feat: Phase 7 — Marmot group chat UI & ViewModel layer

Add complete UI layer for Marmot Protocol MLS group messaging:

State models (commons/commonMain/):
- MarmotGroupChatroom: tracks decrypted inner messages per group
- MarmotGroupList: manages all group chatrooms with change notifications
- MarmotGroupFeedFilter: feed filter for group message feeds
- MarmotGroupFeedViewModel: ViewModel exposing group messages

Account integration:
- Add marmotGroupList to IAccount interface and implementations
- GroupEventHandler indexes inner events into MarmotGroupList
- AccountViewModel gains sendMarmotGroupMessage, createMarmotGroup,
  publishMarmotKeyPackage helper methods

Android screens (amethyst/):
- MarmotGroupListScreen: lists all groups with last message preview
- MarmotGroupChatScreen: group conversation with message composer
- MarmotGroupChatView: message feed + simple text composer
- CreateGroupDialog: create new MLS group with display name
- AddMemberDialog: add member by npub/hex (KeyPackage fetch TBD)

Navigation & integration:
- Route.MarmotGroupList and Route.MarmotGroupChat routes
- Wired into AppNavigation nav graph
- "MLS Groups" button added to ChannelFabColumn on Messages screen
- Marmot group newest messages appear in ChatroomListKnownFeedFilter

https://claude.ai/code/session_0194SxKfAU61PY92eqP4cCXM

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -376,6 +376,9 @@ class Account(
     val draftsDecryptionCache = DraftEventCache(signer)
 
     override val chatroomList = cache.getOrCreateChatroomList(signer.pubKey)
+    override val marmotGroupList =
+        com.vitorpamplona.amethyst.commons.model.marmotGroups
+            .MarmotGroupList()
 
     val newNotesPreProcessor = EventProcessor(this, cache)
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/AppNavigation.kt

@@ -71,6 +71,8 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.list.metadat
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipManagement.ArticleBookmarkListManagementScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.membershipManagement.PostBookmarkListManagementScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.bookmarkgroups.old.OldBookmarkListScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupChatScreen
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup.MarmotGroupListScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.ChatroomByAuthorScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.ChatroomScreen
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.privateDM.send.NewGroupDMScreen
@@ -282,6 +284,9 @@ fun BuildNavigation(
         composableFromEndArgs<Route.Room> { ChatroomScreen(it.toKey(), it.message, it.replyId, it.draftId, it.expiresDays, accountViewModel, nav) }
         composableFromEndArgs<Route.RoomByAuthor> { ChatroomByAuthorScreen(it.id, null, accountViewModel, nav) }
 
+        composableFromEnd<Route.MarmotGroupList> { MarmotGroupListScreen(accountViewModel, nav) }
+        composableFromEndArgs<Route.MarmotGroupChat> { MarmotGroupChatScreen(it.nostrGroupId, accountViewModel, nav) }
+
         composableFromEndArgs<Route.PublicChatChannel> {
             PublicChatChannelScreen(it.id, it.draftId, it.replyTo, accountViewModel, nav)
         }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/routes/Routes.kt

@@ -263,6 +263,12 @@ sealed class Route {
         val id: String? = null,
     ) : Route()
 
+    @Serializable object MarmotGroupList : Route()
+
+    @Serializable data class MarmotGroupChat(
+        val nostrGroupId: String,
+    ) : Route()
+
     @Serializable data class NewGroupDM(
         val message: String? = null,
         val attachment: String? = null,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountViewModel.kt

@@ -1440,6 +1440,30 @@ class AccountViewModel(
         }
     }
 
+    // --- Marmot Group Messaging ---
+
+    suspend fun sendMarmotGroupMessage(
+        nostrGroupId: String,
+        text: String,
+    ) {
+        val template =
+            com.vitorpamplona.quartz.nip01Core.signers.eventTemplate<com.vitorpamplona.quartz.nip01Core.core.Event>(
+                kind = 9,
+                description = text,
+            )
+        val innerEvent = account.signer.sign<com.vitorpamplona.quartz.nip01Core.core.Event>(template)
+        val relays = account.outboxRelays.flow.value
+        account.sendMarmotGroupMessage(nostrGroupId, innerEvent, relays)
+    }
+
+    suspend fun createMarmotGroup(nostrGroupId: String) {
+        account.createMarmotGroup(nostrGroupId)
+    }
+
+    suspend fun publishMarmotKeyPackage() {
+        account.publishMarmotKeyPackage()
+    }
+
     override fun onCleared() {
         Log.d("AccountViewModel", "onCleared")
         callController?.cleanup()

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/DecryptAndIndexProcessor.kt

@@ -475,6 +475,9 @@ class GroupEventHandler(
                     if (cache.justConsume(innerEvent, null, false)) {
                         val innerNote = cache.getOrCreateNote(innerEvent.id)
                         innerNote.event = innerEvent
+
+                        // Track the message in the Marmot group chatroom
+                        account.marmotGroupList.addMessage(result.groupId, innerNote)
                     }
                 }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/AddMemberDialog.kt

@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip19Bech32.Nip19Parser
+import com.vitorpamplona.quartz.nip19Bech32.entities.NProfile
+import com.vitorpamplona.quartz.nip19Bech32.entities.NPub
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+
+@Composable
+fun AddMemberDialog(
+    nostrGroupId: HexKey,
+    accountViewModel: AccountViewModel,
+    onDismiss: () -> Unit,
+) {
+    var memberInput by remember { mutableStateOf("") }
+    var statusMessage by remember { mutableStateOf<String?>(null) }
+    var isAdding by remember { mutableStateOf(false) }
+    val scope = rememberCoroutineScope()
+
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Add Member") },
+        text = {
+            Column {
+                OutlinedTextField(
+                    value = memberInput,
+                    onValueChange = {
+                        memberInput = it
+                        statusMessage = null
+                    },
+                    label = { Text("npub or hex pubkey") },
+                    modifier = Modifier.fillMaxWidth(),
+                    singleLine = true,
+                )
+                Text(
+                    "Enter the member's npub or hex public key. " +
+                        "They must have published a KeyPackage (kind:30443) to be added.",
+                    modifier = Modifier.padding(top = 8.dp),
+                    style = MaterialTheme.typography.bodySmall,
+                )
+                if (statusMessage != null) {
+                    Text(
+                        text = statusMessage!!,
+                        modifier = Modifier.padding(top = 8.dp),
+                        style = MaterialTheme.typography.bodySmall,
+                        color =
+                            if (statusMessage!!.startsWith("Error")) {
+                                MaterialTheme.colorScheme.error
+                            } else {
+                                MaterialTheme.colorScheme.primary
+                            },
+                    )
+                }
+            }
+        },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    isAdding = true
+                    statusMessage = "Looking up KeyPackage..."
+                    scope.launch(Dispatchers.IO) {
+                        try {
+                            val pubkey = resolvePubkey(memberInput)
+                            if (pubkey == null) {
+                                statusMessage = "Error: Invalid public key format"
+                                isAdding = false
+                                return@launch
+                            }
+                            statusMessage = "Fetching KeyPackage for ${pubkey.take(8)}..."
+                            // TODO: Fetch KeyPackage from relays and call addMarmotGroupMember
+                            // For now, show that the flow would proceed here
+                            statusMessage = "Error: KeyPackage fetch not yet implemented. " +
+                                "The member's KeyPackage (kind:30443) must be fetched from relays."
+                            isAdding = false
+                        } catch (e: Exception) {
+                            statusMessage = "Error: ${e.message}"
+                            isAdding = false
+                        }
+                    }
+                },
+                enabled = !isAdding && memberInput.isNotBlank(),
+            ) {
+                Text(if (isAdding) "Adding..." else "Add")
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) {
+                Text("Cancel")
+            }
+        },
+    )
+}
+
+private fun resolvePubkey(input: String): HexKey? {
+    val trimmed = input.trim()
+
+    // Try hex pubkey
+    if (trimmed.length == 64 && trimmed.all { it in '0'..'9' || it in 'a'..'f' }) {
+        return trimmed
+    }
+
+    // Try bech32 (npub / nprofile)
+    val entity =
+        Nip19Parser.uriToRoute("nostr:$trimmed")?.entity
+            ?: Nip19Parser.uriToRoute(trimmed)?.entity
+    return when (entity) {
+        is NPub -> entity.hex
+        is NProfile -> entity.hex
+        else -> null
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/CreateGroupDialog.kt

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlin.random.Random
+
+@Composable
+fun CreateGroupDialog(
+    accountViewModel: AccountViewModel,
+    onDismiss: () -> Unit,
+    onGroupCreated: (HexKey) -> Unit,
+) {
+    var groupName by remember { mutableStateOf("") }
+    var isCreating by remember { mutableStateOf(false) }
+    val scope = rememberCoroutineScope()
+
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Create Marmot Group") },
+        text = {
+            Column {
+                OutlinedTextField(
+                    value = groupName,
+                    onValueChange = { groupName = it },
+                    label = { Text("Group Name") },
+                    modifier = Modifier.fillMaxWidth(),
+                    singleLine = true,
+                )
+                Text(
+                    "A new MLS group will be created. You can add members after.",
+                    modifier = Modifier.padding(top = 8.dp),
+                    style = androidx.compose.material3.MaterialTheme.typography.bodySmall,
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    isCreating = true
+                    scope.launch(Dispatchers.IO) {
+                        val nostrGroupId = Random.nextBytes(32).joinToString("") { "%02x".format(it) }
+                        accountViewModel.createMarmotGroup(nostrGroupId)
+                        // Set display name locally
+                        if (groupName.isNotBlank()) {
+                            accountViewModel.account.marmotGroupList
+                                .getOrCreateGroup(nostrGroupId)
+                                .displayName.value = groupName
+                        }
+                        onGroupCreated(nostrGroupId)
+                    }
+                },
+                enabled = !isCreating,
+            ) {
+                Text(if (isCreating) "Creating..." else "Create")
+            }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) {
+                Text("Cancel")
+            }
+        },
+    )
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupChatScreen.kt

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.consumeWindowInsets
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.statusBarsPadding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.GroupAdd
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun MarmotGroupChatScreen(
+    nostrGroupId: HexKey,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val chatroom =
+        remember(nostrGroupId) {
+            accountViewModel.account.marmotGroupList.getOrCreateGroup(nostrGroupId)
+        }
+    val displayName by chatroom.displayName.collectAsStateWithLifecycle()
+    val memberCount by chatroom.memberCount.collectAsStateWithLifecycle()
+    var showAddMemberDialog by remember { mutableStateOf(false) }
+
+    DisappearingScaffold(
+        isInvertedLayout = true,
+        topBar = {
+            TopAppBar(
+                navigationIcon = {
+                    IconButton(onClick = { nav.popBack() }) {
+                        Icon(
+                            imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                            contentDescription = "Back",
+                        )
+                    }
+                },
+                title = {
+                    Column {
+                        Text(displayName ?: "Marmot Group")
+                        if (memberCount > 0) {
+                            Text(
+                                text = "$memberCount members",
+                                style = androidx.compose.material3.MaterialTheme.typography.bodySmall,
+                            )
+                        }
+                    }
+                },
+                actions = {
+                    IconButton(onClick = { showAddMemberDialog = true }) {
+                        Icon(
+                            imageVector = Icons.Default.GroupAdd,
+                            contentDescription = "Add Member",
+                        )
+                    }
+                },
+            )
+        },
+        accountViewModel = accountViewModel,
+    ) {
+        Column(Modifier.padding(it).consumeWindowInsets(it).statusBarsPadding()) {
+            MarmotGroupChatView(
+                nostrGroupId = nostrGroupId,
+                accountViewModel = accountViewModel,
+                nav = nav,
+            )
+        }
+    }
+
+    if (showAddMemberDialog) {
+        AddMemberDialog(
+            nostrGroupId = nostrGroupId,
+            accountViewModel = accountViewModel,
+            onDismiss = { showAddMemberDialog = false },
+        )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupChatView.kt

@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.text.input.TextFieldState
+import androidx.compose.foundation.text.input.clearText
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.Send
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.vitorpamplona.amethyst.ui.feeds.WatchLifecycleAndUpdateModel
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.feed.RefreshingChatroomFeedView
+import com.vitorpamplona.amethyst.ui.theme.DoubleVertSpacer
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+
+@Composable
+fun MarmotGroupChatView(
+    nostrGroupId: HexKey,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val feedViewModel: MarmotGroupFeedViewModel =
+        viewModel(
+            key = nostrGroupId + "MarmotGroupFeedViewModel",
+            factory =
+                MarmotGroupFeedViewModel.Factory(
+                    nostrGroupId,
+                    accountViewModel.account,
+                ),
+        )
+
+    WatchLifecycleAndUpdateModel(feedViewModel)
+
+    Column(Modifier.fillMaxHeight()) {
+        Column(
+            modifier =
+                Modifier
+                    .fillMaxHeight()
+                    .padding(vertical = 0.dp)
+                    .weight(1f, true),
+        ) {
+            RefreshingChatroomFeedView(
+                feedContentState = feedViewModel.feedState,
+                accountViewModel = accountViewModel,
+                nav = nav,
+                routeForLastRead = "MarmotGroup/$nostrGroupId",
+                onWantsToReply = { },
+                onWantsToEditDraft = { },
+            )
+        }
+
+        Spacer(modifier = DoubleVertSpacer)
+
+        MarmotGroupMessageComposer(
+            nostrGroupId = nostrGroupId,
+            accountViewModel = accountViewModel,
+            onMessageSent = {
+                feedViewModel.feedState.sendToTop()
+            },
+        )
+    }
+}
+
+@Composable
+fun MarmotGroupMessageComposer(
+    nostrGroupId: HexKey,
+    accountViewModel: AccountViewModel,
+    onMessageSent: suspend () -> Unit,
+) {
+    val scope = rememberCoroutineScope()
+    val messageState = remember { TextFieldState() }
+
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 8.dp, vertical = 4.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(4.dp),
+    ) {
+        OutlinedTextField(
+            state = messageState,
+            modifier = Modifier.weight(1f),
+            placeholder = { Text("Message") },
+            lineLimits =
+                androidx.compose.foundation.text.input.TextFieldLineLimits
+                    .MultiLine(maxHeightInLines = 4),
+        )
+        IconButton(
+            onClick = {
+                val text = messageState.text.toString().trim()
+                if (text.isNotEmpty()) {
+                    scope.launch(Dispatchers.IO) {
+                        accountViewModel.sendMarmotGroupMessage(nostrGroupId, text)
+                        messageState.clearText()
+                        onMessageSent()
+                    }
+                }
+            },
+        ) {
+            Icon(
+                imageVector = Icons.AutoMirrored.Filled.Send,
+                contentDescription = "Send",
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupFeedViewModel.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import com.vitorpamplona.amethyst.commons.ui.feeds.MarmotGroupFeedFilter
+import com.vitorpamplona.amethyst.commons.viewmodels.ListChangeFeedViewModel
+import com.vitorpamplona.amethyst.model.Account
+import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+
+class MarmotGroupFeedViewModel(
+    nostrGroupId: HexKey,
+    account: Account,
+) : ListChangeFeedViewModel(
+        MarmotGroupFeedFilter(nostrGroupId, account.marmotGroupList, account),
+        LocalCache,
+    ) {
+    class Factory(
+        val nostrGroupId: HexKey,
+        val account: Account,
+    ) : ViewModelProvider.Factory {
+        @Suppress("UNCHECKED_CAST")
+        override fun <T : ViewModel> create(modelClass: Class<T>): T = MarmotGroupFeedViewModel(nostrGroupId, account) as T
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/MarmotGroupListScreen.kt

@@ -0,0 +1,241 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.marmotGroup
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.Add
+import androidx.compose.material.icons.filled.VpnKey
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.FloatingActionButton
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.commons.model.marmotGroups.MarmotGroupChatroom
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.Route
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun MarmotGroupListScreen(
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    var showCreateGroupDialog by remember { mutableStateOf(false) }
+    var groupList by remember { mutableStateOf(listOf<Pair<HexKey, MarmotGroupChatroom>>()) }
+    val scope = rememberCoroutineScope()
+
+    // Load group list
+    LaunchedEffect(Unit) {
+        loadGroupList(accountViewModel, onUpdate = { groupList = it })
+    }
+
+    // Listen for group list changes
+    LaunchedEffect(Unit) {
+        accountViewModel.account.marmotGroupList.groupListChanges.collect {
+            loadGroupList(accountViewModel, onUpdate = { groupList = it })
+        }
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                navigationIcon = {
+                    IconButton(onClick = { nav.popBack() }) {
+                        Icon(
+                            imageVector = Icons.AutoMirrored.Filled.ArrowBack,
+                            contentDescription = "Back",
+                        )
+                    }
+                },
+                title = { Text("Marmot Groups") },
+                actions = {
+                    IconButton(
+                        onClick = {
+                            scope.launch(Dispatchers.IO) {
+                                accountViewModel.publishMarmotKeyPackage()
+                            }
+                        },
+                    ) {
+                        Icon(
+                            imageVector = Icons.Default.VpnKey,
+                            contentDescription = "Publish KeyPackage",
+                        )
+                    }
+                },
+            )
+        },
+        floatingActionButton = {
+            FloatingActionButton(onClick = { showCreateGroupDialog = true }) {
+                Icon(Icons.Default.Add, contentDescription = "Create Group")
+            }
+        },
+    ) { padding ->
+        if (groupList.isEmpty()) {
+            Box(
+                modifier = Modifier.fillMaxSize().padding(padding),
+                contentAlignment = Alignment.Center,
+            ) {
+                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                    Text(
+                        "No groups yet",
+                        style = MaterialTheme.typography.titleMedium,
+                    )
+                    Text(
+                        "Publish your KeyPackage to receive invitations.",
+                        style = MaterialTheme.typography.bodyMedium,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                        modifier = Modifier.padding(top = 4.dp),
+                    )
+                }
+            }
+        } else {
+            LazyColumn(
+                modifier = Modifier.fillMaxSize().padding(padding),
+            ) {
+                items(groupList, key = { it.first }) { (groupId, chatroom) ->
+                    MarmotGroupListItem(
+                        groupId = groupId,
+                        chatroom = chatroom,
+                        onClick = {
+                            nav.nav(Route.MarmotGroupChat(groupId))
+                        },
+                    )
+                    HorizontalDivider()
+                }
+            }
+        }
+    }
+
+    if (showCreateGroupDialog) {
+        CreateGroupDialog(
+            accountViewModel = accountViewModel,
+            onDismiss = { showCreateGroupDialog = false },
+            onGroupCreated = { groupId ->
+                showCreateGroupDialog = false
+                nav.nav(Route.MarmotGroupChat(groupId))
+            },
+        )
+    }
+}
+
+private fun loadGroupList(
+    accountViewModel: AccountViewModel,
+    onUpdate: (List<Pair<HexKey, MarmotGroupChatroom>>) -> Unit,
+) {
+    val groups = mutableListOf<Pair<HexKey, MarmotGroupChatroom>>()
+    accountViewModel.account.marmotGroupList.rooms.forEach { key, chatroom ->
+        groups.add(key to chatroom)
+    }
+    // Also add groups from MarmotManager that might not have messages yet
+    accountViewModel.account.marmotManager?.activeGroupIds()?.forEach { groupId ->
+        if (groups.none { it.first == groupId }) {
+            groups.add(groupId to accountViewModel.account.marmotGroupList.getOrCreateGroup(groupId))
+        }
+    }
+    groups.sortByDescending { it.second.newestMessage?.createdAt() ?: 0L }
+    onUpdate(groups)
+}
+
+@Composable
+fun MarmotGroupListItem(
+    groupId: HexKey,
+    chatroom: MarmotGroupChatroom,
+    onClick: () -> Unit,
+) {
+    val displayName by chatroom.displayName.collectAsStateWithLifecycle()
+    val newestMessage = chatroom.newestMessage
+
+    Row(
+        modifier =
+            Modifier
+                .fillMaxWidth()
+                .clickable(onClick = onClick)
+                .padding(horizontal = 16.dp, vertical = 12.dp),
+        horizontalArrangement = Arrangement.SpaceBetween,
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Column(modifier = Modifier.weight(1f)) {
+            Text(
+                text = displayName ?: "Group ${groupId.take(8)}...",
+                style = MaterialTheme.typography.titleSmall,
+                fontWeight = FontWeight.Bold,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+            )
+            if (newestMessage != null) {
+                Text(
+                    text = newestMessage.event?.content ?: "",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis,
+                    modifier = Modifier.padding(top = 2.dp),
+                )
+            } else {
+                Text(
+                    text = "No messages yet",
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    modifier = Modifier.padding(top = 2.dp),
+                )
+            }
+        }
+        Column(horizontalAlignment = Alignment.End) {
+            Text(
+                text = "${chatroom.messages.size} msgs",
+                style = MaterialTheme.typography.labelSmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/rooms/ChannelFabColumn.kt

@@ -103,6 +103,25 @@ fun ChannelFabColumn(nav: INav) {
                 }
 
                 Spacer(modifier = Modifier.height(20.dp))
+
+                FloatingActionButton(
+                    onClick = {
+                        nav.nav(Route.MarmotGroupList)
+                        isOpen = false
+                    },
+                    modifier = Size55Modifier,
+                    shape = CircleShape,
+                    containerColor = MaterialTheme.colorScheme.primary,
+                ) {
+                    Text(
+                        text = "MLS\nGroups",
+                        color = Color.White,
+                        textAlign = TextAlign.Center,
+                        fontSize = Font12SP,
+                    )
+                }
+
+                Spacer(modifier = Modifier.height(20.dp))
             }
         }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/rooms/dal/ChatroomListKnownFeedFilter.kt

@@ -77,7 +77,12 @@ class ChatroomListKnownFeedFilter(
                         .firstOrNull()
                 }
 
-        return (privateMessages + publicChannels + ephemeralChats).sortedWith(DefaultFeedOrder)
+        val marmotGroups =
+            account.marmotGroupList.rooms.mapNotNull { _, chatroom ->
+                chatroom.newestMessage
+            }
+
+        return (privateMessages + publicChannels + ephemeralChats + marmotGroups).sortedWith(DefaultFeedOrder)
     }
 
     override fun updateListWith(

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/IAccount.kt

@@ -20,6 +20,7 @@
  */
 package com.vitorpamplona.amethyst.commons.model
 
+import com.vitorpamplona.amethyst.commons.model.marmotGroups.MarmotGroupList
 import com.vitorpamplona.amethyst.commons.model.privateChats.ChatroomList
 import com.vitorpamplona.quartz.nip01Core.signers.EventTemplate
 import com.vitorpamplona.quartz.nip01Core.signers.NostrSigner
@@ -101,6 +102,9 @@ interface IAccount {
     /** Chatroom list for private DM conversations */
     val chatroomList: ChatroomList
 
+    /** Marmot MLS group chat list */
+    val marmotGroupList: MarmotGroupList
+
     /** Whether a note is acceptable (not hidden, not blocked, etc.) */
     fun isAcceptable(note: Note): Boolean
 

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/marmotGroups/MarmotGroupChatroom.kt

@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.marmotGroups
+
+import androidx.compose.runtime.Stable
+import com.vitorpamplona.amethyst.commons.model.Channel.Companion.DefaultFeedOrder
+import com.vitorpamplona.amethyst.commons.model.ListChange
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.amethyst.commons.model.NotesGatherer
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.MutableStateFlow
+import java.lang.ref.WeakReference
+
+/**
+ * Represents a Marmot MLS group chat room.
+ * Tracks decrypted inner messages for a single group.
+ * Follows the same pattern as [com.vitorpamplona.amethyst.commons.model.privateChats.Chatroom].
+ */
+@Stable
+class MarmotGroupChatroom(
+    val nostrGroupId: HexKey,
+) : NotesGatherer {
+    var messages: Set<Note> = setOf()
+    var displayName = MutableStateFlow<String?>(null)
+    var memberCount = MutableStateFlow(0)
+    var newestMessage: Note? = null
+
+    private var changesFlow: WeakReference<MutableSharedFlow<ListChange<Note>>> = WeakReference(null)
+
+    fun changesFlow(): MutableSharedFlow<ListChange<Note>> {
+        val current = changesFlow.get()
+        if (current != null) return current
+        val new = MutableSharedFlow<ListChange<Note>>(0, 100, BufferOverflow.DROP_OLDEST)
+        changesFlow = WeakReference(new)
+        return new
+    }
+
+    override fun removeNote(note: Note) {
+        removeMessageSync(note)
+    }
+
+    @Synchronized
+    fun addMessageSync(msg: Note): Boolean {
+        if (msg !in messages) {
+            messages = messages + msg
+            msg.addGatherer(this)
+
+            val createdAt = msg.createdAt() ?: 0L
+            if (createdAt > (newestMessage?.createdAt() ?: 0L)) {
+                newestMessage = msg
+            }
+
+            changesFlow.get()?.tryEmit(ListChange.Addition(msg))
+            return true
+        }
+        return false
+    }
+
+    @Synchronized
+    fun removeMessageSync(msg: Note): Boolean {
+        if (msg in messages) {
+            messages = messages - msg
+            msg.removeGatherer(this)
+
+            if (msg == newestMessage) {
+                newestMessage = messages.maxByOrNull { it.createdAt() ?: 0L }
+            }
+
+            changesFlow.get()?.tryEmit(ListChange.Deletion(msg))
+            return true
+        }
+        return false
+    }
+
+    fun pruneMessagesToTheLatestOnly(): Set<Note> {
+        val sorted = messages.sortedWith(DefaultFeedOrder)
+        val toKeep =
+            sorted.take(100).toSet() +
+                sorted.filter { it.flowSet?.isInUse() ?: false }
+
+        val toRemove = messages.minus(toKeep)
+        messages = toKeep
+
+        changesFlow.get()?.tryEmit(ListChange.SetDeletion<Note>(toRemove))
+        return toRemove
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/marmotGroups/MarmotGroupList.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.model.marmotGroups
+
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.utils.cache.LargeCache
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.MutableSharedFlow
+
+/**
+ * Tracks all Marmot MLS group chatrooms for an account.
+ * Follows the same pattern as [com.vitorpamplona.amethyst.commons.model.privateChats.ChatroomList].
+ */
+class MarmotGroupList {
+    var rooms = LargeCache<HexKey, MarmotGroupChatroom>()
+        private set
+
+    private val _groupListChanges = MutableSharedFlow<HexKey>(0, 20, BufferOverflow.DROP_OLDEST)
+    val groupListChanges = _groupListChanges
+
+    fun getOrCreateGroup(nostrGroupId: HexKey): MarmotGroupChatroom = rooms.getOrCreate(nostrGroupId) { MarmotGroupChatroom(nostrGroupId) }
+
+    fun addMessage(
+        nostrGroupId: HexKey,
+        msg: Note,
+    ) {
+        val chatroom = getOrCreateGroup(nostrGroupId)
+        if (chatroom.addMessageSync(msg)) {
+            _groupListChanges.tryEmit(nostrGroupId)
+        }
+    }
+
+    fun removeMessage(
+        nostrGroupId: HexKey,
+        msg: Note,
+    ) {
+        val chatroom = getOrCreateGroup(nostrGroupId)
+        if (chatroom.removeMessageSync(msg)) {
+            _groupListChanges.tryEmit(nostrGroupId)
+        }
+    }
+
+    fun allGroupIds(): List<HexKey> {
+        val result = mutableListOf<HexKey>()
+        rooms.forEach { key, _ -> result.add(key) }
+        return result
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/ui/feeds/MarmotGroupFeedFilter.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.ui.feeds
+
+import com.vitorpamplona.amethyst.commons.model.IAccount
+import com.vitorpamplona.amethyst.commons.model.Note
+import com.vitorpamplona.amethyst.commons.model.marmotGroups.MarmotGroupList
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+
+/**
+ * Feed filter for messages within a single Marmot MLS group.
+ * Retrieves decrypted inner events from the [MarmotGroupList].
+ */
+class MarmotGroupFeedFilter(
+    val nostrGroupId: HexKey,
+    val marmotGroupList: MarmotGroupList,
+    val account: IAccount,
+) : AdditiveFeedFilter<Note>(),
+    ChangesFlowFilter<Note> {
+    fun chatroom() = marmotGroupList.getOrCreateGroup(nostrGroupId)
+
+    override fun changesFlow() = chatroom().changesFlow()
+
+    override fun feedKey(): String = nostrGroupId
+
+    override fun feed(): List<Note> =
+        chatroom()
+            .messages
+            .filter { account.isAcceptable(it) }
+            .sortedWith(DefaultFeedOrder)
+
+    override fun applyFilter(newItems: Set<Note>): Set<Note> {
+        val chatroom = chatroom()
+        return newItems.filter { it in chatroom.messages && account.isAcceptable(it) }.toSet()
+    }
+
+    override fun sort(items: Set<Note>): List<Note> = items.sortedWith(DefaultFeedOrder)
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/viewmodels/MarmotGroupFeedViewModel.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.viewmodels
+
+import com.vitorpamplona.amethyst.commons.model.IAccount
+import com.vitorpamplona.amethyst.commons.model.cache.ICacheProvider
+import com.vitorpamplona.amethyst.commons.model.marmotGroups.MarmotGroupList
+import com.vitorpamplona.amethyst.commons.ui.feeds.MarmotGroupFeedFilter
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+
+/**
+ * ViewModel for a single Marmot group conversation feed.
+ * Exposes the decrypted inner messages for the group.
+ */
+class MarmotGroupFeedViewModel(
+    val nostrGroupId: HexKey,
+    val account: IAccount,
+    marmotGroupList: MarmotGroupList,
+    cacheProvider: ICacheProvider,
+) : ListChangeFeedViewModel(
+        MarmotGroupFeedFilter(nostrGroupId, marmotGroupList, account),
+        cacheProvider,
+    )

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/model/DesktopIAccount.kt

@@ -118,6 +118,9 @@ class DesktopIAccount(
     override val spammersHashCodes: Set<Int> = emptySet()
 
     override val chatroomList: ChatroomList = ChatroomList(accountState.pubKeyHex)
+    override val marmotGroupList =
+        com.vitorpamplona.amethyst.commons.model.marmotGroups
+            .MarmotGroupList()
 
     override val nip47SignerState: INwcSignerState =
         object : INwcSignerState {