Send Information While a Computer Program Is Running

Some computer programs need information while they are already doing their work. Vercel Sandbox now offers a way to send that information. The feature uses standard input, which is also called stdin. It lets information enter a program while that program runs. Developers can use it to exchange messages with other tools.

One example is an MCP server such as agent-browser. MCP connects computer tools so they can work together. The new feature lets a program send messages to these tools. It can also send information to other programs while they run. The main change is support for this exchange during ongoing work.

Vercel provides ways to use the feature in TypeScript and Python. In TypeScript, developers turn on input when they start the program. They can then send information and close the input when finished. The tools can also take information that arrives over time. When that information stops arriving, the input closes as well.

Python developers can also start a program with input turned on. They then send the information it needs while it is running. Another step closes the input and collects any remaining response. That step also waits for the program to finish its work. Sending information and collecting the response are both part of this process.

Not every program needs information to arrive at different times. Some programs receive everything they need in one single step. For those cases, Python offers a way to pass it all together. Developers can choose the method that matches how the program receives information. Vercel's update supports both ongoing exchanges and this simpler kind of input.