Best Alternatives to Harden in 2025

Guardrails AI is an open-source framework for adding programmable validations and safety checks to AI outputs. It can be used to validate tool calls and enforce security policies, though it may require more custom development than Harden's pre-trained model.

Lakera Guard provides real-time protection against prompt injection, data leakage, and other AI security threats. It offers a cloud-based API that can be integrated with AI coding agents to screen inputs and outputs, but it may not keep all data local like Harden.

Rebuff AI is a self-hardening prompt injection detector that can be used to protect AI agents from malicious inputs. It offers a combination of heuristics and LLM-based detection, and can be deployed locally, making it a good alternative for those prioritizing data privacy.

NeMo Guardrails is an open-source toolkit for adding programmable guardrails to LLM-based conversational systems. It allows you to define safety policies and can be extended to validate tool calls, but it may require significant setup and customization.

Protect AI Guardian is a security solution for AI/ML models and applications, offering scanning and runtime protection. It focuses on model supply chain security and can help secure AI coding agents, but it is more enterprise-oriented and may not be free.

Arthur Shield provides real-time guardrails for LLM applications, including hallucination detection, PII protection, and prompt injection defense. It offers a cloud-based solution with a focus on observability, but it may not offer the same local-first approach as Harden.

CalypsoAI Moderator is a platform for securing and monitoring AI interactions, with features like policy enforcement and threat detection. It is designed for enterprises and can integrate with AI coding agents, but it is a commercial product and may not be suitable for individual developers.