Langchain Chains

---
name: langchain-chains
description: LangChain chain composition including SequentialChain, RouterChain, and LCEL patterns
allowed-tools:
  - Read
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graph:
  domains: [domain:software-engineering]
  specializations: [specialization:ai-agents-conversational]
  skillAreas: [skill-area:chain-of-thought-multistep-orchestration, skill-area:tool-service-integration-agents]
  roles: [role:ml-engineer, role:backend-engineer]
  workflows: [workflow:feature-development, workflow:ml-model-lifecycle]
  topics: [topic:design-patterns]

---

# LangChain Chains Skill

## Capabilities

- Compose LangChain chains using LCEL (LangChain Expression Language)
- Implement sequential chain patterns
- Design router chains for conditional logic
- Create parallel execution chains
- Handle chain fallbacks and retries
- Implement streaming chains

## Target Processes

- dialogue-flow-design
- chatbot-design-implementation

## Implementation Details

### Chain Patterns

1. **LCEL Pipelines**: Modern composition with | operator
2. **SequentialChain**: Linear chain execution (legacy)
3. **RouterChain**: Conditional routing based on input
4. **RunnableParallel**: Parallel execution branches
5. **RunnableBranch**: Conditional branching

### Configuration Options

- Input/output key mapping
- Error handling strategies
- Retry configuration
- Streaming settings
- Batch processing options

### Best Practices

- Use LCEL for new implementations
- Implement proper input/output schemas
- Add fallback chains for resilience
- Use streaming for long operations

### Dependencies

- langchain-core
- langchain