Claude Code, one of the most widely used AI coding tools, gained a built-in plugin system called Mods in version 2.1.287, released on 1 October. Coverage from The Decoder on 3 October describes Mods as JavaScript or TypeScript functions that hook into what the tool does: tool calls, prompts, even what appears on screen. Anthropic says some of its own features, such as the /diff command, are already built this way.
What is actually new
Until now, developers could extend Claude Code through hooks and external connectors that ran outside the tool. Mods run inside it. They can add panels, intercept actions before they happen, and add new commands. They work in the command line and desktop app, and partly in the VS Code extension. The first official example, “You Should Know”, runs a second agent that watches the first and flags things the developer may have missed.
The part buyers should notice
Mods run with the developer’s own permissions and are not sandboxed. Anthropic’s own advice is to install them only from trusted sources. Organisations can control which Mods are allowed to load, but only if someone has set that up.
That puts a familiar problem in a new place. A plugin on a developer’s laptop can see what the developer sees: your code, your credentials, your test data. The risk is not that Mods are bad. It is that AI tooling is now an ecosystem of third-party add-ons, with the same supply-chain questions as any other software.
What to ask a supplier
- Do you have an approved list of AI tool plugins, or can any engineer install anything?
- Do engineers working on our project use machines that hold our credentials and data?
- Who reviews what the agents produce before it ships?
So what
Customisable AI tooling is good news for teams that use it well. It lets a disciplined studio build review steps and guardrails into the way agents work. It is bad news for teams that treat “we use Claude Code” as a complete answer. The tool matters less than the process around it. See how we run AI-assisted development with experienced engineers accountable for every change, or start a project and ask us how we govern our tooling.