Agent Harness vs Agent Framework vs MCP: Which Layer Owns the Loop, State, Tools, Permissions, and Recovery
MarkTechPost Michal Sutter
Harnesses, agent frameworks, and MCP are separated as distinct layers in agent architecture, each owning different responsibilities in the execution stack. MCP became stateless in the 2026-07-28 update, while the article attributes no execution loop or agent state ownership to MCP and places tool-call contracts and transport there instead. As a result, developers choose whether they get a fixed loop and permissions from a harness, compose a loop from a framework, and then rely on MCP only for standardized tool/resource/prompt calls and elicitation.
Why it matters
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.