Your coding agent should see what your app is doing.

Add the skill

pnpm dlx skills add vercel-labs/dev3000 --skill d3k

Then ask your coding agent:

Use d3k to run this project and help me debug it.

Your agent starts the dev server and a project browser, keeps them running across edits, and reads the evidence it needs. Sign-in state stays in the browser profile.

Start with your harness

Prefer to start from your terminal? Install the CLI, then run your local app with a coding harness. d3k starts the server and browser before handing the terminal to the harness with d3k skill guidance.

pnpm add --global dev3000
d3k portless setup
d3k start --harness codex

Choose fx, codex, or claude with --harness. Use an interactive terminal with the harness installed and signed in. Exiting the harness closes the session.

Remote code, local Chrome

Run your Vercel project in a sandbox while Chrome uses your laptop’s CPU and GPU. No local project checkout is needed. A stable HTTPS URL and an authenticated browser bridge connect them.

vercel login
d3k --project my-team/my-project --harness fx
# Browser: https://my-project.d3k.localhost

Sandbox mode is experimental and requires macOS, Vercel CLI, Sandbox access, Bun, Node.js 24+, Chrome, and local Portless setup. The harness runs locally by default, with code and app environment in the sandbox. Use --harness-location sandbox to run the harness remotely. New sandboxes clone public repositories. Use --attach my-dev for an existing sandbox containing a private checkout. Chrome is confined to its dedicated profile and system files. fx connects automatically to your team’s AI Gateway with a project-scoped, expiring session key and a $5 spending limit. Use projects you trust with that access.

Use your desktop assistant

Connect ChatGPT or Claude Desktop through local MCP. Your assistant edits and tests code in the sandbox, controls local Chrome, and can create PRs. No terminal harness or Gateway key is needed.

d3k mcp --print-config

Add the generated local server configuration to your desktop client, then ask it to open your project. See the desktop setup instructions.

Exit and pick it back up

Exiting the harness or pressing Ctrl-C closes Chrome and prints your resume command. Resume restores the checkout, hostname, browser profile, and harness choice with a fresh browser connection.

d3k --resume              # List saved sandbox sessions
d3k --resume <id>         # Reconnect a session
d3k --resume <id> --harness codex

Saved entries contain session metadata, not past terminal output. Resume requires the sandbox to still exist and does not restore the harness conversation. See the README for command overrides and lifecycle details.