T3 Code Windows Tutorial: Use your mobile phone to remotely control Codex, Claude Code and OpenCode

T3 Code defines itself as an “Agent harness control surface”: it does not provide a new base model, but controls Codex, Claude Code, Cursor, Grok Build and OpenCode that are already installed and logged on your computer.

You can view and control the Agent using a local web page, the Electron desktop client, or the mobile interface. It solves the problem of continuing to view tasks, reply to questions, and manage multiple local coding agents after leaving the computer. This also means that the upper limit of permissions of T3 Code depends on the underlying CLI. If Codex can modify the entire workspace and Claude Code can execute commands, then the remote control interface may also trigger these capabilities. The official clearly stated that the project is still in its early stages and bugs should be expected, so this article starts with local trial and then discusses remote access.

What is the difference between it and Remote Desktop and Pi Web

Remote desktop transmits the entire Windows graphical interface, while T3 Code only presents the Agent session and related controls, so it is easier to operate on the mobile phone. It is not about moving the model to the cloud. The Agent CLI, login status, repositories, and commands are still running on your Windows computer. Compared with the Web packaging of a single Agent, the goal of T3 Code is to uniformly control multiple Providers and provide Web, desktop and mobile portals.

Suitable usage:

• Check long-term test results during commuting;
• Answer Agent’s clarifying questions on your mobile phone;
• Manage several independent repository sessions at the same time;
• Control the development host from a tablet within the LAN;
• Retain your existing Codex or Claude Code subscription login. It is not suitable to open unattended computers directly to the public network, nor should it be regarded as a mature enterprise permissions platform.

Check the underlying Agent before installation

T3 Code requires at least one installed and certified Provider. Check item by item in PowerShell:

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codex --version
claude --version
cursor-agent --version
opencode --version

Only one of them needs to be available, not all of them need to be installed. Codex Login:

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codex login

Claude Code Login:

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claude auth login

Cursor CLI Login:

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cursor-agent login

OpenCode Login:

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opencode auth login

These commands may change with each project version, and the corresponding official documents shall prevail. After completing the login, first open a test repository in a normal terminal to confirm that the Agent can start and read files.

Route 1: Zero installation trial with npx

The fastest official entrance is:

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npx t3@latest

The first run will download the npm package and start the T3 Code backend and local web application. Note the local address and port displayed by the terminal, do not assume it is a certain port based on old tutorials. View all parameters:

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npx t3@latest --help

If npm asks whether to install the package, first check that the package name is indeed t3, and confirm that the source is from the official project. Keep the terminal running and access the local URL it outputs in a browser on the same computer. Do not configure public network forwarding at this time. Complete local function verification first. Press Ctrl+C on the terminal to end the test. Then confirm whether the process exited:

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Get-Process | Where-Object { $_.ProcessName -match 't3|node' }

Do not terminate all Node processes at will, because other development services may also use Node.

Route 2: Install Windows desktop version

Officially supports installation through winget:

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winget install T3Tools.T3Code

Start from the start menu after installation, or check whether the program is registered:

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winget list T3Tools.T3Code

Upgrade:

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winget upgrade T3Tools.T3Code

If enterprise policy blocks winget, you can download it from the official GitHub Releases Download the signed installation package. Do not obtain repackaged installers from third-party software download sites.

The desktop version still relies on the local Provider. It does not automatically complete the Codex or Claude Code login for you.

Connecting to the test repository for the first time

Create a new directory that does not contain sensitive code:

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$testRoot = 'C:\Work\t3code-demo'
New-Item -ItemType Directory -Path $testRoot -Force
Set-Location $testRoot
git init

After creating a few sample files, select this directory from T3 Code and start the logged-in Provider. The first task should be read-only, for example:

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列出仓库中的文件，说明每个文件用途，不要修改文件，也不要运行安装命令。

Check whether the interface is displayed correctly:

• Provider name;
• Current working directory;
• Agent output;
• Tool call or approval;
• Session stop button;
• Session status after page refresh.

After passing, let the Agent modify a test file and use Git to confirm the scope:

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git status --short
git diff

Why Windows identity and environment variables are inconsistent

When npx t3@latest is launched from PowerShell, it usually inherits the user, PATH and environment variables of the current terminal. Desktop applications may get a different environment when launched from the Start menu. The typical symptom is that codex can be run in the terminal, but T3 Code prompts that the Provider cannot be found. Check the command location first:

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Get-Command codex
Get-Command claude
$env:PATH -split ';'

Re-login to Windows or restart the desktop application to refresh the user level PATH that changed after installation. Don’t write the API Key into system-level environment variables to “solve everything”. T3 Code is designed to reuse the existing authentication of the Provider, giving priority to fixing CLI login and program visibility.

If T3 Code is run as a different Windows user, it will not automatically read the authentication file under your current account.

Local Web and LAN Access

The local listening address 127.0.0.1 can only be accessed from the current computer, which is the most secure default. To access from a mobile phone on the same Wi-Fi, you need to confirm whether T3 Code provides listening address parameters. Take a look first:

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npx t3@latest --help

Change the listening address to the LAN interface only when the official parameters clearly support it. Then look up the computer IP:

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Get-NetIPAddress -AddressFamily IPv4 |
  Where-Object { $_.IPAddress -notlike '169.254*' -and $_.IPAddress -ne '127.0.0.1' }

View the actual listening:

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Get-NetTCPConnection -State Listen |
  Sort-Object LocalPort |
  Select-Object LocalAddress,LocalPort,OwningProcess

Create Windows Firewall rules for only the actual ports and limit the remote addresses to the home or work network segment. Don’t create broad rules that allow all ports, all network profiles. Do not use naked HTTP access on public Wi-Fi because session content and control requests may be eavesdropped by devices on the same network segment.

More secure remote access methods

After leaving the LAN, preferentially use a networking VPN, such as Tailscale, WireGuard, or an existing enterprise VPN. This way T3 Code can continue to listen only to private networks. Recommended relationships are:

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手机 -> 私有 VPN -> Windows 开发机 -> T3 Code -> 本地 Agent CLI

Not recommended:

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互联网 -> 路由器端口转发 -> 未认证的 T3 Code HTTP 端口

If you must use a reverse proxy, at least require HTTPS, strong authentication, origin restrictions, WebSocket support, and short sessions. Also make sure that T3 Code’s own authentication mechanism cannot rely solely on a difficult-to-guess URL. Cloudflare Tunnel can hide the origin address, but the public Tunnel is still the public network entrance. Should be combined with Access authentication, don’t assume that just because “no router ports are open” doesn’t mean there is no risk.

What actions should be verified on the mobile phone

Do not perform real development tasks immediately after the first mobile phone connection. Test item by item:

1. Open an existing session;
2. Check whether the long output is complete;
3. Reply with plain text;
4. Reject tool approval once;
5. Stop the running Agent;
6. Switch to another repository;
7. Reconnect after locking the phone screen;
8. Disconnect the VPN and confirm that it cannot be accessed. In particular, test whether “stop” actually terminates the underlying process. Some interfaces just stop outputting, and the command may still be running in the background. Check related processes on the Windows side:

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Get-CimInstance Win32_Process |
  Where-Object { $_.Name -match 'codex|claude|node|t3' } |
  Select-Object ProcessId,Name,CommandLine

Do not confuse workspaces with multiple Provider sessions

T3 Code can control multiple Providers, which does not mean that they share the same context, permissions, or configuration. Explicitly record for each session:

• Provider;
• Absolute path to the repository;
• Current branch;
• Whether writing is allowed;
• Whether command execution is allowed;
• Task goal;
• Acceptance command. Require Agent to report before remote operation:

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只报告当前工作目录、Git 分支和未提交文件，不要修改任何内容。

If the directory or branch is incorrect, stop the session and correct it on the computer before continuing. Mobile phone screens are smaller, making it easier to ignore route prompts.

Subscriptions, API Keys and Fees

Official description T3 Code can use your existing subscriptions or certifications in Codex, Claude Code, Cursor, Grok Build and OpenCode.

The charges are still incurred by the corresponding Provider. T3 Code is just a control surface and will not turn high-value tasks into free tasks. Need to check separately:

• Whether the Provider uses subscription login or API Key;
• Whether parallel sessions increase consumption;
• Whether long-term background tasks are still running;
• Whether expensive operations are repeated during failed retries;
• Whether the task will automatically stop when the mobile phone is disconnected. Do not synchronize the Provider’s authentication directory to the public cloud disk, and do not paste the API Key into the T3 Code chat.

What does it mean that the project is still in its early stages

The official README clearly states “Expect bugs”, and there is currently no complete public documentation site. Assume for actual use:

• Upgrades may change the session format;
• Web and desktop versions may behave inconsistently;
• Some Provider integrations lag behind new CLI versions;
• Remote reconnection may lose some state;
• Background processes require manual inspection;
• The security model may still be adjusted.

Don’t base your unique development environment and unique session history on an earlier version. The real code is always saved in Git, and important task descriptions are saved in Issues or repository documents.

T3 Code faults located by symptoms

npx t3@latest download failed

Check npm Registry, agent and Node versions:

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npm config get registry
node --version
npm cache verify

Do not turn off corporate TLS checks or use untrusted mirrors without confirming the cause.

T3 Code cannot find Codex or Claude

Run Get-Command with the same Windows user, restart the desktop application, and confirm that the CLI login does not exist only in another user or WSL.

Blank after opening the browser

Check the first error when starting the terminal, browser console and port occupation. Try a browser window without extensions to exclude script blocking.

Mobile phone connection timed out

Confirm that the mobile phone and computer network are reachable, the program is not monitoring 127.0.0.1, the Windows Firewall rule range is correct, and the VPN route has been established.

Session shows running but no output

Check whether the underlying Agent is waiting for approval, the login has expired, or the command is stuck. Go back to the Windows side and view the process and startup logs.

Unexpected modifications occur in the repository

Stop the Agent immediately and save the evidence:

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git status --short
git diff --stat
git diff

Do not use destructive Git commands to directly clear the site. First confirm which files were originally modified by the user.

Security habits for daily use

• Enable disk encryption and lock screen on Windows development machine;
• Enable biometrics and remote wipe on mobile phone;
• T3 Code only listens to the local machine or private VPN;
• Do not directly open the public network port;
• Agent uses ordinary users instead of administrators;
• High-risk commands retain manual approval;
• Confirm the directory and branch for each remote task;
• Upgrade T3 Code and the underlying Provider regularly;
• Save Git state before leaving the computer;
• Revoke VPN and Provider sessions if the device is found missing.

Is it worth installing

If you often run Codex or Claude Code tasks that last for more than ten minutes, T3 Code’s mobile control entry is very attractive. The fastest way to evaluate is not to deploy on the public network immediately, but to run npx t3@latest in the test repository to experience local Web, task stopping and session recovery.

After confirming that the local area is reliable, then access the mobile phone through private VPN. Only when authentication, permissions, logs, and disconnection behavior are verified should it be allowed to take control of the real working repository.

T3 Code resources

• T3 Code official repository
• Codex official document
• Claude Code Official document