diff --git a/pom.xml b/pom.xml
index 6b7fe3e..e5fb8c5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -173,6 +173,9 @@
           <argLine>${argLine.common} ${argLine.printGC} --add-modules jdk.incubator.foreign</argLine>
           <!-- Ensure the whole stacktrace is preserved when an exception is thrown. See https://issues.apache.org/jira/browse/SUREFIRE-1457 -->
           <trimStackTrace>false</trimStackTrace>
+          <systemProperties>
+            <sample>nosample</sample>
+          </systemProperties>
         </configuration>
         <dependencies>
           <!-- Declare the surefire dynamic dependencies explicitly, to speed up the docker build. -->
diff --git a/src/main/java/io/netty/buffer/api/memseg/MemSegBuffer.java b/src/main/java/io/netty/buffer/api/memseg/MemSegBuffer.java
index b99b81c..842e48a 100644
--- a/src/main/java/io/netty/buffer/api/memseg/MemSegBuffer.java
+++ b/src/main/java/io/netty/buffer/api/memseg/MemSegBuffer.java
@@ -60,12 +60,19 @@ class MemSegBuffer extends RcSupport<Buffer, MemSegBuffer> implements Buffer, Re
 
     static {
         try (ResourceScope scope = ResourceScope.newSharedScope()) {
-            CLOSED_SEGMENT = MemorySegment.allocateNative(1, scope);
+            // We are not allowed to allocate a zero-sized native buffer, but we *can* take a zero-sized slice from it.
+            // We need the CLOSED_SEGMENT to have a size of zero, because we'll use its size for bounds checks after
+            // the buffer is closed.
+            MemorySegment segment = MemorySegment.allocateNative(1, scope);
+            CLOSED_SEGMENT = segment.asSlice(0, 0);
         }
         SEGMENT_CLOSE = new Drop<MemSegBuffer>() {
             @Override
             public void drop(MemSegBuffer buf) {
-                buf.base.scope().close();
+                ResourceScope scope = buf.base.scope();
+                if (!scope.isImplicit()) {
+                    scope.close();
+                }
             }
 
             @Override
diff --git a/src/main/java/io/netty/buffer/api/memseg/NativeMemorySegmentManager.java b/src/main/java/io/netty/buffer/api/memseg/NativeMemorySegmentManager.java
index b49395e..98fe021 100644
--- a/src/main/java/io/netty/buffer/api/memseg/NativeMemorySegmentManager.java
+++ b/src/main/java/io/netty/buffer/api/memseg/NativeMemorySegmentManager.java
@@ -22,6 +22,8 @@ import java.lang.ref.Cleaner;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.LongAdder;
 
+import static jdk.incubator.foreign.ResourceScope.newSharedScope;
+
 public class NativeMemorySegmentManager extends AbstractMemorySegmentManager {
     public static final LongAdder MEM_USAGE_NATIVE = new LongAdder();
     private static final ConcurrentHashMap<Long, Runnable> CLEANUP_ACTIONS = new ConcurrentHashMap<>();
@@ -37,7 +39,7 @@ public class NativeMemorySegmentManager extends AbstractMemorySegmentManager {
 
     @Override
     protected MemorySegment createSegment(long size, Cleaner cleaner) {
-        final ResourceScope scope = ResourceScope.newSharedScope(cleaner);
+        final ResourceScope scope = cleaner == null ? newSharedScope() : newSharedScope(cleaner);
         scope.addOnClose(getCleanupAction(size));
         var segment = MemorySegment.allocateNative(size, scope);
         MEM_USAGE_NATIVE.add(size);
diff --git a/src/test/java/io/netty/buffer/api/BufferTest.java b/src/test/java/io/netty/buffer/api/BufferTest.java
index f2a9c43..e3ccdbf 100644
--- a/src/test/java/io/netty/buffer/api/BufferTest.java
+++ b/src/test/java/io/netty/buffer/api/BufferTest.java
@@ -31,10 +31,14 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.ReadOnlyBufferException;
 import java.text.ParseException;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.time.temporal.TemporalUnit;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.SplittableRandom;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -43,6 +47,7 @@ import java.util.concurrent.SynchronousQueue;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Function;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 import java.util.stream.Stream.Builder;
 
@@ -64,7 +69,7 @@ public class BufferTest {
     private static ExecutorService executor;
 
     private static final Memoize<Fixture[]> ALL_COMBINATIONS = new Memoize<>(
-            () -> fixtureCombinations().toArray(Fixture[]::new));
+            () -> fixtureCombinations().filter(sample()).toArray(Fixture[]::new));
     private static final Memoize<Fixture[]> NON_COMPOSITE = new Memoize<>(
             () -> Arrays.stream(ALL_COMBINATIONS.get()).filter(f -> !f.isComposite()).toArray(Fixture[]::new));
     private static final Memoize<Fixture[]> HEAP_ALLOCS = new Memoize<>(
@@ -73,6 +78,19 @@ public class BufferTest {
             () -> Arrays.stream(ALL_COMBINATIONS.get()).filter(f -> f.isDirect()).toArray(Fixture[]::new));
     private static final Memoize<Fixture[]> POOLED_ALLOCS = new Memoize<>(
             () -> Arrays.stream(ALL_COMBINATIONS.get()).filter(f -> f.isPooled()).toArray(Fixture[]::new));
+    private static final Memoize<Fixture[]> POOLED_DIRECT_ALLOCS = new Memoize<>(
+            () -> Arrays.stream(ALL_COMBINATIONS.get()).filter(
+                    f -> f.isPooled() && f.isDirect()).toArray(Fixture[]::new));
+
+    private static Predicate<Fixture> sample() {
+        String sampleSetting = System.getProperty("sample");
+        if ("nosample".equalsIgnoreCase(sampleSetting)) {
+            return fixture -> true;
+        }
+        Instant today = Instant.now().truncatedTo(ChronoUnit.DAYS);
+        SplittableRandom rng = new SplittableRandom(today.hashCode());
+        return fixture -> rng.nextInt(0, 100) <= 2; // Filter out 97% of tests.
+    }
 
     static Fixture[] allocators() {
         return ALL_COMBINATIONS.get();
@@ -94,6 +112,10 @@ public class BufferTest {
         return POOLED_ALLOCS.get();
     }
 
+    static Fixture[] pooledDirectAllocators() {
+        return POOLED_DIRECT_ALLOCS.get();
+    }
+
     static List<Fixture> initialAllocators() {
         return List.of(
                 new Fixture("heap", BufferAllocator::heap, HEAP),
@@ -962,7 +984,7 @@ public class BufferTest {
         }
     }
 
-    @Disabled
+    @Disabled // TODO
     @ParameterizedTest
     @MethodSource("allocators")
     public void sliceMustBecomeOwnedOnSourceBufferClose(Fixture fixture) {
@@ -1650,42 +1672,42 @@ public class BufferTest {
     @Nested
     @Isolated
     class CleanerTests {
-        @Disabled("Precise native memory accounting does not work since recent panama-foreign changes.")
         @ParameterizedTest
-        @MethodSource("io.netty.buffer.api.BufTest#directAllocators")
+        @MethodSource("io.netty.buffer.api.BufferTest#directAllocators")
         public void bufferMustBeClosedByCleaner(Fixture fixture) throws InterruptedException {
+            var initial = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum();
             var allocator = fixture.createAllocator();
             allocator.close();
-            int iterations = 100;
+            int iterations = 50;
             int allocationSize = 1024;
             for (int i = 0; i < iterations; i++) {
                 allocateAndForget(allocator, allocationSize);
                 System.gc();
                 System.runFinalization();
             }
-            var sum = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum();
+            var sum = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum() - initial;
             var totalAllocated = (long) allocationSize * iterations;
             assertThat(sum).isLessThan(totalAllocated);
         }
 
-        private void allocateAndForget(BufferAllocator allocator, int size) {
+        private static void allocateAndForget(BufferAllocator allocator, int size) {
             allocator.allocate(size);
         }
 
-        @Disabled("Precise native memory accounting does not work since recent panama-foreign changes.")
         @ParameterizedTest
-        @MethodSource("io.netty.buffer.api.BufTest#directPooledAllocators")
+        @MethodSource("io.netty.buffer.api.BufferTest#pooledDirectAllocators")
         public void buffersMustBeReusedByPoolingAllocatorEvenWhenDroppedByCleanerInsteadOfExplicitly(Fixture fixture)
                 throws InterruptedException {
+            var initial = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum();
             try (var allocator = fixture.createAllocator()) {
-                int iterations = 100;
+                int iterations = 50;
                 int allocationSize = 1024;
                 for (int i = 0; i < iterations; i++) {
                     allocateAndForget(allocator, allocationSize);
                     System.gc();
                     System.runFinalization();
                 }
-                var sum = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum();
+                var sum = NativeMemorySegmentManager.MEM_USAGE_NATIVE.sum() - initial;
                 var totalAllocated = (long) allocationSize * iterations;
                 assertThat(sum).isLessThan(totalAllocated);
             }