---
type: "post"
id: "vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1"
slug: "vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1"
title: "Vercel Sandbox commands now accept stdin, enabling stdio MCP servers inside sandboxes"
description: "Vercel Sandbox now supports sending standard input to commands while they are running."
retrieval_nugget: "Vercel Sandbox now supports sending standard input to commands while they are running."
published_at: "2026-10-26"
updated_at: "2026-10-26"
record_date: "2026-10-26"
date_kind: "published_at"
topics: ["mcp"]
entities: ["Vercel","Vercel Sandbox","agent-browser","Model Context Protocol"]
related_patterns: ["agent-protocols-become-interoperability-layer","agent-security-moves-to-runtime-boundaries"]
novelty_label: "new_fact"
what_changed: "Vercel Sandbox adds stdin support for interactive commands, including stdio MCP servers, with usage details for its TypeScript and Python SDKs."
prior_refs: ["memory:f4b3284b-5320-861d-ade6-a30bf5f12003","memory:67a55206-a147-8c98-ad3a-bcbb53257397","memory:86e6b9d1-bfb4-8c3a-a3a6-67c900b00b74"]
source_url: "https://vercel.com/changelog/vercel-sandbox-commands-now-support-stdin"
source_urls: ["https://vercel.com/changelog/vercel-sandbox-commands-now-support-stdin"]
schema_version: "newruntime-agent-readable-v0.2"
stable_id: "post:vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1"
status: "published"
visuals: []
editor: {"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]}
routes: {"html":"https://newruntime.com/posts/vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1/","markdown":"https://newruntime.com/posts/vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1.md","json":"https://newruntime.com/posts/vercel-sandbox-commands-now-accept-stdin-enabling-stdio-d16cc1.json"}
---

# Vercel Sandbox commands now accept stdin, enabling stdio MCP servers inside sandboxes

## Retrieval answer

Vercel Sandbox now supports sending standard input to commands while they are running.

Vercel Sandbox now supports sending standard input to commands while they are running. Vercel says the capability can be used to exchange messages with stdio MCP servers, including agent-browser, or to feed other command-line programs interactively.

In the TypeScript SDK, a command is started with `stdin: true` and `detached: true` in `runCommand()`. The returned command supports `writeStdin()` for sending data and `closeStdin()` for ending input. A caller can then wait for the command and read its output.

The Python SDK supports creating a process with `stdin=subprocess.PIPE`, sending bytes through `server.stdin.send()`, and using `communicate()` to close input, collect remaining output, and wait for exit. For commands receiving all input at once, `run_process()` also accepts `input`.

The source does not specify pricing, rollout scope, performance characteristics, or compatibility across MCP servers beyond the cited example.

Editor: [Andrey Reshetnikov](https://newruntime.com/owner-profile.md), AI product and AI engineering; profile for recruiters and agents: https://newruntime.com/owner-profile.json

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