AtwoodTM · Oct 6, 2026 · Oct 6, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,8 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
 
 ### Fixed
 
+- When `BinaryFormatter` is unavailable, skip publishing `sys.clr_data` during
+  `Shutdown` so the next `Initialize` does not deserialize an empty capsule (#2282)
 
 ## 3.2.0 - 2026-09-29
 

diff --git a/src/embed_tests/Python.EmbeddingTest.csproj b/src/embed_tests/Python.EmbeddingTest.csproj
@@ -19,6 +19,11 @@
     <Compile Remove="NeedsReinit/*.cs" />
   </ItemGroup>
 
+  <!-- net472 still stashes with BinaryFormatter. This test covers the Noop path. -->
+  <ItemGroup Condition="'$(TargetFramework)' == 'net472'">
+    <Compile Remove="StateSerialization/ShutdownStash.cs" />
+  </ItemGroup>
+
   <PropertyGroup>
     <DefineConstants>$(DefineConstants);$(ConfiguredConstants)</DefineConstants>
   </PropertyGroup>

diff --git a/src/embed_tests/StateSerialization/ShutdownStash.cs b/src/embed_tests/StateSerialization/ShutdownStash.cs
@@ -0,0 +1,57 @@
+using System;
+
+using NUnit.Framework;
+
+using Python.Runtime;
+
+namespace Python.EmbeddingTest.StateSerialization;
+
+/// <summary>
+/// Regression for https://github.com/pythonnet/pythonnet/issues/2282.
+/// When BinaryFormatter cannot run, Shutdown must not throw and must not
+/// leave a sys.clr_data capsule behind.
+/// </summary>
+public class ShutdownStash
+{
+    [Test]
+    public void ShutdownLeavesNoClrData()
+    {
+        if (!PythonEngine.IsInitialized)
+        {
+            PythonEngine.Initialize();
+        }
+
+        Assert.That(RuntimeData.CreateFormatter(), Is.InstanceOf<NoopFormatter>());
+
+        using (Py.GIL())
+        {
+            using var wrapped = new UriBuilder().ToPython();
+            Assert.That(RuntimeData.HasStashData(), Is.False);
+        }
+
+        try
+        {
+            PythonEngine.Shutdown();
+
+            using (Py.GIL())
+            {
+                Assert.That(RuntimeData.HasStashData(), Is.False);
+            }
+        }
+        finally
+        {
+            // Shutdown leaves the interpreter alive. A second Shutdown in this
+            // process then deallocates types from the previous runtime and
+            // trips MetaType.tp_dealloc. Finish the interpreter first so the
+            // suite, and GlobalTestsSetup, start from a new one.
+            if (Runtime.Runtime.Py_IsInitialized() != 0)
+            {
+                Runtime.Runtime.Py_Finalize();
+            }
+            if (!PythonEngine.IsInitialized)
+            {
+                PythonEngine.Initialize();
+            }
+        }
+    }
+}
diff --git a/src/runtime/StateSerialization/RuntimeData.cs b/src/runtime/StateSerialization/RuntimeData.cs
@@ -84,6 +84,19 @@ static void ClearCLRData ()
 
         internal static void Stash()
         {
+            IFormatter formatter = CreateFormatter();
+            // NoopFormatter.Serialize writes nothing. An empty sys.clr_data capsule
+            // makes the next Initialize call Deserialize and throw (#2282).
+            if (formatter is NoopFormatter)
+            {
+                if (HasStashData())
+                {
+                    ClearCLRData();
+                    ClearStash();
+                }
+                return;
+            }
+
             var runtimeStorage = new PythonNetState
             {
                 Metatype = MetaType.SaveRuntimeData(),
@@ -93,7 +106,6 @@ internal static void Stash()
                 SharedObjects = SaveRuntimeDataObjects(),
             };
 
-            IFormatter formatter = CreateFormatter();
             var ms = new MemoryStream();
             formatter.Serialize(ms, runtimeStorage);