Fiddler AI vs Patronus AI

Fiddler AI is an observability, evaluation and guardrails platform that now calls itself "the control plane for enterprise AI agents." It was founded in October 2018 by Krishna Gade (CEO), formerly an engineering manager at Facebook, and Amit Paka (COO), and is based in Palo Alto, California. It has raised $100 million; its latest round was a $30 million Series C led by RPS Ventures in January 2026, with Lightspeed Venture Partners, Lux Capital and Insight Partners among the existing investors taking part. Fiddler says its revenue grew more than fourfold in the 18 months before that round. Customers shown on its site include Nielsen, Integral Ad Science, Qualtrics, Thumbtack, LendingPoint, American Family Insurance and the US Department of Energy. The platform covers two kinds of AI. For predictive models, ML Observability tracks performance, drift and data integrity with root-cause analysis, gives global and local explanations, and runs fairness checks such as disparate impact, equal opportunity and demographic parity on structured, text and image models. For LLM applications and agents, it ingests OpenTelemetry traces (with integrations for LangGraph, LangChain, Strands Agents, Google ADK, Claude Code and LiteLLM), scores them with 80+ built-in metrics, custom evaluators or your own LLM judge, and runs experiments against golden datasets. Its Guardrails, powered by Fiddler's own Centor models, screen prompts and responses for hallucinations (faithfulness), toxicity, jailbreaks, prompt injection and 35+ types of PII and PHI. Fiddler says enforcement takes under 80 ms and runs inside the customer's cloud or VPC with no data leaving it. Deployment options are SaaS, VPC, AWS GovCloud and on-premises. **AI compliance coverage** Fiddler's governance features are audit trails that record every decision, action, evaluation and policy outcome, plus executive dashboards. Its governance page names SR 11-7, HIPAA and NAIC, and lists the EU AI Act among relevant policies; its Control Plane FAQ says its audit trails support the NIST AI RMF, ISO/IEC 42001, HIPAA, SR 11-7, NAIC and the EU AI Act. It doesn't publish control mappings, templates or a model inventory for any of them. Fiddler says it has a SOC 2 Type II report and is HIPAA compliant. In 2023 it released Fiddler Auditor, a free LLM red-teaming and robustness library under the Elastic License 2.0, but its last release was in November 2023 and red-teaming isn't part of the current platform. **Who it's for** Enterprises in financial services, insurance, healthcare and government that run predictive models and LLM agents in production and want monitoring, evaluation and runtime guardrails in one place, often inside their own cloud. It is an observability and enforcement layer, not a governance workflow tool: teams that need AI inventories, risk assessments and policy workflows will need a governance platform alongside it.

Patronus AI was founded in 2023 by Anand Kannappan (CEO) and Rebecca Qian (CTO), who both previously worked on AI at Meta, and is based in San Francisco. It launched in September 2023 as an LLM evaluation company for regulated industries. It raised a $3 million seed round led by Lightspeed Venture Partners, then a $17 million Series A led by Notable Capital in May 2024. In June 2026 it raised a $50 million Series B led by Greenfield Partners, with Lightspeed, Notable Capital, Datadog and Samsung, bringing its total to $70 million. **What it sells now** Its homepage now says: "Patronus AI is a research lab developing training data and simulated environments for frontier AI." The products page offers Frontier Training Data: tasks with reference solutions and graders, and ready-built or custom simulated environments for software development, computer use and knowledge work, delivered to run in a lab's own training infrastructure. In December 2025 it launched Generative Simulators and RL Environments, which generate tasks and rules and adapt them as an agent learns. In June 2026 it announced Digital World Models, replicas of websites and company systems where agents can practice. Patronus says most leading frontier labs and hyperscalers are customers but names none, and it reports revenue growth of more than 15 times over the past year. **The evaluation platform** Patronus's documentation still describes the evaluation product the company started with. It includes an API and SDK with off-the-shelf evaluators (among them Lynx for hallucination detection and the small Glider evaluator model), custom evaluators, experiments, logs, tracing and Percival, launched in May 2025 to find failures in agentic systems and suggest fixes. Evaluation Runs and the Experimentation SDK are Enterprise features. An older landing page names OpenAI, HP and Pearson as customers and offers on-premise deployment. The homepage, products page and pricing page no longer mention the platform. **AI compliance coverage** Patronus doesn't map its products to any AI regulation or standard and publishes no security certifications. Its older landing page says it is vetted by third-party security firms each year. **Who it's for** Frontier AI labs and large AI teams that buy training data and agent environments. Teams looking for an evaluation or observability tool to support compliance work should confirm that the evaluation platform is still sold and supported before buying.