diff --git a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
index cc378dcc8872a..db8416cf5ddd1 100644
--- a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
+++ b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
@@ -280,6 +280,7 @@ public static bool IsMetadataTokenSupported
         // Changed to `true` when trimming
         public static bool IsBuiltWithAggressiveTrimming => IsNativeAot;
         public static bool IsNotBuiltWithAggressiveTrimming => !IsBuiltWithAggressiveTrimming;
+        public static bool IsTrimmedWithILLink => IsBuiltWithAggressiveTrimming && !IsNativeAot;
 
         // Windows - Schannel supports alpn from win8.1/2012 R2 and higher.
         // Linux - OpenSsl supports alpn from openssl 1.0.2 and higher.
diff --git a/src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj b/src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj
index 03138144a9db7..0ad5f15337a6e 100644
--- a/src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj
+++ b/src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj
@@ -72,19 +72,20 @@
     <TrimmerRootDescriptor Include="$(MSBuildThisFileDirectory)ILLink.Descriptors.xml" />
   </ItemGroup>
 
-  <Target Name="PreserveEnCAssembliesFromLinking" Condition="'$(TargetOS)' == 'browser' and '$(EnableAggressiveTrimming)' == 'true'" BeforeTargets="ConfigureTrimming">
+  <Target Name="PreserveEnCAssembliesFromLinking" Condition="'$(TargetOS)' == 'browser' and '$(EnableAggressiveTrimming)' == 'true'" BeforeTargets="PrepareForILLink">
     <ItemGroup>
-      <!-- want to compute the intersection: apply update test assemblies that are also resolved to publish.
+      <!-- want to compute the intersection: apply update test assemblies that are also resolved to link.
         -->
       <ApplyUpdateTestProjectReference Include="@(ProjectReference)" Condition="$([System.String]::new('%(FileName)').StartsWith('$(ApplyUpdateTestPrefix)'))" />
       <ApplyUpdateTestAssemblyName Include="@(ApplyUpdateTestProjectReference->'%(FileName).dll')" />
-      <ResolvedFileToPublishNoDirName Include="%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)">
-        <ResolvedFileToPublish>%(ResolvedFileToPublish.FullPath)</ResolvedFileToPublish>
-      </ResolvedFileToPublishNoDirName>
-      <ResolvedApplyUpdateAssembly Include="@(ResolvedFileToPublishNoDirName)" Condition="'@(ResolvedFileToPublishNoDirName)' == '@(ApplyUpdateTestAssemblyName)' and %(Identity) != ''" />
       <!-- Don't let the IL linker modify EnC test assemblies -->
-      <TrimmerRootAssembly Include="%(ResolvedApplyUpdateAssembly.ResolvedFileToPublish)" />
-    </ItemGroup>
+      <ManagedAssemblyToLink Condition="'%(FileName)%(Extension)' == '@(ApplyUpdateTestAssemblyName)'">
+        <TrimMode>copy</TrimMode>
+      </ManagedAssemblyToLink>
+      <ManagedAssemblyToLink Condition="'%(FileName)%(Extension)' == '@(IntermediateAssembly->'%(FileName)%(Extension)')'">
+        <TrimMode>copy</TrimMode>
+      </ManagedAssemblyToLink>
+    </ItemGroup> 
   </Target>
 
   <Target Name="IncludeDeltasInWasmBundle" BeforeTargets="PrepareForWasmBuildApp" Condition="'$(TargetOS)' == 'browser'">
diff --git a/src/libraries/System.Runtime/tests/System.Reflection.Tests/MemberInfoTests.cs b/src/libraries/System.Runtime/tests/System.Reflection.Tests/MemberInfoTests.cs
index e30d8f8a16bd1..411d947e7405a 100644
--- a/src/libraries/System.Runtime/tests/System.Reflection.Tests/MemberInfoTests.cs
+++ b/src/libraries/System.Runtime/tests/System.Reflection.Tests/MemberInfoTests.cs
@@ -166,7 +166,8 @@ public void MethodInfoReflectedTypeDoesNotSurviveRuntimeHandles()
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtimelab/issues/830", typeof(PlatformDetection), nameof(PlatformDetection.IsNativeAot))]
+        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsBuiltWithAggressiveTrimming)),
+            /* Stripping ComVisible because descriptors tell us so */]
         public void GetCustomAttributesData()
         {
             MemberInfo[] m = typeof(MemberInfoTests).GetMember("SampleClass");
diff --git a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj
index ca223dc873277..6514d08c8f284 100644
--- a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj
+++ b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj
@@ -14,6 +14,8 @@
 
     <!-- The test is looking for debugger attributes we would have stripped with NativeAOT -->
     <IlcKeepManagedDebuggerSupport>true</IlcKeepManagedDebuggerSupport>
+    <!-- Same for ILLink -->
+    <DebuggerSupport>true</DebuggerSupport>
   </PropertyGroup>
 
   <!--
diff --git a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/AttributeTests.cs b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/AttributeTests.cs
index 2484d1b9ac81c..6774195fa52ff 100644
--- a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/AttributeTests.cs
+++ b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/AttributeTests.cs
@@ -154,7 +154,7 @@ class ChildAttributeWithField : ParentAttribute
             public int Field = 0;
         }
 
-        [ActiveIssue("https://github.com/dotnet/runtimelab/issues/803", typeof(PlatformDetection), nameof(PlatformDetection.IsNativeAot))]
+        [ActiveIssue("https://github.com/dotnet/runtimelab/issues/803", typeof(PlatformDetection), nameof(PlatformDetection.IsBuiltWithAggressiveTrimming))]
         [Fact]
         [StringValue("\uDFFF")]
         public static void StringArgument_InvalidCodeUnits_FallbackUsed()
diff --git a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Attributes.cs b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Attributes.cs
index 0b75b48ea133e..61c10f947946a 100644
--- a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Attributes.cs
+++ b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Attributes.cs
@@ -44,7 +44,8 @@ public void TestIsDefined()
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsNativeAot) /* Stripping ComVisible because descriptors tell us so */)]
+        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsBuiltWithAggressiveTrimming)
+            /* Stripping ComVisible because descriptors tell us so */)]
         public void IsDefined_PropertyInfo()
         {
             PropertyInfo pi = typeof(TestBase).GetProperty("PropBase3");
@@ -327,6 +328,8 @@ public static class GetCustomAttribute
     {
 
         [Fact]
+        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsTrimmedWithILLink))
+            /* Stripping security attributes removes UnverifiableCodeAttribute */]
         public static void customAttributeCount()
         {
             List<CustomAttributeData> customAttributes = typeof(GetCustomAttribute).Module.CustomAttributes.ToList();
diff --git a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/CustomAttributeDataTests.cs b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/CustomAttributeDataTests.cs
index b46084e523d43..ddd5939ed0431 100644
--- a/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/CustomAttributeDataTests.cs
+++ b/src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Reflection/CustomAttributeDataTests.cs
@@ -75,7 +75,8 @@ public static void Test_CustomAttribute_Constructor_CrossAssembly1()
 
         [Fact]
         [ComVisible(false)]
-        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsNativeAot)) /* Descriptors tell us to remove ComVisibleAttribute */]
+        [ActiveIssue("https://github.com/dotnet/linker/issues/2078", typeof(PlatformDetection), nameof(PlatformDetection.IsBuiltWithAggressiveTrimming))
+            /* Descriptors tell us to remove ComVisibleAttribute */]
         public static void Test_CustomAttribute_Constructor_CrossAssembly2()
         {
             MethodInfo m = (MethodInfo)MethodBase.GetCurrentMethod();
diff --git a/src/tools/illink/src/linker/CompatibilitySuppressions.xml b/src/tools/illink/src/linker/CompatibilitySuppressions.xml
index 1e9b7f7c998d0..1dd110c02eea6 100644
--- a/src/tools/illink/src/linker/CompatibilitySuppressions.xml
+++ b/src/tools/illink/src/linker/CompatibilitySuppressions.xml
@@ -1147,6 +1147,12 @@
     <Left>ref/net8.0/illink.dll</Left>
     <Right>lib/net8.0/illink.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Mono.Linker.AnnotationStore.IsRootAssembly(Mono.Cecil.AssemblyDefinition)</Target>
+    <Left>ref/net8.0/illink.dll</Left>
+    <Right>lib/net8.0/illink.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Mono.Linker.AnnotationStore.Mark(Mono.Cecil.CustomAttribute,Mono.Linker.DependencyInfo@)</Target>
@@ -1243,6 +1249,12 @@
     <Left>ref/net8.0/illink.dll</Left>
     <Right>lib/net8.0/illink.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Mono.Linker.AnnotationStore.SetRootAssembly(Mono.Cecil.AssemblyDefinition)</Target>
+    <Left>ref/net8.0/illink.dll</Left>
+    <Right>lib/net8.0/illink.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Mono.Linker.AnnotationStore.SetSubstitutedInit(Mono.Cecil.TypeDefinition)</Target>
diff --git a/src/tools/illink/src/linker/Linker.Steps/MarkStep.cs b/src/tools/illink/src/linker/Linker.Steps/MarkStep.cs
index 76768d00551cb..da4dc455f0abc 100644
--- a/src/tools/illink/src/linker/Linker.Steps/MarkStep.cs
+++ b/src/tools/illink/src/linker/Linker.Steps/MarkStep.cs
@@ -153,6 +153,7 @@ internal DynamicallyAccessedMembersTypeHierarchy DynamicallyAccessedMembersTypeH
 			DependencyKind.InterfaceImplementationInterfaceType,
 			DependencyKind.Ldtoken,
 			DependencyKind.ModifierType,
+			DependencyKind.NestedType,
 			DependencyKind.InstructionTypeRef,
 			DependencyKind.ParameterType,
 			DependencyKind.ReferencedBySpecialAttribute,
@@ -373,7 +374,7 @@ internal void MarkEntireType (TypeDefinition type, in DependencyInfo reason)
 					MarkEntireType (nested, new DependencyInfo (DependencyKind.NestedType, type));
 			}
 
-			Annotations.Mark (type, reason, ScopeStack.CurrentScope.Origin);
+			MarkTypeVisibleToReflection (type, type, reason, ScopeStack.CurrentScope.Origin);
 			MarkCustomAttributes (type, new DependencyInfo (DependencyKind.CustomAttribute, type));
 			MarkTypeSpecialCustomAttributes (type);
 
@@ -386,26 +387,27 @@ internal void MarkEntireType (TypeDefinition type, in DependencyInfo reason)
 
 			if (type.HasFields) {
 				foreach (FieldDefinition field in type.Fields) {
-					MarkField (field, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
+					MarkFieldVisibleToReflection (field, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
 				}
 			}
 
 			if (type.HasMethods) {
 				foreach (MethodDefinition method in type.Methods) {
-					Annotations.SetAction (method, MethodAction.ForceParse);
-					MarkMethod (method, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
+					if (IsFullyPreservedAction (Annotations.GetAction (type.Module.Assembly)))
+						Annotations.SetAction (method, MethodAction.ForceParse);
+					MarkMethodVisibleToReflection (method, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
 				}
 			}
 
 			if (type.HasProperties) {
 				foreach (var property in type.Properties) {
-					MarkProperty (property, new DependencyInfo (DependencyKind.MemberOfType, type));
+					MarkPropertyVisibleToReflection (property, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
 				}
 			}
 
 			if (type.HasEvents) {
 				foreach (var ev in type.Events) {
-					MarkEvent (ev, new DependencyInfo (DependencyKind.MemberOfType, type));
+					MarkEventVisibleToReflection (ev, new DependencyInfo (DependencyKind.MemberOfType, type), ScopeStack.CurrentScope.Origin);
 				}
 			}
 		}
@@ -1422,6 +1424,8 @@ protected virtual void MarkAssembly (AssemblyDefinition assembly, DependencyInfo
 					MarkEntireAssembly (assembly);
 				}
 				return;
+			} else if (Annotations.IsRootAssembly (assembly)) {
+				MarkEntireAssembly (assembly);
 			}
 
 			ProcessModuleType (assembly);
@@ -2033,7 +2037,9 @@ internal void MarkStaticConstructorVisibleToReflection (TypeDefinition type, in
 				// will call MarkType on the attribute type itself).
 				// If for some reason we do keep the attribute type (could be because of previous reference which would cause IL2045
 				// or because of a copy assembly with a reference and so on) then we should not spam the warnings due to the type itself.
-				if (!(reason.Source is IMemberDefinition sourceMemberDefinition && sourceMemberDefinition.DeclaringType == type))
+				// Also don't warn when the type is marked due to an assembly being rooted.
+				if (!(reason.Source is IMemberDefinition sourceMemberDefinition && sourceMemberDefinition.DeclaringType == type) &&
+					reason.Kind is not DependencyKind.TypeInAssembly)
 					Context.LogWarning (ScopeStack.CurrentScope.Origin, DiagnosticId.AttributeIsReferencedButTrimmerRemoveAllInstances, type.GetDisplayName ());
 			}
 
diff --git a/src/tools/illink/src/linker/Linker.Steps/RootAssemblyInputStep.cs b/src/tools/illink/src/linker/Linker.Steps/RootAssemblyInputStep.cs
index 2752ebc7dd472..d29432e8b60ce 100644
--- a/src/tools/illink/src/linker/Linker.Steps/RootAssemblyInputStep.cs
+++ b/src/tools/illink/src/linker/Linker.Steps/RootAssemblyInputStep.cs
@@ -87,7 +87,8 @@ protected override void Process ()
 				Context.MetadataTrimming = MetadataTrimming.None;
 				break;
 			case AssemblyRootMode.AllMembers:
-				Context.Annotations.SetAction (assembly, AssemblyAction.Copy);
+				Annotations.SetRootAssembly (assembly);
+				Annotations.Mark (assembly.MainModule, di, origin);
 				return;
 			}
 		}
diff --git a/src/tools/illink/src/linker/Linker.Steps/UnreachableBlocksOptimizer.cs b/src/tools/illink/src/linker/Linker.Steps/UnreachableBlocksOptimizer.cs
index d9fd14c5c9a5e..295d740874cb9 100644
--- a/src/tools/illink/src/linker/Linker.Steps/UnreachableBlocksOptimizer.cs
+++ b/src/tools/illink/src/linker/Linker.Steps/UnreachableBlocksOptimizer.cs
@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
@@ -1583,7 +1583,7 @@ public bool Analyze (in CalleePayload callee, Stack<MethodDefinition> callStack)
 								return false;
 
 							if (operand is int oint) {
-								if (oint == 1)
+								if (oint != 0)
 									jmpTarget = (Instruction) instr.Operand;
 
 								continue;
diff --git a/src/tools/illink/src/linker/Linker/Annotations.cs b/src/tools/illink/src/linker/Linker/Annotations.cs
index 5185314b9d3da..ec507ea25c0a5 100644
--- a/src/tools/illink/src/linker/Linker/Annotations.cs
+++ b/src/tools/illink/src/linker/Linker/Annotations.cs
@@ -59,6 +59,7 @@ public partial class AnnotationStore
 		protected readonly Dictionary<TypeDefinition, TypePreserveMembers> preserved_type_members = new ();
 		protected readonly Dictionary<ExportedType, TypePreserveMembers> preserved_exportedtype_members = new ();
 		protected readonly Dictionary<IMemberDefinition, List<MethodDefinition>> preserved_methods = new Dictionary<IMemberDefinition, List<MethodDefinition>> ();
+		readonly HashSet<AssemblyDefinition> assemblies_with_root_all_members = new ();
 		protected readonly HashSet<IMetadataTokenProvider> public_api = new HashSet<IMetadataTokenProvider> ();
 		protected readonly Dictionary<AssemblyDefinition, ISymbolReader> symbol_readers = new Dictionary<AssemblyDefinition, ISymbolReader> ();
 		readonly Dictionary<IMemberDefinition, LinkerAttributesInformation> linker_attributes = new Dictionary<IMemberDefinition, LinkerAttributesInformation> ();
@@ -399,6 +400,16 @@ public bool TryGetPreservedMembers (ExportedType type, out TypePreserveMembers p
 			return preserved_exportedtype_members.TryGetValue (type, out preserve);
 		}
 
+		public void SetRootAssembly (AssemblyDefinition assembly)
+		{
+			assemblies_with_root_all_members.Add (assembly);
+		}
+
+		public bool IsRootAssembly (AssemblyDefinition assembly)
+		{
+			return assemblies_with_root_all_members.Contains (assembly);
+		}
+
 		public bool TryGetMethodStubValue (MethodDefinition method, out object? value)
 		{
 			return MemberActions.TryGetMethodStubValue (method, out value);
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases.Expectations/Metadata/SetupLinkerLinkAllAttribute.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases.Expectations/Metadata/SetupLinkerLinkAllAttribute.cs
new file mode 100644
index 0000000000000..6596b12677d8a
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases.Expectations/Metadata/SetupLinkerLinkAllAttribute.cs
@@ -0,0 +1,12 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace Mono.Linker.Tests.Cases.Expectations.Metadata
+{
+	[AttributeUsage (AttributeTargets.Class, AllowMultiple = false)]
+	public class SetupLinkerLinkAllAttribute : BaseMetadataAttribute
+	{
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/DefaultLibraryLinkBehavior.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/DefaultLibraryLinkBehavior.cs
index 93ab6940440ae..1df55a6ca704e 100644
--- a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/DefaultLibraryLinkBehavior.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/DefaultLibraryLinkBehavior.cs
@@ -1,3 +1,6 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
 using Mono.Linker.Tests.Cases.Expectations.Assertions;
 using Mono.Linker.Tests.Cases.Expectations.Metadata;
 
@@ -6,12 +9,12 @@ namespace Mono.Linker.Tests.Cases.Libraries
 	[IgnoreTestCase ("NativeAOT doesn't implement library trimming the same way", IgnoredBy = Tool.NativeAot)]
 	[KeptAttributeAttribute (typeof (IgnoreTestCaseAttribute), By = Tool.Trimmer)]
 	[SetupCompileAsLibrary]
-	[SetupLinkerArgument ("-a", "test.dll")]
+	[SetupLinkerLinkAll]
 	[Kept]
 	[KeptMember (".ctor()")]
 	public class DefaultLibraryLinkBehavior
 	{
-		// Kept because by default libraries their action set to copy
+		// Kept because by default libraries have all members rooted
 		[Kept]
 		public static void Main ()
 		{
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary.cs
new file mode 100644
index 0000000000000..27365bbbfac34
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary.cs
@@ -0,0 +1,56 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+using Mono.Linker.Tests.Cases.Libraries.Dependencies;
+
+#if RootAllLibrary
+[assembly: TypeForwardedTo (typeof (RootAllLibrary_ExportedType))]
+#endif
+
+namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
+{
+	public class RootAllLibrary
+	{
+		public static void Public ()
+		{
+		}
+
+		private static void Private ()
+		{
+		}
+
+		private class NestedType
+		{
+		}
+
+		public static void RemovedBranch ()
+		{
+			if (SubstitutedProperty)
+				RootAllLibrary_OptionalDependency.Use ();
+		}
+
+		// Substituted to false in RootAllLibrary_Substitutions.xml
+		static bool SubstitutedProperty {
+			get {
+				RequiresUnreferencedCode ();
+				return true;
+			}
+		}
+
+		[RequiresUnreferencedCode (nameof (RequiresUnreferencedCode))]
+		static void RequiresUnreferencedCode ()
+		{
+		}
+
+		[RootAllLibrary_RemovedAttribute]
+		class TypeWithRemovedAttribute
+		{
+		}
+	}
+
+	class NonPublicType
+	{
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_ExportedType.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_ExportedType.cs
new file mode 100644
index 0000000000000..222ccf3fef0f2
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_ExportedType.cs
@@ -0,0 +1,9 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
+{
+	public class RootAllLibrary_ExportedType
+	{
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_LinkAttributes.xml b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_LinkAttributes.xml
new file mode 100644
index 0000000000000..5a9d268cc754a
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_LinkAttributes.xml
@@ -0,0 +1,7 @@
+<linker>
+    <assembly fullname="removedattribute">
+        <type fullname="Mono.Linker.Tests.Cases.Libraries.Dependencies.RootAllLibrary_RemovedAttribute">
+            <attribute internal="RemoveAttributeInstances" />
+        </type>
+    </assembly>
+</linker>
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_OptionalDependency.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_OptionalDependency.cs
new file mode 100644
index 0000000000000..53a4e00beea1e
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_OptionalDependency.cs
@@ -0,0 +1,12 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
+{
+	public class RootAllLibrary_OptionalDependency
+	{
+		[RequiresUnreferencedCode (nameof (RootAllLibrary_OptionalDependency))]
+		public static void Use ()
+		{
+		}
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_RemovedAttribute.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_RemovedAttribute.cs
new file mode 100644
index 0000000000000..0f72c2169c16c
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_RemovedAttribute.cs
@@ -0,0 +1,8 @@
+using System;
+
+namespace Mono.Linker.Tests.Cases.Libraries.Dependencies
+{
+	public class RootAllLibrary_RemovedAttribute : Attribute
+	{
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_Substitutions.xml b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_Substitutions.xml
new file mode 100644
index 0000000000000..af4bf89168b0e
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/Dependencies/RootAllLibrary_Substitutions.xml
@@ -0,0 +1,7 @@
+<linker>
+    <assembly fullname="library">
+        <type fullname="Mono.Linker.Tests.Cases.Libraries.Dependencies.RootAllLibrary">
+            <method signature="System.Boolean get_SubstitutedProperty()" body="stub" value="false" />
+        </type>
+    </assembly>
+</linker>
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryBehavior.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryBehavior.cs
new file mode 100644
index 0000000000000..543a088c11448
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryBehavior.cs
@@ -0,0 +1,61 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Metadata;
+using Mono.Linker.Tests.Cases.Libraries.Dependencies;
+
+namespace Mono.Linker.Tests.Cases.Libraries
+{
+	[IgnoreTestCase ("NativeAOT doesn't implement library trimming the same way", IgnoredBy = Tool.NativeAot)]
+	[KeptAttributeAttribute (typeof (IgnoreTestCaseAttribute), By = Tool.Trimmer)]
+	// This validates the trimming behavior of a library when it is trimmed following
+	// the instructions for preparing libraries for trimming:
+	// https://learn.microsoft.comdotnet/core/deploying/trimming/prepare-libraries-for-trimming
+	[SetupCompileBefore ("exportedtype.dll", new[] { typeof (RootAllLibrary_ExportedType) })]
+	[SetupCompileBefore ("optionaldependency.dll", new[] { typeof (RootAllLibrary_OptionalDependency) })]
+	[SetupCompileBefore ("removedattribute.dll", new[] { typeof (RootAllLibrary_RemovedAttribute) },
+		resources: new object[] {
+			new string[] { "Dependencies/RootAllLibrary_LinkAttributes.xml", "ILLink.LinkAttributes.xml" }
+		})]
+	[SetupCompileBefore ("library.dll",
+		new[] { typeof (RootAllLibrary) },
+		references: new[] { "exportedtype.dll", "optionaldependency.dll", "removedattribute.dll" },
+		defines: new[] { "RootAllLibrary" },
+		resources: new object[] {
+			new string[] { "Dependencies/RootAllLibrary_Substitutions.xml", "ILLink.Substitutions.xml" },
+		})]
+
+	[SetupLinkerArgument ("-a", "library.dll")]
+	[IgnoreSubstitutions (false)]
+	[IgnoreLinkAttributes (false)]
+
+	[ExpectedNoWarnings]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "Public()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "Private()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "RemovedBranch()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "get_SubstitutedProperty()")]
+	[KeptTypeInAssembly ("library.dll", "Mono.Linker.Tests.Cases.Libraries.Dependencies.NonPublicType")]
+	[KeptTypeInAssembly ("library.dll", "Mono.Linker.Tests.Cases.Libraries.Dependencies.RootAllLibrary/NestedType")]
+
+	// Type forwarders are kept (but not necessarily the type definition that the forwarder points to)
+	[KeptTypeInAssembly ("library.dll", typeof (RootAllLibrary_ExportedType))]
+	[RemovedAssembly ("exportedtype.dll")]
+
+	// Substitutions and branch removal work. Dependencies reachable only from removed branches are removed.
+	[RemovedAssembly ("optionaldependency.dll")]
+	[LogDoesNotContain ("IL2026:.*SubstitutedProperty.get:.*RequiresUnreferencedCode\\(\\)", regexMatch: true)]
+	[LogDoesNotContain ("IL2026:.*RemovedBranch\\(\\):.*RootAllLibrary_OptionalDependency.Use\\(\\)", regexMatch: true)]
+
+	// Attribute removal works.
+	[RemovedAssembly ("removedattribute.dll")]
+
+	[Kept]
+	public class RootAllLibraryBehavior
+	{
+		[Kept]
+		public static void Main ()
+		{
+		}
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryCopyBehavior.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryCopyBehavior.cs
new file mode 100644
index 0000000000000..9c2b444882223
--- /dev/null
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/Libraries/RootAllLibraryCopyBehavior.cs
@@ -0,0 +1,61 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Metadata;
+using Mono.Linker.Tests.Cases.Libraries.Dependencies;
+
+namespace Mono.Linker.Tests.Cases.Libraries
+{
+	[IgnoreTestCase ("NativeAOT doesn't implement library trimming the same way", IgnoredBy = Tool.NativeAot)]
+	[KeptAttributeAttribute (typeof (IgnoreTestCaseAttribute), By = Tool.Trimmer)]
+	// Keep this testcase setup identical to RootAllLibraryBehavior.cs.
+	// This test is designed to validate the behavior of the 'copy' action,
+	// compared to rooting an assembly via '-a' (tested in RootAllLibraryBehavior.cs).
+	[SetupCompileBefore ("exportedtype.dll", new[] { typeof (RootAllLibrary_ExportedType) })]
+	[SetupCompileBefore ("optionaldependency.dll", new[] { typeof (RootAllLibrary_OptionalDependency) })]
+	[SetupCompileBefore ("removedattribute.dll", new[] { typeof (RootAllLibrary_RemovedAttribute) },
+		resources: new object[] {
+			new string[] { "Dependencies/RootAllLibrary_LinkAttributes.xml", "ILLink.LinkAttributes.xml" }
+		})]
+	[SetupCompileBefore ("library.dll",
+		new[] { typeof (RootAllLibrary) },
+		references: new[] { "exportedtype.dll", "optionaldependency.dll", "removedattribute.dll" },
+		defines: new[] { "RootAllLibrary" },
+		resources: new object[] {
+			new string[] { "Dependencies/RootAllLibrary_Substitutions.xml", "ILLink.Substitutions.xml" },
+		})]
+
+	[SetupLinkerAction ("copy", "library")]
+	[IgnoreSubstitutions (false)]
+	[IgnoreLinkAttributes (false)]
+
+	[ExpectedNoWarnings]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "Public()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "Private()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "RemovedBranch()")]
+	[KeptMemberInAssembly ("library.dll", typeof (RootAllLibrary), "get_SubstitutedProperty()")]
+	[KeptTypeInAssembly ("library.dll", "Mono.Linker.Tests.Cases.Libraries.Dependencies.NonPublicType")]
+	[KeptTypeInAssembly ("library.dll", "Mono.Linker.Tests.Cases.Libraries.Dependencies.RootAllLibrary/NestedType")]
+
+	// Type forwarders are kept (but not necessarily the type definition that the forwarder points to)
+	[KeptTypeInAssembly ("library.dll", typeof (RootAllLibrary_ExportedType))]
+	[RemovedAssembly ("exportedtype.dll")]
+
+	// Substitutions and branch removal don't work in copy assemblies. Dependencies are kept, even if only referenced from reachable branches.
+	[KeptMemberInAssembly ("optionaldependency.dll", typeof (RootAllLibrary_OptionalDependency), "Use()")]
+	[LogContains ("IL2026:.*SubstitutedProperty.get:.*RequiresUnreferencedCode\\(\\)", regexMatch: true)]
+	[LogContains ("IL2026:.*RemovedBranch\\(\\):.*RootAllLibrary_OptionalDependency.Use\\(\\)", regexMatch: true)]
+	
+	// Attributes are kept in copy assemblies, even if the attribute XML has RemoveAttributeInstances.
+	[KeptTypeInAssembly ("removedattribute.dll", typeof (RootAllLibrary_RemovedAttribute))]
+
+	[Kept]
+	public class RootAllLibraryCopyBehavior
+	{
+		[Kept]
+		public static void Main ()
+		{
+		}
+	}
+}
diff --git a/src/tools/illink/test/Mono.Linker.Tests.Cases/TypeForwarding/UnusedForwarderWithAssemblyCopyIsKept.cs b/src/tools/illink/test/Mono.Linker.Tests.Cases/TypeForwarding/UnusedForwarderWithAssemblyCopyIsKept.cs
index 8c3121860df07..4250b07a77c6b 100644
--- a/src/tools/illink/test/Mono.Linker.Tests.Cases/TypeForwarding/UnusedForwarderWithAssemblyCopyIsKept.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests.Cases/TypeForwarding/UnusedForwarderWithAssemblyCopyIsKept.cs
@@ -15,7 +15,7 @@ namespace Mono.Linker.Tests.Cases.TypeForwarding
 
 	[SetupLinkerAction ("copy", "Forwarder")]
 
-	[KeptMemberInAssembly ("Forwarder.dll", typeof (ImplementationLibrary))]
+	[KeptTypeInAssembly ("Forwarder.dll", typeof (ImplementationLibrary))]
 	[RemovedAssembly ("Implementation.dll")]
 
 	public class UnusedForwarderWithAssemblyCopyIsKept
diff --git a/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadataProvider.cs b/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadataProvider.cs
index 4021018445665..b134310fe7970 100644
--- a/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadataProvider.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TestCaseMetadataProvider.cs
@@ -180,5 +180,11 @@ public virtual bool LinkPublicAndFamily ()
 			return _testCaseTypeDefinition.CustomAttributes
 				.FirstOrDefault (attr => attr.AttributeType.Name == nameof (SetupLinkerLinkPublicAndFamilyAttribute)) != null;
 		}
+
+		public virtual bool LinkAll ()
+		{
+			return _testCaseTypeDefinition.CustomAttributes
+				.FirstOrDefault (attr => attr.AttributeType.Name == nameof (SetupLinkerLinkAllAttribute)) != null;
+		}
 	}
 }
\ No newline at end of file
diff --git a/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TrimmingArgumentBuilder.cs b/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TrimmingArgumentBuilder.cs
index dfcc508e08a37..cdb59e6571130 100644
--- a/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TrimmingArgumentBuilder.cs
+++ b/src/tools/illink/test/Mono.Linker.Tests/TestCasesRunner/TrimmingArgumentBuilder.cs
@@ -57,14 +57,14 @@ public virtual void AddDefaultAction (string value)
 			Append (value);
 		}
 
-		public virtual void LinkFromAssembly (string fileName)
+		public virtual void RootAssemblyEntryPoint (string fileName)
 		{
 			Append ("-a");
 			Append (fileName);
 			Append ("entrypoint");
 		}
 
-		public virtual void LinkFromPublicAndFamily (string fileName)
+		public virtual void RootAssemblyVisible (string fileName)
 		{
 #if NETCOREAPP
 			Append ("-a");
@@ -76,6 +76,12 @@ public virtual void LinkFromPublicAndFamily (string fileName)
 #endif
 		}
 
+		public virtual void RootAssembly (string fileName)
+		{
+			Append ("-a");
+			Append (fileName);
+		}
+
 		public virtual void IgnoreDescriptors (bool value)
 		{
 			Append ("--ignore-descriptors");
@@ -179,9 +185,11 @@ public virtual void AddAdditionalArgument (string flag, string[] values)
 		public virtual void ProcessTestInputAssembly (NPath inputAssemblyPath)
 		{
 			if (_metadataProvider.LinkPublicAndFamily ())
-				LinkFromPublicAndFamily (inputAssemblyPath.ToString ());
+				RootAssemblyVisible (inputAssemblyPath.ToString ());
+			else if (_metadataProvider.LinkAll ())
+				RootAssembly (inputAssemblyPath.ToString ());
 			else
-				LinkFromAssembly (inputAssemblyPath.ToString ());
+				RootAssemblyEntryPoint (inputAssemblyPath.ToString ());
 		}
 
 		public virtual void ProcessOptions (TestCaseLinkerOptions options)