# Vercel Sandbox 1.9.1

- Product: Vercel Sandbox (https://whatsnew.fyi/product/vercel-sandbox)
- Vendor: Vercel
- Date: 2026-04-02
- Version: 1.9.1
- Original notes: https://github.com/vercel/sandbox/releases/tag/%40vercel/sandbox%401.9.1
- Permalink: https://whatsnew.fyi/product/vercel-sandbox/releases/1.9.1

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **changed** — Build and publish both ESM and CJS outputs for the SDK package
- **added** — Support useworkflow serialization for sandboxes and commands
- **fixed** — Fix a size mismatch when encoding binaries during write operations
- **changed** — Accept string and Uint8Array in writeFiles() content, not just Buffer

###### Patch Changes

-   Build and publish both ESM and CJS outputs for the SDK package. ([#84](https://github.com/vercel/sandbox/pull/84))

-   Support useworkflow serialization for sandboxes and commands ([#72](https://github.com/vercel/sandbox/pull/72))

-   Fix a Size mismatch when encoding binaries during write operations ([#127](https://github.com/vercel/sandbox/pull/127))

-   Accept `string` and `Uint8Array` in `writeFiles()` content, not just `Buffer`. ([#128](https://github.com/vercel/sandbox/pull/128))