diff --git a/go/core/internal/controller/reconciler.go b/go/core/internal/controller/reconciler.go
index 0a958b9875..82b5e19a98 100644
--- a/go/core/internal/controller/reconciler.go
+++ b/go/core/internal/controller/reconciler.go
@@ -540,26 +540,24 @@ func (r *Reconciler) reconcileModelConfigStatus(ctx context.Context, key string)
 }
 
 func statusWithTransitionTimes(desired, current kagentv1alpha3.AgentStatus) kagentv1alpha3.AgentStatus {
-	desired.Conditions = append([]metav1.Condition(nil), desired.Conditions...)
-	for i := range desired.Conditions {
-		condition := &desired.Conditions[i]
-		previous := apimeta.FindStatusCondition(current.Conditions, condition.Type)
-		if previous != nil && previous.Status == condition.Status {
-			condition.LastTransitionTime = previous.LastTransitionTime
-		} else {
-			condition.LastTransitionTime = metav1.Now()
-		}
-	}
+	desired.Conditions = conditionsWithTransitionTimes(desired.Conditions, current.Conditions)
 	return desired
 }
 
 func modelConfigStatusWithTransitionTimes(desired, current kagentv1alpha3.ModelConfigStatus) kagentv1alpha3.ModelConfigStatus {
-	desired.Conditions = append([]metav1.Condition(nil), desired.Conditions...)
-	for conditionIndex := range desired.Conditions {
-		condition := &desired.Conditions[conditionIndex]
-		if previous := apimeta.FindStatusCondition(current.Conditions, condition.Type); previous != nil &&
-			previous.Status == condition.Status && previous.Reason == condition.Reason &&
-			previous.Message == condition.Message && previous.ObservedGeneration == condition.ObservedGeneration {
+	desired.Conditions = conditionsWithTransitionTimes(desired.Conditions, current.Conditions)
+	return desired
+}
+
+// conditionsWithTransitionTimes keeps the transition time a condition's
+// status holds and stamps the current time when the status changes, as
+// apimeta.SetStatusCondition does; a new reason or message alone is no
+// transition.
+func conditionsWithTransitionTimes(desired, current []metav1.Condition) []metav1.Condition {
+	desired = append([]metav1.Condition(nil), desired...)
+	for conditionIndex := range desired {
+		condition := &desired[conditionIndex]
+		if previous := apimeta.FindStatusCondition(current, condition.Type); previous != nil && previous.Status == condition.Status {
 			condition.LastTransitionTime = previous.LastTransitionTime
 			continue
 		}
diff --git a/go/core/internal/controller/reconciler_test.go b/go/core/internal/controller/reconciler_test.go
index 669e3f44c3..5b135b01af 100644
--- a/go/core/internal/controller/reconciler_test.go
+++ b/go/core/internal/controller/reconciler_test.go
@@ -613,3 +613,21 @@ func reconciliationTestCard(name string) *a2apb.AgentCard {
 		SupportedInterfaces: []*a2apb.AgentInterface{{Url: "http://127.0.0.1:80", ProtocolBinding: "GRPC", ProtocolVersion: "1.0"}},
 	}
 }
+
+func TestModelConfigConditionTransitionTimesMoveOnlyOnStatusChange(t *testing.T) {
+	then := metav1.NewTime(time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC))
+	current := kagentv1alpha3.ModelConfigStatus{Conditions: []metav1.Condition{
+		{Type: "Accepted", Status: metav1.ConditionFalse, Reason: "SecretNotFound", Message: "secret team-a/a not found", ObservedGeneration: 1, LastTransitionTime: then},
+		{Type: "Ready", Status: metav1.ConditionTrue, Reason: "Resolved", ObservedGeneration: 1, LastTransitionTime: then},
+	}}
+	desired := kagentv1alpha3.ModelConfigStatus{Conditions: []metav1.Condition{
+		{Type: "Accepted", Status: metav1.ConditionFalse, Reason: "SecretKeyNotFound", Message: "key missing in secret team-a/b", ObservedGeneration: 2},
+		{Type: "Ready", Status: metav1.ConditionFalse, Reason: "Unresolved", ObservedGeneration: 2},
+	}}
+
+	got := modelConfigStatusWithTransitionTimes(desired, current)
+
+	require.Equal(t, then, got.Conditions[0].LastTransitionTime, "a new reason, message or generation alone is no transition")
+	require.True(t, got.Conditions[1].LastTransitionTime.After(then.Time), "a status change stamps a new transition time")
+	require.True(t, desired.Conditions[0].LastTransitionTime.IsZero(), "the desired conditions are not mutated")
+}