Best Braintrust Alternatives in 2026

Arize Phoenix is an open-source, OpenTelemetry-native observability and evaluation platform for LLM apps and agents. It traces every call, scores it with 50+ built-in evaluators, and self-hosts for free, which makes it the standard pick for vendor-neutral teams.

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.

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.

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.

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.

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.

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.

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.

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.

Weights & Biases is the standard ML experiment tracking platform used by over a million AI engineers. It covers model training workflows with W&B Models and LLM observability with W&B Weave, now under CoreWeave ownership since May 2025.