Vercel Sandbox adds stdin support for running commands

Details

Vercel Sandbox now supports sending input to running commands through standard input (stdin).
Use case includes exchanging messages with stdio MCP servers such as agent-browser or sending data to command-line programs while they run.
In the TypeScript SDK, set stdin: true and detached: true in runCommand(), then use writeStdin() to send input and closeStdin() to finish.
The TypeScript SDK also accepts a Node.js readable stream (e.g., process.stdin) for stdin, automatically closing the command's stdin when the stream ends.
In the Python SDK, set stdin=subprocess.PIPE and send input with server.stdin.send(), then call communicate() to close stdin, collect output, and wait for exit.
Python's run_process() allows passing input directly for commands that receive all input at once.

Key point