offprompt MCP server

offprompt

offprompt lets a coding agent ask you for a secret and have it land where the project needs it, without the value passing through the model.

Agents need API keys. Paste one into the chat and it goes into the model's context, the transcript on disk and the provider's logs, and stays there. offprompt gives the agent another way to ask: a tool call that opens a page in your browser, from which the value goes straight into the file. The transcript only ever sees the key's name.

How it works

the file they go in, then waits inside the call.

1. The agent asks. It calls collect_secret with every key it needs, why it needs them, and

which file it writes to. Each field checks its value as you type, paste or import it, and links to where the key is made.

1. A page opens on 127.0.0.1 in your browser. It says which agent is asking, what for, and

four-emoji fingerprint, the same four your page shows. From then on the agent reads the values from the environment by name.

1. The file is written. offprompt answers the agent with the key names, the file and a

When the agent runs in a cloud sandbox, it gives you a link to the page instead. The page reaches you through a Cloudflare tunnel, and your browser encrypts the values first, to a key only the sandbox holds.

The page itself can be tried at offprompt.dev/playground.

Install

In a project's folder:

npx offprompt init

That puts the server in the project as tools/offprompt/mcp.mjs, one file that runs on node alone, and declares it in the project config of each agent found on your machine. Commit those files together with tools/offprompt/, and everyone on the project gets offprompt, as does every cloud sandbox that clones it.

To have offprompt in every project you open instead, install it for yourself:

npx offprompt init -g

npx offprompt list        # every agent, whether it was found, and how offprompt reaches it
npx offprompt remove      # out of this project
npx offprompt remove -g   # out of every agent that has it

offprompt runs on Node 22 or later. Installation covers choosing agents with --agent, and updating.

Agents

offprompt is an MCP server, so any agent that speaks MCP can use it. init sets these up:

Claude Code asks once before it starts a server a project declares. Codex and Pi read a project's config only in a project you trust. Agents has each one in detail.

Documentation

docs.offprompt.dev has the rest: what the agent can ask for, the page, every provider offprompt knows and the checks on its keys, the tools, cloud sandboxes and troubleshooting. offprompt.dev shows offprompt at work.

Security

Shortened. The full README is on GitHub.