diff --git a/frontend/src/components/GuideReader.svelte b/frontend/src/components/GuideReader.svelte
index 4f51e7e..46bcce4 100644
--- a/frontend/src/components/GuideReader.svelte
+++ b/frontend/src/components/GuideReader.svelte
@@ -14,6 +14,15 @@
   let activeModuleKey = '';
   let activeTab = 0;
   let search = '';
+  // collapse state: 'modules' | 'platform' | 'technical' | 'app:<name>'
+  let open: Record<string, boolean> = { modules: true };
+  function toggle(key: string) { open = { ...open, [key]: !open[key] }; }
+  function expandFor(key: string) {
+    const app = key.split('.')[0];
+    if (app === 'platform') open = { ...open, platform: true };
+    else if (app === 'technical') open = { ...open, technical: true };
+    else open = { ...open, modules: true, ['app:' + app]: true };
+  }
 
   marked.setOptions({ gfm: true, breaks: false });
   const render = (md: string): string => marked.parse(md, { async: false }) as string;
@@ -38,13 +47,21 @@
         }))
         .filter(a => a.modules.length > 0);
 
+  // group nav: product-app "Modules" section (all except platform/technical) + platform + technical
+  $: searching = !!search.trim();
+  $: productApps = filtered.filter(a => a.app !== 'platform' && a.app !== 'technical');
+  $: platformApp = filtered.find(a => a.app === 'platform') ?? null;
+  $: technicalApp = filtered.find(a => a.app === 'technical') ?? null;
+  const isOpen = (key: string) => searching || !!open[key];
+
   async function loadNav() {
     loadingNav = true;
     try {
       nav = await fetchNav();
-      // auto-select the first module
-      const first = nav.find(a => a.modules.length)?.modules[0];
-      if (first) selectModule(first.module);
+      // auto-select the first product module (or first available)
+      const first = (nav.find(a => a.app !== 'platform' && a.app !== 'technical' && a.modules.length)
+        ?? nav.find(a => a.modules.length))?.modules[0];
+      if (first) { expandFor(first.module); selectModule(first.module); }
     } catch (e: any) {
       addToast('error', 'Failed to load guides', e?.response?.data?.message ?? e?.message ?? '');
     } finally {
@@ -54,6 +71,7 @@
 
   async function selectModule(key: string) {
     if (key === activeModuleKey && module) return;
+    expandFor(key);
     activeModuleKey = key;
     loadingModule = true;
     module = null;
@@ -88,21 +106,59 @@
       {:else if filtered.length === 0}
         <div class="side-msg">No guides found.</div>
       {:else}
-        {#each filtered as app (app.app)}
-          <div class="nav-group">
-            <div class="nav-group-label">{appLabel(app.app)}</div>
-            {#each app.modules as m (m.module)}
-              <button
-                class="nav-item"
-                class:active={m.module === activeModuleKey}
-                on:click={() => selectModule(m.module)}
-                title={m.module}
-              >
-                {m.title}
-              </button>
-            {/each}
+        <!-- MODULES (product apps) -->
+        {#if productApps.length}
+          <div class="nav-sec">
+            <button class="sec-head" on:click={() => toggle('modules')}>
+              <span class="chev">{isOpen('modules') ? '▾' : '▸'}</span> Modules
+            </button>
+            {#if isOpen('modules')}
+              {#each productApps as app (app.app)}
+                <div class="nav-app">
+                  <button class="app-head" on:click={() => toggle('app:' + app.app)}>
+                    <span class="chev">{isOpen('app:' + app.app) ? '▾' : '▸'}</span> {appLabel(app.app)}
+                  </button>
+                  {#if isOpen('app:' + app.app)}
+                    {#each app.modules as m (m.module)}
+                      <button class="nav-item nested" class:active={m.module === activeModuleKey}
+                        on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>
+                    {/each}
+                  {/if}
+                </div>
+              {/each}
+            {/if}
           </div>
-        {/each}
+        {/if}
+
+        <!-- PLATFORM -->
+        {#if platformApp}
+          <div class="nav-sec">
+            <button class="sec-head" on:click={() => toggle('platform')}>
+              <span class="chev">{isOpen('platform') ? '▾' : '▸'}</span> Platform
+            </button>
+            {#if isOpen('platform')}
+              {#each platformApp.modules as m (m.module)}
+                <button class="nav-item" class:active={m.module === activeModuleKey}
+                  on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>
+              {/each}
+            {/if}
+          </div>
+        {/if}
+
+        <!-- TECHNICAL -->
+        {#if technicalApp}
+          <div class="nav-sec">
+            <button class="sec-head" on:click={() => toggle('technical')}>
+              <span class="chev">{isOpen('technical') ? '▾' : '▸'}</span> Technical
+            </button>
+            {#if isOpen('technical')}
+              {#each technicalApp.modules as m (m.module)}
+                <button class="nav-item" class:active={m.module === activeModuleKey}
+                  on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>
+              {/each}
+            {/if}
+          </div>
+        {/if}
       {/if}
     </nav>
 
@@ -177,17 +233,29 @@
   .side-nav { flex: 1; overflow-y: auto; padding: 0.25rem 0 1rem; }
   .side-msg { color: rgba(255,255,255,0.7); font-size: 0.85rem; padding: 0.75rem 1.25rem; }
 
-  .nav-group { margin-bottom: 0.5rem; }
-  .nav-group-label {
-    color: rgba(255,255,255,0.55); font-size: 0.7rem; font-weight: 700;
-    text-transform: uppercase; letter-spacing: 0.06em; padding: 0.5rem 1.25rem 0.25rem;
+  .nav-sec { margin-bottom: 0.1rem; }
+  .sec-head {
+    display: flex; align-items: center; gap: 0.4rem; width: 100%; text-align: left;
+    background: none; border: none; cursor: pointer;
+    color: rgba(255,255,255,0.9); font-size: 0.78rem; font-weight: 700;
+    text-transform: uppercase; letter-spacing: 0.05em; padding: 0.6rem 1.1rem;
   }
+  .sec-head:hover { background: rgba(255,255,255,0.06); }
+  .app-head {
+    display: flex; align-items: center; gap: 0.35rem; width: 100%; text-align: left;
+    background: none; border: none; cursor: pointer;
+    color: rgba(255,255,255,0.72); font-size: 0.82rem; font-weight: 600;
+    padding: 0.35rem 1.1rem 0.35rem 1.5rem;
+  }
+  .app-head:hover { background: rgba(255,255,255,0.06); color: white; }
+  .chev { font-size: 0.58rem; width: 9px; display: inline-block; color: rgba(255,255,255,0.55); flex-shrink: 0; }
   .nav-item {
     display: block; width: 100%; text-align: left;
     background: none; border: none; border-left: 3px solid transparent;
     color: rgba(255,255,255,0.82); font-size: 0.85rem;
     padding: 0.4rem 1.25rem 0.4rem 1.5rem; cursor: pointer;
   }
+  .nav-item.nested { padding-left: 2.5rem; }
   .nav-item:hover { background: rgba(255,255,255,0.08); color: white; }
   .nav-item.active { background: rgba(255,255,255,0.14); color: white; border-left-color: white; font-weight: 600; }