@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
In Claude Code:
claude mcp add reachpad -e REACHPAD_IDENTITY_CREDENTIAL=… -- npx -y @reachpad/mcp
Two transports, one implementation
npx @reachpad/mcp
REACHPAD_MCP_HTTP_PORT=8722 npx @reachpad/mcp
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.
| variable | meaning |
|---|
REACHPAD_ENDPOINT | your reachpad host. Plaintext http:// to anything but loopback is refused before a socket opens. |
REACHPAD_IDENTITY_CREDENTIAL | your per-user credential. It names one account and can act for no other — the server takes the identity from the credential's own record, never from the request. |
REACHPAD_API_KEY | optional, per-workspace scoped and revocable. When set, run_command uses it and needs no identity exchange. |
REACHPAD_MCP_HTTP_PORT | serve HTTP instead of stdio. |
REACHPAD_MCP_HTTP_HOST | default 127.0.0.1. This process bridges to a control plane with your credentials, so binding it to the world is a decision made on purpose, behind a proxy that terminates TLS. |
REACHPAD_MCP_HTTP_TOKEN | bearer token, compared in constant time. Absent, one is generated for the run and printed on stderr — the endpoint is never unauthenticated by omission. |
REACHPAD_MCP_HTTP_NO_AUTH | 1 serves with no authentication at all: every caller that can reach the port is authorized. An affirmative choice, not a default. |
REACHPAD_MCP_ALLOWED_ORIGINS | comma-separated. A request carrying an unlisted Origin is refused — a browser cannot forge it, which closes DNS rebinding. No Origin at all is a non-browser client and is allowed. |
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.
| tool | what it does |
|---|
get_credit_balance() | remaining compute credits. One credit runs one standard workspace for one minute. |
create_workspace(repo?, ref?, name?) | a new workspace, optionally with a repository cloned into $HOME/work. Reachpad generates its display name when omitted. |
list_workspaces() | your workspaces and how many forks each has |
get_workspace(workspace) | what it boots from: its head snapshot, its log position and its fork tree |
run_command(workspace, argv, cwd?, env?, timeout_ms?) | one command, its exit code and its output. A paused workspace resumes to serve it. |
checkpoint_workspace(workspace, name?) | fork from the last sealed snapshot; the original is untouched |
expose_port(workspace, port, check?) | open a port to the web and get the link that reaches it. Idempotent per port. |
list_ports(workspace) | the ports this workspace has open, oldest first, with their links |
revoke_port(workspace, port) | close one port. Re-opening it later mints a different link. |
delete_workspace(workspace) | archive it and free the plan slot. Nothing is deleted — snapshots and history survive. |
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.