Agent Harness Convergence Across All Platforms.

Anthropic, Vercel, Mastra, LangGraph, and OpenAI all shipped harness primitives simultaneously — external scaffolding managing persistent state, retry logic, and HITL checkpoints around stateless LLM inference. This isn't framework preference; it's architectural necessity. The mismatch between stateless inference and stateful tasks cannot be solved at the model layer. Phil Schmid