Anthropic released Claude Code Mods, allowing developers to use TypeScript to rewrite prompts, intercept tool calls, customize the terminal interface, and even directly replace built-in functionality.
This mechanism is embedded directly in the existing Plugin system and works across both the command line and desktop client.
It works like an event interceptor: events are emitted across the entire chain, from the model initiating a request, to tool execution, to permission approval.
A Mod written by a developer can execute before an event, after an event, or directly replace the original logic; multiple Mods can also stack like middleware according to load order.
More interesting is the adjustment at the product architecture level: the official team directly refactored the built-in diff feature into a Mod, so if users don't like it, they can turn it off or replace it with their own version. Anthropic explicitly stated that in the future it will strip out more built-in features and reduce the client itself to an extremely small core.
This transformation approach is actually highly consistent with the direction DeepSeek took previously with DeepSeek Harness.
Everyone has found that as business scenarios become more complex, the black-box shell that the official team hardcodes for users simply cannot withstand the customization demands of production environments. Enterprises need data masking, approvals, and interception of high-risk commands; developers need personalized interfaces and workflows. The official team cannot satisfy all needs.
The official team only retains the core runtime scheduler and hands the rest over to the Plugin ecosystem.
After seeing how Mods work, the first thing that came to mind was DeepSeek Harness, and the other was Antigravity.
Antigravity also adjusted an old feature a while ago, highly similar to Mods, called “Lifecycle Hooks”. The implementation logic is different, but the ultimate idea is the same; however, Antigravity did not do it thoroughly enough and built this feature in a patch-like way.