Top 10 LangSmith Alternatives (2025) – from LLM Tracers to Observability Tools

LangSmith popularized LLM tracing inside LangChain, but the market has since exploded with numerous LangSmith alternatives offering different approaches to LLM observability.

Leveraging a panel of experts and thorough reviews of docs and other materials, below we compare the ten LangSmith alternatives most often shortlisted by engineering teams across four lenses:

  1. Company maturity & funding
  2. Breadth of functionality – tracing, evaluation, monitoring, analytics
  3. Enterprise‑readiness – SOC‑2, OTEL, RBAC, on‑prem options
  4. Open‑source posture & lock‑in risk

Best LangSmith Alternatives by Key Use Case:

  • Open Source: Arize Phoenix (Elastic 2.0) or LangFuse (MIT)
  • Enterprise: Arize AX or Datadog
  • LangChain Integration: Arize Phoenix or LangSmith (proprietary)
  • Self-Hosting: Arize AX or Phoenix

LangSmith Alternative Company Facts & Funding

Founded HQ Latest Funding* OSS Core?
Arize AX 2020 San Francisco Series C ($70 M)
Partially (Phoenix)
Arize Phoenix 2023 San Francisco – (Apache-2) Yes (Elastic 2.0)
LangFuse 2023 Berlin Seed ($4 M) MIT
Braintrust 2022 Palo Alto Seed No
LangSmith 2023 New York Series A No
MLflow GenAI 2024 San Francisco Databricks (private) Apache-2
Datadog LLM Obs. 2024 New York NASDAQ: DDOG No
Galileo 2021 San Francisco Series B ($28 M) No
Fiddler 2018 Bay Area Series C ($47 M) No

LangSmith Alternative Feature Comparison Matrices (2025)

Dev & Deploy

Open Source Code One-Click Deploy / Self-Host
Framework Agnostic
Arize Phoenix Open source Docker one-click ✅
Arize AX – VPC / on-prem ✅
LangSmith ❌ ❌ (Enterprise only)
⚠️ LangChain-centric
Braintrust ❌ Self-host (hybrid/paid) ✅
LangFuse Open source Docker/K8s self-host ✅
Datadog ❌ SaaS + agents ❌
MLflow GenAI Open source Self-host supported ❌
Galileo ❌ VPC / on-prem (paid) ✅
Fiddler ❌ VPC / air-gapped (paid) ❌

LLM Tracing

Agent Tracing Agent Graphs Multi-Agent Session View MCP Tracing
Arize Phoenix Agent traces Agent graphs Multi-agent view ✅
Arize AX Agent traces Agent graphs Multi-agent view ✅
LangSmith ✅ (manual setup) ⚠️ Partial ⚠️ Limited ❌
Braintrust ❌ ❌ ❌ ❌
LangFuse Trace spans ❌ ❌ ❌
Datadog LLM traces Trace flow view Multi-agent trace ❌
MLflow GenAI Trace spans ❌ ❌ ❌
Galileo Trace timeline ❌ ❌ ❌
Fiddler LLM monitoring ❌ ❌ ❌

Evaluation

Offline Evaluations Online Evaluations (at scale)
Online Playground Evals
Arize Phoenix Offline evals At-scale online Coming soon
Arize AX Offline evals At-scale online
Playground evals
LangSmith ✅ ❌ ✅
Braintrust ✅ ✅ (⚠️ logs) ✅
LangFuse LLM judges ⚠️ Limited ⚠️ Basic
Datadog Code checks ⚠️ Limited ❌
MLflow GenAI Built-in judges Periodic monitoring ❌
Galileo Evaluate runs ⚠️ Limited ⚠️ Basic
Fiddler Guardrail scoring ⚠️ Limited ❌

Evals (Part II)

Annotation Queues Human-in-the-Loop AI Assistant / Agent Mode
Arize Phoenix ✅ Annotation queues ✅ HITL workflows ❌
Arize AX ✅ Annotation queues ✅ HITL workflows Alyx
LangSmith ✅ (Enterprise) ✅ (Enterprise) ❌
Braintrust ❌ ❌ ❌
LangFuse Basic queues Basic feedback ❌
Datadog ❌ ❌ ❌
MLflow GenAI ❌ ❌ ❌
Galileo Annotation queues HITL options ❌
Fiddler ❌ ❌ ❌

Instrumentation & Modalities

Auto-Instrumentation (OpenInference) Multi-Modal Support / Spans
Custom Metrics Builder
Arize Phoenix OpenInference Multi-modal spans Metrics builder
Arize AX OpenInference Multi-modal spans Metrics builder
LangSmith ❌ (SDK-based) Multi-modal ⚠️ Limited
Braintrust ❌ Multi-modal ❌
LangFuse ❌ ❌ Metric APIs
Datadog ❌ ❌ ❌
MLflow GenAI MLflow native Multi-modal ❌
Galileo ❌ ❌
Guardrail metrics
Fiddler ❌ ❌ Custom metrics

Dashboards, Alerts & Cost

Dashboards (Custom) Monitoring & Alerts
Token & Cost Tracking
Arize Phoenix Built-in dashboards Configurable Token & cost
Arize AX Advanced dashboards Customizable Slack, Pagerduty Token & cost
LangSmith ✅ Customizable ❌ ✅
Braintrust ❌ ❌ ✅
LangFuse ❌ ❌ Token & cost
Datadog Dashboard suite (paid) Alerts & thresholds (paid)
Tokens & cost (paid)
MLflow GenAI ❌ Periodic checks ⚠️ Via traces
Galileo Basic dashboards Guardrail alerts (paid) ❌
Fiddler Custom dashboards Guardrail alerts ❌

Search, Export & Support for Computer Vision and ML

Trace Search & Cohort Slicing Data Export / DB Sync
Support for Traditional ML/CV
Arize Phoenix Basic search UI & SDK Robust
Arize AX Advanced slicing Data sync Robust
LangSmith ⚠️ Manual SDK ❌
Braintrust ❌ ✅ ❌
LangFuse Search & filters Exports / API ❌
Datadog Trace queries APIs / export ❌
MLflow GenAI Trace search Artifacts / DB Traditional ML
Galileo Filters & drilldowns APIs / export ❌
Fiddler Cohort slicing APIs / export
Traditional ML/CV

Access, Compliance and Commercial

SSO / RBAC / Audit Logs HIPAA / VPC / On-Prem Pricing
Arize Phoenix Self-host Self-host Free
Arize AX Full RBAC / SSO HIPAA / VPC / On-Prem
Usage-based (no eval/seat tax)
LangSmith ✅ (Enterprise) ✅ (Enterprise)
Enterprise plan required
Braintrust SOC-2 only Self-host (hybrid/paid)
Seat + eval + retention fees
LangFuse RBAC / SSO SOC 2 Type II
SaaS tiers + OSS
Datadog Full RBAC SaaS; agents on-prem
Enterprise (paid)
MLflow GenAI  Self-host Self-host
OSS + managed
Galileo Full RBAC VPC / on-prem (paid)
Enterprise (paid)
Fiddler Full RBAC VPC
Enterprise (paid)

LangSmith Alternative Platform Profiles (Pros & Drawbacks)

Arize AX — Petabyte‑scale backend with real-time monitoring, custom dashboards, and Alyx Copilot AI assistant. Widely popular because most features are free. Enterprise features like on-prem deployment or agent trajectory analysis. Drawback: commercial SaaS pricing (VPC/HIPAA available).

Arize Phoenix — Elastic 2.0 licensed with robust monitoring, evaluations, and more. Self-host options with seamless upgrade path to AX. Drawback: Alyx Copilot and managed dashboards only available in AX.

LangFuse — MIT licensed with active community (13k+ GitHub stars) and built-in RBAC. Drawback: monitoring, playground, and custom evaluators gated behind paid tier; requires ClickHouse + Redis infrastructure overhead.

Braintrust — Clean REST API with custom evaluators and basic annotation queues. Drawback: no real-time monitoring capabilities; performance issues with large dataset uploads.

LangSmith — Deep LangChain integration with datasets and basic prompt evaluation. Drawback: closed source with self-hosting restricted to Enterprise tier; limited to LangChain ecosystem; past security vulnerabilities.

Datadog LLM Observability — Comprehensive APM integration with existing Datadog infrastructure. Drawback: lacks prompt playground, custom evaluators, and agent-specific analytics; primarily metrics-focused.

MLflow GenAI — Apache-2 licensed with experiment tracking and code-based evaluations. Drawback: notebook-based interface; no real-time monitoring or production alerting capabilities.

Galileo (Luna) — Specialized in data quality with SLM evaluators and annotation workflows. Drawback: limited to data quality use cases; no comprehensive LLM observability features.

Fiddler — Enterprise-focused with custom monitoring rules and compliance features. Drawback: primarily designed for traditional ML; limited LLM-specific capabilities.

Build Your Own — Complete control over features and infrastructure. Drawback: significant development overhead; requires ongoing maintenance and expertise.

LangSmith Alternative FAQs – Pricing, Features, Migration

What is LangSmith?

A closed‑source LLM debugging & evaluation SaaS created by the LangChain team; it focuses on LangChain workflows and offers basic tracing, datasets and prompt evaluations.

Is LangSmith open‑source?

No. Source code is proprietary; self‑hosting is gated behind the Enterprise plan.

Does LangSmith support self‑hosting?

Yes, but only on the Enterprise tier—making it inaccessible for most trials or early‑stage teams.

How much does LangSmith cost?

Published SaaS pricing starts around $39 per user / month; on‑prem quotes are negotiated.

Which LangSmith alternative is open‑source and free?

Arize Phoenix (Elastic 2.0) and LangFuse (MIT) are the two OSS options; Phoenix bundles monitors and playground features that LangFuse paywalls.

What security issues have affected LangSmith?

In 2025 the “AgentSmith” vulnerability (CVSS 8.8) exposed OpenAI keys via malicious agents before being patched.

Which alternative is OTEL‑native out‑of‑the‑box?

Arize Phoenix and Arize AX; LangFuse requires an adapter and LangSmith limits OTEL to LangChain spans.

Is Arize Phoenix really free in production?

Yes—unlimited event volumes under the Apache‑2 licence, including monitors, evaluators and the prompt playground.

Arize AX vs Phoenix – what’s the difference?

Phoenix = self‑hosted OSS core. AX = managed service with petabyte OLAP backend, custom dashboards, Copilot insights, RBAC, HIPAA and a 99.9 % SLA.

Can I migrate from LangSmith to Phoenix/AX?

Yes. Export LangSmith traces via OTEL and forward them to Phoenix; moving from Phoenix to AX is a one‑line config change.

Does Datadog offer LangSmith‑like LLM observability?

Its 2024 module tracks basic metrics but lacks prompt playgrounds, custom evaluators or agent graphs—so teams often pair it with Phoenix or AX for depth.

Which alternative scales best for enterprise workloads?

Arize AX ingests billions of spans per day for customers such as AT&T and Pepsi; Phoenix uses the same instrumentation path for easy upgrade when scale hits.

What are the best LangSmith alternatives for open source?

Arize Phoenix (Apache-2) and LangFuse (MIT) are the main open-source options. Phoenix offers more features including monitoring, custom evaluators, and agent trajectory analysis that LangFuse paywalls.

How do LangSmith alternatives compare for enterprise use?

Arize AX leads with petabyte-scale OLAP, SOC-2/HIPAA compliance, and dedicated enterprise support. Datadog offers APM integration but lacks LLM-specific features. Most others have limited enterprise capabilities.

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