feat(custom-blocks): log and bill child runs in the publisher's workspace

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

@@ -2,6 +2,7 @@ import type React from 'react'
 import { AgentSkillsIcon, WorkflowIcon } from '@/components/icons'
 import { formatCreditCost } from '@/lib/billing/credits/conversion'
 import { perceivedBrightness } from '@/lib/colors'
+import { hasUnhandledError } from '@/lib/logs/execution/trace-spans/trace-spans'
 import type { TraceSpan } from '@/lib/logs/types'
 import { LoopTool } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/subflows/loop/loop-config'
 import { ParallelTool } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/subflows/parallel/parallel-config'
@@ -43,10 +44,7 @@ export function hasErrorInTree(span: TraceSpan): boolean {
 }
 
 export function hasUnhandledErrorInTree(span: TraceSpan): boolean {
-  if (span.status === 'error' && !span.errorHandled) return true
-  if (span.children?.length) return span.children.some(hasUnhandledErrorInTree)
-  if (span.toolCalls?.length && !span.errorHandled) return span.toolCalls.some((tc) => tc.error)
-  return false
+  return hasUnhandledError(span, { includeToolCalls: true })
 }
 
 export function getBlockIconAndColor(

apps/sim/app/workspace/[workspaceId]/logs/utils.ts

@@ -85,6 +85,7 @@ const TRIGGER_VARIANT_MAP: Record<string, React.ComponentProps<typeof Badge>['va
   copilot: 'pink',
   mothership: 'pink',
   workflow: 'blue-secondary',
+  custom_block: 'blue-secondary',
 }
 
 interface StatusBadgeProps {

apps/sim/blocks/custom/build-config.test.ts

@@ -94,9 +94,18 @@ describe('buildCustomBlockConfig', () => {
     expect(findSub(config, 'docs')?.multiple).toBe(true)
   })
 
-  it('exposes the full result and hides plumbing when no outputs are curated', () => {
+  it('advertises no data fields — and no whole-result fallback — without curation', () => {
     const config = buildCustomBlockConfig(row, fields, { icon })
-    expect(Object.keys(config.outputs).sort()).toEqual(['error', 'result', 'success'])
+    // Curation is required at publish, so an uncurated row exposes only the
+    // system fields. `result` must not come back: it would advertise the child's
+    // raw terminal state (agent toolCalls/thinking, nested workflow ids).
+    expect(Object.keys(config.outputs).sort()).toEqual([
+      'error',
+      'errorRef',
+      'errorType',
+      'success',
+    ])
+    expect(config.outputs.result).toBeUndefined()
     expect(config.outputs.childWorkflowId).toBeUndefined()
     expect(config.outputs.childTraceSpans).toBeUndefined()
   })

apps/sim/blocks/custom/build-config.ts

@@ -63,13 +63,14 @@ export const RESERVED_PARAMS = new Set([
 ])
 
 /**
- * Output names the block projects itself (`success`/`error` from `buildOutputs`,
- * `cost` from the executor's billing aggregation). A user-named exposed output
- * must never shadow these — an output literally named `cost` would clobber the
- * billed cost. `result` is deliberately NOT reserved: it only exists as a system
+ * Output names the block projects itself: `success`/`error`/`errorType`/`errorRef`
+ * from `buildOutputs`, plus `cost` (kept reserved for forward compatibility now
+ * that the child bills its own run). A user-named exposed output must never
+ * shadow these. `result` is deliberately NOT reserved: it only exists as a system
  * field when no outputs are curated, which cannot co-occur with a named output.
+ * Compared lowercased, so every entry here must be lowercase.
  */
-export const RESERVED_OUTPUT_NAMES = new Set(['success', 'error', 'cost'])
+export const RESERVED_OUTPUT_NAMES = new Set(['success', 'error', 'cost', 'errortype', 'errorref'])
 
 /** Whether an exposed-output name collides with a system output field. */
 export function isReservedOutputName(name: string): boolean {
@@ -208,13 +209,15 @@ function buildOutputs(exposed: CustomBlockOutput[] | undefined): BlockConfig['ou
   const outputs: BlockConfig['outputs'] = {
     success: { type: 'boolean', description: 'Execution success status' },
     error: { type: 'string', description: 'Error message' },
+    errorType: { type: 'string', description: 'Machine-readable failure class' },
+    errorRef: { type: 'string', description: 'Opaque reference to the failed run' },
   }
-  if (exposed && exposed.length > 0) {
-    for (const out of exposed) {
-      outputs[out.name] = { type: 'json', description: `Output: ${out.path}` }
-    }
-  } else {
-    outputs.result = { type: 'json', description: 'Workflow execution result' }
+  // No whole-`result` fallback: curation is required at publish, so every
+  // consumer-visible field is one the publisher chose. A legacy row with no
+  // curated outputs advertises no data fields and fails loudly at invocation
+  // rather than silently reverting to exposing the child's raw terminal state.
+  for (const out of exposed ?? []) {
+    outputs[out.name] = { type: 'json', description: `Output: ${out.path}` }
   }
   return outputs
 }

apps/sim/executor/errors/boundary.ts

@@ -0,0 +1,54 @@
+/**
+ * Machine-readable class of a custom-block failure. Every member describes a
+ * fact the CONSUMER already knows or can act on — never the source workflow's
+ * blocks, tools, or upstream provider responses.
+ */
+export type CustomBlockErrorType =
+  | 'missing_inputs'
+  | 'not_deployed'
+  | 'unavailable'
+  | 'depth_limit'
+  /**
+   * The payer had no usage headroom, so the child never ran. Safe to surface:
+   * a custom block always resolves within the consumer's own organization, so
+   * the exhausted limit is their org's, not a foreign publisher's.
+   */
+  | 'usage_limit'
+  /** The child run was cancelled (the invoking run aborted or was cancelled). */
+  | 'cancelled'
+  | 'execution_failed'
+
+/** What a failed custom block tells its consumer. Leaks nothing about the source run. */
+export interface CustomBlockFailure {
+  /** Stable, machine-readable class of the failure. */
+  errorType: CustomBlockErrorType
+  /** Opaque handle to the child run, so the publisher can find the exact failing execution. */
+  ref?: string
+  /** Consumer-safe sentence. Generic unless the throw site was a {@link BoundarySafeError}. */
+  message: string
+}
+
+/**
+ * An error whose `message` names only the CALLER's own artifacts — the block
+ * they placed, its input labels, its deployment state — so it may cross an
+ * invocation boundary verbatim.
+ *
+ * Every error that is NOT of this class is opaque at the boundary. The default
+ * is fail-closed, so a `throw new Error(...)` added later anywhere in the
+ * custom-block path is redacted without anyone remembering to redact it. This
+ * replaces the older convention of throwing *before* the `try` block to dodge
+ * the catch's sanitizer, where redaction depended on lexical position.
+ */
+export class BoundarySafeError extends Error {
+  readonly errorType: CustomBlockErrorType
+
+  constructor(options: { message: string; errorType: CustomBlockErrorType }) {
+    super(options.message)
+    this.name = 'BoundarySafeError'
+    this.errorType = options.errorType
+  }
+}
+
+export function isBoundarySafeError(error: unknown): error is BoundarySafeError {
+  return error instanceof BoundarySafeError
+}

apps/sim/executor/errors/child-workflow-error.ts

@@ -1,4 +1,5 @@
 import type { TraceSpan } from '@/lib/logs/types'
+import type { CustomBlockFailure } from '@/executor/errors/boundary'
 import type { ExecutionResult } from '@/executor/types'
 
 interface ChildWorkflowErrorOptions {
@@ -8,6 +9,12 @@ interface ChildWorkflowErrorOptions {
   executionResult?: ExecutionResult
   childWorkflowSnapshotId?: string
   childWorkflowInstanceId?: string
+  /** Child workflow names from this invocation down to the failing run, outermost first. */
+  workflowChain?: string[]
+  /** The deepest non-workflow failure, already block-name-prefixed (`"Function 1: boom"`). */
+  rootErrorMessage?: string
+  /** Consumer-safe failure descriptor. Set only at a custom-block invocation boundary. */
+  consumerFacing?: CustomBlockFailure
   cause?: Error
 }
 
@@ -21,6 +28,15 @@ export class ChildWorkflowError extends Error {
   readonly childWorkflowSnapshotId?: string
   /** Per-invocation unique ID used to correlate child block events with this workflow block. */
   readonly childWorkflowInstanceId?: string
+  /**
+   * The chain of child workflow names from this invocation down to the failing
+   * run. Carried structurally so nesting never has to be recovered by parsing
+   * the formatted message.
+   */
+  readonly workflowChain: string[]
+  /** The deepest non-workflow failure, without any workflow-chain prefixes. */
+  readonly rootErrorMessage: string
+  readonly consumerFacing?: CustomBlockFailure
 
   constructor(options: ChildWorkflowErrorOptions) {
     super(options.message, { cause: options.cause })
@@ -30,9 +46,24 @@ export class ChildWorkflowError extends Error {
     this.executionResult = options.executionResult
     this.childWorkflowSnapshotId = options.childWorkflowSnapshotId
     this.childWorkflowInstanceId = options.childWorkflowInstanceId
+    this.workflowChain = options.workflowChain ?? [options.childWorkflowName]
+    this.rootErrorMessage = options.rootErrorMessage ?? options.message
+    this.consumerFacing = options.consumerFacing
   }
 
   static isChildWorkflowError(error: unknown): error is ChildWorkflowError {
     return error instanceof ChildWorkflowError
   }
 }
+
+/**
+ * Renders a nested child-workflow failure for display. Kept byte-identical to
+ * the format this error used to carry as a raw string, so persisted logs and
+ * the UI are unaffected by the move to structured fields.
+ */
+export function formatWorkflowChainMessage(chain: string[], rootError: string): string {
+  if (chain.length > 1) {
+    return `Workflow chain: ${chain.join(' → ')} | ${rootError}`
+  }
+  return `"${chain[0]}" failed: ${rootError}`
+}

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

@@ -21,6 +21,7 @@ import {
   DEFAULTS,
   EDGE,
   isSentinelBlockType,
+  isWorkflowBlockType,
 } from '@/executor/constants'
 import type { DAGNode } from '@/executor/dag/builder'
 import { ChildWorkflowError } from '@/executor/errors/child-workflow-error'
@@ -450,10 +451,25 @@ export class BlockExecutor {
       errorOutput.content = partialContent
     }
 
+    // Only real workflow blocks surface a child workflow name. A custom block's
+    // source workflow is never named to its consumer — and before the handler
+    // resolves the real name this field still holds the source workflow id, so
+    // an early throw (e.g. the call-chain depth limit) would leak it outright.
     if (ChildWorkflowError.isChildWorkflowError(error)) {
-      errorOutput.childWorkflowName = error.childWorkflowName
-      if (error.childWorkflowSnapshotId) {
-        errorOutput.childWorkflowSnapshotId = error.childWorkflowSnapshotId
+      if (isWorkflowBlockType(block.metadata?.id)) {
+        errorOutput.childWorkflowName = error.childWorkflowName
+        if (error.childWorkflowSnapshotId) {
+          errorOutput.childWorkflowSnapshotId = error.childWorkflowSnapshotId
+        }
+      }
+      // A custom block's consumer gets a machine-readable failure class and an
+      // opaque handle to the failed run — enough to branch on and to quote in a
+      // support request, without naming anything inside the source workflow.
+      if (error.consumerFacing) {
+        errorOutput.errorType = error.consumerFacing.errorType
+        if (error.consumerFacing.ref) {
+          errorOutput.errorRef = error.consumerFacing.ref
+        }
       }
     }
 

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

@@ -945,6 +945,7 @@ export class AgentBlockHandler implements BlockHandler {
       workflowId: ctx.workflowId,
       workspaceId: ctx.workspaceId,
       userId: ctx.userId,
+      executionId: ctx.executionId,
       stream: streaming,
       messages: messages?.map(({ executionId, ...msg }) => msg),
       environmentVariables: normalizeStringRecord(ctx.environmentVariables),
@@ -1028,6 +1029,10 @@ export class AgentBlockHandler implements BlockHandler {
         isDeployedContext: ctx.isDeployedContext,
         callChain: ctx.callChain,
         billingAttribution: ctx.metadata.billingAttribution,
+        // Reaches tool `_context` via `prepareToolExecution`, so a tool that starts
+        // its own child execution (a custom block) correlates and cancels against
+        // this real run instead of minting a phantom id.
+        executionId: ctx.executionId,
         reasoningEffort: providerRequest.reasoningEffort,
         verbosity: providerRequest.verbosity,
         thinkingLevel: providerRequest.thinkingLevel,

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

@@ -3,6 +3,7 @@ import { toError } from '@sim/utils/errors'
 import { getBlock } from '@/blocks/index'
 import { isMcpTool } from '@/executor/constants'
 import type { BlockHandler, ExecutionContext } from '@/executor/types'
+import { readStatusCode } from '@/executor/utils/errors'
 import type { SerializedBlock } from '@/serializer/types'
 import { executeTool } from '@/tools'
 import { getTool } from '@/tools/utils'
@@ -93,6 +94,10 @@ export class GenericBlockHandler implements BlockHandler {
           blockName: block.metadata?.name || 'Unnamed Block',
           output: result.output || {},
           timestamp: new Date().toISOString(),
+          // `executeTool` flattens a thrown error into a result, so Sim's own
+          // status (hosted-key 429/503) would be lost here. Carry it onto the
+          // error so `getExecutionErrorStatus` can still reach the API caller.
+          ...(typeof result.statusCode === 'number' ? { statusCode: result.statusCode } : {}),
         })
 
         throw error
@@ -107,8 +112,9 @@ export class GenericBlockHandler implements BlockHandler {
           errorMessage += `: ${block.metadata.name}`
         }
 
-        if (error.status) {
-          errorMessage += ` (Status: ${error.status})`
+        const statusCode = readStatusCode(error)
+        if (statusCode !== undefined) {
+          errorMessage += ` (Status: ${statusCode})`
         }
 
         error.message = errorMessage

apps/sim/executor/handlers/workflow/custom-block-tool-runner.test.ts

@@ -88,7 +88,7 @@ describe('runCustomBlockTool', () => {
     expect(res.error).toContain('not deployed')
   })
 
-  it('rolls up already-incurred child cost when the run fails', async () => {
+  it('reports no cost on failure — the child session billed its own run', async () => {
     const err: any = new Error('child blew up')
     err.name = 'ChildWorkflowError'
     err.childTraceSpans = [{ id: 's1', name: 'child', type: 'agent', cost: { total: 0.25 } }]
@@ -98,8 +98,7 @@ describe('runCustomBlockTool', () => {
     const res = await runCustomBlockTool({ blockType: 'custom_block_abc', _context: {} })
 
     expect(res.success).toBe(false)
-    // Partial spend must not be recorded as zero-cost.
-    expect((res.output as any).cost.total).toBeGreaterThan(0)
+    expect(res.output).toEqual({})
   })
 
   it('rejects a missing block type without invoking the handler', async () => {
@@ -108,3 +107,41 @@ describe('runCustomBlockTool', () => {
     expect(mockExecute).not.toHaveBeenCalled()
   })
 })
+
+describe('buildCustomBlockExecutionContext invoker identity', () => {
+  it("adopts the invoking run's ids so correlation names a real execution", () => {
+    const ctx = buildCustomBlockExecutionContext({
+      workspaceId: 'ws-1',
+      executionId: 'agent-execution-id',
+      requestId: 'agent-request-id',
+    })
+
+    expect(ctx.executionId).toBe('agent-execution-id')
+    expect(ctx.metadata.executionId).toBe('agent-execution-id')
+    expect(ctx.metadata.requestId).toBe('agent-request-id')
+  })
+
+  it('falls back to generated ids when the caller supplies none', () => {
+    const ctx = buildCustomBlockExecutionContext({ workspaceId: 'ws-1' })
+
+    expect(ctx.executionId).toBeTruthy()
+    expect(ctx.metadata.requestId).toBeTruthy()
+    expect(ctx.executionId).not.toBe(ctx.metadata.requestId)
+  })
+})
+
+describe('buildCustomBlockExecutionContext cancellation', () => {
+  it("adopts the agent tool loop's abort signal so the bridge has something to watch", () => {
+    const controller = new AbortController()
+    const ctx = buildCustomBlockExecutionContext(
+      { workspaceId: 'ws-1' },
+      { abortSignal: controller.signal }
+    )
+
+    expect(ctx.abortSignal).toBe(controller.signal)
+  })
+
+  it('leaves the signal undefined when the caller has none', () => {
+    expect(buildCustomBlockExecutionContext({ workspaceId: 'ws-1' }).abortSignal).toBeUndefined()
+  })
+})