boxes.dev vs T3 Code

At a glance

As of September 2026.

Who runs the computer

T3 Code runs agents on a computer you provide, and boxes.dev runs the computers for you.

The T3 Code server runs on your laptop or on a host you set up, such as a cloud VM, and holds your repositories, agent logins, terminals, and history. You install and sign in to each agent's CLI on that host, and you keep the host secure, updated, and reachable. The desktop, web, and mobile apps connect to it through T3 Connect, a private network or Tailscale, or SSH from the desktop app. T3 Code itself is free, and you pay for the host and for each agent's plan.

boxes.dev first sets up your full development environment on a cloud machine called the Template box, with the tools, databases, services, and data your app needs, so an agent can run the app and test its changes end to end. A setup agent can port the environment from your laptop, including the files, local data, agent settings, and skills you choose to upload, or build it from a GitHub repository. boxes.dev then saves the Template box as a snapshot, and every task runs on its own devbox, a full, isolated copy of that machine. A maintenance script can keep the Template box current as your code changes, running on a schedule or when files such as a lockfile change, and each successful run saves a new snapshot. Team Templates let an admin prepare one starting environment for everyone on the team.

You'd never let an engineer ship code they hadn't run, and a full environment holds the agent to the same standard. On a boxes.dev devbox, the agent runs your whole app, with its databases and services, and tests its changes in the browser as it builds. It reproduces bugs in the real app to find the root cause instead of guessing from the code, so it writes better code and makes fewer mistakes. It can also take screenshots and record video for you to review, so you can hand it most repetitive manual testing.

Worktrees on one host, or a machine for each task

T3 Code separates parallel threads with Git worktrees, and boxes.dev gives each task its own machine.

In T3 Code, a thread started with New worktree gets its own branch and working directory, and project scripts can install dependencies when the worktree is created. The worktrees share the host's CPU, memory, services, databases, and ports, so threads that each need their own database or a dev server on the same port need more setup, such as containers or another host. With several hosts connected, T3 Code can choose one for each new thread based on available CPU and memory.

Each boxes.dev devbox is a separate machine with its own copy of your databases and services, so every task can run the whole app on its usual ports. A devbox can also hold several threads, which share its files and running services.

Reaching the running app

On boxes.dev, you and the agent can both use the app running on a devbox, and T3 Code's desktop app has a preview browser that agents can drive.

In T3 Code's preview browser, you can pick page elements and attach annotations to a message, and a project script can open a URL in the browser when the script runs.

Each boxes.dev devbox runs a browser that you and the agent share, so you can watch the agent test the app, click through it yourself, or comment on page elements to show the agent what to change. Ports forwards the app to the same localhost port on your laptop and gives each devbox stable .localhost addresses. A public link shares a devbox's running app with anyone, and a Project URL gives your project one stable public address that you can point at any devbox, which suits OAuth callbacks and webhooks.

When you close your laptop

Both keep working after you close your laptop when the work runs in the cloud, and boxes.dev also sleeps machines that nobody is using.

On a Linux host, T3 Code's background service starts at boot and keeps running after you log out, so agents keep working after you disconnect. A Mac host needs to stay logged in and awake. A cloud VM used as a host runs, and bills, until you stop it.

A boxes.dev devbox stays awake while its agent works and sleeps when nobody is using it. Sleep keeps the machine's files and memory, like closing a laptop's lid, so dev servers, databases, and terminal sessions resume where they left off, and a sleeping devbox doesn't use box-hours. The devbox stays yours until you delete it.

What comes with every boxes.dev devbox

The boxes.dev desktop app opens the same set of tools for whichever devbox you select:

• Terminal, with tabs that keep running after you close the app.
• Files, a file browser and editor with search across the workspace.
• Git/Review, for branch history and diffs, where comments on changed lines go to the agent together as one message.
• Browser, the browser on the devbox that you and the agent share.
• Ports, for the forwarding, .localhost addresses, and public links described above.
• Activity, which shows the processes using the machine's CPU and memory.

Mentioning @boxes.dev in a Slack thread starts Codex or Claude Code on a new devbox, and later mentions from you or teammates you allow send follow-ups to the same conversation, which run with your access. Work can also start from an assigned Linear issue, a schedule, or an API call. Agents can start other agents on new or existing devboxes, message each other, read earlier threads, and leave notes in a shared /project folder. You can share a thread's link with your team, let teammates read threads, and link commits to the threads that made them. The iOS and Android apps can reply to agents, browse files, and open a shell on a devbox.

Where T3 Code shines

• Free and open source. T3 Code is MIT-licensed, so you can read, change, and fork the whole app.
• Six agents in one app. Codex, Claude Code, Cursor, Grok Build, OpenCode, and Antigravity work side by side, and you can add separate accounts for the same agent.
• Load balancing across hosts. With several machines connected, T3 Code can choose one for each new thread based on available CPU and memory.
• Mobile simulators beside a thread. On a host that supports them, an iOS Simulator or Android Emulator opens next to the conversation, and agents can use it to check their work.

Pricing

As of September 2026.

A box-hour is one default devbox awake for an hour, and sleeping devboxes don't use any. On Starter, 40 box-hours works out to about two hours of devbox time each working day, and Pro's 250 to about twelve, spread across as many as ten devboxes at once. Your Claude or ChatGPT plan covers the agents' usage. See Plans, seats, and box-hours.

T3 Code's terms say it has no subscription fee, that you pay your agent providers, cloud infrastructure, and network operators, and that any paid feature will show its price before you buy it. See T3 Code's terms.

Using both

T3 Code and boxes.dev can work on the same repositories, with the same Claude and ChatGPT logins. You can keep T3 Code on the hosts you already run, and use boxes.dev when the agent should test its work in its own copy of your full running app, or when work should start from Slack or Linear.

Frequently asked questions

Is T3 Code free and open source?

Yes. T3 Code is MIT-licensed and has no subscription fee. You pay for your agents' plans and for any host you run it on.

How does T3 Code on a cloud VM compare with boxes.dev?

A well-prepared VM running T3 Code gives you agents that keep working after you disconnect and that you can reach from desktop, web, and phone. You still provision, secure, update, and pay for the VM, and parallel threads share it. boxes.dev gives each task a full, isolated copy of your Template box, sleeps idle machines while keeping their memory, and adds a browser you share with the agent, Slack, Linear, schedules, and public URLs.

Can I use my Claude and ChatGPT plans with both?

Yes. T3 Code runs Claude Code and Codex with the logins on your host, and boxes.dev runs them with your Claude or ChatGPT plan or an API key.

Sources

• T3 Code: install and providers, remote access, background service, threads and worktrees, project file, settings, source control, devices, browser profiles, composer, downloads, license, and terms.
• boxes.dev: How boxes.dev works, Update your Template box and snapshots, Startup, teardown, and maintenance, Sleep, wake, and recover a devbox, Review a page with your agent, Browse, edit, and transfer files, Preview your app, Project URLs, Commit, push, and open a pull request, Create and publish a Team Template, Connect Codex and Claude, Install and use the CLI, Work from Slack, Create an automation, Shared project storage, Organize and share threads, Use boxes.dev on your phone, and Plans, seats, and box-hours.