0087: Terminal-session task lifecycle is historical

Status: accepted (2026-08-20) · Scope: product tier (core/events/v3, core/agents, commands/agents)

Context

V3 separates session authority from task lifecycle. A session.ended event proves that one generation stopped, while coord.lifecycle_changed records whether its task was active, blocked, or done. One task may continue in a later generation, so terminal session authority cannot complete the task by itself.

The first terminal coordination reader kept that separation in storage but not in its output. A trace could say session=ended and lifecycle=active without explaining that active was the last declaration from the finished generation. It also dated the task lifecycle with the generation’s last event, even when that event was the session terminal rather than a lifecycle transition.

Alternatives considered

Set every explicitly ended session to done. Rejected because it invents a task transition and prevents a task from continuing in a later generation.

Replace terminal task state with unknown. Rejected because the last declaration is valid historical evidence. Discarding it makes blocked and done generations indistinguishable when the ledger already preserves the difference.

Keep rendering the last value without qualification. Rejected because a bare active value reads as current work and can contradict authoritative session completion.

Decision

Agent command results carry task_state_scope: "current" | "historical". Authority-safe live rows returned by list, show, whoami, and status use current. Trace uses historical when it selects a terminal generation and renders the human label as lifecycle=historical(<last-state>).

The value remains the last recorded lifecycle declaration. Session completion does not emit or project a synthetic done. A merely waiting multi-turn task still has a live session and therefore keeps current scope.

The V3 safety reducer records the observed time of each task, lifecycle, and presence transition. Coordination views use the lifecycle transition time for task_state_updated_at; unrelated progress and session.ended no longer move that timestamp. The reducer build identifier advances to event-v3-safety-reducer-v2 so downstream projections can identify the new evidence fields.

Result

The agent-surface regression ends a generation whose last declared lifecycle is active. List omits it, show refuses it as non-live, and trace reports the session as ended with task_state: "active", task_state_scope: "historical", and the original lifecycle-transition timestamp. No done event is created.