src/controllers/api/loginController.ts

@@ -161,7 +161,16 @@ const createLoginResponse = (
     if (version_compare(buildLabel, "2022.09.06.19.24") >= 0) {
         resp.CrossPlatformAllowed = account.CrossPlatformAllowed;
         resp.HUB = `${myUrlBase}/api/`;
-        resp.MatchmakingBuildId = buildConfig.matchmakingBuildId;
+
+        // On live, the MatchmakingBuildId is a random 64-bit integer, but any string that is unique per build should do the trick.
+        const [year, month, day, hour, minute] = buildLabel.split(".").map(x => parseInt(x));
+        resp.MatchmakingBuildId = (
+            year * 1_00_00_00_00 +
+            month * 1_00_00_00 +
+            day * 1_00_00 +
+            hour * 1_00 +
+            minute
+        ).toString();
     }
     if (version_compare(buildLabel, "2023.04.25.23.40") >= 0) {
         if (version_compare(buildLabel, "2025.08.26.09.49") >= 0) {

src/services/buildConfigService.ts

@@ -5,13 +5,11 @@ import { repoDir } from "../helpers/pathHelper.ts";
 interface IBuildConfig {
     version: string;
     buildLabel: string;
-    matchmakingBuildId: string;
 }
 
 export const buildConfig: IBuildConfig = {
     version: "",
-    buildLabel: "",
-    matchmakingBuildId: ""
+    buildLabel: ""
 };
 
 const buildConfigPath = path.join(repoDir, "static/data/buildConfig.json");

src/types/session.ts

@@ -31,7 +31,7 @@ export interface ISession {
 export interface IFindSessionRequest {
     id?: string;
     originalSessionId?: string;
-    buildId?: number;
+    buildId?: number | bigint;
     gameModeId?: number;
     regionId?: number;
     maxEloDifference?: number;