diff --git a/internal-api/internal-api-9/build.gradle.kts b/internal-api/internal-api-9/build.gradle.kts
index 47ede220d8b..bd9e9fbf3d1 100644
--- a/internal-api/internal-api-9/build.gradle.kts
+++ b/internal-api/internal-api-9/build.gradle.kts
@@ -34,6 +34,13 @@ listOf(JavaCompile::class.java, GroovyCompile::class.java).forEach { compileTask
 
 extra["minimumBranchCoverage"] = 0.8
 extra["minimumInstructionCoverage"] = 0.8
+// Remaining uncovered code is JVM-specific fallbacks (ProcessHandle failures, IBM J9 frame mapping)
+// that cannot be reached on the test JVMs.
+extra["excludedClassesCoverage"] = listOf(
+  "datadog.trace.util.JDK9ExecutableSupplier",
+  "datadog.trace.util.JDK9PidSupplier",
+  "datadog.trace.util.stacktrace.JDK9StackWalker",
+)
 
 dependencies {
   api(project(":internal-api"))
diff --git a/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ExecutableSupplierTest.java b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ExecutableSupplierTest.java
new file mode 100644
index 00000000000..888f5c9227c
--- /dev/null
+++ b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ExecutableSupplierTest.java
@@ -0,0 +1,15 @@
+package datadog.trace.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class JDK9ExecutableSupplierTest {
+
+  @Test
+  void returnsCurrentProcessExecutable() {
+    String expected = ProcessHandle.current().info().command().orElse(null);
+
+    assertEquals(expected, new JDK9ExecutableSupplier().get());
+  }
+}
diff --git a/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ModuleAccessTest.java b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ModuleAccessTest.java
new file mode 100644
index 00000000000..acdcce55436
--- /dev/null
+++ b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9ModuleAccessTest.java
@@ -0,0 +1,80 @@
+package datadog.trace.util;
+
+import static datadog.trace.util.JDK9ModuleAccess.addModuleReads;
+import static datadog.trace.util.JDK9ModuleAccess.canRead;
+import static datadog.trace.util.JDK9ModuleAccess.exportModuleToUnnamedModule;
+import static datadog.trace.util.JDK9ModuleAccess.getUnnamedModule;
+import static java.util.Collections.singleton;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.lang.instrument.Instrumentation;
+import java.net.URL;
+import java.net.URLClassLoader;
+import net.bytebuddy.agent.ByteBuddyAgent;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+class JDK9ModuleAccessTest {
+
+  private static Instrumentation inst;
+
+  @BeforeAll
+  static void installAgent() {
+    inst = ByteBuddyAgent.install();
+  }
+
+  @Test
+  void getUnnamedModuleReturnsClassLoaderUnnamedModule() {
+    ClassLoader cl = newClassLoader();
+
+    assertSame(cl.getUnnamedModule(), getUnnamedModule(cl));
+  }
+
+  @Test
+  void canReadReflectsModuleReadability() {
+    Module unnamed = newClassLoader().getUnnamedModule();
+    Module javaBase = Object.class.getModule();
+
+    // unnamed modules read every module, java.base reads no unnamed module
+    assertTrue(canRead(unnamed, javaBase));
+    assertFalse(canRead(javaBase, unnamed));
+  }
+
+  @Test
+  void addModuleReadsMakesModuleReadable() {
+    Module javaSql = java.sql.Driver.class.getModule();
+    Module unnamed = newClassLoader().getUnnamedModule();
+    assertFalse(javaSql.canRead(unnamed));
+
+    addModuleReads(inst, javaSql, singleton(unnamed));
+
+    assertTrue(javaSql.canRead(unnamed));
+  }
+
+  @Test
+  void exportModuleToUnnamedModuleExportsPackages() {
+    ClassLoader cl = newClassLoader();
+    Module javaBase = Object.class.getModule();
+    assertFalse(javaBase.isExported("jdk.internal.misc", cl.getUnnamedModule()));
+
+    exportModuleToUnnamedModule(inst, "java.base", new String[] {"jdk.internal.misc"}, cl);
+
+    assertTrue(javaBase.isExported("jdk.internal.misc", cl.getUnnamedModule()));
+  }
+
+  @Test
+  void exportModuleToUnnamedModuleIgnoresUnknownModule() {
+    ClassLoader cl = newClassLoader();
+
+    assertDoesNotThrow(
+        () -> exportModuleToUnnamedModule(inst, "does.not.exist", new String[] {"some.pkg"}, cl));
+  }
+
+  /** A fresh class loader, so module changes don't leak to other tests. */
+  private static ClassLoader newClassLoader() {
+    return new URLClassLoader(new URL[0], null);
+  }
+}
diff --git a/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9PidSupplierTest.java b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9PidSupplierTest.java
new file mode 100644
index 00000000000..a56b52e7eed
--- /dev/null
+++ b/internal-api/internal-api-9/src/test/java/datadog/trace/util/JDK9PidSupplierTest.java
@@ -0,0 +1,13 @@
+package datadog.trace.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class JDK9PidSupplierTest {
+
+  @Test
+  void returnsCurrentProcessPid() {
+    assertEquals(Long.toString(ProcessHandle.current().pid()), new JDK9PidSupplier().get());
+  }
+}