Canonical LangGraph patterns for typed State, conditional routers, interrupt/resume, checkpointers, structured outputs, tool/MCP wiring, subgraphs, parallel branches, async streaming, and LangSmith tracing. Use when designing or implementing any LangGraph node, router, or graph. Reference; not a runbook.
Standard Python project setup using uv or conda + pip, src-layout, ruff (lint + format), mypy strict, pytest + pytest-asyncio, and pre-commit. Includes pyproject.toml, uv, and environment.yml templates, a GitHub Actions CI snippet, and LLM-friendly test patterns. Use when scaffolding a new project or upgrading…