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Claude Code Mods: A Few Lines of TypeScript That Change How Your AI Agent Behaves

Plugins add features. Mods change how the agent itself behaves.

On October 1, 2026, Anthropic released Mods alongside Claude Code version 2.1.287. Where Claude Code''s existing hooks were shell scripts that reacted to events, Mods are TypeScript functions that wrap the agent''s internal operations. They can intercept a tool call''s input and output from a single handler, auto-approve permission dialogs, or silently scrub sensitive data before it ever reaches the model.

Five Things Mods Can Do

1. Rewrite Prompts Before They Reach the Model

Modify a user''s request before it is sent. For example, automatically inject "always use TypeScript" into every prompt, or normalize vague language into more precise instructions.

2. Block, Retry, or Rewrite Tool Calls

When Claude Code is about to run a command (such as rm -rf), a mod can detect it and block execution, rewrite it to a safer alternative, or trigger a retry with a different approach.

3. Auto-Approve or Auto-Deny Permission Requests

Permission dialogs that previously required manual confirmation can be handled automatically by a mod. Set rules like "always approve read requests inside this directory" and the dialog disappears.

4. Redact Secrets From Tool Output

Before tool results are returned to the model, a mod can strip out API keys, passwords, and personal data. This prevents sensitive information from accumulating in the model''s context window.

5. Customize the UI

Edit or replace interface elements, add new display panels, or restyle existing views to match a team''s workflow.

The Built-In /diff Feature Is Now a Mod

One of the notable structural changes is that Anthropic has converted existing built-in features into mods. The /diff command β€” which showed uncommitted changes in a panel beside the conversation β€” now ships as a mod. That means users can disable it, fork it, or replace it with a custom version. Anthropic said more built-in features will be modded over time.

How to Install Mods

Mods ride inside plugins and are installed via the /plugin command. Both the CLI and the desktop app support them.

The fastest way to start: ask Claude Code itself to write a mod. Describe the behavior you want in natural language and Claude Code will generate the TypeScript mod file for you.

Security Warning

Anthropic was explicit in its launch announcement: Mods are not sandboxed. A mod runs with the same access to your machine as Claude Code itself. Installing a mod from an untrusted source carries real risk. Always review mod code before installing β€” especially in team environments where mods will be shared.

EdTech Use Cases

Mods give institutions practical tools to configure safe, consistent Claude Code environments for learners.

Restrict dangerous commands: A mod deployed to all students can block commands that delete files or access system directories, creating a safer learning sandbox.

Enforce coding conventions: A prompt-rewriting mod that automatically applies a course''s style guide means every student works with an AI assistant that already knows the rules.

Protect sensitive data: A redaction mod that strips API keys or personal information from tool output can be applied at the organization level before students ever see a result.

The Takeaway: From Using Claude Code to Shaping It

Mods shift Claude Code from something you use to something you sculpt β€” tailored to your team, your workflow, and your risk tolerance. Developers who know TypeScript can start immediately. Those who don''t can simply describe the behavior they want and let Claude Code write the mod.

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Claude Code Mods: A Few Lines of TypeScript That Change How Your AI Agent Behaves | MINSSAM.COM