CalypsoAI vs Prompt Security

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.

Prompt Security is an AI security product that controls how employees use AI tools and protects the AI applications and agents companies build. Itamar Golan (CEO) and Lior Drihem (CTO), who had worked at Check Point and Orca Security, founded it in August 2023; it is based in Tel Aviv. It raised $23 million: a $5 million seed round led by Hetz Ventures (January 2024) and an $18 million Series A led by Jump Capital (November 2024), with Ridge Ventures, Okta and F5 joining. SentinelOne, the Mountain View, California security company, agreed to buy Prompt Security on August 5, 2025 and completed the deal on September 5, 2025. Its Form 8-K puts the consideration at approximately $180 million in cash and SentinelOne Class A stock. Prompt Security is still sold under its own name, as part of SentinelOne's Singularity Platform. The product page is on sentinelone.com; prompt.security now hosts research and free tools such as the open-source Prompt Fuzzer, and the old press release we checked there redirects to SentinelOne. **What it does** SentinelOne's Prompt Security page lists three areas. AI Usage Control inventories the AI tools and code assistants employees and developers use, including unsanctioned shadow AI, and redacts sensitive data and enforces policies across more than 15,000 AI services in real time. It also covers GitHub Copilot, Cursor and Claude Code, keeping secrets and intellectual property out of them. AI Application Security tests homegrown AI apps for prompt injection, jailbreaks and data poisoning before deployment, runs a real-time AI firewall, and turns red-team findings into guardrails. Agentic AI Security finds shadow MCP servers and unsanctioned agents, enforces least-privilege access for agents and keeps a searchable audit log. SentinelOne says Prompt's MCP gateway scores the risk of more than 13,000 known MCP servers and can allow, block, filter or redact their actions. Prompt deploys through a lightweight agent and browser extensions, and covers major LLM providers, including OpenAI, Anthropic and Google, and self-hosted models. **Product changes since the acquisition** At its OneCon conference in November 2025 SentinelOne launched Prompt Security for Employees, for AI Code Assistants and for AI Applications, plus Prompt Security for Agentic AI in beta. At RSAC in March 2026 it announced Prompt AI Agent Security, a discovery and governance control plane for agents and MCP servers (agent posture management was in preview), and Prompt AI Red Teaming for testing homegrown AI apps. **Frameworks** Neither SentinelOne's Prompt Security pages nor prompt.security name the EU AI Act, ISO 42001 or the NIST AI RMF; they refer only to meeting compliance requirements in general terms. This profile lists no frameworks. **Who it's for** Companies that want to let employees use generative AI and coding assistants while controlling data exposure, especially existing SentinelOne customers. Named customers include 10x Banking and Carnival Corporation.