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github-actions[bot] 5556b4cde5 fix(core): make step-argument serialization failures catchable in workflow code (#3675) (#3687)
* fix(core): make step-argument serialization failures catchable in workflow code

A step whose arguments fail to serialize is now finalized by the
suspension handler as step_created + step_failed (mirroring a step-body
failure) instead of rejecting the whole suspension. The next replay —
forced in-process, since no step message is dispatched for the failed
step — rejects the step's promise with the SerializationError, so a
try/catch around the step call observes it. Uncaught, the error
propagates out of the workflow body and fails the run as a fatal
USER_ERROR immediately, instead of redelivering the orchestrator
message until max deliveries (49/48) as reported in production on v4.

* Serialize the step_failed error with the VM global; one-sentence changeset

Addresses review feedback: dehydrateStepError in
finalizeUnserializableStep now receives suspension.globalThis like every
other dehydration in this file. Error detection is realm-independent, so
the host-created SerializationError serializes identically, but VM-realm
values guest code threw into the cause chain are now detected by the
realm-sensitive reducers.

* Address review: QuickJS engine support, deferred-batch join, drain gate, placeholder marker, telemetry, docs

- QuickJS: dumpPendingOps now catches a step input's serialization
  failure per-op, reframes it as a SerializationError with the same
  framed message as dehydrateStepArguments, and surfaces it on the
  pending op instead of failing the whole collection. The entrypoint's
  dispatchPendingOps finalizes such steps as step_created (placeholder
  input) + step_failed, excludes them from inline claims and queue
  publishes, marks them handled, and raises the requeue signal so the
  failure is observed even when the feed lags — mirroring the node:vm
  engine, so both engines agree: catchable in workflow code, USER_ERROR
  with the framed message when uncaught. Both step-argument e2e tests
  now pass on WORKFLOW_VM=quickjs.
- runtime.ts: the failed-step replay path now joins
  suspensionResult.deferredBatchWork before continuing, so a trailing
  chunk commit or step-message publish rejection propagates instead of
  being swallowed after ack; committed inline claims are documented as
  deliberately handed to owned recovery.
- Terminal drain: finalization is gated on a stepDispatch target. The
  drain caller has no replay to observe a finalization, so a completed
  run no longer gains failed-step rows for an unawaited unserializable
  step — the rethrown error is swallowed by the drain's catch,
  preserving its pre-existing behavior.
- The placeholder input now carries a marker string ('[input
  unavailable: step argument serialization failed]', shared via
  runtime/unserializable-step.ts) so inspect/o11y don't render the
  failed step as a genuine zero-argument call.
- New workflow.steps.failed_serialization span attribute on the
  suspension span, so occurrence is measurable without log search.
- Docs: v5 serialization-failed error page documents where each
  boundary's failure surfaces (catchable step failure vs run failure)
  and the no-retry USER_ERROR semantics; foundations/errors-and-retries
  gains a Serialization Failures section with the try/catch shape.

* Guard the finalization crash window; self-contained docs samples

- A crash or transient failure between finalization's two durable
  writes leaves a lone placeholder step_created, and redelivery then
  dispatches the step through normal crash recovery — previously
  running user code with the placeholder arguments. The placeholder
  now carries a structural flag on the input triple's top level (which
  user code never controls, so no false positives), and the step
  executor checks it after hydration: instead of running the body, it
  throws the intended fatal SerializationError, completing the
  interrupted finalization as step_failed. Applies to both engines
  (they share the placeholder and the executor).
- Regression tests: executor fails a placeholder-input step without
  running the body (and doesn't trip on a genuine argument equal to
  the display marker); handleSuspension rejects for redelivery when
  step_failed can't be written after step_created landed, leaving the
  recoverable placeholder behind; mixed bad-step + large fan-out
  returns the failure set alongside still-pending deferredBatchWork
  whose rejection surfaces — the contract the runtime's failed-step
  join (added previously) relies on.
- Docs: the two new code samples are now self-contained so the docs
  code-sample typecheck passes.

Signed-off-by: Nathan Rajlich <n@n8.io>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
2026-08-20 18:44:04 +00:00
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