Kosmoy vs Arize: AI Evaluation and Governance Compared (2026)

Each spoke is one capability, scored 0–10; the further a point sits from the centre, the stronger the product. Arize's shape peaks exactly where you would expect — Testing, Evals & Red-teaming (9 vs 7) and Observability & FinOps (9 vs 7) both go to Arize, and its Kubernetes-first self-hosted tier earns an 8 on sovereignty. Kosmoy's shape is the wider web: inventory, gateway, containment and compliance are where the gap runs the other way, and sovereignty is the one axis it scores 10.

Evaluation depth. Arize's Evaluator Hub versions LLM-as-a-judge evaluators at commit level, with datasets, experiments and online evals on production traffic (Arize AX). Kosmoy ships 20 evaluators across six dimensions with offline and online runs — comprehensive, and newer; Arize leads on experiment workflow, evaluator versioning and annotation depth.

Production observability. OpenTelemetry tracing, Signal continuous trace review and voice-agent replay across AX and Phoenix make Arize a category leader on tracing granularity (Phoenix). Kosmoy tracks cost, usage and agent traces per model, app and user — solid, gateway-native observability, less granular step-level debugging.

Open-source on-ramp. Phoenix (Apache-2.0, 2M+ monthly downloads) lets a single engineer adopt Arize's tracing and evals this afternoon. Kosmoy has no open-source tier; procurement runs through an enterprise sales process.

Evaluator ecosystem. Pre-built evaluator templates, an LLM-as-a-judge guide the category cites, and the Alyx copilot give Arize a maturity on eval authoring that a 2026-vintage suite does not yet match.

Inventory beyond the SDK. Arize's projects and spaces exist inside the platform, for apps you have instrumented. Kosmoy's four registries cover the whole estate: connectors pull agents from Azure AI Foundry, Bedrock, Vertex, Salesforce and ServiceNow into one master list, each with an owner and a risk tier. If the question is “what AI do we run?”, only one of these products tries to answer it.

A gateway, not an SDK. Arize's runtime Guards intercept at SDK level inside the application. Kosmoy's AI Gateway is a traffic chokepoint: one OpenAI-compatible policy point across LLM, MCP and A2A calls, with RBAC, routing, budgets and guardrails enforced on every request — and a red-team finding becomes an enforced rule there.

Agent containment. Arize observes and evaluates agents; it documents no sandbox or kill switch. Kosmoy's Action Capsule runs each agent, MCP server or private model in a kernel-enforced sandbox whose only egress is its paired gateway, with per-task credentials and a kill switch.

Compliance evidence. Arize documents SOC 2 and HIPAA for itself but no EU AI Act, ISO/IEC 42001 or NIST AI RMF tooling for its customers (not documented as of July 2026). Kosmoy produces framework-ready evidence bundles from registry state, gateway logs and evaluation runs — one source, every audit.

Deployment as a governance fact. Arize AX self-hosts Kubernetes-first; Kosmoy is only ever single-tenant software in your Kubernetes, air-gap capable, with no vendor control plane to trust — which is why sovereignty is the one axis scored 10.

These two coexist cleanly because they instrument different layers. Arize lives in the application via its SDK, giving engineers deep traces and eval experiments; Kosmoy lives in the traffic path and the registry, giving the organization inventory, enforcement, containment and compliance evidence. A team can run Arize for the engineering build loop while Kosmoy governs the path to production — and because Kosmoy's own evaluation suite reads gateway traffic, the two eval stories complement rather than collide. If the requirement is one platform that both evaluates and enforces in your own perimeter, that is the Kosmoy case; if it is the deepest possible eval and tracing toolkit for engineers, keep Arize in the mix.