Arthur vs CalypsoAI

Arthur provides an AI Delivery Engine that enables teams to launch, secure, and optimize AI applications across the full lifecycle, from pre-production evaluations to runtime guardrails and production monitoring. The platform supports traditional machine learning, generative AI, and agentic AI with metrics for data drift, accuracy, hallucinations, toxicity, PII detection, and custom evals, while keeping sensitive data local via a federated data-control plane architecture. It targets enterprise AI teams in regulated sectors like banking, healthcare, and insurance, offering deployment flexibility (SaaS, on-prem, AWS, GCP) and integrations like webhooks to Slack/Jira. Distinct from peers, Arthur emphasizes agent discovery & governance and open-source Evals Engine components for real-time performance insights.Arthur homepage, Arthur platform, pricing, PR Newswire Series B, ZoomInfo, LinkedIn

CalypsoAI was an AI security company founded in the US in 2018 by Neil Serebryany, its first CEO; it describes itself as founded in Silicon Valley, and its early press releases carry Washington datelines. It began with software for testing, validating and monitoring AI and machine learning models for national security, finance and other regulated customers, and moved to securing generative AI with CalypsoAI Moderator in 2023. Donnchadh Casey became CEO in August 2024. In October 2024 CalypsoAI named Dublin its global co-headquarters, alongside a US headquarters in New York; IDA Ireland says the CEO, the CTO and most of its R&D were based in Dublin. Paladin Capital Group led its $13 million Series A (July 2020) and a $23 million Series A-1 (June 2023), and F5 says it raised more than $40 million in venture funding. Investors also included Lockheed Martin Ventures and Hakluyt Capital. F5 announced on September 11, 2025 that it would acquire CalypsoAI for $180 million in purchase consideration, mostly cash. F5's 10-Q says the deal closed on September 26, 2025 and records $145.2 million in cash consideration. CalypsoAI is no longer sold separately: calypsoai.com now redirects to F5's AI Guardrails page. F5 introduced F5 AI Guardrails and F5 AI Red Team when it announced the close, and made both generally available in January 2026. Buyers should evaluate those products. **What it sold** By 2025 CalypsoAI sold an inference security platform with two main products. Inference Defend checked prompts and responses in real time to block prompt injection, jailbreaks and sensitive data leakage, using custom scanners that could be versioned, tested and enforced per project. Inference Red-Team ran automated and agent-driven multi-turn attacks, drawing on more than 10,000 new attack prompts a month, and produced a risk score. The platform logged AI interactions for audit, sent logs to Splunk, and ran as SaaS, on premises or hybrid. In August 2025 CalypsoAI said an on-premises version of Red-Team, for organizations with strict data residency or air-gapped requirements, would soon be available in early access. **Frameworks** In August 2025 CalypsoAI added an EU AI Act scanner package to Inference Defend, covering four Article 5 prohibited-practice categories: manipulation, social scoring, biometric data harvesting and surveillance. F5's deal announcement said its governance features help customers meet GDPR and EU AI Act requirements. We found no CalypsoAI mapping to the NIST AI RMF or ISO 42001.