Arthur Shield - 2026 Pricing, Features, Reviews & Alternatives

Arthur Shield is an LLM firewall that sits between the application layer and the LLM deployment layer, validating user prompts and model responses in real time across two dedicated endpoints: input and output. Configurable detection rules cover PII and sensitive data leakage, hallucinations, prompt injection attempts, toxic language, profanity, and other quality metrics. Compatible with OpenAI and other leading LLMs, Arthur Shield deploys as SaaS or on-premises and integrates with AWS, Azure, and other major cloud providers via an API-first design, requiring no major infrastructure changes to existing LLM applications.

Arthur Shield targets companies of all sizes deploying LLM-based applications, with particular focus on enterprises in regulated industries such as banking, healthcare, insurance, financial services, and fintech. The platform serves AI/ML engineering teams, data scientists, security teams, and governance and compliance leaders including CISOs, CIOs, and CDOs. Detection capabilities include a dedicated hallucination detection model, a precision-prioritized prompt injection classifier, a PII detection model with post-processing enhancements, and a toxicity classifier supporting inputs up to 8,000 tokens with a chunking strategy for harmful request classification.

All detections operate as configurable, auditable rules applied at inference time, giving organizations granular control over which safety checks are active and how flagged interactions are handled. Inference deep-dive capabilities allow teams to inspect flagged prompts and responses in detail. By intercepting unsafe or policy-violating LLM outputs before they reach end users, Arthur Shield reduces reputational, operational, and compliance risk associated with production LLM deployments.