Claude Code Mods Announced: A Customizable Agent Architecture with TypeScript

As AI-assisted coding assistants and autonomous software agents settle at the center of modern software development, developers' demand for control over these tools grows every day. Instead of AI tools that work as standard closed boxes, people are looking for flexible platforms that can bend to the dynamics of the project and the team. Anthropic has rolled out a comprehensive architecture that answers this need for Claude Code, its AI assistant that runs in terminal and desktop environments: Claude Code Mods.

The mods system, which lets developers use TypeScript to change Claude Code's working logic from top to bottom, opens up a wide customization space that ranges from the assistant's prompt flow to security checks, and from custom interface components to replacing built-in features.

What Are Claude Code Mods and Why Were They Built?

Mods are compact TypeScript functions that directly change Claude Code's behavior. Anthropic had previously introduced the "Hooks" mechanism to give users certain automations. However, the hooks infrastructure only offered a passive structure triggered after specific actions; it could not rewrite events, change the user interface or replace built-in core functions.

Developers wanting to shape Claude Code to their own way of working without waiting for official feature updates is what gave birth to the mods architecture. Thanks to this system, matured on GitHub with community feedback, a mod can now modify prompts before they reach the model, block risky terminal commands or add new interactive control panels to the terminal interface.

Event-Driven Working Logic

Whenever Claude Code carries out any operation on the system, it fires an event in the background. Calling a tool, asking the user for confirmation or permission, or printing output to the screen are examples of these events. A mod works by hooking into exactly this event flow.

Mod functions can run before events, after them, at the moment an event happens, or as a wrapper that surrounds the event entirely:
• Prompt Manipulation: An instruction the user writes can be inspected by a mod before it is sent to the AI model, expanded according to corporate standards or filtered.
• Privacy and Sensitive Data Protection (Secret Redaction): Secret keys, API tokens or personal data that appear in the output of the terminal tools Claude runs can be redacted through mods before Claude reads them.
• Tool Management and Retries: An unsafe tool call can be blocked outright, its parameters can be corrected, or automatic retry logic can be built for error cases.
• Dynamic Permission Approvals: The permission prompt can be approved automatically for certain safe commands, while extra security steps can be brought in for operations that touch critical directories.

Building Custom Interfaces for the Terminal and Desktop

One of the most innovative aspects of the mods system is that it can intervene in visual output. Mods that run in both the terminal-based CLI version of Claude Code and the desktop app can customize the interface shown on screen.

A mod can reformat the questions Claude asks, tool outputs or summary tables. Custom interactive buttons, form inputs or side panels can be added to the interface. What's more, when a button added by one mod is pressed, another mod in the system can be triggered, making it possible to build complex and integrated workflows.

Mods written by different developers stack on top of each other in load order when they are loaded. The mod loaded first is the layer that sees the event first and evaluates the result last. This structure makes it possible for mods from independent developers to work in harmony with each other.

One of the most interesting features is that Claude Code can mod itself. When a developer tells Claude Code directly, "Write me a mod that enforces these rules," the assistant generates the required TypeScript code, loads it as a plugin and activates it instantly in the active session with hot reload.

Breaking Up Built-in Features and a Modular Core

With this update, Anthropic is also modularizing its own product architecture. The built-in features inside Claude Code are gradually being turned into standalone mods. For example, the platform's popular /diff feature now runs as a standalone mod.

If they wish, developers can turn off this built-in mod from the /plugin menu or replace it with a custom diff tool they have written themselves. In the long run, the company aims to reduce Claude Code to a minimal core engine and offer all additional capabilities as mods users can choose from.

Enterprise Security and the sec-default Shield

Mods run on the user's computer at the same privilege level as Claude Code and without sandbox isolation. That is why it is very important to prefer trusted plugins when loading mods from external sources.

To guarantee security in enterprise environments, Anthropic offers management shields specific to the Team and Enterprise plans:
• System administrators can restrict mod marketplaces through the central management console or remotely distribute allowed mods to users.
• On corporate machines and in centralized configurations, a built-in mod called sec-default (security default) is automatically loaded with the highest priority. This security layer strictly prevents the mods users install from bypassing the security and permission rules.
• Teams can build internal security mods that show CI/CD status live in a side panel of the chat, start a mandatory approval mechanism for operations that touch live production servers, and record all mod actions in an audit log.

Starting today, developers can begin trying out mods using the /plugin command in the CLI or through the Claude Directory, and package their own TypeScript mods to share with the community.