diff --git a/python/src/trezorlib/cli/__init__.py b/python/src/trezorlib/cli/__init__.py
index da2a126eba..0b14778ed7 100644
--- a/python/src/trezorlib/cli/__init__.py
+++ b/python/src/trezorlib/cli/__init__.py
@@ -26,7 +26,7 @@ from contextlib import contextmanager
 import click
 
 from .. import exceptions, transport, ui
-from ..client import PROTOCOL_V2, TrezorClient
+from ..client import ProtocolVersion, TrezorClient
 from ..messages import Capability
 from ..transport import Transport
 from ..transport.session import Session, SessionV1, SessionV2
@@ -150,11 +150,11 @@ class TrezorConnection:
 
         # Try resume session from id
         if self.session_id is not None:
-            if client.protocol_version is Session.CODEC_V1:
+            if client.protocol_version is ProtocolVersion.PROTOCOL_V1:
                 session = SessionV1.resume_from_id(
                     client=client, session_id=self.session_id
                 )
-            elif client.protocol_version is Session.THP_V2:
+            elif client.protocol_version is ProtocolVersion.PROTOCOL_V2:
                 session = SessionV2(client, self.session_id)
                 # TODO fix resumption on THP
             else:
@@ -311,7 +311,7 @@ def with_client(
             try:
                 return func(client, *args, **kwargs)
             finally:
-                if client.protocol_version == PROTOCOL_V2:
+                if client.protocol_version == ProtocolVersion.PROTOCOL_V2:
                     get_channel_db().save_channel(client.protocol)
                 # if not session_was_resumed:
                 #     try:
diff --git a/python/src/trezorlib/cli/trezorctl.py b/python/src/trezorlib/cli/trezorctl.py
index da784a5a6b..b3a885e4c8 100755
--- a/python/src/trezorlib/cli/trezorctl.py
+++ b/python/src/trezorlib/cli/trezorctl.py
@@ -25,7 +25,7 @@ from typing import TYPE_CHECKING, Any, Callable, Iterable, Optional, TypeVar, ca
 import click
 
 from .. import __version__, log, messages, protobuf
-from ..client import TrezorClient
+from ..client import ProtocolVersion, TrezorClient
 from ..transport import DeviceIsBusy, enumerate_devices
 from ..transport.session import Session
 from ..transport.thp import channel_database
@@ -308,7 +308,7 @@ def list_devices(no_resolve: bool) -> Optional[Iterable["Transport"]]:
         try:
             client = get_client(transport)
             description = format_device_name(client.features)
-            if client.protocol_version == Session.THP_V2:
+            if client.protocol_version == ProtocolVersion.PROTOCOL_V2:
                 get_channel_db().save_channel(client.protocol)
         except DeviceIsBusy:
             description = "Device is in use by another process"
diff --git a/python/src/trezorlib/client.py b/python/src/trezorlib/client.py
index 6bb8a2a27d..d82554dd93 100644
--- a/python/src/trezorlib/client.py
+++ b/python/src/trezorlib/client.py
@@ -18,6 +18,7 @@ from __future__ import annotations
 import logging
 import os
 import typing as t
+from enum import IntEnum
 
 from . import mapping, messages, models
 from .mapping import ProtobufMapping
@@ -48,9 +49,11 @@ Or visit https://suite.trezor.io/
 
 LOG = logging.getLogger(__name__)
 
-UNKNOWN = -1
-PROTOCOL_V1 = 1
-PROTOCOL_V2 = 2
+
+class ProtocolVersion(IntEnum):
+    UNKNOWN = 0x00
+    PROTOCOL_V1 = 0x01  # Codec
+    PROTOCOL_V2 = 0x02  # THP
 
 
 class TrezorClient:
@@ -80,12 +83,13 @@ class TrezorClient:
         else:
             self.protocol = protocol
         self.protocol.mapping = self.mapping
+
         if isinstance(self.protocol, ProtocolV1):
-            self._protocol_version = PROTOCOL_V1
+            self._protocol_version = ProtocolVersion.PROTOCOL_V1
         elif isinstance(self.protocol, ProtocolV2):
-            self._protocol_version = PROTOCOL_V2
+            self._protocol_version = ProtocolVersion.PROTOCOL_V2
         else:
-            self._protocol_version = UNKNOWN
+            self._protocol_version = ProtocolVersion.UNKNOWN
 
     @classmethod
     def resume(
diff --git a/python/src/trezorlib/debuglink.py b/python/src/trezorlib/debuglink.py
index ba24b8109a..707401cf1b 100644
--- a/python/src/trezorlib/debuglink.py
+++ b/python/src/trezorlib/debuglink.py
@@ -42,7 +42,7 @@ from .exceptions import Cancelled, PinException, TrezorFailure
 from .log import DUMP_BYTES
 from .messages import Capability, DebugWaitType
 from .tools import expect, parse_path
-from .transport.session import Session, SessionV1, SessionV2
+from .transport.session import Session, SessionV1
 from .transport.thp.protocol_v1 import ProtocolV1
 
 if t.TYPE_CHECKING:
@@ -1031,18 +1031,12 @@ class SessionDebugWrapper(Session):
     def __init__(self, session: Session) -> None:
         self._session = session
         self.reset_debug_features()
-        if isinstance(session, SessionV1):
-            self.client.session_version = 1
-        elif isinstance(session, SessionV2):
-            self.client.session_version = 2
-        elif isinstance(session, SessionDebugWrapper):
+        if isinstance(session, SessionDebugWrapper):
             raise Exception("Cannot wrap already wrapped session!")
-        else:
-            self.client.session_version = -1  # UNKNOWN
 
     @property
-    def session_version(self) -> int:
-        return self.client.session_version
+    def protocol_version(self) -> int:
+        return self.client.protocol_version
 
     @property
     def client(self) -> TrezorClientDebugLink:
@@ -1284,7 +1278,6 @@ class TrezorClientDebugLink(TrezorClient):
     # by the device.
 
     def __init__(self, transport: "Transport", auto_interact: bool = True) -> None:
-        self._session_version: int = -1
         try:
             debug_transport = transport.find_debug()
             self.debug = DebugLink(debug_transport, auto_interact)
@@ -1311,14 +1304,6 @@ class TrezorClientDebugLink(TrezorClient):
         self.debug.version = self.version
         self.passphrase: str | None = None
 
-    @property
-    def session_version(self) -> int:
-        return self._session_version
-
-    @session_version.setter
-    def session_version(self, value: int) -> None:
-        self._session_version = value
-
     @property
     def layout_type(self) -> LayoutType:
         return self.debug.layout_type
diff --git a/python/src/trezorlib/transport/session.py b/python/src/trezorlib/transport/session.py
index 1d0948ddf5..6b6f4cce2c 100644
--- a/python/src/trezorlib/transport/session.py
+++ b/python/src/trezorlib/transport/session.py
@@ -14,8 +14,6 @@ LOG = logging.getLogger(__name__)
 
 
 class Session:
-    CODEC_V1: t.Final[int] = 1
-    THP_V2: t.Final[int] = 2
     button_callback: t.Callable[[Session, t.Any], t.Any] | None = None
     pin_callback: t.Callable[[Session, t.Any], t.Any] | None = None
     passphrase_callback: t.Callable[[Session, t.Any], t.Any] | None = None
diff --git a/tests/device_tests/test_basic.py b/tests/device_tests/test_basic.py
index 50dee4a42e..2955615e11 100644
--- a/tests/device_tests/test_basic.py
+++ b/tests/device_tests/test_basic.py
@@ -15,6 +15,7 @@
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
 from trezorlib import device, messages, models
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.debuglink import TrezorClientDebugLink as Client
 
@@ -22,7 +23,7 @@ from trezorlib.debuglink import TrezorClientDebugLink as Client
 def test_features(client: Client):
     session = client.get_session()
     f0 = session.features
-    if Session(session).session_version == Session.CODEC_V1:
+    if client.protocol_version == ProtocolVersion.PROTOCOL_V1:
         # session erases session_id from its features
         f0.session_id = session.id
         f1 = session.call(messages.Initialize(session_id=session.id))
diff --git a/tests/device_tests/test_debuglink.py b/tests/device_tests/test_debuglink.py
index 7516da8a5d..d9445fddec 100644
--- a/tests/device_tests/test_debuglink.py
+++ b/tests/device_tests/test_debuglink.py
@@ -17,6 +17,7 @@
 import pytest
 
 from trezorlib import debuglink, device, messages, misc
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.debuglink import TrezorClientDebugLink as Client
 from trezorlib.tools import parse_path
@@ -62,7 +63,7 @@ def test_pin(session: Session):
 
 @pytest.mark.models("core")
 def test_softlock_instability(session: Session):
-    if session.session_version == Session.THP_V2:
+    if session.protocol_version == ProtocolVersion.PROTOCOL_V2:
         raise Exception("THIS NEEDS TO BE CHANGED FOR THP")
 
     def load_device():
diff --git a/tests/device_tests/test_msg_applysettings.py b/tests/device_tests/test_msg_applysettings.py
index 6179acb82f..18fde33506 100644
--- a/tests/device_tests/test_msg_applysettings.py
+++ b/tests/device_tests/test_msg_applysettings.py
@@ -19,6 +19,7 @@ from pathlib import Path
 import pytest
 
 from trezorlib import btc, device, exceptions, messages, misc, models
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.tools import parse_path
 
@@ -205,7 +206,7 @@ def test_apply_homescreen_toif(session: Session):
 
 @pytest.mark.models(skip=["legacy", "safe3"])
 def test_apply_homescreen_jpeg(session: Session):
-    if session.session_version is Session.THP_V2:
+    if session.protocol_version is ProtocolVersion.PROTOCOL_V2:
         raise Exception(
             "FAILS BECAUSE THE MESSAGE IS BIGGER THAN THE INTERNAL READ BUFFER"
         )
diff --git a/tests/device_tests/test_protection_levels.py b/tests/device_tests/test_protection_levels.py
index 1f49657e35..7825cbacee 100644
--- a/tests/device_tests/test_protection_levels.py
+++ b/tests/device_tests/test_protection_levels.py
@@ -17,6 +17,7 @@
 import pytest
 
 from trezorlib import btc, device, messages, misc, models
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import LayoutType
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.exceptions import TrezorFailure
@@ -61,17 +62,17 @@ def _assert_protection(
         client.refresh_features()
         assert client.features.pin_protection is pin
         assert client.features.passphrase_protection is passphrase
-        if session.session_version == Session.THP_V2:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V2:
             new_session = session.client.get_session()
         session.lock()
         session.end()
-    if session.session_version == Session.CODEC_V1:
+    if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
         new_session = session.client.get_session()
     return Session(new_session)
 
 
 def test_initialize(session: Session):
-    if session.session_version == Session.THP_V2:
+    if session.protocol_version == ProtocolVersion.PROTOCOL_V2:
         # Test is skipped for THP
         return
 
@@ -194,7 +195,7 @@ def test_get_public_key(session: Session):
         client.use_pin_sequence([PIN4])
         expected_responses = [_pin_request(session)]
 
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             expected_responses.append(messages.PassphraseRequest)
         expected_responses.append(messages.PublicKey)
 
@@ -208,7 +209,7 @@ def test_get_address(session: Session):
     with session, session.client as client:
         client.use_pin_sequence([PIN4])
         expected_responses = [_pin_request(session)]
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             expected_responses.append(messages.PassphraseRequest)
         expected_responses.append(messages.Address)
 
@@ -323,7 +324,7 @@ def test_sign_message(session: Session):
 
         expected_responses = [_pin_request(session)]
 
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             expected_responses.append(messages.PassphraseRequest)
 
         expected_responses.extend(
@@ -409,7 +410,7 @@ def test_signtx(session: Session):
     with session, session.client as client:
         client.use_pin_sequence([PIN4])
         expected_responses = [_pin_request(session)]
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             expected_responses.append(messages.PassphraseRequest)
         expected_responses.extend(
             [
@@ -463,11 +464,11 @@ def test_unlocked(session: Session):
 def test_passphrase_cached(session: Session):
     session = _assert_protection(session, pin=False)
     with session:
-        if session.session_version == 1:
+        if session.protocol_version == 1:
             session.set_expected_responses(
                 [messages.PassphraseRequest, messages.Address]
             )
-        elif session.session_version == 2:
+        elif session.protocol_version == 2:
             session.set_expected_responses([messages.Address])
         else:
             raise Exception("Unknown session type")
diff --git a/tests/device_tests/test_session.py b/tests/device_tests/test_session.py
index 45cec6acf2..56b8ace996 100644
--- a/tests/device_tests/test_session.py
+++ b/tests/device_tests/test_session.py
@@ -18,6 +18,7 @@ import pytest
 
 from trezorlib import cardano, messages, models
 from trezorlib.btc import get_public_node
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.debuglink import TrezorClientDebugLink as Client
 from trezorlib.exceptions import TrezorFailure
@@ -33,7 +34,7 @@ PIN4 = "1234"
 
 def test_thp_end_session(client: Client):
     session = Session(client.get_session())
-    if session.session_version == Session.CODEC_V1:
+    if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
         # TODO: This test should be skipped on non-THP builds
         return
 
diff --git a/tests/device_tests/test_session_id_and_passphrase.py b/tests/device_tests/test_session_id_and_passphrase.py
index 9dc059e978..6aa7dced5b 100644
--- a/tests/device_tests/test_session_id_and_passphrase.py
+++ b/tests/device_tests/test_session_id_and_passphrase.py
@@ -19,6 +19,7 @@ import random
 import pytest
 
 from trezorlib import device, exceptions, messages
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import LayoutType
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.debuglink import TrezorClientDebugLink as Client
@@ -65,7 +66,10 @@ def _get_xpub(
         ]
     else:
         expected_responses = [messages.PublicKey]
-    if passphrase_v1 is not None and session.session_version == Session.CODEC_V1:
+    if (
+        passphrase_v1 is not None
+        and session.protocol_version == ProtocolVersion.PROTOCOL_V1
+    ):
         session.passphrase = passphrase_v1
 
     with session:
diff --git a/tests/persistence_tests/test_shamir_persistence.py b/tests/persistence_tests/test_shamir_persistence.py
index a545ee556c..1524bd5203 100644
--- a/tests/persistence_tests/test_shamir_persistence.py
+++ b/tests/persistence_tests/test_shamir_persistence.py
@@ -17,8 +17,8 @@
 import pytest
 
 from trezorlib import device, messages
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import DebugLink, LayoutType
-from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.messages import RecoveryStatus
 
 from ..click_tests import common, recovery
@@ -158,7 +158,7 @@ def test_recovery_on_old_wallet(core_emulator: Emulator):
     layout = debug.read_layout()
 
     # while keyboard is open, hit the device with Initialize/GetFeatures
-    if device_handler.client.session_version == Session.CODEC_V1:
+    if device_handler.client.protocol_version == ProtocolVersion.PROTOCOL_V1:
         device_handler.client.get_management_session().call(messages.Initialize())
     device_handler.client.refresh_features()
 
diff --git a/tests/upgrade_tests/test_firmware_upgrades.py b/tests/upgrade_tests/test_firmware_upgrades.py
index 2531fd450d..94682a9b19 100644
--- a/tests/upgrade_tests/test_firmware_upgrades.py
+++ b/tests/upgrade_tests/test_firmware_upgrades.py
@@ -21,6 +21,7 @@ import pytest
 from shamir_mnemonic import shamir
 
 from trezorlib import btc, debuglink, device, exceptions, fido, messages, models
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.messages import (
     ApplySettings,
@@ -373,7 +374,7 @@ def test_upgrade_shamir_backup(gen: str, tag: Optional[str]):
 
         # Get a passphrase-less and a passphrased address.
         address = btc.get_address(session, "Bitcoin", PATH)
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             session.call(messages.Initialize(new_session=True))
         new_session = emu.client.get_session(passphrase="TREZOR")
         address_passphrase = btc.get_address(new_session, "Bitcoin", PATH)
diff --git a/tests/upgrade_tests/test_passphrase_consistency.py b/tests/upgrade_tests/test_passphrase_consistency.py
index be8c7dc74b..bdeb74cabf 100644
--- a/tests/upgrade_tests/test_passphrase_consistency.py
+++ b/tests/upgrade_tests/test_passphrase_consistency.py
@@ -20,6 +20,7 @@ import pytest
 
 from trezorlib import btc, device, mapping, messages, models, protobuf
 from trezorlib._internal.emulator import Emulator
+from trezorlib.client import ProtocolVersion
 from trezorlib.debuglink import SessionDebugWrapper as Session
 from trezorlib.tools import parse_path
 
@@ -139,7 +140,7 @@ def test_init_device(emulator: Emulator):
         btc.get_address(session, "Testnet", parse_path("44h/1h/0h/0/0"))
         # in TT < 2.3.0 session_id will only be available after PassphraseStateRequest
         session_id = session.id
-        if session.session_version == Session.CODEC_V1:
+        if session.protocol_version == ProtocolVersion.PROTOCOL_V1:
             session.call(messages.Initialize(session_id=session_id))
         btc.get_address(
             session,