fix(child-workflow-error-spans): pass trace-spans accurately in block logs (#3054)

* fix(child-workflow): must bypass hiddenFromDisplay config

* fix passing of spans to be in block log

* keep fallback for backwards compat

* fix error message formatting

* clean up

apps/sim/app/workspace/[workspaceId]/logs/components/log-details/components/trace-spans/trace-spans.tsx

@@ -57,40 +57,6 @@ function useSetToggle() {
   )
 }
 
-/**
- * Generates a unique key for a trace span
- */
-function getSpanKey(span: TraceSpan): string {
-  if (span.id) {
-    return span.id
-  }
-  const name = span.name || 'span'
-  const start = span.startTime || 'unknown-start'
-  const end = span.endTime || 'unknown-end'
-  return `${name}|${start}|${end}`
-}
-
-/**
- * Merges multiple arrays of trace span children, deduplicating by span key
- */
-function mergeTraceSpanChildren(...groups: TraceSpan[][]): TraceSpan[] {
-  const merged: TraceSpan[] = []
-  const seen = new Set<string>()
-
-  groups.forEach((group) => {
-    group.forEach((child) => {
-      const key = getSpanKey(child)
-      if (seen.has(key)) {
-        return
-      }
-      seen.add(key)
-      merged.push(child)
-    })
-  })
-
-  return merged
-}
-
 /**
  * Parses a time value to milliseconds
  */
@@ -116,34 +82,16 @@ function hasErrorInTree(span: TraceSpan): boolean {
 
 /**
  * Normalizes and sorts trace spans recursively.
- * Merges children from both span.children and span.output.childTraceSpans,
- * deduplicates them, and sorts by start time.
+ * Deduplicates children and sorts by start time.
  */
 function normalizeAndSortSpans(spans: TraceSpan[]): TraceSpan[] {
   return spans
     .map((span) => {
       const enrichedSpan: TraceSpan = { ...span }
 
-      // Clean output by removing childTraceSpans after extracting
-      if (enrichedSpan.output && typeof enrichedSpan.output === 'object') {
-        enrichedSpan.output = { ...enrichedSpan.output }
-        if ('childTraceSpans' in enrichedSpan.output) {
-          const { childTraceSpans, ...cleanOutput } = enrichedSpan.output as {
-            childTraceSpans?: TraceSpan[]
-          } & Record<string, unknown>
-          enrichedSpan.output = cleanOutput
-        }
-      }
-
-      // Merge and deduplicate children from both sources
-      const directChildren = Array.isArray(span.children) ? span.children : []
-      const outputChildren = Array.isArray(span.output?.childTraceSpans)
-        ? (span.output!.childTraceSpans as TraceSpan[])
-        : []
-
-      const mergedChildren = mergeTraceSpanChildren(directChildren, outputChildren)
-      enrichedSpan.children =
-        mergedChildren.length > 0 ? normalizeAndSortSpans(mergedChildren) : undefined
+      // Process and deduplicate children
+      const children = Array.isArray(span.children) ? span.children : []
+      enrichedSpan.children = children.length > 0 ? normalizeAndSortSpans(children) : undefined
 
       return enrichedSpan
     })

apps/sim/app/workspace/[workspaceId]/logs/components/log-details/log-details.tsx

@@ -18,6 +18,7 @@ import {
 import { ScrollArea } from '@/components/ui/scroll-area'
 import { BASE_EXECUTION_CHARGE } from '@/lib/billing/constants'
 import { cn } from '@/lib/core/utils/cn'
+import { filterHiddenOutputKeys } from '@/lib/logs/execution/trace-spans/trace-spans'
 import {
   ExecutionSnapshot,
   FileCards,
@@ -274,16 +275,13 @@ export const LogDetails = memo(function LogDetails({
     return isWorkflowExecutionLog && log?.cost
   }, [log, isWorkflowExecutionLog])
 
-  // Extract and clean the workflow final output (remove childTraceSpans for cleaner display)
+  // Extract and clean the workflow final output (recursively remove hidden keys for cleaner display)
   const workflowOutput = useMemo(() => {
     const executionData = log?.executionData as
       | { finalOutput?: Record<string, unknown> }
       | undefined
     if (!executionData?.finalOutput) return null
-    const { childTraceSpans, ...cleanOutput } = executionData.finalOutput as {
-      childTraceSpans?: unknown
-    } & Record<string, unknown>
-    return cleanOutput
+    return filterHiddenOutputKeys(executionData.finalOutput) as Record<string, unknown>
   }, [log?.executionData])
 
   useEffect(() => {

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

@@ -39,8 +39,8 @@ interface WorkflowStackEntry {
 
 /**
  * Extracts child trace spans from a workflow block's execution data.
- * Checks both the `children` property (where trace span processing moves them)
- * and the legacy `output.childTraceSpans` for compatibility.
+ * Checks `children` property (where trace-spans processing puts them),
+ * with fallback to `output.childTraceSpans` for old stored logs.
  */
 function extractChildTraceSpans(blockExecution: BlockExecutionData | undefined): TraceSpan[] {
   if (!blockExecution) return []
@@ -49,6 +49,7 @@ function extractChildTraceSpans(blockExecution: BlockExecutionData | undefined):
     return blockExecution.children
   }
 
+  // Backward compat: old stored logs may have childTraceSpans in output
   if (blockExecution.output && typeof blockExecution.output === 'object') {
     const output = blockExecution.output as Record<string, unknown>
     if (Array.isArray(output.childTraceSpans)) {

apps/sim/executor/execution/block-executor.ts

@@ -152,6 +152,9 @@ export class BlockExecutor {
         blockLog.durationMs = duration
         blockLog.success = true
         blockLog.output = filterOutputForLog(block.metadata?.id || '', normalizedOutput, { block })
+        if (normalizedOutput.childTraceSpans && Array.isArray(normalizedOutput.childTraceSpans)) {
+          blockLog.childTraceSpans = normalizedOutput.childTraceSpans
+        }
       }
 
       this.state.setBlockOutput(node.id, normalizedOutput, duration)
@@ -245,6 +248,10 @@ export class BlockExecutor {
       blockLog.error = errorMessage
       blockLog.input = this.sanitizeInputsForLog(input)
       blockLog.output = filterOutputForLog(block.metadata?.id || '', errorOutput, { block })
+
+      if (errorOutput.childTraceSpans && Array.isArray(errorOutput.childTraceSpans)) {
+        blockLog.childTraceSpans = errorOutput.childTraceSpans
+      }
     }
 
     logger.error(

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

@@ -118,7 +118,7 @@ describe('WorkflowBlockHandler', () => {
       }
 
       await expect(handler.execute(deepContext, mockBlock, inputs)).rejects.toThrow(
-        'Error in child workflow "child-workflow-id": Maximum workflow nesting depth of 10 exceeded'
+        '"child-workflow-id" failed: Maximum workflow nesting depth of 10 exceeded'
       )
     })
 
@@ -132,7 +132,7 @@ describe('WorkflowBlockHandler', () => {
       })
 
       await expect(handler.execute(mockContext, mockBlock, inputs)).rejects.toThrow(
-        'Error in child workflow "non-existent-workflow": Child workflow non-existent-workflow not found'
+        '"non-existent-workflow" failed: Child workflow non-existent-workflow not found'
       )
     })
 
@@ -142,7 +142,7 @@ describe('WorkflowBlockHandler', () => {
       mockFetch.mockRejectedValueOnce(new Error('Network error'))
 
       await expect(handler.execute(mockContext, mockBlock, inputs)).rejects.toThrow(
-        'Error in child workflow "child-workflow-id": Network error'
+        '"child-workflow-id" failed: Network error'
       )
     })
   })
@@ -212,7 +212,7 @@ describe('WorkflowBlockHandler', () => {
 
       expect(() =>
         (handler as any).mapChildOutputToParent(childResult, 'child-id', 'Child Workflow', 100)
-      ).toThrow('Error in child workflow "Child Workflow": Child workflow failed')
+      ).toThrow('"Child Workflow" failed: Child workflow failed')
 
       try {
         ;(handler as any).mapChildOutputToParent(childResult, 'child-id', 'Child Workflow', 100)

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

@@ -52,6 +52,11 @@ export class WorkflowBlockHandler implements BlockHandler {
       throw new Error('No workflow selected for execution')
     }
 
+    // Initialize with registry name, will be updated with loaded workflow name
+    const { workflows } = useWorkflowRegistry.getState()
+    const workflowMetadata = workflows[workflowId]
+    let childWorkflowName = workflowMetadata?.name || workflowId
+
     try {
       const currentDepth = (ctx.workflowId?.split('_sub_').length || 1) - 1
       if (currentDepth >= DEFAULTS.MAX_WORKFLOW_DEPTH) {
@@ -75,9 +80,8 @@ export class WorkflowBlockHandler implements BlockHandler {
         throw new Error(`Child workflow ${workflowId} not found`)
       }
 
-      const { workflows } = useWorkflowRegistry.getState()
-      const workflowMetadata = workflows[workflowId]
-      const childWorkflowName = workflowMetadata?.name || childWorkflow.name || 'Unknown Workflow'
+      // Update with loaded workflow name (more reliable than registry)
+      childWorkflowName = workflowMetadata?.name || childWorkflow.name || 'Unknown Workflow'
 
       logger.info(
         `Executing child workflow: ${childWorkflowName} (${workflowId}) at depth ${currentDepth}`
@@ -142,11 +146,6 @@ export class WorkflowBlockHandler implements BlockHandler {
     } catch (error: unknown) {
       logger.error(`Error executing child workflow ${workflowId}:`, error)
 
-      const { workflows } = useWorkflowRegistry.getState()
-      const workflowMetadata = workflows[workflowId]
-      const childWorkflowName = workflowMetadata?.name || workflowId
-
-      const originalError = error instanceof Error ? error.message : 'Unknown error'
       let childTraceSpans: WorkflowTraceSpan[] = []
       let executionResult: ExecutionResult | undefined
 
@@ -165,8 +164,11 @@ export class WorkflowBlockHandler implements BlockHandler {
         childTraceSpans = error.childTraceSpans
       }
 
+      // Build a cleaner error message for nested workflow errors
+      const errorMessage = this.buildNestedWorkflowErrorMessage(childWorkflowName, error)
+
       throw new ChildWorkflowError({
-        message: `Error in child workflow "${childWorkflowName}": ${originalError}`,
+        message: errorMessage,
         childWorkflowName,
         childTraceSpans,
         executionResult,
@@ -175,6 +177,72 @@ export class WorkflowBlockHandler implements BlockHandler {
     }
   }
 
+  /**
+   * Builds a cleaner error message for nested workflow errors.
+   * Parses nested error messages to extract workflow chain and root error.
+   */
+  private buildNestedWorkflowErrorMessage(childWorkflowName: string, error: unknown): string {
+    const originalError = error instanceof Error ? error.message : 'Unknown error'
+
+    // Extract any nested workflow names from the error message
+    const { chain, rootError } = this.parseNestedWorkflowError(originalError)
+
+    // Add current workflow to the beginning of the chain
+    chain.unshift(childWorkflowName)
+
+    // If we have a chain (nested workflows), format nicely
+    if (chain.length > 1) {
+      return `Workflow chain: ${chain.join(' → ')} | ${rootError}`
+    }
+
+    // Single workflow failure
+    return `"${childWorkflowName}" failed: ${rootError}`
+  }
+
+  /**
+   * Parses a potentially nested workflow error message to extract:
+   * - The chain of workflow names
+   * - The actual root error message (preserving the block prefix for the failing block)
+   *
+   * Handles formats like:
+   * - "workflow-name" failed: error
+   * - [block_type] Block Name: "workflow-name" failed: error
+   * - Workflow chain: A → B | error
+   */
+  private parseNestedWorkflowError(message: string): { chain: string[]; rootError: string } {
+    const chain: string[] = []
+    const remaining = message
+
+    // First, check if it's already in chain format
+    const chainMatch = remaining.match(/^Workflow chain: (.+?) \| (.+)$/)
+    if (chainMatch) {
+      const chainPart = chainMatch[1]
+      const errorPart = chainMatch[2]
+      chain.push(...chainPart.split(' → ').map((s) => s.trim()))
+      return { chain, rootError: errorPart }
+    }
+
+    // Extract workflow names from patterns like:
+    // - "workflow-name" failed:
+    // - [block_type] Block Name: "workflow-name" failed:
+    const workflowPattern = /(?:\[[^\]]+\]\s*[^:]+:\s*)?"([^"]+)"\s*failed:\s*/g
+    let match: RegExpExecArray | null
+    let lastIndex = 0
+
+    match = workflowPattern.exec(remaining)
+    while (match !== null) {
+      chain.push(match[1])
+      lastIndex = match.index + match[0].length
+      match = workflowPattern.exec(remaining)
+    }
+
+    // The root error is everything after the last match
+    // Keep the block prefix (e.g., [function] Function 1:) so we know which block failed
+    const rootError = lastIndex > 0 ? remaining.slice(lastIndex) : remaining
+
+    return { chain, rootError: rootError.trim() || 'Unknown error' }
+  }
+
   private async loadChildWorkflow(workflowId: string) {
     const headers = await buildAuthHeaders()
     const url = buildAPIUrl(`/api/workflows/${workflowId}`)
@@ -444,7 +512,7 @@ export class WorkflowBlockHandler implements BlockHandler {
     if (!success) {
       logger.warn(`Child workflow ${childWorkflowName} failed`)
       throw new ChildWorkflowError({
-        message: `Error in child workflow "${childWorkflowName}": ${childResult.error || 'Child workflow execution failed'}`,
+        message: `"${childWorkflowName}" failed: ${childResult.error || 'Child workflow execution failed'}`,
         childWorkflowName,
         childTraceSpans: childTraceSpans || [],
       })

apps/sim/executor/types.ts

@@ -114,6 +114,12 @@ export interface BlockLog {
   loopId?: string
   parallelId?: string
   iterationIndex?: number
+  /**
+   * Child workflow trace spans for nested workflow execution.
+   * Stored separately from output to keep output clean for display
+   * while preserving data for trace-spans processing.
+   */
+  childTraceSpans?: TraceSpan[]
 }
 
 export interface ExecutionMetadata {

apps/sim/executor/utils/output-filter.ts

@@ -1,3 +1,4 @@
+import { filterHiddenOutputKeys } from '@/lib/logs/execution/trace-spans/trace-spans'
 import { getBlock } from '@/blocks'
 import { isHiddenFromDisplay } from '@/blocks/types'
 import { isTriggerBehavior, isTriggerInternalKey } from '@/executor/constants'
@@ -7,6 +8,7 @@ import type { SerializedBlock } from '@/serializer/types'
 /**
  * Filters block output for logging/display purposes.
  * Removes internal fields and fields marked with hiddenFromDisplay.
+ * Also recursively filters globally hidden keys from nested objects.
  *
  * @param blockType - The block type string (e.g., 'human_in_the_loop', 'workflow')
  * @param output - The raw block output to filter
@@ -44,7 +46,8 @@ export function filterOutputForLog(
       continue
     }
 
-    filtered[key] = value
+    // Recursively filter globally hidden keys from nested objects
+    filtered[key] = filterHiddenOutputKeys(value)
   }
 
   return filtered

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

@@ -5,6 +5,39 @@ import type { ExecutionResult } from '@/executor/types'
 
 const logger = createLogger('TraceSpans')
 
+/**
+ * Keys that should be recursively filtered from output display.
+ * These are internal fields used for execution tracking that shouldn't be shown to users.
+ */
+const HIDDEN_OUTPUT_KEYS = new Set(['childTraceSpans'])
+
+/**
+ * Recursively filters hidden keys from nested objects for cleaner display.
+ * Used by both executor (for log output) and UI (for display).
+ */
+export function filterHiddenOutputKeys(value: unknown): unknown {
+  if (value === null || value === undefined) {
+    return value
+  }
+
+  if (Array.isArray(value)) {
+    return value.map((item) => filterHiddenOutputKeys(item))
+  }
+
+  if (typeof value === 'object') {
+    const filtered: Record<string, unknown> = {}
+    for (const [key, val] of Object.entries(value as Record<string, unknown>)) {
+      if (HIDDEN_OUTPUT_KEYS.has(key)) {
+        continue
+      }
+      filtered[key] = filterHiddenOutputKeys(val)
+    }
+    return filtered
+  }
+
+  return value
+}
+
 function isSyntheticWorkflowWrapper(span: TraceSpan | undefined): boolean {
   if (!span || span.type !== 'workflow') return false
   return !span.blockId
@@ -21,43 +54,34 @@ function flattenWorkflowChildren(spans: TraceSpan[]): TraceSpan[] {
       return
     }
 
-    const processedSpan = ensureNestedWorkflowsProcessed(span)
+    const processedSpan: TraceSpan = { ...span }
+
+    const directChildren = Array.isArray(span.children) ? span.children : []
+    const outputChildren =
+      span.output &&
+      typeof span.output === 'object' &&
+      Array.isArray((span.output as { childTraceSpans?: TraceSpan[] }).childTraceSpans)
+        ? ((span.output as { childTraceSpans?: TraceSpan[] }).childTraceSpans as TraceSpan[])
+        : []
+
+    const allChildren = [...directChildren, ...outputChildren]
+    if (allChildren.length > 0) {
+      processedSpan.children = flattenWorkflowChildren(allChildren)
+    }
+
+    if (outputChildren.length > 0 && processedSpan.output) {
+      const { childTraceSpans: _, ...cleanOutput } = processedSpan.output as {
+        childTraceSpans?: TraceSpan[]
+      } & Record<string, unknown>
+      processedSpan.output = cleanOutput
+    }
+
     flattened.push(processedSpan)
   })
 
   return flattened
 }
 
-function getTraceSpanKey(span: TraceSpan): string {
-  if (span.id) {
-    return span.id
-  }
-
-  const name = span.name || 'span'
-  const start = span.startTime || 'unknown-start'
-  const end = span.endTime || 'unknown-end'
-
-  return `${name}|${start}|${end}`
-}
-
-function mergeTraceSpanChildren(...childGroups: TraceSpan[][]): TraceSpan[] {
-  const merged: TraceSpan[] = []
-  const seen = new Set<string>()
-
-  childGroups.forEach((group) => {
-    group.forEach((child) => {
-      const key = getTraceSpanKey(child)
-      if (seen.has(key)) {
-        return
-      }
-      seen.add(key)
-      merged.push(child)
-    })
-  })
-
-  return merged
-}
-
 export function buildTraceSpans(result: ExecutionResult): {
   traceSpans: TraceSpan[]
   totalDuration: number
@@ -318,19 +342,24 @@ export function buildTraceSpans(result: ExecutionResult): {
       }
     }
 
-    if (
-      isWorkflowBlockType(log.blockType) &&
-      log.output?.childTraceSpans &&
-      Array.isArray(log.output.childTraceSpans)
-    ) {
-      const childTraceSpans = log.output.childTraceSpans as TraceSpan[]
-      const flattenedChildren = flattenWorkflowChildren(childTraceSpans)
-      span.children = mergeTraceSpanChildren(span.children || [], flattenedChildren)
+    if (isWorkflowBlockType(log.blockType)) {
+      const childTraceSpans = Array.isArray(log.childTraceSpans)
+        ? log.childTraceSpans
+        : Array.isArray(log.output?.childTraceSpans)
+          ? (log.output.childTraceSpans as TraceSpan[])
+          : null
 
-      const { childTraceSpans: _, ...cleanOutput } = span.output as {
-        childTraceSpans?: TraceSpan[]
-      } & Record<string, unknown>
-      span.output = cleanOutput
+      if (childTraceSpans) {
+        const flattenedChildren = flattenWorkflowChildren(childTraceSpans)
+        span.children = flattenedChildren
+
+        if (span.output && typeof span.output === 'object' && 'childTraceSpans' in span.output) {
+          const { childTraceSpans: _, ...cleanOutput } = span.output as {
+            childTraceSpans?: TraceSpan[]
+          } & Record<string, unknown>
+          span.output = cleanOutput
+        }
+      }
     }
 
     spanMap.set(spanId, span)
@@ -730,47 +759,3 @@ function groupIterationBlocks(spans: TraceSpan[]): TraceSpan[] {
 
   return result
 }
-
-function ensureNestedWorkflowsProcessed(span: TraceSpan): TraceSpan {
-  const processedSpan: TraceSpan = { ...span }
-
-  if (processedSpan.output && typeof processedSpan.output === 'object') {
-    processedSpan.output = { ...processedSpan.output }
-  }
-
-  const normalizedChildren = Array.isArray(span.children)
-    ? span.children.map((child) => ensureNestedWorkflowsProcessed(child))
-    : []
-
-  const outputChildSpans = (() => {
-    if (!processedSpan.output || typeof processedSpan.output !== 'object') {
-      return [] as TraceSpan[]
-    }
-
-    const maybeChildSpans = (processedSpan.output as { childTraceSpans?: TraceSpan[] })
-      .childTraceSpans
-    if (!Array.isArray(maybeChildSpans) || maybeChildSpans.length === 0) {
-      return [] as TraceSpan[]
-    }
-
-    return flattenWorkflowChildren(maybeChildSpans)
-  })()
-
-  const mergedChildren = mergeTraceSpanChildren(normalizedChildren, outputChildSpans)
-
-  if (
-    processedSpan.output &&
-    typeof processedSpan.output === 'object' &&
-    processedSpan.output !== null &&
-    'childTraceSpans' in processedSpan.output
-  ) {
-    const { childTraceSpans, ...cleanOutput } = processedSpan.output as {
-      childTraceSpans?: TraceSpan[]
-    } & Record<string, unknown>
-    processedSpan.output = cleanOutput
-  }
-
-  processedSpan.children = mergedChildren.length > 0 ? mergedChildren : undefined
-
-  return processedSpan
-}