diff --git a/backend/internal/service/ollama_cloud_usage.go b/backend/internal/service/ollama_cloud_usage.go
index 1de9574a7..d489ec172 100644
--- a/backend/internal/service/ollama_cloud_usage.go
+++ b/backend/internal/service/ollama_cloud_usage.go
@@ -196,6 +196,10 @@ func (s *SettingService) SetOllamaCloudUsageSettings(ctx context.Context, settin
 	if settings == nil {
 		return infraerrors.BadRequest("INVALID_OLLAMA_CLOUD_USAGE_SETTINGS", "settings cannot be nil")
 	}
+	if settings.DebounceMinutes == 0 {
+		// Legacy clients that omit debounce_minutes keep the fail-safe default.
+		settings.DebounceMinutes = ollamaCloudUsageDefaultDebounceMinutes
+	}
 	if settings.IntervalMinutes < ollamaCloudUsageMinIntervalMinutes || settings.IntervalMinutes > ollamaCloudUsageMaxIntervalMinutes {
 		return infraerrors.BadRequest(
 			"INVALID_OLLAMA_CLOUD_USAGE_INTERVAL",
diff --git a/backend/internal/service/ollama_cloud_usage_test.go b/backend/internal/service/ollama_cloud_usage_test.go
index da73639a7..9269e4f75 100644
--- a/backend/internal/service/ollama_cloud_usage_test.go
+++ b/backend/internal/service/ollama_cloud_usage_test.go
@@ -317,10 +317,14 @@ func TestOllamaCloudUsageSettingsDefaultOffAndValidation(t *testing.T) {
 
 	err = settingsService.SetOllamaCloudUsageSettings(context.Background(), &OllamaCloudUsageSettings{Enabled: true, IntervalMinutes: 14, DebounceMinutes: 1})
 	require.Error(t, err)
-	err = settingsService.SetOllamaCloudUsageSettings(context.Background(), &OllamaCloudUsageSettings{Enabled: true, IntervalMinutes: 90, DebounceMinutes: 0})
-	require.Error(t, err)
 	err = settingsService.SetOllamaCloudUsageSettings(context.Background(), &OllamaCloudUsageSettings{Enabled: true, IntervalMinutes: 90, DebounceMinutes: 61})
 	require.Error(t, err)
+	// DebounceMinutes=0 (legacy omit) defaults to 1 on write.
+	err = settingsService.SetOllamaCloudUsageSettings(context.Background(), &OllamaCloudUsageSettings{Enabled: true, IntervalMinutes: 90, DebounceMinutes: 0})
+	require.NoError(t, err)
+	settings, err = settingsService.GetOllamaCloudUsageSettings(context.Background())
+	require.NoError(t, err)
+	require.Equal(t, 1, settings.DebounceMinutes)
 	err = settingsService.SetOllamaCloudUsageSettings(context.Background(), &OllamaCloudUsageSettings{Enabled: true, IntervalMinutes: 90, DebounceMinutes: 2})
 	require.NoError(t, err)
 	settings, err = settingsService.GetOllamaCloudUsageSettings(context.Background())