langgraphjs/CLAUDE.md

LangGraphJS Development Guide

Build & Test Commands

• Build: pnpm build
• Lint: pnpm lint (fix with pnpm lint:fix) — uses oxlint
• Format: pnpm format (check with pnpm format:check) — uses oxfmt
• Test: pnpm test (single test: pnpm test:single /path/to/yourtest.test.ts)
• Integration tests: pnpm test:int (start deps: pnpm test:int:deps, stop: pnpm test:int:deps:down)

Code Style Guidelines

• TypeScript: Target ES2021, NodeNext modules, strict typing enabled
• Formatting: 2-space indentation, 80 char width, double quotes, semicolons required
• Naming: camelCase (variables/functions), CamelCase (classes), UPPER_CASE (constants)
• Files: lowercase .ts, tests use .test.ts or .int.test.ts for integration
• Error Handling: Custom error classes that extend BaseLangGraphError
• Imports: ES modules with file extensions, order: external deps → internal modules → types
• Project Structure: Monorepo with pnpm workspaces, libs/ for packages, examples/ for demos
• New Features: Match patterns of existing code, ensure proper testing, discuss major abstractions in issues

Library Architecture

System Layers

• Channels Layer: Base communication & state management (BaseChannel, LastValue, Topic)
• Checkpointer Layer: Persistence and state serialization across backends
• Pregel Layer: Message passing execution engine with superstep-based computation
• Graph Layer: High-level APIs for workflow definition (Graph, StateGraph)

Key Dependencies

• Channels provide state management primitives used by Pregel nodes
• Checkpointer enables persistence, serialization, and time-travel debugging
• Pregel implements the execution engine using channels for communication
• Graph builds on Pregel adding workflow semantics and node/edge definitions
• StateGraph extends Graph with shared state management capabilities