hermes-chatto-plugin/adapter.py

"""Chatto Platform Adapter for Hermes Agent.

A plugin-based gateway adapter that connects to a Chatto server
(self-hosted team chat) and relays messages to/from the Hermes agent.


The adapter uses the chattolib library for all Chatto API interactions,
including both outbound messaging and realtime WebSocket connections.

"""

from __future__ import annotations

import random

from gateway.platforms.helpers import MessageDeduplicator

# Put the vendored dependencies for THIS platform on sys.path before importing
# anything from chattolib. Imported relatively as part of the plugin package and
# absolutely when this module is loaded standalone (e.g. by the tests).
try:
    from .vendor_path import setup_vendor_path
except ImportError:  # pragma: no cover - depends on how the module is loaded
    from vendor_path import setup_vendor_path

setup_vendor_path()

import asyncio
import hashlib
import logging
import mimetypes
import os
import ssl
import urllib.request as _urllib_request
from datetime import UTC, datetime
from enum import StrEnum
from typing import Any, cast
from urllib.parse import urlsplit

logger = logging.getLogger(__name__)

from gateway.config import Platform, PlatformConfig
from gateway.platforms.base import (
    BasePlatformAdapter,
    MessageEvent,
    MessageType,
    ProcessingOutcome,
    SendResult,
    cache_media_bytes,
    get_inbound_media_max_bytes,
    validate_inbound_media_size,
)

# Chattolib imports (vendored)
# Using vendored chattolib from vendor/chattolib/
# See vendor_chattolib.sh for how to update the vendored copy

# Absolute imports — vendor/ is on sys.path (see above) and chattolib's own
# modules import each other absolutely. Mixing in relative ".vendor.chattolib"
# imports would load a second, distinct copy of every module, so isinstance()
# checks across the two copies would silently fail.
try:
    from chattolib.client import (
        ChattoClient,
    )
    from chattolib.exceptions import (
        ChattoAuthError,
        ChattoError,
    )
    from chattolib.realtime import (
        ChattoRealtimeCloseError,
        ChattoRealtimeError,
        RealtimeEvent,
        stream_events,
    )
    from chattolib.realtime_types import (
        MessagePostedPayload,
        ReactionPayload,
    )
    from chattolib.types import PresenceStatus, RoomKind, RoomWithViewerState, User

except ImportError as e:
    # Fail loudly: continuing here only defers the failure to a confusing
    # NameError somewhere deep in the adapter.
    logger.error("Chatto: failed to import vendored chattolib: %s", e)
    raise


try:
    from .platform_config import (
        ChattoConfiguration,
        ChattoConstants,
    )
except ImportError:  # pragma: no cover - loaded as a top-level module (tests)
    from platform_config import (
        ChattoConfiguration,
        ChattoConstants,
    )


# --------------------------------------------------------------------------- #
# Chat types
# --------------------------------------------------------------------------- #


class HermesChatType(StrEnum):
    """The ``chat_type`` vocabulary the Hermes gateway understands.

    Declared in ``gateway/session.py:161`` as ``"dm", "group", "channel",
    "thread"`` and consumed as a bare string all over the gateway:
    ``SessionSource.description`` (session.py:239) and the PII-redacting
    description in ``build_session_context_prompt`` (session.py:537) both
    branch on these exact values and fall back to a nameless generic case for
    anything else, and ``build_session_key`` puts the value straight into the
    session key.  Passing a chattolib ``RoomKind`` (``"ROOM_KIND_CHANNEL"``)
    therefore does not fail loudly — it just quietly degrades what the agent is
    told about where it is.

    A StrEnum so it stays a drop-in ``str`` at every one of those call sites.

    GROUP vs CHANNEL
    ----------------
    There is no strict contract between the two, and the adapters disagree in
    practice: Slack labels every non-DM conversation ``"group"`` (including real
    channels), Discord uses both, and Telegram reserves ``"channel"`` for actual
    broadcast channels.  The intended reading is ``group`` = ordinary
    multi-participant chat, ``channel`` = broadcast surface.

    The distinction only changes behaviour in three places:

    1. Authorization (``gateway/authz_mixin.py``) — the only security-relevant
       one.  The group-scoped env allowlists apply to ``{"group", "forum"}``
       ONLY, never to ``"channel"``: ``{PLATFORM}_GROUP_ALLOWED_USERS`` /
       ``_GROUP_ALLOWED_CHATS`` (:616), the chat-id allowlist (:708) and the
       Telegram legacy shim (:724).  The adapter-delegation paths in turn treat
       all three alike (:461, :649, :674, :694), where the value only picks
       ``group_allow_from`` over ``allow_from`` from ``config.extra``.
       For Chatto both choices are equivalent today: those group env maps hold
       Telegram and QQBot only (:535-541), and our own allowlist runs through
       ``CHATTO_ALLOWED_USERS``, which is chat_type-independent.
    2. What the agent is told — ``SessionSource.description`` renders
       ``"group: Name"`` vs ``"channel: Name"`` (session.py:239-246), likewise
       the PII-redacted variant (session.py:537-544).
    3. The session key, which embeds the literal (session.py:1192).  Changing
       the value for a room re-buckets its existing sessions.

    Explicitly NOT affected: ``is_shared_multi_user_session`` (session.py:1063)
    only looks at ``"dm"`` and ``thread_id``, so sender prefixes, the multi-user
    prompt line and ``group_sessions_per_user`` treat group and channel
    identically.
    """

    DM = "dm"
    GROUP = "group"
    CHANNEL = "channel"
    # Emitted by adapters whose thread events are their own chat type (Slack,
    # Discord). We don't: a Chatto thread keeps its room's chat_type and is
    # identified by ``thread_id`` on the source instead. Listed for the record,
    # because build_session_key rewrites the slot to "thread" itself
    # (session.py:1190).
    THREAD = "thread"
    # Not declared in session.py:161 but real: Telegram forum topics travel as
    # "forum", and the authz group allowlists above accept it alongside "group".
    # Chatto has no equivalent, so we never emit it.


# Chatto only distinguishes DMs from channels. UNSPECIFIED means the server
# sent a kind this vendored chattolib doesn't know: map it to the generic
# multi-user bucket rather than guessing "channel", and never to "dm" — that
# value drives session isolation (is_shared_multi_user_session, session.py:1063)
# and would silently turn a room into a private conversation.
#
# CHANNEL for RoomKind.CHANNEL is the descriptive choice and carries no
# behavioural cost (see the GROUP vs CHANNEL note above). Switching to GROUP for
# Slack parity would be this one line — plus the re-bucketing of existing
# sessions that point 3 of that note describes.
_ROOM_KIND_TO_CHAT_TYPE: dict[RoomKind, HermesChatType] = {
    RoomKind.DM: HermesChatType.DM,
    RoomKind.CHANNEL: HermesChatType.CHANNEL,
    RoomKind.UNSPECIFIED: HermesChatType.GROUP,
}


def chat_type_for_room_kind(kind: RoomKind | None) -> HermesChatType:
    """Map a chattolib RoomKind onto the gateway's chat_type vocabulary.

    An unknown or missing kind becomes ``GROUP`` — see ``_ROOM_KIND_TO_CHAT_TYPE``.
    """
    if kind is None:
        return HermesChatType.GROUP
    return _ROOM_KIND_TO_CHAT_TYPE.get(kind, HermesChatType.GROUP)


# Blocking filesystem/network helpers. The adapter runs on the shared gateway
# event loop, so file reads and HTTP downloads are pushed to a worker thread
# via asyncio.to_thread — a slow disk or dead image URL must not stall every
# platform's message processing.


def _read_file_bytes(path: str) -> bytes:
    """Read a whole file synchronously (run via asyncio.to_thread)."""
    with open(path, "rb") as f:
        return f.read()


def _write_file_bytes(path: str, data: bytes) -> None:
    """Write bytes to a file synchronously (run via asyncio.to_thread)."""
    with open(path, "wb") as f:
        f.write(data)


def _download_to_file(url: str, path: str, timeout: float) -> None:
    """Download ``url`` to ``path`` synchronously (run via asyncio.to_thread)."""
    req = _urllib_request.Request(url, headers={"User-Agent": "Hermes/1.0"})
    try:
        ctx = ssl.create_default_context()
    except Exception:
        ctx = None
    with _urllib_request.urlopen(req, timeout=timeout, context=ctx) as resp:
        _write_file_bytes(path, resp.read())


# --------------------------------------------------------------------------- #
# Adapter
# --------------------------------------------------------------------------- #


def hermes_adapter_factory(config: PlatformConfig):
    """Construct a ChattoAdapter from a PlatformConfig."""
    return ChattoAdapter(config)


class ChattoAdapter(BasePlatformAdapter):
    """Chatto platform adapter.

    Receives messages via WebSocket realtime, sends via ConnectRPC.
    """

    _SPLIT_THRESHOLD = 9900
    # Read by BasePlatformAdapter.max_message_length_for_chat(), which the
    # gateway and the stream consumer use to chunk outgoing messages. Without
    # it they fall back to 4096 and split Chatto messages far earlier than
    # necessary — send() itself already truncates at 10000.
    MAX_MESSAGE_LENGTH = ChattoConstants.MAX_MESSAGE_LENGTH
    splits_long_messages = True
    supports_code_blocks: bool = True
    supports_status_text: bool = True  # client.update_custom_status

    def __init__(self, pconfig: PlatformConfig):
        """Signature needs to be compatible with BasePlatformAdapter.__init__."""
        super().__init__(
            config=pconfig, platform=Platform(ChattoConstants.PLATFORM_NAME)
        )
        # "extra" has been pre-processed by Hermes-Framework to be a dict of extra config values insode PlatformConfig.

        # --- Configuration from our configuration data class with some logic ---
        self.chatto_config: ChattoConfiguration = ChattoConfiguration(pconfig)

        # ------ State -------
        # SDK runtime handle (injected by Hermes); annotate for Pylance
        self.sdk: Any = getattr(self, "sdk", None)

        # Our own user, filled in by connect(). Events arriving before connect()
        # completes must not blow up on an undefined attribute.
        self.me: User | None = None

        # --- Runtime state ---
        self._user_id: str = ""
        self._user_display: str = ""
        self._room_names: dict[str, str] = {}
        self._room_kinds: dict[str, RoomKind] = {}
        self._our_thread_roots: set = set()  # thread root event IDs we created
        self._our_message_ids: set = (
            set()
        )  # message IDs we sent (for thread root detection)
        self._seen: list[str] = []  # Plain RealtimeEvent-id list
        self._resume_cursor: str | None = None
        self._watch_room_ids: list[str] = []
        # Rooms the server force-joined everyone into (Room.universal) — used
        # only for [universal] tags in the watch log, never for gating.
        self._universal_room_ids: set[str] = set()
        # One-shot guard for the unjoined-home-channel warning in _refresh_rooms.
        self._home_warning_logged = False
        self._ws_task: asyncio.Task | None = None
        self._presence_task: asyncio.Task | None = None
        self._ws_ready: asyncio.Event | None = None
        self._ws_active = False
        self._ws_ref = None  # reference to open websocket for dynamic resubscribe

        # Persistent typing indicator loops per room
        self._typing_tasks: dict[str, asyncio.Task] = {}

        # Member directory cache: user_id -> user info dict
        self._user_cache: dict[str, User] = {}
        # Handle -> does a user hold it. Cached both ways; see _mentions_someone_else.
        self._known_handles: dict[str, bool] = {}

        # Chattolib client cache and lock for async access.
        self._chatto_client: ChattoClient | None = None
        self._chatto_client_lock: asyncio.Lock = asyncio.Lock()

        # Dedup — chattolib may redeliver events across reconnects.
        self._dedup = MessageDeduplicator()

    # ------------------------------------------------------------------ #
    # Auth
    # ------------------------------------------------------------------ #

    async def _get_chatto_client(self: ChattoAdapter) -> ChattoClient | None:
        """Get or create a ChattoClient instance."""
        if self._chatto_client is not None:
            return self._chatto_client

        async with self._chatto_client_lock:
            if self._chatto_client is not None:
                return self._chatto_client

            try:
                assert (
                    self.chatto_config.login.value
                )  # now we can assume, _login is available.

                client = await self._open_client(
                    base_url=self.chatto_config.base_url.value,
                    login=self.chatto_config.login.value,
                    password=self.chatto_config.password.value,
                    token=self.chatto_config.token.value,
                )
                self._chatto_client = client
                self._token = client.token
                logger.info(
                    "Chatto: logged in as '%s' via chattolib",
                    self.chatto_config.login.value,
                )
                return client
            except ChattoAuthError as e:
                logger.error("Chatto: authentication failed: %s", e)
                return None
            except (ChattoError, ValueError) as e:
                logger.error("Chatto: failed to create client: %s", e)
                return None

    async def _require_client(self) -> ChattoClient:
        """Return a ChattoClient or raise RuntimeError if unavailable.

        Use this helper when the caller expects a client to exist and
        wants a single canonical failure path. Methods that prefer a
        soft-fail can catch RuntimeError and return gracefully.
        """
        client = await self._get_chatto_client()
        if client is None:
            raise RuntimeError("Chatto client unavailable")
        return client

    async def _ensure_token(self) -> bool:
        """Ensure we have a logged-in Chatto client and token."""
        if self.chatto_config.token.value and isinstance(
            self._chatto_client, ChattoClient
        ):
            return True

        client = await self._get_chatto_client()
        return client is not None

    # ------------------------------------------------------------------ #
    # Connection
    # ------------------------------------------------------------------ #
    async def _open_client(
        self,
        *,
        base_url: str,
        login: str,
        password: str,
        token: str | None = None,
    ) -> ChattoClient:
        """Return a connected ``ChattoClient`` using token or login/password."""
        if token:
            return ChattoClient(token=token, base_url=base_url)
        return await ChattoClient.login(login, password, base_url=base_url)

    async def connect(self, *, is_reconnect: bool = False) -> bool:
        """Connect to Chatto and start the realtime event stream.

        BasePlatformAdapter override
        """
        logger.info("Chatto: connecting...")

        if not await self._ensure_token():
            return False

        try:
            client = await self._require_client()
        except RuntimeError:
            self._set_fatal_error(
                "connect_failed", "Chatto client not available", retryable=True
            )
            return False

        # Get our first own user info
        try:
            self.me = await client.me()
        except Exception as exc:
            logger.error("Chatto: failed to get user info: %s", exc)
            self._set_fatal_error(
                "chatto_auth_failed",
                f"Chatto auth failed: {exc}",
                retryable=False,
            )
            try:
                assert self._chatto_client
                await self._chatto_client.close()
            finally:
                self._chatto_client = None
            return False

        # Announce online presence so the bot appears online in the member list.
        # The server treats this as a TTL, so _presence_refresh_loop below has to
        # keep re-announcing it — a single call here lapses back to offline.
        await self._announce_online()

        self._closing = False
        # Start background realtime WS event stream loop.
        self._ws_ready = asyncio.Event()
        self._ws_task = asyncio.create_task(
            self._chattolib_event_loop(),
            name="chatto-event-stream",
        )
        self._presence_task = asyncio.create_task(
            self._presence_refresh_loop(),
            name="chatto-presence-refresh",
        )
        self._mark_connected()

        logger.info(
            "Chatto: connected and authentiated to %s using login:'%s' (display_name:'%s' id: '%s')",
            self.chatto_config.base_url.value,
            self.me.login,
            self.me.display_name,
            self.me.id,
        )

        return True

    async def _announce_online(self) -> bool:
        """Tell the server we are online. Returns whether the call got through.

        Logged at warning level on failure: a silently dropped presence call is
        indistinguishable from a bot that is simply not running.
        """
        try:
            client = await self._require_client()
            await client.update_presence(status=PresenceStatus.ONLINE)
            return True
        except Exception as exc:
            logger.warning(
                "Chatto: presence refresh failed, bot may appear offline: %s", exc
            )
            return False

    async def _presence_refresh_loop(self) -> None:
        """Re-announce ONLINE until disconnect, since presence expires server-side.

        Failures are not fatal — the next tick tries again, so a blip in the
        presence endpoint costs at most one interval of visible offline time.
        """
        while not self._closing:
            await self._sleep_interruptible(ChattoConstants.PRESENCE_REFRESH_INTERVAL)
            if self._closing:
                return
            await self._announce_online()

    async def disconnect(self) -> None:
        """Stop WebSocket, presence refresh, typing tasks, and clear state.

        BasePlatformAdapter override
        """
        # No explicit offline broadcast: chattolib rejects OFFLINE outright
        # ("stop refreshing to go offline"), so cancelling the refresh loop
        # below is what actually takes the bot offline.
        self._ws_active = False
        self._closing = True

        # Cancel all typing tasks
        for chat_id in list(self._typing_tasks.keys()):
            await self.stop_typing(chat_id)

        if self._ws_task and not self._ws_task.done():
            self._ws_task.cancel()
            try:
                await self._ws_task
            except (asyncio.CancelledError, Exception):
                logger.debug(
                    "Chatto: websocket task ended during disconnect", exc_info=True
                )
            self._ws_task = None

        if self._presence_task and not self._presence_task.done():
            self._presence_task.cancel()
            try:
                await self._presence_task
            except (asyncio.CancelledError, Exception):
                logger.debug(
                    "Chatto: presence task ended during disconnect", exc_info=True
                )
        self._presence_task = None

        if self._chatto_client:
            try:
                await self._chatto_client.close()
            except Exception:
                logger.exception("Chatto: error closing client")
            finally:
                self._chatto_client = None

        self._token = None
        logger.info("Chatto: disconnected")
        self._mark_disconnected()

    async def _seed_room(self, room_id: str) -> None:
        """Seed high-water mark from the newest events so a restart doesn't replay history."""
        try:
            try:
                client = await self._require_client()
                timeline_page = await client.get_room_events(room_id)
            except RuntimeError:
                logger.debug(
                    "Chatto: _seed_room aborted - no client available for %s", room_id
                )
                return

            for ev in timeline_page.events:
                if ev.id:
                    self._mark_seen(ev.id)
            logger.debug(
                "Chatto: seeded room %s with %d events",
                room_id,
                len(timeline_page.events),
            )
        except Exception as e:
            logger.debug("Chatto: get room events failed for %s: %s", room_id, e)

    # ------------------------------------------------------------------ #
    # Realtime Event List
    # ------------------------------------------------------------------ #

    def _mark_seen(self, event_id: str) -> None:
        self._seen.append(event_id)
        while len(self._seen) > ChattoConstants.SEEN_CAP:
            self._seen.remove(self._seen[0])  # fastest removal of first item in a list.

    def _is_seen(self, event_id: str) -> bool:
        return event_id in self._seen

    # ------------------------------------------------------------------ #
    # WebSocket Realtime Transport
    # ------------------------------------------------------------------ #

    def _mentions_me(self, body: str) -> bool:
        """Whether the message addresses this bot.

        By login, by display name, or by a broadcast handle — ``@here`` speaks
        to everyone present and the bot is one of them, so naming a colleague
        alongside it does not take the bot out of the audience.
        """
        if not self.me:
            return False
        for handle in (self.me.login, self.me.display_name):
            if handle and f"@{handle}" in body:
                return True
        return any(
            handle.lower() in ChattoConstants.BROADCAST_MENTIONS
            for handle in ChattoConstants.MENTION_RE.findall(body)
        )

    async def _handle_belongs_to_a_user(self, handle: str) -> bool:
        """Whether ``handle`` is the login of a real Chatto user.

        The API carries no mention entities — ``mention_confirmation_token`` is
        reserved in the message descriptor — so an @-token is only a candidate
        until the directory confirms it. Results are cached both ways, since
        the same handles recur and a miss is as reusable as a hit.
        """
        known = self._known_handles.get(handle)
        if known is not None:
            return known
        try:
            client = await self._require_client()
            member = await client.get_user(login=handle)
        except Exception as exc:
            # Unresolved means "not confirmed", so the message goes through.
            logger.debug("Chatto: could not resolve handle @%s: %s", handle, exc)
            return False
        exists = member is not None and member.user is not None
        self._known_handles[handle] = exists
        return exists

    async def _mentions_someone_else(self, body: str) -> bool:
        """Whether the message @-mentions a person who is not this bot.

        Broadcast handles are not a person — they address everyone present,
        the bot included, so they do not count as someone else. A handle no
        user holds is not a mention at all: someone writing *about* mentioning
        ("per @-mention", "@nonexistent") is talking to us, and staying silent
        on a false positive is worse than answering one.
        """
        for handle in ChattoConstants.MENTION_RE.findall(body):
            if handle.lower() in ChattoConstants.BROADCAST_MENTIONS:
                continue
            if self.me and handle in (self.me.login, self.me.display_name):
                continue
            if await self._handle_belongs_to_a_user(handle):
                return True
        return False

    def _check_auth(self, user: User) -> bool:
        """We roll our own auth-systen on the against the chatto_config'ured allowed_users etc.

        because.. Hermes authz_mixin.py IS NOT SANE.
        """
        if self.chatto_config.allow_all_users.value:
            return True
        if user.login in self.chatto_config.allowed_users.value:
            return True
        if user.id in self.chatto_config.allowed_users.value:
            return True
        logger.info(
            "Chatto: rejecting message from unauthorized user '%s' (%s)",
            user.login,
            user.id,
        )
        return False

    # ------------------------------------------------------------------ #
    # Room management over DM (/join, /leave)
    # ------------------------------------------------------------------ #

    _DM_COMMANDS = ("/join", "/leave")

    async def _handle_dm_command(self, room_id: str, body: str) -> bool:
        """Run a ``/join`` or ``/leave`` admin command sent as a direct message.

        Returns True when ``body`` is one of the commands — whether it
        succeeded or not — so the caller keeps it out of the agent pipeline.
        Membership lives on the Chatto server: a joined room reappears in
        every future ``list_rooms()`` and therefore survives restarts.
        """
        verb, _, argument = body.strip().partition(" ")
        if verb.lower() not in self._DM_COMMANDS:
            return False

        try:
            client = await self._require_client()
        except RuntimeError:
            await self.send(chat_id=room_id, content="Chatto client is not connected.")
            return True

        argument = argument.strip()
        if not argument:
            await self.send(
                chat_id=room_id,
                content="Usage: /join <room-id or #name> | /leave <room-id or #name>",
            )
            return True

        error, target = await self._resolve_room_target(client, argument)
        if error or target is None:
            await self.send(chat_id=room_id, content=error or "Room lookup failed.")
            return True

        if verb.lower() == "/join":
            reply = await self._run_join(client, target)
        else:
            reply = await self._run_leave(client, target)
        await self.send(chat_id=room_id, content=reply)
        return True

    async def _resolve_room_target(
        self,
        client: ChattoClient,
        argument: str,
    ) -> tuple[str | None, RoomWithViewerState | None]:
        """Resolve a /join//leave argument to a room.

        ``#name`` is looked up case-insensitively in a fresh directory scan
        (which also refreshes our name/kind caches); anything else is treated
        as a room ID and verified via GetRoom. An ambiguous name comes back as
        an error naming the candidates, so the admin can retry with an ID.
        """
        if not argument.startswith("#"):
            state = await client.get_room(argument)
            if state is None or state.room is None:
                return f"No room with ID '{argument}'.", None
            return None, state

        wanted = argument[1:].strip().casefold()
        matches: list[RoomWithViewerState] = []
        for state in await client.list_rooms() or []:
            room_obj = state.room if state else None
            if room_obj and (room_obj.name or "").strip().casefold() == wanted:
                matches.append(state)
                self._room_names[room_obj.id] = room_obj.name
                self._room_kinds[room_obj.id] = room_obj.kind
        if not matches:
            return f"No room named '{argument}'.", None
        if len(matches) > 1:
            candidates = "\n".join(f"• {m.room.name} ({m.room.id})" for m in matches)
            return (
                f"Several rooms are named '{argument}' — pick one by ID:\n{candidates}"
            ), None
        return None, matches[0]

    async def _run_join(self, client: ChattoClient, state: RoomWithViewerState) -> str:
        """Join a room via RoomService/JoinRoom and watch it immediately.

        An account that already holds membership (invited natively in Chatto)
        needs no JoinRoom call — it only gets seeded into the watch list.
        """
        room_obj = state.room
        label = f"'{room_obj.name}' ({room_obj.id})"
        joined_room = room_obj
        if not state.viewer_state.is_member:
            try:
                joined_room = await client.join_room(room_obj.id) or room_obj
            except ChattoError as exc:
                logger.warning("Chatto: /join failed for %s (%s)", room_obj.id, exc)
                return f"Could not join {label}: {exc}"
        self._room_names[joined_room.id] = joined_room.name
        self._room_kinds[joined_room.id] = joined_room.kind
        if joined_room.id not in self._watch_room_ids:
            await self._seed_room(joined_room.id)
            self._watch_room_ids.append(joined_room.id)
        if state.viewer_state.is_member:
            return f"Already a member of {label} — watching it."
        return f"Joined {label}."

    async def _run_leave(self, client: ChattoClient, state: RoomWithViewerState) -> str:
        """Leave a room via RoomService/LeaveRoom and stop watching it.

        Two rooms are refused: a DM conversation cannot be left, and leaving
        the configured home channel would silently break cron/notification
        delivery, which posts there through the standalone sender.
        """
        room_obj = state.room
        label = f"'{room_obj.name}' ({room_obj.id})"
        if room_obj.kind == RoomKind.DM:
            return "Direct messages cannot be left."
        home_id = (self.chatto_config.home_channel.value or "").strip()
        if home_id == room_obj.id:
            return (
                f"{label} is the configured home channel "
                "(CHATTO_HOME_CHANNEL); leaving it would break cron and "
                "notification delivery. Point CHATTO_HOME_CHANNEL elsewhere first."
            )
        try:
            left = await client.leave_room(room_obj.id)
        except ChattoError as exc:
            logger.warning("Chatto: /leave failed for %s (%s)", room_obj.id, exc)
            return f"Could not leave {label}: {exc}"
        if not left:
            return f"Chatto refused to leave {label}."
        if room_obj.id in self._watch_room_ids:
            self._watch_room_ids.remove(room_obj.id)
        return f"Left {label}."

    # ------------------------------------------------------------------ #
    # Inbound attachments
    # ------------------------------------------------------------------ #

    async def _download_attachment_bytes(self, url: str) -> bytes:
        """Download an attachment, refusing to buffer more than the gateway cap.

        The Content-Length header is checked first so an oversized asset is
        rejected before a single chunk is read; the running total is re-checked
        as chunks arrive, because a missing or lying header must not smuggle an
        unbounded body past the cap.
        """
        import httpx

        max_bytes = get_inbound_media_max_bytes()
        chunks: list[bytes] = []
        total = 0
        async with (
            httpx.AsyncClient(
                timeout=ChattoConstants.HTTP_TIMEOUT,
                follow_redirects=True,
            ) as http,
            http.stream("GET", url) as resp,
        ):
            resp.raise_for_status()
            declared = resp.headers.get("content-length")
            if declared:
                try:
                    declared_size = int(declared)
                except ValueError:
                    logger.debug("Chatto: ignoring invalid Content-Length %r", declared)
                else:
                    validate_inbound_media_size(
                        declared_size,
                        media_type="attachment",
                        max_bytes=max_bytes,
                    )
            async for chunk in resp.aiter_bytes():
                total += len(chunk)
                validate_inbound_media_size(
                    total,
                    media_type="attachment",
                    max_bytes=max_bytes,
                )
                chunks.append(chunk)
        return b"".join(chunks)

    async def _cache_attachments(
        self,
        room_id: str,
        attachments: list[Any],
    ) -> tuple[list[str], list[str], list[str]]:
        """Download message attachments into the gateway media cache.

        Returns ``(media_urls, media_types, media_kinds)`` — the paths are
        agent-visible cache paths, exactly what ``cache_media_bytes`` yields for
        every other platform.  A failing attachment is logged and skipped: the
        message itself still reaches the agent.
        """
        media_urls: list[str] = []
        media_types: list[str] = []
        media_kinds: list[str] = []

        for att in attachments or []:
            asset_url = getattr(att, "asset_url", None)
            url = getattr(asset_url, "url", "") if asset_url else ""
            filename = getattr(att, "filename", "") or ""
            content_type = getattr(att, "content_type", "") or ""
            if not url:
                # Videos are announced before transcoding finishes, so the
                # signed URL can legitimately be missing on arrival.
                logger.info(
                    "Chatto: attachment '%s' has no asset URL yet, skipping",
                    filename,
                )
                continue
            try:
                data = await self._download_attachment_bytes(url)
                cached = cache_media_bytes(
                    data,
                    filename=filename,
                    mime_type=content_type,
                )
            except Exception as e:
                logger.warning(
                    "Chatto: failed to cache attachment '%s' (%s): %s",
                    filename,
                    content_type,
                    e,
                )
                continue
            if cached is None:
                logger.warning(
                    "Chatto: attachment '%s' (%s) could not be cached, skipping",
                    filename,
                    content_type,
                )
                continue
            media_urls.append(cached.path)
            media_types.append(cached.media_type)
            media_kinds.append(cached.kind)

        return media_urls, media_types, media_kinds

    @staticmethod
    def _message_type_for_media_kinds(media_kinds: list[str]) -> MessageType:
        """Pick the MessageType for a set of cached attachment kinds."""
        if "document" in media_kinds:
            return MessageType.DOCUMENT
        if "image" in media_kinds:
            return MessageType.PHOTO
        if "video" in media_kinds:
            return MessageType.VIDEO
        if "audio" in media_kinds:
            return MessageType.AUDIO
        return MessageType.TEXT

    def _is_respond_room(self, room_id: str) -> bool:
        """Whether inbound messages from this room reach the agent pipeline.

        With ``CHATTO_RESPOND_ROOMS`` set, every non-DM room is gated against
        that positive list; rooms outside it stay read-only (marked as read,
        never seeded or answered). DMs are always respond rooms so ``/join``
        stays reachable, and unknown room kinds fail closed.
        """
        respond_rooms = self.chatto_config.respond_rooms.value
        if not respond_rooms:
            return True
        if self._room_kinds.get(room_id) == RoomKind.DM:
            return True
        return room_id in respond_rooms

    async def _dispatch_message_posted(self, payload: MessagePostedPayload) -> None:
        # Respond-room gate first: read-only memberships must not cost a
        # single API call, so this runs before fetch_message and _require_client.
        if not self._is_respond_room(payload.room_id):
            logger.debug(
                "Chatto: message from read-only room %s ignored", payload.room_id
            )
            return

        try:
            client = await self._require_client()
        except RuntimeError:
            logger.warning("Chatto: chattolib event loop aborted - no client available")
            return
        logger.info("Chatto WS: 'message_posted' payload:%s", payload)

        message = await payload.fetch_message(client=client)
        if message is None or message.deleted_at:
            return
        message_body = message.body or ""
        logger.info("message: %s", message)

        attachments = list(message.attachments or [])
        # A message carrying only an image/PDF has an empty body — dropping it
        # here is what made attachments sent to Hermes disappear silently.
        if not message_body and not attachments:
            return

        if message.actor_id in self._user_cache:
            # try the user cache.
            user = self._user_cache.get(message.actor_id)
        else:
            # get the user and update cache.
            directory_member = await client.get_user(user_id=message.actor_id)
            if directory_member is None:
                return
            user = directory_member.user
            if user is None:
                return
            self._user_cache[user.id] = user

        if user is None:
            return

        if not self._check_auth(user):
            return

        # Todo: use a function that either reads from cache or gets room kind again.
        if self._room_kinds.get(message.room_id) is None:
            room_viewer_state = await client.get_room(message.room_id)
            if room_viewer_state is None:
                return
            if room_viewer_state.room is None:
                return
            self._room_kinds[message.room_id] = (
                room_viewer_state.room.kind or RoomKind.UNSPECIFIED
            )

        room_kind = self._room_kinds.get(message.room_id)

        logger.info("message_body: %s room_kind: %s", message_body, room_kind)

        # Membership commands ride in over DMs only: they change what the bot
        # listens to and must never reach the agent pipeline or the mention
        # gates.
        if room_kind == RoomKind.DM and await self._handle_dm_command(
            message.room_id,
            message_body,
        ):
            return

        # require_mention deliberately gates channels only: in a channel the bot
        # is one of many listeners and must be addressed, whereas a DM is already
        # addressed at it — so DMs are always answered, mention or not.
        mentioned = False
        if (
            room_kind == RoomKind.CHANNEL
            and self.chatto_config.require_mention.value
            and self.me
        ):
            if self.me.login and not mentioned:
                mentioned = bool(f"@{self.me.login}" in message_body)
            if self.me.display_name and not mentioned:
                mentioned = bool(f"@{self.me.display_name}" in message_body)
            if mentioned is False:
                logger.debug(
                    "Discarding message. Bot was not mentionend but require_mention is '%s'.",
                    self.chatto_config.require_mention.value,
                )
                return

        logger.info("mentioned: %s", mentioned)

        # With require_mention off we see every message in the channel, including
        # ones plainly aimed at a named colleague. Answering those would be
        # barging in, so acknowledge that we read it and stay quiet. Checked
        # after the bot-mention test above, so a message naming us *and* someone
        # else still counts as ours.
        if (
            room_kind == RoomKind.CHANNEL
            and not self.chatto_config.require_mention.value
            and not self._mentions_me(message_body)
            and await self._mentions_someone_else(message_body)
        ):
            logger.info("Chatto: message addresses someone else, acknowledging only")
            if self.chatto_config.reactions.value:
                await self.add_reaction(message.room_id, message.id, "🫥")
            return

        # Thread anchoring — if the incoming message is inside a Chatto thread, we
        # keep that thread by default; otherwise leave thread_id unset so
        # replies land at the root.
        thread_id = (
            payload.thread_root_event_id or None
        )  # we could also take "payload.room_id" but then, we're in a thread already.
        if not thread_id and room_kind != RoomKind.DM:
            thread_id = message.id

        source = self.build_source(
            chat_id=payload.room_id,
            chat_name=self._room_names.get(message.room_id),
            chat_type=chat_type_for_room_kind(room_kind),
            user_id=message.actor_id,
            user_name=user.login,  # use login, because display_name is changeable by anyone.
            thread_id=thread_id,
            message_id=payload.message_event_id,
            role_authorized=True,
        )

        # prepare a MessageEvent
        message_event = MessageEvent(
            text=message_body,
            source=source,
            message_id=message.id,
            timestamp=message.created_at or datetime.now(UTC),
            raw_message=message,
            reply_to_message_id=message.in_reply_to,
        )
        if message_event.is_command():
            message_event.message_type = MessageType.COMMAND

        # Attachments — download and hand the local cache paths to the gateway,
        # which runs vision enrichment / document extraction off media_urls.
        (
            message_event.media_urls,
            message_event.media_types,
            media_kinds,
        ) = await self._cache_attachments(
            payload.room_id,
            attachments,
        )
        if media_kinds:
            # Same precedence as the Teams/Signal adapters: document-context
            # injection gates strictly on DOCUMENT, image handling keys off the
            # per-path image/* MIME regardless of message_type.
            message_event.message_type = self._message_type_for_media_kinds(media_kinds)
        else:
            message_event.message_type = MessageType.TEXT

        logger.info("Chatto: Dispatching MessageEvent to Hermes: %s", message_event)
        await self.handle_message(message_event)
        return

    async def _forward_reaction(
        self,
        event: RealtimeEvent,
        payload: ReactionPayload,
        *,
        removed: bool,
    ) -> None:
        """Forward a human reaction to the gateway's reaction hook surface.

        The handler is registered by the gateway via ``set_reaction_handler``
        and fans out as ``reaction:added`` / ``reaction:removed`` through the
        HookRegistry.  The dict shape mirrors the Slack adapter's — hook
        consumers are written against that contract, not against a per-platform
        one.  Our own lifecycle reactions (👀/✅/❌) are dropped: forwarding them
        would feed the agent its own markers.
        """
        actor_id = event.actor_id
        if actor_id and self.me and actor_id == self.me.id:
            return
        if not payload.room_id or not payload.message_event_id or not actor_id:
            return

        handler = getattr(self, "_reaction_handler", None)
        if handler is None:
            return

        action = "removed" if removed else "added"
        try:
            await handler(
                {
                    "platform": ChattoConstants.PLATFORM_NAME,
                    "event_name": f"reaction:{action}",
                    "reaction": payload.emoji,
                    "user_id": actor_id,
                    "item_user_id": None,
                    "item_type": "message",
                    "channel_id": payload.room_id,
                    "message_ts": payload.message_event_id,
                    "event_ts": event.id,
                    "raw_event": event,
                },
            )
        except Exception:  # pragma: no cover - the hook contract is non-blocking
            logger.debug("Chatto: reaction hook forwarding failed", exc_info=True)

    async def _handle_realtime_event(self, event: RealtimeEvent) -> None:
        if self._is_seen(event.id):
            return

        if event.actor_id is None:
            return

        logger.info("EVENT happened: '%s' from %s", event.kind, event.actor_id)

        if (event_payload := event.get("message_posted")) is not None:
            # Self-event filter — the actor_id on the envelope is authoritative
            # (chattolib does NOT filter this itself; see chatto-bridge notes).
            actor_id = event.actor_id
            if actor_id and self.me and actor_id == self.me.id:
                return

            await self._dispatch_message_posted(event_payload)

        elif event.kind in ("reaction_added", "reaction_removed"):
            reaction_payload = event.get(event.kind)
            if reaction_payload is not None:
                await self._forward_reaction(
                    event,
                    cast(ReactionPayload, reaction_payload),
                    removed=event.kind == "reaction_removed",
                )

        # confirmed:
        elif event.kind in (
            "mention_notification",
            "projection_event",
            "presence_changed",
            "notification_dismissed",
            "room_marked_as_read",
            "user_typing",
            "notification_created",
            "new_direct_message_notification",
            "message_edited",
            "message_retracted",
        ):
            logger.debug(
                "Chatto: '%s' event received. Not yet implemented or not needed.",
                event.kind,
            )
        else:
            logger.error("Chatto: unknown event kind: '%s'", event.kind)

    async def _chattolib_event_loop(self) -> None:
        """Event loop using chattolib's stream_events.

        This replaces the manual WebSocket loop with chattolib's high-level
        stream_events() which provides pre-decoded RealtimeEvent objects.
        """
        delay = ChattoConstants.WS_RECONNECT_INITIAL_BACKOFF
        while not self._closing:
            try:
                client = await self._require_client()

                await self._refresh_rooms()
                logger.info(
                    "Chatto: starting chattolib event stream with %d rooms",
                    len(self._watch_room_ids),
                )

                async for event in stream_events(client):
                    if self._closing:
                        return
                    await self._handle_realtime_event(event)
                # Iterator exited cleanly — treat as a normal close and reconnect
                # with the local backoff (no server hint available).
                logger.info("Chatto: realtime stream ended, reconnecting")
            except asyncio.CancelledError:
                return
            except ChattoRealtimeCloseError as exc:
                if not exc.reconnect:
                    logger.error(
                        "Chatto: realtime closed by server (%s: %s), not reconnecting",
                        exc.code,
                        exc.message,
                    )
                    return
                wait = max(
                    exc.retry_after_ms / 1000.0,
                    ChattoConstants.WS_RECONNECT_INITIAL_BACKOFF,
                )
                logger.warning(
                    "Chatto: realtime closed by server (%s), reconnecting in %.1fs",
                    exc.code,
                    wait,
                )
                delay = (
                    ChattoConstants.WS_RECONNECT_INITIAL_BACKOFF
                )  # server hint supersedes local backoff
                await self._sleep_interruptible(wait)
                continue
            except ChattoRealtimeError as exc:
                if getattr(exc, "fatal", False):
                    logger.error(
                        "Chatto: fatal realtime error (%s): %s", exc.code, exc.message
                    )
                    return
                logger.warning(
                    "Chatto: realtime error (%s: %s), reconnecting in %.1fs",
                    exc.code,
                    exc.message,
                    delay,
                )
            except Exception as exc:
                logger.warning(
                    "Chatto: unexpected realtime error: %s, reconnecting in %.1fs",
                    exc,
                    delay,
                )

            if self._closing:
                return

            jitter = delay * 0.2 * random.random()
            await self._sleep_interruptible(delay + jitter)
            delay = min(delay * 2, ChattoConstants.WS_RECONNECT_MAX_BACKOFF)

    async def _sleep_interruptible(self, seconds: float) -> None:
        """Sleep in short slices so disconnect() cancels promptly."""
        end = asyncio.get_running_loop().time() + seconds
        while not self._closing:
            remaining = end - asyncio.get_running_loop().time()
            if remaining <= 0:
                return
            await asyncio.sleep(min(remaining, 0.5))

    def _warn_if_home_channel_unjoined(self, member_ids: set[str]) -> None:
        """Warn once when CHATTO_HOME_CHANNEL names a room the bot is not in.

        Standalone cron delivery posts straight into that room with a fresh
        client and no join logic of its own — without server-side membership
        every proactive send fails there.
        """
        home_id = (self.chatto_config.home_channel.value or "").strip()
        if (
            not home_id
            or home_id in member_ids
            or home_id in self._watch_room_ids
            or self._home_warning_logged
        ):
            return
        self._home_warning_logged = True
        logger.warning(
            "Chatto: CHATTO_HOME_CHANNEL '%s' is not a joined room - cron and "
            "notification delivery will fail until the bot joins it (invite "
            "the account natively in Chatto, or DM it '/join').",
            home_id,
        )

    async def _refresh_rooms(self) -> None:
        """Refresh room list via ConnectRPC, join and seed any newly discovered rooms."""
        try:
            client = await self._require_client()
        except RuntimeError:
            logger.warning("Chatto WS: _refresh_rooms aborted - no client available")
            return

        try:
            rooms_list = await client.list_rooms()
            respond_rooms = self.chatto_config.respond_rooms.value
            member_ids: set[str] = set()
            new_room_ids: list[str] = []

            for room_with_state in rooms_list:
                if not room_with_state:
                    continue

                room_obj = room_with_state.room or None
                if not room_obj:
                    continue

                self._room_names[room_obj.id] = room_obj.name
                self._room_kinds[room_obj.id] = room_obj.kind
                if room_obj.universal:
                    self._universal_room_ids.add(room_obj.id)

                if not room_with_state.viewer_state.is_member:
                    continue
                member_ids.add(room_obj.id)
                if room_obj.id not in self._watch_room_ids:
                    new_room_ids.append(room_obj.id)

            # Watched rooms we no longer belong to (left via /leave, kicked,
            # deleted) drop out here — otherwise the next refresh would
            # quietly re-add what /leave just removed.
            stale_room_ids = [
                rid for rid in self._watch_room_ids if rid not in member_ids
            ]
            for rid in stale_room_ids:
                self._watch_room_ids.remove(rid)
            if stale_room_ids:
                logger.info(
                    "Chatto WS: no longer a member of %d room(s): %s",
                    len(stale_room_ids),
                    stale_room_ids,
                )

            unjoined_listed = [rid for rid in respond_rooms if rid not in member_ids]
            if unjoined_listed:
                logger.warning(
                    "Chatto WS: CHATTO_RESPOND_ROOMS lists room(s) we are not a"
                    " member of: %s",
                    unjoined_listed,
                )

            self._warn_if_home_channel_unjoined(member_ids)

            if not new_room_ids:
                return

            logger.info(
                "Chatto WS: discovered %d new room(s): %s",
                len(new_room_ids),
                new_room_ids,
            )

            for rid in new_room_ids:
                if self._room_kinds.get(rid) != RoomKind.DM:
                    await client.join_room(
                        rid
                    )  # but list_rooms() would not return any if we were not already joined?!
                if self._is_respond_room(rid):
                    await self._seed_room(rid)
                else:
                    logger.info(
                        "Chatto WS: %s (%s) is outside CHATTO_RESPOND_ROOMS -"
                        " watching read-only",
                        self._room_names.get(rid, rid),
                        rid,
                    )
                self._watch_room_ids.append(rid)

            watch_room_names: list[str] = []
            for rid in self._watch_room_ids:
                name = self._room_names[rid]
                if not self._is_respond_room(rid):
                    name += " [read-only]"
                if rid in self._universal_room_ids:
                    name += " [universal]"
                watch_room_names.append(name + " (" + rid + ")")

            logger.info(
                "Chatto WS: Watching %d room(s): %s",
                len(self._watch_room_ids),
                ", ".join(watch_room_names),
            )

        except Exception:
            logger.warning("Chatto WS: _refresh_rooms failed", exc_info=True)

        # ------------------------------------------------------------------ #
        # Read state & notification dismissal (best-effort, Chatto-unique)
        # ------------------------------------------------------------------ #
        # Best-effort: mark all watched rooms as read (room_id may be undefined here)
        for _rid in list(self._watch_room_ids):
            try:
                await client.mark_room_as_read(room_id=_rid)
                await client.dismiss_all_notifications()
            except Exception:
                logger.debug(
                    "Chatto: mark_room_as_read failed for %s", _rid, exc_info=True
                )

    # ------------------------------------------------------------------ #
    # Sending (ConnectRPC — unchanged from polling version)
    # ------------------------------------------------------------------ #

    async def send(
        self,
        chat_id: str,
        content: str,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
    ) -> SendResult:
        """Send a message to a Chatto room.

        Long messages are split into chunks via ``truncate_message`` and
        each chunk is sent as a separate CreateMessage call.  The first
        chunk's message ID is returned as ``message_id``.

        When ``auto_thread`` is enabled and the incoming message was a
        regular room message (not already in a thread), the first chunk is
        sent as a room message and its ID becomes the thread root. Subsequent
        chunks are sent in that thread. This mirrors Discord's auto_thread
        behavior.

        BasePlatformAdapter override
        """
        if not content:
            return SendResult(success=False, error="Empty message")

        formatted = self.format_message(content)
        chunks = self.truncate_message(formatted, ChattoConstants.MAX_MESSAGE_LENGTH)

        # Thread support — resolve thread_id once
        # DM rooms don't support threads, so skip threading for DMs
        thread_id = (metadata or {}).get("thread_id")
        # Only use reply_to as thread_id if auto_thread is enabled.
        # When auto_thread=false, responses go directly in the room
        # without threading under the incoming message.
        # If we already have thread_id from metadata, keep it (it's the
        # thread root); only use reply_to when we don't already have one.
        if reply_to and self.chatto_config.auto_thread.value and not thread_id:
            thread_id = reply_to
        # Check if this is a DM room — DMs don't support threads
        room_kind = self._room_kinds.get(chat_id)
        is_dm = room_kind == RoomKind.DM
        if is_dm:
            thread_id = None

        # Auto-thread: by default, Chatto creates a thread for replies to room
        # messages (not DMs, not already in a thread). This keeps conversations
        # organized in the room. Can be disabled via extra.auto_thread=false.
        use_auto_thread = (
            self.chatto_config.auto_thread.value and not thread_id and not is_dm
        )

        message_ids: list[str] = []
        last_error: str | None = None
        retryable = False

        try:
            client = await self._require_client()
        except RuntimeError:
            return SendResult(
                success=False, error="Chatto client not available", retryable=True
            )

        for i, chunk in enumerate(chunks):
            try:
                msg_obj = await client.post_message(
                    room_id=chat_id,
                    body=chunk,
                    thread_root_event_id=str(thread_id) if thread_id else "",
                )
            except ChattoError as e:
                last_error = str(e)
                retryable = True
                break
            except Exception as e:
                last_error = str(e)
                retryable = True
                break

            self._mark_seen(msg_obj.id)
            message_ids.append(msg_obj.id)
            self._our_message_ids.add(msg_obj.id)
            # If we sent a message WITHOUT a thread_id, this message could
            # become a thread root if someone replies to it
            if not thread_id:
                self._our_thread_roots.add(msg_obj.id)
            # Auto-thread: first chunk becomes the thread root,
            # subsequent chunks go in the thread
            if use_auto_thread and i == 0 and not thread_id:
                thread_id = msg_obj.id

        # Nothing got through at all — report the failure instead of a phantom success.
        if not message_ids:
            return SendResult(
                success=False,
                error=last_error or "Chatto: message could not be sent",
                retryable=retryable,
            )

        first_id = message_ids[0]

        # ------------------------------------------------------------------ #
        # Thread following (best-effort, Chatto-unique)
        # ------------------------------------------------------------------ #
        if thread_id:
            try:
                await client.follow_thread(chat_id, thread_id)
            except Exception:
                logger.debug(
                    "Chatto: follow_thread failed for %s/%s",
                    chat_id,
                    thread_id,
                    exc_info=True,
                )

        # A later chunk failed after earlier ones went out: partial delivery.
        if last_error:
            logger.warning(
                "Chatto: sent %d/%d chunk(s) to %s before failing: %s",
                len(message_ids),
                len(chunks),
                chat_id,
                last_error,
            )

        # raw_response stays unset (dict-shaped per the SendResult contract):
        # gateway consumers such as the cron scheduler call .get() on it, so a
        # chattolib Message here would crash delivery bookkeeping *after* the
        # send already succeeded — the job then falls back to the standalone
        # path and the room sees the message twice.
        return SendResult(success=True, message_id=first_id)

    def format_message(self, content: str) -> str:
        """Normalise outgoing text for Chatto.

        Chatto renders Markdown natively, so there is nothing to escape or
        translate — the only transformations here are the ones that measurably
        render wrong: CRLF line endings (which show up as stray blank lines)
        and runs of more than two blank lines.

        BasePlatformAdapter override
        """
        if not content:
            return content
        normalised = content.replace("\r\n", "\n").replace("\r", "\n")
        while "\n\n\n\n" in normalised:
            normalised = normalised.replace("\n\n\n\n", "\n\n\n")
        return normalised

    async def edit_message(
        self,
        chat_id: str,
        message_id: str,
        content: str,
        *,
        finalize: bool = False,
    ) -> SendResult:
        """Edit a message we previously sent, via MessageService/UpdateMessage.

        The stream consumer drives streaming replies through this: without the
        override the base class reports "Not supported" and every incremental
        update arrives as a *new* message.

        ``finalize`` is a no-op for Chatto — an edit is an edit here, there is
        no in-progress card state to close out (hence no
        ``REQUIRES_EDIT_FINALIZE``).

        Content that exceeds the per-message limit is refused rather than
        silently truncated, so the caller falls back to ``send()``, which
        splits across messages.

        BasePlatformAdapter override
        """
        if not message_id:
            return SendResult(success=False, error="Chatto: no message id to edit")
        if not content:
            return SendResult(success=False, error="Empty message")

        formatted = self.format_message(content)
        if len(formatted) > ChattoConstants.MAX_MESSAGE_LENGTH:
            # Refuse instead of truncating: the caller's fallback path splits.
            return SendResult(
                success=False,
                error=(
                    f"Chatto: edit exceeds {ChattoConstants.MAX_MESSAGE_LENGTH} "
                    f"chars ({len(formatted)})"
                ),
            )

        try:
            client = await self._require_client()
        except RuntimeError:
            return SendResult(
                success=False, error="Chatto client not available", retryable=True
            )

        try:
            msg = await client.update_message(
                room_id=str(chat_id),
                event_id=str(message_id),
                body=formatted,
            )
        except ChattoError as e:
            logger.warning("Chatto: UpdateMessage failed for %s: %s", message_id, e)
            return SendResult(success=False, error=str(e), retryable=True)
        except Exception as e:
            logger.warning("Chatto: UpdateMessage error for %s: %s", message_id, e)
            return SendResult(success=False, error=str(e), retryable=False)

        # Our own edit comes back as a message_edited event; mark it seen so it
        # is never mistaken for inbound traffic.
        edited_id = getattr(msg, "id", "") or str(message_id)
        self._mark_seen(edited_id)
        return SendResult(success=True, message_id=edited_id)

    async def delete_message(self, chat_id: str, message_id: str) -> bool:
        """Delete a message via MessageService/DeleteMessage.

        Used by the stream consumer's fresh-final cleanup (removing a preview
        message once the completed reply has been sent) and by the ephemeral
        reply TTL.

        BasePlatformAdapter override
        """
        if not chat_id or not message_id:
            return False
        try:
            client = await self._require_client()
        except RuntimeError:
            logger.warning("Chatto: DeleteMessage — client unavailable")
            return False
        try:
            return bool(
                await client.delete_message(
                    room_id=str(chat_id),
                    event_id=str(message_id),
                )
            )
        except ChattoError as e:
            logger.warning("Chatto: DeleteMessage failed for %s: %s", message_id, e)
            return False
        except Exception as e:
            logger.warning("Chatto: DeleteMessage error for %s: %s", message_id, e)
            return False

    async def create_handoff_thread(
        self,
        parent_chat_id: str,
        name: str,
    ) -> str | None:
        """Anchor a session handoff in a fresh thread under *parent_chat_id*.

        Chatto threads hang off a message, not off the room, so we post a seed
        message and hand its ID back as the thread root — the same shape the
        Slack adapter uses.  DMs don't support threads, so they get ``None``
        and the watcher keeps delivering into the DM itself.

        BasePlatformAdapter override
        """
        if not parent_chat_id:
            return None
        if self._room_kinds.get(parent_chat_id) == RoomKind.DM:
            logger.debug("Chatto: handoff thread skipped — %s is a DM", parent_chat_id)
            return None

        try:
            client = await self._require_client()
        except RuntimeError:
            logger.warning("Chatto: handoff thread — client unavailable")
            return None

        seed_text = f"🧵 Hermes handoff — **{(name or 'session').strip()[:80]}**"
        try:
            msg = await client.post_message(room_id=str(parent_chat_id), body=seed_text)
        except Exception as e:
            logger.warning(
                "Chatto: handoff thread seed-post failed for room %s: %s",
                parent_chat_id,
                e,
            )
            return None

        seed_id = getattr(msg, "id", "") or ""
        if not seed_id:
            logger.warning("Chatto: handoff thread seed-post returned no message id")
            return None

        self._mark_seen(seed_id)
        self._our_message_ids.add(seed_id)
        self._our_thread_roots.add(seed_id)
        try:
            await client.follow_thread(str(parent_chat_id), seed_id)
        except Exception:
            logger.debug(
                "Chatto: follow_thread failed for handoff %s/%s",
                parent_chat_id,
                seed_id,
                exc_info=True,
            )
        return seed_id

    # Overridden from BaseAdapter:
    async def send_typing(self, chat_id: str, metadata=None) -> None:
        """Start a persistent typing indicator for a room.

        Sends a typing ping every 10 seconds (Chatto's indicator likely
        lasts ~8-10s).  The background loop runs until ``stop_typing()``
        is called or the task is cancelled.

        BasePlatformAdapter override
        """
        if chat_id in self._typing_tasks:
            return  # already running

        async def _typing_loop() -> None:
            try:
                while True:
                    try:
                        try:
                            client = await self._require_client()
                        except RuntimeError:
                            return
                        await client.update_typing_indicator(room_id=str(chat_id))
                    except asyncio.CancelledError:
                        return
                    except Exception:
                        logger.debug(
                            "Chatto: typing indicator refresh failed for %s",
                            chat_id,
                            exc_info=True,
                        )
                    await asyncio.sleep(10)
            except asyncio.CancelledError:
                pass
            finally:
                self._typing_tasks.pop(chat_id, None)

        self._typing_tasks[chat_id] = asyncio.create_task(_typing_loop())

    async def stop_typing(self, chat_id: str) -> None:
        """Stop the persistent typing indicator for a room.

        BasePlatformAdapter override
        """
        task = self._typing_tasks.pop(chat_id, None)
        if task:
            task.cancel()
            try:
                await task
            except (asyncio.CancelledError, Exception):
                logger.debug("Chatto: typing task ended for %s", chat_id, exc_info=True)

    async def get_chat_info(self, chat_id: str) -> dict[str, Any]:
        """Get information about a chat/room.

        BasePlatformAdapter override
        """
        name = self._room_names.get(chat_id, chat_id)
        kind = self._room_kinds.get(chat_id)
        return {
            "name": name,
            "type": chat_type_for_room_kind(kind).value,
        }

    # ------------------------------------------------------------------ #
    # Reactions
    # ------------------------------------------------------------------ #

    @staticmethod
    def _emoji_to_shortcode(emoji: str) -> str:
        """Convert a unicode emoji to a Chatto shortcode name.

        If the emoji is already a shortcode (no unicode mapping found),
        return it as-is.
        """
        shortcode = ChattoConstants.EMOJI_TO_SHORTCODE.get(emoji)
        if shortcode:
            return shortcode
        # Already a shortcode like "thumbsup" — return as-is
        return emoji

    async def add_reaction(self, room_id: str, message_id: str, emoji: str) -> bool:
        """Add a reaction to a message via MessageService/AddReaction."""
        shortcode = self._emoji_to_shortcode(emoji)
        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                logger.warning("Chatto: AddReaction — client unavailable")
                return False
            result = await client.add_reaction(
                room_id=room_id,
                message_event_id=message_id,
                emoji=shortcode,
            )
            return result
        except ChattoError as e:
            logger.warning("Chatto: AddReaction failed: %s", e)
            return False
        except Exception as e:
            logger.warning("Chatto: AddReaction error: %s", e)
            return False

    async def remove_reaction(self, chat_id: str, message_id: str, emoji: str) -> bool:
        """Remove a reaction from a message via MessageService/RemoveReaction."""
        shortcode = self._emoji_to_shortcode(emoji)
        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                logger.warning("Chatto: RemoveReaction — client unavailable")
                return False
            result = await client.remove_reaction(
                room_id=str(chat_id),
                message_event_id=str(message_id),
                emoji=shortcode,
            )
            return result
        except ChattoError as e:
            logger.warning("Chatto: RemoveReaction failed: %s", e)
            return False
        except Exception as e:
            logger.warning("Chatto: RemoveReaction error: %s", e)
            return False

    # ------------------------------------------------------------------ #
    # DM initiation (Chatto-unique)
    # ------------------------------------------------------------------ #

    async def start_dm(self, user_id: str) -> str | None:
        """Start a direct message with a user via RoomService/StartDM.

        Returns the room ID on success, or None on failure.
        """
        if not user_id:
            return None
        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                return None
            room = await client.start_dm(participant_ids=[str(user_id)])
            self._room_names[room.id] = room.name
            self._room_kinds[room.id] = room.kind
            return room.id
        except ChattoError as e:
            logger.debug("Chatto: StartDM failed: %s", e)
            return None
        except Exception as e:
            logger.debug("Chatto: StartDM error: %s", e)
            return None

    # ------------------------------------------------------------------ #
    # Room creation (Chatto-unique)
    # ------------------------------------------------------------------ #

    async def create_room(
        self,
        name: str,
        description: str = "",
        group_id: str = "",
        universal: bool = True,
    ) -> str | None:
        """Create an ad-hoc room via RoomService/CreateRoom.

        Returns the room ID on success, or None on failure.
        """
        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                return None
            room = await client.create_room(
                name=name,
                group_id=group_id or "",
                description=description,
                universal=universal,
            )
            rid = str(room.id) if room else ""
            if rid:
                self._room_names[rid] = room.name
                self._room_kinds[rid] = room.kind
                return rid
            logger.debug("Chatto: CreateRoom returned no room id")
            return None
        except ChattoError as e:
            logger.debug("Chatto: CreateRoom failed: %s", e)
            return None
        except Exception as e:
            logger.debug("Chatto: CreateRoom error: %s", e)
            return None

    # ------------------------------------------------------------------ #
    # Processing lifecycle hooks (reactions-based, like Discord)
    # ------------------------------------------------------------------ #

    def _event_room_and_message_id(self, event: MessageEvent) -> tuple[str, str]:
        """Extract room_id and message_id from a MessageEvent."""
        message_id = event.message_id or ""
        chat_id = event.source.chat_id
        return chat_id, message_id

    async def on_processing_start(self, event: MessageEvent) -> None:
        """Add an 👀 (eyes) reaction to the incoming message.

        BasePlatformAdapter override
        """
        if not self.chatto_config.reactions.value:
            return

        chat_id, message_id = self._event_room_and_message_id(event)
        if not chat_id or not message_id:
            # Routine, not a fault: the gateway runs agent-initiated turns
            # (heartbeat polls, goal continuations) through the same pipeline
            # with message_id=None, and there is no inbound message to mark.
            logger.debug(
                "Chatto: nothing to react to (chat_id=%r, message_id=%r)",
                chat_id,
                message_id,
            )
            return
        await self.add_reaction(chat_id, message_id, "👀")

    async def on_processing_complete(
        self,
        event: MessageEvent,
        outcome: ProcessingOutcome,
    ) -> None:
        """Swap the 👀 reaction for ✅ (success) or ❌ (failure).

        BasePlatformAdapter override
        """
        if not self.chatto_config.reactions.value:
            return
        chat_id, message_id = self._event_room_and_message_id(event)
        if not chat_id or not message_id:
            return
        # Remove the processing eyes reaction
        await self.remove_reaction(chat_id, message_id, "👀")
        # Add the outcome reaction
        if outcome == ProcessingOutcome.SUCCESS:
            await self.add_reaction(chat_id, message_id, "✅")
        elif outcome == ProcessingOutcome.FAILURE:
            await self.add_reaction(chat_id, message_id, "❌")
        elif outcome == ProcessingOutcome.CANCELLED:
            await self.add_reaction(chat_id, message_id, "🚫")

    # ------------------------------------------------------------------ #
    # Asset upload (chunked)
    # ------------------------------------------------------------------ #

    async def _upload_asset(self, room_id: str, file_path: str) -> str | None:
        """Upload a file via the chunked AssetUploadService.

        Returns the asset ID on success, or None on failure.
        """
        try:
            file_data = await asyncio.to_thread(_read_file_bytes, file_path)
        except Exception as e:
            logger.error("Chatto: failed to read file %s — %s", file_path, e)
            return None

        if not file_data:
            logger.error("Chatto: file %s is empty", file_path)
            return None

        file_size = len(file_data)
        file_name = os.path.basename(file_path)
        mime_type = mimetypes.guess_type(file_path)[0] or "application/octet-stream"
        sha256_hash = hashlib.sha256(file_data).hexdigest()

        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                logger.error("Chatto: upload aborted - no client available")
                return None
            # Step 1: Create upload session
            upload = await client.create_upload(
                room_id=room_id,
                filename=file_name,
                size=file_size,
                sha256=sha256_hash,
                content_type=mime_type,
            )
            # AssetUpload names this upload_id, not id — reading it through an
            # untyped getattr default is what let the mismatch reach production.
            upload_id = upload.upload_id
            if not upload_id:
                logger.error("Chatto: CreateUpload returned no upload ID")
                return None

            # Step 2: Upload chunks
            offset = 0
            while offset < file_size:
                chunk = file_data[offset : offset + ChattoConstants.UPLOAD_CHUNK_SIZE]
                chunk_sha256 = hashlib.sha256(chunk).hexdigest()
                await client.upload_chunk(
                    upload_id=upload_id,
                    offset=offset,
                    content=chunk,
                    chunk_sha256=chunk_sha256,
                )
                offset += len(chunk)

            # Step 3: Complete upload
            upload, asset = await client.complete_upload(upload_id=upload_id)
            if not asset:
                logger.error("Chatto: CompleteUpload returned no asset")
                return None

            asset_id = str(getattr(cast(Any, asset), "id", ""))
            logger.info(
                "Chatto: uploaded %s as asset %s (%d bytes)",
                file_name,
                asset_id,
                file_size,
            )
            return asset_id

        except ChattoError as e:
            logger.error("Chatto: upload failed: %s", e)
            return None
        except Exception as e:
            logger.error("Chatto: upload error: %s", e)
            return None

    async def _post_attachment_message(
        self,
        chat_id: str,
        asset_ids: list[str],
        caption: str | None,
        reply_to: str | None,
        metadata: dict[str, Any] | None,
    ) -> SendResult:
        """Post one message carrying already-uploaded assets."""
        thread_id = (metadata or {}).get("thread_id")
        if reply_to:
            thread_id = reply_to

        try:
            try:
                client = await self._require_client()
            except RuntimeError:
                return SendResult(
                    success=False, error="Chatto client not available", retryable=True
                )
            msg = await client.post_message(
                room_id=str(chat_id),
                body=self.format_message(caption) if caption else "",
                attachment_asset_ids=asset_ids,
                thread_root_event_id=str(thread_id) if thread_id else "",
            )
            self._mark_seen(msg.id)
            self._our_message_ids.add(msg.id)
            return SendResult(success=True, message_id=msg.id)
        except ChattoError as e:
            return SendResult(success=False, error=str(e), retryable=True)
        except Exception as e:
            return SendResult(success=False, error=str(e), retryable=False)

    async def _send_local_attachment(
        self,
        chat_id: str,
        file_path: str,
        caption: str | None,
        reply_to: str | None,
        metadata: dict[str, Any] | None,
        *,
        kind: str,
    ) -> SendResult:
        """Upload a local file and post it as a native Chatto attachment.

        Shared by ``send_image_file``/``send_document``/``send_video``/
        ``send_voice`` — the upload mechanics are identical, only the wording of
        the failure notice differs.  On failure we send that notice as text and
        never the host path (it leaks the Hermes home layout).
        """
        notice = f"⚠️ Couldn't deliver the {kind} attachment."

        safe_path = self.validate_media_delivery_path(file_path)
        if not safe_path:
            logger.warning(
                "[%s] send %s: unsafe path %s",
                self.name,
                kind,
                file_path,
            )
            text = f"{caption}\n{notice}" if caption else notice
            return await self.send(chat_id, text, reply_to=reply_to, metadata=metadata)

        asset_id = await self._upload_asset(str(chat_id), safe_path)
        if not asset_id:
            logger.warning(
                "[%s] send %s: upload failed for %s",
                self.name,
                kind,
                safe_path,
            )
            text = f"{caption}\n{notice}" if caption else notice
            return await self.send(chat_id, text, reply_to=reply_to, metadata=metadata)

        return await self._post_attachment_message(
            chat_id,
            [asset_id],
            caption,
            reply_to,
            metadata,
        )

    async def send_image_file(
        self,
        chat_id: str,
        image_path: str,
        caption: str | None = None,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs,
    ) -> SendResult:
        """Send a local image file via the chunked upload API.

        The parameter is ``image_path``, not ``file_path``: every caller passes
        it by keyword (``gateway/run.py:22354``, ``:22470``, and the base class's
        own ``send_multiple_images`` file:// branch), so a renamed parameter
        makes each of those raise TypeError and silently degrade to a text
        notice.

        BasePlatformAdapter override
        """
        return await self._send_local_attachment(
            chat_id,
            image_path,
            caption,
            reply_to,
            metadata,
            kind="image",
        )

    async def send_document(
        self,
        chat_id: str,
        file_path: str,
        caption: str | None = None,
        file_name: str | None = None,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs,
    ) -> SendResult:
        """Send a local file as a native Chatto attachment.

        ``file_name`` is the user-facing name the agent chose; Chatto takes the
        filename from the upload session, so it only matters for the failure
        notice.

        BasePlatformAdapter override
        """
        result = await self._send_local_attachment(
            chat_id,
            file_path,
            caption,
            reply_to,
            metadata,
            kind="file",
        )
        if not result.success and file_name:
            logger.debug("Chatto: document delivery failed for %s", file_name)
        return result

    async def send_video(
        self,
        chat_id: str,
        video_path: str,
        caption: str | None = None,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs,
    ) -> SendResult:
        """Send a local video as a native Chatto attachment.

        Chatto transcodes and plays it inline.

        BasePlatformAdapter override
        """
        return await self._send_local_attachment(
            chat_id,
            video_path,
            caption,
            reply_to,
            metadata,
            kind="video",
        )

    async def send_voice(
        self,
        chat_id: str,
        audio_path: str,
        caption: str | None = None,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
        **kwargs,
    ) -> SendResult:
        """Send a local audio file as a native Chatto attachment.

        Chatto has no dedicated voice-bubble type, so this is an ordinary audio
        attachment — still far better than the base class's text notice.

        BasePlatformAdapter override
        """
        return await self._send_local_attachment(
            chat_id,
            audio_path,
            caption,
            reply_to,
            metadata,
            kind="audio",
        )

    async def send_image(
        self,
        chat_id: str,
        image_url: str,
        caption: str | None = None,
        reply_to: str | None = None,
        metadata: dict[str, Any] | None = None,
    ) -> SendResult:
        """Send an image to a Chatto room.

        Tries to download the image from the URL and upload it as a native
        attachment.  Falls back to sending the URL as a link (Chatto renders
        link previews) if the download fails.

        BasePlatformAdapter override
        """
        # Try downloading and uploading as attachment
        try:
            import tempfile

            # Download to a temp file
            parsed = urlsplit(image_url)
            url_path = parsed.path
            ext = os.path.splitext(url_path)[1] or ".png"
            tmp_fd, tmp_path = tempfile.mkstemp(suffix=ext, prefix="chatto_img_")
            try:
                os.close(tmp_fd)
                await asyncio.to_thread(
                    _download_to_file,
                    image_url,
                    tmp_path,
                    ChattoConstants.HTTP_TIMEOUT,
                )

                # Upload as attachment
                result = await self.send_image_file(
                    chat_id,
                    tmp_path,
                    caption=caption,
                    reply_to=reply_to,
                    metadata=metadata,
                )
                if result.success:
                    return result
            finally:
                try:
                    os.unlink(tmp_path)
                except OSError:
                    pass
        except Exception as e:
            logger.debug(
                "Chatto: send_image download/upload failed, falling back to link: %s", e
            )

        # Fallback: send as link (Chatto renders link previews)
        text = image_url
        if caption:
            text = f"{caption}\n{image_url}"
        return await self.send(chat_id, text, reply_to=reply_to, metadata=metadata)

    async def _materialise_image(self, image_url: str) -> tuple[str | None, bool]:
        """Resolve one ``send_multiple_images`` entry to a local file path.

        Accepts ``http(s)://`` URLs (downloaded to a temp file), ``file://``
        URIs and bare paths.  Returns ``(path, is_temp)`` — the caller unlinks
        when ``is_temp``.  ``(None, False)`` means the entry is unusable.
        """
        import tempfile
        from urllib.parse import unquote as _unquote

        if image_url.startswith(("http://", "https://")):
            parsed = urlsplit(image_url)
            ext = os.path.splitext(parsed.path)[1] or ".png"
            tmp_fd, tmp_path = tempfile.mkstemp(suffix=ext, prefix="chatto_img_")
            os.close(tmp_fd)
            try:
                data = await self._download_attachment_bytes(image_url)
                await asyncio.to_thread(_write_file_bytes, tmp_path, data)
            except Exception as e:
                logger.warning("Chatto: image download failed for %s: %s", image_url, e)
                try:
                    os.unlink(tmp_path)
                except OSError:
                    pass
                return None, False
            return tmp_path, True

        local = image_url
        if local.startswith("file://"):
            local = _unquote(urlsplit(local).path)
        return self.validate_media_delivery_path(local), False

    async def send_multiple_images(
        self,
        chat_id: str,
        images: list[tuple[str, str]],
        metadata: dict[str, Any] | None = None,
        human_delay: float = 0.0,
    ) -> None:
        """Send a batch of images as ONE message with several attachments.

        The base implementation posts each image separately; a Chatto message
        carries a list of attachment assets, so a batch belongs in a single
        message (and a single notification).

        ``human_delay`` is ignored deliberately — there is only one outbound
        call to pace.  Entries that can't be fetched are dropped with a warning;
        if nothing survives, we fall back to the base class so the user still
        gets the links.

        BasePlatformAdapter override
        """
        if len(images or []) < 2:
            await super().send_multiple_images(
                chat_id,
                images,
                metadata=metadata,
                human_delay=human_delay,
            )
            return

        asset_ids: list[str] = []
        captions: list[str] = []
        for image_url, alt_text in images:
            path, is_temp = await self._materialise_image(image_url)
            if not path:
                logger.warning("Chatto: skipping unusable image %s", image_url)
                continue
            try:
                asset_id = await self._upload_asset(str(chat_id), path)
            finally:
                if is_temp:
                    try:
                        os.unlink(path)
                    except OSError:
                        pass
            if not asset_id:
                logger.warning("Chatto: upload failed for image %s", image_url)
                continue
            asset_ids.append(asset_id)
            if alt_text:
                captions.append(alt_text)

        if not asset_ids:
            logger.warning(
                "Chatto: no image survived upload, falling back to per-image delivery",
            )
            await super().send_multiple_images(
                chat_id,
                images,
                metadata=metadata,
                human_delay=human_delay,
            )
            return

        if len(asset_ids) < len(images):
            logger.warning(
                "Chatto: sending %d of %d images — the rest could not be uploaded",
                len(asset_ids),
                len(images),
            )

        await self._post_attachment_message(
            chat_id,
            asset_ids,
            "\n".join(captions) or None,
            None,
            metadata,
        )


# ---------------------------------------------------------------------------
# Cron / out-of-process delivery
# ---------------------------------------------------------------------------


async def hermes_standalone_sender_fn(
    pconfig: PlatformConfig,
    chat_id: str,
    message: str,
    *,
    thread_id=None,
    media_files=None,
    force_document=False,
) -> SendResult:
    """Deliver a message to Chatto without a running gateway adapter. Do not modify signature.

    Used by cron / scheduled routines that run out-of-process. Creates a
    short-lived chattolib client, posts, and closes.
    """
    chatto_config: ChattoConfiguration = ChattoConfiguration(pconfig=pconfig)

    # Create a temporary client for standalone sending — we need a base URL plus
    # either a token or a full login/password pair.
    has_credentials = bool(
        chatto_config.token.value
        or (chatto_config.login.value and chatto_config.password.value),
    )
    if not chatto_config.base_url.value or not has_credentials:
        return SendResult(
            success=False, error="Chatto: base URL or credentials missing"
        )

    client: ChattoClient
    try:
        if chatto_config.token.value:
            client = ChattoClient(
                base_url=chatto_config.base_url.value, token=chatto_config.token.value
            )
        else:
            client = await ChattoClient.login(
                base_url=chatto_config.base_url.value,
                login=chatto_config.login.value,
                password=chatto_config.password.value,
            )
    except Exception as exc:
        return SendResult(success=False, error=f"Chatto login failed: {exc}")

    try:
        kwargs: dict[str, Any] = {}
        if chatto_config.auto_thread.value and thread_id:
            kwargs["thread_root_event_id"] = thread_id
        if media_files and media_files.get("attachment_asset_ids"):
            kwargs["attachment_asset_ids"] = list(media_files["attachment_asset_ids"])
        try:
            posted = await client.post_message(chat_id, message, **kwargs)
        except Exception as exc:
            return SendResult(success=False, error=str(exc))
        return SendResult(success=True, message_id=posted.id)
    finally:
        try:
            await client.close()
        except Exception as exc:
            logger.error(
                "Chatto standalone: error closing short-lived client (perhaps already closed): %s",
                exc,
            )


def hermes_validate_config(config: PlatformConfig) -> bool:
    """Check whether Chatto Plugin is configured.

    Function name should be the same as register argument name with "hermes_" prefix, so we
    know that it is needed for plugin register(). Do not change signature.
    Takes ``config``. Compare to hermes_is_connected().
    """
    chatto_config = ChattoConfiguration(pconfig=config)

    if (
        len(chatto_config.allowed_users.value) > 0
        and chatto_config.allow_all_users.value
    ):
        logger.info(
            "Chatto: Conflicting configuration. Either use 'allowed_users' or 'allow_all_users' but not both."
        )
        return False

    if chatto_config.base_url.value:
        if (chatto_config.token.value is not None) or (
            chatto_config.login.value and chatto_config.password.value
        ):
            return True
        else:
            logger.error(
                "Chatto: Minimally, either token or login/password must be set."
            )
    else:
        logger.error("Chatto: base_url must be set.")

    return False


def hermes_check_fn() -> bool:
    """Report whether the vendored chattolib dependency can be imported."""
    try:
        from chattolib import (
            client,  # noqa: F401 — vendored dependency probe
        )

        return True
    except ImportError:
        return False


# ---------------------------------------------------------------------------
# is_connected probe
# ---------------------------------------------------------------------------


def hermes_is_connected(config: PlatformConfig) -> bool:
    """Check whether Chatto Plugin is connected. But where to: the Hermes Agent or the Chatto server.

    The Hermes Agent plugin docs suck and it seems there are many functions to do the same.
    """
    return bool(hermes_validate_config(config) and config.enabled)


def hermes_setup_fn() -> None:
    """Interactive setup wizard for Chatto. Is called by and only works in Hermes CLI context.

    Function name should be the same as register argument name with "hermes_" prefix, so we
    know that it is needed for plugin register().
    """
    from hermes_cli.setup import (
        print_success,
        prompt,
        prompt_yes_no,
        save_env_value,
    )

    url = prompt(
        "Chatto server URL (e.g. https://chat.example.com) or leave blank for default ChattoHQ on chat.chatto.run:"
    )
    if url:
        save_env_value(ChattoConfiguration.base_url.env_name, url)

    login = prompt("Chatto login (username):")
    if login:
        save_env_value(ChattoConfiguration.login.env_name, login)

    password = prompt("Chatto password:", password=True)
    if password:
        save_env_value(ChattoConfiguration.password.env_name, password)

    home = prompt("Home room ID for notifications (or empty):")
    if home:
        save_env_value(ChattoConfiguration.home_channel.env_name, home)

    allow_all = prompt_yes_no("Allow all users to talk? (true/false):")
    if allow_all:
        save_env_value(ChattoConfiguration.allow_all_users.env_name, str(allow_all))
    print_success("\n✓ Chatto configured. Restart the gateway to activate.")


def hermes_env_enablement_fn() -> dict | None:
    """Seed PlatformConfig.extra from env vars.

    Returns a dict compatible with the PlatformConfig merge hook (or None
    when no env-provided values are present).

    Called by the platform registry during load_gateway_config().
    Return None when the platform isn't minimally configured — the
    caller then skips auto-enabling. Return a dict to seed extras.

    The special 'home_channel' key is extracted and becomes a proper
    HomeChannel dataclass on the PlatformConfig; every other key is
    merged into PlatformConfig.extra.

    Function name should be the same as register argument name with "hermes_" prefix, so we
    know that it is needed for plugin register().
    """
    # Seed keys must be the config.yaml "extra" keys (config_key), NOT the env
    # var names — ChattoConfiguration reads extra[config_key].
    seed: dict[str, Any] = {
        ChattoConfiguration.base_url.field_name: (
            os.getenv(ChattoConfiguration.base_url.env_name)
            or ChattoClient.DEFAULT_BASE_URL
        ).strip(),
    }

    for field in ChattoConfiguration.fields():
        if field.field_name == ChattoConfiguration.base_url.field_name:
            continue
        env_value = os.getenv(field.env_name)
        if env_value:
            seed[field.config_key] = env_value.strip()

    logger.debug(
        "seed: %s", {k: v for k, v in seed.items() if k not in ("token", "password")}
    )

    return seed


# ---------------------------------------------------------------------------
# Plugin registration entry point
# ---------------------------------------------------------------------------

# What each capability is called in the startup banner, keyed by the method
# that implements it. Derived from real overrides rather than hard-coded, so
# dropping a method drops its claim from the log instead of leaving a lie.
_CAPABILITY_LABELS = {
    "send": "text",
    "send_image_file": "images",
    "send_multiple_images": "image batches (bundled into one message)",
    "send_video": "video",
    "send_voice": "voice messages",
    "send_document": "documents",
    "add_reaction": "reactions",
    "edit_message": "message editing",
    "delete_message": "message deletion",
    "send_typing": "typing indicators",
    "create_handoff_thread": "threads",
    "start_dm": "direct messages",
    "create_room": "room creation",
}


def _capabilities() -> list[str]:
    """Name the things this adapter genuinely implements itself.

    A capability counts only when ChattoAdapter overrides the base method —
    inheriting BasePlatformAdapter's fallback means the feature is not
    natively supported, and announcing it would mislead.
    """
    found = [
        label
        for name, label in _CAPABILITY_LABELS.items()
        if getattr(ChattoAdapter, name, None)
        is not getattr(BasePlatformAdapter, name, None)
    ]
    if ChattoAdapter.supports_code_blocks:
        found.append("code blocks")
    if ChattoAdapter.supports_status_text:
        found.append("custom status text")
    found.append("presence (refreshed while connected)")
    return found


def register(ctx) -> None:
    """Plugin entry point — called by the Hermes plugin system."""
    logger.info("Registering Chatto platform plugin on Hermes Agent")

    for capability in _capabilities():
        logger.info("Chatto capability: %s", capability)

    logger.info(
        "ChattoConfiguration.allowed_users.env_name: %s",
        ChattoConfiguration.allowed_users.env_name,
    )

    ctx.register_platform(
        name=ChattoConstants.PLATFORM_NAME,  # this will be the config.yaml key.
        label=ChattoConstants.PLATFORM_LABEL,
        adapter_factory=hermes_adapter_factory,
        check_fn=hermes_check_fn,
        validate_config=hermes_validate_config,
        is_connected=hermes_is_connected,
        install_hint=ChattoConstants.INSTALL_HINT,
        env_enablement_fn=hermes_env_enablement_fn,
        setup_fn=hermes_setup_fn,
        cron_deliver_env_var=ChattoConfiguration.home_channel.env_name,
        standalone_sender_fn=hermes_standalone_sender_fn,
        allowed_users_env=ChattoConfiguration.allowed_users.env_name,
        allow_all_env=ChattoConfiguration.allow_all_users.env_name,
        max_message_length=ChattoConstants.MAX_MESSAGE_LENGTH,
        emoji="😺",
        allow_update_command=True,
        pii_safe=False,
        platform_hint=(
            "Using the 'Hermes Chatto Platform Plugin' you connect to a Chatto server. "
            "Authorized admins and users will contact you and call you his Hermes Agent. They are "
            "natural persons and thus responsible for what they do in terms of rights. You compute "
            "on their behalf. They _may_ address you by @-mentioning your name. If configured, "
            "you also react without a @-mention. Direct messages reach you without a mention."
            "Keep responses conversational. Markdown is supported. "
            "Include MEDIA:/absolute/path/to/file in your response to refer to our local files. Images "
            "(.png, .jpg, .gif, .webp) arrive as inline pictures, videos (.mp4, .mov, .webm) as "
            "video attachments, audio as a voice bubble, anything else as a downloadable document. "
            "Do NOT use markdown image syntax for local files. Local files always go through MEDIA:. "
            "Several images in one response are bundled into a single message. "
        ),
    )