csRestrict

Server-side Fabric mod for Minecraft 26.2, built for Project Nodenium.

What it does

Stops non-operator players from using spectator mode (entered via Carpet's /cs command, or any other means) to instantly jump to and view real players' bases. Carpet fake players (bots) are unaffected.

/cs itself still works, and a restricted spectator can still fly around normally. Only the vanilla "click a player's name to teleport your camera to them" feature is blocked, and only against real players.

How it works

1. Teleport block - the spectator "jump to player" feature sends a ServerboundTeleportToEntityPacket which the server resolves and uses to physically teleport the requester. A mixin on ServerGamePacketListenerImpl#handleTeleportToEntityPacket cancels this specific packet when the requester is a non-op player currently in spectator mode and the resolved target is a real player (not a Carpet fake player).
2. Tab list hiding - as a belt-and-suspenders measure, a mixin filters outgoing ClientboundPlayerInfoUpdatePackets so restricted spectators never see real players listed in their tab list at all (Carpet bots and their own entry are never hidden).
3. Tab list sync - entering or leaving restricted mode pushes a corrective packet (removing already-known real players, or resending the full list on exit) so nothing is left showing a stale gamemode or tab-list entry from before the transition.
4. Command detection - a mixin on handleChatCommand logs (debug level) whenever a player runs a "watched" command (cs by default, configurable in config/csrestrict.json). This is diagnostic only; the actual restriction is based on live gamemode + op state, not the literal command name, so it can't be bypassed by renaming or aliasing the Carpet script.

Whether a player is currently restricted is evaluated live, every time, from their actual gamemode and op status (ServerPlayer#isSpectator() and PlayerList#isOp) - not cached. The only stored state is a small per-player flag used solely to detect the enter/exit transition for step 3.

Carpet fake players are detected via a soft dependency (no compile/runtime dependency on fabric-carpet): by exact class name (carpet.patches.EntityPlayerMPFake) and, as a fallback for forks that relocate the package, by the presence of Carpet's isAShadow marker field.

Building

Requires JDK 25.

./gradlew build

The built jar is in build/libs/csrestrict-1.0.1.jar.

Installing

Drop the jar into the server's mods/ folder alongside Fabric API 0.160.0+26.2 (or newer for 26.2) and Fabric Loader 0.19.5+. It's server-side only ("environment": "server" in fabric.mod.json) - no client installation needed.

Configuration

config/csrestrict.json is created on first run:

{
  "watchedCommands": ["cs"]
}

Add extra command names/aliases here if the server renames or adds alternate ways to trigger the same script; this only changes what gets logged, not what gets blocked.