feat: explain RTC blockers when no R3 candidates are eligible

central/app/control_plane.py

@@ -340,6 +340,19 @@ def blocker_filter_summary(session, *, tenant_id=None, agent_id=None, product_co
     }
 
 
+def rtc_blocker_summary(session, agent_id: int) -> dict:
+    """Read-only, installation-scoped RTC blocker aggregates for the cClassTrib page."""
+    query = _blockers_query(session, agent_id=agent_id, field="RTC", status="OPEN", scope="all")
+    blockers = int(session.scalar(query.with_only_columns(func.count(BlockedProduct.id)).order_by(None)) or 0)
+    products = int(session.scalar(query.with_only_columns(func.count(func.distinct(BlockedProduct.product_code))).order_by(None)) or 0)
+    reason = func.coalesce(BlockedProduct.evidence_summary["reason"].as_string(), BlockedProduct.reason_code)
+    reasons = session.execute(
+        query.with_only_columns(reason, func.count(func.distinct(BlockedProduct.product_code)))
+        .group_by(reason).order_by(None)
+    ).all()
+    return {"open_blockers": blockers, "products_affected": products, "reason_counts": {str(code or ""): int(count) for code, count in reasons}}
+
+
 def _blocker_breakdown_query(query):
     """Group on the source column itself for PostgreSQL-safe SQL semantics."""
     return query.with_only_columns(BlockedProduct.field, func.count(BlockedProduct.id)).group_by(BlockedProduct.field).order_by(None)