Topic
LangChain Expression Language (LCEL) Chains
13 posts on langchain expression language (lcel) chains — part of framework tutorials on the n4n AI blog.
Parallel execution in LangChain using LCEL
Learn to run independent LCEL chains in parallel using RunnableParallel, RunnablePassthrough, and async patterns to cut latency in production LangChain applications.
LCEL RunnableLambda: adding custom functions to chains
Learn to wrap custom Python functions as LCEL RunnableLambda components for composable, streaming-capable LangChain pipelines.
Debugging LCEL chains with LangSmith tracing
Learn to debug LangChain Expression Language chains using LangSmith tracing with step-by-step setup, runnable code, and verification techniques.
Migrating legacy LangChain chains to LCEL
Step-by-step guide to migrating legacy LangChain chains to LCEL with runnable code examples and verification strategies.
LCEL RunnableParallel for multi-step LangChain pipelines
Build multi-step LangChain pipelines with LCEL RunnableParallel — parallel branches, shared state, error handling, and verification steps.
LCEL RunnableBranch: conditional logic in chains
LCEL RunnableBranch lets you route inputs to different chains based on conditions — here's how it works, when to use it, and a production-ready example.
Error handling and fallbacks in LCEL chains
Practical guide to implementing robust error handling, retries, and fallback strategies in LangChain Expression Language chains for production LLM applications.
LCEL with n4n.ai: routing between GPT-4o and Llama 3.3
Step-by-step guide to implementing lcel n4n.ai model routing gpt-4o llama with LangChain Expression Language for cost-efficient and resilient LLM inference.
LCEL pipe syntax explained with real examples
LCEL pipe syntax explained: how LangChain's | operator composes runnables into chains, with working Python examples, debugging tips, and fixes for common mistakes.
LangChain Expression Language: a beginner's guide
A practical langchain expression language beginner guide: build composable LLM chains with LCEL, avoid common pitfalls, and ship faster.
Composing prompt, model, and parser with LCEL
Learn how to lcel compose prompt model parser into a single runnable LangChain chain with code, deployment notes, and verification steps for engineers.
Building a RAG chain entirely in LCEL
Step-by-step lcel rag chain tutorial: load docs, embed with FAISS, and compose retrieval and generation into one LangChain Expression Language chain. Runnable code included.
Build your first LCEL chain in LangChain
Hands-on tutorial to build first LCEL chain LangChain with runnable Python code: install, prompt, model, parser, stream, fallback, and verify.
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