MM-57326: [Shared Channels] Message priority, acknowledgement and persistent notifications need to be synced (#30736)

server/channels/api4/shared_channel_metadata_test.go

@@ -0,0 +1,659 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package api4
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/v8/platform/services/remotecluster"
+	"github.com/mattermost/mattermost/server/v8/platform/services/sharedchannel"
+)
+
+// setupTestEnvironment sets up a common test environment for shared channel metadata tests
+func setupTestEnvironment(t *testing.T) (*TestHelper, *sharedchannel.Service) {
+	th := setupForSharedChannels(t).InitBasic()
+	ss := th.App.Srv().Store()
+	EnsureCleanState(t, th, ss)
+
+	// Set license with all enterprise features
+	license := model.NewTestLicense()
+	license.SkuShortName = model.LicenseShortSkuEnterprise
+	th.App.Srv().SetLicense(license)
+
+	// Enable post priorities and persistent notifications
+	th.App.UpdateConfig(func(cfg *model.Config) {
+		*cfg.ServiceSettings.PostPriority = true
+		*cfg.ServiceSettings.AllowPersistentNotifications = true
+		*cfg.ServiceSettings.AllowPersistentNotificationsForGuests = true
+		*cfg.ServiceSettings.PersistentNotificationMaxRecipients = 100
+	})
+
+	// Verify license and settings
+	require.NotNil(t, th.App.Srv().License(), "License should be active")
+	postPriorityEnabled := *th.App.Config().ServiceSettings.PostPriority
+	require.True(t, postPriorityEnabled, "Post priorities should be enabled")
+
+	// Get the shared channel service and cast to concrete type
+	scsInterface := th.App.Srv().GetSharedChannelSyncService()
+	service, ok := scsInterface.(*sharedchannel.Service)
+	require.True(t, ok, "Expected sharedchannel.Service concrete type")
+	require.True(t, service.Active(), "SharedChannel service should be active")
+
+	// Ensure services are running
+	err := service.Start()
+	require.NoError(t, err)
+
+	rcService := th.App.Srv().GetRemoteClusterService()
+	if rcService != nil {
+		_ = rcService.Start()
+		if rc, ok := rcService.(*remotecluster.Service); ok {
+			rc.SetActive(true)
+		}
+		require.True(t, rcService.Active(), "RemoteClusterService should be active")
+	}
+
+	return th, service
+}
+
+// createSharedChannelSetup creates a shared channel with remote cluster for testing
+func createSharedChannelSetup(t *testing.T, th *TestHelper, service *sharedchannel.Service, testServer *httptest.Server) (*model.Channel, *model.RemoteCluster) {
+	// Create remote cluster
+	selfCluster := &model.RemoteCluster{
+		RemoteId:    model.NewId(),
+		Name:        "test-cluster-" + model.NewId()[:8],
+		SiteURL:     testServer.URL,
+		CreateAt:    model.GetMillis(),
+		LastPingAt:  model.GetMillis(),
+		Token:       model.NewId(),
+		CreatorId:   th.BasicUser.Id,
+		RemoteToken: model.NewId(),
+	}
+	var err error
+	selfCluster, err = th.App.Srv().Store().RemoteCluster().Save(selfCluster)
+	require.NoError(t, err)
+
+	// Create channel with users
+	testChannel := th.CreatePublicChannel()
+	_, appErr := th.App.AddUserToChannel(th.Context, th.BasicUser, testChannel, false)
+	require.Nil(t, appErr)
+	_, appErr = th.App.AddUserToChannel(th.Context, th.BasicUser2, testChannel, false)
+	require.Nil(t, appErr)
+
+	// Create shared channel
+	sc := &model.SharedChannel{
+		ChannelId: testChannel.Id,
+		TeamId:    testChannel.TeamId,
+		Home:      true,
+		ShareName: "test_sync_" + model.NewId()[:8],
+		CreatorId: th.BasicUser.Id,
+		RemoteId:  selfCluster.RemoteId,
+	}
+	sc, err = th.App.ShareChannel(th.Context, sc)
+	require.NoError(t, err)
+
+	// Create shared channel remote
+	scr := &model.SharedChannelRemote{
+		Id:                model.NewId(),
+		ChannelId:         sc.ChannelId,
+		CreatorId:         sc.CreatorId,
+		IsInviteAccepted:  true,
+		IsInviteConfirmed: true,
+		RemoteId:          sc.RemoteId,
+	}
+	_, err = th.App.SaveSharedChannelRemote(scr)
+	require.NoError(t, err)
+
+	return testChannel, selfCluster
+}
+
+func TestSharedChannelPostMetadataSync(t *testing.T) {
+	th, service := setupTestEnvironment(t)
+	defer th.TearDown()
+
+	t.Run("Post Priority Metadata Self-Referential Sync", func(t *testing.T) {
+		var syncedPosts []*model.Post
+
+		// Create test HTTP server using self-referential approach
+		testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServer.Close()
+
+		testChannel, selfCluster := createSharedChannelSetup(t, th, service, testServer)
+
+		// Initialize sync handler
+		syncHandler := NewSelfReferentialSyncHandler(t, service, selfCluster)
+		syncHandler.OnPostSync = func(post *model.Post) {
+			t.Logf("Received synced post: ID=%s, Message=%s, HasMetadata=%v", post.Id, post.Message, post.Metadata != nil)
+			if post.Metadata != nil && post.Metadata.Priority != nil {
+				t.Logf("Post has priority metadata: Priority=%v, RequestedAck=%v, PersistentNotifications=%v",
+					post.Metadata.Priority.Priority,
+					post.Metadata.Priority.RequestedAck,
+					post.Metadata.Priority.PersistentNotifications)
+			}
+			syncedPosts = append(syncedPosts, post)
+		}
+
+		// Update test server to use the sync handler
+		testServer.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandler.HandleRequest(w, r)
+		})
+
+		// Create a local post with priority metadata
+		originalPost, appErr := th.App.CreatePost(th.Context, &model.Post{
+			UserId:    th.BasicUser.Id,
+			ChannelId: testChannel.Id,
+			Message:   "Test post with priority metadata @" + th.BasicUser2.Username,
+			Metadata: &model.PostMetadata{
+				Priority: &model.PostPriority{
+					Priority:                model.NewPointer(model.PostPriorityUrgent),
+					RequestedAck:            model.NewPointer(true),
+					PersistentNotifications: model.NewPointer(true),
+				},
+			},
+		}, testChannel, model.CreatePostFlags{})
+		require.Nil(t, appErr)
+		require.NotNil(t, originalPost)
+
+		// Trigger sync
+		t.Logf("Triggering sync for channel: %s", testChannel.Id)
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for sync completion using Eventually pattern
+		require.Eventually(t, func() bool {
+			return len(syncedPosts) >= 2
+		}, 5*time.Second, 100*time.Millisecond, "Should receive synced posts via self-referential handler")
+
+		// Verify priority metadata is preserved through the complete sync flow
+		t.Logf("Found %d synced posts", len(syncedPosts))
+		syncedPost := syncedPosts[len(syncedPosts)-1]
+		require.NotNil(t, syncedPost.Metadata, "Post metadata should be preserved")
+		require.NotNil(t, syncedPost.Metadata.Priority, "Priority metadata should be preserved")
+		assert.Equal(t, model.PostPriorityUrgent, *syncedPost.Metadata.Priority.Priority, "Priority should be preserved")
+		assert.True(t, *syncedPost.Metadata.Priority.RequestedAck, "RequestedAck should be preserved")
+		assert.True(t, *syncedPost.Metadata.Priority.PersistentNotifications, "PersistentNotifications should be preserved")
+	})
+
+	t.Run("Post Acknowledgement Metadata Self-Referential Sync", func(t *testing.T) {
+		EnsureCleanState(t, th, th.App.Srv().Store())
+		var syncedPosts []*model.Post
+
+		testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServer.Close()
+
+		testChannel, selfCluster := createSharedChannelSetup(t, th, service, testServer)
+
+		syncHandler := NewSelfReferentialSyncHandler(t, service, selfCluster)
+		syncHandler.OnPostSync = func(post *model.Post) {
+			syncedPosts = append(syncedPosts, post)
+		}
+
+		testServer.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandler.HandleRequest(w, r)
+		})
+
+		// Create post with acknowledgement request
+		originalPost, appErr := th.App.CreatePost(th.Context, &model.Post{
+			UserId:    th.BasicUser.Id,
+			ChannelId: testChannel.Id,
+			Message:   "Test post requesting acknowledgements @" + th.BasicUser2.Username,
+			Metadata: &model.PostMetadata{
+				Priority: &model.PostPriority{
+					Priority:                model.NewPointer(model.PostPriorityUrgent),
+					RequestedAck:            model.NewPointer(true),
+					PersistentNotifications: model.NewPointer(false),
+				},
+			},
+		}, testChannel, model.CreatePostFlags{})
+		require.Nil(t, appErr)
+
+		// Add acknowledgement to the post
+		ack := &model.PostAcknowledgement{
+			PostId:    originalPost.Id,
+			UserId:    th.BasicUser2.Id,
+			ChannelId: originalPost.ChannelId,
+		}
+		_, appErr = th.App.SaveAcknowledgementForPostWithModel(th.Context, ack)
+		require.Nil(t, appErr)
+
+		// Trigger sync
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for sync completion
+		require.Eventually(t, func() bool {
+			return len(syncedPosts) >= 2
+		}, 5*time.Second, 100*time.Millisecond, "Should receive synced posts via self-referential handler")
+
+		// Verify acknowledgement metadata is preserved
+		syncedPost := syncedPosts[len(syncedPosts)-1]
+		require.NotNil(t, syncedPost.Metadata, "Post metadata should be preserved")
+		require.NotNil(t, syncedPost.Metadata.Priority, "Priority metadata should be preserved")
+		assert.Equal(t, model.PostPriorityUrgent, *syncedPost.Metadata.Priority.Priority, "Priority should be preserved")
+		assert.True(t, *syncedPost.Metadata.Priority.RequestedAck, "RequestedAck should be preserved")
+		assert.False(t, *syncedPost.Metadata.Priority.PersistentNotifications, "PersistentNotifications should be preserved")
+	})
+
+	t.Run("Acknowledgement Count Sync Back to Sender", func(t *testing.T) {
+		EnsureCleanState(t, th, th.App.Srv().Store())
+		var syncedPosts []*model.Post
+		var postIdToSync string
+
+		testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServer.Close()
+
+		testChannel, selfCluster := createSharedChannelSetup(t, th, service, testServer)
+
+		syncHandler := NewSelfReferentialSyncHandler(t, service, selfCluster)
+		syncHandler.OnPostSync = func(post *model.Post) {
+			if post.Id == postIdToSync {
+				t.Logf("Received sync for target post: ID=%s, HasAcks=%v", post.Id,
+					post.Metadata != nil && post.Metadata.Acknowledgements != nil)
+				if post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+					t.Logf("Acknowledgement count in sync: %d", len(post.Metadata.Acknowledgements))
+				}
+			}
+			syncedPosts = append(syncedPosts, post)
+		}
+
+		testServer.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandler.HandleRequest(w, r)
+		})
+
+		// Create post with acknowledgement request
+		originalPost, appErr := th.App.CreatePost(th.Context, &model.Post{
+			UserId:    th.BasicUser.Id,
+			ChannelId: testChannel.Id,
+			Message:   "Test post for ack count sync @" + th.BasicUser2.Username,
+			Metadata: &model.PostMetadata{
+				Priority: &model.PostPriority{
+					Priority:                model.NewPointer(model.PostPriorityUrgent),
+					RequestedAck:            model.NewPointer(true),
+					PersistentNotifications: model.NewPointer(false),
+				},
+			},
+		}, testChannel, model.CreatePostFlags{})
+		require.Nil(t, appErr)
+		postIdToSync = originalPost.Id
+
+		// Verify initial state - no acknowledgements
+		acks, appErr := th.App.GetAcknowledgementsForPost(originalPost.Id)
+		require.Nil(t, appErr)
+		require.Empty(t, acks, "Should have no acknowledgements initially")
+
+		// Trigger initial sync
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for initial sync
+		require.Eventually(t, func() bool {
+			return len(syncedPosts) >= 2
+		}, 5*time.Second, 100*time.Millisecond, "Should complete initial sync")
+
+		// Add acknowledgement
+		ackForSync := &model.PostAcknowledgement{
+			PostId:         originalPost.Id,
+			UserId:         th.BasicUser2.Id,
+			ChannelId:      originalPost.ChannelId,
+			AcknowledgedAt: model.GetMillis(),
+		}
+		_, appErr = th.App.SaveAcknowledgementForPostWithModel(th.Context, ackForSync)
+		require.Nil(t, appErr)
+
+		// Clear previous synced posts and trigger sync
+		syncedPosts = syncedPosts[:0]
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for acknowledgement sync
+		require.Eventually(t, func() bool {
+			for _, post := range syncedPosts {
+				if post.Id == postIdToSync &&
+					post.Metadata != nil &&
+					post.Metadata.Acknowledgements != nil &&
+					len(post.Metadata.Acknowledgements) > 0 {
+					return true
+				}
+			}
+			return false
+		}, 5*time.Second, 100*time.Millisecond, "Should sync acknowledgements back")
+
+		// Verify acknowledgement was synced
+		var syncedPostWithAcks *model.Post
+		for _, post := range syncedPosts {
+			if post.Id == postIdToSync && post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+				syncedPostWithAcks = post
+				break
+			}
+		}
+
+		require.NotNil(t, syncedPostWithAcks, "Should find synced post with acknowledgements")
+		require.NotNil(t, syncedPostWithAcks.Metadata.Acknowledgements, "Acknowledgements should exist")
+		require.Len(t, syncedPostWithAcks.Metadata.Acknowledgements, 1, "Should have exactly 1 acknowledgement")
+
+		ack := syncedPostWithAcks.Metadata.Acknowledgements[0]
+		assert.Equal(t, th.BasicUser2.Id, ack.UserId, "Acknowledgement should be from BasicUser2")
+		assert.Equal(t, originalPost.Id, ack.PostId, "Acknowledgement should be for the original post")
+		assert.Greater(t, ack.AcknowledgedAt, int64(0), "Acknowledgement should have a timestamp")
+	})
+
+	t.Run("Persistent Notifications Self-Referential Sync", func(t *testing.T) {
+		EnsureCleanState(t, th, th.App.Srv().Store())
+		var syncedPosts []*model.Post
+
+		testServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServer.Close()
+
+		testChannel, selfCluster := createSharedChannelSetup(t, th, service, testServer)
+
+		syncHandler := NewSelfReferentialSyncHandler(t, service, selfCluster)
+		syncHandler.OnPostSync = func(post *model.Post) {
+			syncedPosts = append(syncedPosts, post)
+		}
+
+		testServer.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandler.HandleRequest(w, r)
+		})
+
+		// Create post with persistent notifications enabled
+		_, appErr := th.App.CreatePost(th.Context, &model.Post{
+			UserId:    th.BasicUser.Id,
+			ChannelId: testChannel.Id,
+			Message:   "Test post with persistent notifications @" + th.BasicUser2.Username,
+			Metadata: &model.PostMetadata{
+				Priority: &model.PostPriority{
+					Priority:                model.NewPointer(model.PostPriorityUrgent),
+					RequestedAck:            model.NewPointer(true),
+					PersistentNotifications: model.NewPointer(true),
+				},
+			},
+		}, testChannel, model.CreatePostFlags{})
+		require.Nil(t, appErr)
+
+		// Trigger sync
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for sync completion
+		require.Eventually(t, func() bool {
+			return len(syncedPosts) >= 2
+		}, 5*time.Second, 100*time.Millisecond, "Should receive synced posts via self-referential handler")
+
+		// Verify persistent notifications setting is preserved
+		syncedPost := syncedPosts[len(syncedPosts)-1]
+		require.NotNil(t, syncedPost.Metadata, "Post metadata should be preserved")
+		require.NotNil(t, syncedPost.Metadata.Priority, "Priority metadata should be preserved")
+		assert.Equal(t, model.PostPriorityUrgent, *syncedPost.Metadata.Priority.Priority, "Priority should be preserved")
+		assert.True(t, *syncedPost.Metadata.Priority.RequestedAck, "RequestedAck should be preserved")
+		assert.True(t, *syncedPost.Metadata.Priority.PersistentNotifications, "PersistentNotifications should be preserved")
+	})
+
+	t.Run("Cross-Cluster Acknowledgement End-to-End Flow", func(t *testing.T) {
+		EnsureCleanState(t, th, th.App.Srv().Store())
+		var syncedPostsServerA []*model.Post
+		var syncedPostsServerB []*model.Post
+		var postIdToTrack string
+
+		// Create test HTTP servers for both "clusters"
+		testServerA := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServerA.Close()
+
+		testServerB := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			writeOKResponse(w)
+		}))
+		defer testServerB.Close()
+
+		// Create remote clusters for both "servers"
+		clusterA := &model.RemoteCluster{
+			RemoteId:    model.NewId(),
+			Name:        "cluster-a-ack-flow",
+			SiteURL:     testServerA.URL,
+			CreateAt:    model.GetMillis(),
+			LastPingAt:  model.GetMillis(),
+			Token:       model.NewId(),
+			CreatorId:   th.BasicUser.Id,
+			RemoteToken: model.NewId(),
+		}
+		var err error
+		clusterA, err = th.App.Srv().Store().RemoteCluster().Save(clusterA)
+		require.NoError(t, err)
+
+		clusterB := &model.RemoteCluster{
+			RemoteId:    model.NewId(),
+			Name:        "cluster-b-ack-flow",
+			SiteURL:     testServerB.URL,
+			CreateAt:    model.GetMillis(),
+			LastPingAt:  model.GetMillis(),
+			Token:       model.NewId(),
+			CreatorId:   th.BasicUser.Id,
+			RemoteToken: model.NewId(),
+		}
+		clusterB, err = th.App.Srv().Store().RemoteCluster().Save(clusterB)
+		require.NoError(t, err)
+
+		// Create test channel and add local user
+		testChannel := th.CreatePublicChannel()
+		_, appErr := th.App.AddUserToChannel(th.Context, th.BasicUser, testChannel, false)
+		require.Nil(t, appErr)
+
+		// Create remote user from Cluster B
+		remoteUserFromClusterB := &model.User{
+			Email:         "remote-user-b@example.com",
+			Username:      "remoteuserb" + model.NewId()[:4],
+			Password:      "password123",
+			EmailVerified: true,
+			RemoteId:      &clusterB.RemoteId,
+		}
+		remoteUserFromClusterB, appErr = th.App.CreateUser(th.Context, remoteUserFromClusterB)
+		require.Nil(t, appErr)
+
+		// Add remote user to team and channel
+		_, _, appErr = th.App.AddUserToTeam(th.Context, testChannel.TeamId, remoteUserFromClusterB.Id, "")
+		require.Nil(t, appErr)
+		_, appErr = th.App.AddUserToChannel(th.Context, remoteUserFromClusterB, testChannel, false)
+		require.Nil(t, appErr)
+
+		// Create shared channel
+		sc := &model.SharedChannel{
+			ChannelId: testChannel.Id,
+			TeamId:    testChannel.TeamId,
+			Home:      true,
+			ShareName: "test_cross_cluster_ack",
+			CreatorId: th.BasicUser.Id,
+			RemoteId:  "",
+		}
+		sc, err = th.App.ShareChannel(th.Context, sc)
+		require.NoError(t, err)
+
+		// Create shared channel remotes for both clusters
+		scrA := &model.SharedChannelRemote{
+			Id:                model.NewId(),
+			ChannelId:         sc.ChannelId,
+			CreatorId:         sc.CreatorId,
+			IsInviteAccepted:  true,
+			IsInviteConfirmed: true,
+			RemoteId:          clusterA.RemoteId,
+		}
+		_, err = th.App.SaveSharedChannelRemote(scrA)
+		require.NoError(t, err)
+
+		scrB := &model.SharedChannelRemote{
+			Id:                model.NewId(),
+			ChannelId:         sc.ChannelId,
+			CreatorId:         sc.CreatorId,
+			IsInviteAccepted:  true,
+			IsInviteConfirmed: true,
+			RemoteId:          clusterB.RemoteId,
+		}
+		_, err = th.App.SaveSharedChannelRemote(scrB)
+		require.NoError(t, err)
+
+		// Initialize sync handlers for both clusters
+		syncHandlerA := NewSelfReferentialSyncHandler(t, service, clusterA)
+		syncHandlerA.OnPostSync = func(post *model.Post) {
+			t.Logf("Cluster A received sync: ID=%s, Message=%s, HasAcks=%v",
+				post.Id, post.Message,
+				post.Metadata != nil && post.Metadata.Acknowledgements != nil)
+			if post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+				t.Logf("  Cluster A sees %d acknowledgements", len(post.Metadata.Acknowledgements))
+			}
+			syncedPostsServerA = append(syncedPostsServerA, post)
+		}
+
+		syncHandlerB := NewSelfReferentialSyncHandler(t, service, clusterB)
+		syncHandlerB.OnPostSync = func(post *model.Post) {
+			t.Logf("Cluster B received sync: ID=%s, Message=%s, RequestedAck=%v",
+				post.Id, post.Message,
+				post.Metadata != nil && post.Metadata.Priority != nil && post.Metadata.Priority.RequestedAck != nil && *post.Metadata.Priority.RequestedAck)
+			syncedPostsServerB = append(syncedPostsServerB, post)
+		}
+
+		// Update test servers to use sync handlers
+		testServerA.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandlerA.HandleRequest(w, r)
+		})
+
+		testServerB.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			syncHandlerB.HandleRequest(w, r)
+		})
+
+		// STEP 1: Server A creates a post with acknowledgement request
+		t.Log("=== STEP 1: Server A creates post with ack request ===")
+		originalPost, appErr := th.App.CreatePost(th.Context, &model.Post{
+			UserId:    th.BasicUser.Id,
+			ChannelId: testChannel.Id,
+			Message:   "Cross-cluster ack test - please acknowledge",
+			Metadata: &model.PostMetadata{
+				Priority: &model.PostPriority{
+					Priority:                model.NewPointer(model.PostPriorityUrgent),
+					RequestedAck:            model.NewPointer(true),
+					PersistentNotifications: model.NewPointer(false),
+				},
+			},
+		}, testChannel, model.CreatePostFlags{})
+		require.Nil(t, appErr)
+		postIdToTrack = originalPost.Id
+
+		// Verify initial state - no acknowledgements
+		acks, appErr := th.App.GetAcknowledgementsForPost(originalPost.Id)
+		require.Nil(t, appErr)
+		require.Empty(t, acks, "Should have no acknowledgements initially")
+
+		// STEP 2: Post syncs from Server A to Server B
+		t.Log("=== STEP 2: Post syncs from Server A to Server B ===")
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for Server B to receive the post
+		var syncedPostIdOnServerB string
+		require.Eventually(t, func() bool {
+			for _, post := range syncedPostsServerB {
+				if post.Message == originalPost.Message && post.Metadata != nil && post.Metadata.Priority != nil &&
+					post.Metadata.Priority.RequestedAck != nil && *post.Metadata.Priority.RequestedAck {
+					syncedPostIdOnServerB = post.Id
+					t.Logf("Server B received post %s with ack request (original was %s)", post.Id, postIdToTrack)
+					return true
+				}
+			}
+			return false
+		}, 5*time.Second, 100*time.Millisecond, "Server B should receive post with ack request")
+
+		// STEP 3: User on Server B acknowledges the post
+		t.Log("=== STEP 3: User on Server B acknowledges the post ===")
+		ackFromServerB := &model.PostAcknowledgement{
+			PostId:         syncedPostIdOnServerB,
+			UserId:         remoteUserFromClusterB.Id,
+			ChannelId:      testChannel.Id,
+			AcknowledgedAt: model.GetMillis(),
+		}
+		_, appErr = th.App.SaveAcknowledgementForPostWithModel(th.Context, ackFromServerB)
+		require.Nil(t, appErr)
+
+		// Verify acknowledgement was saved locally
+		acksAfterSave, appErr := th.App.GetAcknowledgementsForPost(syncedPostIdOnServerB)
+		require.Nil(t, appErr)
+		require.Len(t, acksAfterSave, 1, "Should have exactly 1 acknowledgement after user B acks")
+		require.Equal(t, remoteUserFromClusterB.Id, acksAfterSave[0].UserId)
+
+		// STEP 4: Acknowledgement syncs back from Server B to Server A
+		t.Log("=== STEP 4: Acknowledgement syncs back from Server B to Server A ===")
+		// Clear previous sync data to focus on acknowledgement sync
+		syncedPostsServerA = syncedPostsServerA[:0]
+		syncedPostsServerB = syncedPostsServerB[:0]
+
+		// Trigger sync to send acknowledgement back to Server A
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Wait for Server A to receive the acknowledgement sync
+		require.Eventually(t, func() bool {
+			for _, post := range syncedPostsServerA {
+				if post.Id == postIdToTrack && post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+					t.Logf("Server A received post %s with %d acknowledgements", post.Id, len(post.Metadata.Acknowledgements))
+					return len(post.Metadata.Acknowledgements) > 0
+				}
+			}
+			return false
+		}, 5*time.Second, 100*time.Millisecond, "Server A should receive acknowledgement sync")
+
+		// STEP 5: Verify the complete acknowledgement flow
+		t.Log("=== STEP 5: Verify complete acknowledgement flow ===")
+		var serverAPostWithAcks *model.Post
+		for _, post := range syncedPostsServerA {
+			if post.Id == postIdToTrack && post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+				serverAPostWithAcks = post
+				break
+			}
+		}
+
+		require.NotNil(t, serverAPostWithAcks, "Server A should receive post with acknowledgements")
+		require.NotNil(t, serverAPostWithAcks.Metadata.Acknowledgements, "Acknowledgements should exist")
+		require.Len(t, serverAPostWithAcks.Metadata.Acknowledgements, 1, "Should have exactly 1 acknowledgement")
+
+		// Verify acknowledgement details
+		ack := serverAPostWithAcks.Metadata.Acknowledgements[0]
+		assert.Equal(t, remoteUserFromClusterB.Id, ack.UserId, "Acknowledgement should be from remote user")
+		assert.Equal(t, postIdToTrack, ack.PostId, "Acknowledgement should be for the correct post")
+		assert.Greater(t, ack.AcknowledgedAt, int64(0), "Acknowledgement should have a timestamp")
+
+		// Verify priority metadata is preserved
+		require.NotNil(t, serverAPostWithAcks.Metadata.Priority, "Priority metadata should be preserved")
+		assert.Equal(t, model.PostPriorityUrgent, *serverAPostWithAcks.Metadata.Priority.Priority, "Priority should be preserved")
+		assert.True(t, *serverAPostWithAcks.Metadata.Priority.RequestedAck, "RequestedAck should be preserved")
+
+		// STEP 6: Test echo prevention - verify no duplicate acknowledgements
+		t.Log("=== STEP 6: Test echo prevention ===")
+		syncedPostsServerA = syncedPostsServerA[:0]
+
+		// Trigger another sync to ensure no duplicates are created
+		service.NotifyChannelChanged(testChannel.Id)
+
+		// Verify acknowledgement count remains 1 (no duplicates)
+		require.Eventually(t, func() bool {
+			for _, post := range syncedPostsServerA {
+				if post.Id == postIdToTrack && post.Metadata != nil && post.Metadata.Acknowledgements != nil {
+					return len(post.Metadata.Acknowledgements) == 1
+				}
+			}
+			return len(syncedPostsServerA) > 0
+		}, 3*time.Second, 100*time.Millisecond, "Should maintain single acknowledgement after resync")
+
+		t.Logf("✅ Cross-cluster acknowledgement flow completed successfully:")
+		t.Logf("   1. Server A created post with ack request: %s", postIdToTrack)
+		t.Logf("   2. Post synced to Server B with priority metadata intact")
+		t.Logf("   3. User on Server B acknowledged the post: %s", ack.UserId)
+		t.Logf("   4. Acknowledgement synced back to Server A")
+		t.Logf("   5. Server A shows acknowledgement in post metadata")
+		t.Logf("   6. Echo prevention verified - no duplicates created")
+	})
+}

server/channels/api4/shared_channel_test_utils.go

@@ -0,0 +1,245 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package api4
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/v8/channels/store"
+	"github.com/mattermost/mattermost/server/v8/channels/store/sqlstore"
+	"github.com/mattermost/mattermost/server/v8/platform/services/remotecluster"
+	"github.com/mattermost/mattermost/server/v8/platform/services/sharedchannel"
+	"github.com/stretchr/testify/require"
+)
+
+// writeOKResponse writes a standard OK JSON response in the format expected by remotecluster
+func writeOKResponse(w http.ResponseWriter) {
+	response := &remotecluster.Response{
+		Status: "OK",
+		Err:    "",
+	}
+
+	// Set empty sync response as payload
+	syncResp := &model.SyncResponse{}
+	_ = response.SetPayload(syncResp)
+
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	respBytes, _ := json.Marshal(response)
+	_, _ = w.Write(respBytes)
+}
+
+// SelfReferentialSyncHandler handles incoming sync messages for self-referential tests.
+type SelfReferentialSyncHandler struct {
+	t                *testing.T
+	service          *sharedchannel.Service
+	selfCluster      *model.RemoteCluster
+	syncMessageCount *int32
+
+	// Callbacks for capturing sync data
+	OnPostSync            func(post *model.Post)
+	OnAcknowledgementSync func(ack *model.PostAcknowledgement)
+}
+
+// NewSelfReferentialSyncHandler creates a new handler for processing sync messages in tests
+func NewSelfReferentialSyncHandler(t *testing.T, service *sharedchannel.Service, selfCluster *model.RemoteCluster) *SelfReferentialSyncHandler {
+	count := int32(0)
+	return &SelfReferentialSyncHandler{
+		t:                t,
+		service:          service,
+		selfCluster:      selfCluster,
+		syncMessageCount: &count,
+	}
+}
+
+// HandleRequest processes incoming HTTP requests for the test server.
+func (h *SelfReferentialSyncHandler) HandleRequest(w http.ResponseWriter, r *http.Request) {
+	switch r.URL.Path {
+	case "/api/v4/remotecluster/msg":
+		atomic.AddInt32(h.syncMessageCount, 1)
+
+		// Read and process the sync message
+		body, _ := io.ReadAll(r.Body)
+
+		// The message is wrapped in a RemoteClusterFrame
+		var frame model.RemoteClusterFrame
+		err := json.Unmarshal(body, &frame)
+		if err == nil {
+			// Process the message to update cursor
+			response := &remotecluster.Response{}
+			processErr := h.service.OnReceiveSyncMessageForTesting(frame.Msg, h.selfCluster, response)
+			if processErr != nil {
+				response.Status = "ERROR"
+				response.Err = processErr.Error()
+				h.t.Logf("Sync processing error: %v", processErr)
+			} else {
+				response.Status = "OK"
+				response.Err = ""
+
+				var syncMsg model.SyncMsg
+				if unmarshalErr := json.Unmarshal(frame.Msg.Payload, &syncMsg); unmarshalErr == nil {
+					// Handle posts - call callback for verification
+					if len(syncMsg.Posts) > 0 && h.OnPostSync != nil {
+						for _, post := range syncMsg.Posts {
+							h.OnPostSync(post)
+						}
+					}
+
+					// Handle acknowledgements - call callback for verification
+					if len(syncMsg.Acknowledgements) > 0 && h.OnAcknowledgementSync != nil {
+						for _, ack := range syncMsg.Acknowledgements {
+							h.OnAcknowledgementSync(ack)
+						}
+					}
+
+					// Create success response
+					syncResp := &model.SyncResponse{
+						UsersSyncd: make([]string, 0),
+					}
+					_ = response.SetPayload(syncResp)
+				}
+			}
+
+			// Send the response
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusOK)
+			respBytes, _ := json.Marshal(response)
+			_, _ = w.Write(respBytes)
+			return
+		}
+
+		writeOKResponse(w)
+
+	case "/api/v4/remotecluster/ping":
+		writeOKResponse(w)
+
+	case "/api/v4/remotecluster/confirm_invite":
+		writeOKResponse(w)
+
+	default:
+		writeOKResponse(w)
+	}
+}
+
+// GetSyncMessageCount returns the current count of sync messages received
+func (h *SelfReferentialSyncHandler) GetSyncMessageCount() int32 {
+	return atomic.LoadInt32(h.syncMessageCount)
+}
+
+// ensureCleanState ensures a clean test state by removing all shared channels and remote clusters.
+// This helps prevent state pollution between tests.
+func EnsureCleanState(t *testing.T, th *TestHelper, ss store.Store) {
+	t.Helper()
+
+	// First, wait for any pending async tasks to complete, then shutdown services
+	scsInterface := th.App.Srv().GetSharedChannelSyncService()
+	if scsInterface != nil && scsInterface.Active() {
+		// Cast to concrete type to access testing methods
+		if service, ok := scsInterface.(*sharedchannel.Service); ok {
+			// Wait for any pending tasks from previous tests to complete
+			require.Eventually(t, func() bool {
+				return !service.HasPendingTasksForTesting()
+			}, 10*time.Second, 100*time.Millisecond, "All pending sync tasks should complete before cleanup")
+		}
+
+		// Shutdown the shared channel service to stop any async operations
+		_ = scsInterface.Shutdown()
+
+		// Wait for shutdown to complete with more time
+		require.Eventually(t, func() bool {
+			return !scsInterface.Active()
+		}, 5*time.Second, 100*time.Millisecond, "Shared channel service should be inactive after shutdown")
+	}
+
+	// Clear all shared channels and remotes from previous tests
+	allSharedChannels, _ := ss.SharedChannel().GetAll(0, 1000, model.SharedChannelFilterOpts{})
+	for _, sc := range allSharedChannels {
+		// Delete all remotes for this channel
+		remotes, _ := ss.SharedChannel().GetRemotes(0, 100, model.SharedChannelRemoteFilterOpts{ChannelId: sc.ChannelId})
+		for _, remote := range remotes {
+			_, _ = ss.SharedChannel().DeleteRemote(remote.Id)
+		}
+		// Delete the shared channel
+		_, _ = ss.SharedChannel().Delete(sc.ChannelId)
+	}
+
+	// Delete all remote clusters
+	allRemoteClusters, _ := ss.RemoteCluster().GetAll(0, 1000, model.RemoteClusterQueryFilter{})
+	for _, rc := range allRemoteClusters {
+		_, _ = ss.RemoteCluster().Delete(rc.RemoteId)
+	}
+
+	// Clear all acknowledgements from previous tests by setting AcknowledgedAt to 0
+	// This uses raw SQL to ensure all acknowledgements are cleared regardless of their state
+	if sqlStore, ok := ss.(*sqlstore.SqlStore); ok {
+		_, _ = sqlStore.GetMaster().Exec("UPDATE PostAcknowledgements SET AcknowledgedAt = 0")
+	}
+
+	// Remove all channel members from test channels (except the basic team/channel setup)
+	channels, _ := ss.Channel().GetAll(th.BasicTeam.Id)
+	for _, channel := range channels {
+		// Skip direct message and group channels, and skip the default channels
+		if channel.Type != model.ChannelTypeDirect && channel.Type != model.ChannelTypeGroup &&
+			channel.Id != th.BasicChannel.Id {
+			members, _ := ss.Channel().GetMembers(model.ChannelMembersGetOptions{
+				ChannelID: channel.Id,
+			})
+			for _, member := range members {
+				_ = ss.Channel().RemoveMember(th.Context, channel.Id, member.UserId)
+			}
+		}
+	}
+
+	// Get all active users and deactivate non-basic ones
+	options := &model.UserGetOptions{
+		Page:    0,
+		PerPage: 200,
+		Active:  true,
+	}
+	users, _ := ss.User().GetAllProfiles(options)
+	for _, user := range users {
+		// Keep only the basic test users active
+		if user.Id != th.BasicUser.Id && user.Id != th.BasicUser2.Id &&
+			user.Id != th.SystemAdminUser.Id {
+			// Deactivate the user (soft delete)
+			user.DeleteAt = model.GetMillis()
+			_, _ = ss.User().Update(th.Context, user, true)
+		}
+	}
+
+	// Verify cleanup is complete
+	require.Eventually(t, func() bool {
+		sharedChannels, _ := ss.SharedChannel().GetAll(0, 1000, model.SharedChannelFilterOpts{})
+		remoteClusters, _ := ss.RemoteCluster().GetAll(0, 1000, model.RemoteClusterQueryFilter{})
+		return len(sharedChannels) == 0 && len(remoteClusters) == 0
+	}, 2*time.Second, 100*time.Millisecond, "Failed to clean up shared channels and remote clusters")
+
+	// Restart services and ensure they are running and ready
+	if scsInterface != nil {
+		// Restart the shared channel service
+		_ = scsInterface.Start()
+
+		if scs, ok := scsInterface.(*sharedchannel.Service); ok {
+			require.Eventually(t, func() bool {
+				return scs.Active()
+			}, 5*time.Second, 100*time.Millisecond, "Shared channel service should be active after restart")
+		}
+	}
+
+	rcService := th.App.Srv().GetRemoteClusterService()
+	if rcService != nil {
+		if rc, ok := rcService.(*remotecluster.Service); ok {
+			rc.SetActive(true)
+		}
+		require.Eventually(t, func() bool {
+			return rcService.Active()
+		}, 5*time.Second, 100*time.Millisecond, "Remote cluster service should be active")
+	}
+}

server/channels/app/platform/shared_channel_notifier.go

@@ -21,6 +21,8 @@ var sharedChannelEventsForSync = []model.WebsocketEventType{
 	model.WebsocketEventPostDeleted,
 	model.WebsocketEventReactionAdded,
 	model.WebsocketEventReactionRemoved,
+	model.WebsocketEventAcknowledgementAdded,
+	model.WebsocketEventAcknowledgementRemoved,
 }
 
 var sharedChannelEventsForInvitation = []model.WebsocketEventType{

server/channels/app/post.go

@@ -773,9 +773,14 @@ func (a *App) UpdatePost(c request.CTX, receivedUpdatedPost *model.Post, updateP
 	if newPost == nil {
 		return nil, model.NewAppError("UpdatePost", "Post rejected by plugin. "+rejectionReason, nil, "", http.StatusBadRequest)
 	}
-	// Restore the post metadata that was stripped by the plugin. Set it to
-	// the last known good.
-	newPost.Metadata = oldPost.Metadata
+	// Always use incoming metadata when provided, otherwise retain existing
+	if receivedUpdatedPost.Metadata != nil {
+		newPost.Metadata = receivedUpdatedPost.Metadata.Copy()
+	} else {
+		// Restore the post metadata that was stripped by the plugin. Set it to
+		// the last known good.
+		newPost.Metadata = oldPost.Metadata
+	}
 
 	rpost, nErr := a.Srv().Store().Post().Update(c, newPost, oldPost)
 	if nErr != nil {

server/channels/app/post_acknowledgements.go

@@ -15,9 +15,19 @@ import (
 )
 
 func (a *App) SaveAcknowledgementForPost(c request.CTX, postID, userID string) (*model.PostAcknowledgement, *model.AppError) {
-	post, err := a.GetSinglePost(c, postID, false)
-	if err != nil {
-		return nil, err
+	return a.saveAcknowledgementForPostWithPost(c, nil, userID, postID)
+}
+
+func (a *App) saveAcknowledgementForPostWithPost(c request.CTX, post *model.Post, userID string, postID ...string) (*model.PostAcknowledgement, *model.AppError) {
+	if post == nil {
+		if len(postID) == 0 {
+			return nil, model.NewAppError("SaveAcknowledgementForPost", "app.acknowledgement.save.missing_post.app_error", nil, "", http.StatusBadRequest)
+		}
+		var err *model.AppError
+		post, err = a.GetSinglePost(c, postID[0], false)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	channel, err := a.GetChannel(c, post.ChannelId)
@@ -29,8 +39,14 @@ func (a *App) SaveAcknowledgementForPost(c request.CTX, postID, userID string) (
 		return nil, model.NewAppError("SaveAcknowledgementForPost", "api.acknowledgement.save.archived_channel.app_error", nil, "", http.StatusForbidden)
 	}
 
-	acknowledgedAt := model.GetMillis()
-	acknowledgement, nErr := a.Srv().Store().PostAcknowledgement().Save(postID, userID, acknowledgedAt)
+	// Pre-populate the ChannelId to save a DB call in store
+	acknowledgement := &model.PostAcknowledgement{
+		PostId:    post.Id,
+		UserId:    userID,
+		ChannelId: post.ChannelId,
+	}
+
+	savedAck, nErr := a.Srv().Store().PostAcknowledgement().SaveWithModel(acknowledgement)
 	if nErr != nil {
 		var appErr *model.AppError
 		switch {
@@ -56,15 +72,28 @@ func (a *App) SaveAcknowledgementForPost(c request.CTX, postID, userID string) (
 	// The post is always modified since the UpdateAt always changes
 	a.Srv().Store().Post().InvalidateLastPostTimeCache(channel.Id)
 
-	a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementAdded, acknowledgement, post)
+	a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementAdded, savedAck, post)
 
-	return acknowledgement, nil
+	// Trigger post updated event to ensure shared channel sync
+	a.sendPostUpdateEvent(c, post)
+
+	return savedAck, nil
 }
 
 func (a *App) DeleteAcknowledgementForPost(c request.CTX, postID, userID string) *model.AppError {
-	post, err := a.GetSinglePost(c, postID, false)
-	if err != nil {
-		return err
+	return a.deleteAcknowledgementForPostWithPost(c, nil, userID, postID)
+}
+
+func (a *App) deleteAcknowledgementForPostWithPost(c request.CTX, post *model.Post, userID string, postID ...string) *model.AppError {
+	if post == nil {
+		if len(postID) == 0 {
+			return model.NewAppError("DeleteAcknowledgementForPost", "app.acknowledgement.delete.missing_post.app_error", nil, "", http.StatusBadRequest)
+		}
+		var err *model.AppError
+		post, err = a.GetSinglePost(c, postID[0], false)
+		if err != nil {
+			return err
+		}
 	}
 
 	channel, err := a.GetChannel(c, post.ChannelId)
@@ -76,7 +105,7 @@ func (a *App) DeleteAcknowledgementForPost(c request.CTX, postID, userID string)
 		return model.NewAppError("DeleteAcknowledgementForPost", "api.acknowledgement.delete.archived_channel.app_error", nil, "", http.StatusForbidden)
 	}
 
-	oldAck, nErr := a.Srv().Store().PostAcknowledgement().Get(postID, userID)
+	oldAck, nErr := a.Srv().Store().PostAcknowledgement().Get(post.Id, userID)
 
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
@@ -102,6 +131,9 @@ func (a *App) DeleteAcknowledgementForPost(c request.CTX, postID, userID string)
 
 	a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementRemoved, oldAck, post)
 
+	// Trigger post updated event to ensure shared channel sync
+	a.sendPostUpdateEvent(c, post)
+
 	return nil
 }
 
@@ -130,6 +162,80 @@ func (a *App) GetAcknowledgementsForPostList(postList *model.PostList) (map[stri
 	return acknowledgementsMap, nil
 }
 
+// SaveAcknowledgementsForPost saves multiple acknowledgements for a post in a single operation.
+func (a *App) SaveAcknowledgementsForPost(c request.CTX, postID string, userIDs []string) ([]*model.PostAcknowledgement, *model.AppError) {
+	if len(userIDs) == 0 {
+		return []*model.PostAcknowledgement{}, nil
+	}
+
+	post, err := a.GetSinglePost(c, postID, false)
+	if err != nil {
+		return nil, err
+	}
+
+	channel, err := a.GetChannel(c, post.ChannelId)
+	if err != nil {
+		return nil, err
+	}
+
+	if channel.DeleteAt > 0 {
+		return nil, model.NewAppError("SaveAcknowledgementsForPost", "api.acknowledgement.save.archived_channel.app_error", nil, "", http.StatusForbidden)
+	}
+
+	// Create acknowledgements with current timestamp
+	acknowledgedAt := model.GetMillis()
+	var acknowledgements []*model.PostAcknowledgement
+
+	for _, userID := range userIDs {
+		acknowledgements = append(acknowledgements, &model.PostAcknowledgement{
+			PostId:         post.Id,
+			UserId:         userID,
+			ChannelId:      post.ChannelId,
+			AcknowledgedAt: acknowledgedAt,
+		})
+	}
+
+	// Save all acknowledgements
+	savedAcks, nErr := a.Srv().Store().PostAcknowledgement().BatchSave(acknowledgements)
+	if nErr != nil {
+		var appErr *model.AppError
+		switch {
+		case errors.As(nErr, &appErr):
+			return nil, appErr
+		default:
+			return nil, model.NewAppError("SaveAcknowledgementsForPost", "app.acknowledgement.batch_save.app_error", nil, "", http.StatusInternalServerError).Wrap(nErr)
+		}
+	}
+
+	// Resolve persistent notifications for each user
+	for _, userID := range userIDs {
+		if appErr := a.ResolvePersistentNotification(c, post, userID); appErr != nil {
+			a.CountNotificationReason(model.NotificationStatusError, model.NotificationTypeWebsocket, model.NotificationReasonResolvePersistentNotificationError, model.NotificationNoPlatform)
+			a.NotificationsLog().Error("Error resolving persistent notification",
+				mlog.String("sender_id", userID),
+				mlog.String("post_id", post.RootId),
+				mlog.String("status", model.NotificationStatusError),
+				mlog.String("reason", model.NotificationReasonResolvePersistentNotificationError),
+				mlog.Err(appErr),
+			)
+			// We continue processing other acknowledgements even if one fails
+		}
+	}
+
+	// The post is always modified since the UpdateAt always changes
+	a.Srv().Store().Post().InvalidateLastPostTimeCache(channel.Id)
+
+	// Send WebSocket events for each acknowledgement
+	for _, ack := range savedAcks {
+		a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementAdded, ack, post)
+	}
+
+	// Trigger post updated event to ensure shared channel sync
+	a.sendPostUpdateEvent(c, post)
+
+	return savedAcks, nil
+}
+
 func (a *App) sendAcknowledgementEvent(rctx request.CTX, event model.WebsocketEventType, acknowledgement *model.PostAcknowledgement, post *model.Post) {
 	// send out that a acknowledgement has been added/removed
 	message := model.NewWebSocketEvent(event, "", post.ChannelId, "", nil, "")
@@ -141,3 +247,107 @@ func (a *App) sendAcknowledgementEvent(rctx request.CTX, event model.WebsocketEv
 	message.Add("acknowledgement", string(acknowledgementJSON))
 	a.Publish(message)
 }
+
+func (a *App) SaveAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, *model.AppError) {
+	// Get the post to verify it exists and get the channel
+	post, err := a.GetSinglePost(c, acknowledgement.PostId, false)
+	if err != nil {
+		return nil, err
+	}
+
+	channel, err := a.GetChannel(c, post.ChannelId)
+	if err != nil {
+		return nil, err
+	}
+
+	if channel.DeleteAt > 0 {
+		return nil, model.NewAppError("SaveAcknowledgementForPostWithModel", "api.acknowledgement.save.archived_channel.app_error", nil, "", http.StatusForbidden)
+	}
+
+	// Make sure ChannelId is set
+	if acknowledgement.ChannelId == "" {
+		acknowledgement.ChannelId = post.ChannelId
+	}
+
+	savedAck, nErr := a.Srv().Store().PostAcknowledgement().SaveWithModel(acknowledgement)
+	if nErr != nil {
+		var appErr *model.AppError
+		switch {
+		case errors.As(nErr, &appErr):
+			return nil, appErr
+		default:
+			return nil, model.NewAppError("SaveAcknowledgementForPostWithModel", "app.acknowledgement.save.save.app_error", nil, "", http.StatusInternalServerError).Wrap(nErr)
+		}
+	}
+
+	if appErr := a.ResolvePersistentNotification(c, post, acknowledgement.UserId); appErr != nil {
+		a.CountNotificationReason(model.NotificationStatusError, model.NotificationTypeWebsocket, model.NotificationReasonResolvePersistentNotificationError, model.NotificationNoPlatform)
+		a.NotificationsLog().Error("Error resolving persistent notification",
+			mlog.String("sender_id", acknowledgement.UserId),
+			mlog.String("post_id", post.RootId),
+			mlog.String("status", model.NotificationStatusError),
+			mlog.String("reason", model.NotificationReasonResolvePersistentNotificationError),
+			mlog.Err(appErr),
+		)
+		return nil, appErr
+	}
+
+	// The post is always modified since the UpdateAt always changes
+	a.Srv().Store().Post().InvalidateLastPostTimeCache(channel.Id)
+
+	a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementAdded, savedAck, post)
+
+	// Trigger post updated event to ensure shared channel sync
+	a.sendPostUpdateEvent(c, post)
+
+	return savedAck, nil
+}
+
+func (a *App) DeleteAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) *model.AppError {
+	// Get the post to verify it exists and get the channel
+	post, err := a.GetSinglePost(c, acknowledgement.PostId, false)
+	if err != nil {
+		return err
+	}
+
+	channel, err := a.GetChannel(c, post.ChannelId)
+	if err != nil {
+		return err
+	}
+
+	if channel.DeleteAt > 0 {
+		return model.NewAppError("DeleteAcknowledgementForPostWithModel", "api.acknowledgement.delete.archived_channel.app_error", nil, "", http.StatusForbidden)
+	}
+
+	nErr := a.Srv().Store().PostAcknowledgement().Delete(acknowledgement)
+	if nErr != nil {
+		return model.NewAppError("DeleteAcknowledgementForPostWithModel", "app.acknowledgement.delete.app_error", nil, "", http.StatusInternalServerError).Wrap(nErr)
+	}
+
+	// The post is always modified since the UpdateAt always changes
+	a.Srv().Store().Post().InvalidateLastPostTimeCache(channel.Id)
+
+	a.sendAcknowledgementEvent(c, model.WebsocketEventAcknowledgementRemoved, acknowledgement, post)
+
+	// Trigger post updated event to ensure shared channel sync
+	a.sendPostUpdateEvent(c, post)
+
+	return nil
+}
+
+func (a *App) sendPostUpdateEvent(c request.CTX, post *model.Post) {
+	if post == nil {
+		c.Logger().Warn("sendPostUpdateEvent called with nil post")
+		return
+	}
+
+	// Send a post edited event to trigger shared channel sync
+	message := model.NewWebSocketEvent(model.WebsocketEventPostEdited, "", post.ChannelId, "", nil, "")
+
+	// Prepare the post with metadata for the event
+	preparedPost := a.PreparePostForClient(c, post, false, true, true)
+
+	if appErr := a.publishWebsocketEventForPost(c, preparedPost, message); appErr != nil {
+		c.Logger().Warn("Failed to send post update event for acknowledgement sync", mlog.String("post_id", post.Id), mlog.Err(appErr))
+	}
+}

server/channels/app/post_acknowledgements_test.go

@@ -109,7 +109,13 @@ func testDeleteAcknowledgementForPost(t *testing.T) {
 	})
 
 	t.Run("delete acknowledgment for post after 5 min after acknowledged should not delete", func(t *testing.T) {
-		_, nErr := th.App.Srv().Store().PostAcknowledgement().Save(post.Id, th.BasicUser.Id, model.GetMillis()-int64(6*60*1000))
+		acknowledgement := &model.PostAcknowledgement{
+			PostId:         post.Id,
+			UserId:         th.BasicUser.Id,
+			AcknowledgedAt: model.GetMillis() - int64(6*60*1000),
+			ChannelId:      post.ChannelId,
+		}
+		_, nErr := th.App.Srv().Store().PostAcknowledgement().SaveWithModel(acknowledgement)
 		require.NoError(t, nErr)
 
 		acknowledgments, err := th.App.GetAcknowledgementsForPost(post.Id)
@@ -180,13 +186,13 @@ func testGetAcknowledgementsForPostList(t *testing.T) {
 		acknowledgementsMap, err := th.App.GetAcknowledgementsForPostList(postList)
 		require.Nil(t, err)
 
-		expected := map[string][]*model.PostAcknowledgement{
-			p1.Id: acks1,
-			p2.Id: acks2,
-		}
-		require.Equal(t, expected, acknowledgementsMap)
+		// Verify p1 acknowledgements (order-agnostic)
 		require.Len(t, acknowledgementsMap[p1.Id], 2)
+		require.ElementsMatch(t, acks1, acknowledgementsMap[p1.Id])
+
+		// Verify p2 acknowledgements (order-agnostic)
 		require.Len(t, acknowledgementsMap[p2.Id], 1)
+		require.ElementsMatch(t, acks2, acknowledgementsMap[p2.Id])
 		require.Nil(t, acknowledgementsMap[p3.Id])
 	})
 }

server/channels/db/migrations/migrations.list

@@ -277,6 +277,8 @@ channels/db/migrations/mysql/000139_remoteclusters_add_last_global_user_sync_at.
 channels/db/migrations/mysql/000139_remoteclusters_add_last_global_user_sync_at.up.sql
 channels/db/migrations/mysql/000140_add_lastmemberssyncat_to_sharedchannelremotes.down.sql
 channels/db/migrations/mysql/000140_add_lastmemberssyncat_to_sharedchannelremotes.up.sql
+channels/db/migrations/mysql/000141_add_remoteid_channelid_to_post_acknowledgements.down.sql
+channels/db/migrations/mysql/000141_add_remoteid_channelid_to_post_acknowledgements.up.sql
 channels/db/migrations/postgres/000001_create_teams.down.sql
 channels/db/migrations/postgres/000001_create_teams.up.sql
 channels/db/migrations/postgres/000002_create_team_members.down.sql
@@ -555,3 +557,5 @@ channels/db/migrations/postgres/000139_remoteclusters_add_last_global_user_sync_
 channels/db/migrations/postgres/000139_remoteclusters_add_last_global_user_sync_at.up.sql
 channels/db/migrations/postgres/000140_add_lastmemberssyncat_to_sharedchannelremotes.down.sql
 channels/db/migrations/postgres/000140_add_lastmemberssyncat_to_sharedchannelremotes.up.sql
+channels/db/migrations/postgres/000141_add_remoteid_channelid_to_post_acknowledgements.down.sql
+channels/db/migrations/postgres/000141_add_remoteid_channelid_to_post_acknowledgements.up.sql

server/channels/db/migrations/mysql/000141_add_remoteid_channelid_to_post_acknowledgements.down.sql

@@ -0,0 +1,29 @@
+SET @preparedStatement1 = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'PostAcknowledgements'
+        AND table_schema = DATABASE()
+        AND column_name = 'RemoteId'
+    ) > 0,
+    'ALTER TABLE PostAcknowledgements DROP COLUMN RemoteId;',
+    'SELECT 1'
+));
+
+PREPARE alterIfExists FROM @preparedStatement1;
+EXECUTE alterIfExists;
+DEALLOCATE PREPARE alterIfExists;
+
+SET @preparedStatement2 = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'PostAcknowledgements'
+        AND table_schema = DATABASE()
+        AND column_name = 'ChannelId'
+    ) > 0,
+    'ALTER TABLE PostAcknowledgements DROP COLUMN ChannelId;',
+    'SELECT 1'
+));
+
+PREPARE alterIfExists FROM @preparedStatement2;
+EXECUTE alterIfExists;
+DEALLOCATE PREPARE alterIfExists;

server/channels/db/migrations/mysql/000141_add_remoteid_channelid_to_post_acknowledgements.up.sql

@@ -0,0 +1,29 @@
+SET @preparedStatement1 = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'PostAcknowledgements'
+        AND table_schema = DATABASE()
+        AND column_name = 'RemoteId'
+    ) > 0,
+    'SELECT 1;',
+    'ALTER TABLE PostAcknowledgements ADD COLUMN RemoteId varchar(26) DEFAULT \'\';'
+));
+
+PREPARE addColumnIfNotExists FROM @preparedStatement1;
+EXECUTE addColumnIfNotExists;
+DEALLOCATE PREPARE addColumnIfNotExists;
+
+SET @preparedStatement2 = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'PostAcknowledgements'
+        AND table_schema = DATABASE()
+        AND column_name = 'ChannelId'
+    ) > 0,
+    'SELECT 1;',
+    'ALTER TABLE PostAcknowledgements ADD COLUMN ChannelId varchar(26) DEFAULT \'\';'
+));
+
+PREPARE addColumnIfNotExists FROM @preparedStatement2;
+EXECUTE addColumnIfNotExists;
+DEALLOCATE PREPARE addColumnIfNotExists;

server/channels/db/migrations/postgres/000141_add_remoteid_channelid_to_post_acknowledgements.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE postacknowledgements DROP COLUMN IF EXISTS remoteid;
+ALTER TABLE postacknowledgements DROP COLUMN IF EXISTS channelid;

server/channels/db/migrations/postgres/000141_add_remoteid_channelid_to_post_acknowledgements.up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE postacknowledgements ADD COLUMN IF NOT EXISTS remoteid VARCHAR(26) DEFAULT '';
+ALTER TABLE postacknowledgements ADD COLUMN IF NOT EXISTS channelid VARCHAR(26) DEFAULT '';

server/channels/store/retrylayer/retrylayer.go

@@ -8570,6 +8570,48 @@ func (s *RetryLayerPostStore) Update(rctx request.CTX, newPost *model.Post, oldP
 
 }
 
+func (s *RetryLayerPostAcknowledgementStore) BatchDelete(acknowledgements []*model.PostAcknowledgement) error {
+
+	tries := 0
+	for {
+		err := s.PostAcknowledgementStore.BatchDelete(acknowledgements)
+		if err == nil {
+			return nil
+		}
+		if !isRepeatableError(err) {
+			return err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
+func (s *RetryLayerPostAcknowledgementStore) BatchSave(acknowledgements []*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error) {
+
+	tries := 0
+	for {
+		result, err := s.PostAcknowledgementStore.BatchSave(acknowledgements)
+		if err == nil {
+			return result, nil
+		}
+		if !isRepeatableError(err) {
+			return result, err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return result, err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
 func (s *RetryLayerPostAcknowledgementStore) Delete(acknowledgement *model.PostAcknowledgement) error {
 
 	tries := 0
@@ -8633,6 +8675,27 @@ func (s *RetryLayerPostAcknowledgementStore) GetForPost(postID string) ([]*model
 
 }
 
+func (s *RetryLayerPostAcknowledgementStore) GetForPostSince(postID string, since int64, excludeRemoteID string, inclDeleted bool) ([]*model.PostAcknowledgement, error) {
+
+	tries := 0
+	for {
+		result, err := s.PostAcknowledgementStore.GetForPostSince(postID, since, excludeRemoteID, inclDeleted)
+		if err == nil {
+			return result, nil
+		}
+		if !isRepeatableError(err) {
+			return result, err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return result, err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
 func (s *RetryLayerPostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.PostAcknowledgement, error) {
 
 	tries := 0
@@ -8654,11 +8717,32 @@ func (s *RetryLayerPostAcknowledgementStore) GetForPosts(postIds []string) ([]*m
 
 }
 
-func (s *RetryLayerPostAcknowledgementStore) Save(postID string, userID string, acknowledgedAt int64) (*model.PostAcknowledgement, error) {
+func (s *RetryLayerPostAcknowledgementStore) GetSingle(userID string, postID string, remoteID string) (*model.PostAcknowledgement, error) {
 
 	tries := 0
 	for {
-		result, err := s.PostAcknowledgementStore.Save(postID, userID, acknowledgedAt)
+		result, err := s.PostAcknowledgementStore.GetSingle(userID, postID, remoteID)
+		if err == nil {
+			return result, nil
+		}
+		if !isRepeatableError(err) {
+			return result, err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return result, err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
+func (s *RetryLayerPostAcknowledgementStore) SaveWithModel(acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, error) {
+
+	tries := 0
+	for {
+		result, err := s.PostAcknowledgementStore.SaveWithModel(acknowledgement)
 		if err == nil {
 			return result, nil
 		}
@@ -8822,6 +8906,27 @@ func (s *RetryLayerPostPersistentNotificationStore) UpdateLastActivity(postIds [
 
 }
 
+func (s *RetryLayerPostPriorityStore) Delete(postID string) error {
+
+	tries := 0
+	for {
+		err := s.PostPriorityStore.Delete(postID)
+		if err == nil {
+			return nil
+		}
+		if !isRepeatableError(err) {
+			return err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
 func (s *RetryLayerPostPriorityStore) GetForPost(postID string) (*model.PostPriority, error) {
 
 	tries := 0
@@ -8864,6 +8969,27 @@ func (s *RetryLayerPostPriorityStore) GetForPosts(ids []string) ([]*model.PostPr
 
 }
 
+func (s *RetryLayerPostPriorityStore) Save(priority *model.PostPriority) (*model.PostPriority, error) {
+
+	tries := 0
+	for {
+		result, err := s.PostPriorityStore.Save(priority)
+		if err == nil {
+			return result, nil
+		}
+		if !isRepeatableError(err) {
+			return result, err
+		}
+		tries++
+		if tries >= 3 {
+			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
+			return result, err
+		}
+		timepkg.Sleep(100 * timepkg.Millisecond)
+	}
+
+}
+
 func (s *RetryLayerPreferenceStore) CleanupFlagsBatch(limit int64) (int64, error) {
 
 	tries := 0

server/channels/store/sqlstore/post_acknowledgements_store.go

@@ -23,7 +23,7 @@ func newSqlPostAcknowledgementStore(sqlStore *SqlStore) store.PostAcknowledgemen
 
 func (s *SqlPostAcknowledgementStore) Get(postID, userID string) (*model.PostAcknowledgement, error) {
 	query := s.getQueryBuilder().
-		Select("PostId", "UserId", "AcknowledgedAt").
+		Select("PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId").
 		From("PostAcknowledgements").
 		Where(sq.And{
 			sq.Eq{"PostId": postID},
@@ -44,38 +44,20 @@ func (s *SqlPostAcknowledgementStore) Get(postID, userID string) (*model.PostAck
 	return &acknowledgement, nil
 }
 
-func (s *SqlPostAcknowledgementStore) Save(postID, userID string, acknowledgedAt int64) (*model.PostAcknowledgement, error) {
-	if acknowledgedAt == 0 {
-		acknowledgedAt = model.GetMillis()
-	}
-
-	acknowledgement := &model.PostAcknowledgement{
-		UserId:         userID,
-		PostId:         postID,
-		AcknowledgedAt: acknowledgedAt,
-	}
-
+func (s *SqlPostAcknowledgementStore) SaveWithModel(acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, error) {
 	if err := acknowledgement.IsValid(); err != nil {
 		return nil, err
 	}
 
+	acknowledgement.PreSave()
+
 	transaction, err := s.GetMaster().Beginx()
 	if err != nil {
 		return nil, errors.Wrap(err, "begin_transaction")
 	}
 	defer finalizeTransactionX(transaction, &err)
 
-	query := s.getQueryBuilder().
-		Insert("PostAcknowledgements").
-		Columns("PostId", "UserId", "AcknowledgedAt").
-		Values(acknowledgement.PostId, acknowledgement.UserId, acknowledgement.AcknowledgedAt)
-
-	if s.DriverName() == model.DatabaseDriverMysql {
-		query = query.SuffixExpr(sq.Expr("ON DUPLICATE KEY UPDATE AcknowledgedAt = ?", acknowledgement.AcknowledgedAt))
-	} else {
-		query = query.SuffixExpr(sq.Expr("ON CONFLICT (postid, userid) DO UPDATE SET AcknowledgedAt = ?", acknowledgement.AcknowledgedAt))
-	}
-
+	query := s.buildUpsertQuery(acknowledgement)
 	_, err = transaction.ExecBuilder(query)
 	if err != nil {
 		return nil, err
@@ -131,7 +113,7 @@ func (s *SqlPostAcknowledgementStore) GetForPost(postID string) ([]*model.PostAc
 	var acknowledgements []*model.PostAcknowledgement
 
 	query := s.getQueryBuilder().
-		Select("PostId", "UserId", "AcknowledgedAt").
+		Select("PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId").
 		From("PostAcknowledgements").
 		Where(sq.And{
 			sq.NotEq{"AcknowledgedAt": 0},
@@ -157,7 +139,7 @@ func (s *SqlPostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.Po
 		}
 
 		query := s.getQueryBuilder().
-			Select("PostId", "UserId", "AcknowledgedAt").
+			Select("PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId").
 			From("PostAcknowledgements").
 			Where(sq.And{
 				sq.Eq{"PostId": postIds[i:j]},
@@ -176,6 +158,89 @@ func (s *SqlPostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.Po
 	return acknowledgements, nil
 }
 
+func (s *SqlPostAcknowledgementStore) GetForPostSince(postID string, since int64, excludeRemoteID string, inclDeleted bool) ([]*model.PostAcknowledgement, error) {
+	var acknowledgements []*model.PostAcknowledgement
+
+	query := s.getQueryBuilder().
+		Select("PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId").
+		From("PostAcknowledgements").
+		Where(sq.Eq{"PostId": postID})
+
+	if !inclDeleted {
+		query = query.Where(sq.NotEq{"AcknowledgedAt": 0})
+	}
+
+	if since > 0 {
+		query = query.Where(sq.Gt{"AcknowledgedAt": since})
+	}
+
+	if excludeRemoteID != "" {
+		query = query.Where(sq.NotEq{"COALESCE(RemoteId, '')": excludeRemoteID})
+	}
+
+	err := s.GetReplica().SelectBuilder(&acknowledgements, query)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to get PostAcknowledgements for postID=%s since=%d", postID, since)
+	}
+
+	return acknowledgements, nil
+}
+
+func (s *SqlPostAcknowledgementStore) GetSingle(userID, postID, remoteID string) (*model.PostAcknowledgement, error) {
+	query := s.getQueryBuilder().
+		Select("PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId").
+		From("PostAcknowledgements").
+		Where(sq.And{
+			sq.Eq{"PostId": postID},
+			sq.Eq{"UserId": userID},
+		})
+
+	if remoteID != "" {
+		query = query.Where(sq.Eq{"RemoteId": remoteID})
+	} else {
+		query = query.Where(sq.Or{
+			sq.Eq{"RemoteId": ""},
+			sq.Eq{"RemoteId": nil},
+		})
+	}
+
+	var acknowledgement model.PostAcknowledgement
+	err := s.GetReplica().GetBuilder(&acknowledgement, query)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, store.NewErrNotFound("PostAcknowledgement", postID)
+		}
+		return nil, err
+	}
+
+	return &acknowledgement, nil
+}
+
+// buildUpsertQuery creates an upsert query for a PostAcknowledgement
+func (s *SqlPostAcknowledgementStore) buildUpsertQuery(acknowledgement *model.PostAcknowledgement) sq.InsertBuilder {
+	columnsToInsert := []string{"PostId", "UserId", "ChannelId", "AcknowledgedAt", "RemoteId"}
+	var remoteIdValue any
+	if acknowledgement.RemoteId != nil {
+		remoteIdValue = *acknowledgement.RemoteId
+	} else {
+		remoteIdValue = nil
+	}
+	valuesToInsert := []any{acknowledgement.PostId, acknowledgement.UserId, acknowledgement.ChannelId, acknowledgement.AcknowledgedAt, remoteIdValue}
+
+	query := s.getQueryBuilder().
+		Insert("PostAcknowledgements").
+		Columns(columnsToInsert...).
+		Values(valuesToInsert...)
+
+	if s.DriverName() == model.DatabaseDriverMysql {
+		query = query.SuffixExpr(sq.Expr("ON DUPLICATE KEY UPDATE AcknowledgedAt = ?", acknowledgement.AcknowledgedAt))
+	} else {
+		query = query.SuffixExpr(sq.Expr("ON CONFLICT (postid, userid) DO UPDATE SET AcknowledgedAt = ?", acknowledgement.AcknowledgedAt))
+	}
+
+	return query
+}
+
 func updatePost(transaction *sqlxTxWrapper, postId string) error {
 	_, err := transaction.Exec(
 		`UPDATE
@@ -190,3 +255,116 @@ func updatePost(transaction *sqlxTxWrapper, postId string) error {
 
 	return err
 }
+
+func (s *SqlPostAcknowledgementStore) BatchSave(acknowledgements []*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error) {
+	if len(acknowledgements) == 0 {
+		return []*model.PostAcknowledgement{}, nil
+	}
+
+	// Populate missing ChannelId fields and validate all acknowledgements
+	for _, ack := range acknowledgements {
+		// If ChannelId is not set, look it up from the post
+		if ack.ChannelId == "" {
+			postQuery := s.getQueryBuilder().
+				Select("ChannelId").
+				From("Posts").
+				Where(sq.Eq{"Id": ack.PostId})
+
+			var channelId string
+			err := s.GetReplica().GetBuilder(&channelId, postQuery)
+			if err != nil {
+				return nil, errors.Wrapf(err, "failed to get channel id for post %s", ack.PostId)
+			}
+			ack.ChannelId = channelId
+		}
+
+		if err := ack.IsValid(); err != nil {
+			return nil, err
+		}
+	}
+
+	transaction, err := s.GetMaster().Beginx()
+	if err != nil {
+		return nil, errors.Wrap(err, "begin_transaction")
+	}
+	defer finalizeTransactionX(transaction, &err)
+
+	// Keep track of which posts need to be updated
+	postsToUpdate := make(map[string]bool)
+
+	// Insert all acknowledgements
+	for _, ack := range acknowledgements {
+		ack.PreSave()
+
+		query := s.buildUpsertQuery(ack)
+		_, err = transaction.ExecBuilder(query)
+		if err != nil {
+			return nil, err
+		}
+
+		postsToUpdate[ack.PostId] = true
+	}
+
+	// Update the UpdateAt timestamp for all affected posts
+	for postID := range postsToUpdate {
+		err = updatePost(transaction, postID)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return nil, errors.Wrap(err, "commit_transaction")
+	}
+
+	return acknowledgements, nil
+}
+
+func (s *SqlPostAcknowledgementStore) BatchDelete(acknowledgements []*model.PostAcknowledgement) error {
+	if len(acknowledgements) == 0 {
+		return nil
+	}
+
+	transaction, err := s.GetMaster().Beginx()
+	if err != nil {
+		return errors.Wrap(err, "begin_transaction")
+	}
+	defer finalizeTransactionX(transaction, &err)
+
+	// Keep track of which posts need to be updated
+	postsToUpdate := make(map[string]bool)
+
+	// Set AcknowledgedAt to 0 for all acknowledgements
+	for _, ack := range acknowledgements {
+		query := s.getQueryBuilder().
+			Update("PostAcknowledgements").
+			Set("AcknowledgedAt", 0).
+			Where(sq.And{
+				sq.Eq{"PostId": ack.PostId},
+				sq.Eq{"UserId": ack.UserId},
+			})
+
+		_, err = transaction.ExecBuilder(query)
+		if err != nil {
+			return err
+		}
+
+		postsToUpdate[ack.PostId] = true
+	}
+
+	// Update the UpdateAt timestamp for all affected posts
+	for postID := range postsToUpdate {
+		err = updatePost(transaction, postID)
+		if err != nil {
+			return err
+		}
+	}
+
+	err = transaction.Commit()
+	if err != nil {
+		return errors.Wrap(err, "commit_transaction")
+	}
+
+	return nil
+}

server/channels/store/sqlstore/post_priority_store.go

@@ -5,6 +5,7 @@ package sqlstore
 
 import (
 	sq "github.com/mattermost/squirrel"
+	"github.com/pkg/errors"
 
 	"github.com/mattermost/mattermost/server/public/model"
 	"github.com/mattermost/mattermost/server/v8/channels/store"
@@ -22,7 +23,7 @@ func newSqlPostPriorityStore(sqlStore *SqlStore) store.PostPriorityStore {
 
 func (s *SqlPostPriorityStore) GetForPost(postId string) (*model.PostPriority, error) {
 	query := s.getQueryBuilder().
-		Select("Priority", "RequestedAck", "PersistentNotifications").
+		Select("PostId", "ChannelId", "Priority", "RequestedAck", "PersistentNotifications").
 		From("PostsPriority").
 		Where(sq.Eq{"PostId": postId})
 
@@ -46,12 +47,12 @@ func (s *SqlPostPriorityStore) GetForPosts(postIds []string) ([]*model.PostPrior
 		}
 
 		query := s.getQueryBuilder().
-			Select("PostId", "Priority", "RequestedAck", "PersistentNotifications").
+			Select("PostId", "ChannelId", "Priority", "RequestedAck", "PersistentNotifications").
 			From("PostsPriority").
 			Where(sq.Eq{"PostId": postIds[i:j]})
 
 		var priorityBatch []*model.PostPriority
-		err := s.GetReplica().SelectBuilder(&priority, query)
+		err := s.GetReplica().SelectBuilder(&priorityBatch, query)
 
 		if err != nil {
 			return nil, err
@@ -62,3 +63,130 @@ func (s *SqlPostPriorityStore) GetForPosts(postIds []string) ([]*model.PostPrior
 
 	return priority, nil
 }
+
+func (s *SqlPostPriorityStore) Save(priority *model.PostPriority) (*model.PostPriority, error) {
+	tx, err := s.GetMaster().Beginx()
+	if err != nil {
+		return nil, errors.Wrap(err, "begin_transaction")
+	}
+	defer finalizeTransactionX(tx, &err)
+
+	// Delete existing priority
+	deleteQuery := s.getQueryBuilder().
+		Delete("PostsPriority").
+		Where(sq.Eq{"PostId": priority.PostId})
+
+	if _, err := tx.ExecBuilder(deleteQuery); err != nil {
+		return nil, errors.Wrap(err, "delete_existing_priority")
+	}
+
+	// Insert new priority
+	insertQuery := s.getQueryBuilder().
+		Insert("PostsPriority").
+		Columns("PostId", "ChannelId", "Priority", "RequestedAck", "PersistentNotifications").
+		Values(priority.PostId, priority.ChannelId, priority.Priority, priority.RequestedAck, priority.PersistentNotifications)
+
+	if _, err := tx.ExecBuilder(insertQuery); err != nil {
+		return nil, errors.Wrap(err, "insert_priority")
+	}
+
+	// Handle persistent notifications - always delete first, then insert if enabled
+	deletePersistentQuery := s.getQueryBuilder().
+		Delete("PersistentNotifications").
+		Where(sq.Eq{"PostId": priority.PostId})
+
+	if _, err := tx.ExecBuilder(deletePersistentQuery); err != nil {
+		return nil, errors.Wrap(err, "delete_persistent_notification")
+	}
+
+	if priority.PersistentNotifications != nil && *priority.PersistentNotifications {
+		insertPersistentQuery := s.getQueryBuilder().
+			Insert("PersistentNotifications").
+			Columns("PostId", "CreateAt", "LastSentAt", "DeleteAt", "SentCount").
+			Values(priority.PostId, model.GetMillis(), 0, 0, 0)
+
+		if _, err := tx.ExecBuilder(insertPersistentQuery); err != nil {
+			return nil, errors.Wrap(err, "insert_persistent_notification")
+		}
+	}
+
+	// Clear acknowledgements if not requested
+	if priority.RequestedAck == nil || !*priority.RequestedAck {
+		clearAckQuery := s.getQueryBuilder().
+			Update("PostAcknowledgements").
+			Set("AcknowledgedAt", 0).
+			Where(sq.Eq{"PostId": priority.PostId})
+
+		if _, err := tx.ExecBuilder(clearAckQuery); err != nil {
+			return nil, errors.Wrap(err, "clear_acknowledgements")
+		}
+	}
+
+	// Update the post's UpdateAt to trigger clients to refresh
+	updatePostQuery := s.getQueryBuilder().
+		Update("Posts").
+		Set("UpdateAt", model.GetMillis()).
+		Where(sq.Eq{"Id": priority.PostId})
+
+	if _, err := tx.ExecBuilder(updatePostQuery); err != nil {
+		return nil, errors.Wrap(err, "update_post")
+	}
+
+	if err := tx.Commit(); err != nil {
+		return nil, errors.Wrap(err, "commit_transaction")
+	}
+
+	return priority, nil
+}
+
+func (s *SqlPostPriorityStore) Delete(postId string) error {
+	tx, err := s.GetMaster().Beginx()
+	if err != nil {
+		return errors.Wrap(err, "begin_transaction")
+	}
+	defer finalizeTransactionX(tx, &err)
+
+	// Delete from PostsPriority
+	deletePriorityQuery := s.getQueryBuilder().
+		Delete("PostsPriority").
+		Where(sq.Eq{"PostId": postId})
+
+	if _, err := tx.ExecBuilder(deletePriorityQuery); err != nil {
+		return errors.Wrap(err, "delete_priority")
+	}
+
+	// Delete from PersistentNotifications
+	deletePersistentQuery := s.getQueryBuilder().
+		Delete("PersistentNotifications").
+		Where(sq.Eq{"PostId": postId})
+
+	if _, err := tx.ExecBuilder(deletePersistentQuery); err != nil {
+		return errors.Wrap(err, "delete_persistent_notification")
+	}
+
+	// Clear acknowledgements
+	clearAckQuery := s.getQueryBuilder().
+		Update("PostAcknowledgements").
+		Set("AcknowledgedAt", 0).
+		Where(sq.Eq{"PostId": postId})
+
+	if _, err := tx.ExecBuilder(clearAckQuery); err != nil {
+		return errors.Wrap(err, "clear_acknowledgements")
+	}
+
+	// Update post
+	updatePostQuery := s.getQueryBuilder().
+		Update("Posts").
+		Set("UpdateAt", model.GetMillis()).
+		Where(sq.Eq{"Id": postId})
+
+	if _, err := tx.ExecBuilder(updatePostQuery); err != nil {
+		return errors.Wrap(err, "update_post")
+	}
+
+	if err := tx.Commit(); err != nil {
+		return errors.Wrap(err, "commit_transaction")
+	}
+
+	return nil
+}

server/channels/store/store.go

@@ -1035,6 +1035,8 @@ type SharedChannelStore interface {
 type PostPriorityStore interface {
 	GetForPost(postID string) (*model.PostPriority, error)
 	GetForPosts(ids []string) ([]*model.PostPriority, error)
+	Save(priority *model.PostPriority) (*model.PostPriority, error)
+	Delete(postID string) error
 }
 
 type DraftStore interface {
@@ -1053,8 +1055,12 @@ type PostAcknowledgementStore interface {
 	Get(postID, userID string) (*model.PostAcknowledgement, error)
 	GetForPost(postID string) ([]*model.PostAcknowledgement, error)
 	GetForPosts(postIds []string) ([]*model.PostAcknowledgement, error)
-	Save(postID, userID string, acknowledgedAt int64) (*model.PostAcknowledgement, error)
+	GetForPostSince(postID string, since int64, excludeRemoteID string, inclDeleted bool) ([]*model.PostAcknowledgement, error)
+	GetSingle(userID, postID, remoteID string) (*model.PostAcknowledgement, error)
+	SaveWithModel(acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, error)
+	BatchSave(acknowledgements []*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error)
 	Delete(acknowledgement *model.PostAcknowledgement) error
+	BatchDelete(acknowledgements []*model.PostAcknowledgement) error
 }
 
 type PostPersistentNotificationStore interface {

server/channels/store/storetest/mocks/PostAcknowledgementStore.go

@@ -14,6 +14,54 @@ type PostAcknowledgementStore struct {
 	mock.Mock
 }
 
+// BatchDelete provides a mock function with given fields: acknowledgements
+func (_m *PostAcknowledgementStore) BatchDelete(acknowledgements []*model.PostAcknowledgement) error {
+	ret := _m.Called(acknowledgements)
+
+	if len(ret) == 0 {
+		panic("no return value specified for BatchDelete")
+	}
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func([]*model.PostAcknowledgement) error); ok {
+		r0 = rf(acknowledgements)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// BatchSave provides a mock function with given fields: acknowledgements
+func (_m *PostAcknowledgementStore) BatchSave(acknowledgements []*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error) {
+	ret := _m.Called(acknowledgements)
+
+	if len(ret) == 0 {
+		panic("no return value specified for BatchSave")
+	}
+
+	var r0 []*model.PostAcknowledgement
+	var r1 error
+	if rf, ok := ret.Get(0).(func([]*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error)); ok {
+		return rf(acknowledgements)
+	}
+	if rf, ok := ret.Get(0).(func([]*model.PostAcknowledgement) []*model.PostAcknowledgement); ok {
+		r0 = rf(acknowledgements)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func([]*model.PostAcknowledgement) error); ok {
+		r1 = rf(acknowledgements)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // Delete provides a mock function with given fields: acknowledgement
 func (_m *PostAcknowledgementStore) Delete(acknowledgement *model.PostAcknowledgement) error {
 	ret := _m.Called(acknowledgement)
@@ -92,6 +140,36 @@ func (_m *PostAcknowledgementStore) GetForPost(postID string) ([]*model.PostAckn
 	return r0, r1
 }
 
+// GetForPostSince provides a mock function with given fields: postID, since, excludeRemoteID, inclDeleted
+func (_m *PostAcknowledgementStore) GetForPostSince(postID string, since int64, excludeRemoteID string, inclDeleted bool) ([]*model.PostAcknowledgement, error) {
+	ret := _m.Called(postID, since, excludeRemoteID, inclDeleted)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetForPostSince")
+	}
+
+	var r0 []*model.PostAcknowledgement
+	var r1 error
+	if rf, ok := ret.Get(0).(func(string, int64, string, bool) ([]*model.PostAcknowledgement, error)); ok {
+		return rf(postID, since, excludeRemoteID, inclDeleted)
+	}
+	if rf, ok := ret.Get(0).(func(string, int64, string, bool) []*model.PostAcknowledgement); ok {
+		r0 = rf(postID, since, excludeRemoteID, inclDeleted)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(string, int64, string, bool) error); ok {
+		r1 = rf(postID, since, excludeRemoteID, inclDeleted)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // GetForPosts provides a mock function with given fields: postIds
 func (_m *PostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.PostAcknowledgement, error) {
 	ret := _m.Called(postIds)
@@ -122,29 +200,59 @@ func (_m *PostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.Post
 	return r0, r1
 }
 
-// Save provides a mock function with given fields: postID, userID, acknowledgedAt
-func (_m *PostAcknowledgementStore) Save(postID string, userID string, acknowledgedAt int64) (*model.PostAcknowledgement, error) {
-	ret := _m.Called(postID, userID, acknowledgedAt)
+// GetSingle provides a mock function with given fields: userID, postID, remoteID
+func (_m *PostAcknowledgementStore) GetSingle(userID string, postID string, remoteID string) (*model.PostAcknowledgement, error) {
+	ret := _m.Called(userID, postID, remoteID)
 
 	if len(ret) == 0 {
-		panic("no return value specified for Save")
+		panic("no return value specified for GetSingle")
 	}
 
 	var r0 *model.PostAcknowledgement
 	var r1 error
-	if rf, ok := ret.Get(0).(func(string, string, int64) (*model.PostAcknowledgement, error)); ok {
-		return rf(postID, userID, acknowledgedAt)
+	if rf, ok := ret.Get(0).(func(string, string, string) (*model.PostAcknowledgement, error)); ok {
+		return rf(userID, postID, remoteID)
 	}
-	if rf, ok := ret.Get(0).(func(string, string, int64) *model.PostAcknowledgement); ok {
-		r0 = rf(postID, userID, acknowledgedAt)
+	if rf, ok := ret.Get(0).(func(string, string, string) *model.PostAcknowledgement); ok {
+		r0 = rf(userID, postID, remoteID)
 	} else {
 		if ret.Get(0) != nil {
 			r0 = ret.Get(0).(*model.PostAcknowledgement)
 		}
 	}
 
-	if rf, ok := ret.Get(1).(func(string, string, int64) error); ok {
-		r1 = rf(postID, userID, acknowledgedAt)
+	if rf, ok := ret.Get(1).(func(string, string, string) error); ok {
+		r1 = rf(userID, postID, remoteID)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// SaveWithModel provides a mock function with given fields: acknowledgement
+func (_m *PostAcknowledgementStore) SaveWithModel(acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, error) {
+	ret := _m.Called(acknowledgement)
+
+	if len(ret) == 0 {
+		panic("no return value specified for SaveWithModel")
+	}
+
+	var r0 *model.PostAcknowledgement
+	var r1 error
+	if rf, ok := ret.Get(0).(func(*model.PostAcknowledgement) (*model.PostAcknowledgement, error)); ok {
+		return rf(acknowledgement)
+	}
+	if rf, ok := ret.Get(0).(func(*model.PostAcknowledgement) *model.PostAcknowledgement); ok {
+		r0 = rf(acknowledgement)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(*model.PostAcknowledgement) error); ok {
+		r1 = rf(acknowledgement)
 	} else {
 		r1 = ret.Error(1)
 	}

server/channels/store/storetest/mocks/PostPriorityStore.go

@@ -14,6 +14,24 @@ type PostPriorityStore struct {
 	mock.Mock
 }
 
+// Delete provides a mock function with given fields: postID
+func (_m *PostPriorityStore) Delete(postID string) error {
+	ret := _m.Called(postID)
+
+	if len(ret) == 0 {
+		panic("no return value specified for Delete")
+	}
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(string) error); ok {
+		r0 = rf(postID)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
 // GetForPost provides a mock function with given fields: postID
 func (_m *PostPriorityStore) GetForPost(postID string) (*model.PostPriority, error) {
 	ret := _m.Called(postID)
@@ -74,6 +92,36 @@ func (_m *PostPriorityStore) GetForPosts(ids []string) ([]*model.PostPriority, e
 	return r0, r1
 }
 
+// Save provides a mock function with given fields: priority
+func (_m *PostPriorityStore) Save(priority *model.PostPriority) (*model.PostPriority, error) {
+	ret := _m.Called(priority)
+
+	if len(ret) == 0 {
+		panic("no return value specified for Save")
+	}
+
+	var r0 *model.PostPriority
+	var r1 error
+	if rf, ok := ret.Get(0).(func(*model.PostPriority) (*model.PostPriority, error)); ok {
+		return rf(priority)
+	}
+	if rf, ok := ret.Get(0).(func(*model.PostPriority) *model.PostPriority); ok {
+		r0 = rf(priority)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.PostPriority)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(*model.PostPriority) error); ok {
+		r1 = rf(priority)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // NewPostPriorityStore creates a new instance of PostPriorityStore. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
 // The first argument is typically a *testing.T value.
 func NewPostPriorityStore(t interface {

server/channels/store/storetest/post_acknowledgements_store.go

@@ -17,6 +17,8 @@ func TestPostAcknowledgementsStore(t *testing.T, rctx request.CTX, ss store.Stor
 	t.Run("Save", func(t *testing.T) { testPostAcknowledgementsStoreSave(t, rctx, ss) })
 	t.Run("GetForPost", func(t *testing.T) { testPostAcknowledgementsStoreGetForPost(t, rctx, ss) })
 	t.Run("GetForPosts", func(t *testing.T) { testPostAcknowledgementsStoreGetForPosts(t, rctx, ss) })
+	t.Run("BatchSave", func(t *testing.T) { testPostAcknowledgementsStoreBatchSave(t, rctx, ss) })
+	t.Run("BatchDelete", func(t *testing.T) { testPostAcknowledgementsStoreBatchDelete(t, rctx, ss) })
 }
 
 func testPostAcknowledgementsStoreSave(t *testing.T, rctx request.CTX, ss store.Store) {
@@ -37,13 +39,16 @@ func testPostAcknowledgementsStoreSave(t *testing.T, rctx request.CTX, ss store.
 	require.NoError(t, err)
 
 	t.Run("consecutive saves should just update the acknowledged at", func(t *testing.T) {
-		_, err := ss.PostAcknowledgement().Save(post.Id, userID1, 0)
+		ack := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		_, err := ss.PostAcknowledgement().SaveWithModel(ack)
 		require.NoError(t, err)
 
-		_, err = ss.PostAcknowledgement().Save(post.Id, userID1, 0)
+		ack = &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		_, err = ss.PostAcknowledgement().SaveWithModel(ack)
 		require.NoError(t, err)
 
-		ack1, err := ss.PostAcknowledgement().Save(post.Id, userID1, 0)
+		ack1 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack1, err = ss.PostAcknowledgement().SaveWithModel(ack1)
 		require.NoError(t, err)
 
 		acknowledgements, err := ss.PostAcknowledgement().GetForPost(post.Id)
@@ -53,7 +58,8 @@ func testPostAcknowledgementsStoreSave(t *testing.T, rctx request.CTX, ss store.
 
 	t.Run("saving should update the update at of the post", func(t *testing.T) {
 		oldUpdateAt := post.UpdateAt
-		_, err := ss.PostAcknowledgement().Save(post.Id, userID1, 0)
+		ack := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		_, err := ss.PostAcknowledgement().SaveWithModel(ack)
 		require.NoError(t, err)
 
 		post, err = ss.Post().GetSingle(rctx, post.Id, false)
@@ -82,11 +88,14 @@ func testPostAcknowledgementsStoreGetForPost(t *testing.T, rctx request.CTX, ss
 	require.NoError(t, err)
 
 	t.Run("get acknowledgements for post", func(t *testing.T) {
-		ack1, err := ss.PostAcknowledgement().Save(p1.Id, userID1, 0)
+		ack1 := &model.PostAcknowledgement{PostId: p1.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: p1.ChannelId}
+		ack1, err := ss.PostAcknowledgement().SaveWithModel(ack1)
 		require.NoError(t, err)
-		ack2, err := ss.PostAcknowledgement().Save(p1.Id, userID2, 0)
+		ack2 := &model.PostAcknowledgement{PostId: p1.Id, UserId: userID2, AcknowledgedAt: 0, ChannelId: p1.ChannelId}
+		ack2, err = ss.PostAcknowledgement().SaveWithModel(ack2)
 		require.NoError(t, err)
-		ack3, err := ss.PostAcknowledgement().Save(p1.Id, userID3, 0)
+		ack3 := &model.PostAcknowledgement{PostId: p1.Id, UserId: userID3, AcknowledgedAt: 0, ChannelId: p1.ChannelId}
+		ack3, err = ss.PostAcknowledgement().SaveWithModel(ack3)
 		require.NoError(t, err)
 
 		acknowledgements, err := ss.PostAcknowledgement().GetForPost(p1.Id)
@@ -145,13 +154,17 @@ func testPostAcknowledgementsStoreGetForPosts(t *testing.T, rctx request.CTX, ss
 	require.Equal(t, -1, errIdx)
 
 	t.Run("get acknowledgements for post", func(t *testing.T) {
-		ack1, err := ss.PostAcknowledgement().Save(p1.Id, userID1, 0)
+		ack1 := &model.PostAcknowledgement{PostId: p1.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: p1.ChannelId}
+		ack1, err := ss.PostAcknowledgement().SaveWithModel(ack1)
 		require.NoError(t, err)
-		ack2, err := ss.PostAcknowledgement().Save(p1.Id, userID2, 0)
+		ack2 := &model.PostAcknowledgement{PostId: p1.Id, UserId: userID2, AcknowledgedAt: 0, ChannelId: p1.ChannelId}
+		ack2, err = ss.PostAcknowledgement().SaveWithModel(ack2)
 		require.NoError(t, err)
-		ack3, err := ss.PostAcknowledgement().Save(p2.Id, userID2, 0)
+		ack3 := &model.PostAcknowledgement{PostId: p2.Id, UserId: userID2, AcknowledgedAt: 0, ChannelId: p2.ChannelId}
+		ack3, err = ss.PostAcknowledgement().SaveWithModel(ack3)
 		require.NoError(t, err)
-		ack4, err := ss.PostAcknowledgement().Save(p2.Id, userID3, 0)
+		ack4 := &model.PostAcknowledgement{PostId: p2.Id, UserId: userID3, AcknowledgedAt: 0, ChannelId: p2.ChannelId}
+		ack4, err = ss.PostAcknowledgement().SaveWithModel(ack4)
 		require.NoError(t, err)
 
 		acknowledgements, err := ss.PostAcknowledgement().GetForPosts([]string{p1.Id})
@@ -191,3 +204,218 @@ func testPostAcknowledgementsStoreGetForPosts(t *testing.T, rctx request.CTX, ss
 		require.Empty(t, acknowledgements)
 	})
 }
+
+func testPostAcknowledgementsStoreBatchSave(t *testing.T, rctx request.CTX, ss store.Store) {
+	userID1 := model.NewId()
+	userID2 := model.NewId()
+	userID3 := model.NewId()
+
+	p1 := model.Post{}
+	p1.ChannelId = model.NewId()
+	p1.UserId = model.NewId()
+	p1.Message = NewTestID()
+	post, err := ss.Post().Save(rctx, &p1)
+	require.NoError(t, err)
+
+	t.Run("batch save acknowledgements for a post", func(t *testing.T) {
+		// Create a batch of acknowledgements
+		acks := []*model.PostAcknowledgement{
+			{
+				PostId:         post.Id,
+				UserId:         userID1,
+				AcknowledgedAt: model.GetMillis(),
+			},
+			{
+				PostId:         post.Id,
+				UserId:         userID2,
+				AcknowledgedAt: model.GetMillis(),
+			},
+			{
+				PostId:         post.Id,
+				UserId:         userID3,
+				AcknowledgedAt: model.GetMillis(),
+			},
+		}
+
+		// Save the batch
+		savedAcks, err := ss.PostAcknowledgement().BatchSave(acks)
+		require.NoError(t, err)
+		require.Len(t, savedAcks, 3)
+
+		// Verify all were saved correctly
+		retrievedAcks, err := ss.PostAcknowledgement().GetForPost(post.Id)
+		require.NoError(t, err)
+		require.Len(t, retrievedAcks, 3)
+
+		// Verify all users are in the saved acknowledgements
+		userIDMap := make(map[string]bool)
+		for _, ack := range retrievedAcks {
+			userIDMap[ack.UserId] = true
+			require.Equal(t, post.Id, ack.PostId)
+			require.Greater(t, ack.AcknowledgedAt, int64(0))
+		}
+
+		require.True(t, userIDMap[userID1])
+		require.True(t, userIDMap[userID2])
+		require.True(t, userIDMap[userID3])
+	})
+
+	t.Run("batch save empty list of acknowledgements", func(t *testing.T) {
+		// Create an empty batch of acknowledgements
+		acks := []*model.PostAcknowledgement{}
+
+		// Save the empty batch
+		savedAcks, err := ss.PostAcknowledgement().BatchSave(acks)
+		require.NoError(t, err)
+		require.Empty(t, savedAcks)
+	})
+
+	t.Run("batch save should update existing acknowledgements", func(t *testing.T) {
+		// First, delete all existing acknowledgements
+		acks, err := ss.PostAcknowledgement().GetForPost(post.Id)
+		require.NoError(t, err)
+
+		for _, ack := range acks {
+			err = ss.PostAcknowledgement().Delete(ack)
+			require.NoError(t, err)
+		}
+
+		// Create initial acknowledgement
+		ack := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: model.GetMillis(), ChannelId: post.ChannelId}
+		ack, err = ss.PostAcknowledgement().SaveWithModel(ack)
+		require.NoError(t, err)
+
+		initialAckTime := ack.AcknowledgedAt
+
+		// Create a batch with updated timestamp
+		newTimestamp := model.GetMillis() + 1000
+		updatedAcks := []*model.PostAcknowledgement{
+			{
+				PostId:         post.Id,
+				UserId:         userID1,
+				AcknowledgedAt: newTimestamp,
+			},
+		}
+
+		// Batch save should update the existing acknowledgement
+		savedAcks, err := ss.PostAcknowledgement().BatchSave(updatedAcks)
+		require.NoError(t, err)
+		require.Len(t, savedAcks, 1)
+		require.Equal(t, newTimestamp, savedAcks[0].AcknowledgedAt)
+		require.Greater(t, savedAcks[0].AcknowledgedAt, initialAckTime)
+
+		// Verify the acknowledgement was updated
+		retrievedAcks, err := ss.PostAcknowledgement().GetForPost(post.Id)
+		require.NoError(t, err)
+		require.Len(t, retrievedAcks, 1)
+		require.Equal(t, newTimestamp, retrievedAcks[0].AcknowledgedAt)
+	})
+
+	t.Run("batch save should update post's update_at", func(t *testing.T) {
+		// First, check the current post update timestamp
+		currentPost, err := ss.Post().GetSingle(rctx, post.Id, false)
+		require.NoError(t, err)
+		oldUpdateAt := currentPost.UpdateAt
+
+		// Create a batch of new acknowledgements
+		acks := []*model.PostAcknowledgement{
+			{
+				PostId:         post.Id,
+				UserId:         model.NewId(),
+				AcknowledgedAt: model.GetMillis(),
+			},
+		}
+
+		// Save the batch
+		_, err = ss.PostAcknowledgement().BatchSave(acks)
+		require.NoError(t, err)
+
+		// Verify post's update_at was updated
+		updatedPost, err := ss.Post().GetSingle(rctx, post.Id, false)
+		require.NoError(t, err)
+		require.Greater(t, updatedPost.UpdateAt, oldUpdateAt)
+	})
+}
+
+func testPostAcknowledgementsStoreBatchDelete(t *testing.T, rctx request.CTX, ss store.Store) {
+	userID1 := model.NewId()
+	userID2 := model.NewId()
+	userID3 := model.NewId()
+
+	p1 := model.Post{}
+	p1.ChannelId = model.NewId()
+	p1.UserId = model.NewId()
+	p1.Message = NewTestID()
+	post, err := ss.Post().Save(rctx, &p1)
+	require.NoError(t, err)
+
+	t.Run("batch delete all acknowledgements for a post", func(t *testing.T) {
+		// Create multiple acknowledgements
+		ack1 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack1, err = ss.PostAcknowledgement().SaveWithModel(ack1)
+		require.NoError(t, err)
+		ack2 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID2, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack2, err = ss.PostAcknowledgement().SaveWithModel(ack2)
+		require.NoError(t, err)
+		ack3 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID3, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack3, err = ss.PostAcknowledgement().SaveWithModel(ack3)
+		require.NoError(t, err)
+
+		// Verify acknowledgements were created
+		acks, pErr := ss.PostAcknowledgement().GetForPost(post.Id)
+		require.NoError(t, pErr)
+		require.Len(t, acks, 3)
+
+		// Delete all acknowledgements in batch
+		err = ss.PostAcknowledgement().BatchDelete([]*model.PostAcknowledgement{ack1, ack2, ack3})
+		require.NoError(t, err)
+
+		// Verify all acknowledgements were deleted
+		acks, err = ss.PostAcknowledgement().GetForPost(post.Id)
+		require.NoError(t, err)
+		require.Empty(t, acks)
+	})
+
+	t.Run("batch delete should update post's update_at", func(t *testing.T) {
+		// Create acknowledgements
+		ack1 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID1, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack1, err = ss.PostAcknowledgement().SaveWithModel(ack1)
+		require.NoError(t, err)
+		ack2 := &model.PostAcknowledgement{PostId: post.Id, UserId: userID2, AcknowledgedAt: 0, ChannelId: post.ChannelId}
+		ack2, err = ss.PostAcknowledgement().SaveWithModel(ack2)
+		require.NoError(t, err)
+
+		// Get current post update timestamp
+		currentPost, err := ss.Post().GetSingle(rctx, post.Id, false)
+		require.NoError(t, err)
+		oldUpdateAt := currentPost.UpdateAt
+
+		// Delete acknowledgements in batch
+		err = ss.PostAcknowledgement().BatchDelete([]*model.PostAcknowledgement{ack1, ack2})
+		require.NoError(t, err)
+
+		// Verify post's update_at was updated
+		updatedPost, err := ss.Post().GetSingle(rctx, post.Id, false)
+		require.NoError(t, err)
+		require.Greater(t, updatedPost.UpdateAt, oldUpdateAt)
+	})
+
+	t.Run("batch delete with empty list should not error", func(t *testing.T) {
+		// Delete with empty list should not error
+		err := ss.PostAcknowledgement().BatchDelete([]*model.PostAcknowledgement{})
+		require.NoError(t, err)
+	})
+
+	t.Run("batch delete with non-existent acknowledgements should not error", func(t *testing.T) {
+		// Create non-existent acknowledgements
+		nonExistentAck := &model.PostAcknowledgement{
+			PostId:         model.NewId(),
+			UserId:         model.NewId(),
+			AcknowledgedAt: model.GetMillis(),
+		}
+
+		// Delete non-existent acknowledgement should not error
+		err := ss.PostAcknowledgement().BatchDelete([]*model.PostAcknowledgement{nonExistentAck})
+		require.NoError(t, err)
+	})
+}

server/channels/store/timerlayer/timerlayer.go

@@ -6821,6 +6821,38 @@ func (s *TimerLayerPostStore) Update(rctx request.CTX, newPost *model.Post, oldP
 	return result, err
 }
 
+func (s *TimerLayerPostAcknowledgementStore) BatchDelete(acknowledgements []*model.PostAcknowledgement) error {
+	start := time.Now()
+
+	err := s.PostAcknowledgementStore.BatchDelete(acknowledgements)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.BatchDelete", success, elapsed)
+	}
+	return err
+}
+
+func (s *TimerLayerPostAcknowledgementStore) BatchSave(acknowledgements []*model.PostAcknowledgement) ([]*model.PostAcknowledgement, error) {
+	start := time.Now()
+
+	result, err := s.PostAcknowledgementStore.BatchSave(acknowledgements)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.BatchSave", success, elapsed)
+	}
+	return result, err
+}
+
 func (s *TimerLayerPostAcknowledgementStore) Delete(acknowledgement *model.PostAcknowledgement) error {
 	start := time.Now()
 
@@ -6869,6 +6901,22 @@ func (s *TimerLayerPostAcknowledgementStore) GetForPost(postID string) ([]*model
 	return result, err
 }
 
+func (s *TimerLayerPostAcknowledgementStore) GetForPostSince(postID string, since int64, excludeRemoteID string, inclDeleted bool) ([]*model.PostAcknowledgement, error) {
+	start := time.Now()
+
+	result, err := s.PostAcknowledgementStore.GetForPostSince(postID, since, excludeRemoteID, inclDeleted)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.GetForPostSince", success, elapsed)
+	}
+	return result, err
+}
+
 func (s *TimerLayerPostAcknowledgementStore) GetForPosts(postIds []string) ([]*model.PostAcknowledgement, error) {
 	start := time.Now()
 
@@ -6885,10 +6933,10 @@ func (s *TimerLayerPostAcknowledgementStore) GetForPosts(postIds []string) ([]*m
 	return result, err
 }
 
-func (s *TimerLayerPostAcknowledgementStore) Save(postID string, userID string, acknowledgedAt int64) (*model.PostAcknowledgement, error) {
+func (s *TimerLayerPostAcknowledgementStore) GetSingle(userID string, postID string, remoteID string) (*model.PostAcknowledgement, error) {
 	start := time.Now()
 
-	result, err := s.PostAcknowledgementStore.Save(postID, userID, acknowledgedAt)
+	result, err := s.PostAcknowledgementStore.GetSingle(userID, postID, remoteID)
 
 	elapsed := float64(time.Since(start)) / float64(time.Second)
 	if s.Root.Metrics != nil {
@@ -6896,7 +6944,23 @@ func (s *TimerLayerPostAcknowledgementStore) Save(postID string, userID string,
 		if err == nil {
 			success = "true"
 		}
-		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.Save", success, elapsed)
+		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.GetSingle", success, elapsed)
+	}
+	return result, err
+}
+
+func (s *TimerLayerPostAcknowledgementStore) SaveWithModel(acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, error) {
+	start := time.Now()
+
+	result, err := s.PostAcknowledgementStore.SaveWithModel(acknowledgement)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostAcknowledgementStore.SaveWithModel", success, elapsed)
 	}
 	return result, err
 }
@@ -7013,6 +7077,22 @@ func (s *TimerLayerPostPersistentNotificationStore) UpdateLastActivity(postIds [
 	return err
 }
 
+func (s *TimerLayerPostPriorityStore) Delete(postID string) error {
+	start := time.Now()
+
+	err := s.PostPriorityStore.Delete(postID)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostPriorityStore.Delete", success, elapsed)
+	}
+	return err
+}
+
 func (s *TimerLayerPostPriorityStore) GetForPost(postID string) (*model.PostPriority, error) {
 	start := time.Now()
 
@@ -7045,6 +7125,22 @@ func (s *TimerLayerPostPriorityStore) GetForPosts(ids []string) ([]*model.PostPr
 	return result, err
 }
 
+func (s *TimerLayerPostPriorityStore) Save(priority *model.PostPriority) (*model.PostPriority, error) {
+	start := time.Now()
+
+	result, err := s.PostPriorityStore.Save(priority)
+
+	elapsed := float64(time.Since(start)) / float64(time.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if err == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("PostPriorityStore.Save", success, elapsed)
+	}
+	return result, err
+}
+
 func (s *TimerLayerPreferenceStore) CleanupFlagsBatch(limit int64) (int64, error) {
 	start := time.Now()
 

server/i18n/en.json

@@ -4506,10 +4506,18 @@
     "id": "api4.plugin.reattachPlugin.invalid_request",
     "translation": "Failed to parse request"
   },
+  {
+    "id": "app.acknowledgement.batch_save.app_error",
+    "translation": "Failed to save the batch of acknowledgement objects"
+  },
   {
     "id": "app.acknowledgement.delete.app_error",
     "translation": "Unable to delete acknowledgement."
   },
+  {
+    "id": "app.acknowledgement.delete.missing_post.app_error",
+    "translation": "Cannot delete acknowledgement for missing post"
+  },
   {
     "id": "app.acknowledgement.get.app_error",
     "translation": "Unable to get acknowledgement."
@@ -4518,6 +4526,10 @@
     "id": "app.acknowledgement.getforpost.get.app_error",
     "translation": "Unable to get acknowledgement for post."
   },
+  {
+    "id": "app.acknowledgement.save.missing_post.app_error",
+    "translation": "Cannot save acknowledgement for missing post"
+  },
   {
     "id": "app.acknowledgement.save.save.app_error",
     "translation": "Unable to save acknowledgement for post."
@@ -8752,6 +8764,10 @@
     "id": "model.access_policy.is_valid.version.app_error",
     "translation": "Version is not valid for this access control policy."
   },
+  {
+    "id": "model.acknowledgement.is_valid.channel_id.app_error",
+    "translation": "Invalid channel id."
+  },
   {
     "id": "model.acknowledgement.is_valid.post_id.app_error",
     "translation": "Invalid post id."

server/platform/services/sharedchannel/mock_AppIface_test.go

@@ -205,6 +205,26 @@ func (_m *MockAppIface) CreateUploadSession(c request.CTX, us *model.UploadSessi
 	return r0, r1
 }
 
+// DeleteAcknowledgementForPostWithModel provides a mock function with given fields: c, acknowledgement
+func (_m *MockAppIface) DeleteAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) *model.AppError {
+	ret := _m.Called(c, acknowledgement)
+
+	if len(ret) == 0 {
+		panic("no return value specified for DeleteAcknowledgementForPostWithModel")
+	}
+
+	var r0 *model.AppError
+	if rf, ok := ret.Get(0).(func(request.CTX, *model.PostAcknowledgement) *model.AppError); ok {
+		r0 = rf(c, acknowledgement)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.AppError)
+		}
+	}
+
+	return r0
+}
+
 // DeletePost provides a mock function with given fields: c, postID, deleteByID
 func (_m *MockAppIface) DeletePost(c request.CTX, postID string, deleteByID string) (*model.Post, *model.AppError) {
 	ret := _m.Called(c, postID, deleteByID)
@@ -289,6 +309,38 @@ func (_m *MockAppIface) FileReader(path string) (filestore.ReadCloseSeeker, *mod
 	return r0, r1
 }
 
+// GetAcknowledgementsForPost provides a mock function with given fields: postID
+func (_m *MockAppIface) GetAcknowledgementsForPost(postID string) ([]*model.PostAcknowledgement, *model.AppError) {
+	ret := _m.Called(postID)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetAcknowledgementsForPost")
+	}
+
+	var r0 []*model.PostAcknowledgement
+	var r1 *model.AppError
+	if rf, ok := ret.Get(0).(func(string) ([]*model.PostAcknowledgement, *model.AppError)); ok {
+		return rf(postID)
+	}
+	if rf, ok := ret.Get(0).(func(string) []*model.PostAcknowledgement); ok {
+		r0 = rf(postID)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(string) *model.AppError); ok {
+		r1 = rf(postID)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
 // GetOrCreateDirectChannel provides a mock function with given fields: c, userId, otherUserId, channelOptions
 func (_m *MockAppIface) GetOrCreateDirectChannel(c request.CTX, userId string, otherUserId string, channelOptions ...model.ChannelOption) (*model.Channel, *model.AppError) {
 	_va := make([]interface{}, len(channelOptions))
@@ -508,6 +560,26 @@ func (_m *MockAppIface) PermanentDeleteChannel(c request.CTX, channel *model.Cha
 	return r0
 }
 
+// PreparePostForClient provides a mock function with given fields: c, post, isNewPost, includeDeleted, includePriority
+func (_m *MockAppIface) PreparePostForClient(c request.CTX, post *model.Post, isNewPost bool, includeDeleted bool, includePriority bool) *model.Post {
+	ret := _m.Called(c, post, isNewPost, includeDeleted, includePriority)
+
+	if len(ret) == 0 {
+		panic("no return value specified for PreparePostForClient")
+	}
+
+	var r0 *model.Post
+	if rf, ok := ret.Get(0).(func(request.CTX, *model.Post, bool, bool, bool) *model.Post); ok {
+		r0 = rf(c, post, isNewPost, includeDeleted, includePriority)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.Post)
+		}
+	}
+
+	return r0
+}
+
 // Publish provides a mock function with given fields: message
 func (_m *MockAppIface) Publish(message *model.WebSocketEvent) {
 	_m.Called(message)
@@ -533,6 +605,70 @@ func (_m *MockAppIface) RemoveUserFromChannel(c request.CTX, userID string, remo
 	return r0
 }
 
+// SaveAcknowledgementForPostWithModel provides a mock function with given fields: c, acknowledgement
+func (_m *MockAppIface) SaveAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, *model.AppError) {
+	ret := _m.Called(c, acknowledgement)
+
+	if len(ret) == 0 {
+		panic("no return value specified for SaveAcknowledgementForPostWithModel")
+	}
+
+	var r0 *model.PostAcknowledgement
+	var r1 *model.AppError
+	if rf, ok := ret.Get(0).(func(request.CTX, *model.PostAcknowledgement) (*model.PostAcknowledgement, *model.AppError)); ok {
+		return rf(c, acknowledgement)
+	}
+	if rf, ok := ret.Get(0).(func(request.CTX, *model.PostAcknowledgement) *model.PostAcknowledgement); ok {
+		r0 = rf(c, acknowledgement)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(request.CTX, *model.PostAcknowledgement) *model.AppError); ok {
+		r1 = rf(c, acknowledgement)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
+// SaveAcknowledgementsForPost provides a mock function with given fields: c, postID, userIDs
+func (_m *MockAppIface) SaveAcknowledgementsForPost(c request.CTX, postID string, userIDs []string) ([]*model.PostAcknowledgement, *model.AppError) {
+	ret := _m.Called(c, postID, userIDs)
+
+	if len(ret) == 0 {
+		panic("no return value specified for SaveAcknowledgementsForPost")
+	}
+
+	var r0 []*model.PostAcknowledgement
+	var r1 *model.AppError
+	if rf, ok := ret.Get(0).(func(request.CTX, string, []string) ([]*model.PostAcknowledgement, *model.AppError)); ok {
+		return rf(c, postID, userIDs)
+	}
+	if rf, ok := ret.Get(0).(func(request.CTX, string, []string) []*model.PostAcknowledgement); ok {
+		r0 = rf(c, postID, userIDs)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*model.PostAcknowledgement)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(request.CTX, string, []string) *model.AppError); ok {
+		r1 = rf(c, postID, userIDs)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
 // SaveAndBroadcastStatus provides a mock function with given fields: status
 func (_m *MockAppIface) SaveAndBroadcastStatus(status *model.Status) {
 	_m.Called(status)

server/platform/services/sharedchannel/service.go

@@ -78,6 +78,11 @@ type AppIface interface {
 	OnSharedChannelsAttachmentSyncMsg(fi *model.FileInfo, post *model.Post, rc *model.RemoteCluster) error
 	OnSharedChannelsProfileImageSyncMsg(user *model.User, rc *model.RemoteCluster) error
 	Publish(message *model.WebSocketEvent)
+	SaveAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) (*model.PostAcknowledgement, *model.AppError)
+	DeleteAcknowledgementForPostWithModel(c request.CTX, acknowledgement *model.PostAcknowledgement) *model.AppError
+	SaveAcknowledgementsForPost(c request.CTX, postID string, userIDs []string) ([]*model.PostAcknowledgement, *model.AppError)
+	GetAcknowledgementsForPost(postID string) ([]*model.PostAcknowledgement, *model.AppError)
+	PreparePostForClient(c request.CTX, post *model.Post, isNewPost, includeDeleted, includePriority bool) *model.Post
 }
 
 // errNotFound allows checking against Store.ErrNotFound errors without making Store a dependency.

server/platform/services/sharedchannel/sync_recv.go

@@ -82,10 +82,11 @@ func (scs *Service) processSyncMessage(c request.CTX, syncMsg *model.SyncMsg, rc
 
 	var err error
 	syncResp := model.SyncResponse{
-		UserErrors:     make([]string, 0),
-		UsersSyncd:     make([]string, 0),
-		PostErrors:     make([]string, 0),
-		ReactionErrors: make([]string, 0),
+		UserErrors:            make([]string, 0),
+		UsersSyncd:            make([]string, 0),
+		PostErrors:            make([]string, 0),
+		ReactionErrors:        make([]string, 0),
+		AcknowledgementErrors: make([]string, 0),
 	}
 
 	// Check if feature flag is enabled for membership changes
@@ -103,6 +104,7 @@ func (scs *Service) processSyncMessage(c request.CTX, syncMsg *model.SyncMsg, rc
 		mlog.Int("user_count", len(syncMsg.Users)),
 		mlog.Int("post_count", len(syncMsg.Posts)),
 		mlog.Int("reaction_count", len(syncMsg.Reactions)),
+		mlog.Int("acknowledgement_count", len(syncMsg.Acknowledgements)),
 		mlog.Int("status_count", len(syncMsg.Statuses)),
 		mlog.Int("membership_change_count", len(syncMsg.MembershipChanges)),
 	)
@@ -234,6 +236,31 @@ func (scs *Service) processSyncMessage(c request.CTX, syncMsg *model.SyncMsg, rc
 		}
 	}
 
+	// add/remove acknowledgements
+	for _, acknowledgement := range syncMsg.Acknowledgements {
+		if _, err := scs.upsertSyncAcknowledgement(acknowledgement, targetChannel, rc); err != nil {
+			scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Error upserting sync acknowledgement",
+				mlog.String("remote", rc.Name),
+				mlog.String("user_id", acknowledgement.UserId),
+				mlog.String("post_id", acknowledgement.PostId),
+				mlog.Int("acknowledged_at", acknowledgement.AcknowledgedAt),
+				mlog.Err(err),
+			)
+			syncResp.AcknowledgementErrors = append(syncResp.AcknowledgementErrors, acknowledgement.PostId)
+		} else {
+			scs.server.Log().Log(mlog.LvlSharedChannelServiceDebug, "Acknowledgement upserted via sync",
+				mlog.String("remote", rc.Name),
+				mlog.String("user_id", acknowledgement.UserId),
+				mlog.String("post_id", acknowledgement.PostId),
+				mlog.Int("acknowledged_at", acknowledgement.AcknowledgedAt),
+			)
+
+			if syncResp.AcknowledgementsLastUpdateAt < acknowledgement.AcknowledgedAt {
+				syncResp.AcknowledgementsLastUpdateAt = acknowledgement.AcknowledgedAt
+			}
+		}
+	}
+
 	for _, status := range syncMsg.Statuses {
 		scs.app.SaveAndBroadcastStatus(status)
 	}
@@ -431,7 +458,6 @@ func (scs *Service) upsertSyncPost(post *model.Post, targetChannel *model.Channe
 
 	post.RemoteId = model.NewPointer(rc.RemoteId)
 	rctx := request.EmptyContext(scs.server.Log())
-
 	rpost, err := scs.server.GetStore().Post().GetSingle(rctx, post.Id, true)
 	if err != nil {
 		if _, ok := err.(errNotFound); !ok {
@@ -460,8 +486,7 @@ func (scs *Service) upsertSyncPost(post *model.Post, targetChannel *model.Channe
 		if appErr == nil {
 			scs.server.Log().Log(mlog.LvlSharedChannelServiceDebug, "Created sync post",
 				mlog.String("post_id", post.Id),
-				mlog.String("channel_id", post.ChannelId),
-			)
+				mlog.String("channel_id", post.ChannelId))
 		}
 	} else if post.DeleteAt > 0 {
 		// delete post
@@ -472,14 +497,37 @@ func (scs *Service) upsertSyncPost(post *model.Post, targetChannel *model.Channe
 				mlog.String("channel_id", post.ChannelId),
 			)
 		}
-	} else if post.EditAt > rpost.EditAt || post.Message != rpost.Message {
-		// update post
-		rpost, appErr = scs.app.UpdatePost(request.EmptyContext(scs.server.Log()), post, nil)
-		if appErr == nil {
-			scs.server.Log().Log(mlog.LvlSharedChannelServiceDebug, "Updated sync post",
-				mlog.String("post_id", post.Id),
-				mlog.String("channel_id", post.ChannelId),
-			)
+	} else if post.EditAt > rpost.EditAt || post.Message != rpost.Message || post.UpdateAt > rpost.UpdateAt || post.Metadata != nil {
+		var priority *model.PostPriority
+		var acknowledgements []*model.PostAcknowledgement
+
+		if post.Metadata != nil {
+			// Save the received priority
+			if post.Metadata.Priority != nil {
+				priority = post.Metadata.Priority
+			}
+
+			// Save the received acknowledgements
+			if post.Metadata.Acknowledgements != nil {
+				acknowledgements = post.Metadata.Acknowledgements
+			}
+		}
+
+		// First update the basic post
+		rpost, appErr = scs.app.UpdatePost(rctx, post, nil)
+		if appErr != nil {
+			rerr := errors.New(appErr.Error())
+			return nil, rerr
+		}
+
+		// Handle priority metadata separately if needed
+		if priority != nil {
+			rpost = scs.syncRemotePriorityMetadata(rctx, post, priority, rpost)
+		}
+
+		// Handle acknowledgements metadata separately if needed
+		if acknowledgements != nil {
+			rpost = scs.syncRemoteAcknowledgementsMetadata(rctx, post, acknowledgements, rpost)
 		}
 	} else {
 		// nothing to update
@@ -496,6 +544,105 @@ func (scs *Service) upsertSyncPost(post *model.Post, targetChannel *model.Channe
 	return rpost, rerr
 }
 
+// syncRemotePriorityMetadata handles syncing priority metadata from a remote post.
+// It completely replaces existing priority settings with the ones from the remote post,
+// regardless of update type.
+func (scs *Service) syncRemotePriorityMetadata(rctx request.CTX, post *model.Post, priority *model.PostPriority, rpost *model.Post) *model.Post {
+	// First, create a new priority object with proper post and channel IDs
+	newPriority := &model.PostPriority{
+		PostId:    post.Id,
+		ChannelId: post.ChannelId,
+	}
+
+	// Copy the priority values from the remote post
+	if priority.Priority != nil {
+		newPriority.Priority = priority.Priority
+	}
+
+	if priority.RequestedAck != nil {
+		newPriority.RequestedAck = priority.RequestedAck
+	}
+
+	if priority.PersistentNotifications != nil {
+		newPriority.PersistentNotifications = priority.PersistentNotifications
+	}
+
+	// Save the new priority - this will replace any existing priority for the post
+	savedPriority, priorityErr := scs.server.GetStore().PostPriority().Save(newPriority)
+	if priorityErr != nil {
+		scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Error saving post priority from remote",
+			mlog.String("post_id", post.Id),
+			mlog.String("channel_id", post.ChannelId),
+			mlog.Err(priorityErr),
+		)
+	} else {
+		// If the priority is successfully saved, ensure it's in the returned post
+		if rpost.Metadata == nil {
+			rpost.Metadata = &model.PostMetadata{}
+		}
+		// Use the saved priority from the database operation
+		rpost.Metadata.Priority = savedPriority
+	}
+
+	return rpost
+}
+
+// syncRemoteAcknowledgementsMetadata handles syncing acknowledgements metadata from a remote post.
+// It replaces all existing acknowledgements with the ones from the remote post.
+func (scs *Service) syncRemoteAcknowledgementsMetadata(rctx request.CTX, post *model.Post, acknowledgements []*model.PostAcknowledgement, rpost *model.Post) *model.Post {
+	// When syncing from remote, we completely replace the existing acknowledgements
+	// with the ones received from the remote, regardless of update type
+
+	// Get existing acknowledgements and delete them using batch operation
+	existingAcks, appErrGet := scs.app.GetAcknowledgementsForPost(post.Id)
+	if appErrGet != nil {
+		scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Error getting existing acknowledgements for remote sync",
+			mlog.String("post_id", post.Id),
+			mlog.Err(appErrGet),
+		)
+	} else if len(existingAcks) > 0 {
+		// Use batch delete for better performance
+		if nErr := scs.server.GetStore().PostAcknowledgement().BatchDelete(existingAcks); nErr != nil {
+			scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Error batch deleting acknowledgements for remote sync",
+				mlog.String("post_id", post.Id),
+				mlog.Int("count", len(existingAcks)),
+				mlog.Err(nErr),
+			)
+		}
+	}
+
+	// Extract all user IDs from acknowledgements for batch processing
+	userIDs := make([]string, 0, len(acknowledgements))
+	for _, ack := range acknowledgements {
+		userIDs = append(userIDs, ack.UserId)
+	}
+
+	// Use batch operation to save all acknowledgements at once
+	var savedAcks []*model.PostAcknowledgement
+
+	if len(userIDs) > 0 {
+		var appErrAck *model.AppError
+		savedAcks, appErrAck = scs.app.SaveAcknowledgementsForPost(rctx, post.Id, userIDs)
+		if appErrAck != nil {
+			scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Error syncing remote post acknowledgements",
+				mlog.String("post_id", post.Id),
+				mlog.Int("count", len(userIDs)),
+				mlog.Err(appErrAck),
+			)
+			// Fall back to original acknowledgements if batch save fails
+			savedAcks = acknowledgements
+		}
+	}
+
+	// Update acknowledgements in the returned post
+	if rpost.Metadata == nil {
+		rpost.Metadata = &model.PostMetadata{}
+	}
+	rpost.Metadata.Acknowledgements = savedAcks
+
+	return rpost
+}
+
 func (scs *Service) upsertSyncReaction(reaction *model.Reaction, targetChannel *model.Channel, rc *model.RemoteCluster) (*model.Reaction, error) {
 	savedReaction := reaction
 	var appErr *model.AppError
@@ -542,3 +689,54 @@ func (scs *Service) upsertSyncReaction(reaction *model.Reaction, targetChannel *
 	}
 	return savedReaction, retErr
 }
+
+func (scs *Service) upsertSyncAcknowledgement(acknowledgement *model.PostAcknowledgement, targetChannel *model.Channel, rc *model.RemoteCluster) (*model.PostAcknowledgement, error) {
+	savedAcknowledgement := acknowledgement
+	var appErr *model.AppError
+
+	// check that the acknowledgement's post is in the target channel. This ensures the acknowledgement can only be associated with a post
+	// that is in a channel shared with the remote.
+	rctx := request.EmptyContext(scs.server.Log())
+	post, err := scs.server.GetStore().Post().GetSingle(rctx, acknowledgement.PostId, true)
+	if err != nil {
+		return nil, fmt.Errorf("error fetching post for acknowledgement sync: %w", err)
+	}
+	if post.ChannelId != targetChannel.Id {
+		return nil, fmt.Errorf("acknowledgement sync failed: %w", ErrChannelIDMismatch)
+	}
+
+	existingAcknowledgement, err := scs.server.GetStore().PostAcknowledgement().GetSingle(acknowledgement.UserId, acknowledgement.PostId, rc.RemoteId)
+	if err != nil && !isNotFoundError(err) {
+		return nil, fmt.Errorf("error fetching acknowledgement for sync: %w", err)
+	}
+
+	if existingAcknowledgement == nil {
+		// acknowledgement does not exist; check that user belongs to remote and create acknowledgement
+		// this is not done for delete since deletion can be done by admins on the remote
+		user, err := scs.server.GetStore().User().Get(context.TODO(), acknowledgement.UserId)
+		if err != nil {
+			return nil, fmt.Errorf("error fetching user for acknowledgement sync: %w", err)
+		}
+		if user.GetRemoteID() != rc.RemoteId {
+			return nil, fmt.Errorf("acknowledgement sync failed: %w", ErrRemoteIDMismatch)
+		}
+		acknowledgement.RemoteId = model.NewPointer(rc.RemoteId)
+		acknowledgement.ChannelId = targetChannel.Id
+		savedAcknowledgement, appErr = scs.app.SaveAcknowledgementForPostWithModel(request.EmptyContext(scs.server.Log()), acknowledgement)
+	} else {
+		// make sure the acknowledgement being deleted is owned by the remote
+		if existingAcknowledgement.GetRemoteID() != rc.RemoteId {
+			return nil, fmt.Errorf("acknowledgement sync failed: %w", ErrRemoteIDMismatch)
+		}
+		if acknowledgement.AcknowledgedAt == 0 {
+			// Delete the acknowledgement
+			appErr = scs.app.DeleteAcknowledgementForPostWithModel(request.EmptyContext(scs.server.Log()), acknowledgement)
+		}
+	}
+
+	var retErr error
+	if appErr != nil {
+		retErr = errors.New(appErr.Error())
+	}
+	return savedAcknowledgement, retErr
+}

server/platform/services/sharedchannel/sync_send.go

@@ -469,6 +469,9 @@ func (scs *Service) handlePostError(postId string, task syncTask, rc *model.Remo
 		return
 	}
 
+	// Populate metadata for the retry post
+	post = scs.app.PreparePostForClient(request.EmptyContext(scs.server.Log()), post, false, false, true)
+
 	syncMsg := model.NewSyncMsg(task.channelID)
 	syncMsg.Posts = []*model.Post{post}
 

server/platform/services/sharedchannel/sync_send_remote.go

@@ -32,12 +32,13 @@ type syncData struct {
 	rc   *model.RemoteCluster
 	scr  *model.SharedChannelRemote
 
-	users         map[string]*model.User
-	profileImages map[string]*model.User
-	posts         []*model.Post
-	reactions     []*model.Reaction
-	statuses      []*model.Status
-	attachments   []attachment
+	users            map[string]*model.User
+	profileImages    map[string]*model.User
+	posts            []*model.Post
+	reactions        []*model.Reaction
+	acknowledgements []*model.PostAcknowledgement
+	statuses         []*model.Status
+	attachments      []attachment
 
 	resultRepeat                bool
 	resultNextCursor            model.GetPostsSinceForSyncCursor
@@ -59,7 +60,7 @@ func newSyncData(task syncTask, rc *model.RemoteCluster, scr *model.SharedChanne
 }
 
 func (sd *syncData) isEmpty() bool {
-	return len(sd.users) == 0 && len(sd.profileImages) == 0 && len(sd.posts) == 0 && len(sd.reactions) == 0 && len(sd.attachments) == 0
+	return len(sd.users) == 0 && len(sd.profileImages) == 0 && len(sd.posts) == 0 && len(sd.reactions) == 0 && len(sd.acknowledgements) == 0 && len(sd.attachments) == 0
 }
 
 func (sd *syncData) isCursorChanged() bool {
@@ -75,6 +76,7 @@ func (sd *syncData) setDataFromMsg(msg *model.SyncMsg) {
 	sd.users = msg.Users
 	sd.posts = msg.Posts
 	sd.reactions = msg.Reactions
+	sd.acknowledgements = msg.Acknowledgements
 	sd.statuses = msg.Statuses
 }
 
@@ -185,6 +187,11 @@ func (scs *Service) syncForRemote(task syncTask, rc *model.RemoteCluster) error
 		return fmt.Errorf("cannot fetch reactions for sync %v: %w", sd, err)
 	}
 
+	// fetch acknowledgements for posts
+	if err := scs.fetchAcknowledgementsForSync(sd); err != nil {
+		return fmt.Errorf("cannot fetch acknowledgements for sync %v: %w", sd, err)
+	}
+
 	// fetch users associated with posts & reactions
 	if err := scs.fetchPostUsersForSync(sd); err != nil {
 		return fmt.Errorf("cannot fetch post users for sync %v: %w", sd, err)
@@ -218,6 +225,7 @@ func (scs *Service) syncForRemote(task syncTask, rc *model.RemoteCluster) error
 		mlog.Int("images", len(sd.profileImages)),
 		mlog.Int("posts", len(sd.posts)),
 		mlog.Int("reactions", len(sd.reactions)),
+		mlog.Int("acknowledgements", len(sd.acknowledgements)),
 		mlog.Int("attachments", len(sd.attachments)),
 	)
 
@@ -319,6 +327,13 @@ func (scs *Service) fetchPostsForSync(sd *syncData) error {
 		sd.posts = appendPosts(sd.posts, posts, scs.server.GetStore().Post(), cursor.LastPostUpdateAt, scs.server.Log())
 	}
 
+	// Populate metadata for all posts before syncing
+	for i, post := range sd.posts {
+		if post != nil {
+			sd.posts[i] = scs.app.PreparePostForClient(request.EmptyContext(scs.server.Log()), post, false, false, true)
+		}
+	}
+
 	sd.resultNextCursor = nextCursor
 	sd.resultRepeat = count >= maxPostsPerSync
 
@@ -377,6 +392,28 @@ func (scs *Service) fetchReactionsForSync(sd *syncData) error {
 	return merr.ErrorOrNil()
 }
 
+// fetchAcknowledgementsForSync populates the sync data with any new acknowledgements since the last sync.
+func (scs *Service) fetchAcknowledgementsForSync(sd *syncData) error {
+	start := time.Now()
+	defer func() {
+		if metrics := scs.server.GetMetrics(); metrics != nil {
+			metrics.ObserveSharedChannelsSyncCollectionStepDuration(sd.rc.RemoteId, "Acknowledgements", time.Since(start).Seconds())
+		}
+	}()
+
+	merr := merror.New()
+	for _, post := range sd.posts {
+		// any acknowledgements originating from the remote cluster are filtered out
+		acknowledgements, err := scs.server.GetStore().PostAcknowledgement().GetForPostSince(post.Id, sd.scr.LastPostUpdateAt, sd.rc.RemoteId, true)
+		if err != nil {
+			merr.Append(fmt.Errorf("could not get acknowledgements for post %s: %w", post.Id, err))
+			continue
+		}
+		sd.acknowledgements = append(sd.acknowledgements, acknowledgements...)
+	}
+	return merr.ErrorOrNil()
+}
+
 // fetchPostUsersForSync populates the sync data with all users associated with posts.
 func (scs *Service) fetchPostUsersForSync(sd *syncData) error {
 	start := time.Now()
@@ -402,6 +439,10 @@ func (scs *Service) fetchPostUsersForSync(sd *syncData) error {
 		userIDs[reaction.UserId] = p2mm{}
 	}
 
+	for _, acknowledgement := range sd.acknowledgements {
+		userIDs[acknowledgement.UserId] = p2mm{}
+	}
+
 	for _, post := range sd.posts {
 		// add author
 		userIDs[post.UserId] = p2mm{}
@@ -495,7 +536,9 @@ func (scs *Service) filterPostsForSync(sd *syncData) {
 		//   - new posts (EditAt == 0)
 		//   - edited posts (EditAt >= LastPostUpdateAt)
 		//   - deleted posts (DeleteAt > 0)
-		if p.EditAt > 0 && p.EditAt < sd.scr.LastPostUpdateAt && p.DeleteAt == 0 {
+		//   - posts with metadata changes (acknowledgements/priority)
+		hasMetadataChanges := p.Metadata != nil && (p.Metadata.Acknowledgements != nil || p.Metadata.Priority != nil)
+		if p.EditAt > 0 && p.EditAt < sd.scr.LastPostUpdateAt && p.DeleteAt == 0 && !hasMetadataChanges {
 			continue
 		}
 
@@ -514,6 +557,7 @@ func (scs *Service) filterPostsForSync(sd *syncData) {
 
 		filtered = append(filtered, p)
 	}
+
 	sd.posts = filtered
 }
 
@@ -552,6 +596,13 @@ func (scs *Service) sendSyncData(sd *syncData) error {
 		scs.updateCursorForRemote(sd.scr.Id, sd.rc, sd.resultNextCursor)
 	}
 
+	// send acknowledgements
+	if len(sd.acknowledgements) != 0 {
+		if err := scs.sendAcknowledgementSyncData(sd); err != nil {
+			merr.Append(fmt.Errorf("cannot send acknowledgement sync data: %w", err))
+		}
+	}
+
 	// send reactions
 	if len(sd.reactions) != 0 {
 		if err := scs.sendReactionSyncData(sd); err != nil {
@@ -679,6 +730,29 @@ func (scs *Service) sendReactionSyncData(sd *syncData) error {
 	})
 }
 
+// sendAcknowledgementSyncData sends the collected acknowledgement updates to the remote cluster.
+func (scs *Service) sendAcknowledgementSyncData(sd *syncData) error {
+	start := time.Now()
+	defer func() {
+		if metrics := scs.server.GetMetrics(); metrics != nil {
+			metrics.ObserveSharedChannelsSyncSendStepDuration(sd.rc.RemoteId, "Acknowledgements", time.Since(start).Seconds())
+		}
+	}()
+
+	msg := model.NewSyncMsg(sd.task.channelID)
+	msg.Acknowledgements = sd.acknowledgements
+
+	return scs.sendSyncMsgToRemote(msg, sd.rc, func(syncResp model.SyncResponse, errResp error) {
+		if len(syncResp.AcknowledgementErrors) != 0 {
+			scs.server.Log().Log(mlog.LvlSharedChannelServiceError, "Response indicates error for acknowledgement(s) sync",
+				mlog.String("channel_id", sd.task.channelID),
+				mlog.String("remote_id", sd.rc.RemoteId),
+				mlog.Array("acknowledgement_posts", syncResp.AcknowledgementErrors),
+			)
+		}
+	})
+}
+
 // sendStatusSyncData sends the collected status updates to the remote cluster.
 func (scs *Service) sendStatusSyncData(sd *syncData) error {
 	msg := model.NewSyncMsg(sd.task.channelID)

server/public/model/post_acknowledgement.go

@@ -6,9 +6,11 @@ package model
 import "net/http"
 
 type PostAcknowledgement struct {
-	UserId         string `json:"user_id"`
-	PostId         string `json:"post_id"`
-	AcknowledgedAt int64  `json:"acknowledged_at"`
+	UserId         string  `json:"user_id"`
+	PostId         string  `json:"post_id"`
+	AcknowledgedAt int64   `json:"acknowledged_at"`
+	ChannelId      string  `json:"channel_id"`
+	RemoteId       *string `json:"remote_id,omitempty"`
 }
 
 func (o *PostAcknowledgement) IsValid() *AppError {
@@ -20,5 +22,22 @@ func (o *PostAcknowledgement) IsValid() *AppError {
 		return NewAppError("PostAcknowledgement.IsValid", "model.acknowledgement.is_valid.post_id.app_error", nil, "post_id="+o.PostId, http.StatusBadRequest)
 	}
 
+	if !IsValidId(o.ChannelId) {
+		return NewAppError("PostAcknowledgement.IsValid", "model.acknowledgement.is_valid.channel_id.app_error", nil, "channel_id="+o.ChannelId, http.StatusBadRequest)
+	}
+
 	return nil
 }
+
+func (o *PostAcknowledgement) GetRemoteID() string {
+	if o.RemoteId != nil {
+		return *o.RemoteId
+	}
+	return ""
+}
+
+func (o *PostAcknowledgement) PreSave() {
+	if o.AcknowledgedAt == 0 {
+		o.AcknowledgedAt = GetMillis()
+	}
+}

server/public/model/shared_channel.go

@@ -291,6 +291,7 @@ type SyncMsg struct {
 	Reactions         []*Reaction            `json:"reactions,omitempty"`
 	Statuses          []*Status              `json:"statuses,omitempty"`
 	MembershipChanges []*MembershipChangeMsg `json:"membership_changes,omitempty"`
+	Acknowledgements  []*PostAcknowledgement `json:"acknowledgements,omitempty"`
 }
 
 func NewSyncMsg(channelID string) *SyncMsg {
@@ -328,6 +329,9 @@ type SyncResponse struct {
 	ReactionsLastUpdateAt int64    `json:"reactions_last_update_at"`
 	ReactionErrors        []string `json:"reaction_errors"`
 
+	AcknowledgementsLastUpdateAt int64    `json:"acknowledgements_last_update_at"`
+	AcknowledgementErrors        []string `json:"acknowledgement_errors"`
+
 	StatusErrors []string `json:"status_errors"` // user IDs for which the status sync failed
 }