LangChain
AI Engineer path · lesson 78 of 124Run a prompt→model→parser→tool chain, learn the LCEL pipe and the Runnable interface (invoke/stream/batch), tour the component toolbox, and see why loops push you to LangGraph.
{ text: "Good morning" }Key insight
A chain is composable links with a uniform interface — prompt builds the input, the model generates, the parser structures, the tool acts. Swappable and testable. But a straight chain can’t loop or branch; for that you graduate to LangGraph.
Build an LCEL chain
Order the pieces of a retrieval chain.
Tap a piece, then tap where it goes — or drag it. Tap the tray to take one back.
- 1Drop a step here
- 2Drop a step here
- 3Drop a step here
- 4Drop a step here
Test your knowledge
What does a LangChain chain compose?
The short version
A chain is a factory line: the prompt station preps the part, the model machines it, the parser inspects and boxes it, the tool ships it. Memory is the clipboard that remembers the last order.
Interview Questions
References & Further Reading
Related topics
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