fix(reconcile): retire workflow session rows whose owners are no longer live

Implement a sanctioned session lifecycle for post-restart reconciliation so
active session rows with dead or reused owner PIDs can be terminalized
without deleting history. Protect live owners, live leases, and live
client-managed sessions; record durable session_retired audit events; keep
cleanup idempotent under concurrent reconciles.

Closes #969

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

post_restart_reconcile.py

@@ -475,24 +475,65 @@ def reconcile_after_restart(
             )
         )
 
-    # --- sessions -------------------------------------------------------
+    # --- sessions (#969: dead-owner / PID-reuse lifecycle) ---------------
+    # Prefer a precomputed fleet report from the gather/apply path when present;
+    # otherwise classify pure from inventory (injectable checkers stay default).
     sessions = [s for s in (inventory.get("sessions") or []) if isinstance(s, Mapping)]
-    orphan_sessions = [
-        s
-        for s in sessions
-        if str(s.get("status") or "").lower() == "active"
-        and s.get("pid") is not None
-        and not lease_lifecycle.is_process_alive(s.get("pid"))
+    leases_for_sessions = [
+        L for L in (inventory.get("leases") or []) if isinstance(L, Mapping)
     ]
-    if orphan_sessions:
+    fleet_report = inventory.get("session_fleet")
+    if isinstance(fleet_report, Mapping) and "retireable_session_ids" in fleet_report:
+        fleet_details = dict(fleet_report)
+        retireable_ids = list(fleet_details.get("retireable_session_ids") or [])
+        resolved = bool(fleet_details.get("sessions_dimension_resolved", not retireable_ids))
+    else:
+        try:
+            import session_lifecycle as _sl
+
+            client_managed = inventory.get("client_managed_session_ids")
+            cm_set = None
+            if isinstance(client_managed, (list, tuple, set, frozenset)):
+                cm_set = {str(x) for x in client_managed}
+            fleet = _sl.classify_sessions(
+                sessions,
+                leases=leases_for_sessions,
+                now=started,
+                client_managed_sessions=cm_set,
+            )
+            fleet_details = fleet.as_dict()
+            retireable_ids = list(fleet_details.get("retireable_session_ids") or [])
+            resolved = bool(fleet_details.get("sessions_dimension_resolved"))
+        except Exception as exc:  # noqa: BLE001 — fail closed to legacy signal
+            # Legacy fallback: dead-pid active rows only (pre-#969 behaviour).
+            orphan_sessions = [
+                s
+                for s in sessions
+                if str(s.get("status") or "").lower() == "active"
+                and s.get("pid") is not None
+                and not lease_lifecycle.is_process_alive(s.get("pid"))
+            ]
+            retireable_ids = [s.get("session_id") for s in orphan_sessions]
+            resolved = not orphan_sessions
+            fleet_details = {
+                "total_sessions": len(sessions),
+                "retireable_session_ids": retireable_ids,
+                "legacy_fallback": True,
+                "fallback_error": str(exc),
+            }
+
+    if not resolved and retireable_ids:
         items.append(
             _item(
                 DIM_SESSIONS,
                 ITEM_UNRESOLVED,
-                f"{len(orphan_sessions)} active session row(s) with dead owner pid",
+                f"{len(retireable_ids)} session row(s) with dead/reused owner "
+                f"await retirement",
                 details={
-                    "orphan_session_ids": [s.get("session_id") for s in orphan_sessions],
+                    "orphan_session_ids": retireable_ids,
+                    "retireable_session_ids": retireable_ids,
                     "total_sessions": len(sessions),
+                    "fleet": fleet_details,
                 },
                 follow_up=True,
             )
@@ -502,8 +543,12 @@ def reconcile_after_restart(
             _item(
                 DIM_SESSIONS,
                 ITEM_RESOLVED,
-                f"{len(sessions)} session row(s) reconciled (no dead-pid orphans)",
-                details={"total_sessions": len(sessions)},
+                f"{len(sessions)} session row(s) reconciled "
+                f"(no retireable dead/reused owners)",
+                details={
+                    "total_sessions": len(sessions),
+                    "fleet": fleet_details,
+                },
             )
         )