Agent Harnesses Become the Reliability Boundary

Recent architecture analysis clarifies that harnesses—not MCP or model frameworks alone—must own agent loops, state, permissions, recovery, verification, and handoffs. This is increasingly relevant to personal assistants because reliable execution depends on explicit checkpoints, approval gates, non-posting defaults, idempotency, and semantic evaluation rather than generic tool connectivity. The concept is technically important but still needs more concrete household and personal-productivity implementations.