LangChain

★ 5/5 · Infrastructure/Database

LangChain is the leading open-source framework for LLM apps and agents (Python/JS), with LangSmith for tracing/evals/deploy. The library is OSS; LangSmith is the paid control plane.

Pros

Default agent framework. LangGraph for stateful agents. Official LangSmith: Developer $0/seat (5k traces then PAYG), Plus $39/seat/mo (10k traces), Enterprise custom — langchain.com/pricing. LCU $1.50 / LSU $1.00 as printed there.

Cons

Framework changes quickly
you still bring model API keys. LangSmith pay-as-you-go can add up with trace volume. LangChain open source and LangSmith are separate products.

Cost

LangChain open source is free. LangSmith on langchain.com/pricing: Developer $0/seat per month then pay-as-you-go traces; Plus $39/seat per month; Enterprise custom. 1 LCU = $1.50; 1 LSU = $1.00.

Verdict

Default building block for LLM apps, not a consumer chat app.

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