Vercel's fx coding agent harness now works inside T3 Code

What the integration does

T3 Code is described by Vercel as an open-source control plane for coding agents. It lets users add agents such as fx as providers for their coding sessions, so the agent runs inside the T3 Code interface rather than on its own.

According to Vercel, the built-in fx provider supports Supervised and Auto modes. It also works with the models and skills users already have set up in fx. That means anyone who has configured fx does not have to rebuild that setup to use it in T3 Code.

The integration is available across three surfaces: web, desktop, and mobile. Vercel's announcement does not go into further detail on how each surface differs.

How to get started

Vercel outlines a short setup path. Users first install fx and set up their model provider. They then download T3 Code and add fx through the settings menu.

• Step 1: install fx and set up your model provider.
• Step 2: download T3 Code.
• Step 3: go to Settings > Providers > Add provider and add fx.

Both fx and T3 Code are described as open source, so developers can inspect the code of the harness and of the control plane that hosts it.

What it means for developers

The change gives developers who use fx another place to run it. Instead of working only with the agent directly, they can manage fx sessions in T3 Code, which is built to host several coding agents as providers.

The Supervised and Auto modes carry over into this setup, so users can keep the level of oversight they choose for the agent's work. Vercel credits Pranit Sharma, Esteban Suárez, and Ben Sabic as contributors to the announcement.

The source does not give details on pricing, performance, or other supported agents, so those points remain to be confirmed through the project documentation.