Which is the Best AI SEO Library for JavaScript in 2026?

My client wanted to switch LLM providers on a Friday afternoon. I lost a full day. I had an AI-powered SEO pipeline running smoothly — meta descriptions generating on-demand, title tags keyphrase-targeted, the whole thing humming along in a Next.js app. Then the client emailed: "Can we switch from OpenAI to Claude? Their pricing is better." Reasonable request. Should've been a 10-minute job. It wasn't. Because I'd built the pipeline on LangChain, and switching providers meant rewriting chain log