Vercel Sandbox commands now support stdin

Vercel added standard input (stdin) support to commands in Vercel Sandbox, letting developers send input to running commands, including exchanging messages with stdio MCP servers such as agent-browser. In the TypeScript SDK, developers set `stdin: true` and `detached: true` in `runCommand()`, then use `writeStdin()` to send input and `closeStdin()` when finished, or pass a Node.js readable stream like `process.stdin`. In the Python SDK, developers set `stdin=subprocess.PIPE`, send input with `server.stdin.send()`, and call `communicate()` to close stdin, collect remaining output and wait for the process to exit.

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.