diff --git a/go/clients/nodeengineclient/health.go b/go/clients/nodeengineclient/health.go
index b893d43..a5d3b56 100644
--- a/go/clients/nodeengineclient/health.go
+++ b/go/clients/nodeengineclient/health.go
@@ -13,6 +13,10 @@ import (
 // a module declares as the engine placed them (the state data, `<node>.<module>`): their layouts are the seat's contract
 // (seat.HealthByNodeValue, seat.DataByNodeModuleValue); this file is their codec, shared by the engine and its readers.
 
+// RootContract is the statement contract from which an engine judges an account's root: a report whose contract is lower
+// judged nothing about root, and a reader must not read its empty root verdicts as healthy (HealthByNodeValue.Contract).
+const RootContract = 3
+
 // EncodeHealth is h as JSON at the current version; it refuses a report naming no node, and a fall back to the old login
 // that names another node, no login fallen back from, no reason or no time.
 func EncodeHealth(h seat.HealthByNodeValue) ([]byte, error) {
diff --git a/go/clients/nodeengineclient/health_test.go b/go/clients/nodeengineclient/health_test.go
new file mode 100644
index 0000000..7dfdf28
--- /dev/null
+++ b/go/clients/nodeengineclient/health_test.go
@@ -0,0 +1,11 @@
+package nodeengineclient
+
+import "testing"
+
+// A report below RootContract judged nothing about root; the number is the one engines have written since the root
+// judgement began, so a change of it is a change of what a reader trusts.
+func TestRootContractIsTheOneEnginesJudgeRootFrom(t *testing.T) {
+	if RootContract != 3 {
+		t.Fatalf("RootContract = %d, the engines write 3", RootContract)
+	}
+}