diff --git a/src/embed_tests/Codecs.cs b/src/embed_tests/Codecs.cs
index 1beddbec9..157e60803 100644
--- a/src/embed_tests/Codecs.cs
+++ b/src/embed_tests/Codecs.cs
@@ -421,13 +421,18 @@ public PyObject TryEncode(object value)
             }
         }
 
-        class InstancelessExceptionDecoder : IPyObjectDecoder
+        class InstancelessExceptionDecoder : IPyObjectDecoder, IDisposable
         {
             readonly PyObject PyErr = Py.Import("clr.interop").GetAttr("PyErr");
 
             public bool CanDecode(PyType objectType, Type targetType)
                 => PythonReferenceComparer.Instance.Equals(PyErr, objectType);
 
+            public void Dispose()
+            {
+                PyErr.Dispose();
+            }
+
             public bool TryDecode<T>(PyObject pyObj, out T value)
             {
                 if (pyObj.HasAttr("value"))
diff --git a/src/embed_tests/GlobalTestsSetup.cs b/src/embed_tests/GlobalTestsSetup.cs
index 9a832cb0c..dff58b978 100644
--- a/src/embed_tests/GlobalTestsSetup.cs
+++ b/src/embed_tests/GlobalTestsSetup.cs
@@ -9,6 +9,22 @@ namespace Python.EmbeddingTest
     [SetUpFixture]
     public partial class GlobalTestsSetup
     {
+        [OneTimeSetUp]
+        public void GlobalSetup()
+        {
+            Finalizer.Instance.ErrorHandler += FinalizerErrorHandler;
+        }
+
+        private void FinalizerErrorHandler(object sender, Finalizer.ErrorArgs e)
+        {
+            if (e.Error is RuntimeShutdownException)
+            {
+                // allow objects to leak after the python runtime run
+                // they were created in is gone
+                e.Handled = true;
+            }
+        }
+
         [OneTimeTearDown]
         public void FinalCleanup()
         {
diff --git a/src/embed_tests/Inheritance.cs b/src/embed_tests/Inheritance.cs
index 58d66ed96..7de5277a1 100644
--- a/src/embed_tests/Inheritance.cs
+++ b/src/embed_tests/Inheritance.cs
@@ -24,6 +24,7 @@ public void SetUp()
         [OneTimeTearDown]
         public void Dispose()
         {
+            ExtraBaseTypeProvider.ExtraBase.Dispose();
             PythonEngine.Shutdown();
         }
 
diff --git a/src/embed_tests/TestDomainReload.cs b/src/embed_tests/TestDomainReload.cs
index e4479da18..e7b330d12 100644
--- a/src/embed_tests/TestDomainReload.cs
+++ b/src/embed_tests/TestDomainReload.cs
@@ -179,116 +179,6 @@ public static void CrossDomainObject()
 
         #endregion
 
-        #region Tempary tests
-
-        // https://github.com/pythonnet/pythonnet/pull/1074#issuecomment-596139665
-        [Test]
-        public void CrossReleaseBuiltinType()
-        {
-            void ExecTest()
-            {
-                try
-                {
-                    PythonEngine.Initialize();
-                    var numRef = CreateNumReference();
-                    Assert.True(numRef.IsAlive);
-                    PythonEngine.Shutdown(); // <- "run" 1 ends
-                    PythonEngine.Initialize(); // <- "run" 2 starts
-
-                    GC.Collect();
-                    GC.WaitForPendingFinalizers(); // <- this will put former `num` into Finalizer queue
-                    Finalizer.Instance.Collect();
-                    // ^- this will call PyObject.Dispose, which will call XDecref on `num.Handle`,
-                    // but Python interpreter from "run" 1 is long gone, so it will corrupt memory instead.
-                    Assert.False(numRef.IsAlive);
-                }
-                finally
-                {
-                    PythonEngine.Shutdown();
-                }
-            }
-
-            var errorArgs = new List<Finalizer.ErrorArgs>();
-            void ErrorHandler(object sender, Finalizer.ErrorArgs e)
-            {
-                errorArgs.Add(e);
-            }
-            Finalizer.Instance.ErrorHandler += ErrorHandler;
-            try
-            {
-                for (int i = 0; i < 10; i++)
-                {
-                    ExecTest();
-                }
-            }
-            finally
-            {
-                Finalizer.Instance.ErrorHandler -= ErrorHandler;
-            }
-            Assert.AreEqual(errorArgs.Count, 0);
-        }
-
-        [Test]
-        public void CrossReleaseCustomType()
-        {
-            void ExecTest()
-            {
-                try
-                {
-                    PythonEngine.Initialize();
-                    var objRef = CreateConcreateObject();
-                    Assert.True(objRef.IsAlive);
-                    PythonEngine.Shutdown(); // <- "run" 1 ends
-                    PythonEngine.Initialize(); // <- "run" 2 starts
-                    GC.Collect();
-                    GC.WaitForPendingFinalizers();
-                    Finalizer.Instance.Collect();
-                    Assert.False(objRef.IsAlive);
-                }
-                finally
-                {
-                    PythonEngine.Shutdown();
-                }
-            }
-
-            var errorArgs = new List<Finalizer.ErrorArgs>();
-            void ErrorHandler(object sender, Finalizer.ErrorArgs e)
-            {
-                errorArgs.Add(e);
-            }
-            Finalizer.Instance.ErrorHandler += ErrorHandler;
-            try
-            {
-                for (int i = 0; i < 10; i++)
-                {
-                    ExecTest();
-                }
-            }
-            finally
-            {
-                Finalizer.Instance.ErrorHandler -= ErrorHandler;
-            }
-            Assert.AreEqual(errorArgs.Count, 0);
-        }
-
-        private static WeakReference CreateNumReference()
-        {
-            var num = 3216757418.ToPython();
-            Assert.AreEqual(num.Refcount, 1);
-            WeakReference numRef = new WeakReference(num, false);
-            return numRef;
-        }
-
-        private static WeakReference CreateConcreateObject()
-        {
-            var obj = new Domain.MyClass().ToPython();
-            Assert.AreEqual(obj.Refcount, 1);
-            WeakReference numRef = new WeakReference(obj, false);
-            return numRef;
-        }
-
-        #endregion Tempary tests
-
         /// <summary>
         /// This is a magic incantation required to run code in an application
         /// domain other than the current one.
diff --git a/src/embed_tests/pyinitialize.cs b/src/embed_tests/pyinitialize.cs
index a15aff585..61ed9c6fb 100644
--- a/src/embed_tests/pyinitialize.cs
+++ b/src/embed_tests/pyinitialize.cs
@@ -40,8 +40,10 @@ public static void LoadSpecificArgs()
             {
                 using (var argv = new PyList(Runtime.Runtime.PySys_GetObject("argv")))
                 {
-                    Assert.AreEqual(args[0], argv[0].ToString());
-                    Assert.AreEqual(args[1], argv[1].ToString());
+                    using var v0 = argv[0];
+                    using var v1 = argv[1];
+                    Assert.AreEqual(args[0], v0.ToString());
+                    Assert.AreEqual(args[1], v1.ToString());
                 }
             }
         }
@@ -54,12 +56,16 @@ public void ImportClassShutdownRefcount()
 
             PyObject ns = Py.Import(typeof(ImportClassShutdownRefcountClass).Namespace);
             PyObject cls = ns.GetAttr(nameof(ImportClassShutdownRefcountClass));
+            BorrowedReference clsRef = cls.Reference;
+#pragma warning disable CS0618 // Type or member is obsolete
+            cls.Leak();
+#pragma warning restore CS0618 // Type or member is obsolete
             ns.Dispose();
 
-            Assert.Less(cls.Refcount, 256);
+            Assert.Less(Runtime.Runtime.Refcount(clsRef), 256);
 
             PythonEngine.Shutdown();
-            Assert.Greater(cls.Refcount, 0);
+            Assert.Greater(Runtime.Runtime.Refcount(clsRef), 0);
         }
 
         /// <summary>
@@ -176,6 +182,7 @@ public static void TestRunExitFuncs()
                 {
                     Assert.Fail(msg);
                 }
+                PythonEngine.InteropConfiguration = InteropConfiguration.MakeDefault();
                 return;
             }
             bool called = false;
@@ -187,6 +194,7 @@ public static void TestRunExitFuncs()
             atexit.Dispose();
             Runtime.Runtime.Shutdown();
             Assert.True(called);
+            PythonEngine.InteropConfiguration = InteropConfiguration.MakeDefault();
         }
     }
 
diff --git a/src/runtime/Codecs/DecoderGroup.cs b/src/runtime/Codecs/DecoderGroup.cs
index b72cd796c..cf0ee33e9 100644
--- a/src/runtime/Codecs/DecoderGroup.cs
+++ b/src/runtime/Codecs/DecoderGroup.cs
@@ -8,7 +8,7 @@ namespace Python.Runtime.Codecs
     /// <summary>
     /// Represents a group of <see cref="IPyObjectDecoder"/>s. Useful to group them by priority.
     /// </summary>
-    public sealed class DecoderGroup: IPyObjectDecoder, IEnumerable<IPyObjectDecoder>
+    public sealed class DecoderGroup: IPyObjectDecoder, IEnumerable<IPyObjectDecoder>, IDisposable
     {
         readonly List<IPyObjectDecoder> decoders = new List<IPyObjectDecoder>();
 
@@ -46,6 +46,15 @@ public bool TryDecode<T>(PyObject pyObj, out T value)
         /// <inheritdoc />
         public IEnumerator<IPyObjectDecoder> GetEnumerator() => this.decoders.GetEnumerator();
         IEnumerator IEnumerable.GetEnumerator() => this.decoders.GetEnumerator();
+
+        public void Dispose()
+        {
+            foreach (var decoder in this.decoders.OfType<IDisposable>())
+            {
+                decoder.Dispose();
+            }
+            this.decoders.Clear();
+        }
     }
 
     public static class DecoderGroupExtensions
diff --git a/src/runtime/Codecs/EncoderGroup.cs b/src/runtime/Codecs/EncoderGroup.cs
index 4f776a669..6c40623ca 100644
--- a/src/runtime/Codecs/EncoderGroup.cs
+++ b/src/runtime/Codecs/EncoderGroup.cs
@@ -8,7 +8,7 @@ namespace Python.Runtime.Codecs
     /// <summary>
     /// Represents a group of <see cref="IPyObjectDecoder"/>s. Useful to group them by priority.
     /// </summary>
-    public sealed class EncoderGroup: IPyObjectEncoder, IEnumerable<IPyObjectEncoder>
+    public sealed class EncoderGroup: IPyObjectEncoder, IEnumerable<IPyObjectEncoder>, IDisposable
     {
         readonly List<IPyObjectEncoder> encoders = new List<IPyObjectEncoder>();
 
@@ -47,6 +47,15 @@ public PyObject TryEncode(object value)
         /// <inheritdoc />
         public IEnumerator<IPyObjectEncoder> GetEnumerator() => this.encoders.GetEnumerator();
         IEnumerator IEnumerable.GetEnumerator() => this.encoders.GetEnumerator();
+
+        public void Dispose()
+        {
+            foreach (var encoder in this.encoders.OfType<IDisposable>())
+            {
+                encoder.Dispose();
+            }
+            this.encoders.Clear();
+        }
     }
 
     public static class EncoderGroupExtensions
diff --git a/src/runtime/InteropConfiguration.cs b/src/runtime/InteropConfiguration.cs
index 78af5037a..30c9a1c2c 100644
--- a/src/runtime/InteropConfiguration.cs
+++ b/src/runtime/InteropConfiguration.cs
@@ -2,10 +2,11 @@ namespace Python.Runtime
 {
     using System;
     using System.Collections.Generic;
+    using System.Linq;
 
     using Python.Runtime.Mixins;
 
-    public sealed class InteropConfiguration
+    public sealed class InteropConfiguration: IDisposable
     {
         internal readonly PythonBaseTypeProviderGroup pythonBaseTypeProviders
             = new PythonBaseTypeProviderGroup();
@@ -24,5 +25,14 @@ public static InteropConfiguration MakeDefault()
                 },
             };
         }
+
+        public void Dispose()
+        {
+            foreach (var provider in PythonBaseTypeProviders.OfType<IDisposable>())
+            {
+                provider.Dispose();
+            }
+            PythonBaseTypeProviders.Clear();
+        }
     }
 }
diff --git a/src/runtime/Mixins/CollectionMixinsProvider.cs b/src/runtime/Mixins/CollectionMixinsProvider.cs
index 48ea35f1c..e01a6be0d 100644
--- a/src/runtime/Mixins/CollectionMixinsProvider.cs
+++ b/src/runtime/Mixins/CollectionMixinsProvider.cs
@@ -4,7 +4,7 @@
 
 namespace Python.Runtime.Mixins
 {
-    class CollectionMixinsProvider : IPythonBaseTypeProvider
+    class CollectionMixinsProvider : IPythonBaseTypeProvider, IDisposable
     {
         readonly Lazy<PyObject> mixinsModule;
         public CollectionMixinsProvider(Lazy<PyObject> mixinsModule)
@@ -86,5 +86,13 @@ static Type[] NewInterfaces(Type type)
 
         static Type GetDefinition(Type type)
             => type.IsGenericType ? type.GetGenericTypeDefinition() : type;
+
+        public void Dispose()
+        {
+            if (this.mixinsModule.IsValueCreated)
+            {
+                this.mixinsModule.Value.Dispose();
+            }
+        }
     }
 }
diff --git a/src/runtime/converterextensions.cs b/src/runtime/converterextensions.cs
index 2396fb0bd..dfc2ecc21 100644
--- a/src/runtime/converterextensions.cs
+++ b/src/runtime/converterextensions.cs
@@ -166,8 +166,8 @@ internal static void Reset()
                 {
                     clrToPython.Clear();
                     pythonToClr.Clear();
-                    encoders.Clear();
-                    decoders.Clear();
+                    encoders.Dispose();
+                    decoders.Dispose();
                 }
         }
 
diff --git a/src/runtime/finalizer.cs b/src/runtime/finalizer.cs
index 5153c13ad..0acf5254d 100644
--- a/src/runtime/finalizer.cs
+++ b/src/runtime/finalizer.cs
@@ -2,6 +2,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -30,10 +31,12 @@ public class ErrorArgs : EventArgs
         [DefaultValue(DefaultThreshold)]
         public int Threshold { get; set; } = DefaultThreshold;
 
+        bool started;
+
         [DefaultValue(true)]
         public bool Enable { get; set; } = true;
 
-        private ConcurrentQueue<IntPtr> _objQueue = new ConcurrentQueue<IntPtr>();
+        private ConcurrentQueue<PendingFinalization> _objQueue = new ();
         private int _throttled;
 
         #region FINALIZER_CHECK
@@ -79,6 +82,8 @@ internal IncorrectRefCountException(IntPtr ptr)
 
         internal void ThrottledCollect()
         {
+            if (!started) throw new InvalidOperationException($"{nameof(PythonEngine)} is not initialized");
+
             _throttled = unchecked(this._throttled + 1);
             if (!Enable || _throttled < Threshold) return;
             _throttled = 0;
@@ -87,12 +92,13 @@ internal void ThrottledCollect()
 
         internal List<IntPtr> GetCollectedObjects()
         {
-            return _objQueue.ToList();
+            return _objQueue.Select(o => o.PyObj).ToList();
         }
 
-        internal void AddFinalizedObject(ref IntPtr obj)
+        internal void AddFinalizedObject(ref IntPtr obj, int run)
         {
-            if (!Enable || obj == IntPtr.Zero)
+            Debug.Assert(obj != IntPtr.Zero);
+            if (!Enable)
             {
                 return;
             }
@@ -101,14 +107,20 @@ internal void AddFinalizedObject(ref IntPtr obj)
             lock (_queueLock)
 #endif
             {
-                this._objQueue.Enqueue(obj);
+                this._objQueue.Enqueue(new PendingFinalization { PyObj = obj, RuntimeRun = run });
             }
             obj = IntPtr.Zero;
         }
 
+        internal static void Initialize()
+        {
+            Instance.started = true;
+        }
+
         internal static void Shutdown()
         {
             Instance.DisposeAll();
+            Instance.started = false;
         }
 
         private void DisposeAll()
@@ -124,36 +136,31 @@ private void DisposeAll()
 #if FINALIZER_CHECK
                 ValidateRefCount();
 #endif
-                IntPtr obj;
                 Runtime.PyErr_Fetch(out var errType, out var errVal, out var traceback);
 
+                int run = Runtime.GetRun();
+
                 try
                 {
                     while (!_objQueue.IsEmpty)
                     {
-                        if (!_objQueue.TryDequeue(out obj))
+                        if (!_objQueue.TryDequeue(out var obj))
+                            continue;
+
+                        if (obj.RuntimeRun != run)
+                        {
+                            HandleFinalizationException(obj.PyObj, new RuntimeShutdownException(obj.PyObj));
                             continue;
+                        }
 
-                        Runtime.XDecref(obj);
+                        Runtime.XDecref(obj.PyObj);
                         try
                         {
                             Runtime.CheckExceptionOccurred();
                         }
                         catch (Exception e)
                         {
-                            var errorArgs = new ErrorArgs
-                            {
-                                Error = e,
-                            };
-
-                            ErrorHandler?.Invoke(this, errorArgs);
-
-                            if (!errorArgs.Handled)
-                            {
-                                throw new FinalizationException(
-                                    "Python object finalization failed",
-                                    disposable: obj, innerException: e);
-                            }
+                            HandleFinalizationException(obj.PyObj, e);
                         }
                     }
                 }
@@ -166,6 +173,23 @@ private void DisposeAll()
             }
         }
 
+        void HandleFinalizationException(IntPtr obj, Exception cause)
+        {
+            var errorArgs = new ErrorArgs
+            {
+                Error = cause,
+            };
+
+            ErrorHandler?.Invoke(this, errorArgs);
+
+            if (!errorArgs.Handled)
+            {
+                throw new FinalizationException(
+                    "Python object finalization failed",
+                    disposable: obj, innerException: cause);
+            }
+        }
+
 #if FINALIZER_CHECK
         private void ValidateRefCount()
         {
@@ -235,6 +259,12 @@ private void ValidateRefCount()
 #endif
     }
 
+    struct PendingFinalization
+    {
+        public IntPtr PyObj;
+        public int RuntimeRun;
+    }
+
     public class FinalizationException : Exception
     {
         public IntPtr Handle { get; }
@@ -259,5 +289,21 @@ public FinalizationException(string message, IntPtr disposable, Exception innerE
             if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));
             this.Handle = disposable;
         }
+
+        protected FinalizationException(string message, IntPtr disposable)
+            : base(message)
+        {
+            if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));
+            this.Handle = disposable;
+        }
+    }
+
+    public class RuntimeShutdownException : FinalizationException
+    {
+        public RuntimeShutdownException(IntPtr disposable)
+            : base("Python runtime was shut down after this object was created." +
+                   " It is an error to attempt to dispose or to continue using it even after restarting the runtime.", disposable)
+        {
+        }
     }
 }
diff --git a/src/runtime/pybuffer.cs b/src/runtime/pybuffer.cs
index 7161a864f..94741b19b 100644
--- a/src/runtime/pybuffer.cs
+++ b/src/runtime/pybuffer.cs
@@ -236,11 +236,12 @@ private void Dispose(bool disposing)
 
         ~PyBuffer()
         {
-            if (disposedValue)
+            Debug.Assert(!disposedValue);
+
+            if (_view.obj != IntPtr.Zero)
             {
-                return;
+                Finalizer.Instance.AddFinalizedObject(ref _view.obj, _exporter.run);
             }
-            Finalizer.Instance.AddFinalizedObject(ref _view.obj);
         }
 
         /// <summary>
diff --git a/src/runtime/pyobject.cs b/src/runtime/pyobject.cs
index bd767307b..747b4ecdf 100644
--- a/src/runtime/pyobject.cs
+++ b/src/runtime/pyobject.cs
@@ -1,10 +1,10 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Dynamic;
 using System.Linq;
 using System.Linq.Expressions;
+using System.Threading;
 
 namespace Python.Runtime
 {
@@ -27,6 +27,7 @@ public partial class PyObject : DynamicObject, IDisposable
 #endif  
 
         protected internal IntPtr obj = IntPtr.Zero;
+        internal readonly int run = Runtime.GetRun();
 
         public static PyObject None => new PyObject(new BorrowedReference(Runtime.PyNone));
         internal BorrowedReference Reference => new BorrowedReference(this.obj);
@@ -95,11 +96,19 @@ internal PyObject(in StolenReference reference)
         // when the managed wrapper is garbage-collected.
         ~PyObject()
         {
-            if (obj == IntPtr.Zero)
+            if (obj != IntPtr.Zero)
             {
-                return;
+
+#if TRACE_ALLOC
+                CheckRun();
+#endif
+
+                Interlocked.Increment(ref Runtime._collected);
+
+                Finalizer.Instance.AddFinalizedObject(ref obj, run);
             }
-            Finalizer.Instance.AddFinalizedObject(ref obj);
+
+            Dispose(false);
         }
 
 
@@ -167,17 +176,6 @@ public object AsManagedObject(Type t)
 
         internal bool IsDisposed => obj == IntPtr.Zero;
 
-        /// <summary>
-        /// Dispose Method
-        /// </summary>
-        /// <remarks>
-        /// The Dispose method provides a way to explicitly release the
-        /// Python object represented by a PyObject instance. It is a good
-        /// idea to call Dispose on PyObjects that wrap resources that are
-        /// limited or need strict lifetime control. Otherwise, references
-        /// to Python objects will not be released until a managed garbage
-        /// collection occurs.
-        /// </remarks>
         protected virtual void Dispose(bool disposing)
         {
             if (this.obj == IntPtr.Zero)
@@ -188,6 +186,8 @@ protected virtual void Dispose(bool disposing)
             if (Runtime.Py_IsInitialized() == 0)
                 throw new InvalidOperationException("Python runtime must be initialized");
 
+            CheckRun();
+
             if (!Runtime.IsFinalizing)
             {
                 long refcount = Runtime.Refcount(this.obj);
@@ -221,10 +221,32 @@ protected virtual void Dispose(bool disposing)
             this.obj = IntPtr.Zero;
         }
 
+        /// <summary>
+        /// The Dispose method provides a way to explicitly release the
+        /// Python object represented by a PyObject instance. It is a good
+        /// idea to call Dispose on PyObjects that wrap resources that are
+        /// limited or need strict lifetime control. Otherwise, references
+        /// to Python objects will not be released until a managed garbage
+        /// collection occurs.
+        /// </summary>
         public void Dispose()
         {
+            GC.SuppressFinalize(this);
             Dispose(true);
+        }
+
+        [Obsolete("Test use only")]
+        internal void Leak()
+        {
+            Debug.Assert(obj != IntPtr.Zero);
             GC.SuppressFinalize(this);
+            obj = IntPtr.Zero;
+        }
+
+        internal void CheckRun()
+        {
+            if (run != Runtime.GetRun())
+                throw new RuntimeShutdownException(obj);
         }
 
         internal BorrowedReference GetPythonTypeReference()
diff --git a/src/runtime/pythonengine.cs b/src/runtime/pythonengine.cs
index 91e013e86..6e0057036 100644
--- a/src/runtime/pythonengine.cs
+++ b/src/runtime/pythonengine.cs
@@ -317,6 +317,8 @@ public static IntPtr InitExt()
             {
                 Initialize(setSysArgv: false, mode: ShutdownMode.Extension);
 
+                Finalizer.Instance.ErrorHandler += AllowLeaksDuringShutdown;
+
                 // Trickery - when the import hook is installed into an already
                 // running Python, the standard import machinery is still in
                 // control for the duration of the import that caused bootstrap.
@@ -358,6 +360,14 @@ public static IntPtr InitExt()
                    .DangerousMoveToPointerOrNull();
         }
 
+        private static void AllowLeaksDuringShutdown(object sender, Finalizer.ErrorArgs e)
+        {
+            if (e.Error is RuntimeShutdownException)
+            {
+                e.Handled = true;
+            }
+        }
+
         /// <summary>
         /// Shutdown Method
         /// </summary>
@@ -381,7 +391,6 @@ public static void Shutdown(ShutdownMode mode)
             ExecuteShutdownHandlers();
             // Remember to shut down the runtime.
             Runtime.Shutdown(mode);
-            PyObjectConversions.Reset();
 
             initialized = false;
 
diff --git a/src/runtime/runtime.cs b/src/runtime/runtime.cs
index b4b045b4a..217075494 100644
--- a/src/runtime/runtime.cs
+++ b/src/runtime/runtime.cs
@@ -85,7 +85,16 @@ internal static Version PyVersion
             }
         }
 
-        /// <summary>
+        const string RunSysPropName = "__pythonnet_run__";
+        static int run = 0;
+
+        internal static int GetRun()
+        {
+            int runNumber = run;
+            Debug.Assert(runNumber > 0, "This must only be called after Runtime is initialized at least once");
+            return runNumber;
+        }
+
         /// Initialize the runtime...
         /// </summary>
         /// <remarks>Always call this method from the Main thread.  After the
@@ -110,6 +119,9 @@ internal static void Initialize(bool initSigs = false, ShutdownMode mode = Shutd
             if (!interpreterAlreadyInitialized)
             {
                 Py_InitializeEx(initSigs ? 1 : 0);
+
+                NewRun();
+
                 if (PyEval_ThreadsInitialized() == 0)
                 {
                     PyEval_InitThreads();
@@ -130,10 +142,21 @@ internal static void Initialize(bool initSigs = false, ShutdownMode mode = Shutd
                 {
                     PyGILState_Ensure();
                 }
+
+                BorrowedReference pyRun = PySys_GetObject(RunSysPropName);
+                if (pyRun != null)
+                {
+                    run = checked((int)PyLong_AsSignedSize_t(pyRun));
+                }
+                else
+                {
+                    NewRun();
+                }
             }
             MainManagedThreadId = Thread.CurrentThread.ManagedThreadId;
 
             IsFinalizing = false;
+            Finalizer.Initialize();
             InternString.Initialize();
 
             InitPyMembers();
@@ -175,6 +198,13 @@ internal static void Initialize(bool initSigs = false, ShutdownMode mode = Shutd
             inspect = GetModuleLazy("inspect");
         }
 
+        static void NewRun()
+        {
+            run++;
+            using var pyRun = PyLong_FromLongLong(run);
+            PySys_SetObject(RunSysPropName, pyRun);
+        }
+
         private static void InitPyMembers()
         {
             IntPtr op;
@@ -345,26 +375,29 @@ internal static void Shutdown(ShutdownMode mode)
             PyCLRMetaType = IntPtr.Zero;
 
             Exceptions.Shutdown();
+            PythonEngine.InteropConfiguration.Dispose();
+            DisposeLazyModule(clrInterop);
+            DisposeLazyModule(inspect);
+            PyObjectConversions.Reset();
+
+            if (mode != ShutdownMode.Extension)
+            {
+                PyGC_Collect();
+                bool everythingSeemsCollected = TryCollectingGarbage();
+                Debug.Assert(everythingSeemsCollected);
+            }
+
             Finalizer.Shutdown();
             InternString.Shutdown();
 
             if (mode != ShutdownMode.Normal && mode != ShutdownMode.Extension)
             {
-                PyGC_Collect();
                 if (mode == ShutdownMode.Soft)
                 {
                     RuntimeState.Restore();
                 }
                 ResetPyMembers();
                 GC.Collect();
-                try
-                {
-                    GC.WaitForFullGCComplete();
-                }
-                catch (NotImplementedException)
-                {
-                    // Some clr runtime didn't implement GC.WaitForFullGCComplete yet.
-                }
                 GC.WaitForPendingFinalizers();
                 PyGILState_Release(state);
                 // Then release the GIL for good, if there is somehting to release
@@ -390,12 +423,40 @@ internal static void Shutdown(ShutdownMode mode)
             }
         }
 
+        const int MaxCollectRetriesOnShutdown = 20;
+        internal static int _collected;
+        static bool TryCollectingGarbage()
+        {
+            for (int attempt = 0; attempt < MaxCollectRetriesOnShutdown; attempt++)
+            {
+                Interlocked.Exchange(ref _collected, 0);
+                nint pyCollected = 0;
+                for (int i = 0; i < 2; i++)
+                {
+                    GC.Collect();
+                    GC.WaitForPendingFinalizers();
+                    pyCollected += PyGC_Collect();
+                }
+                if (Volatile.Read(ref _collected) == 0 && pyCollected == 0)
+                    return true;
+            }
+            return false;
+        }
+
         internal static void Shutdown()
         {
             var mode = ShutdownMode;
             Shutdown(mode);
         }
 
+        static void DisposeLazyModule(Lazy<PyObject> module)
+        {
+            if (module.IsValueCreated)
+            {
+                module.Value.Dispose();
+            }
+        }
+
         private static Lazy<PyObject> GetModuleLazy(string moduleName)
             => moduleName is null
                 ? throw new ArgumentNullException(nameof(moduleName))
@@ -777,6 +838,10 @@ internal static unsafe long Refcount(IntPtr op)
             return *p;
         }
 
+        [Pure]
+        internal static long Refcount(BorrowedReference op)
+            => Refcount(op.DangerousGetAddress());
+
         /// <summary>
         /// Call specified function, and handle PythonDLL-related failures.
         /// </summary>
@@ -2171,7 +2236,7 @@ internal static int PyException_SetTraceback(BorrowedReference ex, BorrowedRefer
 
 
 
-        internal static IntPtr PyGC_Collect() => Delegates.PyGC_Collect();
+        internal static nint PyGC_Collect() => Delegates.PyGC_Collect();
 
         internal static IntPtr _Py_AS_GC(BorrowedReference ob)
         {
@@ -2551,7 +2616,7 @@ static Delegates()
                 PyErr_Print = (delegate* unmanaged[Cdecl]<void>)GetFunctionByName(nameof(PyErr_Print), GetUnmanagedDll(_PythonDll));
                 PyCell_Get = (delegate* unmanaged[Cdecl]<BorrowedReference, NewReference>)GetFunctionByName(nameof(PyCell_Get), GetUnmanagedDll(_PythonDll));
                 PyCell_Set = (delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, int>)GetFunctionByName(nameof(PyCell_Set), GetUnmanagedDll(_PythonDll));
-                PyGC_Collect = (delegate* unmanaged[Cdecl]<IntPtr>)GetFunctionByName(nameof(PyGC_Collect), GetUnmanagedDll(_PythonDll));
+                PyGC_Collect = (delegate* unmanaged[Cdecl]<nint>)GetFunctionByName(nameof(PyGC_Collect), GetUnmanagedDll(_PythonDll));
                 PyCapsule_New = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr, NewReference>)GetFunctionByName(nameof(PyCapsule_New), GetUnmanagedDll(_PythonDll));
                 PyCapsule_GetPointer = (delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, IntPtr>)GetFunctionByName(nameof(PyCapsule_GetPointer), GetUnmanagedDll(_PythonDll));
                 PyCapsule_SetPointer = (delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, int>)GetFunctionByName(nameof(PyCapsule_SetPointer), GetUnmanagedDll(_PythonDll));
@@ -2830,7 +2895,7 @@ static Delegates()
             internal static delegate* unmanaged[Cdecl]<void> PyErr_Print { get; }
             internal static delegate* unmanaged[Cdecl]<BorrowedReference, NewReference> PyCell_Get { get; }
             internal static delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, int> PyCell_Set { get; }
-            internal static delegate* unmanaged[Cdecl]<IntPtr> PyGC_Collect { get; }
+            internal static delegate* unmanaged[Cdecl]<nint> PyGC_Collect { get; }
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr, NewReference> PyCapsule_New { get; }
             internal static delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, IntPtr> PyCapsule_GetPointer { get; }
             internal static delegate* unmanaged[Cdecl]<BorrowedReference, IntPtr, int> PyCapsule_SetPointer { get; }

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