Client mods policy

How Stratum decides which client mods a player may join with, and how to turn the policy on.

Players connect with the normal Vintage Story client. Some client mods change what a player sees or sends, and a server may want to allow only a known set of them. Stratum’s client mods policy checks the mods a player joins with against a whitelist.

The policy is off by default. Nothing is checked until you turn it on.

Turn it on

Set ClientModPolicy.Enabled to true in stratum.json, or use:

/stratum set ClientModPolicy.Enabled true

Before you enable it, collect the mod IDs your players already use. Ask each player to copy the modid value from each mod’s modinfo.json. Use the ID, not the mod’s display name. With the policy enabled, the client disables unlisted client and universal mods for that session and can still join. This is a client-side convenience control, not an anticheat; a modified client can ignore the list.

How the whitelist works

With StrictWhitelist at true (the default), Stratum sends its allow list to the client. The stock client disables client and universal mods that do not match an entry, then continues joining. With StrictWhitelist at false, Stratum sends no replacement list and the vanilla ModIdWhiteList and ModIdBlackList settings apply unchanged. When the Stratum policy is active, the vanilla allow list is merged into its list, but the vanilla deny list is no longer sent.

The core Vintage Story mods game, creative, and survival are always allowed. Matching is a case-sensitive substring check against modid@version, so examplemod also matches myexamplemod2, while ExampleMod does not match examplemod. Add @version to pin an entry, such as examplemod@1.2.3. Server-only client mods are not checked.

IncludeServerUniversalMods is true by default. It adds the mods the server marks as universal to the whitelist as modid@version entries, so you do not need to list them by hand.

AllowModIds is a list of extra entries added to the whitelist. Each entry is used as you write it, with spaces at the ends removed. The list is empty by default.

For example, if the mod’s modid is examplemod, add that ID:

{
  "ClientModPolicy": {
    "AllowModIds": ["examplemod"]
  }
}

Merge this object into the top level of stratum.json and keep its existing settings. A server universal mod is already allowed when IncludeServerUniversalMods is true.

Config

In stratum.json, under ClientModPolicy:

Key	Default	Effect
`ClientModPolicy.Enabled`	`false`	Turns the policy on.
`ClientModPolicy.StrictWhitelist`	`true`	Sends Stratum’s allow list to the client. Set to `false` to leave the vanilla allow and deny lists unchanged.
`ClientModPolicy.IncludeServerUniversalMods`	`true`	Allows the mods the server marks as universal.
`ClientModPolicy.AllowModIds`	`[]`	Extra mod IDs to allow.
`ClientModPolicy.LogPolicyOnStartup`	`true`	Logs the policy state and allow-list entry count at startup.

Roll it out safely

Keep Enabled set to false while you collect IDs. Add the IDs you intend to allow, then enable the policy during a test session or maintenance window. Edit AllowModIds in stratum.json, since lists cannot be changed with /stratum set. Run /stratum reload to apply the change for the next join. Test with one client that has an allowed mod and one with an unlisted mod. The first should join with the mod enabled; the second should join with that mod disabled. If a player needs another mod, add its ID and reload.