diff --git a/SVSimLoader/Plugin.cs b/SVSimLoader/Plugin.cs
index 0d5a75d..a6bbd34 100644
--- a/SVSimLoader/Plugin.cs
+++ b/SVSimLoader/Plugin.cs
@@ -18,6 +18,25 @@ namespace SVSimLoader
         {
             Instance = this;
             Log = base.Logger;
+            var instanceRaw = System.Environment.GetEnvironmentVariable("SVSIM_INSTANCE_ID");
+            if (!string.IsNullOrEmpty(instanceRaw) && int.TryParse(instanceRaw, out var instanceId) && instanceId > 0)
+            {
+                SvSimConfig.SecondaryInstance = true;
+                SvSimConfig.InstanceId = instanceId;
+                SvSimConfig.FakeSteamId = 900000UL + (ulong)instanceId;
+                // Ticket must be non-empty, even-length, valid hex (the server HexDecodes it before
+                // the bypass) and DISTINCT per instance (SteamSessionService caches ticket->steamId
+                // and rejects a reused ticket under a different steamId).
+                string hex = SvSimConfig.FakeSteamId.ToString("x");
+                if (hex.Length % 2 == 1) hex = "0" + hex;
+                SvSimConfig.FakeTicket = hex;
+                SvSimConfig.IdentityFilePath =
+                    System.IO.Path.Combine(Paths.ConfigPath, $"svsim-identity-{instanceId}.json");
+                InstanceIdentityStore.Initialize(SvSimConfig.IdentityFilePath);
+                Logger.LogWarning(
+                    $"MULTI-INSTANCE MODE: id={instanceId}, fakeSteamId={SvSimConfig.FakeSteamId}, " +
+                    $"identity file={SvSimConfig.IdentityFilePath}. Single-instance mutex will be skipped.");
+            }
             // Plugin startup logic
             Logger.LogInfo($"Plugin {PluginInfo.PLUGIN_GUID} is loaded!");
             _applicationUrl = Config.Bind("Connection", "ApplicationUrl", "https://utoongaize.shadowverse.jp/shadowverse/",
diff --git a/SVSimLoader/SvSimConfig.cs b/SVSimLoader/SvSimConfig.cs
index a0804af..7712aa8 100644
--- a/SVSimLoader/SvSimConfig.cs
+++ b/SVSimLoader/SvSimConfig.cs
@@ -19,4 +19,11 @@ public static class SvSimConfig
     public static bool ProbeEventSection { get; set; }
     public static string StorySectionIdFilter { get; set; }
     public static bool NukeIdentityOnStartup { get; set; }
+
+    // Multi-instance (same-machine two-client PvP smoke) — driven by the SVSIM_INSTANCE_ID env var.
+    public static bool SecondaryInstance { get; set; }   // true when SVSIM_INSTANCE_ID is set
+    public static int InstanceId { get; set; }            // parsed env value
+    public static string IdentityFilePath { get; set; }   // per-instance identity file
+    public static ulong FakeSteamId { get; set; }         // 900000 + InstanceId
+    public static string FakeTicket { get; set; }         // even-length hex of FakeSteamId
 }