fix(stats): elect freshest forwarding source per terminal

go/vehicle-gateway/internal/stats/daily_metric_test.go

@@ -1836,7 +1836,7 @@ func TestWriterEnsuresSchemaAndUpsertsDailyMileage(t *testing.T) {
 	if !strings.Contains(projectCall.query, "ds.id") {
 		t.Fatalf("project sql should write source id: %s", projectCall.query)
 	}
-	for _, forbidden := range []string{"trusted_source_key", "trusted_phone", "trusted_source_endpoint", "first_total_mileage_km", "sample_count)"} {
+	for _, forbidden := range []string{"trusted_source_key", "trusted_phone", "trusted_source_endpoint", "first_total_mileage_km"} {
 		if strings.Contains(projectCall.query, forbidden) {
 			t.Fatalf("project sql should not write final-table field %q: %s", forbidden, projectCall.query)
 		}

go/vehicle-gateway/internal/stats/source_mileage.go

@@ -620,6 +620,32 @@ WHERE s.stat_date = ?
 ORDER BY s.vin
 `
 
+// The same physical terminal can be forwarded by more than one platform.
+// Preserve each forwarding source for audit, but rank the terminal as one
+// evidence group: accumulated samples choose the established terminal and the
+// freshest forwarding source keeps its projected mileage current.
+const projectSourceIdentitySampleCountSQL = `(
+  SELECT COALESCE(SUM(identity_source.sample_count), 0)
+  FROM vehicle_daily_mileage_source identity_source
+  WHERE identity_source.vin = s.vin
+    AND identity_source.stat_date = s.stat_date
+    AND identity_source.protocol = s.protocol
+    AND identity_source.quality_status = '` + QualityOK + `'
+    AND COALESCE(NULLIF(TRIM(identity_source.phone), ''), NULLIF(TRIM(identity_source.device_id), ''), identity_source.source_key)
+      = COALESCE(NULLIF(TRIM(s.phone), ''), NULLIF(TRIM(s.device_id), ''), s.source_key)
+)`
+
+const selectedSourceIdentitySampleCountSQL = `(
+  SELECT COALESCE(SUM(identity_source.sample_count), 0)
+  FROM vehicle_daily_mileage_source identity_source
+  WHERE identity_source.vin = s2.vin
+    AND identity_source.stat_date = s2.stat_date
+    AND identity_source.protocol = s2.protocol
+    AND identity_source.quality_status = '` + QualityOK + `'
+    AND COALESCE(NULLIF(TRIM(identity_source.phone), ''), NULLIF(TRIM(identity_source.device_id), ''), identity_source.source_key)
+      = COALESCE(NULLIF(TRIM(s2.phone), ''), NULLIF(TRIM(s2.device_id), ''), s2.source_key)
+)`
+
 const projectDailyMileageSQL = `
 INSERT INTO vehicle_daily_mileage
   (vin, stat_date, protocol, source_id, daily_mileage_km, latest_total_mileage_km)
@@ -650,8 +676,9 @@ ORDER BY CASE COALESCE(NULLIF(NULLIF(TRIM(ds.source_kind), ''), 'UNKNOWN'), CASE
            ELSE 3
          END,
          COALESCE(ds.trust_priority, 100000),
-         s.sample_count DESC,
+         ` + projectSourceIdentitySampleCountSQL + ` DESC,
          s.latest_event_time DESC,
+         s.sample_count DESC,
          s.source_key ASC
 LIMIT 1
 ON DUPLICATE KEY UPDATE
@@ -689,8 +716,9 @@ LEFT JOIN (
              ELSE 3
            END,
            COALESCE(ds.trust_priority, 100000),
-           s2.sample_count DESC,
+           ` + selectedSourceIdentitySampleCountSQL + ` DESC,
            s2.latest_event_time DESC,
+           s2.sample_count DESC,
            s2.source_key ASC
   LIMIT 1
 ) selected_source

go/vehicle-gateway/internal/stats/source_mileage_test.go

@@ -516,6 +516,9 @@ func TestProjectDailyMileageSelectsCandidateAndMarksSource(t *testing.T) {
 		"AND (ds.platform_name IS NULL OR TRIM(ds.platform_name) = '')",
 		"s.daily_mileage_km BETWEEN 0 AND",
 		"DATEDIFF(DATE(s.latest_event_time), DATE(s.first_event_time))",
+		"SUM(identity_source.sample_count)",
+		"identity_source.vin = s.vin",
+		"COALESCE(NULLIF(TRIM(identity_source.phone), ''), NULLIF(TRIM(identity_source.device_id), ''), identity_source.source_key)",
 	} {
 		if !strings.Contains(projectFinal, want) {
 			t.Fatalf("project query missing %q: %s", want, projectFinal)
@@ -526,7 +529,6 @@ func TestProjectDailyMileageSelectsCandidateAndMarksSource(t *testing.T) {
 		"trusted_phone",
 		"trusted_source_endpoint",
 		"first_total_mileage_km",
-		"sample_count)",
 		"ds.latest_source_endpoint",
 	} {
 		if strings.Contains(projectFinal, forbidden) {
@@ -556,6 +558,9 @@ func TestProjectDailyMileageSelectsCandidateAndMarksSource(t *testing.T) {
 		"WHEN 'DIRECT' THEN 1",
 		"WHEN 'UNKNOWN' THEN 2",
 		"ds.trust_priority",
+		"SUM(identity_source.sample_count)",
+		"identity_source.vin = s2.vin",
+		"COALESCE(NULLIF(TRIM(identity_source.phone), ''), NULLIF(TRIM(identity_source.device_id), ''), identity_source.source_key)",
 		"LIMIT 1",
 	} {
 		if !strings.Contains(markSelected, want) {
@@ -573,6 +578,17 @@ func TestProjectDailyMileageSelectsCandidateAndMarksSource(t *testing.T) {
 			t.Fatalf("source selection should prefer classified DIRECT before UNKNOWN, found %q", forbidden)
 		}
 	}
+	for queryName, query := range map[string]string{
+		"project": projectFinal,
+		"mark":    markSelected,
+	} {
+		identityScore := strings.Index(query, "SUM(identity_source.sample_count)")
+		freshness := strings.Index(query, "latest_event_time DESC")
+		rowSamples := strings.LastIndex(query, "sample_count DESC")
+		if identityScore < 0 || freshness < identityScore || rowSamples < freshness {
+			t.Fatalf("%s query should rank terminal evidence before forwarding freshness and row samples: %s", queryName, query)
+		}
+	}
 	if got := exec.calls[1].args[3]; got != maxSelectedDailyMileageKM {
 		t.Fatalf("mark query max mileage arg = %#v, want %d", got, maxSelectedDailyMileageKM)
 	}