@@ -266,9 +266,18 @@ struct _specialization_cache {
     // - If getitem->func_version == getitem_version, then getitem can be called
     //   with two positional arguments and no keyword arguments, and has neither
     //   *args nor **kwargs (as required by BINARY_OP_SUBSCR_GETITEM):
+    // The same contract applies to setitem, except that it is the Python
+    // function that PyType_Lookup(cls, "__setitem__") would return, and it is
+    // called with three positional arguments (as required by
+    // STORE_SUBSCR_PY_DUNDER).
+    // The pointers are grouped ahead of the versions so that the two version
+    // fields share one word of padding, which keeps this struct at 32 bytes
+    // rather than 40.
     PyObject *getitem;
-    uint32_t getitem_version;
+    PyObject *setitem;
     PyObject *init;
+    uint32_t getitem_version;
+    uint32_t setitem_version;
 };
 
 /* The *real* layout of a type object when allocated on the heap */
 
@@ -549,6 +549,7 @@ extern PyObject *_PyInstrumentation_BranchesIterator(PyCodeObject *code);
 struct _PyCode8 _PyCode_DEF(8);
 
 PyAPI_DATA(const struct _PyCode8) _Py_InitCleanup;
+PyAPI_DATA(const struct _PyCode8) _Py_SetItemCleanup;
 
 #ifdef Py_GIL_DISABLED
 
 
@@ -303,6 +303,7 @@ Known values:
     Python 3.16a1 3703 (Replace DELETE_GLOBAL with PUSH_NULL; STORE_GLOBAL)
     Python 3.16a1 3704 (Replace DELETE_ATTR with PUSH_NULL; STORE_ATTR)
     Python 3.16a1 3705 (Add INTRINSIC_ADD_CONDITIONAL_ANNOTATION)
+    Python 3.16a1 3706 (Add STORE_SUBSCR_PY_DUNDER and EXIT_SETITEM)
 
     Python 3.17 will start with 3750
 
@@ -312,7 +313,7 @@ Known values:
 
 */
 
-#define PYC_MAGIC_NUMBER 3705
+#define PYC_MAGIC_NUMBER 3706
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \
 
@@ -164,6 +164,7 @@ typedef int (*_py_validate_type)(PyTypeObject *);
 // Exported for external JIT support
 int _PyType_Validate(PyTypeObject *ty, _py_validate_type validate, unsigned int *tp_version);
 int _PyType_CacheGetItemForSpecialization(PyHeapTypeObject *ht, PyObject *descriptor, uint32_t tp_version);
+int _PyType_CacheSetItemForSpecialization(PyHeapTypeObject *ht, PyObject *descriptor, uint32_t tp_version);
 
 // Precalculates count of non-unique slots and fills wrapperbase.name_count.
 extern int _PyType_InitSlotDefs(PyInterpreterState *interp);