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LangChain 101

A practical guide series for learning LangChain - prompts, models, retrieval, tools, and exactly where LangChain's job ends and LangGraph's begins. Written by people who build with it for a living.

Foundations → Practitioner · ~29 minutes total
| | input Prompt template Model any provider Parser output

LangChain's core pattern: pipe simple pieces together with | to build a chain.

FOUNDATIONS

Start Here

New to LangChain, or coming from the LangGraph guides and wondering how the two fit together? Start here.

What Is LangChain? (And How It Relates To LangGraph)

The toolbox versus the wiring diagram - what LangChain actually gives you, and exactly where it hands off to LangGraph.

Foundations 5 min read

Prompts, Models & Output Parsers

The three pieces you'll chain together in almost every LangChain project, and how LCEL's pipe syntax connects them.

Foundations 6 min read
HANDS-ON

Work With Real Data

Where LangChain earns its keep - connecting a model to documents it wasn't trained on.

Retrieval & RAG

Load, split, embed, store, retrieve - the five-stage pipeline behind every "chat with your documents" app.

Hands-On 7 min read

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ADVANCED

Tools, Agents & Memory

The two areas where LangChain's own guidance has shifted the most recently - worth getting the current picture, not an outdated one.

Tools & Tool-Calling Agents

Giving a model access to a tool, and the current, non-deprecated way to build an agent around that.

Advanced 6 min read

Memory in LangChain

Why the old memory classes are deprecated, and what to reach for instead in a project you're starting today.

Advanced 5 min read