LangChain

The framework most LLM applications are still assembled with.

AIOpen source

About LangChain

LangChain is a set of developer tools for building applications on large language models and then watching how those applications behave once they are running. Two pieces do most of the work. LangGraph is the framework, released under the MIT licence and free to use. LangSmith is the hosted service for tracing, evaluation and monitoring, and it is what the pricing pages describe.

LangGraph ships built in memory that persists conversation history, human in the loop approval steps, and token by token streaming. Those are the three parts of an agent that are tedious to build by hand: remembering earlier turns, pausing so a person can approve an action before it happens, and returning output as it is produced rather than all at once.

LangSmith records what a run actually did. Tracing SDKs cover Python, TypeScript, Go and Java, and the service ingests OpenTelemetry traces and works with the OpenAI SDK, the Anthropic SDK, the Vercel AI SDK and LlamaIndex, so it is not restricted to applications built with LangGraph. Tracing runs through an asynchronous callback handler and adds no latency to the traced application. Alerts can be raised through webhooks or PagerDuty.

The Developer plan is free but capped at one seat, and includes 5,000 base traces a month before pay as you go charges begin. Plus is $39 per seat per month with no cap on seat count, 10,000 base traces a month and one free small serverless deployment. Base traces are retained for 14 days, and traces upgraded to extended retention are kept for 400 days. Usage past the allowances is metered: a compute unit costs $1.50 and a storage unit costs $1.00, deployments beyond the included one bill on vCPU hours and GiB hours, and tuned evaluators cost $0.01 in compute units per evaluation run on Plus.

Enterprise is custom priced and billed on an annual invoice, adding custom single sign on, attribute based and role based access control, an SLA and a named support team. It is also where deployment opens up. LangSmith can run self hosted on a customer's own Kubernetes cluster, hybrid, or on the vendor's cloud, and the bring your own cloud option supports AWS, GCP and Azure. The managed cloud stores data in the GCP us-central-1 region, which matters if there are residency requirements to satisfy. LangChain states that it does not train on customer data.

Key features

Releases LangGraph under the MIT licence, free to use.
Persists conversation history, adds human in the loop approval steps and streams token by token.
Traces through an asynchronous callback handler, adding no latency to the traced application.
Provides tracing SDKs for Python, TypeScript, Go and Java.
Ingests OpenTelemetry traces and works with the OpenAI, Anthropic and Vercel AI SDKs and LlamaIndex.
Raises alerts through webhooks and PagerDuty.
Retains base traces for 14 days, or 400 days when upgraded to extended retention.
Includes 5,000 base traces per month on the free Developer plan and 10,000 on Plus at $39 per seat.
Runs LangSmith self hosted on a customer's Kubernetes cluster, hybrid, or on the vendor cloud.
Supports bring your own cloud on AWS, GCP and Azure, with managed data held in GCP us-central-1.
Includes one free small serverless deployment on Plus, billing extra ones on vCPU and GiB hours.
Prices compute units at $1.50, storage units at $1.00 and tuned evaluators at $0.01 per run.
Adds custom single sign on, role and attribute based access control, an SLA and named support.
States that it does not train on customer data.

What people use it for

Adding an approval step so a person signs off before an agent takes an irreversible action.
Tracing a production agent without adding latency to the user-facing request.
Keeping traces from an incident for 400 days by upgrading them to extended retention.
Running LangSmith on your own Kubernetes cluster when traces cannot leave the network.
Paging an on-call engineer through PagerDuty when an agent starts failing.
Instrumenting an app built on the OpenAI SDK without moving it onto a new framework.
Starting on the free Developer plan and moving to Plus when a second seat is needed.

Key facts about LangChain
Category	AI
Pricing	Open source
Free tier	Yes
Upvotes	18
Listed	22 August 2026

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