Co-op Bug Fix

Mechwarrior 5 Mercenaries Co-op Bug Fix

Engine.ini fix for the cooperative-mode replication overflow issue

⚠ IMPORTANT — BOTH PLAYERS MUST INSTALL THIS ⚠

This configuration file must be installed on BOTH the host AND every client

that connects to the cooperative session. Installing it on only one side will

not resolve bug — both sides must have the file in place.

⚠ ВАЖНО — ОБА ИГРОКА ДОЛЖНЫ УСТАНОВИТЬ ФАЙЛ ⚠

Этот файл необходимо установить и у хоста, и у каждого клиента,

который подключается к кооперативной сессии. Установка только на одной

стороне не устранит проблему — файл должен присутствовать у обоих

Описание доступно на двух языках ниже / Description is available in two languages below

🇬🇧 English

Many players have run into an issue where, during long campaigns, with a large inventory or with many mods installed, a so-called "Co-op bug" would appear. How it manifests: the client could not see the host's mechs, items or money; the client spawned directly in the hangar with no ability to open the menu; when starting some missions the difficulty was shown as Difficulty: 12344545 (or other garbage values), the mission tonnage was not displayed, and the client could not confirm readiness because of a tonnage overrun.

After reading numerous messages on the YAML Discord and elsewhere, users came to the conclusion that the inventory and the large number of items/mechs in it were to blame. There may indeed be inventory-related problems today, but this particular bug is not solved that way.

Testing was performed on an installation loaded to the maximum with mods (around 90 mods). Because of this number of mods, the bug appeared even with an empty inventory whenever the contract board had more than 3 missions on it. I tested a complete inventory clear-out with items stored into a separate file — that did not help, the bug persisted. Only after reading the full save-game file and partially cleaning it up was it possible to reach the final conclusion and identify the root cause of the bug.

The cause is a single hard-coded UE4 limit which has been reduced in this game from 1 MB to 64 KB: when the host sends a replicated property larger than 64 KB (a typical TArray<FMissionBoardEntry> easily exceeds this size), the client discards the bunch in the middle of deserialization and reads garb