LangSmith review

LangSmith comes second on the strength of its feature set. The observability page lists native tracing for agent frameworks and OpenTelemetry, SDKs for Python, TypeScript, Go and Java, message threading for multi-turn chats, online LLM-as-judge and code evals, trajectory monitoring and alerts through webhooks or PagerDuty. Insights clusters traces to show common behaviors and failure modes without manual tagging. The free Developer plan covers 1 seat and 5k base traces a month. Plus costs $39 per seat a month with 10k base traces, and extra traces are billed in LangChain Standard Units at 0.005 LSU each. The same account also covers agent deployment, sandboxes and an LLM gateway with cost controls and PII redaction. Value scores lower than Langfuse because seat pricing adds up for larger teams, and self-hosting needs an Enterprise contract.

Who it is for

teams building agents with LangChain or LangGraph

Price

Free Developer plan for 1 seat; Plus $39 per seat a month plus pay as you go.

Plus For teams building and deploying agents. $39 / seat per month
Quoted from the vendor pricing page on November 12, 2026.

Key features

• Native tracing for popular agent frameworks and OpenTelemetry, with SDKs for Python, TypeScript, Go and Java
• Online LLM-as-judge and code evals, plus tool and agent trajectory monitoring
• Webhook and PagerDuty alerts and cost tracking
• Insights that cluster traces to surface usage patterns and failure modes
• Cloud, hybrid or self-hosted deployment on Enterprise, with US or EU data location

Strengths and weaknesses

• Strength: Developer plan is free with 5k base traces a month
• Strength: Covers observability, evals, agent deployment and sandboxes under one account
• Strength: Startups backed by VCs can get up to $10,000 in credits
• Weakness: Plus is priced per seat at $39, so costs grow with team size
• Weakness: The free Developer plan is limited to 1 seat
• Weakness: Self-hosted and hybrid options are only on Enterprise

Key facts

• Free plan: Developer, 1 seat, 5k base traces a month
• Plus: $39 per seat a month, 10k base traces included
• Extra traces: 0.005 LSU per trace, at $1.00 per LSU
• Data location: US or EU cloud

Where it ranks

LangSmith is No. 2 in our Best LLM Observability Tools verdict.