Concepts/Concept

Application context

A payroll agent prepares a payment batch and reaches a protected commit node. Approval may arrive hours later. Ending the conversation and starting a new request would lose the exact plan node, action digest, parameter versions, and already completed side effects.

Definition

HITL Block and Resume represents human review as a durable runtime state. The task moves to waiting_for_approval, persists its checkpoint and Intent, then resumes the same node after a decision and precondition check.

Engineering mechanism

The approval request carries action summary, affected resources, risk, evidence, intent hash, expiry, and allowed decisions. Approval is append-only and single-use unless policy says otherwise. Resume reacquires leases, refreshes mutable state, confirms tool and policy versions, and checks idempotency before commit. Rejection, expiry, or changed preconditions follows an explicit transition.

Boundary

Narrative confirmation can continue a low-risk conversation. Runtime blocking is needed when the system must preserve execution identity across a wait point. Approval does not replace post-action verification or compensation.

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