Looking for a LangSmith alternative for LLM evaluation, tracing, or prompt experimentation?
Whether you’re just getting started or scaling AI workflows across teams and environments, it’s critical to choose a solution that’s both robust and flexible. This page explores how Arize Phoenix (open-source) and Arize AX compare to LangSmith, a closed-source LLM app development platform built by LangChain.
What Is LangSmith?
LangSmith is a closed-source LLM application debugging and evaluation tool built by the creators of LangChain. It offers basic support for tracing, prompt evaluation, and dataset management—particularly tailored for LangChain workflows.
While LangSmith is polished and usable out of the box, it comes with several limitations:
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Tied to the LangChain ecosystem
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Self-hosting only available with a paid plan
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Closed codebase with limited extensibility
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Minimal enterprise support beyond SOC-2
Feature Comparison
| Capability | Arize Phoenix | Arize AX | LangSmith |
| Open Source Code | ✅ | – | ❌ |
| One-Click Deploy / Self-Host | ✅ Docker | ✅ VPC / On-Prem |
❌ (Enterprise only)
|
| Framework Agnostic | ✅ | ✅ |
⚠️ LangChain-centric
|
| Agent Tracing | ✅ | ✅ |
✅ (manual setup)
|
| Agent Graphs | ❌ | ✅ | ⚠️ Partial |
| Multi-Agent Session View | ❌ | ✅ | ⚠️ Limited |
| Token & Cost Tracking | ✅ | ✅ | ✅ |
| Auto-Instrumentation (OpenInference) | ✅ | ✅ | ❌ (SDK-based) |
| Multi-Modal Support | ✅ | ✅ | ✅ |
| Custom Metrics Builder | ✅ | ✅ | ⚠️ Limited |
| Dashboards (Custom) | 🔸 Built-in | ✅ Advanced |
✅ Customizable
|
| Monitoring & Alerts | ❌ | ✅ Full | ❌ |
| Offline Evaluations | ✅ | ✅ | ✅ |
| Online Evaluations (at scale) | ✅ | ✅ | ✅ |
| Online Playground Evals | Coming Soon | ✅ | ✅ |
| Annotation Queues | ✅ | ✅ | ✅ |
| Human-in-the-Loop | ✅ | ✅ | ✅ |
| AI Copilot / Insight Discovery | ❌ | ✅ | ❌ |
| Trace Search & Cohort Slicing | 🔸 Basic | ✅ Advanced | ⚠️ Manual |
| Data Export / DB Sync | UI & SDK | ✅ | ✅ |
| SSO / RBAC / Audit Logs | – | ✅ Full | ✅ (Enterprise) |
| HIPAA / VPC / On-Prem | – | ✅ | ✅ (Enterprise) |
| Pricing | ✅ Free | Usage-based (no eval/seat tax) |
Enterprise plan required for full features
|
🏠 Self-Hosting & Deployment Flexibility
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Phoenix: One-command Docker deployment, no license keys or paywalls.
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Arize AX: Deployed in your VPC or on-prem, with 99.9% SLA and enterprise SLAs.
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LangSmith: Self-hosting available only under paid Enterprise plan.
🧠 Evaluation & Tracing Capabilities
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Phoenix & AX:
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Full prompt, tool, and agent tracing
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Offline and online evaluations (millions per day)
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Pre-built and custom evaluators
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Annotation queues with auto metric recomputation
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LangSmith:
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Supports evaluations via LLM-as-judge and Python code
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Annotation queues exist, but no reconciliation workflows
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Agent tracing available via integrations, but multi-agent session graphs are limited
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📊 Monitoring, Alerts, and Enterprise Features
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Phoenix: Includes lightweight built-in dashboards
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Arize AX:
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Custom dashboards
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Alerting and routing (Slack, PagerDuty)
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Copilot for AI-powered insights and anomaly detection
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LangSmith:
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Supports custom dashboards for visualizing trace and cost metrics
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How To Choose
| Use Case | Best Fit |
|---|---|
| Prototyping, R&D, open evaluation | Arize Phoenix (OSS, free, flexible) |
| Enterprise AI Ops, compliance, scale | Arize AX (petabyte scale, VPC, HIPAA, Copilot) |
| LangChain-native debugging | LangSmith (if ecosystem fit is paramount) |