<overview The LangChain ecosystem is split into focused, independently-versioned packages. Understanding which packages you need — and their version constraints — prevents incompatibilities and keeps upgrades predictable. Key principles: - LangChain 1.0 is the current LTS release. Always start new projects on 1.0+. LangChain 0.3 is legacy maintenance-only — do not use it for new work. - langchain-core is the shared foundation: always install it explicitly alongside any other package. - langchain-community (Python only) does NOT follow semantic versioning; pin it conservatively. - LangGraph vs…