diff --git a/src/praisonaiui/server.py b/src/praisonaiui/server.py
index 144c201..2233a79 100644
--- a/src/praisonaiui/server.py
+++ b/src/praisonaiui/server.py
@@ -1303,9 +1303,11 @@ async def patch_session(request: Request) -> JSONResponse:
         body = await request.json()
     except Exception:
         return JSONResponse({"error": "Invalid JSON"}, status_code=400)
-    title = body.get("title")
+    title = body.get("title") if isinstance(body, dict) else None
     if title is not None:
-        await _datastore.update_session(session_id, title=title)
+        if not isinstance(title, str) or not title.strip():
+            return JSONResponse({"error": "title must be a non-empty string"}, status_code=400)
+        await _datastore.update_session(session_id, title=title.strip()[:200])
     return JSONResponse({"status": "updated", "session_id": session_id})
 
 
diff --git a/src/praisonaiui/templates/frontend/plugins/views/chat.js b/src/praisonaiui/templates/frontend/plugins/views/chat.js
index edb346b..a2b82d6 100644
--- a/src/praisonaiui/templates/frontend/plugins/views/chat.js
+++ b/src/praisonaiui/templates/frontend/plugins/views/chat.js
@@ -244,6 +244,9 @@ function injectStyles() {
     .chat-sess-item.active { background:rgba(var(--db-accent-rgb,100,100,255),.15); }
     .chat-sess-item .sess-title { font-weight:500; white-space:nowrap; overflow:hidden; text-overflow:ellipsis; }
     .chat-sess-item .sess-meta { font-size:11px; color:var(--db-text-dim); }
+    .chat-sess-item { position:relative; }
+    .chat-sess-item .sess-rename { position:absolute; top:6px; right:6px; display:none; background:none; border:none; color:var(--db-text-dim); cursor:pointer; font-size:12px; padding:2px 4px; }
+    .chat-sess-item:hover .sess-rename, .chat-sess-item .sess-rename:focus { display:block; }
 
     .chat-main-panel { flex:1; display:flex; flex-direction:column; min-width:0; }
     .chat-top-bar { padding:10px 16px; border-bottom:1px solid var(--db-border); display:flex; align-items:center; justify-content:space-between; gap:10px; }
@@ -1103,10 +1106,41 @@ function renderSessionList() {
     `;
     el.title = id;
     el.addEventListener('click', () => loadSession(id));
+    if (!platformName && id) {
+      const btn = document.createElement('button');
+      btn.className = 'sess-rename';
+      btn.title = 'Rename session';
+      btn.setAttribute('aria-label', 'Rename session');
+      btn.textContent = '✎';
+      btn.addEventListener('click', (e) => { e.stopPropagation(); renameSession(id, title); });
+      el.appendChild(btn);
+    }
     list.appendChild(el);
   });
 }
 
+async function renameSession(sessionId, currentTitle) {
+  const next = (window.prompt('Rename session', currentTitle || '') || '').trim();
+  if (!next || next === currentTitle) return;
+  try {
+    const resp = await fetch('/sessions/' + encodeURIComponent(sessionId), {
+      method: 'PATCH',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ title: next }),
+    });
+    if (!resp.ok) throw new Error('HTTP ' + resp.status);
+    const s = allSessions.find((x) => (x.id || x.session_id) === sessionId);
+    if (s) { s.title = next; delete s.name; }
+    renderSessionList();
+    if (sessionId === currentSessionId) {
+      const header = document.getElementById('chat-header-title');
+      if (header) header.textContent = next;
+    }
+  } catch (e) {
+    console.warn('[Chat] Failed to rename session:', e);
+  }
+}
+
 async function loadSession(sessionId) {
   currentSessionId = sessionId;
   refreshStreamingUI();
@@ -1158,7 +1192,8 @@ async function loadSession(sessionId) {
         title.textContent = (sessionIcon || '📨') + ' ' + displayName;
       }
     } else if (title) {
-      title.textContent = 'Session ' + sessionId.substring(0, 8);
+      const cached = allSessions.find((x) => (x.id || x.session_id) === sessionId);
+      title.textContent = (cached && (cached.name || cached.title)) || ('Session ' + sessionId.substring(0, 8));
     }
   } catch (e) {
     console.warn('[Chat] Failed to load session:', e);
diff --git a/tests/unit/test_chat_session_rename.py b/tests/unit/test_chat_session_rename.py
new file mode 100644
index 0000000..ce7f590
--- /dev/null
+++ b/tests/unit/test_chat_session_rename.py
@@ -0,0 +1,49 @@
+"""Issue #331 — rename a session from the chat rail via the existing PATCH route."""
+
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+
+from starlette.applications import Starlette
+from starlette.routing import Route
+from starlette.testclient import TestClient
+
+import praisonaiui.server as server
+from praisonaiui.datastore import MemoryDataStore
+
+CHAT = Path("src/praisonaiui/templates/frontend/plugins/views/chat.js")
+
+
+def _client(monkeypatch):
+    ds = MemoryDataStore()
+    monkeypatch.setattr(server, "_datastore", ds)
+    app = Starlette(routes=[Route("/sessions/{session_id}", server.patch_session, methods=["PATCH"])])
+    sid = asyncio.run(ds.create_session())["id"]
+    return TestClient(app), ds, sid
+
+
+def test_patch_renames_and_trims(monkeypatch):
+    client, ds, sid = _client(monkeypatch)
+    r = client.patch(f"/sessions/{sid}", json={"title": "  My chat  "})
+    assert r.status_code == 200
+    assert asyncio.run(ds.get_session(sid))["title"] == "My chat"
+
+
+def test_patch_rejects_blank_or_non_string_title(monkeypatch):
+    client, _, sid = _client(monkeypatch)
+    assert client.patch(f"/sessions/{sid}", json={"title": "   "}).status_code == 400
+    assert client.patch(f"/sessions/{sid}", json={"title": 123}).status_code == 400
+
+
+def test_patch_unknown_session_404(monkeypatch):
+    client, _, _ = _client(monkeypatch)
+    assert client.patch("/sessions/nope", json={"title": "x"}).status_code == 404
+
+
+def test_rail_has_rename_button_wired_to_patch():
+    src = CHAT.read_text()
+    assert "async function renameSession(sessionId, currentTitle)" in src
+    assert "method: 'PATCH'" in src
+    assert "renameSession(id, title)" in src
+    assert "e.stopPropagation()" in src