LangSmith vs Arize Phoenix

Detailed side-by-side comparison to help you choose the right tool

LangSmith

🔴Developer

AI Observability

LangSmith is LangChain's commercial observability, evaluation and prompt management platform for LLM apps and agents in production.

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Starting Price

Free
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Arize Phoenix

🔴Developer

AI Observability

Arize Phoenix is an open-source AI observability and evaluation platform for tracing, testing, and improving LLM applications and agents.

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Starting Price

Free
Full ReviewVisit Site

Feature Comparison

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FeatureLangSmithArize Phoenix
CategoryAI ObservabilityAI Observability
Pricing Plans3 listed plans4 listed plans
Starting PriceFreeFree
Key Features
  • • Tracing for any LLM stack via Python/TypeScript SDKs or OpenTelemetry
  • • LLM-as-judge, code-based and pairwise evaluations
  • • Versioned prompts with production A/B traffic splits
  • • LLM Tracing & Observability
  • • Evaluation Framework
  • • Experiment Management

💡 Our Take

Choose LangSmith for managed SaaS convenience, integrated prompt hub, and first-class LangChain support. Choose Arize Phoenix if you want a fully open-source, self-hostable observability tool with strong focus on RAG evaluation and embedding-space analysis, especially if you already use Arize's broader ML observability platform.

LangSmith - Pros & Cons

Pros

  • ✓Best-in-class integration if you already use LangChain or LangGraph.
  • ✓Eval suites are practical enough to actually gate releases on, not just dashboards.
  • ✓Self-hosted Enterprise tier covers SOC 2 and regulated environments.

Cons

  • ✗Per-trace pricing on Plus surprises teams that scale production traffic quickly.
  • ✗Non-LangChain stacks work but trade ergonomic polish for SDK overhead.
  • ✗Some eval features require additional LLM spend on top of the platform fee.

Arize Phoenix - Pros & Cons

Pros

  • ✓Open-source Phoenix can run locally or on controlled infrastructure without a software license fee.
  • ✓OpenTelemetry tracing reduces instrumentation lock-in.
  • ✓Datasets, experiments, evaluations, and Prompt IDE connect evidence to changes.
  • ✓AX Free and Pro include unlimited users and evaluations at published prices.

Cons

  • ✗Self-hosting shifts upgrades, storage, access control, backups, and availability to the user's team.
  • ✗Agent runs can generate many spans, consuming 25,000 or 50,000 allowances quickly.
  • ✗Managed retention of 15 or 30 days may be short for audits or long incident cycles.
  • ✗Fetched pages did not explicitly document native MCP support.

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🔒 Security & Compliance Comparison

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Security FeatureLangSmithArize Phoenix
SOC2✅ Yes✅ Yes
GDPR✅ Yes✅ Yes
HIPAA—❌ No
SSO✅ Yes❌ No
Self-Hosted🔀 Hybrid✅ Yes
On-Prem✅ Yes✅ Yes
RBAC✅ Yes❌ No
Audit Log✅ Yes❌ No
Open Source❌ No✅ Yes
API Key Auth✅ Yes✅ Yes
Encryption at Rest✅ Yes✅ Yes
Encryption in Transit✅ Yes✅ Yes
Data ResidencyUS, EUAvailable
Data Retentionconfigurableconfigurable
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Review LangSmithReview Arize Phoenix