Fiddler AI vs LangSmith

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.

LangSmith is an LLM observability platform that provides tracing, monitoring, and evaluation for AI agents and LLM applications. It offers native tracing for agent frameworks, cost and latency tracking, online LLM-as-judge evals, custom dashboards, and alerts via webhooks or PagerDuty. Framework-agnostic with SDKs for Python, TypeScript, Go, Java, and OpenTelemetry support, it works with OpenAI, Anthropic, LlamaIndex, and custom stacks. Typical buyers are engineering teams building production LLM apps needing visibility into agent behavior, debugging failures, and performance optimization. Enterprise plans include self-hosted and BYOC options for data residency.LangSmith homepage Pricing