langchain-migration-deep-dive

Migrate to LangChain from raw OpenAI SDK, LlamaIndex, or custom LLM code. Covers codebase assessment, side-by-side validation, RAG migration, agent migration, and feature-flagged gradual rollout. Trigger: "migrate to langchain", "langchain refactor", "legacy LLM migration", "replace openai SDK with langchain", "llamaindex to langchain".