LangChain — LangChain is the framework that powers most production LLM apps you've used. It's the plumbing behind the magic. What it provides: - Chains: Connect LLM calls with logic - Agents: LLMs that decide what actions to take - RAG: Retrieval-augmented generation made easy - Memory: Persistent context across conversations If you're building anything serious with LLMs, you'll probably touch LangChain. Python and JS/TS support. Huge ecosystem.

OpenAI Codex CLI — Codex CLI brings OpenAI's coding models directly to your terminal. It's the official CLI tool for developers who prefer shells over GUIs. Core capabilities: - Execute coding tasks from natural language - File system awareness and manipulation - Shell command generation and execution - Works with GPT-4 and GPT-4o models OpenAI's bet on agentic coding. Still early, but improving rapidly. Requires API credits.