diff --git a/pcapkit/const/reg/apptype/apptype.py b/pcapkit/const/reg/apptype/apptype.py
index 76cd73e5e..e2c16d2ef 100644
--- a/pcapkit/const/reg/apptype/apptype.py
+++ b/pcapkit/const/reg/apptype/apptype.py
@@ -90,7 +90,7 @@ def _missing_(cls, value: 'int') -> 'TransportProtocol':
 
         """
         if not (isinstance(value, int) and 0 <= value <= max(cls.__members__.values()) * 2 - 1):
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{value!r} is not a valid {cls.__name__}')
         return super()._missing_(value)
 
 
@@ -2306,8 +2306,8 @@ def __new__(cls, value: 'int', name: 'str' = '<null>',
         # two services on one port stay two canonical members instead of one
         # member and an alias -- an alias would answer to the other's name.
         if cls.__registry__ is None:
-            raise ValueError('%s holds no members; they belong to its per-transport '
-                             'subclasses' % cls.__name__)
+            raise ValueError(f'{cls.__name__} holds no members; they belong to its per-transport '
+                             'subclasses')
         cls.__registry__.add(value, obj)
 
         return obj
@@ -2372,7 +2372,7 @@ def _dispatch(cls, key: 'int', proto: 'TransportProtocol | str') -> 'Type[AppTyp
         # non-port outright is the honest answer, and it has to happen before the
         # miss path, which formats ``key`` with ``%d``.
         if not isinstance(key, int):
-            raise ValueError('%r is not a valid port number for %s' % (key, cls.__name__))
+            raise ValueError(f'{key!r} is not a valid port number for {cls.__name__}')
         if cls.__registry__ is not None:
             return cls
 
@@ -2417,8 +2417,8 @@ def _dispatch(cls, key: 'int', proto: 'TransportProtocol | str') -> 'Type[AppTyp
             subclass = cls.__registries__.get(TransportProtocol(namespaces[0]))
             if subclass is not None:
                 return subclass
-        raise ValueError('%r names no transport protocol registry of %s'
-                         % (proto, cls.__name__))
+        raise ValueError(f'{proto!r} names no transport protocol registry of '
+                         f'{cls.__name__}')
 
     @classmethod
     def get(cls, key: 'int', *,
@@ -2525,13 +2525,13 @@ def _missing_(cls, value: 'int') -> 'Optional[AppType]':
 
         """
         if not (isinstance(value, int) and 0 <= value <= 65535):
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{value!r} is not a valid {cls.__name__}')
         # NOTE: extending this class would give it a member, and aenum then
         # refuses to subclass it -- permanently, for every registry not yet
         # imported. The spans below belong to whichever registry was asked, never
         # to this one.
         if cls.__registry__ is None:
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{value!r} is not a valid {cls.__name__}')
         # NOTE: most spans are IANA's unassigned and reserved markers, which name
         # no transport protocol and so answer every registry. A span that does name
         # one tests ``cls.__transport__`` and answers that registry alone --
diff --git a/pcapkit/vendor/reg/apptype/apptype.py b/pcapkit/vendor/reg/apptype/apptype.py
index 2b8ca27ed..b6b52cf14 100644
--- a/pcapkit/vendor/reg/apptype/apptype.py
+++ b/pcapkit/vendor/reg/apptype/apptype.py
@@ -183,7 +183,7 @@ def _missing_(cls, value: 'int') -> 'TransportProtocol':
 
         """
         if not (isinstance(value, int) and 0 <= value <= max(cls.__members__.values()) * 2 - 1):
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{{value!r}} is not a valid {{cls.__name__}}')
         return super()._missing_(value)
 
 
@@ -261,8 +261,8 @@ def __new__(cls, value: 'int', name: 'str' = '<null>',
         # two services on one port stay two canonical members instead of one
         # member and an alias -- an alias would answer to the other's name.
         if cls.__registry__ is None:
-            raise ValueError('%s holds no members; they belong to its per-transport '
-                             'subclasses' % cls.__name__)
+            raise ValueError(f'{{cls.__name__}} holds no members; they belong to its per-transport '
+                             'subclasses')
         cls.__registry__.add(value, obj)
 
         return obj
@@ -327,7 +327,7 @@ def _dispatch(cls, key: 'int', proto: 'TransportProtocol | str') -> 'Type[{NAME}
         # non-port outright is the honest answer, and it has to happen before the
         # miss path, which formats ``key`` with ``%d``.
         if not isinstance(key, int):
-            raise ValueError('%r is not a valid port number for %s' % (key, cls.__name__))
+            raise ValueError(f'{{key!r}} is not a valid port number for {{cls.__name__}}')
         if cls.__registry__ is not None:
             return cls
 
@@ -372,8 +372,8 @@ def _dispatch(cls, key: 'int', proto: 'TransportProtocol | str') -> 'Type[{NAME}
             subclass = cls.__registries__.get(TransportProtocol(namespaces[0]))
             if subclass is not None:
                 return subclass
-        raise ValueError('%r names no transport protocol registry of %s'
-                         % (proto, cls.__name__))
+        raise ValueError(f'{{proto!r}} names no transport protocol registry of '
+                         f'{{cls.__name__}}')
 
     @classmethod
     def get(cls, key: 'int', *,
@@ -480,13 +480,13 @@ def _missing_(cls, value: 'int') -> 'Optional[{NAME}]':
 
         """
         if not ({FLAG}):
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{{value!r}} is not a valid {{cls.__name__}}')
         # NOTE: extending this class would give it a member, and aenum then
         # refuses to subclass it -- permanently, for every registry not yet
         # imported. The spans below belong to whichever registry was asked, never
         # to this one.
         if cls.__registry__ is None:
-            raise ValueError('%r is not a valid %s' % (value, cls.__name__))
+            raise ValueError(f'{{value!r}} is not a valid {{cls.__name__}}')
         # NOTE: most spans are IANA's unassigned and reserved markers, which name
         # no transport protocol and so answer every registry. A span that does name
         # one tests ``cls.__transport__`` and answers that registry alone --
diff --git a/tests/const/test_const_enum_builtin_parity.py b/tests/const/test_const_enum_builtin_parity.py
index 83e855bee..805fa91e7 100644
--- a/tests/const/test_const_enum_builtin_parity.py
+++ b/tests/const/test_const_enum_builtin_parity.py
@@ -98,12 +98,24 @@
 #: The bespoke templates under :mod:`pcapkit.vendor` that carry their own copy of
 #: the guard, rather than inheriting the one in :mod:`pcapkit.vendor.default`.
 #: Each was rendering a registry that GitHub issue #647 found unguarded.
-BESPOKE_TEMPLATES = (
-    'pcapkit.vendor.tcp.flags',
-    'pcapkit.vendor.ftp.command',
-    'pcapkit.vendor.http.method',
-    'pcapkit.vendor.reg.apptype.apptype',
-)
+#:
+#: Keyed to each template's own guard text rather than one literal shared by
+#: all four: GitHub issue #792 moved ``pcapkit.vendor.reg.apptype.apptype``'s
+#: copy to an f-string, following the library-wide convention GitHub issue
+#: #783 settled, while the other three still raise with ``%`` -- #792
+#: deliberately left them alone so the ``const`` diff stayed reviewable, and
+#: #798 tracks sweeping them, along with the ``%``-formatted dunders and
+#: dropping the f-string disable. One shared literal can no longer pin all four;
+#: what #647 actually needs pinned is that each template still carries *a*
+#: guard rejecting an invalid value, in whatever form that template's own
+#: raise takes, not that the four agree on a formatting style the library is
+#: moving away from.
+BESPOKE_TEMPLATES = {
+    'pcapkit.vendor.tcp.flags': "raise ValueError('%r is not a valid %s' % (value, cls.__name__))",
+    'pcapkit.vendor.ftp.command': "raise ValueError('%r is not a valid %s' % (value, cls.__name__))",
+    'pcapkit.vendor.http.method': "raise ValueError('%r is not a valid %s' % (value, cls.__name__))",
+    'pcapkit.vendor.reg.apptype.apptype': "raise ValueError(f'{{value!r}} is not a valid {{cls.__name__}}')",
+}
 
 
 class _StdIntEnum(enum.IntEnum):
@@ -577,7 +589,9 @@ class ConstEnumGuardTemplateTests(unittest.TestCase):
     agree with it -- the next crawl would simply revert them. The four templates
     below each carry their own copy of the guard rather than inheriting the one
     in :mod:`pcapkit.vendor.default`, which is why all four had to be edited and
-    why all four are checked.
+    why all four are checked -- each against its own guard text now that
+    GitHub issue #792 moved one of them off ``%`` formatting, per
+    :data:`BESPOKE_TEMPLATES`.
     """
 
     def setUp(self) -> None:
@@ -586,13 +600,12 @@ def setUp(self) -> None:
     @unittest.skipUnless(importlib.util.find_spec('requests') is not None,
                          'pcapkit.vendor needs requests')
     def test_every_bespoke_template_carries_the_guard(self) -> None:
-        for module_name in BESPOKE_TEMPLATES:
+        for module_name, guard in BESPOKE_TEMPLATES.items():
             with self.subTest(vendor=module_name):
                 source = inspect.getsource(importlib.import_module(module_name))
                 self.assertIn(
-                    "raise ValueError('%r is not a valid %s' % (value, cls.__name__))",
-                    source, f'{module_name} no longer emits the guard; '
-                            f'see GitHub issue #647')
+                    guard, source, f'{module_name} no longer emits its guard; '
+                                   f'see GitHub issue #647')
 
     @unittest.skipUnless(importlib.util.find_spec('requests') is not None,
                          'pcapkit.vendor needs requests')