The 3 Best Lakera Guard Alternatives in 2026

NeMo Guardrails sits between your app and the model and enforces rules you define: input rails screen or rewrite user messages, dialog rails keep the conversation on approved paths, retrieval rails filter RAG chunks, execution rails check the inputs and outputs of tools the model calls, and output rails block or fix responses. Rules are written in Colang, a Python-like modeling language. It ships jailbreak and injection detection, self-check moderation and hallucination rails, NVIDIA safety models, and integrations with services such as ActiveFence. It runs as a Python library or a server, works with LangChain, and is free under Apache-2.0 (latest release 0.24.1, September 2026). Usage telemetry is on by default and can be turned off.

• Backed by NVIDIA, Apache-2.0
• Rails for tool calls as well as chat
• Dialog control no classifier API offers

Guardrails AI wraps model calls in a Guard made of validators: checks for toxic language, PII, competitor mentions, regex patterns, hallucination and more, each of which can block, fix or re-ask. It also forces structured output from a Pydantic model, using function calling where the model supports it. It runs in-process or as a REST server with an OpenAI-compatible endpoint. The framework is Apache-2.0 and downloaded over 250,000 times a month. Two 2026 changes matter: validators moved to ordinary PyPI packages and hosted remote inference ended on August 25, 2026, and the legal AI company Harvey acquired Guardrails AI on September 9, 2026. Harvey has not said what happens to the open-source project, so watch its activity.

• Composable validators for many risks
• Structured output from a Pydantic model
• Apache-2.0, runs in-process

Bedrock Guardrails applies configurable safeguards to model inputs and outputs: content filters for hate, violence, sexual content and prompt attacks (text and images), denied topics you describe in plain language, word filters, PII and regex masking, contextual grounding checks for hallucination against a source, and Automated Reasoning checks against logical rules. Through the ApplyGuardrail API it works with any model, including OpenAI, Gemini and self-hosted models, not only those on Bedrock, and security teams can enforce one guardrail across an AWS organization. Pricing is per 1,000 text units (up to 1,000 characters each): content filters and denied topics $0.15, sensitive-information filters and contextual grounding $0.10, word filters and regex free, Automated Reasoning $0.17 per policy. Input and output are each charged.

• Published per-unit pricing
• Works with any model via ApplyGuardrail
• Org-wide enforcement across AWS accounts