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 — 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, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
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, and the AI Agents with LangChain & Autonomous Workflows course includes 4 lessons in total. 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.
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; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
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