In the news
The best Python agent harnesses in 2026
Pydantic · Douwe Maan · Published · 3 min read
In 30 seconds
- What happened
- Pydantic released AI Harness, a library of 80+ composable capabilities for building Python agents with file tools, shells, planning, and durable execution.
- Why it matters
- Engineers building production agents need to choose a harness SDK that supports their model providers, execution environments, and approval workflows.
- Watch out
- Pydantic AI Harness is Python-only, library-based with no hosted runtime, and requires you to operate your own durability engine and sandbox infrastructure.
- agent
The patterns behind this
- Durable Execution & Checkpointing
- Agentic Context Engineering (Evolving Playbook)
- Skill Library (Voyager)
Each one covers how the technique works, when it earns its cost, and where it breaks.
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