What is a react (reasoning and acting)?

A popular prompting framework for AI agents that enables an LLM to synergistically generate reasoning traces and task-specific actions in an interleaved manner. The reasoning helps the model plan, while the actions allow it to interface with external tools to gather information.

Who uses one?

Developers building autonomous AI agents and workflows

What does it cost?

Pricing varies. The cheapest provider in our Top 11 starts around $—/mo. See the cheapest providers ranked.

How do I pick one?

Read the full methodology for our 9.4-point scoring framework, then look at the canonical 11 Best AI Agent Builder Platforms 2026 — LangChain, CrewAI & 9 Rivals Ranked, No Paid Listings. If you want a slice of the ranking by price, fit, or compliance, jump to: cheapest · highest-rated · fastest onboarding.

Source: Top 11 11 Best AI Agent Builder Platforms 2026 — LangChain, CrewAI & 9 Rivals Ranked, No Paid Listings, verified May 31, 2026.