[Staaar0]

Issue

After CS2 Nov 11, 2026 Update, MultiAddonManager crashes the server on the first message it sends to a client. The new signatures don't fix this, because the signatures aren't the cause.

When it happens

• A client connects. The CServerSideClientBase hook sees every message sent to a client.
• A plugin calls AddClientAddon with a refresh through IMultiAddonManager, which crashes in GetAddonSignonStateMessage.

Cause

The update changed the network message system but kept the name NetworkMessagesVersion001:

1. A message type is now a plain record (the name, then a create function), no longer an object with virtual functions. The hook's GetNetMessage()->GetNetMessageInfo() makes a virtual call on that record and crashes.
2. FindNetworkMessagePartial moved from index 14 to 10, and AllocateMessage was removed. GetAddonSignonStateMessage uses both.

Fix

All in src/multiaddonmanager.cpp:

• The hook reads the ID with pData->GetMessageId(). Its index is unchanged and it returns a constant.
• A new AllocateNetMessage helper looks up the type through index 10, checks the name, and calls the record's create function. It returns nullptr on a mismatch.
• The code no longer depends on the SDK's INetworkMessageInternal or NetMessageInfo_t.