Phoenix
Free tierThe open-source platform for AI agent development, tracing, and evaluation
Free tier available·Technical·Powered by Vendor Agnostic·API available·Open source
Key strengths
Open-source LLM observability and agent tracingLLM-as-judge and human annotation evaluationNative OpenTelemetry support with no vendor lock-inSelf-hostable / local deploymentVendor and model agnosticExperiment and dataset management for iterative improvement
Free tier + paid plans · from $50 USD/mo
US
Self-hostable
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Recent changes
- Starting price: $0/mo → $50/mo
- Plans updated: AX Free (free, 25k spans/mo, 1 GB, 15-day retention, SaaS); AX Pro ($50/mo, 50k spans/mo, 10 GB, 30-day retention, SaaS); AX Enterprise (custom, SaaS or Self-Hosted)
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Arize Phoenix — Technical Overview
Arize Phoenix is an open-source AI observability and evaluation platform purpose-built for engineers shipping LLM-powered applications and AI agents. It is vendor- and model-agnostic, meaning it integrates with any LLM provider or framework without lock-in.
Key technical characteristics:
- Native OpenTelemetry support — traces are collected via the OTel standard, making Phoenix a drop-in fit for existing observability pipelines.
- Agent & LLM tracing — deep span-level visibility into LLM calls, retrieval steps, tool use, and multi-step agent workflows.
- Evaluation framework — supports LLM-as-judge automated evaluation and human annotation workflows for scoring traces and datasets.
- Experiment & dataset management — version datasets and run iterative experiments to track prompt and model changes over time.
- Deployment flexibility — run locally, self-host on your own infrastructure (Docker, Kubernetes), or use the managed SaaS offering (AX Free / Pro / Enterprise).
- Integrations — LlamaIndex, Docker, Kubernetes, OpenTelemetry, Slack, NVIDIA NeMo Agent Toolkit.
- ~10,000 GitHub stars, reflecting strong open-source adoption.
Pricing tiers (SaaS):
| Tier | Price | Spans/mo | Storage | Retention |
|---|---|---|---|---|
| AX Free | $0 | 25k | 1 GB | 15 days |
| AX Pro | $50/mo | 50k | 10 GB | 30 days |
| AX Enterprise | Custom | Custom | Custom | Custom |
AX Enterprise also supports self-hosted deployment.
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