
-    }
-
     return undefined
   }
 

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

@@ -27,23 +27,28 @@ export function navigatePath(obj: any, path: string[]): any {
       return undefined
     }
 
-    // Handle array indexing like "items[0]" or just numeric indices
-    const arrayMatch = part.match(/^([^[]+)\[(\d+)\](.*)$/)
+    const arrayMatch = part.match(/^([^[]+)(\[.+)$/)
     if (arrayMatch) {
-      // Handle complex array access like "items[0]"
-      const [, prop, index] = arrayMatch
+      const [, prop, bracketsPart] = arrayMatch
       current = current[prop]
       if (current === undefined || current === null) {
         return undefined
       }
-      const idx = Number.parseInt(index, 10)
-      current = Array.isArray(current) ? current[idx] : undefined
+
+      const indices = bracketsPart.match(/\[(\d+)\]/g)
+      if (indices) {
+        for (const indexMatch of indices) {
+          if (current === null || current === undefined) {
+            return undefined
+          }
+          const idx = Number.parseInt(indexMatch.slice(1, -1), 10)
+          current = Array.isArray(current) ? current[idx] : undefined
+        }
+      }
     } else if (/^\d+$/.test(part)) {
-      // Handle plain numeric index
       const index = Number.parseInt(part, 10)
       current = Array.isArray(current) ? current[index] : undefined
     } else {
-      // Handle regular property access
       current = current[part]
     }
   }

apps/sim/lib/execution/isolated-vm-worker.cjs

@@ -130,7 +130,11 @@ async function executeCode(request) {
     await jail.set('environmentVariables', new ivm.ExternalCopy(envVars).copyInto())
 
     for (const [key, value] of Object.entries(contextVariables)) {
-      await jail.set(key, new ivm.ExternalCopy(value).copyInto())
+      if (value === undefined) {
+        await jail.set(key, undefined)
+      } else {
+        await jail.set(key, new ivm.ExternalCopy(value).copyInto())
+      }
     }
 
     const fetchCallback = new ivm.Reference(async (url, optionsJson) => {

apps/sim/tools/function/execute.test.ts

@@ -56,6 +56,7 @@ describe('Function Execute Tool', () => {
         workflowVariables: {},
         blockData: {},
         blockNameMapping: {},
+        blockOutputSchemas: {},
         isCustomTool: false,
         language: 'javascript',
         timeout: 5000,
@@ -83,6 +84,7 @@ describe('Function Execute Tool', () => {
         workflowVariables: {},
         blockData: {},
         blockNameMapping: {},
+        blockOutputSchemas: {},
         isCustomTool: false,
         language: 'javascript',
         workflowId: undefined,
@@ -101,6 +103,7 @@ describe('Function Execute Tool', () => {
         workflowVariables: {},
         blockData: {},
         blockNameMapping: {},
+        blockOutputSchemas: {},
         isCustomTool: false,
         language: 'javascript',
         workflowId: undefined,

apps/sim/tools/function/execute.ts

@@ -53,6 +53,13 @@ export const functionExecuteTool: ToolConfig<CodeExecutionInput, CodeExecutionOu
       description: 'Mapping of block names to block IDs',
       default: {},
     },
+    blockOutputSchemas: {
+      type: 'object',
+      required: false,
+      visibility: 'hidden',
+      description: 'Mapping of block IDs to their output schemas for validation',
+      default: {},
+    },
     workflowVariables: {
       type: 'object',
       required: false,
@@ -81,6 +88,7 @@ export const functionExecuteTool: ToolConfig<CodeExecutionInput, CodeExecutionOu
         workflowVariables: params.workflowVariables || {},
         blockData: params.blockData || {},
         blockNameMapping: params.blockNameMapping || {},
+        blockOutputSchemas: params.blockOutputSchemas || {},
         workflowId: params._context?.workflowId,
         isCustomTool: params.isCustomTool || false,
       }

apps/sim/tools/function/types.ts

@@ -11,6 +11,7 @@ export interface CodeExecutionInput {
   workflowVariables?: Record<string, unknown>
   blockData?: Record<string, unknown>
   blockNameMapping?: Record<string, string>
+  blockOutputSchemas?: Record<string, Record<string, unknown>>
   _context?: {
     workflowId?: string
   }