Training data is 6-12 months stale. For fast-moving libs (Next.js, React, Tailwind), paste the relevant docs section into context before asking for code. Tools like Context7 MCP do this automatically. Once a quarter, ask the model: "What's the current best practice for X in [library] version [Y]?" and verify against official docs.
I'm using [library] version [X]. Before writing any code, tell me the current, non-deprecated API for [task] in that version. If you're not confident your training is current, say so and ask me to paste the relevant docs. Don't use any API that's deprecated or removed in [X].