Arize Phoenix is one of the most popular open-source LLM observability platforms in 2026. If you are evaluating it alongside CortexOps, this article compares them directly on the things that matter for production agent workloads.

Short version:

• Arize Phoenix is the right choice if you are doing notebook-based experimentation, RAG evaluation, or need embeddings analysis. It is well-established with 9,000+ GitHub stars and strong OTel support.

• CortexOps is the right choice if you need a first-class CI/CD deployment gate, multi-framework agent tracing beyond LangGraph, or a flat-rate pricing model that doesn't get expensive at agent-scale span volumes.

What They Are

Arize Phoenix is an open-source LLM observability and evaluation platform from Arize AI. It self-hosts in one command, uses OpenTelemetry for tracing, and includes built-in evaluators covering faithfulness, relevance, hallucination, and toxicity. Phoenix supports popular frameworks including OpenAI Agents SDK, LangGraph, CrewAI, LlamaIndex, and DSPy.

CortexOps is an open-source AI agent observability platform focused on the full production lifecycle — tracing, evaluation in CI/CD, and continuous monitoring. It supports 12 agent frameworks via a unified instrumentation layer and ships a CLI-based deployment gate that exits with code 1 when quality drops below a configured threshold.

One Important Distinction

Phoenix is optimized for prompt-centric experimentation and LLM-as-judge evals in a notebook-friendly self-host. When your app stops looking like a notebook — a production agent that runs for ten minutes, calls fifteen tools, spawns a sub-agent, and fails four tool calls deep — you open Phoenix and get a span tree. You wanted to know what the agent said to the user, what the user said back, and which tool call threw.

CortexOps is designed for that second scenario: debugging multi-node agent failures in production with a structured execution waterfall, not a flat span list.

Feature Comparison

Tracing

Both platforms use OpenTelemetry. Phoenix ships OpenInference — the most widely adopted set of OpenTelemetry semantic conventions for LLM spans. CortexOps uses the emerging OTel LLM semantic conventions directly.

Phoenix instrumentation for LangGraph:

from phoenix.otel import register
tracer_provider = register(project_name="my-agent")
# Auto-instruments LangGraph calls

CortexOps instrumentation:

from cortexops import CortexTracer
tracer = CortexTracer(api_key="cxo-...", project="my-agent")
agent  = tracer.wrap(your_compiled_graph)

Both get you traces. The difference is in what you see: Phoenix shows a span tree. CortexOps shows a node waterfall organised by agent execution flow — which node ran, in what order, how long each took, and which tool calls happened inside each node.

Winner: Roughly equal for tracing. Phoenix has more mature OTel conventions. CortexOps has better agent-native execution view.

Evaluation

Phoenix has a strong evaluation suite. Built-in evaluators cover faithfulness, relevance, hallucination, toxicity, and custom criteria. LLM evaluators use function calling to extract structured judgments rather than parsing freeform text.

CortexOps evaluation uses a golden dataset approach with three built-in rubrics (task completion, response quality, safety) plus a CLI gate:

cortexops eval run \
  --dataset datasets/my_agent.yaml \
  --judge \
  --fail-on "task_completion < 0.90"

Phoenix can be integrated into CI/CD but requires custom scripting. The approach: run experiments on every PR, check scores against thresholds in a Python script, and use exit code to reflect pass/fail. CortexOps ships this pattern out of the box as a first-class CLI command and GitHub Action.

Winner: Phoenix for RAG and research-oriented evals. CortexOps for CI/CD deployment gates.

Pricing at Agent Scale

AX Free is 25k spans and 1GB at 15-day retention. AX Pro is $50/month for 50k spans and 10GB at 30-day retention. Graduating from Phoenix to AX is a new contract, not a tier upgrade, and span-based pricing gets expensive on agent workloads.

A production agent with 10 nodes running 1,000 times per day generates roughly 100,000 spans per day — 3 million per month. That is 60x the AX Pro limit at $50/month.

CortexOps Pro is $49/month for unlimited traces. No span counting.

Winner: CortexOps for high-volume agent workloads. Phoenix/AX for lower-volume experimentation.

License

This matters for some teams. Phoenix uses the Elastic License 2.0, which restricts certain commercial use cases (you cannot offer Phoenix as a managed service to others). CortexOps is MIT — no restrictions.

Winner: CortexOps if license flexibility matters.

When to Choose Arize Phoenix

• You are doing RAG development and need embeddings analysis and context relevance metrics
• You want notebook-friendly local development with a mature, established platform
• You are already in the Arize ecosystem for traditional ML monitoring

• You need the breadth of Phoenix's built-in evaluator library

  When to Choose CortexOps

• You need a CI/CD deployment gate that blocks merges on quality regression

• Your agent uses multiple frameworks (CrewAI + OpenAI SDK + LangGraph simultaneously)

• Span-based pricing would get expensive at your trace volume

• MIT license matters for your use case

- You want a flat-rate Pro plan

Try Both

Both are open source with free tiers. The fastest way to decide:

# Phoenix
pip install arize-phoenix
python -m phoenix.server.main  # starts on localhost:6006

# CortexOps
pip install cortexops
# 3 lines to your first trace — getcortexops.com

Links:

• CortexOps: getcortexops.com | github.com/ashishodu2023/cortexops

- Arize Phoenix: arize.com/phoenix | github.com/arize-ai/phoenix

Ashish Verma is a Senior AI Engineer at PayPal and co-founder of CortexOps. This comparison reflects publicly available information as of June 2026.