diff --git a/matrix_appservice_kakaotalk/commands/__init__.py b/matrix_appservice_kakaotalk/commands/__init__.py
index f92dfd5..d0a7f6f 100644
--- a/matrix_appservice_kakaotalk/commands/__init__.py
+++ b/matrix_appservice_kakaotalk/commands/__init__.py
@@ -1,3 +1,18 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from .auth import SECTION_AUTH
 from .conn import SECTION_CONNECTION
 from .kakaotalk import SECTION_FRIENDS
diff --git a/matrix_appservice_kakaotalk/commands/conn.py b/matrix_appservice_kakaotalk/commands/conn.py
index 42eb58b..8af0b99 100644
--- a/matrix_appservice_kakaotalk/commands/conn.py
+++ b/matrix_appservice_kakaotalk/commands/conn.py
@@ -60,16 +60,19 @@ async def whoami(evt: CommandEvent) -> None:
     await evt.mark_read()
     try:
         own_info = await evt.sender.get_own_info()
+    except SerializerError:
+        evt.sender.log.exception("Failed to deserialize settings struct")
+        own_info = None
+    except CommandException as e:
+        await evt.reply(f"Error from KakaoTalk: {e}")
+    if own_info:
         await evt.reply(
             f"You're logged in as `{own_info.more.uuid}` (nickname: {own_info.more.nickName}, user ID: {evt.sender.ktid})."
         )
-    except SerializerError:
-        evt.sender.log.exception("Failed to deserialize settings struct")
+    else:
         await evt.reply(
             f"You're logged in, but the bridge is unable to retrieve your profile information (user ID: {evt.sender.ktid})."
         )
-    except CommandException as e:
-        await evt.reply(f"Error from KakaoTalk: {e}")
 
 
 @command_handler(
diff --git a/matrix_appservice_kakaotalk/commands/typehint.py b/matrix_appservice_kakaotalk/commands/typehint.py
index 9833394..e04e840 100644
--- a/matrix_appservice_kakaotalk/commands/typehint.py
+++ b/matrix_appservice_kakaotalk/commands/typehint.py
@@ -1,12 +1,31 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from __future__ import annotations
+
 from typing import TYPE_CHECKING
 
 from mautrix.bridge.commands import CommandEvent as BaseCommandEvent
 
 if TYPE_CHECKING:
     from ..__main__ import KakaoTalkBridge
+    from ..portal import Portal
     from ..user import User
 
 
 class CommandEvent(BaseCommandEvent):
-    bridge: "KakaoTalkBridge"
-    sender: "User"
+    bridge: KakaoTalkBridge
+    portal: Portal
+    sender: User
diff --git a/matrix_appservice_kakaotalk/db/__init__.py b/matrix_appservice_kakaotalk/db/__init__.py
index 22a68f4..3dc2b44 100644
--- a/matrix_appservice_kakaotalk/db/__init__.py
+++ b/matrix_appservice_kakaotalk/db/__init__.py
@@ -1,3 +1,18 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from mautrix.util.async_db import Database
 
 from .message import Message
diff --git a/matrix_appservice_kakaotalk/db/message.py b/matrix_appservice_kakaotalk/db/message.py
index 1010565..893d9c0 100644
--- a/matrix_appservice_kakaotalk/db/message.py
+++ b/matrix_appservice_kakaotalk/db/message.py
@@ -23,7 +23,7 @@ from attr import dataclass, field
 from mautrix.types import EventID, RoomID
 from mautrix.util.async_db import Database, Scheme
 
-from ..kt.types.bson import Long
+from ..kt.types.bson import Long, to_optional_long
 
 fake_db = Database.create("") if TYPE_CHECKING else None
 
@@ -34,7 +34,7 @@ class Message:
 
     mxid: EventID
     mx_room: RoomID
-    ktid: Long | None = field(converter=lambda ktid: Long(ktid) if ktid is not None else None)
+    ktid: Long | None = field(converter=to_optional_long)
     index: int
     kt_chat: Long = field(converter=Long)
     kt_receiver: Long = field(converter=Long)
diff --git a/matrix_appservice_kakaotalk/db/upgrade/__init__.py b/matrix_appservice_kakaotalk/db/upgrade/__init__.py
index 2079708..af7dd17 100644
--- a/matrix_appservice_kakaotalk/db/upgrade/__init__.py
+++ b/matrix_appservice_kakaotalk/db/upgrade/__init__.py
@@ -1,3 +1,18 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from mautrix.util.async_db import UpgradeTable
 
 upgrade_table = UpgradeTable()
diff --git a/matrix_appservice_kakaotalk/db/user.py b/matrix_appservice_kakaotalk/db/user.py
index 476e186..7dee70e 100644
--- a/matrix_appservice_kakaotalk/db/user.py
+++ b/matrix_appservice_kakaotalk/db/user.py
@@ -23,7 +23,7 @@ from attr import dataclass, field
 from mautrix.types import RoomID, UserID
 from mautrix.util.async_db import Database
 
-from ..kt.types.bson import Long
+from ..kt.types.bson import Long, to_optional_long
 
 fake_db = Database.create("") if TYPE_CHECKING else None
 
@@ -33,7 +33,7 @@ class User:
     db: ClassVar[Database] = fake_db
 
     mxid: UserID
-    ktid: Long | None = field(converter=lambda x: Long(x) if x is not None else None)
+    ktid: Long | None = field(converter=to_optional_long)
     uuid: str | None
     access_token: str | None
     refresh_token: str | None
diff --git a/matrix_appservice_kakaotalk/formatter/__init__.py b/matrix_appservice_kakaotalk/formatter/__init__.py
index da0da8e..30c0ee7 100644
--- a/matrix_appservice_kakaotalk/formatter/__init__.py
+++ b/matrix_appservice_kakaotalk/formatter/__init__.py
@@ -1,2 +1,17 @@
+# matrix-appservice-kakaotalk - A Matrix-KakaoTalk puppeting bridge.
+# Copyright (C) 2022 Tulir Asokan, Andrew Ferrazzutti
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from .from_kakaotalk import kakaotalk_to_matrix
 from .from_matrix import matrix_to_kakaotalk
diff --git a/matrix_appservice_kakaotalk/formatter/from_matrix.py b/matrix_appservice_kakaotalk/formatter/from_matrix.py
index 3588cab..9976ea6 100644
--- a/matrix_appservice_kakaotalk/formatter/from_matrix.py
+++ b/matrix_appservice_kakaotalk/formatter/from_matrix.py
@@ -111,7 +111,7 @@ async def matrix_to_kakaotalk(
     # NOTE By design, this *throws* if user intent can't be matched (i.e. if a reply can't be created)
     if content.relates_to.rel_type == RelationType.REPLY and not skip_reply:
         message = await DBMessage.get_by_mxid(content.relates_to.event_id, room_id)
-        if not message:
+        if not message or not message.ktid:
             raise ValueError(
                 f"Couldn't find reply target {content.relates_to.event_id}"
                 " to bridge text message reply metadata to KakaoTalk"
@@ -167,17 +167,17 @@ async def matrix_to_kakaotalk(
                 mxid = mention.extra_info["user_id"]
                 if mxid not in joined_members:
                     continue
-                ktid = await _get_id_from_mxid(mxid)
+                ktid = await _get_id_from_mxid(mxid, portal)
                 if ktid is None:
                     continue
                 at += text[last_offset:mention.offset+1].count("@")
                 last_offset = mention.offset+1
-                mention = mentions_by_user.setdefault(ktid, MentionStruct(
+                mention_by_user = mentions_by_user.setdefault(ktid, MentionStruct(
                     at=[],
                     len=mention.length,
                     user_id=ktid,
                 ))
-                mention.at.append(at)
+                mention_by_user.at.append(at)
         mentions = list(mentions_by_user.values()) if mentions_by_user else None
     else:
         text = content.body
diff --git a/matrix_appservice_kakaotalk/kt/client/client.py b/matrix_appservice_kakaotalk/kt/client/client.py
index e0b4ff1..ff9ce1a 100644
--- a/matrix_appservice_kakaotalk/kt/client/client.py
+++ b/matrix_appservice_kakaotalk/kt/client/client.py
@@ -137,7 +137,7 @@ class Client:
         return cls._api_request_void("register_device", passcode=passcode, **req)
 
     @classmethod
-    async def login(cls, **req: JSON) -> Awaitable[OAuthCredential]:
+    def login(cls, **req: JSON) -> Awaitable[OAuthCredential]:
         """
         Obtain a session token by logging in with user-provided credentials.
         Must have first called register_device with these credentials.
@@ -493,7 +493,7 @@ class Client:
     async def _api_user_cred_request_void(self, command: str, *, renew: bool = True, **data: JSON) -> None:
         while True:
             try:
-                return await self._api_user_request_result(
+                await self._api_user_request_void(
                     command, oauth_credential=self._oauth_credential, renew=False, **data
                 )
             except InvalidAccessToken:
@@ -599,7 +599,7 @@ class Client:
             res = None
         return self._on_disconnect(res)
 
-    def _on_switch_server(self) -> Awaitable[None]:
+    def _on_switch_server(self, _: dict[str, JSON]) -> Awaitable[None]:
         # TODO Reconnect automatically instead
         return self._on_disconnect(KickoutRes(KnownKickoutType.CHANGE_SERVER))
 
diff --git a/matrix_appservice_kakaotalk/kt/client/errors.py b/matrix_appservice_kakaotalk/kt/client/errors.py
index 5acebbf..426f7fd 100644
--- a/matrix_appservice_kakaotalk/kt/client/errors.py
+++ b/matrix_appservice_kakaotalk/kt/client/errors.py
@@ -70,7 +70,7 @@ class ResponseError(Exception):
     pass
 
 
-_status_code_message_map: dict[KnownAuthStatusCode | KnownDataStatusCode | int] = {
+_status_code_message_map: dict[KnownAuthStatusCode | KnownDataStatusCode | int, str] = {
     KnownAuthStatusCode.INVALID_PHONE_NUMBER: "Invalid phone number",
     KnownAuthStatusCode.SUCCESS_WITH_ACCOUNT: "Success",
     KnownAuthStatusCode.SUCCESS_WITH_DEVICE_CHANGED: "Success (device changed)",
diff --git a/matrix_appservice_kakaotalk/kt/types/api/struct/account.py b/matrix_appservice_kakaotalk/kt/types/api/struct/account.py
index 3e879e0..53ef528 100644
--- a/matrix_appservice_kakaotalk/kt/types/api/struct/account.py
+++ b/matrix_appservice_kakaotalk/kt/types/api/struct/account.py
@@ -26,9 +26,9 @@ from ...bson import Long
 class OpenChatSettingsStruct(SerializableAttrs):
     chatMemberMaxJoin: int
     chatRoomMaxJoin: int
-    createLinkLimit: 10;
-    createCardLinkLimit: 3;
-    numOfStaffLimit: 5;
+    createLinkLimit = 10
+    createCardLinkLimit = 3
+    numOfStaffLimit = 5
     rewritable: bool
     handoverEnabled: bool
 
diff --git a/matrix_appservice_kakaotalk/kt/types/bson.py b/matrix_appservice_kakaotalk/kt/types/bson.py
index 8456ad2..40fae9d 100644
--- a/matrix_appservice_kakaotalk/kt/types/bson.py
+++ b/matrix_appservice_kakaotalk/kt/types/bson.py
@@ -13,6 +13,8 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from typing import Any
+
 from mautrix.types import Serializable, JSON
 
 
@@ -23,3 +25,6 @@ class Long(int, Serializable):
     @classmethod
     def deserialize(cls, raw: JSON) -> "Long":
         return cls(raw)
+
+def to_optional_long(x: Any | None) -> Long | None:
+    return Long(x) if x is not None else None
diff --git a/matrix_appservice_kakaotalk/kt/types/packet/chat/kickout.py b/matrix_appservice_kakaotalk/kt/types/packet/chat/kickout.py
index 078eb41..9422d77 100644
--- a/matrix_appservice_kakaotalk/kt/types/packet/chat/kickout.py
+++ b/matrix_appservice_kakaotalk/kt/types/packet/chat/kickout.py
@@ -21,7 +21,6 @@ from attr import dataclass
 from mautrix.types import SerializableAttrs
 
 
-@dataclass
 class KnownKickoutType(IntEnum):
     CHANGE_SERVER = -2
     LOGIN_ANOTHER = 0
diff --git a/matrix_appservice_kakaotalk/portal.py b/matrix_appservice_kakaotalk/portal.py
index d66553b..075c562 100644
--- a/matrix_appservice_kakaotalk/portal.py
+++ b/matrix_appservice_kakaotalk/portal.py
@@ -21,8 +21,10 @@ from typing import (
     AsyncGenerator,
     Awaitable,
     Callable,
-    NamedTuple,
+    Coroutine,
+    Generic,
     Pattern,
+    TypeVar,
     cast,
 )
 from io import BytesIO
@@ -31,6 +33,8 @@ import asyncio
 import re
 import time
 
+from attr import dataclass
+
 from mautrix.appservice import IntentAPI
 from mautrix.bridge import BasePortal, NotificationDisabler, async_getter_lock
 from mautrix.errors import MatrixError, MForbidden, MNotFound, SessionNotFound
@@ -125,11 +129,15 @@ class FakeLock:
         pass
 
 
-class StateEventHandler(NamedTuple):
-    # TODO Can this use Generic to force the two StateEventContent parameters to be of the same type?
-    #      Or, just have a single StateEvent parameter
-    apply: Callable[[u.User, StateEventContent, StateEventContent], Awaitable[None]]
-    revert: Callable[[StateEventContent], Awaitable[None]]
+T = TypeVar("T")
+ACallable = Coroutine[None, None, T]
+
+StateEventHandlerContentType = TypeVar("StateEventHandlerContentType", bound=StateEventContent)
+
+@dataclass
+class StateEventHandler(Generic[StateEventHandlerContentType]):
+    apply: Callable[[Portal, u.User, StateEventHandlerContentType, StateEventHandlerContentType], ACallable[None]]
+    revert: Callable[[Portal, StateEventHandlerContentType], ACallable[None]]
     action_name: str
 
 
@@ -155,6 +163,9 @@ class Portal(DBPortal, BasePortal):
     _scheduled_resync: asyncio.Task | None
     _resync_targets: dict[int, p.Puppet]
 
+    _CHAT_TYPE_HANDLER_MAP: dict[ChatType, Callable[..., ACallable[list[EventID]]]]
+    _STATE_EVENT_HANDLER_MAP: dict[EventType, StateEventHandler]
+
     def __init__(
         self,
         ktid: Long,
@@ -226,7 +237,7 @@ class Portal(DBPortal, BasePortal):
             16385: cls._handle_kakaotalk_deleted,
         }
 
-        cls._STATE_EVENT_HANDLER_MAP: dict[EventType, StateEventHandler] = {
+        cls._STATE_EVENT_HANDLER_MAP = {
             EventType.ROOM_POWER_LEVELS: StateEventHandler(
                 cls._handle_matrix_power_levels,
                 cls._revert_matrix_power_levels,
@@ -506,7 +517,7 @@ class Portal(DBPortal, BasePortal):
             decryption_info.url = url
         return url, info, decryption_info
 
-    async def _update_name(self, name: str) -> bool:
+    async def _update_name(self, name: str | None) -> bool:
         if not name:
             self.log.warning("Got empty name in _update_name call")
             return False
@@ -593,6 +604,8 @@ class Portal(DBPortal, BasePortal):
             return False
         if not puppet:
             puppet = await self.get_dm_puppet()
+            if not puppet:
+                return False
         changed = await self._update_name(puppet.name)
         changed = await self._update_photo_from_puppet(puppet) or changed
         return changed
@@ -815,15 +828,20 @@ class Portal(DBPortal, BasePortal):
 
     async def _create_matrix_room(
         self, source: u.User, info: PortalChannelInfo | None = None
-    ) -> RoomID | None:
+    ) -> RoomID:
         if self.mxid:
             await self._update_matrix_room(source, info)
             return self.mxid
 
         self.log.debug(f"Creating Matrix room")
+
         if self.is_direct:
             # NOTE Must do this to find the other member of the DM, since the channel ID != the member's ID!
+            if not info or not info.participantInfo:
+                info = await source.client.get_portal_channel_info(self.channel_props)
+                assert info.participantInfo
             await self._update_participants(source, info.participantInfo)
+
         name: str | None = None
         description: str | None = None
         initial_state = [
@@ -843,6 +861,9 @@ class Portal(DBPortal, BasePortal):
         if self.is_open:
             preset = RoomCreatePreset.PUBLIC
             # TODO Find whether perms apply to any non-direct channel, or just open ones
+            if not info or not info.participantInfo:
+                info = await source.client.get_portal_channel_info(self.channel_props)
+                assert info.participantInfo
             user_power_levels = await self._get_mapped_participant_power_levels(info.participantInfo.participants)
             # NOTE Giving the bot a +1 power level if necessary so it can demote non-puppet admins
             user_power_levels[self.main_intent.mxid] = max(100, 1 + FROM_PERM_MAP[OpenChannelUserPerm.OWNER])
@@ -924,6 +945,8 @@ class Portal(DBPortal, BasePortal):
                 await self._update_participants(source, info.participantInfo)
 
             try:
+                # TODO Think of better typing for this
+                assert info.channel_info
                 await self.backfill(source, is_initial=True, channel_info=info.channel_info)
             except Exception:
                 self.log.exception("Failed to backfill new portal")
@@ -1075,10 +1098,11 @@ class Portal(DBPortal, BasePortal):
         mimetype = message.info.mimetype or magic.mimetype(data)
         filename = message.body
         width, height = None, None
-        if message.info in (MessageType.IMAGE, MessageType.STICKER, MessageType.VIDEO):
+        if message.msgtype in (MessageType.IMAGE, MessageType.STICKER, MessageType.VIDEO):
             width = message.info.width
             height = message.info.height
         try:
+            ext = guess_extension(mimetype)
             log_id = await sender.client.send_media(
                 self.channel_props,
                 TO_MSGTYPE_MAP[message.msgtype],
@@ -1086,7 +1110,7 @@ class Portal(DBPortal, BasePortal):
                 filename,
                 width=width,
                 height=height,
-                ext=guess_extension(mimetype)[1:],
+                ext=ext[1:] if ext else "",
             )
         except CommandException as e:
             self.log.debug(f"Error uploading media for Matrix message {event_id}: {e!s}")
@@ -1191,7 +1215,8 @@ class Portal(DBPortal, BasePortal):
             return
         try:
             effective_sender, _ = await self.get_relay_sender(sender, f"{handler.action_name} {evt.event_id}")
-            await handler.apply(self, effective_sender, evt.prev_content, evt.content)
+            if effective_sender:
+                await handler.apply(self, effective_sender, evt.prev_content, evt.content)
         except Exception as e:
             self.log.error(
                 f"Failed to handle Matrix {handler.action_name} {evt.event_id}: {e}",
@@ -1314,7 +1339,7 @@ class Portal(DBPortal, BasePortal):
         await self.save()
 
     async def _revert_matrix_room_topic(self, prev_content: RoomTopicStateEventContent) -> None:
-        await self.main_intent.set_room_topic(self.mxid, prev_content.topic)
+        await self.main_intent.set_room_topic(self.mxid, prev_content.topic or "")
 
     async def _handle_matrix_room_avatar(
         self,
@@ -1479,7 +1504,7 @@ class Portal(DBPortal, BasePortal):
         chat_text: str | None,
         chat_type: ChatType,
         **_
-    ) -> Awaitable[list[EventID]]:
+    ) -> list[EventID]:
         try:
             type_str = KnownChatType(chat_type).name.lower()
         except ValueError:
@@ -1546,14 +1571,14 @@ class Portal(DBPortal, BasePortal):
         await self._add_kakaotalk_reply(content, attachment)
         return [await self._send_message(intent, content, timestamp=timestamp)]
 
-    def _handle_kakaotalk_photo(self, **kwargs) -> Awaitable[list[EventID]]:
-        return asyncio.gather(self._handle_kakaotalk_uniphoto(**kwargs))
+    async def _handle_kakaotalk_photo(self, **kwargs) -> list[EventID]:
+        return [await self._handle_kakaotalk_uniphoto(**kwargs)]
 
     async def _handle_kakaotalk_multiphoto(
         self,
         attachment: MultiPhotoAttachment,
         **kwargs
-    ) -> Awaitable[list[EventID]]:
+    ) -> list[EventID]:
         # TODO Upload media concurrently, but post messages sequentially
         return [
             await self._handle_kakaotalk_uniphoto(
@@ -1594,12 +1619,12 @@ class Portal(DBPortal, BasePortal):
             **kwargs
         )
 
-    def _handle_kakaotalk_video(
+    async def _handle_kakaotalk_video(
         self,
         attachment: VideoAttachment,
         **kwargs
-    ) -> Awaitable[list[EventID]]:
-        return asyncio.gather(self._handle_kakaotalk_media(
+    ) -> list[EventID]:
+        return [await self._handle_kakaotalk_media(
             attachment,
             VideoInfo(
                 duration=attachment.d,
@@ -1608,14 +1633,14 @@ class Portal(DBPortal, BasePortal):
             ),
             MessageType.VIDEO,
             **kwargs
-        ))
+        )]
 
-    def _handle_kakaotalk_audio(
+    async def _handle_kakaotalk_audio(
         self,
         attachment: AudioAttachment,
         **kwargs
-    ) -> Awaitable[list[EventID]]:
-        return asyncio.gather(self._handle_kakaotalk_media(
+    ) -> list[EventID]:
+        return [await self._handle_kakaotalk_media(
             attachment,
             AudioInfo(
                 size=attachment.s,
@@ -1623,11 +1648,11 @@ class Portal(DBPortal, BasePortal):
             ),
             MessageType.AUDIO,
             **kwargs
-        ))
+        )]
 
     async def _handle_kakaotalk_media(
         self,
-        attachment: MediaAttachment,
+        attachment: MediaAttachment | AudioAttachment,
         info: MediaInfo,
         msgtype: MessageType,
         *,
@@ -1648,7 +1673,7 @@ class Portal(DBPortal, BasePortal):
         info.size = additional_info.size
         info.mimetype = additional_info.mimetype
         content = MediaMessageEventContent(
-            url=mxc, file=decryption_info, msgtype=msgtype, body=chat_text, info=info
+            url=mxc, file=decryption_info, msgtype=msgtype, body=chat_text or "", info=info
         )
         return await self._send_message(intent, content, timestamp=timestamp)
 
@@ -1787,7 +1812,7 @@ class Portal(DBPortal, BasePortal):
         # TODO Should this be removed? With it, can't sync an empty portal!
         #elif (not most_recent or not most_recent.timestamp) and not is_initial:
         #    self.log.debug("Not backfilling %s: no most recent message found", self.ktid_log)
-        elif last_log_id and most_recent and int(most_recent.ktid) >= int(last_log_id):
+        elif last_log_id and most_recent and int(most_recent.ktid or 0) >= int(last_log_id):
             self.log.debug(
                 "Not backfilling %s: last activity is equal to most recent bridged "
                 "message (%s >= %s)",
diff --git a/matrix_appservice_kakaotalk/user.py b/matrix_appservice_kakaotalk/user.py
index 3d93d5a..fd0e01f 100644
--- a/matrix_appservice_kakaotalk/user.py
+++ b/matrix_appservice_kakaotalk/user.py
@@ -89,7 +89,7 @@ class User(DBUser, BaseUser):
     by_mxid: dict[UserID, User] = {}
     by_ktid: dict[int, User] = {}
 
-    client: Client | None
+    _client: Client | None
 
     _notice_room_lock: asyncio.Lock
     _notice_send_lock: asyncio.Lock
@@ -141,7 +141,7 @@ class User(DBUser, BaseUser):
         self._logged_in_info = None
         self._logged_in_info_time = 0
 
-        self.client = None
+        self._client = None
 
     @classmethod
     def init_cls(cls, bridge: KakaoTalkBridge) -> AsyncIterable[Awaitable[bool]]:
@@ -151,6 +151,12 @@ class User(DBUser, BaseUser):
         cls.temp_disconnect_notices = bridge.config["bridge.temporary_disconnect_notices"]
         return (user.reload_session(is_startup=True) async for user in cls.all_logged_in())
 
+    @property
+    def client(self) -> Client:
+        if not self._client:
+            raise ValueError("User must be logged in before its client can be used")
+        return self._client
+
     @property
     def is_connected(self) -> bool | None:
         return self._is_connected
@@ -242,7 +248,10 @@ class User(DBUser, BaseUser):
 
     @property
     def oauth_credential(self) -> OAuthCredential:
-        assert None not in (self.ktid, self.uuid, self.access_token, self.refresh_token)
+        assert self.ktid is not None
+        assert self.uuid is not None
+        assert self.access_token is not None
+        assert self.refresh_token is not None
         return OAuthCredential(
             self.ktid,
             self.uuid,
@@ -259,9 +268,9 @@ class User(DBUser, BaseUser):
             self.log.warning(f"UUID mismatch: expected {self.uuid}, got {oauth_credential.deviceUUID}")
             self.uuid = oauth_credential.deviceUUID
 
-    async def get_own_info(self) -> SettingsStruct:
-        if not self._logged_in_info or self._logged_in_info_time + 60 * 60 < time.monotonic():
-            self._logged_in_info = await self.client.get_settings()
+    async def get_own_info(self) -> SettingsStruct | None:
+        if self._client and (not self._logged_in_info or self._logged_in_info_time + 60 * 60 < time.monotonic()):
+            self._logged_in_info = await self._client.get_settings()
             self._logged_in_info_time = time.monotonic()
         return self._logged_in_info
 
@@ -280,7 +289,7 @@ class User(DBUser, BaseUser):
         user_info = await client.start()
         # NOTE On failure, client.start throws instead of returning something falsy
         self.log.info("Loaded session successfully")
-        self.client = client
+        self._client = client
         self._logged_in_info = user_info
         self._logged_in_info_time = time.monotonic()
         self._track_metric(METRIC_LOGGED_IN, True)
@@ -304,7 +313,7 @@ class User(DBUser, BaseUser):
         await self.logout(remove_ktid=False)
 
     async def is_logged_in(self, _override: bool = False) -> bool:
-        if not self.has_state or not self.client:
+        if not self.has_state or not self._client:
             return False
         if self._is_logged_in is None or _override:
             try:
@@ -360,9 +369,9 @@ class User(DBUser, BaseUser):
             self._is_rpc_reconnecting = False
 
     async def logout(self, *, remove_ktid: bool = True, reset_device: bool = False) -> None:
-        if self.client:
+        if self._client:
             # TODO Look for a logout API call
-            await self.client.stop()
+            await self._client.stop()
         if remove_ktid:
             await self.push_bridge_state(BridgeStateEvent.LOGGED_OUT)
         self._track_metric(METRIC_LOGGED_IN, False)
@@ -374,7 +383,7 @@ class User(DBUser, BaseUser):
 
         self._is_logged_in = False
         self.is_connected = None
-        self.client = None
+        self._client = None
 
         if self.ktid and remove_ktid:
             #await UserPortal.delete_all(self.ktid)
@@ -581,12 +590,12 @@ class User(DBUser, BaseUser):
             state.remote_name = puppet.name
 
     async def get_bridge_states(self) -> list[BridgeState]:
-        if not self.state:
+        if not self.has_state:
             return []
         state = BridgeState(state_event=BridgeStateEvent.UNKNOWN_ERROR)
         if self.is_connected:
             state.state_event = BridgeStateEvent.CONNECTED
-        elif self._is_rpc_reconnecting or self.client:
+        elif self._is_rpc_reconnecting or self._client:
             state.state_event = BridgeStateEvent.TRANSIENT_DISCONNECT
         return [state]
 
@@ -660,8 +669,8 @@ class User(DBUser, BaseUser):
                 await self.logout()
             await self.send_bridge_notice(f"Disconnected from KakaoTalk: {reason_str} {reason_suffix}")
 
-    def on_error(self, error: JSON) -> Awaitable[None]:
-        return self.send_bridge_notice(
+    async def on_error(self, error: JSON) -> None:
+        await self.send_bridge_notice(
             f"Got error event from KakaoTalk:\n\n> {error}",
             # TODO Which error code to use?
             #error_code="kt-connection-error",
@@ -671,7 +680,7 @@ class User(DBUser, BaseUser):
     async def on_client_disconnect(self) -> None:
         self.is_connected = False
         self._track_metric(METRIC_CONNECTED, False)
-        self.client = None
+        self._client = None
         if self._is_logged_in:
             if self.temp_disconnect_notices:
                 await self.send_bridge_notice(
@@ -685,12 +694,12 @@ class User(DBUser, BaseUser):
         self.log.debug(f"Successfully logged in as {oauth_credential.userId}")
         self.oauth_credential = oauth_credential
         await self.push_bridge_state(BridgeStateEvent.CONNECTING)
-        self.client = Client(self, log=self.log.getChild("ktclient"))
+        self._client = Client(self, log=self.log.getChild("ktclient"))
         await self.save()
         self._is_logged_in = True
         # TODO Retry network connection failures here, or in the client (like token refreshes are)?
         #      Should also catch unlikely authentication errors
-        self._logged_in_info = await self.client.start()
+        self._logged_in_info = await self._client.start()
         self._logged_in_info_time = time.monotonic()
         asyncio.create_task(self.post_login(is_startup=True))