fix: materialize stationary yutong daily mileage

2026-07-19 13:23:33 +08:00
parent dffe559160
commit 4da26ad3ba
7 changed files with 292 additions and 9 deletions
--- a/docs/ops/vehicle-ingest-runbook.md
+++ b/docs/ops/vehicle-ingest-runbook.md
@@ -339,7 +339,7 @@ export MYSQL_DSN="$(sed -n 's/^MYSQL_DSN=//p' /opt/lingniu-go-native/env/base.en
 | `vehicle_stat_samples_total{status="skipped_missing_fields"}` | 任意持续增长，或单 topic 可行动跳过数 / `vehicle_stat_writes_total{status="ok"}` 超过 `capacity-check -stat-sample-max-actionable-skip-ratio` | fields topic 收到了 envelope 但没有扁平化 `fields`。优先查 gateway `BuildFieldsEnvelope`、NATS/Kafka bridge topic 映射，以及是否误把 RAW envelope 写进 fields topic。 |
 | `vehicle_stat_samples_total{status="skipped_missing_vin"}` / `skipped_missing_mileage` / `skipped_non_positive_mileage` / `skipped_missing_source` | 单 topic 可行动跳过数 / `vehicle_stat_writes_total{status="ok"}` 超过 `capacity-check -stat-sample-max-actionable-skip-ratio` | fields topic 有消费但大量样本无法进入每日里程。按协议和跳过原因分别检查 VIN 映射、总里程字段映射、里程单位/异常值、`vehicle_data_source` 关联。 |
 | `vehicle_stat_samples_total{status="event_time_future_adjusted"}` | 连续增长或集中在某协议/source | 设备事件时间比接收时间未来超过 10 分钟，统计已回退到接收时间。优先检查上游平台或终端时钟；RAW 帧仍保留设备原始时间，业务 location、Redis 当前态和每日里程使用归一后的时间。 |
-| `vehicle_stat_samples_total{status="written"}` | stat-writer `ok` 增长但 `written` 不增长 | fields topic 有消费但没有有效里程样本入库，按 `skipped_missing_vin`、`skipped_missing_mileage`、`skipped_non_positive_mileage`、`skipped_missing_source`、`skipped_same_mileage` 定位原因；如果主要是 `skipped_same_mileage`，通常表示上游总里程未变化，不等同故障。 |
+| `vehicle_stat_samples_total{status="written"}` / `recovered_stationary` | stat-writer `ok` 增长但 `written` 不增长 | fields topic 有消费但没有有效里程样本入库，按 `skipped_missing_vin`、`skipped_missing_mileage`、`skipped_non_positive_mileage`、`skipped_missing_source`、`skipped_same_mileage` 定位原因；如果主要是 `skipped_same_mileage`，通常表示上游总里程未变化，不等同故障。`recovered_stationary` 表示宇通明确静止帧已用同来源历史仪表值生成 `0 km`，应与 `skipped_missing_mileage` 联合观察。 |
 | `vehicle_stat_sources_total{status="written"}` / `skipped_throttled` | `vehicle_stat_samples_total{status="found"}` 增长但 source tracking 无增长 | 来源管理链路没有维护 `vehicle_data_source`。优先查 source endpoint 是否为空、`vehicle_data_source` 表结构、MySQL 写入错误和 `STATS_SOURCE_TOUCH_INTERVAL_SECONDS`。 |
 | `vehicle_stat_sources_total{status="skipped_missing_endpoint"}` | 单 topic 缺 endpoint / found 超过 `capacity-check -stat-source-max-missing-ratio` | fields envelope 缺 `source_endpoint`，无法区分平台来源和维护 source。优先查 Gateway 是否填充 TCP remote/MQTT endpoint，以及 NATS/Kafka bridge 是否保留 envelope 字段。 |
 | `vehicle_stat_projections_total{status="written"}` / `skipped_throttled` | source 候选持续写入但最终日里程更新频率低 | `vehicle_daily_mileage_source` 是每样本候选事实层，`vehicle_daily_mileage` 是最终投影层。`skipped_throttled` 增长通常表示受 `STATS_PROJECT_INTERVAL_SECONDS` 节流，不代表样本丢失；如需强一致核验可临时设投影间隔为 `0`。 |
@@ -506,6 +506,8 @@ BACKFILL_DATE_TO=2026-07-12 \
 /opt/lingniu-go-native/current/stats-backfill
 ```

+宇通协议会把定位、车况和仪表里程拆成不同的稀疏帧。当天只有明确 `meter_speed=0` 的定位帧、但没有新的仪表总里程帧时，stat-writer 会用同一来源最近的历史总里程生成一条显式 `0 km` 记录，`quality_reason=stationary_carry_forward`；后续收到真实总里程后仍会正常覆盖增长。`vehicle_stat_samples_total{status="recovered_stationary"}` 用于观察该恢复路径。历史补录只能在轨迹核验确认为 `0 km` 后，临时为单次 `stats-backfill` 增加 `BACKFILL_STATIONARY_CARRY_FORWARD=true`；该开关默认关闭，禁止写入 timer，避免仅凭最新静止状态推断整日未行驶。
+
 生产定时补算使用 systemd timer，默认每天 01:30 补算昨天往前 3 天，覆盖上游晚到或断传后恢复的总里程字段：

 ```bash
--- a/go/vehicle-gateway/cmd/stat-writer/main.go
+++ b/go/vehicle-gateway/cmd/stat-writer/main.go
@@ -687,6 +687,7 @@ func recordStatSampleMetrics(registry *metrics.Registry, message kafka.Message,
 	addStatSampleMetric(registry, message, protocol, "skipped_missing_fields", result.SamplesSkippedMissingFields)
 	addStatSampleMetric(registry, message, protocol, "skipped_missing_vin", result.SamplesSkippedMissingVIN)
 	addStatSampleMetric(registry, message, protocol, "skipped_missing_mileage", result.SamplesSkippedMissingMileage)
+	addStatSampleMetric(registry, message, protocol, "recovered_stationary", result.SamplesRecoveredStationary)
 	addStatSampleMetric(registry, message, protocol, "skipped_non_mileage_frame", result.SamplesSkippedNonMileageFrame)
 	addStatSampleMetric(registry, message, protocol, "skipped_non_positive_mileage", result.SamplesSkippedNonPositiveMileage)
 	addStatSampleMetric(registry, message, protocol, "skipped_missing_time", result.SamplesSkippedMissingTime)
--- a/go/vehicle-gateway/cmd/stats-backfill/main.go
+++ b/go/vehicle-gateway/cmd/stats-backfill/main.go
@@ -35,6 +35,7 @@ type config struct {
 	Reset             bool
 	Debug             bool
 	EventTimeFullScan bool
+	StationaryCarry   bool
 	ProgressEvery     int64
 	BaselineLookback  int
 	Location          *time.Location
@@ -453,7 +454,8 @@ func addRealtimeLocationFallbackAggregates(ctx context.Context, mysqlDB *sql.DB,
 				return added, err
 			}
 			for vin, currentSources := range current {
-				for _, currentRow := range currentSources {
+				for i := range currentSources {
+					currentRow := currentSources[i]
 					key := vin + "|" + date + "|" + string(protocol) + "|" + currentRow.SourceKey
 					if _, exists := aggregates[key]; exists {
 						continue
@@ -462,8 +464,22 @@ func addRealtimeLocationFallbackAggregates(ctx context.Context, mysqlDB *sql.DB,
 					if err != nil {
 						return added, err
 					}
+					if cfg.StationaryCarry && !hasPrevious {
+						continue
+					}
+					if cfg.StationaryCarry {
+						// A sparse Yutong location frame can retain an older
+						// realtime odometer than the durable daily baseline.
+						// Stationary carry-forward represents an explicit zero
+						// day, so both ends must use the latest trusted baseline.
+						currentRow.FirstTotalKM = previousRow.TotalKM
+						currentRow.TotalKM = previousRow.TotalKM
+						currentSources[i] = currentRow
+					}
 					agg := aggregateFromDailySource(date, protocol, currentRow, previousRow, hasPrevious)
-					if hasPrevious {
+					if cfg.StationaryCarry {
+						agg.QualityReason = stats.QualityReasonStationaryCarry
+					} else if hasPrevious {
 						agg.QualityReason = "realtime_location_fallback_historical_baseline"
 					} else {
 						agg.QualityReason = "realtime_location_fallback_current_day_first_baseline"
@@ -716,15 +732,28 @@ func queryRealtimeLocationLastRows(ctx context.Context, db *sql.DB, cfg config,
 	if loc == nil {
 		loc = time.FixedZone("Asia/Shanghai", 8*3600)
 	}
-	sqlText := `SELECT l.vin, COALESCE(NULLIF(s.peer, ''), ''), l.total_mileage_event_time, l.total_mileage_km
+	eventTimeColumn := "l.total_mileage_event_time"
+	timePredicate := `l.total_mileage_event_time >= ?
+  AND l.total_mileage_event_time < DATE_ADD(?, INTERVAL 1 DAY)`
+	if cfg.StationaryCarry {
+		eventTimeColumn = "l.event_time"
+		timePredicate = `l.event_time >= ?
+  AND l.event_time < DATE_ADD(?, INTERVAL 1 DAY)
+  AND l.total_mileage_event_time < ?
+  AND COALESCE(l.speed_kmh, 0) = 0`
+	}
+	sqlText := `SELECT l.vin, COALESCE(NULLIF(s.peer, ''), ''), ` + eventTimeColumn + `, l.total_mileage_km
 FROM vehicle_realtime_location l
 LEFT JOIN vehicle_realtime_snapshot s ON s.protocol = l.protocol AND s.vin = l.vin
 WHERE l.protocol = ?
  AND l.vin IS NOT NULL AND l.vin <> ''
  AND l.total_mileage_km IS NOT NULL AND l.total_mileage_km > 0
-  AND l.total_mileage_event_time >= ?
-  AND l.total_mileage_event_time < DATE_ADD(?, INTERVAL 1 DAY)`
-	rows, err := db.QueryContext(ctx, sqlText, string(protocol), date, date)
+  AND ` + timePredicate
+	args := []any{string(protocol), date, date}
+	if cfg.StationaryCarry {
+		args = append(args, date)
+	}
+	rows, err := db.QueryContext(ctx, sqlText, args...)
 	if err != nil {
 		return nil, err
 	}
@@ -979,6 +1008,7 @@ func loadConfig() (config, error) {
 		Reset:             envBool("BACKFILL_RESET", false),
 		Debug:             envBool("BACKFILL_DEBUG", false),
 		EventTimeFullScan: envBool("BACKFILL_EVENT_TIME_FULL_SCAN", false),
+		StationaryCarry:   envBool("BACKFILL_STATIONARY_CARRY_FORWARD", false),
 		ProgressEvery:     int64(envInt("BACKFILL_PROGRESS_EVERY", 100000)),
 		BaselineLookback:  envInt("BACKFILL_BASELINE_LOOKBACK_DAYS", 7),
 		Location:          loc,
--- a/go/vehicle-gateway/cmd/stats-backfill/main_test.go
+++ b/go/vehicle-gateway/cmd/stats-backfill/main_test.go
@@ -323,6 +323,95 @@ func TestQueryRealtimeLocationLastRowsBuildsYutongSourceFromPeer(t *testing.T) {
 	}
 }

+func TestQueryRealtimeLocationLastRowsCanCarryStationaryYutongMileage(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New() error = %v", err)
+	}
+	defer db.Close()
+
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	currentEventTime := time.Date(2026, 7, 19, 6, 5, 42, 0, loc)
+	mock.ExpectQuery("(?s)SELECT.*l\\.event_time.*l\\.total_mileage_event_time < \\?.*COALESCE\\(l\\.speed_kmh, 0\\) = 0").
+		WithArgs("YUTONG_MQTT", "2026-07-19", "2026-07-19", "2026-07-19").
+		WillReturnRows(sqlmock.NewRows([]string{"vin", "peer", "event_time", "total_mileage_km"}).
+			AddRow("LMRKH9AC9R1004099", "mqtt://yutong/ytforward/shln/2", currentEventTime, 24245.0))
+
+	rows, err := queryRealtimeLocationLastRows(context.Background(), db, config{
+		Location:        loc,
+		StationaryCarry: true,
+	}, envelope.ProtocolYutongMQTT, "2026-07-19")
+	if err != nil {
+		t.Fatalf("queryRealtimeLocationLastRows() error = %v", err)
+	}
+	sourceRows := rows["LMRKH9AC9R1004099"]
+	if len(sourceRows) != 1 {
+		t.Fatalf("rows = %d, want 1", len(sourceRows))
+	}
+	if !sourceRows[0].TS.Equal(currentEventTime) || sourceRows[0].TotalKM != 24245 {
+		t.Fatalf("stationary carry row = %#v", sourceRows[0])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("sql expectations: %v", err)
+	}
+}
+
+func TestAddRealtimeLocationFallbackStationaryCarryUsesTrustedHistoricalBaseline(t *testing.T) {
+	mysqlDB, mysqlMock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("mysql sqlmock.New() error = %v", err)
+	}
+	defer mysqlDB.Close()
+	tdDB, tdMock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("td sqlmock.New() error = %v", err)
+	}
+	defer tdDB.Close()
+
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	vin := "LMRKH9AC5R1004133"
+	currentTS := time.Date(2026, 7, 19, 10, 20, 20, 0, loc)
+	previousTS := time.Date(2026, 7, 17, 8, 49, 55, 0, loc)
+	sourceKey := stats.SourceKeyForSource(envelope.ProtocolYutongMQTT, "", vin, "mqtt", "PLATFORM", "yutong")
+	mysqlMock.ExpectQuery("(?s)FROM vehicle_realtime_location l.*l\\.event_time.*l\\.total_mileage_event_time < \\?").
+		WithArgs("YUTONG_MQTT", "2026-07-19", "2026-07-19", "2026-07-19").
+		WillReturnRows(sqlmock.NewRows([]string{"vin", "peer", "event_time", "total_mileage_km"}).
+			AddRow(vin, "mqtt://yutong/ytforward/shln/4", currentTS, 55451.0))
+	mysqlMock.ExpectQuery("(?s)SELECT latest_total_mileage_km, latest_event_time.*FROM vehicle_daily_mileage_source").
+		WithArgs(vin, "2026-07-19", "YUTONG_MQTT", sourceKey).
+		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}).AddRow(55466.0, previousTS))
+
+	aggregates := map[string]*metricAgg{}
+	added, err := addRealtimeLocationFallbackAggregates(context.Background(), mysqlDB, tdDB, config{
+		TDengineDatabase: "lingniu_vehicle_ts",
+		DateFrom:         "2026-07-19",
+		DateTo:           "2026-07-19",
+		Protocols:        []envelope.Protocol{envelope.ProtocolYutongMQTT},
+		Location:         loc,
+		StationaryCarry:  true,
+	}, aggregates)
+	if err != nil {
+		t.Fatalf("addRealtimeLocationFallbackAggregates() error = %v", err)
+	}
+	if added != 1 || len(aggregates) != 1 {
+		t.Fatalf("added=%d aggregates=%d", added, len(aggregates))
+	}
+	for _, agg := range aggregates {
+		if agg.FirstKM != 55466 || agg.LatestKM != 55466 {
+			t.Fatalf("stationary km range = %v -> %v", agg.FirstKM, agg.LatestKM)
+		}
+		if agg.QualityStatus != stats.QualityOK || agg.QualityReason != stats.QualityReasonStationaryCarry {
+			t.Fatalf("quality = %s/%s", agg.QualityStatus, agg.QualityReason)
+		}
+	}
+	if err := mysqlMock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("mysql sql expectations: %v", err)
+	}
+	if err := tdMock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("td sql expectations: %v", err)
+	}
+}
+
 func TestAddRealtimeLocationFallbackAggregatesUsesHistoricalBaseline(t *testing.T) {
 	mysqlDB, mysqlMock, err := sqlmock.New()
 	if err != nil {
--- a/go/vehicle-gateway/internal/stats/daily_metric.go
+++ b/go/vehicle-gateway/internal/stats/daily_metric.go
@@ -69,6 +69,7 @@ type AppendResult struct {
 	SamplesSkippedMissingFields      int
 	SamplesSkippedMissingVIN         int
 	SamplesSkippedMissingMileage     int
+	SamplesRecoveredStationary       int
 	SamplesSkippedNonMileageFrame    int
 	SamplesSkippedNonPositiveMileage int
 	SamplesSkippedMissingTime        int
@@ -282,6 +283,19 @@ func (w *Writer) AppendWithResult(ctx context.Context, env envelope.FrameEnvelop
 	if err != nil {
 		return result, err
 	}
+	var stationaryCandidate *SourceMileageSample
+	if len(samples) == 0 && hasSource && result.SamplesSkippedMissingMileage > 0 {
+		sample, candidate, recovered, recoverErr := w.stationaryCarryForward(ctx, env, identity)
+		if recoverErr != nil {
+			return result, recoverErr
+		}
+		if recovered {
+			samples = []MetricSample{sample}
+			stationaryCandidate = &candidate
+			result.SamplesFound++
+			result.SamplesRecoveredStationary++
+		}
+	}
 	for _, sample := range samples {
 		if !hasSource {
 			result.SamplesSkippedMissingSource++
@@ -293,8 +307,12 @@ func (w *Writer) AppendWithResult(ctx context.Context, env envelope.FrameEnvelop
 			continue
 		}
 		candidate := SourceMileageSampleFromMetric(sample, identity)
-		if err := w.applyRealtimeBaseline(ctx, &candidate); err != nil {
-			return result, err
+		if stationaryCandidate != nil {
+			candidate = *stationaryCandidate
+		} else {
+			if err := w.applyRealtimeBaseline(ctx, &candidate); err != nil {
+				return result, err
+			}
 		}
 		projectDaily := w.shouldProjectDailyMileage(sample)
 		if projectDaily {
@@ -316,6 +334,47 @@ func (w *Writer) AppendWithResult(ctx context.Context, env envelope.FrameEnvelop
 	return result, nil
 }

+func (w *Writer) stationaryCarryForward(ctx context.Context, env envelope.FrameEnvelope, identity SourceIdentity) (MetricSample, SourceMileageSample, bool, error) {
+	if env.Protocol != envelope.ProtocolYutongMQTT || strings.TrimSpace(env.VIN) == "" {
+		return MetricSample{}, SourceMileageSample{}, false, nil
+	}
+	location, ok := telemetry.LocationProjectionForProtocol(env.Protocol, env.Fields)
+	if !ok || location.SpeedKMH == nil || *location.SpeedKMH != 0 {
+		return MetricSample{}, SourceMileageSample{}, false, nil
+	}
+	eventMS, _, ok := envelope.NormalizedEventTimeMSWithReason(env)
+	if !ok {
+		return MetricSample{}, SourceMileageSample{}, false, nil
+	}
+	eventTime := time.UnixMilli(eventMS).In(w.loc)
+	sample := MetricSample{
+		VIN:            strings.TrimSpace(env.VIN),
+		Protocol:       env.Protocol,
+		StatDate:       eventTime.Format("2006-01-02"),
+		EventTime:      eventTime,
+		SourceKey:      SourceKeyForSource(env.Protocol, env.Phone, env.DeviceID, identity.SourceIP, identity.SourceKind, identity.SourceCode),
+		Phone:          strings.TrimSpace(env.Phone),
+		DeviceID:       strings.TrimSpace(env.DeviceID),
+		SourceEndpoint: strings.TrimSpace(env.SourceEndpoint),
+		PlatformName:   strings.TrimSpace(env.PlatformName),
+	}
+	candidate := SourceMileageSampleFromMetric(sample, identity)
+	baseline, found, err := w.previousBaseline(ctx, candidate)
+	if err != nil || !found || baseline.LatestTotalKM <= 0 || baseline.LatestEventTime.IsZero() {
+		return MetricSample{}, SourceMileageSample{}, false, err
+	}
+	sample.TotalMileageKM = baseline.LatestTotalKM
+	candidate = SourceMileageSampleFromMetric(sample, identity)
+	candidate.FirstTotalKM = baseline.LatestTotalKM
+	candidate.LatestTotalKM = baseline.LatestTotalKM
+	candidate.DailyKM = 0
+	candidate.FirstEventTime = baseline.LatestEventTime
+	candidate.LatestEventTime = eventTime
+	candidate.QualityStatus = QualityOK
+	candidate.QualityReason = QualityReasonStationaryCarry
+	return sample, candidate, true, nil
+}
+
 func (w *Writer) writeMileageSample(ctx context.Context, sample MetricSample, candidate SourceMileageSample, projectDaily bool) error {
 	if projectDaily {
 		if beginner, ok := w.exec.(txBeginner); ok {
--- a/go/vehicle-gateway/internal/stats/daily_metric_test.go
+++ b/go/vehicle-gateway/internal/stats/daily_metric_test.go
@@ -1838,6 +1838,107 @@ func TestWriterSkipsConsecutiveDuplicateMileageSamples(t *testing.T) {
 	}
 }

+func TestWriterCarriesPreviousYutongMileageIntoStationaryDay(t *testing.T) {
+	exec := &recordingExec{}
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(exec, loc)
+	eventTime := time.Date(2026, 7, 19, 6, 5, 42, 0, loc)
+	previousTime := time.Date(2026, 7, 18, 16, 48, 10, 0, loc)
+	vin := "LMRKH9AC9R1004099"
+	sourceKey := "YUTONG_MQTT:" + vin + "@PLATFORM:yutong"
+	sample := MetricSample{
+		VIN:       vin,
+		Protocol:  envelope.ProtocolYutongMQTT,
+		StatDate:  "2026-07-19",
+		SourceKey: sourceKey,
+	}
+	writer.baselineCache[mileageCacheKey(sample)] = sourceBaselineCacheEntry{
+		baseline: sourceBaseline{
+			LatestTotalKM:   24245,
+			LatestEventTime: previousTime,
+			QualityReason:   QualityReasonHistorical,
+		},
+		found:    true,
+		cachedAt: time.Now(),
+	}
+	event := managedTestSource(envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolYutongMQTT,
+		VIN:            vin,
+		DeviceID:       vin,
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/2",
+		SourceCode:     "yutong",
+		PlatformName:   "宇通",
+		EventTimeMS:    eventTime.UnixMilli(),
+		ReceivedAtMS:   eventTime.UnixMilli(),
+		Fields: map[string]any{
+			"yutong_mqtt.data.latitude":    "30.645438",
+			"yutong_mqtt.data.longitude":   "114.435672",
+			"yutong_mqtt.data.meter_speed": "0",
+		},
+	})
+
+	result, err := writer.AppendWithResult(context.Background(), event)
+	if err != nil {
+		t.Fatalf("AppendWithResult() error = %v", err)
+	}
+	if result.SamplesRecoveredStationary != 1 || result.SamplesWritten != 1 || result.ProjectionsWritten != 1 {
+		t.Fatalf("stationary carry result = %+v", result)
+	}
+	if result.SamplesSkippedMissingMileage != 1 {
+		t.Fatalf("source-data evidence must retain the missing-mileage counter: %+v", result)
+	}
+	if len(exec.calls) != 7 {
+		t.Fatalf("exec calls = %d, want source touch plus six mileage writes", len(exec.calls))
+	}
+	sourceWrite := exec.calls[1]
+	if !strings.Contains(sourceWrite.query, "INSERT INTO vehicle_daily_mileage_source") {
+		t.Fatalf("source mileage write missing: %s", sourceWrite.query)
+	}
+	if got := sourceWrite.args[9]; got != float64(24245) {
+		t.Fatalf("first total mileage = %#v, want carried 24245", got)
+	}
+	if got := sourceWrite.args[10]; got != float64(24245) {
+		t.Fatalf("latest total mileage = %#v, want carried 24245", got)
+	}
+	if got := sourceWrite.args[11]; got != float64(0) {
+		t.Fatalf("daily mileage = %#v, want explicit zero", got)
+	}
+	if got := sourceWrite.args[16]; got != QualityReasonStationaryCarry {
+		t.Fatalf("quality reason = %#v, want %q", got, QualityReasonStationaryCarry)
+	}
+}
+
+func TestWriterDoesNotCarryMileageForMovingYutongFrame(t *testing.T) {
+	exec := &recordingExec{}
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(exec, loc)
+	eventTime := time.Date(2026, 7, 19, 8, 0, 0, 0, loc)
+	event := managedTestSource(envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolYutongMQTT,
+		VIN:            "LMRKH9AC9R1004099",
+		DeviceID:       "LMRKH9AC9R1004099",
+		SourceEndpoint: "mqtt://yutong/ytforward/shln/2",
+		SourceCode:     "yutong",
+		EventTimeMS:    eventTime.UnixMilli(),
+		Fields: map[string]any{
+			"yutong_mqtt.data.latitude":    "30.645438",
+			"yutong_mqtt.data.longitude":   "114.435672",
+			"yutong_mqtt.data.meter_speed": "12",
+		},
+	})
+
+	result, err := writer.AppendWithResult(context.Background(), event)
+	if err != nil {
+		t.Fatalf("AppendWithResult() error = %v", err)
+	}
+	if result.SamplesRecoveredStationary != 0 || result.SamplesWritten != 0 || result.SamplesSkippedMissingMileage != 1 {
+		t.Fatalf("moving frame must remain missing-mileage evidence: %+v", result)
+	}
+	if len(exec.calls) != 1 || !strings.Contains(exec.calls[0].query, "INSERT INTO vehicle_data_source") {
+		t.Fatalf("moving frame writes = %+v, want source touch only", exec.calls)
+	}
+}
+
 func TestWriterAppendWithResultReportsDuplicateMileage(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec, time.FixedZone("Asia/Shanghai", 8*3600))
--- a/go/vehicle-gateway/internal/stats/source_mileage.go
+++ b/go/vehicle-gateway/internal/stats/source_mileage.go
@@ -15,6 +15,7 @@ const (
 	QualityInvalidDelta           = "INVALID_DELTA"
 	QualityReasonHistorical       = "historical_source_baseline"
 	QualityReasonCurrentDayFirst  = "current_day_first_baseline"
+	QualityReasonStationaryCarry  = "stationary_carry_forward"
 	maxSelectedDailyMileageKM     = 2500
 	maxSelectedDailyMileageKMSQL  = "2500"
 	maxNegativeMileageJitterKMSQL = "1"