diff --git a/server/app/goauto/device/android_client_report_contract_test.go b/server/app/goauto/device/android_client_report_contract_test.go
new file mode 100644
index 0000000..2902adc
--- /dev/null
+++ b/server/app/goauto/device/android_client_report_contract_test.go
@@ -0,0 +1,89 @@
+package device
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+)
+
+// Feed reports captured by Android's real HTTP client into the real Server
+// handler. This optional cross-build check uses synthetic test data only.
+func TestAndroidGeneratedHeartbeatReports(t *testing.T) {
+	path := os.Getenv("GOAUTO_378_ANDROID_REPORTS")
+	if path == "" {
+		t.Skip("set GOAUTO_378_ANDROID_REPORTS to the Android test-generated JSON array")
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var reports []json.RawMessage
+	if err := json.Unmarshal(data, &reports); err != nil {
+		t.Fatal("Android report fixture is not a JSON array")
+	}
+	if len(reports) < 3 {
+		t.Fatal("expected zero-failure, failed and interrupted reports")
+	}
+	db := openTestDatabase(t)
+	service := newTestService(t, db)
+	_, registered := registerHeartbeatDevice(t, service)
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+	router.POST("/heartbeat", Handler{DB: db}.Heartbeat)
+	var sawZero, sawFailure, sawInterrupted bool
+	for i, raw := range reports {
+		t.Run(fmt.Sprintf("android_report_%d", i), func(t *testing.T) {
+			canonical, status := validateHeartbeatClientReport(raw)
+			if status != "accepted" || canonical == nil {
+				t.Fatalf("Android-generated report rejected: classification=%s", status)
+			}
+			var report heartbeatClientReport
+			if err := json.Unmarshal(raw, &report); err != nil {
+				t.Fatal("report decode failed")
+			}
+			sawZero = sawZero || report.FailedRounds == 0
+			sawFailure = sawFailure || report.FailedRounds > 0
+			sawInterrupted = sawInterrupted || report.HasInterruptedRound
+			id := uuid.NewString()
+			body := fmt.Sprintf(`{"requestId":%q,"currentTaskId":null,"clientReport":%s}`, id, raw)
+			for replay := 0; replay < 2; replay++ {
+				req := httptest.NewRequest(http.MethodPost, "/heartbeat", strings.NewReader(body))
+				req.Header.Set("Authorization", "Bearer "+testDeviceToken)
+				res := httptest.NewRecorder()
+				router.ServeHTTP(res, req)
+				if res.Code != http.StatusOK {
+					t.Fatalf("heartbeat status=%d", res.Code)
+				}
+				var response struct {
+					Data struct {
+						AcceptsClientReport bool `json:"acceptsClientReport"`
+					} `json:"data"`
+				}
+				if json.Unmarshal(res.Body.Bytes(), &response) != nil || !response.Data.AcceptsClientReport {
+					t.Fatal("successful response did not advertise report capability")
+				}
+			}
+			var rows []struct {
+				DeviceID           uint64
+				ClientReportStatus string
+				ClientReportJSON   *string
+			}
+			if err := db.Table("agent_heartbeat_log").Where("request_id = ?", id).Find(&rows).Error; err != nil {
+				t.Fatal(err)
+			}
+			if len(rows) != 1 || rows[0].DeviceID != registered.DeviceID || rows[0].ClientReportStatus != "accepted" || rows[0].ClientReportJSON == nil || *rows[0].ClientReportJSON != *canonical {
+				t.Fatal("accepted Android report was not stored once with the correct device and canonical payload")
+			}
+		})
+	}
+	if !sawZero || !sawFailure || !sawInterrupted {
+		t.Fatal("fixture must cover zero-failure, failed and interrupted reports")
+	}
+}