reopen: act on drb-correlation-review of e972cac

- only a substantive call after the close reopens a timer-closed incident;
  a thin "10-4" (doesn't refresh updated_at) or a sweep link of a call from
  before the close rides along without reopening — otherwise the next
  sweep closed it again and the portal flickered.
- substantive_call_count counts a call once, not once per scene.
- a timer-closed incident is never adopted as a cross-system parent.

Replay e972cac (correlation-only on 731b54b's extraction) vs the 09-22
answer key: pairwise F1 0.548 -> 0.807 (precision 0.839 -> 0.956, recall
0.407 -> 0.698); the bridge MVA is one 76-call incident instead of two
40-call halves. server-26#170.

c2-core: 468 pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-c2-core/app/internal/incident_correlator.py

@@ -224,6 +224,16 @@ def _normalize_unit(unit: str) -> str:
     return key or unit.strip().lower()
 
 
+def _after_close(inc: dict, now: datetime) -> bool:
+    try:
+        closed = datetime.fromisoformat(str(inc.get("resolved_at") or "").replace("Z", "+00:00"))
+    except ValueError:
+        return True
+    if closed.tzinfo is None:
+        closed = closed.replace(tzinfo=timezone.utc)
+    return now > closed
+
+
 def _is_trackable_unit(unit: str) -> bool:
     """
     Whether a unit is concrete enough to hold an incident open until it clears.
@@ -2029,7 +2039,8 @@ async def _update_incident(
     incident_id = inc["incident_id"]
 
     call_ids = list(inc.get("call_ids") or [])
-    if call_id not in call_ids:
+    is_new_call = call_id not in call_ids
+    if is_new_call:
         call_ids.append(call_id)
 
     talkgroup_ids = list(inc.get("talkgroup_ids") or [])
@@ -2101,6 +2112,7 @@ async def _update_incident(
     # thin traffic rides along without extending its life.
     if refresh_activity:
         updates["updated_at"] = _floor_at_started_at(inc, now).isoformat()
+        if is_new_call:  # a second scene of the same call is not a second call
             updates["substantive_call_count"] = (
                 inc.get("substantive_call_count")
                 if inc.get("substantive_call_count") is not None else len(inc.get("call_ids") or [])
@@ -2122,8 +2134,11 @@ async def _update_incident(
     # Signal-based auto-resolve: every tracked unit has cleared, none still active.
     # Requires at least one unit to have explicitly signalled back-in-service so we
     # don't fire on incidents where units were never tracked (no unit mentions at all).
-    if inc.get("status") == "resolved":
-        # A timer close was provisional and a related call just arrived.
+    if inc.get("status") == "resolved" and refresh_activity and _after_close(inc, now):
+        # A timer close was provisional and a related, substantive call arrived
+        # after it. A thin "10-4" rides along without reopening (it would not
+        # refresh updated_at, so the next sweep would just close it again),
+        # and neither does a sweep link of a call from before the close.
         updates.update({"status": "active", "resolved_at": None, "resolved_via": None,
                         "reopenable": False, "reopened_count": (inc.get("reopened_count") or 0) + 1})
         logger.info(f"Correlator: reopened timer-closed incident {incident_id} (call {call_id})")
@@ -2373,6 +2388,10 @@ async def _find_cross_system_parent(
     best_score = 0.0
 
     for inc in recent:
+        # A timer-closed incident is in `recent` only so a related call can
+        # reopen it; it must not be adopted as another agency's parent.
+        if inc.get("status") != "active":
+            continue
         # Only cross-system candidates
         if system_id in (inc.get("system_ids") or []):
             continue

drb-c2-core/tests/test_clearance_tracking.py

@@ -93,3 +93,9 @@ def test_thin_calls_do_not_fill_the_call_cap():
     assert ic._incident_at_capacity(inc, now) is None
     legacy = {k: v for k, v in inc.items() if k != "substantive_call_count"}
     assert ic._incident_at_capacity(legacy, now).startswith("call_cap")
+
+
+def test_reopen_only_for_a_call_after_the_close():
+    closed = {"resolved_at": "2026-09-22T15:00:00+00:00"}
+    assert ic._after_close(closed, datetime(2026, 9, 22, 15, 5, tzinfo=timezone.utc))
+    assert not ic._after_close(closed, datetime(2026, 9, 22, 14, 55, tzinfo=timezone.utc))