diff --git a/libervia/backend/plugins/plugin_xep_0461.py b/libervia/backend/plugins/plugin_xep_0461.py
new file mode 100644
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+++ b/libervia/backend/plugins/plugin_xep_0461.py
@@ -0,0 +1,241 @@
+#!/usr/bin/env python3
+
+# Libervia plugin for Extended Channel Search (XEP-0461)
+# Copyright (C) 2009-2025 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import TYPE_CHECKING, Any, Final, Self, cast
+from pydantic import BaseModel, Field
+from twisted.internet import defer
+from twisted.words.protocols.jabber import jid
+from twisted.words.protocols.jabber.xmlstream import XMPPHandler
+from twisted.words.xish import domish
+from wokkel import disco, iwokkel
+from zope.interface import implementer
+from libervia.backend import G
+from libervia.backend.core import exceptions
+from libervia.backend.core.constants import Const as C
+from libervia.backend.core.core_types import SatXMPPEntity
+from libervia.backend.core.i18n import _
+from libervia.backend.core.log import getLogger
+from libervia.backend.memory.sqla import Storage
+from libervia.backend.memory.sqla_mapping import History
+from libervia.backend.models.core import MessageData
+from libervia.backend.models.types import JIDType
+from libervia.backend.tools.utils import ensure_deferred
+
+if TYPE_CHECKING:
+    from libervia.backend.core.main import LiberviaBackend
+
+log = getLogger(__name__)
+
+
+PLUGIN_INFO = {
+    C.PI_NAME: "Message Replies",
+    C.PI_IMPORT_NAME: "XEP-0461",
+    C.PI_TYPE: "XEP",
+    C.PI_MODES: C.PLUG_MODE_BOTH,
+    C.PI_DEPENDENCIES: [],
+    C.PI_RECOMMENDATIONS: [],
+    C.PI_MAIN: "XEP_0461",
+    C.PI_HANDLER: "yes",
+    C.PI_DESCRIPTION: _("Message replies support."),
+}
+
+NS_REPLY = "urn:xmpp:reply:0"
+host: "LiberviaBackend | None" = None
+
+
+class ReplyTo(BaseModel):
+    to: JIDType | None = None
+    id: str
+    internal_uid: bool = Field(
+        default=True,
+        description="True if the id is a message UID, i.e. Libervia internal ID of "
+        "message, otherwise it's an XMPP stanza ID or origin ID as specified in the XEP"
+    )
+
+    async def ensure_xmpp_id(self, client: SatXMPPEntity) -> None:
+        if not self.internal_uid:
+            return
+        history = await G.storage.get(
+            client,
+            History,
+            History.uid,
+            self.id,
+        )
+
+        if history.uid != self.id:
+            raise exceptions.InternalError(
+                f"Inconsistency between given history UID {history.uid!r} and ReplyTo "
+                f"id ({self.id!r})."
+            )
+        if history.type == C.MESS_TYPE_GROUPCHAT:
+            self.id = history.stanza_id
+        else:
+            self.id = history.origin_id
+        assert self.id
+        self.internal_uid = False
+
+    @classmethod
+    def from_element(cls, reply_elt: domish.Element) -> Self:
+        """Create a ReplyTo instance from a <reply> element or its parent.
+
+        @param reply_elt: The <reply> element or a parent element.
+        @return: ReplyTo instance.
+        @raise exceptions.NotFound: If the <reply> element is not found.
+        """
+        if reply_elt.uri != NS_REPLY or reply_elt.name != "reply":
+            child_file_metadata_elt = next(reply_elt.elements(NS_REPLY, "reply"), None)
+            if child_file_metadata_elt is None:
+                raise exceptions.NotFound("<reply> element not found")
+            else:
+                reply_elt = child_file_metadata_elt
+
+        try:
+            message_id = reply_elt["id"]
+        except KeyError:
+            raise exceptions.DataError('Missing "id" attribute.')
+
+        return cls(to=reply_elt.getAttribute("to"), id=message_id, internal_uid=False)
+
+    def to_element(self) -> domish.Element:
+        """Build the <reply> element from this instance's data.
+
+        @return: <reply> element.
+        """
+        if self.internal_uid:
+            raise exceptions.DataError(
+                '"id" must be converted to XMPP id before calling "to_element". Please '
+                '"use ensure_xmpp_id" first.')
+        reply_elt = domish.Element((NS_REPLY, "reply"), attribs={"id": self.id})
+        if self.to is not None:
+            reply_elt["to"] = self.to.full()
+        return reply_elt
+
+
+class XEP_0461:
+    """Implementation of XEP-0461 Message Replies."""
+
+    namespace: Final[str] = NS_REPLY
+
+    def __init__(self, host: Any):
+        log.info(f"Plugin {PLUGIN_INFO[C.PI_NAME]!r} initialization.")
+        self.host = host
+        host.register_namespace("reply", NS_REPLY)
+        host.trigger.add("message_received", self._message_received_trigger)
+        host.trigger.add("sendMessage", self._sendMessage_trigger)
+
+    def get_handler(self, client):
+        return XEP_0461_handler()
+
+    async def _parse_reply(
+        self, client: SatXMPPEntity, message_elt: domish.Element, mess_data: MessageData
+    ) -> MessageData:
+        try:
+            reply_to = ReplyTo.from_element(message_elt)
+        except exceptions.NotFound:
+            pass
+        else:
+            try:
+                thread_id = mess_data["extra"]["thread"]
+            except KeyError:
+                pass
+            else:
+                message_type = message_elt.getAttribute("type")
+                storage = G.storage
+                history = await storage.get_history_from_xmpp_id(
+                    client, reply_to.id, message_type
+                )
+                if history is None:
+                    log.warning(f"Received a <reply> to an unknown message: {reply_to!r}")
+                else:
+                    if not history.thread:
+                        await storage.add_thread(
+                            history.uid, thread_id, None, is_retroactive=True
+                        )
+                    # We can to use internal UID to make frontends life easier.
+                    reply_to.id = history.uid
+                    reply_to.internal_uid = True
+            # FIXME: We use mode=json to have a serialisable data in storage. When
+            #  Pydantic models are fully integrated with MessageData and storage, the
+            #  ReplyTo model should be used directly here instead.
+            mess_data["extra"]["reply"] = reply_to.model_dump(mode="json")
+        return mess_data
+
+    def _message_received_trigger(
+        self,
+        client: SatXMPPEntity,
+        message_elt: domish.Element,
+        post_treat: defer.Deferred,
+    ) -> bool:
+        post_treat.addCallback(
+            lambda mess_data: defer.ensureDeferred(
+                self._parse_reply(client, message_elt, mess_data)
+            )
+        )
+        return True
+
+    @ensure_deferred
+    async def _add_reply_to_elt(self, mess_data: MessageData, client: SatXMPPEntity) -> MessageData:
+        try:
+            # FIXME: Once MessageData is fully moved to Pydantic, we should have directly
+            #   the ReplyTo instance here.
+            reply_to = ReplyTo(**mess_data["extra"]["reply"])
+        except KeyError:
+            log.error('"_add_reply_to_elt" should not be called when there is no reply.')
+        else:
+            await reply_to.ensure_xmpp_id(client)
+            message_elt: domish.Element = mess_data["xml"]
+            message_elt.addChild(reply_to.to_element())
+
+        return mess_data
+
+    def _sendMessage_trigger(
+        self,
+        client: SatXMPPEntity,
+        mess_data: MessageData,
+        pre_xml_treatments: defer.Deferred,
+        post_xml_treatments: defer.Deferred,
+    ) -> bool:
+        try:
+            extra = mess_data["extra"]
+            reply_to = ReplyTo(**extra["reply"])
+        except KeyError:
+            pass
+        else:
+            if "thread" not in extra:
+                # FIXME: once MessageData is fully moved to Pydantic, ReplyTo should be
+                #   used directly here instead of a dump.
+                extra["reply"] = reply_to.model_dump(mode="json")
+                # We use parent message ID as thread ID.
+                extra["thread"] = reply_to.id
+
+            post_xml_treatments.addCallback(self._add_reply_to_elt, client)
+        return True
+
+
+@implementer(iwokkel.IDisco)
+class XEP_0461_handler(XMPPHandler):
+
+    def getDiscoInfo(
+        self, requestor: jid.JID, target: jid.JID, nodeIdentifier: str = ""
+    ) -> list[disco.DiscoFeature]:
+        return [disco.DiscoFeature(NS_REPLY)]
+
+    def getDiscoItems(
+        self, requestor: jid.JID, target: jid.JID, nodeIdentifier: str = ""
+    ) -> list[disco.DiscoItems]:
+        return []