diff --git a/cli/src/main/java/net/neoforged/jst/cli/intellij/IntelliJEnvironmentImpl.java b/cli/src/main/java/net/neoforged/jst/cli/intellij/IntelliJEnvironmentImpl.java
index 07742fb..fc218dc 100644
--- a/cli/src/main/java/net/neoforged/jst/cli/intellij/IntelliJEnvironmentImpl.java
+++ b/cli/src/main/java/net/neoforged/jst/cli/intellij/IntelliJEnvironmentImpl.java
@@ -1,5 +1,6 @@
 package net.neoforged.jst.cli.intellij;
 
+import com.intellij.codeInsight.ExternalAnnotationsManager;
 import com.intellij.core.CoreApplicationEnvironment;
 import com.intellij.core.JavaCoreApplicationEnvironment;
 import com.intellij.core.JavaCoreProjectEnvironment;
@@ -22,11 +23,16 @@
 import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.JavaModuleSystem;
 import com.intellij.psi.JavaPsiFacade;
+import com.intellij.psi.PsiAnnotation;
+import com.intellij.psi.PsiClass;
+import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiElementFinder;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.PsiFileFactory;
 import com.intellij.psi.PsiManager;
+import com.intellij.psi.PsiModifierListOwner;
 import com.intellij.psi.PsiNameHelper;
+import com.intellij.psi.PsiNameValuePair;
 import com.intellij.psi.augment.PsiAugmentProvider;
 import com.intellij.psi.impl.JavaClassSupersImpl;
 import com.intellij.psi.impl.PsiElementFinderImpl;
@@ -37,12 +43,15 @@
 import com.intellij.psi.util.JavaClassSupers;
 import net.neoforged.jst.api.IntelliJEnvironment;
 import net.neoforged.jst.api.Logger;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.VisibleForTesting;
 
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.List;
 import java.util.Objects;
 
 public class IntelliJEnvironmentImpl implements IntelliJEnvironment, AutoCloseable {
@@ -153,6 +162,7 @@ public PsiFile parseFileFromMemory(String filename, String fileContent) {
      */
     private void initProjectExtensionsAndServices(MockProject project) {
         project.registerService(PsiNameHelper.class, PsiNameHelperImpl.class);
+        project.registerService(ExternalAnnotationsManager.class, new MockExternalAnnotationsManager());
 
         var projectExtensions = project.getExtensionArea();
         CoreApplicationEnvironment.registerExtensionPoint(projectExtensions, PsiTreeChangePreprocessor.EP.getName(), PsiTreeChangePreprocessor.class);
diff --git a/cli/src/main/java/net/neoforged/jst/cli/intellij/MockExternalAnnotationsManager.java b/cli/src/main/java/net/neoforged/jst/cli/intellij/MockExternalAnnotationsManager.java
new file mode 100644
index 0000000..f3a4565
--- /dev/null
+++ b/cli/src/main/java/net/neoforged/jst/cli/intellij/MockExternalAnnotationsManager.java
@@ -0,0 +1,91 @@
+package net.neoforged.jst.cli.intellij;
+
+import com.intellij.codeInsight.ExternalAnnotationsManager;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.PsiAnnotation;
+import com.intellij.psi.PsiClass;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
+import com.intellij.psi.PsiModifierListOwner;
+import com.intellij.psi.PsiNameValuePair;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+
+public class MockExternalAnnotationsManager extends ExternalAnnotationsManager {
+    @Override
+    public boolean hasAnnotationRootsForFile(@NotNull VirtualFile file) {
+        return false;
+    }
+
+    @Override
+    public boolean isExternalAnnotation(@NotNull PsiAnnotation annotation) {
+        return false;
+    }
+
+    @Override
+    public @Nullable PsiAnnotation findExternalAnnotation(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQN) {
+        return null;
+    }
+
+    @Override
+    public @NotNull List<PsiAnnotation> findExternalAnnotations(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQN) {
+        return List.of();
+    }
+
+    @Override
+    public boolean isExternalAnnotationWritable(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQN) {
+        return false;
+    }
+
+    @Override
+    public @NotNull PsiAnnotation @NotNull [] findExternalAnnotations(@NotNull PsiModifierListOwner listOwner) {
+        return new PsiAnnotation[0];
+    }
+
+    @Override
+    public @Nullable List<PsiAnnotation> findDefaultConstructorExternalAnnotations(@NotNull PsiClass aClass) {
+        return List.of();
+    }
+
+    @Override
+    public @Nullable List<PsiAnnotation> findDefaultConstructorExternalAnnotations(@NotNull PsiClass aClass, @NotNull String annotationFQN) {
+        return List.of();
+    }
+
+    @Override
+    public void annotateExternally(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQName, @NotNull PsiFile fromFile, PsiNameValuePair @Nullable [] value) throws CanceledConfigurationException {
+
+    }
+
+    @Override
+    public boolean deannotate(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQN) {
+        return false;
+    }
+
+    @Override
+    public boolean editExternalAnnotation(@NotNull PsiModifierListOwner listOwner, @NotNull String annotationFQN, PsiNameValuePair @Nullable [] value) {
+        return false;
+    }
+
+    @Override
+    public @NotNull AnnotationPlace chooseAnnotationsPlaceNoUi(@NotNull PsiElement element) {
+        return AnnotationPlace.NOWHERE;
+    }
+
+    @Override
+    public @NotNull AnnotationPlace chooseAnnotationsPlace(@NotNull PsiElement element) {
+        return AnnotationPlace.NOWHERE;
+    }
+
+    @Override
+    public @Nullable List<PsiFile> findExternalAnnotationsFiles(@NotNull PsiModifierListOwner listOwner) {
+        return List.of();
+    }
+
+    @Override
+    public boolean hasConfiguredAnnotationRoot(@NotNull PsiModifierListOwner owner) {
+        return false;
+    }
+}
diff --git a/settings.gradle b/settings.gradle
index 8c5fa61..a773252 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -42,3 +42,4 @@ include 'tests'
 include 'accesstransformers'
 include 'interfaceinjection'
 include 'unpick'
+include 'sourcetest'
\ No newline at end of file
diff --git a/sourcetest/build.gradle b/sourcetest/build.gradle
new file mode 100644
index 0000000..5456ed1
--- /dev/null
+++ b/sourcetest/build.gradle
@@ -0,0 +1,11 @@
+/**
+ * This project only serves to run the application with all plugins from IntelliJ
+ * while being able to step into original sources.
+ */
+dependencies {
+    implementation(project(':cli'))
+    implementation(project(':accesstransformers'))
+    implementation(project(':interfaceinjection'))
+    implementation(project(':parchment'))
+    implementation(project(':unpick'))
+}