diff --git a/Include/internal/pycore_interp_structs.h b/Include/internal/pycore_interp_structs.h
index 349044116b9d18..cccfe3565db6e0 100644
--- a/Include/internal/pycore_interp_structs.h
+++ b/Include/internal/pycore_interp_structs.h
@@ -525,8 +525,13 @@ struct _py_func_state {
 /****** type state *********/
 
 /* For now we hard-code this to a value for which we are confident
-   all the static builtin types will fit (for all builds). */
-#define _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES 203
+   all the static builtin types will fit (for all builds).
+   If you add a new static type to the standard library, you may have to
+   update one of these numbers.
+   */
+#define _Py_NUM_MANAGED_PREINITIALIZED_TYPES 120
+#define _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES \
+    (_Py_NUM_MANAGED_PREINITIALIZED_TYPES + 83)
 #define _Py_MAX_MANAGED_STATIC_EXT_TYPES 10
 #define _Py_MAX_MANAGED_STATIC_TYPES \
     (_Py_MAX_MANAGED_STATIC_BUILTIN_TYPES + _Py_MAX_MANAGED_STATIC_EXT_TYPES)
diff --git a/InternalDocs/parser.md b/InternalDocs/parser.md
index 1d0ffe6d40d078..1bb4cdea5439f1 100644
--- a/InternalDocs/parser.md
+++ b/InternalDocs/parser.md
@@ -819,6 +819,13 @@ directory on the CPython repository and manually call the parser generator by ex
 $ python -m pegen python <PATH TO YOUR GRAMMAR FILE>
 ```
 
+> [!CAUTION]
+> Python's grammar (the `Grammar/python.gram` file) is written for the
+> C backend. To experiment, you will need to write a grammar
+> without C-specific parts like actions and the trailer.
+> See [#133560](https://github.com/python/cpython/issues/133560) 
+> and [#96424](https://github.com/python/cpython/issues/96424) for more information.
+
 This will generate a file called `parse.py` in the same directory that you
 can use to parse some input:
 
diff --git a/Lib/pdb.py b/Lib/pdb.py
index c4bc0020646b0d..4dd974b375c259 100644
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -376,7 +376,7 @@ def get_default_backend():
 
 def _pyrepl_available():
     """return whether pdb should use _pyrepl for input"""
-    if not os.getenv("PYTHON_BASIC_REPL"):
+    if os.getenv("PYTHON_BASIC_REPL"):
         CAN_USE_PYREPL = False
     else:
         try:
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index c5171f3388c965..db90019975521e 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -4753,6 +4753,16 @@ def foo(self):
         stdout, stderr = self.run_pdb_script(script, commands)
         self.assertIn("The specified object 'C.foo' is not a function", stdout)
 
+    def test_pyrepl_available(self):
+        with patch.dict(os.environ, {"PYTHON_BASIC_REPL": "1"}):
+            self.assertFalse(pdb._pyrepl_available())
+
+        with patch.dict(os.environ, {}, clear=True):
+            mod = types.ModuleType("_pyrepl.main")
+            mod.CAN_USE_PYREPL = True
+            with patch.dict("sys.modules", {"_pyrepl.main": mod}):
+                self.assertTrue(pdb._pyrepl_available())
+
 
 class ChecklineTests(unittest.TestCase):
     def setUp(self):
diff --git a/Misc/NEWS.d/next/Library/2026-04-30-14-21-26.gh-issue-149173.KJqZm0.rst b/Misc/NEWS.d/next/Library/2026-04-30-14-21-26.gh-issue-149173.KJqZm0.rst
new file mode 100644
index 00000000000000..019ab76b863577
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-04-30-14-21-26.gh-issue-149173.KJqZm0.rst
@@ -0,0 +1,2 @@
+Fix inverted :envvar:`PYTHON_BASIC_REPL` environment check in
+``pdb._pyrepl_available``.
diff --git a/Objects/object.c b/Objects/object.c
index e6a764435bc292..e0e26bb50d3653 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -2526,7 +2526,7 @@ extern PyTypeObject _PyMemoryIter_Type;
 extern PyTypeObject _PyPositionsIterator;
 extern PyTypeObject _Py_GenericAliasIterType;
 
-static PyTypeObject* static_types[] = {
+static PyTypeObject* static_types[_Py_NUM_MANAGED_PREINITIALIZED_TYPES] = {
     // The two most important base types: must be initialized first and
     // deallocated last.
     &PyBaseObject_Type,
@@ -2644,6 +2644,9 @@ static PyTypeObject* static_types[] = {
     &_PyUnion_Type,
 #ifdef _Py_TIER2
     &_PyUOpExecutor_Type,
+#else
+    // The array should have the same size on all builds; see gh-149139
+    NULL,
 #endif
     &_PyWeakref_CallableProxyType,
     &_PyWeakref_ProxyType,
@@ -2668,6 +2671,9 @@ _PyTypes_InitTypes(PyInterpreterState *interp)
     // All other static types (unless initialized elsewhere)
     for (size_t i=0; i < Py_ARRAY_LENGTH(static_types); i++) {
         PyTypeObject *type = static_types[i];
+        if (type == NULL) {
+            continue;
+        }
         if (_PyStaticType_InitBuiltin(interp, type) < 0) {
             return _PyStatus_ERR("Can't initialize builtin type");
         }
@@ -2708,6 +2714,9 @@ _PyTypes_FiniTypes(PyInterpreterState *interp)
     // their base classes.
     for (Py_ssize_t i=Py_ARRAY_LENGTH(static_types)-1; i>=0; i--) {
         PyTypeObject *type = static_types[i];
+        if (type == NULL) {
+            continue;
+        }
         _PyStaticType_FiniBuiltin(interp, type);
     }
 }