diff --git a/src/smbclient/_os.py b/src/smbclient/_os.py
index 88917c6..339a642 100644
--- a/src/smbclient/_os.py
+++ b/src/smbclient/_os.py
@@ -306,17 +306,208 @@ def makedirs(path, exist_ok=False, **kwargs):
             create_queue.pop(-1)
 
 
+# Taken from stdlib typeshed but removed the unused 'U' flag
+OpenTextModeUpdating: t.TypeAlias = t.Literal[
+    "r+",
+    "+r",
+    "rt+",
+    "r+t",
+    "+rt",
+    "tr+",
+    "t+r",
+    "+tr",
+    "w+",
+    "+w",
+    "wt+",
+    "w+t",
+    "+wt",
+    "tw+",
+    "t+w",
+    "+tw",
+    "a+",
+    "+a",
+    "at+",
+    "a+t",
+    "+at",
+    "ta+",
+    "t+a",
+    "+ta",
+    "x+",
+    "+x",
+    "xt+",
+    "x+t",
+    "+xt",
+    "tx+",
+    "t+x",
+    "+tx",
+]
+OpenTextModeWriting: t.TypeAlias = t.Literal["w", "wt", "tw", "a", "at", "ta", "x", "xt", "tx"]
+OpenTextModeReading: t.TypeAlias = t.Literal["r", "rt", "tr"]
+OpenTextMode: t.TypeAlias = OpenTextModeUpdating | OpenTextModeWriting | OpenTextModeReading
+OpenBinaryModeUpdating: t.TypeAlias = t.Literal[
+    "rb+",
+    "r+b",
+    "+rb",
+    "br+",
+    "b+r",
+    "+br",
+    "wb+",
+    "w+b",
+    "+wb",
+    "bw+",
+    "b+w",
+    "+bw",
+    "ab+",
+    "a+b",
+    "+ab",
+    "ba+",
+    "b+a",
+    "+ba",
+    "xb+",
+    "x+b",
+    "+xb",
+    "bx+",
+    "b+x",
+    "+bx",
+]
+OpenBinaryModeWriting: t.TypeAlias = t.Literal["wb", "bw", "ab", "ba", "xb", "bx"]
+OpenBinaryModeReading: t.TypeAlias = t.Literal["rb", "br"]
+OpenBinaryMode: t.TypeAlias = OpenBinaryModeUpdating | OpenBinaryModeReading | OpenBinaryModeWriting
+FileType: t.TypeAlias = t.Literal["file", "dir", "pipe"]
+
+
+class SMBBufferedRandom(io.BufferedRandom):
+    raw: SMBRawIO  # type: ignore
+
+
+class SMBBufferedReader(io.BufferedReader):
+    raw: SMBRawIO  # type: ignore
+
+
+class SMBBufferedWriter(io.BufferedWriter):
+    raw: SMBRawIO  # type: ignore
+
+
+# Text mode: always returns a TextIOWrapper
+@t.overload
+def open_file(
+    path,
+    mode: OpenTextMode = "r",
+    buffering=-1,
+    file_type: FileType = "file",
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> io.TextIOWrapper[SMBBufferedRandom | SMBBufferedReader | SMBBufferedWriter]: ...
+
+
+# Unbuffered binary mode: returns a File/Directory/Pipe IO object
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryMode,
+    buffering: t.Literal[0],
+    file_type: t.Literal["file"] = "file",
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBFileIO: ...
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryMode,
+    buffering: t.Literal[0],
+    file_type: t.Literal["dir"],
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBDirectoryIO: ...
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryMode,
+    buffering: t.Literal[0],
+    file_type: t.Literal["pipe"],
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBPipeIO: ...
+
+
+# Buffering is on: return BufferedRandom, BufferedReader, or BufferedWriter
+# NOTE: This cannot handle explicit buffer sizes (>0) because of limitations
+# in Python's type system
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryModeUpdating,
+    buffering: t.Literal[-1] = -1,
+    file_type: FileType = "file",
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBBufferedRandom: ...
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryModeReading,
+    buffering: t.Literal[-1] = -1,
+    file_type: FileType = "file",
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBBufferedReader: ...
+@t.overload
+def open_file(
+    path,
+    mode: OpenBinaryModeWriting,
+    buffering: t.Literal[-1] = -1,
+    file_type: FileType = "file",
+    encoding=None,
+    errors=None,
+    newline=None,
+    share_access=None,
+    desired_access=None,
+    file_attributes=None,
+    **kwargs,
+) -> SMBBufferedWriter: ...
+
+
 def open_file(
     path,
     mode="r",
     buffering=-1,
+    file_type: t.Literal["file", "dir", "pipe"] = "file",
     encoding=None,
     errors=None,
     newline=None,
     share_access=None,
     desired_access=None,
     file_attributes=None,
-    file_type="file",
     **kwargs,
 ):
     """
diff --git a/src/smbprotocol/open.py b/src/smbprotocol/open.py
index 14467d4..644457a 100644
--- a/src/smbprotocol/open.py
+++ b/src/smbprotocol/open.py
@@ -31,6 +31,7 @@
     Structure,
     StructureField,
 )
+from smbprotocol.tree import TreeConnect
 
 log = logging.getLogger(__name__)
 
@@ -1008,7 +1009,7 @@ def __init__(self):
 
 
 class Open:
-    def __init__(self, tree, name):
+    def __init__(self, tree: TreeConnect, name: str):
         """
         [MS-SMB2] v53.0 2017-09-15
 
diff --git a/src/smbprotocol/session.py b/src/smbprotocol/session.py
index ac99a02..5b59183 100644
--- a/src/smbprotocol/session.py
+++ b/src/smbprotocol/session.py
@@ -5,6 +5,7 @@
 import logging
 import random
 from collections import OrderedDict
+from typing import Literal, Optional
 
 import spnego
 from cryptography.hazmat.backends import default_backend
@@ -12,7 +13,7 @@
 from cryptography.hazmat.primitives.kdf.kbkdf import KBKDFHMAC, CounterLocation, Mode
 
 from smbprotocol import Dialects
-from smbprotocol.connection import Capabilities, Ciphers, SecurityMode
+from smbprotocol.connection import Capabilities, Ciphers, Connection, SecurityMode
 from smbprotocol.exceptions import (
     MoreProcessingRequired,
     SMBAuthenticationError,
@@ -170,7 +171,14 @@ def __init__(self):
 
 
 class Session:
-    def __init__(self, connection, username=None, password=None, require_encryption=True, auth_protocol="negotiate"):
+    def __init__(
+        self,
+        connection: Connection,
+        username: Optional[str] = None,
+        password: Optional[str] = None,
+        require_encryption=True,
+        auth_protocol: Literal["negotiate", "ntlm", "kerberos"] = "negotiate",
+    ):
         """
         [MS-SMB2] v53.0 2017-09-15
 
diff --git a/src/smbprotocol/tree.py b/src/smbprotocol/tree.py
index 7383aeb..3383c20 100644
--- a/src/smbprotocol/tree.py
+++ b/src/smbprotocol/tree.py
@@ -20,6 +20,7 @@
     SMB2ValidateNegotiateInfoRequest,
     SMB2ValidateNegotiateInfoResponse,
 )
+from smbprotocol.session import Session
 from smbprotocol.structure import BytesField, EnumField, FlagField, IntField, Structure
 
 log = logging.getLogger(__name__)
@@ -204,7 +205,7 @@ def __init__(self):
 
 
 class TreeConnect:
-    def __init__(self, session, share_name):
+    def __init__(self, session: Session, share_name: str):
         """
         [MS-SMB2] v53.0 2017-09-15