Claude Code Mods explained: run JS modules in-session to build a programmable agent runtime
bibryam · x · 2026-10-31
- Claude Code Mods are a programmable extension layer (like stateful hooks): instead of only prompting the agent, you run JavaScript modules inside the session to customize behavior.
- How it works:
- Mods load into the session and react automatically to agent events (tool calls, turn completions, UI updates);
- Each event passes through the mod as middleware — observe, rewrite, or intercept and return a custom result (e.g. deny a risky command);
- $state.set/get maintains state across turns within the session;
- Custom UI via $ui.status/$ui.panel for status bars and interactive panels.
- Why it matters: stateful multi-turn workflows, deterministic behavior without prompt-reliance, custom guardrails and dev tooling. Claude Code is becoming a programmable agent runtime, not just a coding assistant.
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