feat(FN-285): fix EMEX parallel decode race — always await second promise

Commits merged:
- fix(FN-285): fix EMEX parallel decode race — always await second promise

Files changed:
apps/api/src/vehicles/vehicles.service.spec.ts | 63 ++++++++++++++++++++++++++
 apps/api/src/vehicles/vehicles.service.ts      |  5 +-
 2 files changed, 66 insertions(+), 2 deletions(-)

Fusion-Task-Id: FN-285

apps/api/src/vehicles/vehicles.service.spec.ts

@@ -375,6 +375,69 @@ describe("VehiclesService", () => {
       expect(result).toEqual(savedVehicle);
       expect(vinApiService.decodeVin).toHaveBeenCalledWith("WBAPH5C55BA123456");
     });
+
+    it("should use EMEX when it returns a vehicle (parallel decode)", async () => {
+      vi.mocked(isValidVin).mockReturnValue(true);
+
+      const emexVehicle = {
+        brand: "BMW",
+        model: "320i",
+        year: 2020,
+        engineCode: "N20",
+        engineType: null,
+        engineVolume: null,
+        transmission: "Auto",
+        bodyType: "Sedan",
+        driveType: null,
+        raw: {},
+      };
+
+      let selectCall = 0;
+      let insertCall = 0;
+      const savedVehicle = { id: "v-emex", vin: "WBAPH5C55BA123456", source: "emex" };
+      const db = {
+        select: vi.fn().mockImplementation(() => {
+          selectCall++;
+          const chain: Record<string, any> = {};
+          chain.from = vi.fn().mockReturnValue(chain);
+          chain.innerJoin = vi.fn().mockReturnValue(chain);
+          chain.where = vi.fn().mockReturnValue(chain);
+          chain.limit = vi.fn().mockImplementation(() => {
+            if (selectCall === 1) return []; // no cache
+            if (selectCall === 2) return [{ id: "b1", name: "BMW" }]; // brand
+            if (selectCall === 3) return [{ brandCount: 0 }]; // subscription (unlimited)
+            return [];
+          });
+          return chain;
+        }),
+        insert: vi.fn().mockImplementation(() => {
+          insertCall++;
+          const insertChain: Record<string, any> = {};
+          insertChain.values = vi.fn().mockReturnValue(insertChain);
+          insertChain.returning = vi.fn().mockImplementation(() => {
+            if (insertCall === 1) return [savedVehicle]; // vehicles upsert
+            return [];
+          });
+          insertChain.onConflictDoNothing = vi.fn().mockReturnValue(insertChain);
+          insertChain.onConflictDoUpdate = vi.fn().mockReturnValue(insertChain);
+          return insertChain;
+        }),
+      };
+
+      const { service, partsCatalogsService, emexService } = createService(db);
+      // PCAT returns 0 cars — not definitive, falls through to EMEX check
+      partsCatalogsService.decodeVin.mockResolvedValue(null);
+      // EMEX returns a single vehicle with a known brand
+      emexService.decodeVinOrCandidates.mockResolvedValue({
+        type: "vehicle",
+        vehicle: emexVehicle,
+      });
+
+      const result = await service.decodeVin("WBAPH5C55BA123456", "u1");
+      expect(result).toEqual(savedVehicle);
+      expect(partsCatalogsService.decodeVin).toHaveBeenCalled();
+      expect(emexService.decodeVinOrCandidates).toHaveBeenCalledWith("WBAPH5C55BA123456");
+    });
   });
 
   describe("getHistory", () => {

apps/api/src/vehicles/vehicles.service.ts

@@ -558,9 +558,10 @@ export class VehiclesService {
 
     if (!earlyPcatDefinitive && !earlyEmexDefinitive) {
       // First completer wasn't definitive — wait for the other one.
-      if (earlyWinner.kind === "pcat" && !emexResolved) {
+      // Always await the other promise (if already resolved, returns immediately).
+      if (earlyWinner.kind === "pcat") {
         emexResult = await emexTimedPromise;
-      } else if (earlyWinner.kind === "emex" && !pcatResolved) {
+      } else if (earlyWinner.kind === "emex") {
         pcatResult = await pcatPromise;
       }
       if (signal?.aborted) return null;