diff --git a/CHANGELOG.md b/CHANGELOG.md
index 185f15f1..a3667bd2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Added
+
+- **PR #2614** by @Michaelyklam (refs #2508) — Tighten session pinning around the clarified sidebar workflow: right-clicking a conversation row now opens the existing action menu, pin attempts are capped at three active pinned conversations, and the backend rejects a fourth pin until one is unpinned.
 
 ## [v0.51.95] — 2026-05-20 — Release BS (stage-388 — 5-PR batch — live tool callback event dedup + browser-only dashboard links + messaging transcript merge alignment + Geist Contrast skin + SSE runtime diagnostics)
 
diff --git a/api/routes.py b/api/routes.py
index 063226bf..a8397efa 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -5631,8 +5631,22 @@ def handle_post(handler, parsed) -> bool:
             s = _ensure_full_session_before_mutation(body["session_id"], s)
         except KeyError:
             return bad(handler, "Session not found", 404)
+        pin_requested = bool(body.get("pinned", True))
+        if pin_requested and not getattr(s, "pinned", False):
+            pinned_ids = {
+                getattr(existing, "session_id", None) for existing in all_sessions()
+                if getattr(existing, "pinned", False) and not getattr(existing, "archived", False)
+            }
+            with LOCK:
+                pinned_ids.update(
+                    sid for sid, existing in SESSIONS.items()
+                    if getattr(existing, "pinned", False) and not getattr(existing, "archived", False)
+                )
+            pinned_ids.discard(body["session_id"])
+            if len(pinned_ids) >= 3:
+                return bad(handler, "Up to 3 sessions can be pinned. Unpin one before pinning another.", 400)
         with _get_session_agent_lock(body["session_id"]):
-            s.pinned = bool(body.get("pinned", True))
+            s.pinned = pin_requested
             s.save()
         return j(handler, {"ok": True, "session": s.compact()})
 
diff --git a/docs/pr-media/issue-2508/session-pinned-sidebar.png b/docs/pr-media/issue-2508/session-pinned-sidebar.png
new file mode 100644
index 00000000..d424edd4
Binary files /dev/null and b/docs/pr-media/issue-2508/session-pinned-sidebar.png differ
diff --git a/static/sessions.js b/static/sessions.js
index fc9ae52b..ec8d12ee 100644
--- a/static/sessions.js
+++ b/static/sessions.js
@@ -1475,6 +1475,9 @@ function _sessionSnapshotById(sid){
   if(S.session&&S.session.session_id===sid) return S.session;
   return (_allSessions||[]).find(s=>s&&s.session_id===sid)||null;
 }
+function _pinnedSessionCount(){
+  return (_allSessions||[]).filter(s=>s&&s.pinned&&!s.archived).length;
+}
 function _worktreeSessionCount(ids){
   return (ids||[]).reduce((count,sid)=>{
     const session=_sessionSnapshotById(sid);
@@ -1785,12 +1788,17 @@ function _openSessionActionMenu(session, anchorEl){
       }
     ));
   }
+  const pinLimitReached=!session.pinned&&_pinnedSessionCount()>=3;
   menu.appendChild(_buildSessionAction(
     session.pinned?t('session_unpin'):t('session_pin'),
-    session.pinned?t('session_unpin_desc'):t('session_pin_desc'),
+    pinLimitReached?'Only 3 conversations can be pinned':(session.pinned?t('session_unpin_desc'):t('session_pin_desc')),
     session.pinned?ICONS.pin:ICONS.unpin,
     async()=>{
       closeSessionActionMenu();
+      if(pinLimitReached){
+        if(typeof showToast==='function') showToast('Only 3 conversations can be pinned. Unpin one before pinning another.',3000,'error');
+        return;
+      }
       const newPinned=!session.pinned;
       try{
         await api('/api/session/pin',{method:'POST',body:JSON.stringify({session_id:session.session_id,pinned:newPinned})});
@@ -1799,7 +1807,7 @@ function _openSessionActionMenu(session, anchorEl){
         renderSessionList();
       }catch(err){showToast(t('session_pin_failed')+err.message);}
     },
-    session.pinned?'is-active':''
+    (session.pinned?'is-active':'')+(pinLimitReached?' is-disabled':'')
   ));
   menu.appendChild(_buildSessionAction(
     t('session_move_project'),
@@ -3388,6 +3396,16 @@ function renderSessionListFromCache(){
       actions.appendChild(menuBtn);
       el.appendChild(actions);
     }
+    el.oncontextmenu=(e)=>{
+      if(readOnly) return;
+      e.preventDefault();
+      e.stopPropagation();
+      clearTimeout(_tapTimer);
+      _tapTimer=null;
+      _lastTapTime=0;
+      _clearPointerDragState();
+      _openSessionActionMenu(s, actions||el);
+    };
 
     // Use pointerup + manual double-tap detection instead of onclick/ondblclick.
     // onclick/ondblclick are unreliable on touch devices (iPad Safari especially):
diff --git a/static/style.css b/static/style.css
index 8a84a24d..78030f7c 100644
--- a/static/style.css
+++ b/static/style.css
@@ -733,6 +733,8 @@
   .session-action-copy{display:flex;flex-direction:column;gap:2px;min-width:0;}
   .session-action-meta{font-size:11px;color:var(--muted);line-height:1.3;white-space:normal;opacity:.72;}
   .session-action-opt.is-active{background:var(--accent-bg);}
+  .session-action-opt.is-disabled{opacity:.55;cursor:not-allowed;}
+  .session-action-opt.is-disabled:hover{background:transparent;}
   .session-action-opt.danger:hover{background:rgba(239,83,80,.08);}
   .session-action-opt.danger .ws-opt-icon,.session-action-opt.danger .ws-opt-name{color:var(--error);}
   /* Hide overlay during inline rename */
diff --git a/tests/test_issue2508_session_pin_cap.py b/tests/test_issue2508_session_pin_cap.py
new file mode 100644
index 00000000..b629c7f5
--- /dev/null
+++ b/tests/test_issue2508_session_pin_cap.py
@@ -0,0 +1,89 @@
+"""Regression checks for issue #2508 session pinning bounds and context menu access."""
+
+import json
+import pathlib
+import urllib.error
+import urllib.request
+
+from tests._pytest_port import BASE
+
+
+ROOT = pathlib.Path(__file__).resolve().parent.parent
+ROUTES_PY = (ROOT / "api" / "routes.py").read_text()
+SESSIONS_JS = (ROOT / "static" / "sessions.js").read_text()
+STYLE_CSS = (ROOT / "static" / "style.css").read_text()
+
+
+def post(path, body=None):
+    data = json.dumps(body or {}).encode()
+    req = urllib.request.Request(
+        BASE + path,
+        data=data,
+        headers={"Content-Type": "application/json"},
+    )
+    try:
+        with urllib.request.urlopen(req, timeout=10) as r:
+            return json.loads(r.read()), r.status
+    except urllib.error.HTTPError as e:
+        return json.loads(e.read()), e.code
+
+
+def make_session(created):
+    payload = {
+        "title": f"Pin cap {len(created) + 1}",
+        "messages": [{"role": "user", "content": "keep this conversation handy"}],
+        "model": "test/pin-cap",
+    }
+    d, status = post("/api/session/import", payload)
+    assert status == 200
+    sid = d["session"]["session_id"]
+    created.append(sid)
+    return sid
+
+
+def test_session_pin_endpoint_caps_pinned_sessions_at_three():
+    created = []
+    try:
+        pinned = [make_session(created) for _ in range(3)]
+        for sid in pinned:
+            d, status = post("/api/session/pin", {"session_id": sid, "pinned": True})
+            assert status == 200
+            assert d["session"]["pinned"] is True
+
+        fourth = make_session(created)
+        d, status = post("/api/session/pin", {"session_id": fourth, "pinned": True})
+        assert status == 400
+        assert "3 sessions" in d.get("error", "")
+
+        d, status = post("/api/session/pin", {"session_id": pinned[0], "pinned": False})
+        assert status == 200
+        assert d["session"]["pinned"] is False
+
+        d, status = post("/api/session/pin", {"session_id": fourth, "pinned": True})
+        assert status == 200
+        assert d["session"]["pinned"] is True
+    finally:
+        for sid in created:
+            post("/api/session/delete", {"session_id": sid})
+
+
+def test_session_pin_cap_has_backend_and_frontend_guards():
+    assert 'pinned_ids = {' in ROUTES_PY
+    assert 'pinned_ids.update(' in ROUTES_PY
+    assert 'if len(pinned_ids) >= 3:' in ROUTES_PY
+    assert 'Up to 3 sessions can be pinned' in ROUTES_PY
+
+    assert 'function _pinnedSessionCount()' in SESSIONS_JS
+    assert 'const pinLimitReached=!session.pinned&&_pinnedSessionCount()>=3;' in SESSIONS_JS
+    assert "Only 3 conversations can be pinned" in SESSIONS_JS
+    assert ".session-action-opt.is-disabled{opacity:.55;cursor:not-allowed;}" in STYLE_CSS
+
+
+def test_session_rows_open_action_menu_from_right_click():
+    assert 'el.oncontextmenu=(e)=>{' in SESSIONS_JS
+    context_idx = SESSIONS_JS.find('el.oncontextmenu=(e)=>{')
+    assert context_idx != -1
+    block = SESSIONS_JS[context_idx:SESSIONS_JS.find('};', context_idx) + 2]
+    assert 'e.preventDefault();' in block
+    assert 'e.stopPropagation();' in block
+    assert '_openSessionActionMenu(s, actions||el);' in block