diff --git a/web/hwlab-cloud-web/app.ts b/web/hwlab-cloud-web/app.ts
index 9fe9002d..77087de1 100644
--- a/web/hwlab-cloud-web/app.ts
+++ b/web/hwlab-cloud-web/app.ts
@@ -290,6 +290,7 @@ initSessionSidebar();
 initCopySessionIdButton();
 initCodeAgentTimeoutControl();
 initConversationScrollMemory();
+renderConversation();
 initCommandBar();
 initLiveBuildOverlay();
 initWorkbenchLogout(el.logoutButton);
@@ -620,11 +621,11 @@ function refreshSessionSidebar(options = {}) {
 }
 
 function renderSessionSidebar() {
-  const view = sessionTabsFromConversations(sessionSidebarConversations(), {
+  const view = safeSessionTabsView(() => sessionTabsFromConversations(sessionSidebarConversations(), {
     selectedConversationId: state.conversationId,
     selectedSessionId: state.sessionId,
     activeTraceId: state.activeTraceId
-  });
+  }));
   replaceChildren(el.sessionTabs, ...view.tabs.map(sessionTabButton));
   const pending = Boolean(state.sessionList.pendingAction);
   el.sessionCreate.disabled = pending;
@@ -634,6 +635,17 @@ function renderSessionSidebar() {
   el.sessionStatus.title = state.sessionList.error || state.sessionList.loadedAt || "session list not loaded";
 }
 
+function safeSessionTabsView(factory) {
+  try {
+    const view = factory();
+    if (Array.isArray(view?.tabs)) return view;
+    state.sessionList.error = "session tabs renderer returned an invalid view";
+  } catch (error) {
+    state.sessionList.error = error?.message || String(error);
+  }
+  return { tabs: [], activeKey: null, activeConversation: null };
+}
+
 function renderCopySessionIdButton(activeConversation) {
   if (!el.copySessionId) return;
   const conversationId = textOf(activeConversation?.conversationId) || textOf(state.conversationId);
diff --git a/web/hwlab-cloud-web/index.html b/web/hwlab-cloud-web/index.html
index e23167e1..f3a1eed4 100644
--- a/web/hwlab-cloud-web/index.html
+++ b/web/hwlab-cloud-web/index.html
@@ -208,7 +208,7 @@
               </tbody>
             </table>
           </div>
-        </section
+        </section>
         <section class="view settings-view" id="settings" data-view="settings" aria-labelledby="settings-title" hidden>
           <div class="workspace-panel settings-panel">
             <div class="panel-title-row">
@@ -222,7 +222,6 @@
             </div>
           </div>
         </section>
->
 
         <form class="command-bar" id="command-form" aria-label="Agent 输入">
           <label class="agent-timeout-control" for="code-agent-provider-profile">
diff --git a/web/hwlab-cloud-web/scripts/check.ts b/web/hwlab-cloud-web/scripts/check.ts
index 234ced12..003ec121 100644
--- a/web/hwlab-cloud-web/scripts/check.ts
+++ b/web/hwlab-cloud-web/scripts/check.ts
@@ -46,6 +46,7 @@ console.log("hwlab-cloud-web check: dist freshness verified");
 const html = readWeb("index.html");
 const styles = readWeb("styles.css");
 const app = readCloudWebAppSource(rootDir);
+assertCloudWebHtmlStructure(html);
 assertTraceHelpersBound(readWeb("app-trace.ts"));
 const liveStatus = readWeb("live-status.ts");
 const helpMarkdown = readWeb("help.md");
@@ -260,6 +261,16 @@ function assertIncludes(source, term, message) {
   assert.ok(source.includes(term), message);
 }
 
+function assertCloudWebHtmlStructure(source) {
+  assertDoesNotInclude(source, "</section\n", "Cloud Web HTML must not contain an unterminated closing section tag");
+  assertDoesNotInclude(source, "\n>\n\n        <form", "Cloud Web HTML must not contain a stray tag close before the command bar");
+  assertIncludes(source, "        </section>\n        <section class=\"view settings-view\"", "settings view must follow a complete section close");
+  assertIncludes(source, "        </section>\n\n        <form class=\"command-bar\"", "command bar must follow a complete section close");
+  const centerWorkspace = sectionByClass(source, "section", "center-workspace");
+  assertIncludes(centerWorkspace, 'id="settings" data-view="settings"', "settings view must stay inside center workspace");
+  assertIncludes(centerWorkspace, 'id="command-form"', "command form must stay inside center workspace");
+}
+
 function assertDoesNotInclude(source, term, message) {
   assert.equal(source.includes(term), false, message);
 }
@@ -313,6 +324,26 @@ function sectionById(source, tagName, id) {
   return source.slice(start);
 }
 
+function sectionByClass(source, tagName, className) {
+  const startPattern = new RegExp(`<${tagName}\\b[^>]*\\bclass=["'][^"']*\\b${escapeRegExp(className)}\\b[^"']*["'][^>]*>`, "iu");
+  const startMatch = startPattern.exec(source);
+  if (!startMatch) return "";
+  const start = startMatch.index;
+  const tagPattern = new RegExp(`</?${tagName}\\b[^>]*>`, "giu");
+  tagPattern.lastIndex = start;
+  let depth = 0;
+  for (const match of source.slice(start).matchAll(tagPattern)) {
+    const absoluteEnd = start + match.index + match[0].length;
+    if (match[0].startsWith("</")) {
+      depth -= 1;
+      if (depth === 0) return source.slice(start, absoluteEnd);
+    } else {
+      depth += 1;
+    }
+  }
+  return source.slice(start);
+}
+
 function cssRule(source, selector) {
   const match = new RegExp(`${escapeRegExp(selector)}\\s*\\{`, "u").exec(source);
   if (!match) return "";
diff --git a/web/hwlab-cloud-web/session-tabs.test.ts b/web/hwlab-cloud-web/session-tabs.test.ts
index d9e6106c..db2c0867 100644
--- a/web/hwlab-cloud-web/session-tabs.test.ts
+++ b/web/hwlab-cloud-web/session-tabs.test.ts
@@ -77,6 +77,13 @@ test("session tabs default to newest visible conversation", () => {
   assert.equal(view.activeKey, "ses_b");
 });
 
+test("session tabs expose a stable empty conversation view", () => {
+  const view = sessionTabsFromConversations([]);
+
+  assert.deepEqual(view, { tabs: [], activeKey: null, activeConversation: null });
+  assert.equal(Array.isArray(view.tabs), true);
+});
+
 test("session tabs surface authoritative messageCount and fall back to message length", () => {
   const explicit = sessionTabsFromConversations([
     conversation("cnv_explicit", "ses_explicit", "trc_explicit", "completed", "2026-06-03T00:00:01Z", {
diff --git a/web/hwlab-cloud-web/styles.css b/web/hwlab-cloud-web/styles.css
index 48d4ccc4..8697450c 100644
--- a/web/hwlab-cloud-web/styles.css
+++ b/web/hwlab-cloud-web/styles.css
@@ -2768,20 +2768,58 @@ tbody tr:last-child td {
 @media (max-width: 520px) {
   .workbench-shell {
     --rail-width: 64px;
-    --session-sidebar-width: 128px;
-    grid-template-columns: var(--rail-width) var(--session-sidebar-width) minmax(0, 1fr);
-    grid-template-rows: minmax(0, 1fr) clamp(260px, 34dvh, 320px);
+    --session-sidebar-width: 0px;
+    grid-template-columns: minmax(0, 1fr);
+    grid-template-rows: auto minmax(0, 1fr) clamp(260px, 34dvh, 320px);
   }
 
   .activity-rail {
+    grid-column: 1;
+    grid-row: 1;
+    display: flex;
+    flex-wrap: wrap;
+    align-items: center;
+    gap: 6px;
     padding: 7px;
+    border-right: 0;
+    border-bottom: 1px solid var(--line);
+    overflow-x: auto;
+    overflow-y: hidden;
+  }
+
+  .rail-spacer {
+    display: none;
   }
 
   .rail-button {
+    flex: 0 0 auto;
+    min-height: 36px;
     padding: 6px 3px;
     font-size: 11px;
   }
 
+  .sidebar-toggle {
+    min-height: 36px;
+  }
+
+  .session-sidebar {
+    display: none;
+  }
+
+  .center-workspace {
+    grid-column: 1;
+    grid-row: 2;
+  }
+
+  .right-sidebar {
+    grid-column: 1;
+    grid-row: 3;
+    width: 100%;
+    padding-left: 8px;
+    border-left: 0;
+    border-top: 1px solid var(--line);
+  }
+
   .topbar {
     display: block;
   }