LangChain
LangChain is the most widely adopted framework for building applications powered by large language models. Since v1, the langchain package is deliberately small and agent-focused: create_agent is the standard way to build an agent, middleware customizes every step of the agent loop, and structured output is built in. Everything else (legacy chains, retrievers, the old AgentExecutor) moved to langchain-classic.
LangGraph Deep Dive
LangGraph is a framework for building stateful, multi-actor agent applications as directed graphs. Built on top of LangChain primitives, it gives you explicit control over agent control flow, state management, and human-in-the-loop interactions that a standard agent loop does not expose. LangChain's createagent is built on LangGraph, so you can start with createagent and middleware and drop to a custom StateGraph when the topology demands it.
CrewAI
CrewAI is a multi-agent orchestration framework built around the metaphor of a team ("crew") of specialized AI agents collaborating to accomplish complex tasks. Its role-based design makes it intuitive to set up and reason about, especially for workflows that mirror real-world team structures.
Microsoft Agent Framework
Verified against official documentation: 2026-10-12 (overview, workflows). Microsoft Agent Framework (MAF) is the documented successor path for both AutoGen and Semantic Kernel. Its overview describes it as combining AutoGen's simple single- and multi-agent abstractions with Semantic Kernel's enterprise features such as session-based state, type safety, middleware, and telemetry, plus graph-based workflows.
LlamaIndex Agents
LlamaIndex (formerly GPT Index) started as a data framework for connecting LLMs to external data sources. It has since evolved into a full agent framework with a distinctive strength: treating data retrieval pipelines as first-class agent tools. If your agent's primary job is to query, synthesize, and reason over complex data sources, LlamaIndex agents are purpose-built for that workflow.
OpenAI Responses and Agents SDK
Verified against official documentation the Responses API generates output and tool calls, the Conversations API stores conversation items, and the Agents SDK orchestrates an agent loop in your application. They are not interchangeable names for a hosted assistant.
Framework Comparison
Official documentation checked: 2026-10-12. Compare execution models and operational requirements, not unsupported numerical scores for community size or “production readiness.” The recommendations below are engineering judgments, not benchmark results. Provider support and feature parity depend on the language, adapter, model, and version you deploy.
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