Best PydanticAI Alternatives in 2026

smolagents is Hugging Face's open-source Python library for building AI agents that write code as actions rather than JSON tool calls. Apache 2.0, ~1,000 lines of core code, supports 100-plus LLMs including local models via Ollama and Transformers.

OpenAI's official open-source framework for multi-agent workflows. Launched March 2025 as the production successor to Swarm. Provides handoffs, guardrails, tracing, and voice agent support in Python and TypeScript.

Genkit is Google's open-source AI framework for TypeScript, Go, and Python developers. It provides typed flows, RAG, tool calling, and multi-agent support with a standout local Developer UI for iterating prompts and debugging traces. Free under Apache 2.0.

Agno is an open-source Python framework for building multi-agent AI systems, rebranded from Phidata in January 2025. Model-agnostic, Apache 2.0, with built-in memory, knowledge bases, and a production-ready AgentOS runtime for deploying agents as services.

Vercel AI SDK is an open-source TypeScript toolkit for building AI-powered applications and agents. It provides a unified API across 20+ model providers, streaming UI hooks for React and Vue, structured output with Zod, and a full agent abstraction layer.

Mastra is an open-source TypeScript framework for building production AI agents, from the team behind Gatsby. It ships agents, durable workflows, RAG, built-in memory with SOTA LongMemEval scores, and a visual debugging studio.

DSPy is a Stanford NLP framework that treats prompt engineering as a compiler problem: you write typed signatures and modules, define a metric, and an optimizer searches for the best prompts automatically. Free, Apache 2.0, 5M+ monthly PyPI downloads.

Haystack is deepset's open-source Python framework for building production-ready RAG pipelines and AI agents. Apache 2.0 licensed, it gives developers explicit control over retrieval, context routing, and generation through composable, YAML-serializable pipeline graphs.

BentoML is an open-source Python framework for packaging and deploying machine learning models as production APIs. It supports any ML framework, includes OpenLLM for self-hosted LLM serving, and offers BentoCloud for managed inference with autoscaling and BYOC.

Stagehand is an MIT-licensed TypeScript SDK from Browserbase that adds natural-language browser control (act, extract, observe) on top of CDP, letting developers build browser agents that survive UI changes without selector maintenance.