This is a much bigger deal than a lot of people realize.
For the first time, Anthropic has opened up Claude Code itself. You can now customize almost anything about it, including the UI. You can basically build your own custom harness on top of Claude Code.
Let’s break it down.
What Are Claude Mods?
Mods are small pieces of JavaScript or TypeScript code that run inside Claude Code and change two things:
How Claude Code looks
How Claude Code works
Technically, a mod is a Claude Code plugin with one extra file called the hooks module.
Claude Code calls the functions in that file whenever something happens, like a tool about to run or a prompt being sent. Because mods are plugins, you install and share them the same way.
Customizing Claude Code can make a big difference in how efficiently developers work. The real value comes from building a setup that fits your workflow, reduces repetitive tasks, and helps you get consistent results without unnecessary complexity.
Excellent breakdown! Comparing Mods to middleware makes the concept click instantly especially the execution model ($, e, next). The distinction between Mods running persistent session code inside the harness versus external MCP connectors/hooks is…
