Agent Harness Loop Contract

#Learning Objectives

• Specify an agent harness loop as a deterministic state machine with explicit transitions.
• Implement ten lifecycle hook topics that operators wire policy, telemetry, and guardrails into.
• Define two pull points where the loop yields control back to the caller and resumes on a fresh input.
• Enforce per-session budgets (turns, tool calls, wall-clock) without leaking partial state on exceeding.
• Emit a typed stream of eleven event types so downstream UIs and tracers can subscribe without inspecting the loop directly.