CORRUPTED_EVENT_LOG on @workflow/core 4.6.1 with Promise.race([Promise.all(multiple hooks), sleep()])

[coreycoto]

Summary

A production Vercel Workflow using @workflow/core@4.6.1 repeatedly fails during recovery replay with CORRUPTED_EVENT_LOG when an ordered batch of multiple hooks is raced against sleep():

const hooks = children.map(() => createHook<Result>());

const outcome = await Promise.race([
  Promise.all(hooks.map(async (hook) => await hook)),
  sleep("35m"),
]);

The run made normal forward progress for approximately 41 minutes before a recovery replay diverged. The runtime attempted three recovery replays and then marked the run failed after the fourth divergence.

This looks related to #2171, but appears to reproduce on @workflow/core@4.6.1 with the multi-hook Promise.all(...) variant.

Actual behavior

The terminal workflow error was:

CORRUPTED_EVENT_LOG
Workflow replay diverged 4 times after 3 recovery replays.
Last divergence: Replay could not consume event:
eventType=hook_created,
correlationId=<hook-id>,
eventId=<event-id>.

The workflow's application/domain ledger remained in its last running state because the provider failed before finalization.

Expected behavior

Recovery replay should consume the committed hook and wait events in deterministic event-log order and continue from the last durable checkpoint.

Environment

• Vercel Workflows, production
• Region: iad1
• workflow: 4.6.1
• @workflow/core: 4.6.1
• @workflow/world-vercel: 4.5.1
• @workflow/next: 4.1.1
• Next.js: 16.2.4
• Workflow spec version shown in the trace: 3
• Batch concurrency: 8

Additional context

The original application used a sliding worker pool. We first removed that source of nondeterminism and changed it to fixed, ledger-ordered batches: hooks are now created sequentially in child order, each queue step is awaited, and the batch does not advance until the current batch settles.

The remaining orchestration primitive is effectively:

for (const batch of orderedBatches(children, 8)) {
  const hooks = [];

  for (const child of batch) {
    const hook = createHook<Result>();
    hooks.push({ child, hook });
    await queueChildStep(child, hook.token);
  }

  await Promise.race([
    Promise.all(hooks.map(({ hook }) => hook)),
    sleep("35m"),
  ]);
}

The failure happened after many batches had completed successfully, during a provider recovery replay. The divergent event was hook_created, not an application step failure, queue delivery error, or hook payload validation error.

PR #2171 describes a hook-versus-sleep replay race caused by delivery/microtask ordering. Since this run used @workflow/core@4.6.1, I suspect either:

1. the multiple-hook Promise.all shape exposes an uncovered variant, or
2. there is a regression in the later runtime.

I can provide the private Vercel workflow run ID, deployment ID, exact event ID, correlation ID, and full trace directly to a maintainer through a non-public channel.

[VaguelySerious]

Hi @coreycoto, thanks for reporting. A fix for this will be released in 4.7.0 (releasing in the coming days), and is already included in 5.0.0-beta.36 (which will release as 5.0.0 in the coming weeks)