diff --git a/Robust.Shared.Maths/Properties/AssemblyInfo.cs b/Robust.Shared.Maths/Properties/AssemblyInfo.cs
index 1609dbc4e..fe5bc30bf 100644
--- a/Robust.Shared.Maths/Properties/AssemblyInfo.cs
+++ b/Robust.Shared.Maths/Properties/AssemblyInfo.cs
@@ -6,4 +6,3 @@
 
 [assembly: InternalsVisibleTo("Robust.Client")]
 [assembly: InternalsVisibleTo("Robust.UnitTesting")]
-[assembly: InternalsVisibleTo("Content.Benchmarks")]
diff --git a/Robust.Shared/ContentPack/AssemblyTypeChecker.Config.cs b/Robust.Shared/ContentPack/AssemblyTypeChecker.Config.cs
index 1be49194d..560b71e75 100644
--- a/Robust.Shared/ContentPack/AssemblyTypeChecker.Config.cs
+++ b/Robust.Shared/ContentPack/AssemblyTypeChecker.Config.cs
@@ -88,6 +88,7 @@ namespace Robust.Shared.ContentPack
             public string SystemAssemblyName = default!;
             public HashSet<VerifierError> AllowedVerifierErrors = default!;
             public List<string> WhitelistedNamespaces = default!;
+            public List<string> AllowedAssemblyPrefixes = default!;
             public Dictionary<string, Dictionary<string, TypeConfig>> Types = default!;
         }
 
diff --git a/Robust.Shared/ContentPack/AssemblyTypeChecker.cs b/Robust.Shared/ContentPack/AssemblyTypeChecker.cs
index e96d2c024..cbd7a9309 100644
--- a/Robust.Shared/ContentPack/AssemblyTypeChecker.cs
+++ b/Robust.Shared/ContentPack/AssemblyTypeChecker.cs
@@ -131,6 +131,16 @@ namespace Robust.Shared.ContentPack
                 return false;
             }
 
+#pragma warning disable RA0004
+            var loadedConfig = _config.Result;
+#pragma warning restore RA0004
+
+            if (!loadedConfig.AllowedAssemblyPrefixes.Any(allowedNamePrefix => asmName.StartsWith(allowedNamePrefix)))
+            {
+                _sawmill.Error($"Assembly name '{asmName}' is not allowed for a content assembly");
+                return false;
+            }
+
             if (VerifyIL)
             {
                 if (!DoVerifyIL(asmName, resolver, peReader, reader))
@@ -179,10 +189,6 @@ namespace Robust.Shared.ContentPack
                 return true;
             }
 
-#pragma warning disable RA0004
-            var loadedConfig = _config.Result;
-#pragma warning restore RA0004
-
             var badRefs = new ConcurrentBag<EntityHandle>();
 
             // We still do explicit type reference scanning, even though the actual whitelists work with raw members.
diff --git a/Robust.Shared/ContentPack/ModLoader.cs b/Robust.Shared/ContentPack/ModLoader.cs
index 57a91d2ef..931c64290 100644
--- a/Robust.Shared/ContentPack/ModLoader.cs
+++ b/Robust.Shared/ContentPack/ModLoader.cs
@@ -93,19 +93,23 @@ namespace Robust.Shared.ContentPack
         {
             var sw = Stopwatch.StartNew();
             Sawmill.Debug("LOADING modules");
-            var files = new Dictionary<string, (ResPath Path, string[] references)>();
+            var files = new Dictionary<string, (ResPath Path, MemoryStream data, string[] references)>();
 
             // Find all modules we want to load.
             foreach (var fullPath in paths)
             {
                 using var asmFile = _res.ContentFileRead(fullPath);
-                var refData = GetAssemblyReferenceData(asmFile);
+                var ms = new MemoryStream();
+                asmFile.CopyTo(ms);
+
+                ms.Position = 0;
+                var refData = GetAssemblyReferenceData(ms);
                 if (refData == null)
                     continue;
 
                 var (asmRefs, asmName) = refData.Value;
 
-                if (!files.TryAdd(asmName, (fullPath, asmRefs)))
+                if (!files.TryAdd(asmName, (fullPath, ms, asmRefs)))
                 {
                     Sawmill.Error("Found multiple modules with the same assembly name " +
                                   $"'{asmName}', A: {files[asmName].Path}, B: {fullPath}.");
@@ -122,10 +126,10 @@ namespace Robust.Shared.ContentPack
 
                 Parallel.ForEach(files, pair =>
                 {
-                    var (name, (path, _)) = pair;
+                    var (name, (_, data, _)) = pair;
 
-                    using var stream = _res.ContentFileRead(path);
-                    if (!typeChecker.CheckAssembly(stream, resolver))
+                    data.Position = 0;
+                    if (!typeChecker.CheckAssembly(data, resolver))
                     {
                         throw new TypeCheckFailedException($"Assembly {name} failed type checks.");
                     }
@@ -137,14 +141,15 @@ namespace Robust.Shared.ContentPack
             var nodes = TopologicalSort.FromBeforeAfter(
                 files,
                 kv => kv.Key,
-                kv => kv.Value.Path,
+                kv => kv.Value,
                 _ => Array.Empty<string>(),
                 kv => kv.Value.references,
                 allowMissing: true); // missing refs would be non-content assemblies so allow that.
 
             // Actually load them in the order they depend on each other.
-            foreach (var path in TopologicalSort.Sort(nodes))
+            foreach (var item in TopologicalSort.Sort(nodes))
             {
+                var (path, memory, _) = item;
                 Sawmill.Debug($"Loading module: '{path}'");
                 try
                 {
@@ -156,9 +161,9 @@ namespace Robust.Shared.ContentPack
                     }
                     else
                     {
-                        using var assemblyStream = _res.ContentFileRead(path);
+                        memory.Position = 0;
                         using var symbolsStream = _res.ContentFileReadOrNull(path.WithExtension("pdb"));
-                        LoadGameAssembly(assemblyStream, symbolsStream, skipVerify: true);
+                        LoadGameAssembly(memory, symbolsStream, skipVerify: true);
                     }
                 }
                 catch (Exception e)
@@ -174,7 +179,7 @@ namespace Robust.Shared.ContentPack
 
         private (string[] refs, string name)? GetAssemblyReferenceData(Stream stream)
         {
-            using var reader = ModLoader.MakePEReader(stream);
+            using var reader = ModLoader.MakePEReader(stream, leaveOpen: true);
             var metaReader = reader.GetMetadataReader();
 
             var name = metaReader.GetString(metaReader.GetAssemblyDefinition().Name);
diff --git a/Robust.Shared/ContentPack/Sandbox.yml b/Robust.Shared/ContentPack/Sandbox.yml
index 63b10a3f6..7963e2c59 100644
--- a/Robust.Shared/ContentPack/Sandbox.yml
+++ b/Robust.Shared/ContentPack/Sandbox.yml
@@ -17,6 +17,10 @@ WhitelistedNamespaces:
 - Content
 - OpenDreamShared
 
+AllowedAssemblyPrefixes:
+- OpenDream
+- Content
+
 # The type whitelist does NOT care about which assembly types come from.
 # This is because types switch assembly all the time.
 # Just look up stuff like StreamReader on https://apisof.net.
diff --git a/Robust.Shared/Properties/AssemblyInfo.cs b/Robust.Shared/Properties/AssemblyInfo.cs
index ca50911fc..86e9a1fad 100644
--- a/Robust.Shared/Properties/AssemblyInfo.cs
+++ b/Robust.Shared/Properties/AssemblyInfo.cs
@@ -9,7 +9,6 @@
 [assembly: InternalsVisibleTo("Robust.UnitTesting")]
 [assembly: InternalsVisibleTo("OpenToolkit.GraphicsLibraryFramework")]
 [assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")] // Gives access to Castle(Moq)
-[assembly: InternalsVisibleTo("Content.Benchmarks")]
 [assembly: InternalsVisibleTo("Robust.Benchmarks")]
 [assembly: InternalsVisibleTo("Robust.Client.WebView")]
 [assembly: InternalsVisibleTo("Robust.Packaging")]