diff --git a/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStore.kt b/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStore.kt
new file mode 100644
index 000000000..70333fd91
--- /dev/null
+++ b/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStore.kt
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: AGPLv3
+ *
+ * Copyright (c) 2026 Askimo
+ */
+package io.askimo.ui.bookmarks
+
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+
+class BookmarkCountsStore {
+    private val mutableCounts = MutableStateFlow<Map<String, Int>>(emptyMap())
+
+    val counts: StateFlow<Map<String, Int>> = mutableCounts.asStateFlow()
+
+    fun setCounts(counts: Map<String, Int>) {
+        mutableCounts.value = counts.toMap()
+    }
+
+    fun applyBookmarkChange(sessionId: String, isBookmarked: Boolean) {
+        mutableCounts.update { current ->
+            val nextCount = (current[sessionId] ?: 0) + if (isBookmarked) 1 else -1
+            if (nextCount > 0) {
+                current + (sessionId to nextCount)
+            } else {
+                current - sessionId
+            }
+        }
+    }
+}
diff --git a/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarksViewModel.kt b/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarksViewModel.kt
index fdd079650..398496e71 100644
--- a/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarksViewModel.kt
+++ b/desktop-shared/src/main/kotlin/io/askimo/ui/bookmarks/BookmarksViewModel.kt
@@ -24,6 +24,7 @@ import kotlinx.coroutines.withContext
 class BookmarksViewModel(
     private val chatSessionService: ChatSessionService,
     private val scope: CoroutineScope,
+    private val bookmarkCountsStore: BookmarkCountsStore,
 ) {
     private val log = logger<BookmarksViewModel>()
 
@@ -63,6 +64,10 @@ class BookmarksViewModel(
      * then persist the change via [chatSessionService].
      */
     fun removeBookmark(messageId: String) {
+        val sessionId = groups.firstOrNull { group ->
+            group.messages.any { it.id == messageId }
+        }?.session?.id
+
         // Optimistic update
         groups = groups.mapNotNull { group ->
             val updated = group.messages.filter { it.id != messageId }
@@ -71,9 +76,12 @@ class BookmarksViewModel(
 
         scope.launch {
             try {
-                withContext(Dispatchers.IO) {
+                val isBookmarked = withContext(Dispatchers.IO) {
                     chatSessionService.toggleBookmark(messageId)
                 }
+                if (sessionId != null) {
+                    bookmarkCountsStore.applyBookmarkChange(sessionId, isBookmarked)
+                }
             } catch (e: Exception) {
                 log.error("Failed to remove bookmark for message {}", messageId, e)
                 load()
diff --git a/desktop-shared/src/main/kotlin/io/askimo/ui/chat/ChatViewModel.kt b/desktop-shared/src/main/kotlin/io/askimo/ui/chat/ChatViewModel.kt
index 7f2086d5a..7948f081e 100644
--- a/desktop-shared/src/main/kotlin/io/askimo/ui/chat/ChatViewModel.kt
+++ b/desktop-shared/src/main/kotlin/io/askimo/ui/chat/ChatViewModel.kt
@@ -25,6 +25,7 @@ import io.askimo.core.event.internal.DiagramFixedEvent
 import io.askimo.core.event.internal.ProjectRefreshEvent
 import io.askimo.core.event.internal.SessionTitleUpdatedEvent
 import io.askimo.core.logging.logger
+import io.askimo.ui.bookmarks.BookmarkCountsStore
 import io.askimo.ui.session.SessionManager
 import io.askimo.ui.util.ErrorHandler
 import kotlinx.coroutines.CoroutineScope
@@ -52,6 +53,7 @@ class ChatViewModel(
     private val sessionManager: SessionManager,
     private val scope: CoroutineScope,
     private val chatSessionService: ChatSessionService,
+    private val bookmarkCountsStore: BookmarkCountsStore,
 ) : ChatActions {
     private val log = logger<ChatViewModel>()
 
@@ -1358,6 +1360,7 @@ class ChatViewModel(
      * for instant feedback (optimistic update).
      */
     override fun toggleBookmark(messageId: String) {
+        val sessionId = currentSessionId.value
         bookmarkedMessageIds = if (messageId in bookmarkedMessageIds) {
             bookmarkedMessageIds - messageId
         } else {
@@ -1366,9 +1369,12 @@ class ChatViewModel(
 
         scope.launch {
             try {
-                withContext(Dispatchers.IO) {
+                val isBookmarked = withContext(Dispatchers.IO) {
                     chatSessionService.toggleBookmark(messageId)
                 }
+                if (sessionId != null) {
+                    bookmarkCountsStore.applyBookmarkChange(sessionId, isBookmarked)
+                }
             } catch (e: Exception) {
                 // Roll back the optimistic update on failure
                 bookmarkedMessageIds = if (messageId in bookmarkedMessageIds) {
diff --git a/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionManager.kt b/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionManager.kt
index 89376b1da..7fdd167e8 100644
--- a/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionManager.kt
+++ b/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionManager.kt
@@ -24,6 +24,7 @@ import io.askimo.core.providers.ConfigurationErrorException
 import io.askimo.core.providers.isContextLengthError
 import io.askimo.core.providers.sendStreamingMessageWithCallback
 import io.askimo.core.vision.ImageProcessor
+import io.askimo.ui.bookmarks.BookmarkCountsStore
 import io.askimo.ui.chat.ChatViewModel
 import io.askimo.ui.chat.CreationMode
 import kotlinx.coroutines.CoroutineScope
@@ -62,6 +63,7 @@ import java.util.concurrent.ConcurrentHashMap
 class SessionManager(
     private val chatSessionService: ChatSessionService,
     private val scope: CoroutineScope,
+    private val bookmarkCountsStore: BookmarkCountsStore,
 ) {
     private val log = logger<SessionManager>()
 
@@ -476,6 +478,7 @@ class SessionManager(
             sessionManager = this,
             scope = scope,
             chatSessionService = chatSessionService,
+            bookmarkCountsStore = bookmarkCountsStore,
         )
 
         chatViewModels[sessionId] = viewModel
diff --git a/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionsViewModel.kt b/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionsViewModel.kt
index d27f8dc2c..d46b5614a 100644
--- a/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionsViewModel.kt
+++ b/desktop-shared/src/main/kotlin/io/askimo/ui/session/SessionsViewModel.kt
@@ -17,6 +17,7 @@ import io.askimo.core.event.internal.SessionTitleUpdatedEvent
 import io.askimo.core.event.internal.SessionsRefreshEvent
 import io.askimo.core.i18n.LocalizationManager
 import io.askimo.core.logging.logger
+import io.askimo.ui.bookmarks.BookmarkCountsStore
 import io.askimo.ui.common.export.ExportFormat
 import io.askimo.ui.shell.PinnedSidebarState
 import io.askimo.ui.util.ErrorHandler
@@ -40,6 +41,7 @@ class SessionsViewModel(
     private val scope: CoroutineScope,
     private val sessionService: ChatSessionService,
     private val sessionManager: SessionManager,
+    private val bookmarkCountsStore: BookmarkCountsStore,
     private val onCreateNewSession: () -> String,
     private val onRenameComplete: () -> Unit = {}, // Callback when rename completes
 ) : PinnedSidebarState {
@@ -74,7 +76,7 @@ class SessionsViewModel(
         private set
 
     /** sessionId → number of bookmarked messages. Only populated for sessions that have ≥1 bookmark. */
-    var bookmarkCountsBySession by mutableStateOf<Map<String, Int>>(emptyMap())
+    var bookmarkCountsBySession by mutableStateOf(bookmarkCountsStore.counts.value)
         private set
 
     var searchQuery by mutableStateOf("")
@@ -126,12 +128,21 @@ class SessionsViewModel(
     }
 
     init {
+        subscribeToBookmarkCounts()
         loadSessions(1)
         loadRecentSessions()
         loadStarredSessions()
         subscribeToSessionEvents()
     }
 
+    private fun subscribeToBookmarkCounts() {
+        scope.launch {
+            bookmarkCountsStore.counts.collect { counts ->
+                bookmarkCountsBySession = counts
+            }
+        }
+    }
+
     /**
      * Subscribe to internal events to keep session list updated.
      */
@@ -200,7 +211,7 @@ class SessionsViewModel(
                 }
                 recentSessions = sessions
                 totalSessionCount = total
-                bookmarkCountsBySession = bookmarkCounts
+                bookmarkCountsStore.setCounts(bookmarkCounts)
 
                 log.debug("Loaded ${sessions.size} sessions without projects (showing ${sessions.size} in sidebar, total: $total)")
             } catch (e: Exception) {
diff --git a/desktop-shared/src/test/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStoreTest.kt b/desktop-shared/src/test/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStoreTest.kt
new file mode 100644
index 000000000..398568955
--- /dev/null
+++ b/desktop-shared/src/test/kotlin/io/askimo/ui/bookmarks/BookmarkCountsStoreTest.kt
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: AGPLv3
+ *
+ * Copyright (c) 2026 Askimo
+ */
+package io.askimo.ui.bookmarks
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class BookmarkCountsStoreTest {
+    @Test
+    fun `setCounts publishes a snapshot`() {
+        val source = mutableMapOf("session-a" to 2)
+        val store = BookmarkCountsStore()
+
+        store.setCounts(source)
+        source["session-a"] = 3
+
+        assertEquals(mapOf("session-a" to 2), store.counts.value)
+    }
+
+    @Test
+    fun `bookmark creates a count for a session`() {
+        val store = BookmarkCountsStore()
+
+        store.applyBookmarkChange("session-a", isBookmarked = true)
+
+        assertEquals(mapOf("session-a" to 1), store.counts.value)
+    }
+
+    @Test
+    fun `bookmark increments the session without changing other counts`() {
+        val store = BookmarkCountsStore()
+        store.setCounts(mapOf("session-a" to 2, "session-b" to 4))
+
+        store.applyBookmarkChange("session-a", isBookmarked = true)
+
+        assertEquals(mapOf("session-a" to 3, "session-b" to 4), store.counts.value)
+    }
+
+    @Test
+    fun `unbookmark decrements the session count`() {
+        val store = BookmarkCountsStore()
+        store.setCounts(mapOf("session-a" to 2))
+
+        store.applyBookmarkChange("session-a", isBookmarked = false)
+
+        assertEquals(mapOf("session-a" to 1), store.counts.value)
+    }
+
+    @Test
+    fun `unbookmark removes a session after its final bookmark`() {
+        val store = BookmarkCountsStore()
+        store.setCounts(mapOf("session-a" to 1, "session-b" to 2))
+
+        store.applyBookmarkChange("session-a", isBookmarked = false)
+
+        assertEquals(mapOf("session-b" to 2), store.counts.value)
+    }
+
+    @Test
+    fun `unbookmark leaves counts unchanged for a missing session`() {
+        val store = BookmarkCountsStore()
+        store.setCounts(mapOf("session-a" to 2))
+
+        store.applyBookmarkChange("session-b", isBookmarked = false)
+
+        assertEquals(mapOf("session-a" to 2), store.counts.value)
+    }
+}
diff --git a/desktop/src/main/kotlin/io/askimo/desktop/Main.kt b/desktop/src/main/kotlin/io/askimo/desktop/Main.kt
index 2f89200bf..ab984c353 100644
--- a/desktop/src/main/kotlin/io/askimo/desktop/Main.kt
+++ b/desktop/src/main/kotlin/io/askimo/desktop/Main.kt
@@ -98,6 +98,7 @@ import io.askimo.desktop.shell.footerBar
 import io.askimo.desktop.shell.navigationSidebar
 import io.askimo.desktop.shell.telemetryPanel
 import io.askimo.desktop.user.userProfileDialog
+import io.askimo.ui.bookmarks.BookmarkCountsStore
 import io.askimo.ui.bookmarks.BookmarksViewModel
 import io.askimo.ui.bookmarks.bookmarksView
 import io.askimo.ui.chat.ChatViewModel
@@ -475,8 +476,9 @@ fun app(frameWindowScope: FrameWindowScope? = null, windowState: WindowState? =
 
     val appContext = remember { koin.get<AppContext>() }
     val chatSessionService = remember { koin.get<ChatSessionService>() }
+    val bookmarkCountsStore = remember { koin.get<BookmarkCountsStore>() }
 
-    val bookmarksViewModel = remember { BookmarksViewModel(chatSessionService, scope) }
+    val bookmarksViewModel = remember { BookmarksViewModel(chatSessionService, scope, bookmarkCountsStore) }
 
     val sessionManager = remember { koin.get<SessionManager>() }
     val sessionsViewModel = remember {
diff --git a/desktop/src/main/kotlin/io/askimo/desktop/di/DesktopModule.kt b/desktop/src/main/kotlin/io/askimo/desktop/di/DesktopModule.kt
index 061cc51ba..85d00973a 100644
--- a/desktop/src/main/kotlin/io/askimo/desktop/di/DesktopModule.kt
+++ b/desktop/src/main/kotlin/io/askimo/desktop/di/DesktopModule.kt
@@ -19,6 +19,7 @@ import io.askimo.core.tools.ToolProviderImpl
 import io.askimo.desktop.project.ProjectViewModel
 import io.askimo.desktop.project.ProjectsViewModel
 import io.askimo.desktop.settings.AIProviderViewModel
+import io.askimo.ui.bookmarks.BookmarkCountsStore
 import io.askimo.ui.chat.ProjectIndexStateManager
 import io.askimo.ui.common.monitoring.SystemResourceMonitor
 import io.askimo.ui.discover.DiscoverViewModel
@@ -89,11 +90,13 @@ val desktopModule = module {
     single { SystemResourceMonitor() }
 
     single { ProjectIndexStateManager() }
+    single { BookmarkCountsStore() }
 
     single {
         SessionManager(
             chatSessionService = get(),
             scope = CoroutineScope(Dispatchers.Default + SupervisorJob()),
+            bookmarkCountsStore = get(),
         )
     }
 
@@ -102,6 +105,7 @@ val desktopModule = module {
             scope = scope,
             sessionService = get(),
             sessionManager = sessionManager,
+            bookmarkCountsStore = get(),
             onCreateNewSession = onCreateNewSession,
             onRenameComplete = onRenameComplete,
         )