Sync pre-release CPython main branch from GitHub (2026-06-26)

Summary:
Imported python/cpython `3.16.0a0` from upstream rev [`1812162`](https://www.github.com/python/cpython/commit/1812162f81ef034616294ec9ee53e951f99c9582) (committed 2026-06-26 23:27:47+00:00).

# Commit Info

- Base: (`3.16.0a0`) - [`285d96d`](https://www.github.com/python/cpython/commit/285d96dd784620fe8afb02688abe72a916555061) (commit date: 2026-06-26 04:48:53+00:00)
- Imported: (`3.16.0a0`) - [`1812162`](https://www.github.com/python/cpython/commit/1812162f81ef034616294ec9ee53e951f99c9582) (commit date: 2026-06-26 23:27:47+00:00)

# Noteworthy file changes

- Low-signal files (15 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GI4dCSCsO9K7u40DAIYeZeqvCoY0br0LAAAz

Differential Revision: D109921298

fbshipit-source-id: 338022c9bbcda5d8871b1c78086a1db9098b1983

Author: generatedunixname1734921407115435

cinderx/Interpreter/3.16/Includes/generated_cases.c.h

@@ -10871,7 +10871,18 @@
                     JUMP_TO_PREDICTED(LOAD_ATTR);
                 }
             }
-            /* Skip 2 cache entries */
+            // _GUARD_KEYS_VERSION
+            {
+                uint32_t keys_version = read_u32(&this_instr[4].cache);
+                PyTypeObject *owner_cls = Py_TYPE(PyStackRef_AsPyObjectBorrow(owner));
+                PyHeapTypeObject *owner_heap_type = (PyHeapTypeObject *)owner_cls;
+                PyDictKeysObject *keys = owner_heap_type->ht_cached_keys;
+                if (FT_ATOMIC_LOAD_UINT32_RELAXED(keys->dk_version) != keys_version) {
+                    UPDATE_MISS_STATS(LOAD_ATTR);
+                    assert(_PyOpcode_Deopt[opcode] == (LOAD_ATTR));
+                    JUMP_TO_PREDICTED(LOAD_ATTR);
+                }
+            }
             // _LOAD_ATTR_METHOD_WITH_VALUES
             {
                 PyObject *descr = read_obj(&this_instr[6].cache);
@@ -11056,7 +11067,18 @@
                     JUMP_TO_PREDICTED(LOAD_ATTR);
                 }
             }
-            /* Skip 2 cache entries */
+            // _GUARD_KEYS_VERSION
+            {
+                uint32_t keys_version = read_u32(&this_instr[4].cache);
+                PyTypeObject *owner_cls = Py_TYPE(PyStackRef_AsPyObjectBorrow(owner));
+                PyHeapTypeObject *owner_heap_type = (PyHeapTypeObject *)owner_cls;
+                PyDictKeysObject *keys = owner_heap_type->ht_cached_keys;
+                if (FT_ATOMIC_LOAD_UINT32_RELAXED(keys->dk_version) != keys_version) {
+                    UPDATE_MISS_STATS(LOAD_ATTR);
+                    assert(_PyOpcode_Deopt[opcode] == (LOAD_ATTR));
+                    JUMP_TO_PREDICTED(LOAD_ATTR);
+                }
+            }
             // _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES
             {
                 PyObject *descr = read_obj(&this_instr[6].cache);