Agent Harness vs Agent Framework vs MCP: Which Layer Owns the Loop, State, Tools, Permissions, and Recovery
Architecture explainer separates agent harnesses, frameworks, and MCP by which layer owns the loop, state, permissions, and recovery.
The article distinguishes agent harnesses (OpenAI Codex, Claude Agent SDK), which own the execution loop, sandbox, permission model, and recovery; frameworks (LangGraph, OpenAI Agents SDK, Microsoft Agent Framework), which supply composable primitives; and MCP, a stateless JSON-RPC wire protocol governed by the Linux Foundation's Agentic AI Foundation since December 2025. An ownership matrix maps the execution loop, state, tool transport, permissions, recovery, sandboxing, and multi-agent orchestration to each layer. The 2026-07-28 MCP specification made the protocol fully stateless, retiring the initialize handshake and session headers.
- Harnesses (Codex, Claude Agent SDK) own loop, permissions, sandbox, and recovery
- Frameworks (LangGraph, OpenAI Agents SDK) provide composable state and orchestration primitives
- MCP is a stateless JSON-RPC tool contract with no loop or agent state
- Microsoft Agent Framework reached 1.0 GA in April 2026
From the original article
11 min read at marktechpost.com
A practitioner's map of the 3 layers in a modern agent stack, with verified sources and an overlap analysis. The post Agent Harness vs Agent Framework vs MCP: Which Layer Owns the Loop, State, Tools, Permissions, and Recovery appeared first on MarkTechPost.
By Michal Sutter · marktechpost.com
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