diff --git a/hub/src/store/messages.ts b/hub/src/store/messages.ts
index bb850c0c3..2f4250cd4 100644
--- a/hub/src/store/messages.ts
+++ b/hub/src/store/messages.ts
@@ -64,6 +64,16 @@ export function addMessage(
         local_id: localId ?? null
     })
 
+    db.prepare(`
+        UPDATE sessions
+        SET updated_at = CASE WHEN updated_at > @updated_at THEN updated_at ELSE @updated_at END,
+            seq = seq + 1
+        WHERE id = @session_id
+    `).run({
+        session_id: sessionId,
+        updated_at: now
+    })
+
     const row = db.prepare('SELECT * FROM messages WHERE id = ?').get(id) as DbMessageRow | undefined
     if (!row) {
         throw new Error('Failed to create message')
@@ -154,6 +164,20 @@ export function mergeSessionMessages(
             'UPDATE messages SET session_id = ? WHERE session_id = ?'
         ).run(toSessionId, fromSessionId)
 
+        db.prepare(`
+            UPDATE sessions
+            SET updated_at = (
+                SELECT MAX(value)
+                FROM (
+                    SELECT updated_at AS value FROM sessions WHERE id = ?
+                    UNION ALL
+                    SELECT COALESCE(MAX(created_at), 0) AS value FROM messages WHERE session_id = ?
+                )
+            ),
+            seq = seq + 1
+            WHERE id = ?
+        `).run(toSessionId, toSessionId, toSessionId)
+
         db.exec('COMMIT')
         return { moved: result.changes, oldMaxSeq, newMaxSeq }
     } catch (error) {
diff --git a/hub/src/sync/sessionModel.test.ts b/hub/src/sync/sessionModel.test.ts
index 8b68c560b..035c884c2 100644
--- a/hub/src/sync/sessionModel.test.ts
+++ b/hub/src/sync/sessionModel.test.ts
@@ -52,6 +52,65 @@ describe('session model', () => {
         expect(toSessionSummary(session).effort).toBe('high')
     })
 
+    it('updates session timestamp when a message is stored', async () => {
+        const store = new Store(':memory:')
+        const events: SyncEvent[] = []
+        const cache = new SessionCache(store, createPublisher(events))
+
+        const session = cache.getOrCreateSession(
+            'session-message-time',
+            { path: '/tmp/project', host: 'localhost', flavor: 'codex' },
+            null,
+            'default'
+        )
+        const before = store.sessions.getSession(session.id)
+        await new Promise((resolve) => setTimeout(resolve, 2))
+
+        const message = store.messages.addMessage(session.id, { role: 'assistant', content: 'hello' })
+        const after = store.sessions.getSession(session.id)
+
+        expect(after?.updatedAt).toBe(message.createdAt)
+        expect(after?.updatedAt ?? 0).toBeGreaterThan(before?.updatedAt ?? 0)
+    })
+
+    it('broadcasts a session update when a message is received', async () => {
+        const store = new Store(':memory:')
+        const engine = new SyncEngine(
+            store,
+            {} as never,
+            new RpcRegistry(),
+            { broadcast() {} } as never
+        )
+        const events: SyncEvent[] = []
+        const unsubscribe = engine.subscribe((event) => events.push(event))
+
+        try {
+            const session = engine.getOrCreateSession(
+                'session-message-event-time',
+                { path: '/tmp/project', host: 'localhost', flavor: 'codex' },
+                null,
+                'default'
+            )
+            await new Promise((resolve) => setTimeout(resolve, 2))
+            const message = store.messages.addMessage(session.id, { role: 'assistant', content: 'hello' })
+
+            engine.handleRealtimeEvent({
+                type: 'message-received',
+                sessionId: session.id,
+                message
+            })
+
+            const sessionUpdated = events.find((event) =>
+                event.type === 'session-updated' && event.sessionId === session.id
+            )
+            expect(sessionUpdated).toBeDefined()
+            expect(engine.getSession(session.id)?.updatedAt).toBe(message.createdAt)
+        } finally {
+            unsubscribe()
+            engine.stop()
+        }
+    })
+
     it('persists explicit model reasoning effort on Codex sessions', () => {
         const store = new Store(':memory:')
         const events: SyncEvent[] = []
diff --git a/hub/src/sync/syncEngine.ts b/hub/src/sync/syncEngine.ts
index b4d391005..a3a623912 100644
--- a/hub/src/sync/syncEngine.ts
+++ b/hub/src/sync/syncEngine.ts
@@ -182,9 +182,7 @@ export class SyncEngine {
         }
 
         if (event.type === 'message-received' && event.sessionId) {
-            if (!this.getSession(event.sessionId)) {
-                this.sessionCache.refreshSession(event.sessionId)
-            }
+            this.sessionCache.refreshSession(event.sessionId)
         }
 
         this.eventPublisher.emit(event)
diff --git a/web/src/App.tsx b/web/src/App.tsx
index 7ab0798c2..d7289b6fe 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -239,30 +239,43 @@ function AppInner() {
         })
     }, [addToast])
 
-    const eventSubscription = useMemo(() => {
-        if (selectedSessionId) {
-            return { sessionId: selectedSessionId }
-        }
-        return { all: true }
-    }, [selectedSessionId])
+    const globalEventSubscription = useMemo(() => ({ all: true }), [])
+    const sessionEventSubscription = useMemo(
+        () => (selectedSessionId ? { sessionId: selectedSessionId } : undefined),
+        [selectedSessionId]
+    )
 
     const { subscriptionId } = useSSE({
         enabled: Boolean(api && token),
         token: token ?? '',
         baseUrl,
-        subscription: eventSubscription,
+        subscription: globalEventSubscription,
         onConnect: handleSseConnect,
         onDisconnect: handleSseDisconnect,
         onEvent: handleSseEvent,
         onToast: handleToast
     })
 
+    const { subscriptionId: sessionSubscriptionId } = useSSE({
+        enabled: Boolean(api && token && selectedSessionId),
+        token: token ?? '',
+        baseUrl,
+        subscription: sessionEventSubscription,
+        onEvent: handleSseEvent
+    })
+
     useVisibilityReporter({
         api,
         subscriptionId,
         enabled: Boolean(api && token)
     })
 
+    useVisibilityReporter({
+        api,
+        subscriptionId: sessionSubscriptionId,
+        enabled: Boolean(api && token && selectedSessionId)
+    })
+
     // Loading auth source
     if (isAuthSourceLoading) {
         return (
diff --git a/web/src/components/SessionList.tsx b/web/src/components/SessionList.tsx
index 115cc266e..128cc8ecf 100644
--- a/web/src/components/SessionList.tsx
+++ b/web/src/components/SessionList.tsx
@@ -152,6 +152,39 @@ function groupByMachine(
     })
 }
 
+const SESSION_LIST_LAST_SEEN_KEY = 'hapi.session-list.last-seen.v1'
+
+function loadLastSeenUpdatedAt(): Record<string, number> {
+    if (typeof window === 'undefined') {
+        return {}
+    }
+    try {
+        const raw = window.localStorage.getItem(SESSION_LIST_LAST_SEEN_KEY)
+        if (!raw) return {}
+        const parsed = JSON.parse(raw) as Record<string, unknown>
+        const next: Record<string, number> = {}
+        for (const [key, value] of Object.entries(parsed)) {
+            if (typeof value === 'number' && Number.isFinite(value)) {
+                next[key] = value
+            }
+        }
+        return next
+    } catch {
+        return {}
+    }
+}
+
+function persistLastSeenUpdatedAt(value: Record<string, number>) {
+    if (typeof window === 'undefined') {
+        return
+    }
+    try {
+        window.localStorage.setItem(SESSION_LIST_LAST_SEEN_KEY, JSON.stringify(value))
+    } catch {
+        // Ignore storage failures.
+    }
+}
+
 function CopyPathButton({ path, className }: { path: string; className?: string }) {
     const [copied, setCopied] = useState(false)
     const timerRef = useRef<ReturnType<typeof setTimeout>>(undefined)
@@ -181,6 +214,16 @@ function CopyPathButton({ path, className }: { path: string; className?: string
     )
 }
 
+function UnreadDot({ className }: { className?: string }) {
+    return (
+        <span
+            aria-label="Unread updates"
+            title="Unread updates"
+            className={`inline-block h-2 w-2 rounded-full bg-[var(--app-link)] shadow-[0_0_0_2px_var(--app-bg)] ${className ?? ''}`}
+        />
+    )
+}
+
 function PlusIcon(props: { className?: string }) {
     return (
         <svg
@@ -352,9 +395,10 @@ function SessionItem(props: {
     showPath?: boolean
     api: ApiClient | null
     selected?: boolean
+    unread?: boolean
 }) {
     const { t } = useTranslation()
-    const { session: s, onSelect, showPath = true, api, selected = false } = props
+    const { session: s, onSelect, showPath = true, api, selected = false, unread = false } = props
     const { haptic } = usePlatform()
     const [menuOpen, setMenuOpen] = useState(false)
     const [menuAnchorPoint, setMenuAnchorPoint] = useState<{ x: number; y: number }>({ x: 0, y: 0 })
@@ -399,6 +443,9 @@ function SessionItem(props: {
                         <div className={`truncate text-sm font-medium ${s.active ? 'text-[var(--app-fg)]' : 'text-[var(--app-hint)]'}`}>
                             {sessionName}
                         </div>
+                        {unread ? (
+                            <UnreadDot className="shrink-0" />
+                        ) : null}
                         {s.active && s.thinking ? (
                             <LoaderIcon className="h-3.5 w-3.5 shrink-0 text-[var(--app-hint)] animate-spin-slow" />
                         ) : null}
@@ -489,9 +536,71 @@ export function SessionList(props: {
         () => groupSessionsByDirectory(deduplicateSessionsByAgentId(props.sessions, selectedSessionId)),
         [props.sessions, selectedSessionId]
     )
+    const [lastSeenUpdatedAtBySession, setLastSeenUpdatedAtBySession] = useState<Record<string, number>>(
+        () => loadLastSeenUpdatedAt()
+    )
     const [collapseOverrides, setCollapseOverrides] = useState<Map<string, boolean>>(
         () => new Map()
     )
+
+    useEffect(() => {
+        setLastSeenUpdatedAtBySession((prev) => {
+            const next: Record<string, number> = {}
+            let changed = false
+
+            for (const session of props.sessions) {
+                const previousValue = prev[session.id]
+                if (typeof previousValue === 'number' && Number.isFinite(previousValue)) {
+                    next[session.id] = previousValue
+                } else {
+                    next[session.id] = session.updatedAt
+                    changed = true
+                }
+            }
+
+            if (!changed && Object.keys(prev).length !== Object.keys(next).length) {
+                changed = true
+            }
+
+            return changed ? next : prev
+        })
+    }, [props.sessions])
+
+    useEffect(() => {
+        if (!selectedSessionId) return
+        const selectedSession = props.sessions.find((session) => session.id === selectedSessionId)
+        if (!selectedSession) return
+
+        setLastSeenUpdatedAtBySession((prev) => {
+            const previousValue = prev[selectedSession.id] ?? 0
+            if (previousValue >= selectedSession.updatedAt) {
+                return prev
+            }
+            return {
+                ...prev,
+                [selectedSession.id]: selectedSession.updatedAt
+            }
+        })
+    }, [props.sessions, selectedSessionId])
+
+    useEffect(() => {
+        persistLastSeenUpdatedAt(lastSeenUpdatedAtBySession)
+    }, [lastSeenUpdatedAtBySession])
+
+    const unreadSessionIds = useMemo(() => {
+        const next = new Set<string>()
+        for (const session of props.sessions) {
+            if (session.id === selectedSessionId) {
+                continue
+            }
+            const lastSeenUpdatedAt = lastSeenUpdatedAtBySession[session.id] ?? session.updatedAt
+            if (session.updatedAt > lastSeenUpdatedAt) {
+                next.add(session.id)
+            }
+        }
+        return next
+    }, [lastSeenUpdatedAtBySession, props.sessions, selectedSessionId])
+
     const isGroupCollapsed = (group: SessionGroup): boolean => {
         const override = collapseOverrides.get(group.key)
         if (override !== undefined) return override
@@ -524,6 +633,26 @@ export function SessionList(props: {
         [groups, machineLabelsById] // eslint-disable-line react-hooks/exhaustive-deps
     )
 
+    const groupHasUnread = useMemo(() => {
+        const map = new Map<string, boolean>()
+        for (const group of groups) {
+            map.set(group.key, group.sessions.some((session) => unreadSessionIds.has(session.id)))
+        }
+        return map
+    }, [groups, unreadSessionIds])
+
+    const machineHasUnread = useMemo(() => {
+        const map = new Map<string, boolean>()
+        for (const machineGroup of machineGroups) {
+            const key = machineGroup.machineId ?? UNKNOWN_MACHINE_ID
+            map.set(
+                key,
+                machineGroup.projectGroups.some((group) => groupHasUnread.get(group.key))
+            )
+        }
+        return map
+    }, [groupHasUnread, machineGroups])
+
     const isMachineCollapsed = (mg: MachineGroup): boolean => {
         const key = `machine::${mg.machineId ?? UNKNOWN_MACHINE_ID}`
         const override = collapseOverrides.get(key)
@@ -611,6 +740,7 @@ export function SessionList(props: {
             <div className="flex flex-col gap-3 px-2 pt-1 pb-2">
                 {machineGroups.map((mg) => {
                     const machineCollapsed = isMachineCollapsed(mg)
+                    const hasUnreadInMachine = machineHasUnread.get(mg.machineId ?? UNKNOWN_MACHINE_ID) === true
                     return (
                         <div key={mg.machineId ?? UNKNOWN_MACHINE_ID}>
                             {/* Level 1: Machine */}
@@ -622,6 +752,9 @@ export function SessionList(props: {
                                 <ChevronIcon className="h-4 w-4 text-[var(--app-hint)] shrink-0" collapsed={machineCollapsed} />
                                 <MachineIcon className="h-4 w-4 text-[var(--app-hint)] shrink-0" />
                                 <span className="text-sm font-semibold truncate flex-1">{mg.label}</span>
+                                {hasUnreadInMachine ? (
+                                    <UnreadDot className="shrink-0" />
+                                ) : null}
                                 <span className="text-[11px] tabular-nums text-[var(--app-hint)] shrink-0">({mg.totalSessions})</span>
                             </button>
 
@@ -631,6 +764,7 @@ export function SessionList(props: {
                                 <div className="flex flex-col ml-3.5 pl-1 mt-0.5">
                                     {mg.projectGroups.map((group) => {
                                         const isCollapsed = isGroupCollapsed(group)
+                                        const hasUnreadInGroup = groupHasUnread.get(group.key) === true
                                         return (
                                             <div key={group.key}>
                                                 <div
@@ -642,6 +776,9 @@ export function SessionList(props: {
                                                     <span className="font-medium text-sm truncate flex-1">
                                                         {group.displayName}
                                                     </span>
+                                                    {hasUnreadInGroup ? (
+                                                        <UnreadDot className="shrink-0" />
+                                                    ) : null}
                                                     <CopyPathButton path={group.directory} className="opacity-0 group-hover/project:opacity-100 transition-opacity duration-150" />
                                                     <span className="text-[11px] tabular-nums text-[var(--app-hint)] shrink-0">
                                                         ({group.sessions.length})
@@ -660,6 +797,7 @@ export function SessionList(props: {
                                                                 showPath={false}
                                                                 api={api}
                                                                 selected={s.id === selectedSessionId}
+                                                                unread={unreadSessionIds.has(s.id)}
                                                             />
                                                         ))}
                                                     </div>
diff --git a/web/src/hooks/useSSE.ts b/web/src/hooks/useSSE.ts
index 7b43260c0..7f4787098 100644
--- a/web/src/hooks/useSSE.ts
+++ b/web/src/hooks/useSSE.ts
@@ -499,6 +499,9 @@ export function useSSE(options: {
 
             if (event.type === 'message-received') {
                 ingestIncomingMessages(event.sessionId, [event.message])
+                const patch = { updatedAt: event.message.createdAt }
+                patchSessionDetail(event.sessionId, patch)
+                patchSessionSummary(event.sessionId, patch)
             }
 
             if (event.type === 'session-added' || event.type === 'session-updated' || event.type === 'session-removed') {