Reachpad MCP Server

@reachpad/mcp

reachpad lets Claude, Codex and other coding agents build full-stack apps in persistent workspaces and share them by link, without a separate deployment. A workspace is a cloud development computer an agent operates itself: a repo, a filesystem, installed dependencies and build state that all survive between calls, not an ephemeral sandbox that forgets. Processes are the exception; see below.

This is the MCP server. It lets Claude, ChatGPT, Cursor, OpenCode or your own agent create a workspace, run commands in it, fork it, and come back to it later, without a developer keeping a laptop open for them.

• It persists. Pause it and the disk is sealed; the next call boots from that seal with the files, installs and git state intact, rather than rebuilding. Processes are the exception: a start is always a cold boot.
• It forks. Twenty attempts from one prepared state cost a delta each, not twenty rebuilds — because the workspace is a snapshot chain, not a machine.
• It can keep secrets out of the workspace. A brokered credential is called at the boundary on your behalf and its value never enters the workspace, the log or the store. A credential written into the workspace instead is readable there, by design.
• It is agent-agnostic. The REST API is canonical; this server, the SDK and the CLI are translations of it. Bring your own agent.

The API is the product boundary, not a web UI: reachpad.dev.

Install

npx -y @reachpad/mcp          # stdio, for a local client

In Claude Code:

claude mcp add reachpad -e REACHPAD_IDENTITY_CREDENTIAL=… -- npx -y @reachpad/mcp

Two transports, one implementation

npx @reachpad/mcp                                  # stdio
REACHPAD_MCP_HTTP_PORT=8722 npx @reachpad/mcp      # streamable http

stdio is what a local client talks to; Streamable HTTP is what a remote connector talks to. Same tools, same behaviour — added rather than forked, because two implementations of one surface is how they drift.

The HTTP side answers 405 to GET: every tool here is request/response, and the spec permits declining the server-initiated stream rather than holding a connection open for traffic that never comes. There are no sessions — nothing is held across calls that a restart could not rebuild. And it carries no credential of its own: whatever authorizes the HTTP request is what authorizes reachpad.

It is authenticated by default. Set REACHPAD_MCP_HTTP_TOKEN and that is the bearer token; set nothing and one is generated for the run and printed on stderr, because a port that bridges to your account with run_command behind it should not be open to every other process on the machine:

reachpad mcp: streamable http on http://127.0.0.1:8722
reachpad mcp: no REACHPAD_MCP_HTTP_TOKEN was set, so this one was generated for this run:

    Authorization: Bearer 3Qk…

reachpad mcp: it changes every restart. Set REACHPAD_MCP_HTTP_TOKEN to pin it, or
reachpad mcp: REACHPAD_MCP_HTTP_NO_AUTH=1 to serve with no authentication at all.

Serving with no authentication is still available and is now something you say out loud: REACHPAD_MCP_HTTP_NO_AUTH=1.

Configure

If several credentials are set, the narrowest wins, and a refused credential is never retried under a broader one — falling back would be privilege escalation nobody chose to perform.

Tools

Renamed in 0.4.0. Six tools used to be spelled *_environment and took an environment argument, while the CLI, the manual and the dashboard all said workspace. There was only ever one object; now there is only one word for it. The old names and the old argument still work and are not advertised, so nothing that already calls them breaks — but write new calls against the workspace spelling.

Not here, deliberately: starting an agent inside the workspace. It is in reachpad's roadmap and not in the fleet yet — a tool that always fails costs a model a turn and teaches it to distrust the rest, so this server advertises nothing it cannot serve.

What a port link is, and is not

Worth reading before you hand one to somebody, because none of it is discoverable from the URL:

• Anyone signed in to Reachpad who has the link can open it. It is not a private URL and not a secure one. Treat it like a preview deployment.
• The link is an address, not a copy. Restart the app on the same port and the same link serves the new version.
• A running process does not survive a pause. The workspace cold-boots with its files intact and nothing running, so after a pause the link answers with an error until something is listening on that port again. A visitor's request wakes a paused workspace; it does not restart anything inside it.
• expose_port dials the port afterwards and tells you if nothing answered, because a link to a port nothing is serving looks exactly like a link that works. Pass check: false to skip it — the dial resumes a paused workspace.
• With only REACHPAD_API_KEY, the key must be --role owner. A collaborator key is refused: listing hands back live tokens, and a token is a capability.

The rules it is built to

These are the ways a naive client of a streaming exec API misleads a model, and what this one does instead.

• An unterminated stream is UNKNOWN, never success. If the response ends without a terminal event, the tool says so in those words. It is not a zero exit, and an agent must not retry a non-idempotent command on the strength of it.
• Its deadline is looser than the server's, so a server-side answer always wins the race. A client that gives up first turns "your build finished" into "unknown", and the numbers are mirrored from the server rather than guessed.
• Refusals carry remedies, not codes. At your plan limit you get the limit, your current count, and what to do — the numbers come from the server, because a limit hardcoded in a client is a lie the moment your plan changes.
• Results are handles, not payloads. Output is tailed with the dropped byte count named. Build logs can be megabytes, and an MCP result that size destroys the caller's context window.
• A refusal is a result, not a transport error, so the model can read it and act. Only an unknown tool is a protocol error.

Test

node --test 'test/*.test.mjs'

No network and no credentials. The protocol suite spawns the shipped server as a child process and speaks real JSON-RPC over its stdio against a stub control plane on a real socket, so nothing under test is an internal import. One test runs the same arc against a real reachpad and skips when no endpoint is configured.

Repository

This repository is the source. It is deliberately separate from the reachpad backend: this code is public, it is published to npm, and its release workflow holds publishing rights — none of which belong in the same repository as the control plane. Nothing here can read the backend's source, and no job in the backend copies files out to here.

Two server constants are mirrored in src/client.js — the exec grace period and the default exec timeout. A mirrored constant normally rots; this one does not, because the backend's own CI fetches this published package and fails if they disagree. The check lives where the number would change.