diff --git a/addons/im_livechat/static/src/core/web/discuss_sidebar_categories_livechat.js b/addons/im_livechat/static/src/core/web/discuss_sidebar_categories_livechat.js
index 4233cba978f..6f8c0c0a09e 100644
--- a/addons/im_livechat/static/src/core/web/discuss_sidebar_categories_livechat.js
+++ b/addons/im_livechat/static/src/core/web/discuss_sidebar_categories_livechat.js
@@ -5,7 +5,10 @@ import { discussSidebarCategoriesRegistry } from "@mail/discuss/core/web/discuss
 discussSidebarCategoriesRegistry.add(
     "livechats",
     {
-        predicate: (store) => store.discuss.livechat.threads.some((thread) => thread?.is_pinned),
+        predicate: (store) =>
+            store.discuss.livechat.threads.some(
+                (thread) => thread.displayToSelf || thread.isLocallyPinned
+            ),
         value: (store) => store.discuss.livechat,
     },
     { sequence: 20 }
diff --git a/addons/im_livechat/static/tests/sidebar_patch_tests.js b/addons/im_livechat/static/tests/sidebar_patch_tests.js
index 7b546c7cebd..5e191098279 100644
--- a/addons/im_livechat/static/tests/sidebar_patch_tests.js
+++ b/addons/im_livechat/static/tests/sidebar_patch_tests.js
@@ -7,7 +7,7 @@ import { start } from "@mail/../tests/helpers/test_utils";
 
 import { url } from "@web/core/utils/urls";
 import { nextTick } from "@web/../tests/helpers/utils";
-import { click, contains } from "@web/../tests/utils";
+import { click, contains, insertText } from "@web/../tests/utils";
 
 QUnit.module("discuss sidebar (patch)");
 
@@ -472,3 +472,35 @@ QUnit.test("Message unread counter", async () => {
     );
     await contains(".o-mail-DiscussSidebarChannel .badge", { text: "1" });
 });
+
+QUnit.test("unknown livechat can be displayed and interacted with", async () => {
+    const pyEnv = await startServer();
+    const partnerId = pyEnv["res.partner"].create({ name: "Jane" });
+    const channelId = pyEnv["discuss.channel"].create({
+        channel_member_ids: [[0, 0, { partner_id: partnerId }]],
+        channel_type: "livechat",
+        livechat_operator_id: partnerId,
+    });
+    const { openDiscuss } = await start();
+    await openDiscuss();
+    await contains("button.o-active", { text: "Inbox" });
+    await contains(".o-mail-DiscussSidebarCategory-livechat", { count: 0 });
+    await contains(".o-mail-DiscussSidebarChannel", { count: 0 });
+    await openDiscuss(channelId);
+    await contains(
+        ".o-mail-DiscussSidebarCategory-livechat + .o-mail-DiscussSidebarChannel.o-active",
+        {
+            text: "Jane",
+        }
+    );
+    await insertText(".o-mail-Composer-input", "Hello", { replace: true });
+    await click(".o-mail-Composer-send:enabled");
+    await contains(".o-mail-Message", { text: "Hello" });
+    await click("button", { text: "Inbox" });
+    await contains(".o-mail-DiscussSidebarChannel:not(.o-active)", { text: "Jane" });
+    await click("div[title='Unpin Conversation']", {
+        parent: [".o-mail-DiscussSidebarChannel", { text: "Jane" }],
+    });
+    await contains(".o-mail-DiscussSidebarCategory-livechat", { count: 0 });
+    await contains(".o-mail-DiscussSidebarChannel", { count: 0 });
+});
diff --git a/addons/mail/models/discuss/discuss_channel.py b/addons/mail/models/discuss/discuss_channel.py
index 426599b35d5..9a8d88ce6b6 100644
--- a/addons/mail/models/discuss/discuss_channel.py
+++ b/addons/mail/models/discuss/discuss_channel.py
@@ -539,7 +539,7 @@ class Channel(models.Model):
         # Last interest and is_pinned are updated for a channel when posting a message.
         # So a notification is needed to update UI, and it should come before the
         # notification of the message itself to ensure the channel automatically opens.
-        payload = {"id": self.id, "isServerPinned": True, "last_interest_dt": fields.Datetime.now()}
+        payload = {"id": self.id, "is_pinned": True, "last_interest_dt": fields.Datetime.now()}
         bus_notifications = [
             (self, "discuss.channel/last_interest_dt_changed", payload),
             (self, "discuss.channel/new_message", {"id": self.id, "message": message_format}),
diff --git a/addons/mail/static/src/core/common/thread_model.js b/addons/mail/static/src/core/common/thread_model.js
index f9e46e2cce0..edccebaa061 100644
--- a/addons/mail/static/src/core/common/thread_model.js
+++ b/addons/mail/static/src/core/common/thread_model.js
@@ -279,6 +279,8 @@ export class Thread extends Record {
     custom_notifications = false;
     /** @type {String} */
     mute_until_dt;
+    /** @type {Boolean} */
+    isLocallyPinned = false;
 
     get accessRestrictedToGroupText() {
         if (!this.authorizedGroupFullName) {
diff --git a/addons/mail/static/src/core/common/thread_service.js b/addons/mail/static/src/core/common/thread_service.js
index 56ee60be5e6..e6d9aef1eee 100644
--- a/addons/mail/static/src/core/common/thread_service.js
+++ b/addons/mail/static/src/core/common/thread_service.js
@@ -403,15 +403,15 @@ export class ThreadService {
     }
 
     async unpin(thread) {
+        thread.isLocallyPinned = false;
         if (thread.eq(this.store.discuss.thread)) {
             this.router.replaceState({ active_id: undefined });
         }
-        if (thread.model !== "discuss.channel") {
-            return;
+        if (thread.model === "discuss.channel" && thread.is_pinned) {
+            return this.orm.silent.call("discuss.channel", "channel_pin", [thread.id], {
+                pinned: false,
+            });
         }
-        return this.orm.silent.call("discuss.channel", "channel_pin", [thread.id], {
-            pinned: false,
-        });
     }
 
     pin(thread) {
@@ -642,6 +642,9 @@ export class ThreadService {
         if (pushState) {
             this.router.pushState({ active_id: activeId });
         }
+        if (!thread.is_pinned) {
+            thread.isLocallyPinned = true;
+        }
     }
 
     /**
diff --git a/addons/mail/static/src/core/web/discuss_client_action.js b/addons/mail/static/src/core/web/discuss_client_action.js
index 16cdb6e6302..1f3c1c0d24a 100644
--- a/addons/mail/static/src/core/web/discuss_client_action.js
+++ b/addons/mail/static/src/core/web/discuss_client_action.js
@@ -53,18 +53,12 @@ export class DiscussClientAction extends Component {
             // legacy format (sent in old emails, shared links, ...)
             model = "discuss.channel";
         }
-        const activeThread = this.store.Thread.get({ model, id });
-        if (!activeThread || activeThread.notEq(this.store.discuss.thread)) {
-            const thread =
-                this.store.Thread.get({ model, id }) ??
-                (await this.threadService.fetchChannel(parseInt(id)));
-            if (!thread) {
-                return;
-            }
-            if (!thread.is_pinned) {
-                await this.threadService.pin(thread);
-            }
-            this.threadService.setDiscussThread(thread);
+        let activeThread = this.store.Thread.get({ model, id });
+        if (!activeThread?.type && model === "discuss.channel") {
+            activeThread = await this.threadService.fetchChannel(parseInt(id));
+        }
+        if (activeThread && activeThread.notEq(this.store.discuss.thread)) {
+            this.threadService.setDiscussThread(activeThread);
         }
     }
 }
diff --git a/addons/mail/static/src/discuss/core/common/discuss_core_common_service.js b/addons/mail/static/src/discuss/core/common/discuss_core_common_service.js
index 6c4ef563c52..ae85a224cf0 100644
--- a/addons/mail/static/src/discuss/core/common/discuss_core_common_service.js
+++ b/addons/mail/static/src/discuss/core/common/discuss_core_common_service.js
@@ -51,11 +51,7 @@ export class DiscussCoreCommon {
                 }
             });
             this.busService.subscribe("discuss.channel/last_interest_dt_changed", (payload) => {
-                const { id, last_interest_dt } = payload;
-                const channel = this.store.Thread.get({ model: "discuss.channel", id });
-                if (channel) {
-                    channel.last_interest_dt = last_interest_dt;
-                }
+                this.store.Thread.insert({ model: "discuss.channel", ...payload });
             });
             this.busService.subscribe("discuss.channel/leave", (payload) => {
                 const thread = this.store.Thread.insert({
@@ -252,9 +248,6 @@ export class DiscussCoreCommon {
                 return;
             }
         }
-        if (!channel.is_pinned) {
-            this.threadService.pin(channel);
-        }
         this.store.Message.get(messageData.temporary_id)?.delete();
         messageData.temporary_id = null;
         const message = this.store.Message.insert(messageData, { html: true });
diff --git a/addons/mail/static/src/discuss/core/web/discuss_sidebar_categories.js b/addons/mail/static/src/discuss/core/web/discuss_sidebar_categories.js
index e10546ba2c2..3c863dc5c14 100644
--- a/addons/mail/static/src/discuss/core/web/discuss_sidebar_categories.js
+++ b/addons/mail/static/src/discuss/core/web/discuss_sidebar_categories.js
@@ -84,7 +84,7 @@ export class DiscussSidebarCategories extends Component {
     filteredThreads(category) {
         return category.threads.filter((thread) => {
             return (
-                thread.displayToSelf &&
+                (thread.displayToSelf || thread.isLocallyPinned) &&
                 (!this.state.quickSearchVal ||
                     cleanTerm(thread.name).includes(cleanTerm(this.state.quickSearchVal)))
             );
diff --git a/addons/mail/static/tests/discuss/core/web/sidebar_tests.js b/addons/mail/static/tests/discuss/core/web/sidebar_tests.js
index 3f89ac5c154..db3628ef1d9 100644
--- a/addons/mail/static/tests/discuss/core/web/sidebar_tests.js
+++ b/addons/mail/static/tests/discuss/core/web/sidebar_tests.js
@@ -55,3 +55,33 @@ QUnit.test(
         await contains(".o-mail-NavigableList-item", { text: "Create: # test" });
     }
 );
+
+QUnit.test("unknown channel can be displayed and interacted with", async () => {
+    const pyEnv = await startServer();
+    const partnerId = pyEnv["res.partner"].create({ name: "Jane" });
+    const channelId = pyEnv["discuss.channel"].create({
+        channel_member_ids: [[0, 0, { partner_id: partnerId }]],
+        channel_type: "channel",
+        name: "Not So Secret",
+    });
+    const { openDiscuss } = await start();
+    await openDiscuss();
+    await contains("button.o-active", { text: "Inbox" });
+    await contains(".o-mail-DiscussSidebarChannel", { count: 0 });
+    await openDiscuss(channelId);
+    await contains(
+        ".o-mail-DiscussSidebarCategory-channel + .o-mail-DiscussSidebarChannel.o-active",
+        {
+            text: "Not So Secret",
+        }
+    );
+    await insertText(".o-mail-Composer-input", "Hello", { replace: true });
+    await click(".o-mail-Composer-send:enabled");
+    await contains(".o-mail-Message", { text: "Hello" });
+    await click("button", { text: "Inbox" });
+    await contains(".o-mail-DiscussSidebarChannel:not(.o-active)", { text: "Not So Secret" });
+    await click("div[title='Leave this channel']", {
+        parent: [".o-mail-DiscussSidebarChannel", { text: "Not So Secret" }],
+    });
+    await contains(".o-mail-DiscussSidebarChannel", { count: 0 });
+});
diff --git a/addons/mail/static/tests/helpers/mock_server/models/discuss_channel.js b/addons/mail/static/tests/helpers/mock_server/models/discuss_channel.js
index a4a28795533..a8a563b756b 100644
--- a/addons/mail/static/tests/helpers/mock_server/models/discuss_channel.js
+++ b/addons/mail/static/tests/helpers/mock_server/models/discuss_channel.js
@@ -204,18 +204,13 @@ patch(MockServer.prototype, {
     _mockDiscussChannelMessagePost(id, kwargs, context) {
         const message_type = kwargs.message_type || "notification";
         const channel = this.getRecords("discuss.channel", [["id", "=", id]])[0];
-        if (channel.channel_type !== "channel") {
-            const memberOfCurrentUser = this._mockDiscussChannelMember__getAsSudoFromContext(
-                channel.id
-            );
-            if (memberOfCurrentUser) {
-                this.pyEnv["discuss.channel.member"].write([memberOfCurrentUser.id], {
-                    last_interest_dt: serializeDateTime(today()),
-
-                    is_pinned: true,
-                });
-            }
-        }
+        const members = this.pyEnv["discuss.channel.member"].search([
+            ["channel_id", "=", channel.id],
+        ]);
+        this.pyEnv["discuss.channel.member"].write(members, {
+            last_interest_dt: serializeDateTime(today()),
+            is_pinned: true,
+        });
         const messageData = this._mockMailThreadMessagePost(
             "discuss.channel",
             [id],
diff --git a/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js b/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
index 671efb90e05..00ffafc4051 100644
--- a/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
+++ b/addons/mail/static/tests/helpers/mock_server/models/mail_thread.js
@@ -286,34 +286,18 @@ patch(MockServer.prototype, {
         const messageFormat = this._mockMailMessageMessageFormat([messageId])[0];
         const notifications = [];
         if (model === "discuss.channel") {
-            // members
             const channels = this.getRecords("discuss.channel", [["id", "=", message.res_id]]);
             for (const channel of channels) {
-                // notify update of last_interest_dt
                 const now = serializeDateTime(today());
-                const members = this.getRecords("discuss.channel.member", [
-                    ["id", "in", channel.channel_member_ids],
+                notifications.push([
+                    channel,
+                    "discuss.channel/last_interest_dt_changed",
+                    {
+                        id: channel.id,
+                        is_pinned: true,
+                        last_interest_dt: now,
+                    },
                 ]);
-                this.pyEnv["discuss.channel.member"].write(
-                    members.map((member) => member.id),
-                    { last_interest_dt: now }
-                );
-                for (const member of members) {
-                    const target = member.guest_id
-                        ? this.pyEnv["mail.guest"].searchRead([["id", "=", member.guest_id]])[0]
-                        : this.pyEnv["res.partner"].searchRead([["id", "=", member.partner_id]], {
-                              context: { active_test: false },
-                          })[0];
-                    notifications.push([
-                        target,
-                        "discuss.channel/last_interest_dt_changed",
-                        {
-                            id: channel.id,
-                            isServerPinned: member.is_pinned,
-                            last_interest_dt: member.last_interest_dt,
-                        },
-                    ]);
-                }
                 notifications.push([
                     channel,
                     "discuss.channel/new_message",