路由与条件链
构建能够根据输入动态选择路径的链，将每个请求发送到最合适的子链，从而实现更智能的分支式工作流。
路由与条件链 是 CoddyKit 上的免费 AI Agents with LangChain & Autonomous Workflows 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 AI Agents with LangChain & Autonomous Workflows 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 AI Agents with LangChain & Autonomous Workflows 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
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
常见问题解答
「路由与条件链」课时是免费的吗？
是的 — 「路由与条件链」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 AI Agents with LangChain & Autonomous Workflows 课程的其余内容，请升级到 CoddyKit PRO。 AI Agents with LangChain & Autonomous Workflows 课程共包含 4 节课。
「路由与条件链」这节课中我会学到什么？
构建能够根据输入动态选择路径的链，将每个请求发送到最合适的子链，从而实现更智能的分支式工作流。 你通过在浏览器中直接运行的动手代码来练习 AI Agents with LangChain & Autonomous Workflows，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 AI Agents with LangChain & Autonomous Workflows 需要有经验吗？
无需任何先前经验。CoddyKit 上的 AI Agents with LangChain & Autonomous Workflows 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「路由与条件链」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 AI Agents with LangChain & Autonomous Workflows 课中编写并运行代码吗？
能。每节 AI Agents with LangChain & Autonomous Workflows 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。