diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 0115c57..6f55adb 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -33,7 +33,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install ruff
+        python -m pip install ruff ty
 
     - name: Lint with Ruff on a basic set of rules
       run: |
@@ -42,3 +42,7 @@ jobs:
     - name: Lint with Ruff on an extended ruleset but always return success
       run: |
         ruff check libdestruct --output-format=github --exit-zero
+
+    - name: Type check with ty
+      run: |
+        ty check --output-format=github
diff --git a/libdestruct/__init__.py b/libdestruct/__init__.py
index c66dcc4..14bbf89 100644
--- a/libdestruct/__init__.py
+++ b/libdestruct/__init__.py
@@ -5,7 +5,7 @@
 #
 
 try:  # pragma: no cover
-    from rich.traceback import install
+    from rich.traceback import install  # ty: ignore[unresolved-import]
 
     install()
 except ImportError:  # pragma: no cover
diff --git a/libdestruct/backing/fake_resolver.py b/libdestruct/backing/fake_resolver.py
index 637e67f..2e7946a 100644
--- a/libdestruct/backing/fake_resolver.py
+++ b/libdestruct/backing/fake_resolver.py
@@ -6,13 +6,15 @@
 
 from __future__ import annotations
 
+from typing import Literal
+
 from libdestruct.backing.resolver import Resolver
 
 
 class FakeResolver(Resolver):
     """A class that can resolve elements in a simulated memory storage."""
 
-    def __init__(self: FakeResolver, memory: dict | None = None, address: int | None = 0, endianness: str = "little") -> None:
+    def __init__(self: FakeResolver, memory: dict | None = None, address: int | None = 0, endianness: Literal["little", "big"] = "little") -> None:
         """Initializes a basic fake resolver."""
         self.memory = memory if memory is not None else {}
         self.address = address
diff --git a/libdestruct/backing/memory_resolver.py b/libdestruct/backing/memory_resolver.py
index 34c559d..4b90a8d 100644
--- a/libdestruct/backing/memory_resolver.py
+++ b/libdestruct/backing/memory_resolver.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from libdestruct.backing.resolver import Resolver
 
@@ -17,7 +17,7 @@
 class MemoryResolver(Resolver):
     """A class that can resolve itself to a value in a referenced memory storage."""
 
-    def __init__(self: MemoryResolver, memory: MutableSequence, address: int | None, endianness: str = "little") -> None:
+    def __init__(self: MemoryResolver, memory: MutableSequence, address: int | None, endianness: Literal["little", "big"] = "little") -> None:
         """Initializes a basic memory resolver."""
         self.memory = memory
         self.address = address
diff --git a/libdestruct/backing/resolver.py b/libdestruct/backing/resolver.py
index 32612f9..fbeae16 100644
--- a/libdestruct/backing/resolver.py
+++ b/libdestruct/backing/resolver.py
@@ -7,6 +7,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
+from typing import Literal
 
 from typing_extensions import Self
 
@@ -16,7 +17,7 @@ class Resolver(ABC):
 
     parent: Self
 
-    endianness: str = "little"
+    endianness: Literal["little", "big"] = "little"
     """The endianness of the data this resolver accesses."""
 
     @abstractmethod
diff --git a/libdestruct/c/c_integer_types.py b/libdestruct/c/c_integer_types.py
index bf76989..2759348 100644
--- a/libdestruct/c/c_integer_types.py
+++ b/libdestruct/c/c_integer_types.py
@@ -28,6 +28,7 @@ def get(self: _c_integer) -> int:
     def to_bytes(self: _c_integer) -> bytes:
         """Return the serialized representation of the object."""
         if self._frozen:
+            assert isinstance(self._frozen_value, int)
             return self._frozen_value.to_bytes(self.size, self.endianness, signed=self.signed)
 
         return self.resolver.resolve(self.size, 0)
diff --git a/libdestruct/c/c_str.py b/libdestruct/c/c_str.py
index 3895a31..207c45d 100644
--- a/libdestruct/c/c_str.py
+++ b/libdestruct/c/c_str.py
@@ -6,6 +6,8 @@
 
 from __future__ import annotations
 
+from collections.abc import Iterator
+
 from libdestruct.common.array.array import array
 
 
@@ -54,7 +56,7 @@ def __setitem__(self: c_str, index: int, value: bytes) -> None:
         """Set the character at the given index to the given value."""
         self._set(value, index)
 
-    def __iter__(self: c_str) -> iter:
+    def __iter__(self: c_str) -> Iterator:
         """Return an iterator over the string."""
         for i in range(self.count()):
             yield self.get(i)
diff --git a/libdestruct/common/array/array.py b/libdestruct/common/array/array.py
index e204302..72c3ad6 100644
--- a/libdestruct/common/array/array.py
+++ b/libdestruct/common/array/array.py
@@ -7,6 +7,7 @@
 from __future__ import annotations
 
 from abc import abstractmethod
+from collections.abc import Iterator
 from types import GenericAlias
 
 from libdestruct.common.obj import obj
@@ -42,7 +43,7 @@ def __setitem__(self: array, index: int, value: object) -> None:
         self.set(index, value)
 
     @abstractmethod
-    def __iter__(self: array) -> iter:
+    def __iter__(self: array) -> Iterator:
         """Return an iterator over the array."""
 
     def __contains__(self: array, value: object) -> bool:
diff --git a/libdestruct/common/enum/enum.py b/libdestruct/common/enum/enum.py
index 7aac7af..2a37eca 100644
--- a/libdestruct/common/enum/enum.py
+++ b/libdestruct/common/enum/enum.py
@@ -30,8 +30,8 @@ def __class_getitem__(cls, params: tuple) -> GenericAlias:
     python_enum: type[Enum]
     """The backing Python enum."""
 
-    _backing_type: type[obj]
-    """The backing type."""
+    _backing_type: obj
+    """The inflated backing instance."""
 
     lenient: bool
     """Whether the conversion is lenient or not."""
diff --git a/libdestruct/common/enum/int_enum_field.py b/libdestruct/common/enum/int_enum_field.py
index a9ead12..136af8b 100644
--- a/libdestruct/common/enum/int_enum_field.py
+++ b/libdestruct/common/enum/int_enum_field.py
@@ -58,7 +58,7 @@ def __init__(
             case _:
                 raise ValueError("The size of the field must be a power of 2.")
 
-    def inflate(self: IntEnumField, resolver: Resolver) -> int:
+    def inflate(self: IntEnumField, resolver: Resolver) -> enum:
         """Inflate the field.
 
         Args:
diff --git a/libdestruct/common/flags/flags.py b/libdestruct/common/flags/flags.py
index eb324de..982b58e 100644
--- a/libdestruct/common/flags/flags.py
+++ b/libdestruct/common/flags/flags.py
@@ -30,8 +30,8 @@ def __class_getitem__(cls, params: tuple) -> GenericAlias:
     python_flag: type[IntFlag]
     """The backing Python IntFlag."""
 
-    _backing_type: type[obj]
-    """The backing type."""
+    _backing_type: obj
+    """The inflated backing instance."""
 
     lenient: bool
     """Whether the conversion is lenient or not."""
diff --git a/libdestruct/common/inflater.py b/libdestruct/common/inflater.py
index ff457c8..e34ed64 100644
--- a/libdestruct/common/inflater.py
+++ b/libdestruct/common/inflater.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from libdestruct.backing.memory_resolver import MemoryResolver
 from libdestruct.common.type_registry import TypeRegistry
@@ -21,7 +21,7 @@
 class Inflater:
     """The memory manager, which inflates any memory-referencing type."""
 
-    def __init__(self: Inflater, memory: MutableSequence, endianness: str = "little") -> None:
+    def __init__(self: Inflater, memory: MutableSequence, endianness: Literal["little", "big"] = "little") -> None:
         """Initialize the memory manager."""
         self.memory = memory
         self.endianness = endianness
diff --git a/libdestruct/common/obj.py b/libdestruct/common/obj.py
index 4f59bbd..8e61001 100644
--- a/libdestruct/common/obj.py
+++ b/libdestruct/common/obj.py
@@ -7,7 +7,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import TYPE_CHECKING, Generic, TypeVar
+from typing import TYPE_CHECKING, Generic, Literal, TypeVar
 
 from libdestruct.common.hexdump import format_hexdump
 
@@ -19,7 +19,7 @@
 class obj(ABC, Generic[T]):
     """A generic object, with reference to the backing memory view."""
 
-    endianness: str = "little"
+    endianness: Literal["little", "big"] = "little"
     """The endianness of the backing reference view."""
 
     resolver: Resolver
@@ -31,7 +31,7 @@ class obj(ABC, Generic[T]):
     _frozen_value: object = None
     """The frozen value of the object."""
 
-    def __init__(self: obj, resolver: Resolver) -> None:
+    def __init__(self: obj, resolver: Resolver | None) -> None:
         """Initialize a generic object.
 
         Args:
@@ -59,7 +59,7 @@ def to_bytes(self: obj) -> bytes:
         """Serialize the object to bytes."""
 
     @classmethod
-    def from_bytes(cls: type[obj], data: bytes, endianness: str = "little") -> obj:
+    def from_bytes(cls: type[obj], data: bytes, endianness: Literal["little", "big"] = "little") -> obj:
         """Deserialize the object from bytes."""
         from libdestruct.libdestruct import inflater
 
diff --git a/libdestruct/common/ptr/ptr.py b/libdestruct/common/ptr/ptr.py
index b550905..f884718 100644
--- a/libdestruct/common/ptr/ptr.py
+++ b/libdestruct/common/ptr/ptr.py
@@ -67,9 +67,10 @@ def get(self: ptr) -> int:
         value = self.resolver.resolve(self.size, 0)
         return int.from_bytes(value, self.endianness)
 
-    def to_bytes(self: obj) -> bytes:
+    def to_bytes(self: ptr) -> bytes:
         """Return the serialized representation of the object."""
         if self._frozen:
+            assert isinstance(self._frozen_value, int)
             return self._frozen_value.to_bytes(self.size, self.endianness)
 
         return self.resolver.resolve(self.size, 0)
@@ -159,7 +160,7 @@ def __sub__(self: ptr, n: int) -> ptr:
         new_addr = self.get() - n * self._element_size
         return ptr(_ArithmeticResolver(self.resolver, new_addr), self.wrapper)
 
-    def __getitem__(self: ptr, n: int) -> obj:
+    def __getitem__(self: ptr, n: int) -> obj | bytes:
         """Return the object at index n relative to this pointer."""
         return (self + n).unwrap()
 
diff --git a/libdestruct/common/struct/struct.py b/libdestruct/common/struct/struct.py
index 2d812d6..ee57785 100644
--- a/libdestruct/common/struct/struct.py
+++ b/libdestruct/common/struct/struct.py
@@ -6,7 +6,7 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, Literal
 
 from libdestruct.common.obj import obj
 from libdestruct.common.type_registry import TypeRegistry
@@ -23,14 +23,14 @@ def __init__(self: struct) -> None:
         """Initialize the struct."""
         raise RuntimeError("This type should not be directly instantiated.")
 
-    def __new__(cls: type[struct], *args: ..., **kwargs: ...) -> struct:  # noqa: PYI034
+    def __new__(cls: type[struct], *args: Any, **kwargs: Any) -> struct:  # noqa: PYI034
         """Create a new struct."""
         # Look for an inflater for this struct
         type_impl = TypeRegistry().inflater_for(cls)
         return type_impl(*args, **kwargs)
 
     @classmethod
-    def from_bytes(cls: type[struct], data: bytes, endianness: str = "little") -> struct_impl:
+    def from_bytes(cls: type[struct], data: bytes, endianness: Literal["little", "big"] = "little") -> struct_impl:
         """Create a struct from a serialized representation."""
         type_inflater = inflater(data, endianness=endianness)
 
diff --git a/libdestruct/common/struct/struct_impl.py b/libdestruct/common/struct/struct_impl.py
index 7ef8c02..f81f002 100644
--- a/libdestruct/common/struct/struct_impl.py
+++ b/libdestruct/common/struct/struct_impl.py
@@ -7,7 +7,7 @@
 from __future__ import annotations
 
 from types import GenericAlias
-from typing import Annotated, get_args, get_origin
+from typing import Annotated, Any, get_args, get_origin
 
 from typing_extensions import Self
 
@@ -37,7 +37,7 @@ class struct_impl(struct):
     _inflater: TypeRegistry = TypeRegistry()
     """The type registry, used for inflating the attributes."""
 
-    def __init__(self: struct_impl, resolver: Resolver | None = None, **kwargs: ...) -> None:
+    def __init__(self: struct_impl, resolver: Resolver | None = None, **kwargs: Any) -> None:
         """Initialize the struct implementation."""
         # If we have kwargs and the resolver is None, we provide a fake resolver
         if kwargs and resolver is None:
@@ -80,7 +80,7 @@ def __setattr__(self: struct_impl, name: str, value: object) -> None:
             pass
         object.__setattr__(self, name, value)
 
-    def __new__(cls: struct_impl, *args: ..., **kwargs: ...) -> Self:
+    def __new__(cls: struct_impl, *args: Any, **kwargs: Any) -> Self:
         """Create a new struct."""
         # Skip the __new__ method of the parent class
         # struct_impl -> struct -> obj becomes struct_impl -> obj
diff --git a/libdestruct/common/union/union.py b/libdestruct/common/union/union.py
index 9e73f04..2e9fc6e 100644
--- a/libdestruct/common/union/union.py
+++ b/libdestruct/common/union/union.py
@@ -94,7 +94,7 @@ def freeze(self: union) -> None:
             v.freeze()
         super().freeze()
 
-    def diff(self: union) -> tuple[object, object]:
+    def diff(self: union) -> tuple[object, object] | dict[str, tuple[object, object]]:
         """Return the difference between the frozen and current value."""
         if self._variant is not None:
             return self._variant.diff()
diff --git a/libdestruct/common/utils.py b/libdestruct/common/utils.py
index d37836a..e365303 100644
--- a/libdestruct/common/utils.py
+++ b/libdestruct/common/utils.py
@@ -15,7 +15,7 @@
 from libdestruct.common.type_registry import TypeRegistry
 
 if TYPE_CHECKING:  # pragma: no cover
-    from collections.abc import Generator
+    from collections.abc import Callable, Generator
 
     from libdestruct.backing.resolver import Resolver
     from libdestruct.common.obj import obj
@@ -26,7 +26,7 @@ def is_field_bound_method(item: obj) -> bool:
     return isinstance(item, MethodType) and isinstance(item.__self__, Field)
 
 
-def size_of(item_or_inflater: obj | callable[[Resolver], obj]) -> int:
+def size_of(item_or_inflater: obj | Callable[[Resolver], obj]) -> int:
     """Return the size in bytes of a type, instance, or field descriptor."""
     # Field instances (e.g. array_of, ptr_to) — must come before .size check
     if isinstance(item_or_inflater, Field):
diff --git a/libdestruct/libdestruct.py b/libdestruct/libdestruct.py
index 04f05ee..22bbaab 100644
--- a/libdestruct/libdestruct.py
+++ b/libdestruct/libdestruct.py
@@ -9,7 +9,7 @@
 import mmap
 from collections.abc import Sequence
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from typing_extensions import Self
 
@@ -25,7 +25,7 @@
 _VALID_ENDIANNESS = ("little", "big")
 
 
-def inflater(memory: Sequence | mmap.mmap, endianness: str = "little") -> Inflater:
+def inflater(memory: Sequence | mmap.mmap, endianness: Literal["little", "big"] = "little") -> Inflater:
     """Return a TypeInflater instance."""
     if not isinstance(memory, Sequence | mmap.mmap):
         raise TypeError(f"memory must be a Sequence, not {type(memory).__name__}")
@@ -43,7 +43,7 @@ def __init__(
         self: FileInflater,
         file_handle: io.BufferedReader,
         mmap_obj: mmap.mmap,
-        endianness: str = "little",
+        endianness: Literal["little", "big"] = "little",
     ) -> None:
         """Initialize the file-backed inflater."""
         super().__init__(mmap_obj, endianness=endianness)
@@ -60,7 +60,7 @@ def __exit__(self: FileInflater, *args: object) -> None:
         self._file_handle.close()
 
 
-def inflater_from_file(path: str, writable: bool = False, endianness: str = "little") -> FileInflater:
+def inflater_from_file(path: str, writable: bool = False, endianness: Literal["little", "big"] = "little") -> FileInflater:
     """Create an inflater backed by a memory-mapped file.
 
     Args:
@@ -81,7 +81,7 @@ def inflater_from_file(path: str, writable: bool = False, endianness: str = "lit
     return FileInflater(file_handle, mmap_obj, endianness=endianness)
 
 
-def inflate(item: type, memory: Sequence, address: int | Resolver, endianness: str = "little") -> obj:
+def inflate(item: type, memory: Sequence, address: int | Resolver, endianness: Literal["little", "big"] = "little") -> obj:
     """Inflate a memory-referencing type.
 
     Args:
diff --git a/pyproject.toml b/pyproject.toml
index 06dd261..f4a6417 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -34,11 +34,38 @@ dependencies = ["typing_extensions", "pycparser"]
 [project.optional-dependencies]
 dev = [
     "rich",
+    "ty",
 ]
 
 [tool.setuptools.packages.find]
 include = ["libdestruct*"]
 
+[tool.ty.src]
+exclude = ["test/", "build/"]
+
+[tool.ty.rules]
+# -- Dynamic metaclass/descriptor inflation pattern --
+# The type registry, struct metaclass, and descriptor protocol resolve attributes
+# at runtime in ways that ty cannot yet follow (_type_impl, _member_offsets, etc).
+unresolved-attribute = "ignore"
+
+# -- Rules that caught real bugs --
+# Keep as warn until annotations are improved, then promote to error.
+invalid-return-type = "warn"       # union.diff() returns dict, ptr.__getitem__ returns bytes
+invalid-argument-type = "warn"     # union.__init__ passes None as Resolver
+invalid-type-form = "warn"         # lowercase `callable`, `iter` as type, `...` as annotation
+missing-argument = "warn"          # wrong _backing_type: type[obj] (should be obj) in enum/flags
+too-many-positional-arguments = "warn"  # array.__setitem__ calls set() with wrong arity
+
+# -- Intentional design patterns --
+invalid-method-override = "warn"   # deliberate param narrowing in _set/set overrides (LSP)
+invalid-assignment = "warn"        # _backing_type instance vs type confusion; descriptor __set__
+unsupported-operator = "warn"      # obj.get() returns `object`, operators on result untypeable
+call-non-callable = "warn"         # dynamic inflater dispatch: resolved_type(resolver)
+not-subscriptable = "warn"         # object.__setattr__ hides dict types from checker
+no-matching-overload = "warn"      # untyped dict in struct_parser
+invalid-yield = "warn"             # yield from dynamic __getitem__ typed as object
+
 [tool.ruff]
 line-length = 120
 indent-width = 4