# Vercel Workflow SDK adds atomic starts to prevent duplicate runs

_Published Wednesday, November 4, 2026 at 2:21 PM EST · Products · Latest · Tier 2 — Notable_

![Vercel Workflow SDK adds atomic starts to prevent duplicate runs — Primary](https://assets.vercel.com/image/upload/contentful/image/e5382hct74si/1t2DaV8IVnp7ibDYvEqXvN/3292f4d1cf23f6e6bbf4e12d1a2c9923/image__65_.png)

Vercel says Workflow SDK 5.3.1 lets developers start a workflow and reserve its identifying token in one indivisible operation, closing a documented gap that could previously create duplicate runs. A duplicate start now raises an error identifying the run that already owns the token, without creating another run.

Developers can route a duplicate request's payload to the existing run. Messages arriving before execution begins are buffered and delivered in order. An optional retention setting keeps the token unavailable after a run ends, allowing applications to reject late duplicates.

## Sources

- [Vercel News](https://vercel.com/changelog/atomic-start-hooks-in-the-workflow-sdk)

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Canonical: https://techandbusiness.org/newswire/4_zQ-jYG7BjYGOupQguZEA
Published: 2026-11-04T19:21:58.600Z
Story chronology: 2026-11-04T18:55:00.000Z
Retrieved: 2026-11-04T22:06:37.507Z
Publisher: Tech & Business (techandbusiness.org)