CAITLYN

CAITLYN is an adaptive security middleware for LLM agents. It scans untrusted content through a fast executable-skill layer and a context-sensitive LLM layer, and can synthesize verified defense skills from new counterexamples.

Full documentation, architecture, evaluation results, and limitations are available in the project repository.

Install

CAITLYN requires Node.js 22.19 or newer.

Install the command-line interface globally:

npm install -g caitlyn
caitlyn status
caitlyn

The package also installs caitlyn-hook, which is used by supported agent integrations.

For project-local use:

npm install caitlyn
npx caitlyn status

Tier 0 scanning works without an API key. Tier 1 and defense synthesis require a supported model provider. The guided setup writes provider, Agent, detection, and privacy settings only after a final confirmation. Privacy protection stays off unless that setup enables it and chooses standard or strict:

caitlyn setup

caitlyn setup --no-connection-test skips the live API probe. /setup in the TUI runs the same flow. Alternatively, export a provider key:

export OPENROUTER_API_KEY="your-key"

Protect an agent

caitlyn detect
caitlyn install --dry-run codex
caitlyn install codex
caitlyn daemon start
caitlyn watch --status

Supported adapters include Claude Code, Codex, OpenCode, Hermes, OpenClaw, and Pi Coding Agent. Configuration changes are backed up before installation.

Commands

| Command | Purpose | | --- | --- | | caitlyn or caitlyn tui | Open the full-screen terminal interface | | caitlyn scan <content> | Scan content | | caitlyn status | Inspect the defense and attack libraries | | caitlyn detect | Detect supported agents | | caitlyn setup | Guided provider, Agent, and detection setup | | caitlyn install <agent> | Install an agent integration | | caitlyn uninstall <agent> | Remove an integration and restore its backup | | caitlyn daemon start\|stop\|status | Manage the local daemon | | caitlyn synthesize <pattern> | Submit a System II trigger | | caitlyn update --check | Check for a newer release |

Library use

The package exposes its scanner and filesystem-native defense library:

import {
  createUnavailableLlmCall,
  loadDefenseSkills,
  loadAttacks,
  scan,
} from "caitlyn";

const result = await scan({
  defense skills: loadDefenseSkills(),
  attacks: loadAttacks(),
  content: "untrusted content",
  llmCall: createUnavailableLlmCall("Tier 0 only"),
});

License

MIT