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Best AI Agent Frameworks

The best AI agent framework for TypeScript and Next.js builders is the Vercel AI SDK; for Python, start with the OpenAI Agents SDK or Pydantic AI. Use the Claude Agent SDK to build agents that work with tools and files like Claude Code, and LangGraph when you need complex, stateful graphs with human-in-the-loop. All of these are free, open-source libraries; you pay only for model usage.

Libraries for building agents and AI apps. Prices last verified Oct 22, 2026.

Agent Frameworks rankings

#1
Vercel AI SDK
free
TypeScript toolkit for AI apps and agents.
Best for: TS/Next.js builders

Pricing: Free, open source

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#2
OpenAI Agents SDK
free
Lightweight framework for multi-agent workflows.
Best for: Simple agents on OpenAI models

Pricing: Free, open source (pay for model usage)

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#3
Claude Agent SDK
free
The agent harness behind Claude Code as an SDK.
Best for: Agents that use tools and files like Claude Code

Pricing: Free SDK (pay for Claude API usage)

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#4
LangGraph
free
Stateful, controllable agent orchestration.
Best for: Complex graphs with human-in-the-loop

Pricing: Free, open source (MIT); LangSmith platform is paid

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#5
Mastra
free
TypeScript agent framework with workflows and memory.
Best for: Full-featured TS agents

Pricing: Free, open source (Apache 2.0); enterprise features separately licensed

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#6
CrewAI
freemium
Framework for role-based multi-agent crews.
Best for: Multi-agent role-play pipelines

Pricing: Open-source framework; hosted platform free tier (50 executions/mo) + enterprise

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#7
Pydantic AI
free
Type-safe Python agent framework.
Best for: Python devs who love typing

Pricing: Free, open source

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#8
LlamaIndex
freemium
Framework for agents over your data.
Best for: RAG and document agents

Pricing: Open-source framework; LlamaCloud free plan (10K credits), Starter $50/mo

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