garak is a CLI tool and Python library for automated red-teaming and vulnerability scanning of large language models (LLMs). It systematically probes models with adversarial inputs (jailbreaks, prompt injections, encoding attacks, etc.) and uses detectors to classify model responses for safety failures. It supports multiple model backends (OpenAI, Anthropic, HuggingFace, etc.) and generates structured reports with severity scoring. The system follows a modular plugin architecture with base classes for probes, detectors, generators, harnesses, evaluators, and buffs. Plugins are dynamically loaded and configured via a hierarchical config system. The default harness runs probes with their associated detectors, while a cross-product harness allows all probes against all detectors. Results are logged as JSONL and can be visualized via a React-based web UI (garak-report) that displays DEFCON-level severity, calibration Z-scores, and technique-intent matrices. While primarily an application, garak incorporates significant research elements: it implements state-of-the-art attack techniques (GCG, AutoDAN, BEAST, TAP) and includes curated datasets of adversarial prompts and calibration data. The codebase serves both as a practical security tool and as a research platform for LLM vulnerability assessment.