feat(custom-blocks): log and bill child runs in the publisher's workspace by TheodoreSpeaks · Pull Request #6023 · simstudioai/sim

TheodoreSpeaks · 2026-07-28T22:25:07Z

Summary

A custom block's child run is now its own execution: own executionId, own logging session against the source (publisher's) workspace, own ledger rows. The publisher sees a full run with the trace waterfall in their own Logs; the consumer's view stays as opaque as before.
Billing follows the invocation boundary. The consumer no longer absorbs the child's model spend — they pay only their own base execution fee, and the child adds no second fee.
Fixes a privacy leak: SSE callbacks were forwarded into the source run, streaming the publisher's block names, inputs, outputs, workflow name, and raw agent tokens to the consumer's browser. Invisible in the UI because the terminal drops them for custom_block_*, so it went unnoticed.
Fixes failed custom blocks billing $0 — buildCostCarrierSpans wrote to blockLog.childTraceSpans, but its only reader is gated on isWorkflowBlockType, which excludes custom blocks. Dissolves now that the child bills itself; both roll-ups deleted.
Fixes the depth-limit throw leaking the source workflow's UUID into the consumer's output (childWorkflowName still holds the workflow id before it's resolved).
Errors: adds BoundarySafeError so consumer visibility is a property decided at the throw site (fail-closed) instead of depending on whether a throw sits before or after the try. Consumers now get a machine-readable errorType plus an opaque errorRef (the child's execution id) they can quote in support.
Deletes the regex round-trip (parseNestedWorkflowError / buildNestedWorkflowErrorMessage) in favour of a structured workflowChain. That also fixes Workflow chain: Child → Child | err, which happened whenever a child returned success: false rather than throwing.
Fixes 429/503 surfacing to API callers as 500 — readStatusCode now walks .cause and reads HttpError/status/statusCode, with a narrow 503-only 5xx whitelist so an upstream 502/504 never becomes ours. buildBlockExecutionError now preserves cause. Deletes dead buildHTTPError.
Unifies four copies of the "did this run fail?" span walk into hasUnhandledError / traceSpansIndicateFailure.

Behaviour changes worth flagging

Runs where a mothership block recovered from a failed child span were previously logged failed by logger.ts / logging-session.ts, which recursed past the error boundary that trace-spans.ts honours. They now log as succeeded. Existing rows are not backfilled, so expect a step-change in dashboard failure rates.
Rate-limited / hosted-key-exhausted runs now return 429/503 instead of 500. Anything retrying on status === 500 should be checked.
A custom block inside an N-iteration loop writes N log rows into the publisher's workspace.

Type of Change

New feature (also fixes several bugs found along the way)

Testing

Tested manually end-to-end across two workspaces in the same org: child run lands in the publisher's workspace with the full trace, consumer's row shows only its own 0.005 base fee and no model cost, and the child resolves credentials against the source workspace (verified via BYOK — a publisher key correctly zeroes the charge, and removing it bills the source workspace).

Full suite green: type-check 0 errors, lint:check, and all 11 CI audits (check:boundaries, check:api-validation:strict, check:utils, check:zustand-v5, check:react-query, check:client-boundary, check:bare-icons, check:icon-paths, check:realtime-prune, skills:check, agent-stream-docs:check). 15107/15108 tests pass — the one failure is a pre-existing local-env issue (cloud-review-tools shells out to a rg binary that isn't installed).

Checklist

Code follows project style guidelines
Self-reviewed my changes
Tests added/updated and passing
No new warnings introduced
I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

…pace

vercel · 2026-07-28T22:25:13Z

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cursor · 2026-07-28T22:25:16Z

PR Summary

High Risk
Touches billing attribution, cross-workspace execution/logging, and privacy redaction at the custom-block boundary; behavior changes include log success/failure classification and 429/503 API responses instead of 500.

Overview
Custom block invocations now run the publisher workflow as a separate execution: fresh executionId, custom_block logging session in the source workspace (zero base fee on the child), usage admitted against the source payer, correlation back to the consumer run, parent cancellation bridged to the child, and bounded waitForChildRuns at the end of the invoking run so abandoned children are less likely to stick in running.

Billing and visibility shift across the boundary: model spend is no longer rolled onto the consumer block or failed tool results; the consumer sees only curated outputs plus success / error / errorType / errorRef. Publishing and updates require at least one exposed output—the whole-child result fallback is removed so raw agent/workflow internals cannot leak. Consumer failures use BoundarySafeError and redacted ChildWorkflowError (consumerFacing); regular workflow blocks still get child names and trace spans. SSE callbacks are not forwarded into custom-block children (fixes a publisher-data stream leak).

Agent-as-tool paths adopt the invoker’s executionId and abort signal. HTTP mapping for workflow API errors now walks .cause, forwards Sim-owned 4xx/503 via HttpError/statusCode on tool responses, and avoids treating upstream status as the API status. Failure detection is centralized in hasUnhandledError / traceSpansIndicateFailure (including mothership recovery semantics). Nested workflow errors use structured workflowChain instead of message parsing.

^{Reviewed by Cursor Bugbot for commit b345750. Bugbot is set up for automated code reviews on this repo. Configure here.}

greptile-apps · 2026-07-28T22:28:48Z

Greptile Summary

Custom-block child runs are isolated as their own executions billed and logged in the publisher workspace, with boundary-safe consumer errors and no SSE leak of source internals.

Child runs open a LoggingSession on the source workflow/workspace with a fresh executionId, zero base charge, and correlation back to the invoker.
Boundary failures are classified via BoundarySafeError / buildBoundaryFailure (unavailable, usage_limit, depth_limit, etc.) and surface errorType/errorRef to consumers without source details.
Agent-tool custom blocks adopt the invoking run’s executionId and abort signal; status codes propagate for 429/503; curated outputs only (no whole-result fallback).

Confidence Score: 5/5

Safe to merge; both previously reported boundary-classification issues are fixed at HEAD and no remaining blockers were identified in this follow-up scope.

Unavailable custom blocks now go through buildBoundaryFailure with errorType unavailable, and admission denials use CustomBlockAdmissionError/usage_limit so consumers can branch; no blocking failure remains in the scored set.

Important Files Changed

Filename	Overview
apps/sim/executor/handlers/workflow/workflow-handler.ts	Routes unavailable and other boundary failures through buildBoundaryFailure; child session/billing isolated to publisher workspace.
apps/sim/lib/workflows/custom-blocks/child-execution.ts	Admission denials are BoundarySafeError with usage_limit; personal-quota messages sanitized to a generic consumer-safe string.
apps/sim/executor/execution/block-executor.ts	Maps consumerFacing errorType/errorRef onto block error output; suppresses childWorkflowName for non-workflow custom blocks.

Sequence Diagram

sequenceDiagram
  participant Consumer as Consumer workflow
  participant WH as WorkflowBlockHandler
  participant Admit as admitCustomBlockChildExecution
  participant Child as Child Executor
  participant Log as LoggingSession (source WS)

  Consumer->>WH: execute custom_block
  WH->>WH: getCustomBlockAuthority
  alt unavailable / no curated outputs
    WH-->>Consumer: ChildWorkflowError consumerFacing.unavailable
  else admitted path
    WH->>Admit: source payer limits
    alt usage exceeded
      Admit-->>WH: CustomBlockAdmissionError usage_limit
      WH-->>Consumer: consumerFacing.usage_limit
    else ok
      WH->>Log: safeStart (source workspace)
      WH->>Child: execute (own executionId)
      Child-->>Log: complete / error
      WH-->>Consumer: curated outputs or opaque failure + errorType/errorRef
    end
  end

_{Reviews (11): Last reviewed commit: "fix(custom-blocks): track the whole chil..." | Re-trigger Greptile}

…or consumers

TheodoreSpeaks · 2026-07-28T22:49:16Z

@greptile

TheodoreSpeaks · 2026-07-28T22:49:17Z

@cursor review

…eric failure

TheodoreSpeaks · 2026-07-28T22:58:31Z

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@cursor review

…opagate

TheodoreSpeaks · 2026-07-28T23:17:28Z

@greptile

TheodoreSpeaks · 2026-07-28T23:17:29Z

@cursor review

TheodoreSpeaks · 2026-07-28T23:28:21Z

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TheodoreSpeaks · 2026-07-28T23:28:22Z

@cursor review

TheodoreSpeaks · 2026-07-28T23:39:37Z

@greptile

… consumers

TheodoreSpeaks · 2026-07-28T23:49:44Z

@greptile

TheodoreSpeaks · 2026-07-28T23:49:45Z

@cursor review

…ecution

TheodoreSpeaks · 2026-07-29T00:15:21Z

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TheodoreSpeaks · 2026-07-29T00:15:22Z

@cursor review

…to agent tools

TheodoreSpeaks · 2026-07-29T00:42:28Z

@greptile

TheodoreSpeaks · 2026-07-29T00:42:29Z

@cursor review

TheodoreSpeaks · 2026-07-29T01:04:57Z

@greptile

TheodoreSpeaks · 2026-07-29T01:04:58Z

@cursor review

cursor · 2026-07-29T01:11:46Z

-        // source workflow would bill if run directly, exactly as if it ran the key.
-        const childCost = aggregateChildCost(childTraceSpans)
-        return this.projectCustomBlockOutput(executionResult, exposedOutputs, childCost)
+        return this.projectCustomBlockOutput(executionResult, exposedOutputs)


Paused child treated as success

Medium Severity

Cancelled custom-block children are classified with a BoundarySafeError after the child session is finalized, but paused children (status: 'paused', success: true) are not. They go through safeComplete, then projectCustomBlockOutput, so a source HITL pause becomes a consumer success with incomplete outputs and a completed publisher log. CustomBlockErrorType has no paused member either.

Additional Locations (2)

apps/sim/executor/handlers/workflow/workflow-handler.ts#L734-L746

apps/sim/executor/errors/boundary.ts#L5-L19

^{Reviewed by Cursor Bugbot for commit 67805cb. Configure here.}

…ancelled

…hole result

cursor

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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^{Reviewed by Cursor Bugbot for commit 264bc74. Configure here.}

TheodoreSpeaks · 2026-07-30T17:26:51Z

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

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TheodoreSpeaks added 2 commits July 28, 2026 19:41

fix(executor): stop adopting an upstream target's HTTP status as our own

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

fix(custom-blocks): track the whole child run, not just its finalization

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TheodoreSpeaks commented Jul 28, 2026

Summary

Behaviour changes worth flagging

Type of Change

Testing

Checklist

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PR Summary

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Greptile Summary

Confidence Score: 5/5

Important Files Changed

Sequence Diagram

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Paused child treated as success

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