Best Arize Phoenix Alternatives in 2026

Braintrust is an eval-first observability platform for teams shipping LLM products, wiring tracing, datasets, scorers, and CI/CD quality gates into one workflow. Used by OpenAI, Stripe, and Notion, it is premium and proprietary, with a steep jump from free to paid.

Opik is Comet's open-source (Apache 2.0) LLM observability and evaluation platform: tracing, 30+ judge metrics, real-time guardrails, and a distinctive automated agent optimizer. Free to self-host with a $19/month cloud tier, it undercuts the premium eval platforms.

DeepInfra is a low-cost, OpenAI-compatible inference API for 150+ open models, processing trillions of tokens a week on its own GPU stack. It is among the cheapest providers, with documented price-stability and support trade-offs to weigh.

Kong AI Gateway is the LLM and agent traffic-governance layer on Kong's open-source API gateway, unifying routing, token quotas, caching, PII guards, and observability. By 2026 it governs LLM, MCP, and agent-to-agent traffic from one control plane.

Baseten is a managed inference platform for deploying custom and fine-tuned AI models to production as autoscaling APIs. With Truss packaging, Chains pipelines, and HIPAA compliance, it targets ML teams shipping their own models, and it is backed by an NVIDIA-led 2026 round.

Nebius is a Nasdaq-listed AI cloud offering large-scale NVIDIA GPU compute plus the Token Factory inference API for open models. EU data residency, enterprise governance, and an NVIDIA investment make it a serious option for training and production inference.

Composio is a managed tool-integration and auth layer that lets AI agents take real actions across 1,000+ apps without hand-rolling OAuth. With broad coverage, framework support, and the Rube MCP server, it favors fast prototyping over enterprise identity governance.

Fireworks AI is an inference platform that runs open-source and custom models on a fast, OpenAI-compatible API. Built by ex-Meta PyTorch engineers, its FireAttention engine targets best-in-class throughput, which is why latency-sensitive products like Cursor and Notion run on it.

Langfuse is an open-source LLM observability and engineering platform used by AI teams to trace, debug, evaluate, and manage prompts in production. MIT-licensed, self-hostable, and trusted by over 63 Fortune 500 companies including Khan Academy.

SiliconFlow is a China-based inference platform offering one OpenAI-compatible API to 200+ models, including the DeepSeek, Qwen, GLM, and Kimi families. It is cheap and broad, but China data residency and a real-name verification requirement make it a careful choice for Western teams.