feat(go): reuse parsed fields across projections

docs/ops/go-vehicle-ingest-memory.md

@@ -0,0 +1,341 @@
+# Go 车辆接入上下文记忆
+
+更新时间：2026-07-03
+
+这份文档用于在 Codex 上下文重载后快速恢复项目状态。更完整的运行排查步骤见：
+
+- `docs/ops/vehicle-ingest-runbook.md`
+- `docs/architecture/production-data-plane-inventory.md`
+
+## 当前目标
+
+Go 版本车辆数据接入链路已经作为生产主链路运行在 ECS `115.29.187.205`。
+
+核心目标：
+
+1. 高性能可靠接收 GB32960、JT808、宇通 MQTT。
+2. 协议解析后先写 NATS，再桥接 Kafka。
+3. Kafka raw 供 TDengine 历史、Redis 实时、MySQL 当前态/统计消费。
+4. 尽量避免 Java 老链路、Xinda 相关链路和重复存储。
+5. 解析字段只投影一次，避免 TDengine/Redis/MySQL 各自重复 flatten。
+
+## 服务和端口
+
+ECS：`115.29.187.205`
+
+| 服务 | systemd | 端口 | 作用 |
+| --- | --- | --- | --- |
+| Gateway | `lingniu-go-gateway.service` | `808`、`32960`、`20211` | JT808、GB32960、宇通 MQTT 接入和解析 |
+| NATS fast writer | `lingniu-go-nats-fast-writer.service` | 健康端口随 env | NATS 快速写 TDengine/Redis |
+| NATS Kafka bridge | `lingniu-go-nats-kafka-bridge.service` | `20214` | NATS 到 Kafka |
+| History writer | `lingniu-go-history-writer.service` | `20212` | Kafka raw 写 TDengine |
+| Stat writer | `lingniu-go-stat-writer.service` | `20213` | Kafka raw 写每日里程 |
+| Realtime API | `lingniu-go-realtime-api.service` | `20200` | Redis/MySQL 投影和 HTTP API |
+
+业务端口：
+
+- JT808：`0.0.0.0:808`
+- GB32960：`0.0.0.0:32960`
+- Swagger/API：`http://115.29.187.205:20200/swagger-ui/index.html`
+
+## 部署路径
+
+Go 服务使用 systemd 裸机部署，不使用 Docker。
+
+```bash
+/opt/lingniu-go-native/current
+/opt/lingniu-go-native/releases/*
+/opt/lingniu-go-native/env/*.env
+```
+
+最近 release：
+
+```text
+/opt/lingniu-go-native/releases/parsed-fields-once-20260703163821
+```
+
+服务重启：
+
+```bash
+systemctl restart lingniu-go-gateway.service
+systemctl restart lingniu-go-nats-fast-writer.service
+systemctl restart lingniu-go-nats-kafka-bridge.service
+systemctl restart lingniu-go-history-writer.service
+systemctl restart lingniu-go-stat-writer.service
+systemctl restart lingniu-go-realtime-api.service
+```
+
+健康检查：
+
+```bash
+for port in 20211 20212 20213 20214 20200; do
+  curl -fsS "http://127.0.0.1:${port}/readyz"
+  echo
+done
+```
+
+## 中间件
+
+Kafka / NATS ECS：
+
+- 公网：`114.55.58.251`
+- 内网：`172.17.111.56`
+- NATS：`172.17.111.56:4222`
+
+TDengine：
+
+- 内网：`172.17.111.57`
+- WS：`172.17.111.57:6041`
+- 数据库：`lingniu_vehicle_ts`
+
+MySQL RDS：
+
+- 内网：`rm-bp179zbv481rnw3e2.mysql.rds.aliyuncs.com:3306`
+- 数据库：`lingniu_vehicle_data`
+
+Redis：
+
+- 内网：`r-bp1u741kij7e51i481.redis.rds.aliyuncs.com:6379`
+- DB：`50`
+
+不要在最终回答中明文输出生产密码。
+
+## Topic
+
+当前 Go raw topic：
+
+```text
+vehicle.raw.go.gb32960.v1
+vehicle.raw.go.jt808.v1
+vehicle.raw.go.yutong-mqtt.v1
+```
+
+fields topic 已存在：
+
+```text
+vehicle.fields.go.gb32960.v1
+vehicle.fields.go.jt808.v1
+vehicle.fields.go.yutong-mqtt.v1
+```
+
+当前核心链路仍以 raw topic 作为事实输入；raw envelope 里已经包含一次性预计算的 `parsed_fields`。
+
+## 代码结构
+
+主要目录：
+
+```text
+go/vehicle-gateway/cmd/gateway
+go/vehicle-gateway/cmd/history-writer
+go/vehicle-gateway/cmd/realtime-api
+go/vehicle-gateway/cmd/stat-writer
+go/vehicle-gateway/cmd/nats-fast-writer
+go/vehicle-gateway/cmd/nats-kafka-bridge
+go/vehicle-gateway/internal/protocol/gb32960
+go/vehicle-gateway/internal/protocol/jt808
+go/vehicle-gateway/internal/protocol/yutongmqtt
+go/vehicle-gateway/internal/realtime
+go/vehicle-gateway/internal/history
+go/vehicle-gateway/internal/identity
+```
+
+每次改代码后在本地跑：
+
+```bash
+cd go/vehicle-gateway
+go test ./...
+```
+
+## 解析和存储原则
+
+### 一次解析字段
+
+2026-07-03 已完成优化：
+
+- `FrameEnvelope` 增加：
+  - `parsed_fields`
+  - `parsed_field_types`
+- Gateway 在发布 raw 前调用 `realtime.EnsureParsedFields(&env)`。
+- TDengine writer、Redis realtime KV、MySQL snapshot 优先使用 `env.ParsedFields`。
+- 旧消息没有 `parsed_fields` 时，保留 fallback，从 `Parsed` 展开一次。
+
+相关文件：
+
+```text
+go/vehicle-gateway/internal/envelope/envelope.go
+go/vehicle-gateway/internal/realtime/kv.go
+go/vehicle-gateway/internal/gateway/tcp_server.go
+go/vehicle-gateway/internal/gateway/mqtt_client.go
+go/vehicle-gateway/internal/history/writer.go
+go/vehicle-gateway/internal/realtime/repository.go
+go/vehicle-gateway/internal/realtime/snapshot_writer.go
+```
+
+### GB32960 多帧
+
+GB32960 有两类实际模式：
+
+1. 单条 `0x02` 同时包含标准 data unit 和 vendor data unit。
+2. 标准帧加 vendor 栈分片帧。
+
+例子：
+
+- `LB9A32A24R0LS1426`：单帧完整混合上报，单帧约 `774 bytes`，`gd_fc_stack.cell_count=108`。
+- `LNXNEGRR7SR318212`：多帧上报，`gd_fc_stack.cell_count=432`，按 `200 + 200 + 32` 分片。
+
+TDengine raw_frames 必须保持单帧事实，不跨帧合并。
+
+Redis/MySQL 实时视图可以按 `protocol + vin` 增量合并，但不能让后来的 stack-only 帧覆盖标准车辆字段。
+
+### JT808
+
+JT808 主入口端口是 `808`，不再使用 `8089`。
+
+解析重点：
+
+- 包头手机号按 BCD 去前导 0。
+- `0x0100` 注册帧写 `jt808_registration`。
+- `0x0102` 鉴权帧尝试按 phone 查 registration/binding 关联 VIN。
+- `0x0200` 位置帧即使没有注册/鉴权，也会按 phone 降级查 `vehicle_identity_binding`，建立 session。
+- 位置附加信息 `0x01` 是 GPS 总里程，按差值用于每日里程。
+
+## MySQL 身份表
+
+`vehicle_identity_binding` 是外部维护事实表，服务只读，不允许运行时写入。
+
+核心字段：
+
+```text
+vin
+plate
+phone
+oem
+updated_at
+```
+
+用途：
+
+- JT808 用 phone 或 plate 找 VIN。
+- Realtime snapshot/location 用 VIN 反查 plate。
+- 后续导入 G7s、广安车联等来源时更新 phone/oem。
+
+`jt808_registration` 是 808 注册鉴权运行状态表，以 phone 为主键，记录注册、鉴权、source_endpoint、关联 VIN 状态。
+
+## 2026-07-03 数据维护记录
+
+### G7s binding
+
+源文件：
+
+```text
+/Users/lingniu/Library/Mobile Documents/com~apple~CloudDocs/rsync/2026_07_02_17_11_37转发配置列表-1(2).xlsx
+```
+
+处理规则：
+
+1. 删除原有 G7/G7s 的 `phone/oem`。
+2. 使用文件中的 `手机号` 列更新。
+3. 冲突的不更新，其他更新。
+
+执行结果：
+
+- 清空旧 G7/G7s：`666` 行。
+- 更新安全 G7s：`561` 行。
+- 跳过：`72` 行。
+  - 缺 plate 或 VIN：`14`
+  - 与非 G7/G7s 绑定冲突：`58`
+
+跳过清单：
+
+```text
+outputs/g7s_binding_skipped_apply.csv
+```
+
+### JT808 unknown VIN 导出
+
+导出条件：
+
+- `jt808_registration.vin` 为空、`unknown` 或 `unknow`
+- 且 `phone` 不存在于 `vehicle_identity_binding.phone`
+
+结果：
+
+- `30` 个 phone
+
+导出文件：
+
+```text
+outputs/jt808_unknown_vin_phone_not_in_binding.csv
+```
+
+## 常用查询
+
+历史 raw frame：
+
+```bash
+curl -s 'http://115.29.187.205:20200/api/history/raw-frames?protocol=GB32960&vin=LB9A32A24R0LS1426&limit=1&includeFields=true'
+```
+
+只取指定 parsed fields：
+
+```bash
+curl -s 'http://115.29.187.205:20200/api/history/raw-frames?protocol=GB32960&vin=LB9A32A24R0LS1426&limit=1&includeFields=true&fields=gb32960.vehicle.speed_kmh&fields=gb32960.gd_fc_stack.stack_water_outlet_temp_c'
+```
+
+808 源 IP：
+
+```bash
+journalctl -u lingniu-go-gateway.service --since '10 minutes ago' --no-pager
+ss -tn sport = :808
+```
+
+最近已观察到 808 源 IP：
+
+```text
+115.159.85.149
+222.66.200.68
+122.152.221.156
+115.231.168.135
+```
+
+## 部署步骤
+
+本地构建：
+
+```bash
+cd go/vehicle-gateway
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/gateway ./cmd/gateway
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/history-writer ./cmd/history-writer
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/realtime-api ./cmd/realtime-api
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/stat-writer ./cmd/stat-writer
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/nats-fast-writer ./cmd/nats-fast-writer
+GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -trimpath -ldflags='-s -w' -o /tmp/lingniu-go-deploy/nats-kafka-bridge ./cmd/nats-kafka-bridge
+```
+
+上传部署：
+
+```bash
+release="name-$(date +%Y%m%d%H%M%S)"
+ssh root@115.29.187.205 "mkdir -p /opt/lingniu-go-native/releases/$release"
+scp /tmp/lingniu-go-deploy/* root@115.29.187.205:/opt/lingniu-go-native/releases/$release/
+ssh root@115.29.187.205 "chmod 755 /opt/lingniu-go-native/releases/$release/* && ln -sfn /opt/lingniu-go-native/releases/$release /opt/lingniu-go-native/current"
+```
+
+部署后验证：
+
+```bash
+ssh root@115.29.187.205 '
+systemctl is-active lingniu-go-gateway.service lingniu-go-nats-fast-writer.service lingniu-go-nats-kafka-bridge.service lingniu-go-history-writer.service lingniu-go-stat-writer.service lingniu-go-realtime-api.service
+for port in 20211 20212 20213 20214 20200; do curl -fsS "http://127.0.0.1:${port}/readyz"; echo; done
+journalctl -u lingniu-go-gateway.service --since "2 minutes ago" --no-pager | grep -Ei "error|failed|panic|fatal" || true
+'
+```
+
+## 下次恢复上下文时先做
+
+1. 读本文件。
+2. 读 `docs/ops/vehicle-ingest-runbook.md`。
+3. 读 `docs/architecture/production-data-plane-inventory.md`。
+4. 执行 `git status --short`。
+5. 如果涉及生产，先查 ECS 服务健康和最近日志。
+

go/vehicle-gateway/internal/envelope/envelope.go

@@ -49,6 +49,8 @@ type FrameEnvelope struct {
 	RawHex           string            `json:"raw_hex,omitempty"`
 	RawText          string            `json:"raw_text,omitempty"`
 	Parsed           map[string]any    `json:"parsed,omitempty"`
+	ParsedFields     map[string]any    `json:"parsed_fields,omitempty"`
+	ParsedFieldTypes map[string]string `json:"parsed_field_types,omitempty"`
 	Fields           map[string]any    `json:"fields,omitempty"`
 	ParseStatus      ParseStatus       `json:"parse_status"`
 	ParseError       string            `json:"parse_error,omitempty"`

go/vehicle-gateway/internal/gateway/mqtt_client.go

@@ -222,6 +222,9 @@ func (c *MQTTClient) handleMessage(ctx context.Context, topic string, payload []
 	}
 	frameStatus = env.ParseStatus
 	c.recordFrameMetric(env.ParseStatus)
+	if env.ParseStatus != envelope.ParseBadFrame {
+		realtime.EnsureParsedFields(&env)
+	}
 	if err := c.cfg.Sink.PublishRaw(messageCtx, env); err != nil {
 		c.recordPublishMetric("raw", "error")
 		c.cfg.Logger.Error("publish mqtt raw failed", "topic", topic, "event_id", env.StableEventID(), "error", err)

go/vehicle-gateway/internal/gateway/tcp_server.go

@@ -237,6 +237,9 @@ func (s *TCPServer) handleFrame(ctx context.Context, conn net.Conn, raw []byte,
 	}
 	frameStatus = env.ParseStatus
 	s.recordFrameMetric(env.ParseStatus)
+	if env.ParseStatus != envelope.ParseBadFrame {
+		realtime.EnsureParsedFields(&env)
+	}
 
 	if err := s.sink.PublishRaw(frameCtx, env); err != nil {
 		s.recordPublishMetric("raw", "error")

go/vehicle-gateway/internal/history/writer.go

@@ -318,11 +318,11 @@ func jsonString(value any) string {
 }
 
 func parsedFieldsJSONString(env envelope.FrameEnvelope) string {
-	fieldsEnv, ok := realtime.BuildFieldsEnvelope(env)
+	fields, _, ok := realtime.ParsedFieldsForEnvelope(env)
-	if !ok || len(fieldsEnv.Fields) == 0 {
+	if !ok || len(fields) == 0 {
 		return ""
 	}
-	return jsonString(fieldsEnv.Fields)
+	return jsonString(fields)
 }
 
 func floatField(env envelope.FrameEnvelope, key string) (float64, bool) {

go/vehicle-gateway/internal/history/writer_test.go

@@ -111,8 +111,8 @@ func TestWriterChunksOversizedParsedFields(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec)
 	env := sampleEnvelope()
-	env.Parsed = map[string]any{
+	env.ParsedFields = map[string]any{
-		"large_payload": strings.Repeat("x", 16_128),
+		"jt808.location.large_payload": strings.Repeat("x", 16_128),
 	}
 
 	if err := writer.AppendRawFrame(context.Background(), env); err != nil {
@@ -131,6 +131,30 @@ func TestWriterChunksOversizedParsedFields(t *testing.T) {
 	}
 }
 
+func TestWriterUsesEnvelopeParsedFieldsWithoutReflattening(t *testing.T) {
+	exec := &recordingExec{}
+	writer := NewWriter(exec)
+	env := sampleEnvelope()
+	env.Parsed = map[string]any{
+		"location": map[string]any{"speed_kmh": 99},
+	}
+	env.ParsedFields = map[string]any{
+		"jt808.location.speed_kmh": "12.3",
+	}
+
+	if err := writer.AppendRawFrame(context.Background(), env); err != nil {
+		t.Fatalf("AppendRawFrame() error = %v", err)
+	}
+
+	rawInsert := findSQL(exec.calls, "INSERT INTO raw_")
+	if !strings.Contains(rawInsert, `"jt808.location.speed_kmh":"12.3"`) {
+		t.Fatalf("raw insert should use precomputed parsed fields: %s", rawInsert)
+	}
+	if strings.Contains(rawInsert, `"jt808.location.speed_kmh":"99"`) {
+		t.Fatalf("raw insert should not re-flatten parsed payload: %s", rawInsert)
+	}
+}
+
 func TestWriterLeavesParsedFieldsEmptyWhenNoParsedPayload(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec)

go/vehicle-gateway/internal/realtime/kv.go

@@ -26,16 +26,8 @@ func BuildFieldsEnvelope(env envelope.FrameEnvelope) (envelope.FrameEnvelope, bo
 	if !envelope.IsRealtimeTelemetryFrame(env) {
 		return envelope.FrameEnvelope{}, false
 	}
-	rows := realtimeKVFields(env, env.Parsed)
+	fields, fieldTypes, ok := ParsedFieldsForEnvelope(env)
-	fields := make(map[string]any, len(rows))
+	if !ok {
-	for _, row := range rows {
-		key := row.Domain
-		if strings.TrimSpace(row.Field) != "" {
-			key += "." + row.Field
-		}
-		fields[key] = row.Value
-	}
-	if len(fields) == 0 {
 		return envelope.FrameEnvelope{}, false
 	}
 	out := envelope.FrameEnvelope{
@@ -53,6 +45,8 @@ func BuildFieldsEnvelope(env envelope.FrameEnvelope) (envelope.FrameEnvelope, bo
 		EventTimeMS:      env.EventTimeMS,
 		ReceivedAtMS:     env.ReceivedAtMS,
 		Fields:           fields,
+		ParsedFields:     fields,
+		ParsedFieldTypes: fieldTypes,
 		Parsed: map[string]any{
 			"source_event_id": env.StableEventID(),
 			"field_mapping":   realtimeFieldMappingVersion,
@@ -62,6 +56,91 @@ func BuildFieldsEnvelope(env envelope.FrameEnvelope) (envelope.FrameEnvelope, bo
 	return out, true
 }
 
+func EnsureParsedFields(env *envelope.FrameEnvelope) bool {
+	if env == nil {
+		return false
+	}
+	if len(env.ParsedFields) > 0 {
+		if env.ParsedFieldTypes == nil {
+			env.ParsedFieldTypes = inferParsedFieldTypes(env.ParsedFields)
+		}
+		return true
+	}
+	fields, fieldTypes, ok := ParsedFieldsForEnvelope(*env)
+	if !ok {
+		return false
+	}
+	env.ParsedFields = fields
+	env.ParsedFieldTypes = fieldTypes
+	return true
+}
+
+func ParsedFieldsForEnvelope(env envelope.FrameEnvelope) (map[string]any, map[string]string, bool) {
+	if len(env.ParsedFields) > 0 {
+		fields := cloneAnyMap(env.ParsedFields)
+		fieldTypes := cloneStringMap(env.ParsedFieldTypes)
+		if len(fieldTypes) == 0 {
+			fieldTypes = inferParsedFieldTypes(fields)
+		}
+		return fields, fieldTypes, true
+	}
+	rows := realtimeKVFields(env, env.Parsed)
+	if len(rows) == 0 {
+		return nil, nil, false
+	}
+	fields := make(map[string]any, len(rows))
+	fieldTypes := make(map[string]string, len(rows))
+	for _, row := range rows {
+		key := realtimeKVFieldPath(row.Domain, row.Field)
+		if key == "" {
+			continue
+		}
+		fields[key] = row.Value
+		fieldTypes[key] = row.ValueType
+	}
+	if len(fields) == 0 {
+		return nil, nil, false
+	}
+	return fields, fieldTypes, true
+}
+
+func inferParsedFieldTypes(fields map[string]any) map[string]string {
+	if len(fields) == 0 {
+		return nil
+	}
+	out := make(map[string]string, len(fields))
+	for key, value := range fields {
+		_, valueType, ok := stringifyKVValue(value)
+		if !ok {
+			continue
+		}
+		out[key] = valueType
+	}
+	return out
+}
+
+func cloneAnyMap(in map[string]any) map[string]any {
+	if len(in) == 0 {
+		return nil
+	}
+	out := make(map[string]any, len(in))
+	for key, value := range in {
+		out[key] = value
+	}
+	return out
+}
+
+func cloneStringMap(in map[string]string) map[string]string {
+	if len(in) == 0 {
+		return nil
+	}
+	out := make(map[string]string, len(in))
+	for key, value := range in {
+		out[key] = value
+	}
+	return out
+}
+
 type protocolFieldMapping struct {
 	Prefix       string
 	GBDataUnits  bool

go/vehicle-gateway/internal/realtime/repository.go

@@ -348,20 +348,10 @@ func (r *Repository) setJSON(ctx context.Context, key string, value any, ttl tim
 }
 
 func (r *Repository) setKV(ctx context.Context, vin string, env envelope.FrameEnvelope, parsed map[string]any) error {
-	rows := realtimeKVFields(env, parsed)
+	if len(env.ParsedFields) == 0 && len(parsed) > 0 {
-	if len(rows) == 0 {
+		env.Parsed = parsed
-		return nil
-	}
-	values := make(map[string]any, len(rows))
-	types := make(map[string]any, len(rows))
-	for _, row := range rows {
-		field := realtimeKVFieldPath(row.Domain, row.Field)
-		if field == "" {
-			continue
-		}
-		values[field] = row.Value
-		types[field] = row.ValueType
 	}
+	values, types := realtimeKVMapsForEnvelope(env)
 	if len(values) == 0 {
 		return nil
 	}
@@ -383,8 +373,7 @@ func (r *Repository) setKV(ctx context.Context, vin string, env envelope.FrameEn
 }
 
 func (r *Repository) setFastProjection(ctx context.Context, vehicleKey string, vin string, env envelope.FrameEnvelope) error {
-	rows := realtimeKVFields(env, env.Parsed)
+	values, types := realtimeKVMapsForEnvelope(env)
-	values, types := realtimeKVMaps(rows)
 	eventTimeMS := eventTimeOrReceivedMS(env)
 	offlineAfterMS := env.ReceivedAtMS + r.cfg.ttl().Milliseconds()
 	online := OnlineStatus{
@@ -435,6 +424,30 @@ func (r *Repository) setFastProjection(ctx context.Context, vehicleKey string, v
 	return err
 }
 
+func realtimeKVMapsForEnvelope(env envelope.FrameEnvelope) (map[string]any, map[string]any) {
+	if fields, fieldTypes, ok := ParsedFieldsForEnvelope(env); ok {
+		values := make(map[string]any, len(fields))
+		types := make(map[string]any, len(fields))
+		for field, value := range fields {
+			if strings.TrimSpace(field) == "" {
+				continue
+			}
+			stringValue, valueType, ok := stringifyKVValue(value)
+			if !ok {
+				continue
+			}
+			values[field] = stringValue
+			if typed := strings.TrimSpace(fieldTypes[field]); typed != "" {
+				types[field] = typed
+			} else {
+				types[field] = valueType
+			}
+		}
+		return values, types
+	}
+	return nil, nil
+}
+
 func realtimeKVMaps(rows []RealtimeKVField) (map[string]any, map[string]any) {
 	values := make(map[string]any, len(rows))
 	types := make(map[string]any, len(rows))

go/vehicle-gateway/internal/realtime/repository_test.go

@@ -646,6 +646,37 @@ func TestRepositoryOnlineStatus(t *testing.T) {
 	}
 }
 
+func TestRepositoryUsesEnvelopeParsedFieldsForRealtimeKV(t *testing.T) {
+	repo, closeFn := newTestRepository(t)
+	defer closeFn()
+	ctx := context.Background()
+
+	if err := repo.Update(ctx, envelope.FrameEnvelope{
+		Protocol:     envelope.ProtocolJT808,
+		VIN:          "VIN001",
+		EventTimeMS:  1000,
+		ReceivedAtMS: 1100,
+		MessageID:    "0x0200",
+		Parsed: map[string]any{
+			"location": map[string]any{"speed_kmh": 99},
+		},
+		ParsedFields: map[string]any{
+			"jt808.location.speed_kmh": "12.3",
+		},
+		Fields: map[string]any{envelope.FieldSpeedKMH: 12.3},
+	}); err != nil {
+		t.Fatalf("Update() error = %v", err)
+	}
+
+	values, err := repo.client.HGetAll(ctx, realtimeKVValuesKey(envelope.ProtocolJT808, "VIN001")).Result()
+	if err != nil {
+		t.Fatalf("HGetAll() error = %v", err)
+	}
+	if got, want := values["jt808.location.speed_kmh"], "12.3"; got != want {
+		t.Fatalf("speed kv = %#v, want %q; all=%#v", got, want, values)
+	}
+}
+
 func TestRepositorySkipsFramesWithoutVIN(t *testing.T) {
 	repo, closeFn := newTestRepository(t)
 	defer closeFn()

go/vehicle-gateway/internal/realtime/snapshot_writer.go

@@ -187,7 +187,10 @@ func (w *SnapshotWriter) snapshotFieldsForEnvelope(ctx context.Context, env enve
 		if len(existing) > 0 {
 			if isStructuredSnapshotParsed(env.Protocol, existing) {
 				parsed = mergeParsedForProtocol(env.Protocol, existing, env.Parsed)
-				return realtimeSnapshotFlatFields(env, parsed), nil
+				mergedEnv := env
+				mergedEnv.ParsedFields = nil
+				mergedEnv.ParsedFieldTypes = nil
+				return realtimeSnapshotFlatFields(mergedEnv, parsed), nil
 			}
 			return mergeRealtimeSnapshotFields(existing, incoming), nil
 		}
@@ -196,6 +199,12 @@ func (w *SnapshotWriter) snapshotFieldsForEnvelope(ctx context.Context, env enve
 }
 
 func realtimeSnapshotFlatFields(env envelope.FrameEnvelope, parsed map[string]any) map[string]any {
+	if len(env.ParsedFields) > 0 {
+		fields := cloneMap(env.ParsedFields)
+		if len(fields) > 0 {
+			return fields
+		}
+	}
 	rows := realtimeKVFields(env, parsed)
 	if len(rows) == 0 {
 		return nil

go/vehicle-gateway/internal/realtime/snapshot_writer_test.go

@@ -257,6 +257,57 @@ func TestSnapshotWriterMergesGB32960ParsedJSONAcrossSplitRealtimeFrames(t *testi
 	}
 }
 
+func TestSnapshotWriterUsesEnvelopeParsedFieldsWithoutReflattening(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	writer := NewSnapshotWriter(db)
+
+	mock.ExpectQuery("SELECT parsed_json FROM vehicle_realtime_snapshot WHERE protocol = \\? AND vin = \\?").
+		WithArgs("GB32960", "VIN001").
+		WillReturnRows(sqlmock.NewRows([]string{"parsed_json"}))
+	mock.ExpectExec("INSERT INTO vehicle_realtime_snapshot").
+		WithArgs(
+			"GB32960",
+			"VIN001",
+			"",
+			"",
+			"",
+			jsonFlatFieldsArg{fields: map[string]string{
+				"gb32960.vehicle.speed_kmh": "12.3",
+			}},
+			sqlmock.AnyArg(),
+			sqlmock.AnyArg(),
+			sqlmock.AnyArg(),
+		).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	err = writer.Update(context.Background(), envelope.FrameEnvelope{
+		Protocol:     envelope.ProtocolGB32960,
+		MessageID:    "0x02",
+		VIN:          "VIN001",
+		EventTimeMS:  1782918600000,
+		ReceivedAtMS: 1782918601000,
+		Parsed: map[string]any{
+			"data_units": []any{
+				map[string]any{"type": "0x01", "name": "vehicle", "value": map[string]any{"speed_kmh": 99}},
+			},
+		},
+		ParsedFields: map[string]any{
+			"gb32960.vehicle.speed_kmh": "12.3",
+		},
+		Fields: map[string]any{envelope.FieldSpeedKMH: 12.3},
+	})
+	if err != nil {
+		t.Fatalf("Update() error = %v", err)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("sql expectations: %v", err)
+	}
+}
+
 func TestSnapshotWriterCollapsesGB32960StackFragmentsWhenMergingParsedJSON(t *testing.T) {
 	db, mock, err := sqlmock.New()
 	if err != nil {