diff --git a/frontend/dashboard.css b/frontend/dashboard.css
index a1b8e37..023a443 100644
--- a/frontend/dashboard.css
+++ b/frontend/dashboard.css
@@ -385,6 +385,9 @@ textarea { resize: vertical; min-height: 120px; }
 .update-sheet-header button { min-height:44px; }
 .update-triage-progress { margin:10px 0; padding:8px 10px; border:1px solid #2a496e; border-radius:10px; background:#10213a; }
 .update-sheet-content { overflow-wrap:anywhere; white-space:pre-wrap; }
+.update-new-activity { scroll-margin-block:18px 96px; border-color:#60a5fa; box-shadow:0 0 0 2px rgba(96,165,250,.25); }
+.update-new-activity::before { content:'New activity'; display:inline-block; margin-bottom:6px; padding:2px 7px; border-radius:999px; background:#1d4ed8; color:#fff; font-size:12px; font-weight:700; }
+.update-new-activity-jump { position:sticky; bottom:92px; z-index:4; min-height:44px; width:100%; margin:10px 0; border-color:#60a5fa; background:#17345a; }
 .update-reply { display:grid; gap:8px; margin-top:16px; }
 .update-reply textarea { width:100%; min-height:112px; resize:vertical; }
 .update-reply button { min-height:44px; width:100%; }
diff --git a/frontend/dashboard.js b/frontend/dashboard.js
index 1c2548f..7f49d4a 100644
--- a/frontend/dashboard.js
+++ b/frontend/dashboard.js
@@ -910,6 +910,11 @@
     refresh: refreshMyWorkView,
     select: qs,
   });
+  const updateReadPosition = createUpdateReadPosition({
+    panel: qs('#update-sheet .update-sheet-panel'),
+    jump: qs('#jump-update-new-activity'),
+  });
+  qs('#jump-update-new-activity').addEventListener('click', () => updateReadPosition.jump());
   const notificationReader = createNotificationReader({
     load: fetchNotificationDetail,
     getScope: () => confirmedOwnerLogin,
@@ -924,6 +929,7 @@
       }
       selectedUpdate = item;
       selectedUpdateDetail = null;
+      updateReadPosition.open(String(item.notification_id));
       updateMentions.dismiss();
       qs('#update-sheet').classList.add('open');
       qs('#update-sheet-key').textContent = item.key || '';
@@ -2984,6 +2990,8 @@
     qs('#load-older-update-comments').hidden = !Number.isInteger(state?.older_page);
     qs('#update-conversation-status').textContent = comments.length ?
       comments.length + ' of ' + Math.max(state.total || 0, comments.length) + ' messages loaded.' : 'No comments yet.';
+    const newest = qs('#update-comments .issue-comment:last-child');
+    updateReadPosition.ready(String(selectedUpdate?.notification_id || ''), newest);
   }
 
   function renderPullConversation(state) {
diff --git a/frontend/index.html b/frontend/index.html
index 94f7c8f..e9a804a 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -760,6 +760,7 @@
     </div>
     <h2>Full conversation</h2>
     <div id="update-comments"></div>
+    <button class="update-new-activity-jump" id="jump-update-new-activity" type="button" hidden>Jump to new activity</button>
     <button class="conversation-more" id="load-older-update-comments" type="button" hidden>Load older messages</button>
     <div id="update-conversation-status" class="small" aria-live="assertive"></div>
     <details>
@@ -1074,6 +1075,7 @@
 <script src="static/mobile-work-entry.js"></script>
 <script src="static/mobile-queue-launcher.js"></script>
 <script src="static/update-triage-session.js"></script>
+<script src="static/update-read-position.js"></script>
 <script src="static/update-triage-launcher.js"></script>
 <script src="static/agenda-session-launcher.js"></script>
 <script src="static/mobile-launch.js"></script>
diff --git a/frontend/service-worker.js b/frontend/service-worker.js
index c389342..193cb4a 100644
--- a/frontend/service-worker.js
+++ b/frontend/service-worker.js
@@ -77,6 +77,7 @@ const SHELL = [
   BASE + 'static/mobile-work-entry.js',
   BASE + 'static/mobile-queue-launcher.js',
   BASE + 'static/update-triage-session.js',
+  BASE + 'static/update-read-position.js',
   BASE + 'static/update-triage-launcher.js',
   BASE + 'static/agenda-session-launcher.js',
   BASE + 'static/mobile-launch.js',
diff --git a/frontend/update-read-position.js b/frontend/update-read-position.js
new file mode 100644
index 0000000..c2a524f
--- /dev/null
+++ b/frontend/update-read-position.js
@@ -0,0 +1,49 @@
+(function (root, factory) {
+  if (typeof module === 'object' && module.exports) module.exports = factory;
+  else root.createUpdateReadPosition = factory;
+})(typeof self !== 'undefined' ? self : this, function createUpdateReadPosition(options) {
+  const panel = options.panel;
+  const jump = options.jump;
+  let identity = '';
+  let openingTop = 0;
+  let movedByUser = false;
+  let positioned = false;
+  let target = null;
+
+  function moveToTarget() {
+    if (!target) return false;
+    target.classList?.add('update-new-activity');
+    target.scrollIntoView({ block:'end' });
+    positioned = true;
+    jump.hidden = true;
+    return true;
+  }
+
+  panel.addEventListener('scroll', () => {
+    if (identity && !positioned && panel.scrollTop !== openingTop) movedByUser = true;
+  }, { passive:true });
+
+  return {
+    open(nextIdentity) {
+      identity = String(nextIdentity || '');
+      openingTop = panel.scrollTop;
+      movedByUser = false;
+      positioned = false;
+      target = null;
+      jump.hidden = true;
+    },
+    ready(readyIdentity, newest) {
+      if (!identity || String(readyIdentity || '') !== identity || positioned || !newest) return false;
+      target = newest;
+      target.classList?.add('update-new-activity');
+      if (movedByUser) {
+        jump.hidden = false;
+        return false;
+      }
+      return moveToTarget();
+    },
+    jump() {
+      return moveToTarget();
+    },
+  };
+});
diff --git a/tests/test_service_worker.py b/tests/test_service_worker.py
index 8bbdb1e..045122f 100644
--- a/tests/test_service_worker.py
+++ b/tests/test_service_worker.py
@@ -847,6 +847,7 @@ def test_install_precaches_complete_subpath_scoped_app_shell():
         "/dashboard/static/mobile-work-entry.js",
         "/dashboard/static/mobile-queue-launcher.js",
         "/dashboard/static/update-triage-session.js",
+        "/dashboard/static/update-read-position.js",
         "/dashboard/static/update-triage-launcher.js",
         "/dashboard/static/agenda-session-launcher.js",
         "/dashboard/static/mobile-launch.js",
diff --git a/tests/test_update_read_position.py b/tests/test_update_read_position.py
new file mode 100644
index 0000000..98bded8
--- /dev/null
+++ b/tests/test_update_read_position.py
@@ -0,0 +1,87 @@
+import json
+import subprocess
+from pathlib import Path
+
+import pytest
+
+from tests.dashboard_bundle import dashboard
+
+
+POSITIONER = Path(__file__).resolve().parents[1] / "frontend" / "update-read-position.js"
+
+
+def run_positioner(script: str) -> dict:
+    source = f"const createPositioner = require({json.dumps(str(POSITIONER))});\n" + script
+    result = subprocess.run(["node", "-e", source], capture_output=True, text=True)
+    assert result.returncode == 0, result.stderr
+    return json.loads(result.stdout)
+
+
+def test_new_update_scrolls_to_newest_activity_once_without_reusing_previous_offset():
+    result = run_positioner("""
+const listeners = {};
+const panel = {scrollTop:480, addEventListener:(name, fn)=>listeners[name]=fn};
+const jump = {hidden:true, focus(){}};
+const first = {calls:0, scrollIntoView(){this.calls += 1}, classList:{add(){}}};
+const second = {calls:0, scrollIntoView(){this.calls += 1}, classList:{add(){}}};
+const positioner = createPositioner({panel, jump});
+positioner.open('101');
+positioner.ready('101', first);
+positioner.ready('101', first);
+panel.scrollTop = 920;
+positioner.open('102');
+positioner.ready('102', second);
+process.stdout.write(JSON.stringify({first:first.calls, second:second.calls, jumpHidden:jump.hidden}));
+""")
+
+    assert result == {"first": 1, "second": 1, "jumpHidden": True}
+
+
+def test_user_scroll_during_loading_preserves_position_until_explicit_jump():
+    result = run_positioner("""
+const listeners = {};
+const panel = {scrollTop:120, addEventListener:(name, fn)=>listeners[name]=fn};
+const jump = {hidden:true, focus(){}};
+const target = {calls:0, scrollIntoView(){this.calls += 1}, classList:{add(){}}};
+const positioner = createPositioner({panel, jump});
+positioner.open('201');
+panel.scrollTop = 260;
+listeners.scroll();
+positioner.ready('201', target);
+const before = {calls:target.calls, hidden:jump.hidden, top:panel.scrollTop};
+positioner.jump();
+process.stdout.write(JSON.stringify({before, after:{calls:target.calls, hidden:jump.hidden}}));
+""")
+
+    assert result == {
+        "before": {"calls": 0, "hidden": False, "top": 260},
+        "after": {"calls": 1, "hidden": True},
+    }
+
+
+def test_stale_or_prefetched_conversation_cannot_move_the_visible_update():
+    result = run_positioner("""
+const panel = {scrollTop:0, addEventListener(){}};
+const jump = {hidden:true};
+const stale = {calls:0, scrollIntoView(){this.calls += 1}, classList:{add(){}}};
+const current = {calls:0, scrollIntoView(){this.calls += 1}, classList:{add(){}}};
+const positioner = createPositioner({panel, jump});
+positioner.open('302');
+positioner.ready('301', stale);
+positioner.ready('302', current);
+process.stdout.write(JSON.stringify({stale:stale.calls, current:current.calls}));
+""")
+
+    assert result == {"stale": 0, "current": 1}
+
+
+@pytest.mark.anyio
+async def test_dashboard_mounts_mobile_new_activity_positioning_flow():
+    html = await dashboard()
+
+    assert '<script src="static/update-read-position.js"></script>' in html
+    assert 'id="jump-update-new-activity"' in html
+    assert "updateReadPosition.open(String(item.notification_id))" in html
+    assert "updateReadPosition.ready(String(selectedUpdate?.notification_id || ''), newest)" in html
+    assert ".update-new-activity" in html
+    assert "BASE + 'static/update-read-position.js'" in (POSITIONER.parent / "service-worker.js").read_text()