Remote Coding Runtime

A model-neutral, client-neutral remote coding runtime with one stable Cloudflare control plane and outbound-only local Runners.

ChatGPT / Claude / Cursor / any MCP client
          │ HTTPS stateless MCP
          ▼
Cloudflare Worker
  Admin UI · RegistryDO · RunnerDO
          │ authenticated outbound WebSocket RPC
          ▼
Local Runner
  filesystem · transactional patch · Git · process · persistent jobs

Cloudflare does not execute code or call an AI model. The MCP client performs reasoning; the Runner performs filesystem, Git, and process work. Closing the browser, chat, MCP request, or Runner WebSocket does not stop a job that has already been started.

Architecture

• Worker: the only public MCP/control-plane endpoint. It authenticates MCP client URLs, serves the small admin UI, and routes bounded RPC messages.

• RegistryDO: SQLite metadata for Runners, workspaces, historical jobs, administrator password/session state, and MCP client credentials.

• RunnerDO: one hibernatable Durable Object per Runner. It owns the current outbound Runner WebSocket and correlated RPC bridge; it never executes coding work.

• Runner: an outbound-only Node process with trusted workspace mappings, path confinement, patch/Git services, local subprocesses, and persistent logs/job metadata.

• Protocol: packages/protocol provides strict TypeScript schemas and a generated language-neutral JSON Schema for future Go/Rust Runners.

The Cloudflare core uses only Workers plus SQLite-backed Durable Objects. It does not use OAuth, KV, D1, Queues, R2, Sandbox, Containers, Dynamic Workers, tunnels, inbound SSH, GitHub Actions runtime, or AI model APIs.

Related MCP server: cloud-to-local

Deploy

Requirements: Node.js 20+, npm, Git, Wrangler, and a Cloudflare account with SQLite-backed Durable Objects enabled.

git clone https://github.com/aloneio/remote-coding-runtime.git
cd remote-coding-runtime
npm install
npm test
npm run typecheck
npm run build
npm run validate:worker

Configure the three production secrets used by Runner administration and the internal control channel:

cd apps/worker
npx wrangler secret put ADMIN_TOKEN
npx wrangler secret put RUNNER_TOKEN_PEPPER
npx wrangler secret put INTERNAL_CONTROL_SECRET

Then deploy only when ready:

npx wrangler deploy --config wrangler.jsonc

npm run validate:worker runs Wrangler with --dry-run. Verify its output contains --dry-run: exiting now; it does not prove a deployed account's quotas or production network behavior.

First setup

Open the deployed root URL, for example:

https://mcp.aloneio.com/

A fresh RegistryDO displays:

Welcome to Remote Coding Runtime
Create administrator password

The first valid setup request wins atomically. No bootstrap password is required. Set the password immediately after deployment. If an uninitialized public instance is claimed by somebody else, delete/reset its Cloudflare state and redeploy.

Passwords are not stored in plaintext. The Registry stores a versioned PBKDF2-HMAC-SHA-256 verifier with a random salt. Login creates a random seven-day opaque session; the browser receives a Secure, HttpOnly, SameSite=Strict, Path=/ cookie, while RegistryDO stores only its SHA-256 hash. Password changes revoke every existing session.

Admin state-changing requests use a session-bound CSRF token and same-origin checks. Setup and login also use short-lived pre-auth CSRF cookies.

Add a Runner

Runner authentication remains independent from admin login and MCP client credentials. Enroll or rotate a Runner through the ADMIN_TOKEN-protected API:

curl -sS -X POST https://mcp.aloneio.com/admin/runners \
  -H "Authorization: Bearer $ADMIN_TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{"runner_id":"home-pc"}'

The plaintext Runner token is returned only by successful enrollment/rotation. Store it securely, then start the Runner:

CODING_RUNNER_TOKEN='returned-runner-token' \
  npx tsx apps/runner/src/cli.ts start \
  --server wss://mcp.aloneio.com \
  --runner-id home-pc \
  --workspace zero=/home/me/code/zero\;writable\;noshell

Workspace syntax:

--workspace id=path[;readonly|writable][;shell|noshell]

Defaults are readonly;noshell. Production requires wss://; cleartext ws:// is accepted only for loopback together with --insecure-local.

The Runner needs only outbound Internet access. It does not expose HTTP, MCP, OAuth, SSH, or inbound ports.

Create MCP clients

Log in at /, then use the /admin dashboard:

1. Enter a name such as ChatGPT Web, Claude, or Cursor Desktop.

2. Select Read, Write, and/or Execute scopes.

3. Press Create.

4. Copy the generated URL immediately. It is shown once.

Example:

https://mcp.aloneio.com/fJ3...43-character-base64url-secret...x92/mcp

Configure only that URL in the MCP client. No OAuth flow, callback, or extra Bearer header is required. Each client must have its own URL:

ChatGPT → secret A
Claude  → secret B
Cursor  → secret C

The dashboard supports:

• Create

• Rename

• Rotate

• Revoke

• Per-client coding:read, coding:write, coding:exec scopes

• Created/last-used/status/key-prefix display

Rotation invalidates the old URL immediately and displays the replacement once. Revocation makes the URL return the same 404 Not Found used for unknown secrets.

Secret URL security model

/<secret>/mcp is an API credential. Treat the full URL like a password:

• do not publish it;

• do not include it in screenshots;

• do not commit it to Git;

• do not paste it into logs, issues, or analytics;

• create a different URL for every MCP client/device;

• rotate immediately if leakage is suspected.

The application never logs the incoming URL/path and stores only a SHA-256 verifier plus a short display prefix. MCP/admin responses use Cache-Control: no-store; HTML also uses Referrer-Policy: no-referrer, a restrictive CSP, nosniff, and frame blocking. Infrastructure outside the application may still record request paths, so configure Cloudflare log redaction and rely on rotation/revocation for recovery.

Tool catalog

Runtime

runner_list
runner_info
workspace_list
env_info

Filesystem

fs_read
fs_list
fs_search
fs_apply_patch

Execution and persistent jobs

exec_start
exec_run
job_list
job_get
job_logs
job_cancel
job_input

Git

git_status
git_diff

coding:read permits runtime/filesystem reads, job_list/job_get/logs, and Git inspection. coding:write permits patching. coding:exec permits process start/run/cancel/input. A job is shared within the single-admin instance rather than owned by one MCP client: Claude can discover and read a job created earlier by ChatGPT if it has the required scope.

Persistent jobs

exec_start returns a job_id promptly. The Runner persists local authoritative state under:

~/.remote-coding-runner/state/
├── runner.json
└── jobs/<job_id>/
    ├── meta.json
    ├── stdout.log
    └── stderr.log

The Worker stores bounded metadata only. job_list reads RegistryDO snapshots and therefore works while a Runner is offline. Full stdout/stderr remains on the Runner and is read through paginated job_logs once the Runner is online.

Runner sync upserts current/recent jobs without deleting older history simply because it was omitted from a bounded snapshot. Registry retains active/nonterminal jobs and up to 1,000 terminal jobs per Runner. A job may record created_by_client_id for audit, but that field does not restrict cross-client access.

After a Runner restart, a process that still matches its saved PID/fingerprint becomes unknown. Lazy reconciliation during job_get, job_list, and sync keeps it unknown while alive and changes it to interrupted after disappearance because the real exit outcome is unavailable. A recovered cancellation becomes cancelled only when durable evidence proves that this Runner delivered the termination request; no exit code is invented.

On-disk log files remain complete and unbounded by default. Monitor Runner disk use.

Filesystem and patch safety

MCP requests provide only runner_id, workspace_id, and workspace-relative paths. The Runner rejects:

• POSIX absolute paths;

• Windows drive, UNC, and device paths;

• NUL bytes and .. traversal;

• unknown workspace IDs;

• symlink/junction ancestry and escapes;

• write-through symlinks;

• writes to readonly workspaces.

fs_read and job_logs use UTF-8-safe byte cursors. Tiny pages containing Chinese, emoji, and accented characters can be concatenated exactly without replacement characters.

fs_apply_patch supports Add/Update/Delete/Move operations, expected SHA-256 baselines, exact hunk matching, same-directory staging/backups, rollback, BOM/newline/mode preservation, and bounded structured results. Stable safe errors such as invalid_patch, missing_file, target_exists, baseline_changed, hunk errors, patch_install_failed, and patch_rollback_failed reach MCP without exposing host absolute paths.

This is a workspace/path authorization boundary, not a hostile operating-system sandbox. Run untrusted repositories or commands inside an external VM/container with restricted mounts, secrets, and network access.

Timeouts and environment discovery

Shared protocol constants keep the deadlines aligned:

normal Runner operation maximum: 8,000 ms
Worker → Runner bridge timeout: 12,000 ms

This leaves a four-second transport/reply margin. exec_run and Git use the shared local limit; longer work must use exec_start.

env_info caches bounded parallel probes for platform, architecture, hostname, shell, Node, npm, pnpm, Python, Git, Go, rustc, Cargo, and Docker. Missing or timed-out tools return { "available": false } instead of failing the request.

Tests

npm test
npm run typecheck
npm run build
npm run validate:worker

The suite includes protocol tests, Runner filesystem/process/patch/Git/recovery tests, Worker Durable Object and admin/client-auth tests, and a real local Wrangler + real Runner E2E. Coverage includes:

• atomic one-time setup;

• PBKDF2 password/session behavior, expiry, logout, password invalidation, and CSRF;

• per-client secret URL create/rotate/revoke/404/scope enforcement;

• real MCP → Worker → Runner fs_read;

• UTF-8 file/log pagination;

• persistent execution after an MCP request closes;

• Runner transport disconnect, local continuation, reconnect, and sync;

• Client A starting a job and Client B discovering it with job_list while offline;

• traversal, symlink, readonly, patch, Git, timeout, output, and concurrency boundaries.

Local tests do not prove the quotas of a particular Cloudflare account, production edge-log redaction, Internet client compatibility, or a deployed restart/hibernation event. Deployment remains an operator-owned acceptance step.

Scope deliberately excluded

The MVP does not include MCP Tasks, PTY/web terminal, multi-user accounts, organizations, teams, billing, AI agents, RAG, browser automation, GitHub Actions runtime, Cloudflare Sandbox, or Cloudflare Containers.

Acknowledgements and license

This is an independent Apache-2.0 implementation. Design research considered:

• xyTom/coding-tools-mcp, Apache-2.0 + NOTICE;

• volter-ai/volter-tunnel, Apache-2.0 + NOTICE;

• Hiroshimeow/agent-mcp-gateway, MIT;

• Cloudflare Workers, Durable Objects, WebSocket Hibernation, Agents MCP handler, and MCP TypeScript SDK documentation.

The requested davidlosasgonzalez/codeagent-mcp repository was unavailable at the public URL during research, so no code or license from it was used.