Anthropic lets developers rewrite Claude Code with TypeScript mods

Anthropic released mods for Claude Code on 1 October. It calls them small TypeScript functions that can "rewrite a prompt, add new UI, replace a built-in feature, or add entirely new functionality." Mods are available now, the company said. They work in the command-line tool and the desktop app. TestingCatalog posted a demo clip and said the approach could reach most client-side software.

https://x.com/testingcatalog/status/2105752819441525182

Anthropic's blog post says each action in Claude Code emits an event and a mod hooks into it. A mod can run before an event, after it or in place of it, and several mods stack in load order. Anthropic lists rewriting prompts, blocking or changing tool calls, redacting sensitive output and adding buttons among the things a mod could do.

Mods ship inside plugins and install through the Claude directory or the /plugin command, Anthropic said. It also said the built-in /diff feature now runs as a mod, so users can turn it off or replace it, and that more built-in features are planned to follow. A community repository by konsta95 already lists three mods, including a status line, though it showed no stars when we read it.

Anthropic's getting-started guide walks through Token Weather, an 80-line mod that shows context-window use above the prompt with weather icons. It also describes Blast Radius, which holds risky Bash calls and shows what they would change, and Replay Theater, which lets users step through a turn's file edits.

Anthropic warned that mods run with full machine access and are not sandboxed, so users should install them only from trusted sources. On Team and Enterprise plans a security mod called sec-default loads first to stop risky operations, the company said, and administrators can deploy their own mods and audit logging. No independent testing of the feature had been published when we checked.