Routing and Conditional Chains
Build chains that dynamically pick a path based on input, sending each request to the most appropriate sub-chain for smarter, branching workflows.
Routing and Conditional Chains is a free AI Agents with LangChain & Autonomous Workflows lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the AI Agents with LangChain & Autonomous Workflows learning path, and your progress syncs across the web and the CoddyKit app. The AI Agents with LangChain & Autonomous Workflows course includes 4 lessons in total.
Beyond Straight-Line Chains
Sequential chains always run the same steps in order. But real workflows branch: a billing question and a coding question need different handling.
This lesson covers routing chains that choose a path based on the input.
What a Router Does
A router inspects the input, decides which destination chain best fits, and forwards the input there. It is a dispatcher in front of several specialist chains.
input -> router -> { billing_chain | code_chain | general_chain }Defining Destination Chains
Each destination is a normal chain tuned for one kind of task, with its own prompt and configuration.
billing = LLMChain(llm=llm, prompt=billing_prompt)
coding = LLMChain(llm=llm, prompt=coding_prompt)Describing Each Route
The router needs to know what each destination is for. Provide a name and a short description so it can match an input to the right one.
routes = [
{'name': 'billing', 'description': 'invoices, refunds, payments'},
{'name': 'coding', 'description': 'programming and debugging help'}
]LLM-Based Routing
One approach asks the LLM itself to classify the input and name the destination. It is flexible and handles fuzzy intent, but adds a model call and some unpredictability.
# router prompt asks model to output: {'destination': 'billing', 'input': ...}Rule-Based Routing
When intent is clear from structure, a deterministic function can route faster and cheaper than an LLM.
def route(query):
if 'refund' in query.lower():
return 'billing'
return 'general'The Default Route
Some inputs match no specialist. Always provide a default destination so the chain never fails on an unexpected request.
default_chain = LLMChain(llm=llm, prompt=general_prompt)Composing the Router Chain
LangChain's routing chain ties the router, the destination map, and the default together into a single callable that picks the path automatically.
from langchain.chains.router import MultiPromptChain
chain = MultiPromptChain(
router_chain=router,
destination_chains={'billing': billing, 'coding': coding},
default_chain=default_chain)Handling Misroutes
Routing is a prediction and can be wrong. Log the chosen destination, let a destination decline and fall back, and monitor misroute rates so you can refine descriptions over time.
LLM vs Rule-Based Tradeoffs
Choose your router by the situation:
- Rules: fast, cheap, deterministic; brittle for fuzzy intent
- LLM: flexible, handles nuance; slower, costs a call, less predictable
Hybrids use rules first and fall back to the LLM.
A Routing Workflow
Putting it together:
- Build specialist destination chains
- Describe each route clearly
- Choose rule-based, LLM-based, or hybrid routing
- Always include a default and monitor misroutes
Quick Check
Test your understanding of routing chains.
Recap
You learned to build branching, conditional chains.
- A router dispatches input to specialist destination chains
- Routing can be rule-based, LLM-based, or hybrid
- Clear route descriptions improve accuracy
- Always include a default and monitor misroutes
Frequently Asked Questions
Is the “Routing and Conditional Chains” lesson free?
Yes — the full text of “Routing and Conditional Chains” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the AI Agents with LangChain & Autonomous Workflows course, upgrade to CoddyKit PRO. The AI Agents with LangChain & Autonomous Workflows course includes 4 lessons in total.
What will I learn in “Routing and Conditional Chains”?
Build chains that dynamically pick a path based on input, sending each request to the most appropriate sub-chain for smarter, branching workflows. You practise AI Agents with LangChain & Autonomous Workflows with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start AI Agents with LangChain & Autonomous Workflows?
No prior experience is required. AI Agents with LangChain & Autonomous Workflows on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.
How long does the “Routing and Conditional Chains” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this AI Agents with LangChain & Autonomous Workflows lesson?
Yes. Every AI Agents with LangChain & Autonomous Workflows lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Introduction to LangChain Chains
- Sequential & Simple Chains
- Customizing Chain Logic
- Routing and Conditional Chains