diff --git a/Content.Client/RCD/RCDMenu.xaml.cs b/Content.Client/RCD/RCDMenu.xaml.cs
index 51ec66ea444..3eb0397a690 100644
--- a/Content.Client/RCD/RCDMenu.xaml.cs
+++ b/Content.Client/RCD/RCDMenu.xaml.cs
@@ -68,7 +68,7 @@ public RCDMenu(EntityUid owner, RCDMenuBoundUserInterface bui)
                 tooltip = Loc.GetString(entProto.Name);
             }
 
-            tooltip = char.ToUpper(tooltip[0]) + tooltip.Remove(0, 1);
+            tooltip = OopsConcat(char.ToUpper(tooltip[0]).ToString(), tooltip.Remove(0, 1));
 
             var button = new RCDMenuButton()
             {
@@ -119,6 +119,12 @@ public RCDMenu(EntityUid owner, RCDMenuBoundUserInterface bui)
         SendRCDSystemMessageAction += bui.SendRCDSystemMessage;
     }
 
+    private static string OopsConcat(string a, string b)
+    {
+        // This exists to prevent Roslyn being clever and compiling something that fails sandbox checks.
+        return a + b;
+    }
+
     private void AddRCDMenuButtonOnClickActions(Control control)
     {
         var radialContainer = control as RadialContainer;
diff --git a/Content.Server.Database/Model.cs b/Content.Server.Database/Model.cs
index b6ca9d95d0b..eab62702ffe 100644
--- a/Content.Server.Database/Model.cs
+++ b/Content.Server.Database/Model.cs
@@ -881,6 +881,7 @@ public enum ConnectionDenyReason : byte
         Whitelist = 1,
         Full = 2,
         Panic = 3,
+        Connected = 4,
     }
 
     public class ServerBanHit
diff --git a/Content.Server/Administration/ServerApi.cs b/Content.Server/Administration/ServerApi.cs
index 04fd38598fb..2f7bcbe48e2 100644
--- a/Content.Server/Administration/ServerApi.cs
+++ b/Content.Server/Administration/ServerApi.cs
@@ -67,7 +67,7 @@ void IPostInjectInit.PostInject()
         _sawmill = _logManager.GetSawmill("serverApi");
 
         // Get
-        RegisterActorHandler(HttpMethod.Get, "/admin/info", InfoHandler);
+        RegisterHandler(HttpMethod.Get, "/admin/info", InfoHandler); //frontier - not sure why this action needs an actor
         RegisterHandler(HttpMethod.Get, "/admin/game_rules", GetGameRules);
         RegisterHandler(HttpMethod.Get, "/admin/presets", GetPresets);
 
@@ -452,7 +452,7 @@ await context.RespondJsonAsync(new GameruleResponse
     /// <summary>
     ///     Handles fetching information.
     /// </summary>
-    private async Task InfoHandler(IStatusHandlerContext context, Actor actor)
+    private async Task InfoHandler(IStatusHandlerContext context) //frontier - we had an actor here and never used it so we drop it for now until im compelled to re-add it
     {
         /*
         Information to display
diff --git a/Content.Server/Connection/ConnectionManager.cs b/Content.Server/Connection/ConnectionManager.cs
index cd89f48d49f..4b57aa66157 100644
--- a/Content.Server/Connection/ConnectionManager.cs
+++ b/Content.Server/Connection/ConnectionManager.cs
@@ -2,6 +2,8 @@
 using System.Runtime.InteropServices;
 using System.Text.Json.Nodes;
 using System.Threading.Tasks;
+using Content.Server._NF.Auth;
+using Content.Server.Administration;
 using Content.Server.Database;
 using Content.Server.GameTicking;
 using Content.Server.Preferences.Managers;
@@ -48,6 +50,9 @@ public sealed class ConnectionManager : IConnectionManager
         [Dependency] private readonly IGameTiming _gameTiming = default!;
         [Dependency] private readonly ILogManager _logManager = default!;
 
+        //frontier
+        [Dependency] private readonly MiniAuthManager _authManager = default!;
+
         private readonly Dictionary<NetUserId, TimeSpan> _temporaryBypasses = [];
         private ISawmill _sawmill = default!;
 
@@ -228,6 +233,21 @@ private async Task NetMgrOnConnecting(NetConnectingArgs e)
                 }
             }
 
+            //Frontier
+            //This is our little chunk that serves as a dAuth. It takes in a comma seperated list of IP:PORT, and chekcs
+            //the requesting player against the list of players logged in to other servers. It is intended to be failsafe.
+            //In the case of Admins, it shares the same bypass setting as the soft_max_player_limit
+            if (!_cfg.GetCVar(CCVars.AllowMultiConnect) && !adminBypass)
+            {
+                var serverListString = _cfg.GetCVar(CCVars.ServerAuthList);
+                var serverList = serverListString.Split(",");
+                foreach (var server in serverList)
+                {
+                    if (await _authManager.IsPlayerConnected(server, userId))
+                        return (ConnectionDenyReason.Connected, Loc.GetString("multiauth-already-connected"), null);
+                }
+            }
+            // end Frontier
             return null;
         }
 
diff --git a/Content.Server/Entry/EntryPoint.cs b/Content.Server/Entry/EntryPoint.cs
index 3cdf3bfe8e2..4c43670a053 100644
--- a/Content.Server/Entry/EntryPoint.cs
+++ b/Content.Server/Entry/EntryPoint.cs
@@ -1,3 +1,4 @@
+using Content.Server._NF.Auth;
 using Content.Server.Acz;
 using Content.Server.Administration;
 using Content.Server.Administration.Logs;
@@ -103,6 +104,7 @@ public override void Init()
                 IoCManager.Resolve<GhostKickManager>().Initialize();
                 IoCManager.Resolve<ServerInfoManager>().Initialize();
                 IoCManager.Resolve<ServerApi>().Initialize();
+                IoCManager.Resolve<MiniAuthManager>();
 
                 _voteManager.Initialize();
                 _updateManager.Initialize();
diff --git a/Content.Server/IoC/ServerContentIoC.cs b/Content.Server/IoC/ServerContentIoC.cs
index f6800f72890..8bd866a20d3 100644
--- a/Content.Server/IoC/ServerContentIoC.cs
+++ b/Content.Server/IoC/ServerContentIoC.cs
@@ -1,3 +1,4 @@
+using Content.Server._NF.Auth;
 using Content.Server.Administration;
 using Content.Server.Administration.Logs;
 using Content.Server.Administration.Managers;
@@ -61,6 +62,8 @@ public static void Register()
             IoCManager.Register<ServerDbEntryManager>();
             IoCManager.Register<ISharedPlaytimeManager, PlayTimeTrackingManager>();
             IoCManager.Register<ServerApi>();
+            IoCManager.Register<MiniAuthManager>(); //Frontier
+
         }
     }
 }
diff --git a/Content.Server/_NF/Auth/Auth.cs b/Content.Server/_NF/Auth/Auth.cs
new file mode 100644
index 00000000000..8ec682d07bc
--- /dev/null
+++ b/Content.Server/_NF/Auth/Auth.cs
@@ -0,0 +1,88 @@
+using System.Net;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Net.Http;
+using System.Net.Http.Json;
+using System.Net.Http.Headers;
+using Content.Shared.CCVar;
+using Robust.Shared.Configuration;
+using JetBrains.Annotations;
+
+namespace Content.Server._NF.Auth;
+
+public sealed class MiniAuthManager
+{
+    [Dependency] private readonly IConfigurationManager _cfg = default!;
+
+    private readonly HttpClient _http = new();
+
+    /// <summary>
+    /// Frontier function to ping a server and check to see if the given player is currently connected to the given server.
+    /// Servers using this function must share an admin_api token as defined in their respective server_config.toml
+    /// </summary>
+    /// <param name="address">The address of the server to ping.</param>
+    /// <param name="player">the GUID of the player to check for connection.</param>
+    /// <returns>True if the response from the server is successful and the player is connected. False in any case of error, timeout, or failure.</returns>
+    public async Task<bool> IsPlayerConnected(string address, Guid player)
+    {
+        var connected = false;
+        var statusAddress = "http://" + address + "/admin/info";
+
+        var cancel = new CancellationToken();
+        var linkedToken = CancellationTokenSource.CreateLinkedTokenSource(cancel);
+        linkedToken.CancelAfter(TimeSpan.FromSeconds(10));
+
+        _http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("SS14Token", _cfg.GetCVar(CCVars.AdminApiToken));
+
+        //We need to do a try catch here because theres essentially no way to guarantee our json response is proper.
+        //Throughout all of this, we want it to fail to deny, not fail to allow, so if any step of our auth goes wrong,
+        //people can still connect.
+        try
+        {
+            var status = await _http.GetFromJsonAsync<InfoResponse>(statusAddress, linkedToken.Token);
+
+            foreach (var connectedPlayer in status!.Players)
+            {
+                if (connectedPlayer.UserId == player)
+                {
+                    connected = true;
+                    break;
+                }
+            }
+        }
+        catch (Exception e)
+        {
+        }
+        return connected;
+    }
+
+    /// <summary>
+    /// Record used to send the response for the info endpoint.
+    /// Frontier - This is a direct copy of ServerAPI.InfoResponse to match the json format. they kept it private so i just copied it
+    /// </summary>
+    [UsedImplicitly]
+    private sealed record InfoResponse
+    {
+        public required int RoundId { get; init; }
+        public required List<Player> Players { get; init; }
+        public required List<string> GameRules { get; init; }
+        public required string? GamePreset { get; init; }
+        public required MapInfo? Map { get; init; }
+        public required string? MOTD { get; init; }
+        public required Dictionary<string, object> PanicBunker { get; init; }
+
+        public sealed class Player
+        {
+            public required Guid UserId { get; init; }
+            public required string Name { get; init; }
+            public required bool IsAdmin { get; init; }
+            public required bool IsDeadminned { get; init; }
+        }
+
+        public sealed class MapInfo
+        {
+            public required string Id { get; init; }
+            public required string Name { get; init; }
+        }
+    }
+}
diff --git a/Content.Shared/CCVar/CCVars.cs b/Content.Shared/CCVar/CCVars.cs
index 4d9a704f521..a80567d0173 100644
--- a/Content.Shared/CCVar/CCVars.cs
+++ b/Content.Shared/CCVar/CCVars.cs
@@ -2045,6 +2045,11 @@ public static readonly CVarDef<float>
         public static readonly CVarDef<string> TippyEntity =
             CVarDef.Create("tippy.entity", "TippyClippy", CVar.SERVER | CVar.REPLICATED); // Frontier - Tippy<TippyClippy
 
+        public static readonly CVarDef<string> ServerAuthList =
+            CVarDef.Create("frontier.auth_servers", "", CVar.CONFIDENTIAL | CVar.SERVERONLY);
+
+        public static readonly CVarDef<bool> AllowMultiConnect =
+            CVarDef.Create("frontier.allow_multi_connect", true, CVar.CONFIDENTIAL | CVar.SERVERONLY);
         /*
          * DEBUG
          */
diff --git a/Content.Shared/Chat/SharedChatSystem.cs b/Content.Shared/Chat/SharedChatSystem.cs
index e61d93efaeb..4f0b1465cd2 100644
--- a/Content.Shared/Chat/SharedChatSystem.cs
+++ b/Content.Shared/Chat/SharedChatSystem.cs
@@ -152,10 +152,16 @@ public string SanitizeMessageCapital(string message)
         if (string.IsNullOrEmpty(message))
             return message;
         // Capitalize first letter
-        message = char.ToUpper(message[0]) + message.Remove(0, 1);
+        message = OopsConcat(char.ToUpper(message[0]).ToString(), message.Remove(0, 1));
         return message;
     }
 
+    private static string OopsConcat(string a, string b)
+    {
+        // This exists to prevent Roslyn being clever and compiling something that fails sandbox checks.
+        return a + b;
+    }
+
     public string SanitizeMessageCapitalizeTheWordI(string message, string theWordI = "i")
     {
         if (string.IsNullOrEmpty(message))
diff --git a/Resources/Locale/en-US/_NF/adventure/adventure.ftl b/Resources/Locale/en-US/_NF/adventure/adventure.ftl
index 02872d0e3ae..a6fbf130949 100644
--- a/Resources/Locale/en-US/_NF/adventure/adventure.ftl
+++ b/Resources/Locale/en-US/_NF/adventure/adventure.ftl
@@ -21,6 +21,7 @@ shipyard-rules-default2 =
 shuttle-ftl-proximity = Nearby objects too massive for FTL!
 
 changelog-tab-title-Upstream = Upstream Changelog
+multiauth-already-connected = Already connected to Frontier Official servers.
 
 public-transit-departure = Now departing for {$destination}. Estimated travel time: {$flytime} seconds.
 public-transit-arrival = Thank you for choosing NT Public Transit. Next transfer to {$destination} departs in {$waittime} seconds.
\ No newline at end of file