# Vercel Sandbox commands now support stdin

> Source: <https://vercel.com/changelog/vercel-sandbox-commands-now-support-stdin>
> Published: 2026-10-26 06:00:00+00:00

[Vercel Sandbox](https://vercel.com/sandbox) now lets you send input to running commands through standard input (stdin). Use it to exchange messages with stdio MCP servers such as [agent-browser](https://github.com/vercel-labs/agent-browser#mcp-server), or send data to other command-line programs while they run.

In the TypeScript SDK, set `stdin: true` and `detached: true` in `runCommand()`. Use `writeStdin()` to send input and `closeStdin()` when you’re done:

You can also set `stdin` to a Node.js readable stream, such as `process.stdin`. The SDK forwards the stream’s data and closes the command’s standard input when the stream ends.

In the Python SDK, set `stdin=subprocess.PIPE` and send input with `server.stdin.send()`. Call `communicate()` to close stdin, collect remaining output, and wait for the process to exit:

For commands that receive all their input at once, you can pass `input` directly to Python’s `run_process()`.

Read the [Sandbox documentation](https://vercel.com/docs/sandbox/sdk-reference#writestdin) to get started.