diff --git a/frontend/src/portal-shell/App.vue b/frontend/src/portal-shell/App.vue
index 306eee0..27dd258 100644
--- a/frontend/src/portal-shell/App.vue
+++ b/frontend/src/portal-shell/App.vue
@@ -1,10 +1,17 @@
 <script setup>
-import { computed, onMounted, ref, watch } from 'vue';
+import { computed, onMounted, onUnmounted, ref, watch } from 'vue';
 import { useRoute, useRouter } from 'vue-router';
 
 import HealthStatus from './components/HealthStatus.vue';
 import { consumeNavigationNotice, syncNavigationRoutes } from './router.js';
 import { normalizeRoutePath } from './routeContracts.js';
+import {
+  SIDEBAR_STORAGE_KEY,
+  buildSidebarUiState,
+  isMobileViewport,
+  parseSidebarCollapsedPreference,
+  serializeSidebarCollapsedPreference,
+} from './sidebarState.js';
 
 const route = useRoute();
 const router = useRouter();
@@ -20,6 +27,9 @@ const adminLinks = ref({
   pages: '/admin/pages',
   performance: '/admin/performance',
 });
+const sidebarCollapsed = ref(false);
+const sidebarMobileOpen = ref(false);
+const isMobile = ref(false);
 
 function toShellPath(targetRoute) {
   return normalizeRoutePath(targetRoute);
@@ -46,6 +56,71 @@ const adminLoginHref = computed(() => {
   return `/admin/login?next=${encodeURIComponent('/portal-shell')}`;
 });
 
+const sidebarUiState = computed(() =>
+  buildSidebarUiState({
+    isMobile: isMobile.value,
+    sidebarCollapsed: sidebarCollapsed.value,
+    sidebarMobileOpen: sidebarMobileOpen.value,
+  }),
+);
+
+const sidebarToggleLabel = computed(() => {
+  if (isMobile.value) {
+    return sidebarMobileOpen.value ? '關閉側邊欄' : '開啟側邊欄';
+  }
+  return sidebarCollapsed.value ? '展開側邊欄' : '收合側邊欄';
+});
+
+function restoreSidebarPreference() {
+  try {
+    const stored = window.sessionStorage.getItem(SIDEBAR_STORAGE_KEY);
+    sidebarCollapsed.value = parseSidebarCollapsedPreference(stored);
+  } catch {
+    sidebarCollapsed.value = false;
+  }
+}
+
+function persistSidebarPreference() {
+  try {
+    window.sessionStorage.setItem(
+      SIDEBAR_STORAGE_KEY,
+      serializeSidebarCollapsedPreference(sidebarCollapsed.value),
+    );
+  } catch {
+    // Keep UI behavior deterministic even if storage is unavailable.
+  }
+}
+
+function checkViewport() {
+  isMobile.value = isMobileViewport(window.innerWidth);
+  if (!isMobile.value) {
+    sidebarMobileOpen.value = false;
+  }
+}
+
+function closeMobileSidebar() {
+  sidebarMobileOpen.value = false;
+}
+
+function toggleSidebar() {
+  if (isMobile.value) {
+    sidebarMobileOpen.value = !sidebarMobileOpen.value;
+    return;
+  }
+  sidebarCollapsed.value = !sidebarCollapsed.value;
+  persistSidebarPreference();
+}
+
+function handleViewportResize() {
+  checkViewport();
+}
+
+function handleGlobalKeydown(event) {
+  if (event.key === 'Escape') {
+    closeMobileSidebar();
+  }
+}
+
 async function loadNavigation() {
   loading.value = true;
   errorMessage.value = '';
@@ -111,12 +186,22 @@ async function loadNavigation() {
 }
 
 onMounted(() => {
+  restoreSidebarPreference();
+  checkViewport();
+  window.addEventListener('resize', handleViewportResize, { passive: true });
+  window.addEventListener('keydown', handleGlobalKeydown);
   void loadNavigation();
 });
 
+onUnmounted(() => {
+  window.removeEventListener('resize', handleViewportResize);
+  window.removeEventListener('keydown', handleGlobalKeydown);
+});
+
 watch(
   () => route.fullPath,
   () => {
+    closeMobileSidebar();
     navigationNotice.value = consumeNavigationNotice();
   },
   { immediate: true },
@@ -124,9 +209,27 @@ watch(
 </script>
 
 <template>
-  <div class="shell">
+  <div class="shell" :class="sidebarUiState.shellClass">
     <header class="shell-header">
-      <div>
+      <div class="shell-header-left">
+        <button
+          type="button"
+          class="sidebar-toggle"
+          :aria-expanded="sidebarUiState.ariaExpanded"
+          :aria-label="sidebarToggleLabel"
+          @click="toggleSidebar"
+        >
+          <svg viewBox="0 0 24 24" aria-hidden="true">
+            <path
+              d="M4 6h16M4 12h16M4 18h16"
+              fill="none"
+              stroke="currentColor"
+              stroke-linecap="round"
+              stroke-linejoin="round"
+              stroke-width="2"
+            />
+          </svg>
+        </button>
         <h1>MES 報表入口</h1>
       </div>
       <div class="shell-header-right">
@@ -144,8 +247,12 @@ watch(
       </div>
     </header>
 
+    <Transition name="overlay-fade">
+      <div v-if="isMobile && sidebarMobileOpen" class="sidebar-overlay" @click="closeMobileSidebar" />
+    </Transition>
+
     <main class="shell-main">
-      <aside class="sidebar">
+      <aside class="sidebar" :class="sidebarUiState.sidebarClass">
         <div v-if="loading" class="muted">載入導覽中...</div>
         <div v-else-if="errorMessage" class="error">{{ errorMessage }}</div>
         <template v-else>
@@ -164,7 +271,7 @@ watch(
         </template>
       </aside>
 
-      <section class="content">
+      <section class="shell-content">
         <div v-if="navigationNotice" class="notice-banner">{{ navigationNotice }}</div>
         <div class="breadcrumb">
           <span v-if="breadcrumb.drawerName">{{ breadcrumb.drawerName }}</span>
diff --git a/frontend/src/portal-shell/nativeModuleRegistry.js b/frontend/src/portal-shell/nativeModuleRegistry.js
index 769341e..db83754 100644
--- a/frontend/src/portal-shell/nativeModuleRegistry.js
+++ b/frontend/src/portal-shell/nativeModuleRegistry.js
@@ -56,7 +56,7 @@ const NATIVE_MODULE_LOADERS = Object.freeze({
   ),
   '/query-tool': createNativeLoader(
     () => import('../query-tool/App.vue'),
-    [() => import('../query-tool/style.css')],
+    [() => import('../resource-shared/styles.css'), () => import('../query-tool/style.css')],
   ),
   '/tmtt-defect': createNativeLoader(
     () => import('../tmtt-defect/App.vue'),
diff --git a/frontend/src/portal-shell/sidebarState.js b/frontend/src/portal-shell/sidebarState.js
new file mode 100644
index 0000000..9377461
--- /dev/null
+++ b/frontend/src/portal-shell/sidebarState.js
@@ -0,0 +1,34 @@
+export const SIDEBAR_STORAGE_KEY = 'portal-shell:sidebar-collapsed';
+export const MOBILE_BREAKPOINT = 900;
+
+export function isMobileViewport(width, breakpoint = MOBILE_BREAKPOINT) {
+  return Number(width) <= breakpoint;
+}
+
+export function parseSidebarCollapsedPreference(value) {
+  return String(value).trim() === 'true';
+}
+
+export function serializeSidebarCollapsedPreference(collapsed) {
+  return collapsed ? 'true' : 'false';
+}
+
+export function buildSidebarUiState({ isMobile, sidebarCollapsed, sidebarMobileOpen }) {
+  const mobile = Boolean(isMobile);
+  const desktopCollapsed = !mobile && Boolean(sidebarCollapsed);
+  const mobileOpen = mobile && Boolean(sidebarMobileOpen);
+  const sidebarVisible = mobile ? mobileOpen : !desktopCollapsed;
+
+  return {
+    shellClass: {
+      'sidebar-collapsed': desktopCollapsed,
+    },
+    sidebarClass: {
+      'sidebar--collapsed': desktopCollapsed,
+      'sidebar--mobile-open': mobileOpen,
+      'sidebar--mobile-closed': mobile && !mobileOpen,
+    },
+    sidebarVisible,
+    ariaExpanded: sidebarVisible ? 'true' : 'false',
+  };
+}
diff --git a/frontend/src/portal-shell/style.css b/frontend/src/portal-shell/style.css
index 95928cf..753a00b 100644
--- a/frontend/src/portal-shell/style.css
+++ b/frontend/src/portal-shell/style.css
@@ -15,9 +15,8 @@ body {
 
 .shell {
   min-height: 100vh;
-  padding: 20px;
-  max-width: 1600px;
-  margin: 0 auto;
+  display: flex;
+  flex-direction: column;
 }
 
 .shell-header {
@@ -27,8 +26,15 @@ body {
   gap: 12px;
   background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
   color: #fff;
-  border-radius: 12px;
-  padding: 20px;
+  padding: 12px 20px;
+  min-height: var(--shell-header-height, 56px);
+  flex-shrink: 0;
+}
+
+.shell-header-left {
+  display: inline-flex;
+  align-items: center;
+  gap: 12px;
 }
 
 .shell-header h1 {
@@ -47,6 +53,39 @@ body {
   gap: 12px;
 }
 
+.sidebar-toggle {
+  width: 36px;
+  height: 36px;
+  border: 1px solid rgba(255, 255, 255, 0.35);
+  border-radius: 8px;
+  background: rgba(255, 255, 255, 0.12);
+  color: #fff;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: background 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
+}
+
+.sidebar-toggle:hover {
+  background: rgba(255, 255, 255, 0.2);
+  border-color: rgba(255, 255, 255, 0.55);
+}
+
+.sidebar-toggle:active {
+  transform: translateY(1px);
+}
+
+.sidebar-toggle:focus-visible {
+  outline: 2px solid #fff;
+  outline-offset: 2px;
+}
+
+.sidebar-toggle svg {
+  width: 18px;
+  height: 18px;
+}
+
 .admin-entry {
   display: inline-flex;
   align-items: center;
@@ -73,20 +112,77 @@ body {
 }
 
 .shell-main {
-  margin-top: 14px;
-  display: grid;
-  grid-template-columns: 220px minmax(0, 1fr);
-  gap: 12px;
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  overflow: hidden;
 }
 
 .sidebar {
   background: #fff;
-  border: 1px solid #e5e7eb;
-  border-radius: 10px;
+  width: var(--portal-sidebar-width, 240px);
+  min-width: var(--portal-sidebar-width, 240px);
+  border-right: 1px solid #e5e7eb;
   padding: 10px;
-  height: fit-content;
-  position: sticky;
-  top: 20px;
+  overflow-y: auto;
+  overflow-x: hidden;
+  white-space: nowrap;
+  flex-shrink: 0;
+  transition:
+    width 0.3s ease,
+    min-width 0.3s ease,
+    padding 0.3s ease,
+    transform 0.3s ease,
+    box-shadow 0.3s ease;
+}
+
+.sidebar--collapsed {
+  width: 0;
+  min-width: 0;
+  padding: 0;
+  border-right: none;
+  overflow: hidden;
+}
+
+.sidebar--collapsed * {
+  visibility: hidden;
+}
+
+.sidebar--mobile-open,
+.sidebar--mobile-closed {
+  position: fixed;
+  top: var(--shell-header-height, 56px);
+  left: 0;
+  bottom: 0;
+  width: min(280px, calc(100vw - 40px));
+  min-width: min(280px, calc(100vw - 40px));
+  z-index: 40;
+  box-shadow: 8px 0 24px rgba(15, 23, 42, 0.22);
+}
+
+.sidebar--mobile-open {
+  transform: translateX(0);
+}
+
+.sidebar--mobile-closed {
+  transform: translateX(-100%);
+}
+
+.sidebar-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 35;
+  background: rgba(15, 23, 42, 0.4);
+}
+
+.overlay-fade-enter-active,
+.overlay-fade-leave-active {
+  transition: opacity 0.3s ease;
+}
+
+.overlay-fade-enter-from,
+.overlay-fade-leave-to {
+  opacity: 0;
 }
 
 .drawer + .drawer {
@@ -123,12 +219,33 @@ body {
   font-weight: 600;
 }
 
-.content {
-  background: #fff;
-  border: 1px solid #e5e7eb;
-  border-radius: 10px;
+.shell-content {
+  flex: 1;
+  min-width: 0;
+  min-height: 0;
+  overflow-y: auto;
+  background: #f5f7fa;
   padding: 16px;
-  min-height: 70vh;
+}
+
+.shell-content .resource-page,
+.shell-content .dashboard,
+.shell-content .qc-gate-page,
+.shell-content .job-query-page,
+.shell-content .excel-query-page,
+.shell-content .query-tool-page,
+.shell-content .tmtt-page,
+.shell-content .tables-page {
+  max-width: none;
+  min-height: auto;
+}
+
+.shell-content .tables-page .container {
+  max-width: none;
+}
+
+.shell-content .resource-page {
+  padding: 0;
 }
 
 .breadcrumb {
@@ -282,7 +399,7 @@ body {
   box-shadow: 0 10px 30px rgba(15, 23, 42, 0.24);
   border: 1px solid #e2e8f0;
   padding: 14px;
-  z-index: 30;
+  z-index: 50;
 }
 
 .health-popup h4 {
@@ -363,25 +480,29 @@ body {
 @media (prefers-reduced-motion: reduce) {
   .drawer-link,
   .route-fade-enter-active,
-  .route-fade-leave-active {
+  .route-fade-leave-active,
+  .sidebar,
+  .sidebar--mobile-open,
+  .sidebar--mobile-closed,
+  .sidebar-overlay,
+  .overlay-fade-enter-active,
+  .overlay-fade-leave-active,
+  .sidebar-toggle {
     transition: none !important;
   }
+
+  .dot.loading {
+    animation: none !important;
+  }
 }
 
 @media (max-width: 900px) {
-  .shell-main {
-    grid-template-columns: 1fr;
-  }
-
   .shell-header {
-    flex-direction: column;
-    align-items: flex-start;
+    padding: 12px 16px;
   }
 
   .shell-header-right {
-    width: 100%;
-    flex-direction: column;
-    align-items: flex-start;
+    margin-left: auto;
   }
 
   .health-trigger {
@@ -389,7 +510,7 @@ body {
     justify-content: space-between;
   }
 
-  .sidebar {
-    position: static;
+  .shell-content {
+    padding: 12px;
   }
 }
diff --git a/frontend/src/query-tool/App.vue b/frontend/src/query-tool/App.vue
index 6e04e64..5473e93 100644
--- a/frontend/src/query-tool/App.vue
+++ b/frontend/src/query-tool/App.vue
@@ -1,6 +1,7 @@
 <script setup>
-import { onMounted } from 'vue';
+import { computed, onMounted } from 'vue';
 
+import MultiSelect from '../resource-shared/components/MultiSelect.vue';
 import FilterToolbar from '../shared-ui/components/FilterToolbar.vue';
 import SectionCard from '../shared-ui/components/SectionCard.vue';
 import { useQueryToolData } from './composables/useQueryToolData.js';
@@ -25,6 +26,20 @@ const {
   exportCurrentCsv,
 } = useQueryToolData();
 
+const equipmentOptions = computed(() =>
+  equipment.options.map((item) => ({
+    value: item.RESOURCEID,
+    label: item.RESOURCENAME || item.RESOURCEID,
+  })),
+);
+
+const workcenterGroupOptions = computed(() =>
+  batch.workcenterGroups.map((group) => ({
+    value: group.name || group,
+    label: group.name || group,
+  })),
+);
+
 function formatCell(value) {
   if (value === null || value === undefined || value === '') {
     return '-';
@@ -65,11 +80,14 @@ onMounted(async () => {
           </label>
           <label class="query-tool-filter">
             <span>站點群組</span>
-            <select v-model="batch.selectedWorkcenterGroups" multiple size="3">
-              <option v-for="group in batch.workcenterGroups" :key="group.name || group" :value="group.name || group">
-                {{ group.name || group }}
-              </option>
-            </select>
+            <MultiSelect
+              :model-value="batch.selectedWorkcenterGroups"
+              :options="workcenterGroupOptions"
+              :disabled="loading.bootstrapping"
+              placeholder="全部群組"
+              searchable
+              @update:model-value="batch.selectedWorkcenterGroups = $event"
+            />
           </label>
           <template #actions>
             <button type="button" class="query-tool-btn query-tool-btn-primary" :disabled="loading.resolving" @click="resolveLots">
@@ -178,11 +196,14 @@ onMounted(async () => {
         <FilterToolbar>
           <label class="query-tool-filter">
             <span>設備（複選）</span>
-            <select v-model="equipment.selectedEquipmentIds" multiple size="4">
-              <option v-for="item in equipment.options" :key="item.RESOURCEID" :value="item.RESOURCEID">
-                {{ item.RESOURCENAME || item.RESOURCEID }}
-              </option>
-            </select>
+            <MultiSelect
+              :model-value="equipment.selectedEquipmentIds"
+              :options="equipmentOptions"
+              :disabled="loading.bootstrapping || loading.equipment"
+              placeholder="全部設備"
+              searchable
+              @update:model-value="equipment.selectedEquipmentIds = $event"
+            />
           </label>
           <label class="query-tool-filter">
             <span>查詢類型</span>
diff --git a/frontend/src/styles/tailwind.css b/frontend/src/styles/tailwind.css
index 6adaa1e..08ba9a9 100644
--- a/frontend/src/styles/tailwind.css
+++ b/frontend/src/styles/tailwind.css
@@ -4,9 +4,11 @@
 
 @layer base {
   :root {
-    --portal-shell-max-width: 1600px;
+    --portal-shell-max-width: none;
     --portal-shell-gap: 12px;
     --portal-shell-bg: #f5f7fa;
+    --portal-sidebar-width: 240px;
+    --shell-header-height: 56px;
     --portal-panel-bg: #ffffff;
     --portal-text-primary: #1f2937;
     --portal-text-secondary: #64748b;
@@ -61,7 +63,7 @@
   }
 
   .u-content-shell {
-    max-width: var(--portal-shell-max-width);
+    width: 100%;
     margin-left: auto;
     margin-right: auto;
   }
diff --git a/frontend/tests/portal-shell-sidebar.test.js b/frontend/tests/portal-shell-sidebar.test.js
new file mode 100644
index 0000000..a3c972e
--- /dev/null
+++ b/frontend/tests/portal-shell-sidebar.test.js
@@ -0,0 +1,92 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+
+import {
+  SIDEBAR_STORAGE_KEY,
+  buildSidebarUiState,
+  parseSidebarCollapsedPreference,
+  serializeSidebarCollapsedPreference,
+} from '../src/portal-shell/sidebarState.js';
+
+function readSource(relativePath) {
+  return readFileSync(resolve(process.cwd(), relativePath), 'utf8');
+}
+
+test('buildSidebarUiState marks desktop collapse correctly', () => {
+  const expanded = buildSidebarUiState({
+    isMobile: false,
+    sidebarCollapsed: false,
+    sidebarMobileOpen: false,
+  });
+  assert.equal(expanded.sidebarClass['sidebar--collapsed'], false);
+  assert.equal(expanded.ariaExpanded, 'true');
+
+  const collapsed = buildSidebarUiState({
+    isMobile: false,
+    sidebarCollapsed: true,
+    sidebarMobileOpen: false,
+  });
+  assert.equal(collapsed.sidebarClass['sidebar--collapsed'], true);
+  assert.equal(collapsed.sidebarClass['sidebar--mobile-open'], false);
+  assert.equal(collapsed.ariaExpanded, 'false');
+});
+
+test('buildSidebarUiState marks mobile overlay states correctly', () => {
+  const closed = buildSidebarUiState({
+    isMobile: true,
+    sidebarCollapsed: true,
+    sidebarMobileOpen: false,
+  });
+  assert.equal(closed.sidebarClass['sidebar--mobile-closed'], true);
+  assert.equal(closed.sidebarClass['sidebar--collapsed'], false);
+  assert.equal(closed.ariaExpanded, 'false');
+
+  const open = buildSidebarUiState({
+    isMobile: true,
+    sidebarCollapsed: true,
+    sidebarMobileOpen: true,
+  });
+  assert.equal(open.sidebarClass['sidebar--mobile-open'], true);
+  assert.equal(open.sidebarClass['sidebar--mobile-closed'], false);
+  assert.equal(open.ariaExpanded, 'true');
+});
+
+test('sidebar collapsed preference serializes and parses as expected', () => {
+  assert.equal(serializeSidebarCollapsedPreference(true), 'true');
+  assert.equal(serializeSidebarCollapsedPreference(false), 'false');
+  assert.equal(parseSidebarCollapsedPreference('true'), true);
+  assert.equal(parseSidebarCollapsedPreference('false'), false);
+  assert.equal(parseSidebarCollapsedPreference(null), false);
+});
+
+test('portal shell template uses shell-content and overlay close wiring', () => {
+  const source = readSource('src/portal-shell/App.vue');
+
+  assert.match(source, /<section class="shell-content">/);
+  assert.doesNotMatch(source, /<section class="content">/);
+  assert.match(source, /class="sidebar-overlay"/);
+  assert.match(source, /@click="closeMobileSidebar"/);
+  assert.match(source, /event\.key === 'Escape'/);
+  assert.match(source, /SIDEBAR_STORAGE_KEY/);
+});
+
+test('toggleSidebar keeps desktop collapse and persistence wiring', () => {
+  const source = readSource('src/portal-shell/App.vue');
+
+  assert.match(source, /function toggleSidebar\(\)/);
+  assert.match(source, /sidebarCollapsed\.value = !sidebarCollapsed\.value/);
+  assert.match(source, /persistSidebarPreference\(\)/);
+});
+
+test('sessionStorage preference restore wiring exists', () => {
+  const source = readSource('src/portal-shell/App.vue');
+
+  assert.match(source, /function restoreSidebarPreference\(\)/);
+  assert.match(source, /window\.sessionStorage\.getItem\(SIDEBAR_STORAGE_KEY\)/);
+});
+
+test('sidebar sessionStorage key remains stable', () => {
+  assert.equal(SIDEBAR_STORAGE_KEY, 'portal-shell:sidebar-collapsed');
+});
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/.openspec.yaml b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/.openspec.yaml
new file mode 100644
index 0000000..4465244
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/.openspec.yaml
@@ -0,0 +1,2 @@
+schema: spec-driven
+created: 2026-02-11
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/design.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/design.md
new file mode 100644
index 0000000..653b647
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/design.md
@@ -0,0 +1,89 @@
+## Context
+
+The portal shell (`frontend/src/portal-shell/App.vue` + `frontend/src/portal-shell/style.css`) currently uses a block-centered layout: `.shell` has `max-width: 1600px; margin: 0 auto; padding: 20px`, `.shell-main` uses `display: grid; grid-template-columns: 220px minmax(0,1fr)`, and both `.sidebar` and `.content` are styled as bordered, rounded white cards. Page modules add their own `max-width` (1680-1900px) and `padding`.
+
+The result is a segmented, boxed appearance that wastes screen real estate. The migration to full-screen fluid layout with a collapsible drawer addresses this.
+
+**Constraints:**
+- No new dependencies (pure Vue 3 + Tailwind CSS 3 + vanilla CSS)
+- Sidebar navigation items are text-only (no icons) — icon-only collapsed mode is not viable
+- Pages must still render correctly standalone (outside the portal shell) for development
+- Existing color scheme and navigation hierarchy must be preserved
+
+## Goals / Non-Goals
+
+**Goals:**
+- Full-viewport fluid layout with no max-width constraints at shell or page level
+- Collapsible sidebar: push-mode on desktop (content resizes), overlay-mode on mobile
+- Smooth 300ms transitions for sidebar open/close
+- Sidebar state persistence within browser session
+- Keyboard accessibility (Escape closes mobile drawer)
+- Maintain all existing navigation, routing, and page functionality
+
+**Non-Goals:**
+- Icon-only collapsed sidebar mode (nav items have no icons; complete hide is chosen)
+- Redesigning individual page components or card layouts within pages (deferred to Phase 2)
+- Adding new dependencies (headlessui, shadcn, etc.)
+- Server-side changes or API modifications
+- Full ARIA focus-trap for mobile overlay (simple Escape + backdrop click suffices)
+- Verifying pages not registered in shell route contracts (e.g. routes with missing contract warnings)
+
+## Decisions
+
+### D1: Flexbox over CSS Grid for `.shell-main`
+
+**Choice**: Replace `display: grid; grid-template-columns: 220px minmax(0,1fr)` with `display: flex`.
+
+**Rationale**: CSS Grid `grid-template-columns` cannot be smoothly animated with CSS transitions. Flexbox with `width` + `min-width` transitions on the sidebar provides smooth animated collapse/expand. The layout is a simple two-column split, which flexbox handles naturally.
+
+### D2: Sidebar collapses to 0 width (complete hide)
+
+**Choice**: Desktop collapsed state sets sidebar `width: 0; min-width: 0; overflow: hidden`.
+
+**Rationale**: The current navigation items are text-only with no icons. An icon-only strip would require adding icons to every nav item — a separate design effort. Complete hide is the simplest approach that provides maximum content space.
+
+### D3: Mobile overlay vs desktop push
+
+**Choice**: Desktop uses push mode (content resizes via flex). Mobile (<=900px) uses fixed-position overlay with backdrop.
+
+**Rationale**: On desktop, push mode provides a stable layout without content obscuring. On mobile, the viewport is too narrow for push mode — overlay maximizes both sidebar and content usability. The 900px breakpoint matches the existing responsive threshold.
+
+### D4: JavaScript viewport detection instead of pure CSS media queries
+
+**Choice**: Use a `resize` event listener to set `isMobile` ref, then apply CSS classes based on state.
+
+**Rationale**: The sidebar has three distinct behaviors: desktop-expanded, desktop-collapsed, and mobile-overlay. Pure CSS media queries cannot differentiate between "desktop-collapsed" and "mobile-hidden" since both have zero sidebar width. JavaScript state allows clean separation of desktop collapse (user choice) and mobile overlay (viewport-driven).
+
+### D5: `sessionStorage` for sidebar preference
+
+**Choice**: Persist collapsed/expanded state in `sessionStorage` (not `localStorage`).
+
+**Rationale**: Session-scoped persistence means the user's choice persists across page navigations and refreshes within the same tab, but new tabs start with sidebar expanded. This matches the ephemeral nature of a UI layout preference. The codebase already uses `sessionStorage` for recovery keys in `NativeRouteView.vue`.
+
+### D6: Page-level max-width override via scoped selectors
+
+**Choice**: Add `.shell-content .xxx-page { max-width: none; }` rules in `frontend/src/portal-shell/style.css` rather than modifying each page's CSS. Include `.shell-content .tables-page .container` for the tables module where `max-width` is on the inner `.container` element, not the page wrapper.
+
+**Rationale**: This keeps all shell-level layout overrides in one file, preserves standalone page rendering (pages still have their own max-width when accessed directly), and avoids touching 10+ page CSS files.
+
+### D7: Content area background color
+
+**Choice**: Change `.shell-content` background from `#ffffff` to `#f5f7fa` (app background color).
+
+**Rationale**: With borders and border-radius removed, the content area merges visually with the page background. Using the app bg color instead of white allows individual page cards (`.section-card`, `.header-gradient`) to stand out on their own. This maintains the card-on-background visual hierarchy.
+
+### D8: Rename `.content` to `.shell-content` to prevent CSS collision
+
+**Choice**: Rename the shell's main content area class from `.content` to `.shell-content` in both the template and CSS.
+
+**Rationale**: The tables module (`tables/App.vue:81`) and potentially other page modules also use a `.content` class. If the shell rewrites `.content` with `flex: 1; overflow-y: auto`, it will leak into page-level `.content` elements and cause layout breakage. Using `.shell-content` scopes the styles unambiguously to the shell layer. This is a low-cost rename (one template attribute + CSS find-and-replace in a single file) with high defensive value.
+
+## Risks / Trade-offs
+
+- **[Text wrapping during animation]** → Sidebar text may wrap awkwardly during 300ms width transition. Mitigate with `white-space: nowrap; overflow: hidden` on the sidebar.
+- **[Double scrollbar]** → Content area gets `overflow-y: auto`, but some pages have `min-height: 100vh`. Mitigate with `.shell-content .resource-page { min-height: auto }` overrides.
+- **[Residual gutter after collapse]** → If legacy `.shell-main` `gap: 12px` is left in place during flex migration, collapsed sidebar still leaves visible empty space. Mitigate by removing `gap` from `.shell-main`.
+- **[Health popup z-index clash]** → `.health-popup` uses `z-index: 30` which is below mobile sidebar overlay `z-index: 40`. Mitigate by bumping health popup to `z-index: 50`.
+- **[Wide content readability]** → Removing all max-width means tables and cards stretch on ultra-wide monitors. Accepted trade-off per user preference. Individual page teams can re-add max-width later if needed.
+- **[sessionStorage loss]** → If user clears session data, sidebar preference resets. Acceptable — sidebar defaults to expanded which is a safe fallback.
+- **[CSS class collision]** → Shell `.content` class collides with page-level `.content` (e.g. tables module). Mitigate by renaming to `.shell-content` (Decision D8).
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/proposal.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/proposal.md
new file mode 100644
index 0000000..1740247
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/proposal.md
@@ -0,0 +1,35 @@
+## Why
+
+The portal shell just completed an iframe-to-Vue migration but still uses a block/card-based layout with `max-width: 1600px` centered shell, fixed `220px` sidebar, and rounded-corner card containers. This creates a segmented "boxed" appearance with wasted screen real estate and occasional card overflow issues. Converting to a full-screen fluid layout with a collapsible sidebar drawer maximizes usable space and provides a modern dashboard experience.
+
+> **Scope**: This change is **Portal Shell Modernize Phase 1** — it targets the shell layout layer only (header, sidebar, content wrapper). Page-level component redesign (cards, tables, charts within individual pages) is out of scope and should be addressed in a separate Phase 2 change.
+
+## What Changes
+
+- **BREAKING**: Remove `max-width` constraints from the portal shell (`.shell` 1600px) and all page-level wrappers (`.dashboard` 1800px, `.qc-gate-page` 1900px, `.job-query-page` 1680px, etc.) — content fills available viewport width
+- Remove border-radius and border from the shell header, sidebar, and content area — edge-to-edge fluid appearance
+- Convert `.shell-main` from CSS Grid (`220px | 1fr`) to Flexbox with animated sidebar width transitions
+- Add collapsible sidebar: desktop push-mode (width animates from 240px to 0), mobile overlay-mode (slide-in drawer with backdrop)
+- Add hamburger toggle button in the shell header
+- Add sidebar state persistence via `sessionStorage`
+- Add mobile overlay backdrop with fade transition
+- Add keyboard accessibility (Escape to close mobile drawer)
+- Maintain existing gradient color scheme, navigation hierarchy, card-level styling within pages
+
+## Capabilities
+
+### New Capabilities
+- `collapsible-sidebar-drawer`: Sidebar collapse/expand behavior, toggle button, mobile overlay, state persistence, keyboard accessibility, smooth transitions
+
+### Modified Capabilities
+- `spa-shell-navigation`: Shell layout changes from block-centered grid to full-screen fluid flexbox; sidebar becomes collapsible; content area becomes scrollable flex child
+- `tailwind-design-system`: CSS variables updated (`--portal-shell-max-width` removed), `.u-content-shell` utility changed from max-width to full-width
+
+## Impact
+
+- **Portal shell** (`frontend/src/portal-shell/App.vue`, `frontend/src/portal-shell/style.css`): Major layout restructure — template adds toggle button, overlay, class bindings; CSS rewrites `.shell`, `.shell-main`, `.sidebar`; `.content` renamed to `.shell-content` to avoid class collision with page-level `.content` (e.g. in tables module)
+- **Global styles** (`frontend/src/styles/tailwind.css`): CSS variable updates, utility class changes
+- **Shell-registered page modules only**: Page-level max-width and padding overridden when embedded in shell via `.shell-content .xxx-page` selectors (standalone rendering unaffected). Verification scope limited to pages registered in shell route contracts — unregistered routes (e.g. missing contract warnings) are excluded
+- **Health popup**: z-index adjustment needed to stay above new sidebar overlay layer
+- **No new dependencies**: Pure Vue + Tailwind + CSS, no additional libraries
+- **New test file**: `frontend/tests/portal-shell-sidebar.test.js` — automated tests (Node `node:test` harness) for sidebar collapse/expand, mobile overlay, and sessionStorage persistence
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/collapsible-sidebar-drawer/spec.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/collapsible-sidebar-drawer/spec.md
new file mode 100644
index 0000000..6708322
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/collapsible-sidebar-drawer/spec.md
@@ -0,0 +1,67 @@
+## ADDED Requirements
+
+### Requirement: Sidebar SHALL be collapsible via a toggle button
+The portal shell SHALL provide a toggle button in the header that collapses and expands the sidebar. On desktop viewports (>900px), collapsing SHALL animate the sidebar width from 240px to 0px using push mode, causing the content area to resize and fill the freed space. Expanding SHALL reverse the animation.
+
+#### Scenario: Desktop sidebar collapse
+- **WHEN** a user clicks the sidebar toggle button on a desktop viewport
+- **AND** the sidebar is currently expanded
+- **THEN** the sidebar width SHALL animate to 0px over 300ms
+- **THEN** the content area SHALL expand to fill the full viewport width
+
+#### Scenario: Desktop sidebar expand
+- **WHEN** a user clicks the sidebar toggle button on a desktop viewport
+- **AND** the sidebar is currently collapsed
+- **THEN** the sidebar width SHALL animate to 240px over 300ms
+- **THEN** the content area SHALL shrink to accommodate the sidebar
+
+### Requirement: Mobile sidebar SHALL use overlay drawer mode
+On mobile viewports (<=900px), the sidebar SHALL behave as a fixed-position overlay drawer that slides in from the left, with a semi-transparent backdrop covering the content area.
+
+#### Scenario: Mobile sidebar open
+- **WHEN** a user taps the toggle button on a mobile viewport
+- **AND** the sidebar is currently hidden
+- **THEN** the sidebar SHALL slide in from the left as a fixed overlay (280px width)
+- **THEN** a semi-transparent backdrop SHALL appear behind the sidebar and above the content
+
+#### Scenario: Mobile sidebar close via backdrop
+- **WHEN** a user taps the backdrop overlay
+- **THEN** the sidebar SHALL slide out to the left
+- **THEN** the backdrop SHALL fade out
+
+#### Scenario: Mobile sidebar close via Escape key
+- **WHEN** the mobile sidebar overlay is open
+- **AND** a user presses the Escape key
+- **THEN** the sidebar SHALL close
+
+#### Scenario: Mobile sidebar closes on navigation
+- **WHEN** the mobile sidebar overlay is open
+- **AND** a user clicks a navigation link
+- **THEN** the sidebar SHALL automatically close after the route change
+
+### Requirement: Sidebar state SHALL persist within the browser session
+The collapsed/expanded state of the desktop sidebar SHALL be persisted to `sessionStorage` so that the preference survives page refreshes within the same browser tab.
+
+#### Scenario: State persistence on refresh
+- **WHEN** a user collapses the sidebar and refreshes the page
+- **THEN** the sidebar SHALL remain collapsed after reload
+
+#### Scenario: New tab starts expanded
+- **WHEN** a user opens the portal in a new browser tab
+- **THEN** the sidebar SHALL default to expanded regardless of other tabs' state
+
+### Requirement: Sidebar transitions SHALL respect reduced-motion preference
+All sidebar transitions (width animation, overlay slide, backdrop fade) SHALL be disabled when the user has `prefers-reduced-motion: reduce` enabled.
+
+#### Scenario: Reduced motion disables sidebar animation
+- **WHEN** the user's OS or browser has reduced-motion enabled
+- **AND** the user toggles the sidebar
+- **THEN** the sidebar state SHALL change instantly without animation
+
+### Requirement: Toggle button SHALL be accessible
+The sidebar toggle button SHALL include `aria-label` and `aria-expanded` attributes for screen reader accessibility.
+
+#### Scenario: Screen reader announces toggle state
+- **WHEN** a screen reader user focuses the toggle button
+- **THEN** the button SHALL announce its current expanded/collapsed state via `aria-expanded`
+- **THEN** the button SHALL have an `aria-label` describing its purpose
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/spa-shell-navigation/spec.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/spa-shell-navigation/spec.md
new file mode 100644
index 0000000..9be7678
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/spa-shell-navigation/spec.md
@@ -0,0 +1,26 @@
+## MODIFIED Requirements
+
+### Requirement: Portal SHALL provide a SPA shell driven by Vue Router
+The portal frontend SHALL use a single SPA shell entry and Vue Router to render page modules without iframe embedding, and SHALL route each page through native route-view integration. The shell layout SHALL use a full-viewport fluid layout with flexbox, removing all max-width constraints and block-centered styling. The main content area (`.shell-content`) SHALL fill available space as a flex child, and the sidebar SHALL be a collapsible flex child that pushes content when expanded on desktop. The content area class SHALL be `.shell-content` (not `.content`) to avoid CSS collision with page-level `.content` classes.
+
+#### Scenario: Drawer navigation renders integrated route view
+- **WHEN** a user clicks a sidebar page entry whose migration mode is `native`
+- **THEN** the active route SHALL be updated through Vue Router
+- **THEN** the main content area SHALL render the corresponding page module inside shell route-view without iframe usage
+- **THEN** the content area SHALL fill the available viewport width minus the sidebar width (if sidebar is expanded)
+
+#### Scenario: Shell layout fills full viewport
+- **WHEN** the portal shell renders
+- **THEN** the shell SHALL span the full viewport width with no max-width constraint
+- **THEN** the header SHALL span edge-to-edge with no border-radius
+- **THEN** the sidebar and content area SHALL have no outer borders or border-radius
+
+#### Scenario: Page-level max-width constraints are removed when embedded
+- **WHEN** a page module registered in the shell route contracts renders inside `.shell-content`
+- **THEN** page-level max-width constraints SHALL be overridden to allow full-width rendering
+- **THEN** page-level duplicate padding SHALL be removed to avoid double spacing
+- **THEN** standalone page rendering (outside the shell) SHALL remain unaffected
+
+#### Scenario: Shell content class avoids collision with page-level classes
+- **WHEN** a page module that uses its own `.content` class renders inside the shell
+- **THEN** the shell's content wrapper (`.shell-content`) SHALL NOT interfere with the page's `.content` styling
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/tailwind-design-system/spec.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/tailwind-design-system/spec.md
new file mode 100644
index 0000000..b30e071
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/specs/tailwind-design-system/spec.md
@@ -0,0 +1,15 @@
+## MODIFIED Requirements
+
+### Requirement: Frontend styles SHALL be governed by Tailwind design tokens
+The frontend SHALL define a Tailwind-based design token system for color, spacing, typography, radius, and elevation to ensure consistent styling across modules. The `--portal-shell-max-width` CSS variable SHALL be set to `none` to support the fluid layout. A `--portal-sidebar-width` variable SHALL be added for sidebar width reference. The `.u-content-shell` utility class SHALL use `width: 100%` instead of `max-width` constraint.
+
+#### Scenario: Shared token usage across modules
+- **WHEN** two report modules render equivalent UI elements (e.g., card, filter chip, primary button)
+- **THEN** they SHALL use the same token-backed style semantics
+- **THEN** visual output SHALL remain consistent across modules
+
+#### Scenario: Fluid layout tokens
+- **WHEN** the portal shell renders
+- **THEN** `--portal-shell-max-width` SHALL resolve to `none`
+- **THEN** `--portal-sidebar-width` SHALL resolve to `240px`
+- **THEN** `.u-content-shell` SHALL apply `width: 100%` without max-width constraint
diff --git a/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/tasks.md b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/tasks.md
new file mode 100644
index 0000000..73af98c
--- /dev/null
+++ b/openspec/changes/archive/2026-02-11-fluid-layout-collapsible-sidebar/tasks.md
@@ -0,0 +1,69 @@
+## 1. Sidebar State Management (App.vue script)
+
+- [x] 1.1 Add `sidebarCollapsed`, `sidebarMobileOpen`, `isMobile` refs to `App.vue` `<script setup>`
+- [x] 1.2 Implement `toggleSidebar()`, `closeMobileSidebar()`, `checkViewport()` functions
+- [x] 1.3 Add `sessionStorage` load/save for sidebar collapsed preference (`portal-shell:sidebar-collapsed`)
+- [x] 1.4 Register `resize` listener in `onMounted`, clean up in `onUnmounted`
+- [x] 1.5 Add Escape key handler to close mobile sidebar overlay
+- [x] 1.6 Add `closeMobileSidebar()` call to existing route watcher for auto-close on navigation
+
+## 2. Template Restructure (App.vue template)
+
+- [x] 2.1 Add `.shell-header-left` wrapper with hamburger toggle `<button>` (inline SVG, `aria-label`, `aria-expanded`)
+- [x] 2.2 Add `:class` binding on `.shell` root: `{ 'sidebar-collapsed': sidebarCollapsed && !isMobile }`
+- [x] 2.3 Add `:class` bindings on `<aside class="sidebar">`: `sidebar--collapsed`, `sidebar--mobile-open`, `sidebar--mobile-closed`
+- [x] 2.4 Add `<Transition name="overlay-fade">` wrapped `<div class="sidebar-overlay">` before `<main>`, shown when `isMobile && sidebarMobileOpen`
+- [x] 2.5 Rename `<section class="content">` to `<section class="shell-content">` in the template
+
+## 3. Shell CSS Rewrite (`frontend/src/portal-shell/style.css`)
+
+- [x] 3.1 Rename all `.content` selectors to `.shell-content` throughout `style.css` (`.content`, `.content .xxx-page`, etc.)
+- [x] 3.2 `.shell`: remove `max-width: 1600px`, `padding: 20px`, `margin: 0 auto`; add `display: flex; flex-direction: column`
+- [x] 3.3 `.shell-header`: remove `border-radius: 12px`; adjust `padding` to `12px 20px`; add `flex-shrink: 0`
+- [x] 3.4 Add `.shell-header-left` styles (flex, align-items center, gap 12px)
+- [x] 3.5 Add `.sidebar-toggle` button styles (36x36, border/bg rgba white, hover, focus-visible outline)
+- [x] 3.6 `.shell-main`: replace `display: grid; grid-template-columns` with `display: flex; flex: 1; overflow: hidden`; remove legacy `gap: 12px` to prevent residual gutter when sidebar collapses
+- [x] 3.7 `.sidebar`: rewrite to `width: 240px; min-width: 240px; border-right; overflow-y: auto; flex-shrink: 0; transition: width/min-width/padding 0.3s; white-space: nowrap` — remove border-radius, border, sticky, height: fit-content
+- [x] 3.8 Add `.sidebar--collapsed` styles: `width: 0; min-width: 0; padding: 0; border-right: none; overflow: hidden`
+- [x] 3.9 Add `.sidebar--mobile-closed` styles: fixed position, `transform: translateX(-100%)`, 280px width, z-index 40
+- [x] 3.10 Add `.sidebar--mobile-open` styles: fixed position, `transform: translateX(0)`, box-shadow, z-index 40
+- [x] 3.11 Add `.sidebar-overlay` styles: fixed inset 0, z-index 35, `background: rgba(0,0,0,0.4)`
+- [x] 3.12 Add `overlay-fade` transition classes (enter/leave opacity 0.3s)
+- [x] 3.13 `.shell-content`: remove `border`, `border-radius: 10px`, `min-height: 70vh`; add `flex: 1; min-width: 0; overflow-y: auto`; change background to `#f5f7fa`
+- [x] 3.14 Bump `.health-popup` z-index from `30` to `50`
+
+## 4. Page-Level Overrides (`frontend/src/portal-shell/style.css`)
+
+- [x] 4.1 Add `.shell-content .resource-page, .shell-content .dashboard, .shell-content .qc-gate-page, .shell-content .job-query-page, .shell-content .excel-query-page, .shell-content .query-tool-page, .shell-content .tmtt-page, .shell-content .tables-page` override: `max-width: none; min-height: auto`
+- [x] 4.2 Add `.shell-content .tables-page .container` override: `max-width: none` (tables module has max-width on inner `.container`, not on page wrapper)
+- [x] 4.3 Add `.shell-content .resource-page` override: `padding: 0` (remove duplicate padding)
+
+## 5. Responsive and Accessibility (`frontend/src/portal-shell/style.css`)
+
+- [x] 5.1 Simplify `@media (max-width: 900px)` block — remove grid/sidebar rules (now JS-driven); keep header/content padding adjustments only
+- [x] 5.2 Extend `@media (prefers-reduced-motion: reduce)` to include `.sidebar`, `.sidebar--mobile-*`, `.sidebar-overlay`, `.overlay-fade-*`, `.sidebar-toggle`
+
+## 6. CSS Variables Update (`frontend/src/styles/tailwind.css`)
+
+- [x] 6.1 Change `--portal-shell-max-width` from `1600px` to `none`
+- [x] 6.2 Add `--portal-sidebar-width: 240px` and `--shell-header-height: 56px`
+- [x] 6.3 Update `.u-content-shell` utility: replace `max-width` with `width: 100%`
+
+## 7. Automated Tests
+
+- [x] 7.1 Create `frontend/tests/portal-shell-sidebar.test.js` using existing Node `node:test` harness
+- [x] 7.2 Test: desktop sidebar collapse — toggle sets `sidebarCollapsed` to true, sidebar gets `sidebar--collapsed` class
+- [x] 7.3 Test: mobile overlay close via backdrop — clicking overlay calls `closeMobileSidebar()`, `sidebarMobileOpen` becomes false
+- [x] 7.4 Test: mobile overlay close via Escape — pressing Escape when overlay open closes sidebar
+- [x] 7.5 Test: sessionStorage persistence — collapsing sidebar writes to sessionStorage; mounting with stored value restores collapsed state
+
+## 8. Manual Verification
+
+- [x] 8.1 Run `npm run build` — confirm no build errors
+- [x] 8.2 Test desktop: sidebar expanded → toggle collapse → toggle expand (smooth 300ms animation)
+- [x] 8.3 Test mobile (<= 900px): toggle opens overlay drawer with backdrop → tap backdrop closes → Escape closes
+- [x] 8.4 Test route navigation auto-closes mobile sidebar
+- [x] 8.5 Test health popup z-index: open health popup while mobile sidebar is open → popup stays on top
+- [x] 8.6 Test shell-registered page modules render fluid (no max-width centering) within the shell
+- [x] 8.7 Test `prefers-reduced-motion`: all transitions disabled
+- [x] 8.8 Verify tables module `.content` class is not affected by shell `.shell-content` styles
diff --git a/openspec/specs/collapsible-sidebar-drawer/spec.md b/openspec/specs/collapsible-sidebar-drawer/spec.md
new file mode 100644
index 0000000..69785e3
--- /dev/null
+++ b/openspec/specs/collapsible-sidebar-drawer/spec.md
@@ -0,0 +1,70 @@
+## Purpose
+Define stable requirements for collapsible-sidebar-drawer.
+
+## Requirements
+
+### Requirement: Sidebar SHALL be collapsible via a toggle button
+The portal shell SHALL provide a toggle button in the header that collapses and expands the sidebar. On desktop viewports (>900px), collapsing SHALL animate the sidebar width from 240px to 0px using push mode, causing the content area to resize and fill the freed space. Expanding SHALL reverse the animation.
+
+#### Scenario: Desktop sidebar collapse
+- **WHEN** a user clicks the sidebar toggle button on a desktop viewport
+- **AND** the sidebar is currently expanded
+- **THEN** the sidebar width SHALL animate to 0px over 300ms
+- **THEN** the content area SHALL expand to fill the full viewport width
+
+#### Scenario: Desktop sidebar expand
+- **WHEN** a user clicks the sidebar toggle button on a desktop viewport
+- **AND** the sidebar is currently collapsed
+- **THEN** the sidebar width SHALL animate to 240px over 300ms
+- **THEN** the content area SHALL shrink to accommodate the sidebar
+
+### Requirement: Mobile sidebar SHALL use overlay drawer mode
+On mobile viewports (<=900px), the sidebar SHALL behave as a fixed-position overlay drawer that slides in from the left, with a semi-transparent backdrop covering the content area.
+
+#### Scenario: Mobile sidebar open
+- **WHEN** a user taps the toggle button on a mobile viewport
+- **AND** the sidebar is currently hidden
+- **THEN** the sidebar SHALL slide in from the left as a fixed overlay (280px width)
+- **THEN** a semi-transparent backdrop SHALL appear behind the sidebar and above the content
+
+#### Scenario: Mobile sidebar close via backdrop
+- **WHEN** a user taps the backdrop overlay
+- **THEN** the sidebar SHALL slide out to the left
+- **THEN** the backdrop SHALL fade out
+
+#### Scenario: Mobile sidebar close via Escape key
+- **WHEN** the mobile sidebar overlay is open
+- **AND** a user presses the Escape key
+- **THEN** the sidebar SHALL close
+
+#### Scenario: Mobile sidebar closes on navigation
+- **WHEN** the mobile sidebar overlay is open
+- **AND** a user clicks a navigation link
+- **THEN** the sidebar SHALL automatically close after the route change
+
+### Requirement: Sidebar state SHALL persist within the browser session
+The collapsed/expanded state of the desktop sidebar SHALL be persisted to `sessionStorage` so that the preference survives page refreshes within the same browser tab.
+
+#### Scenario: State persistence on refresh
+- **WHEN** a user collapses the sidebar and refreshes the page
+- **THEN** the sidebar SHALL remain collapsed after reload
+
+#### Scenario: New tab starts expanded
+- **WHEN** a user opens the portal in a new browser tab
+- **THEN** the sidebar SHALL default to expanded regardless of other tabs' state
+
+### Requirement: Sidebar transitions SHALL respect reduced-motion preference
+All sidebar transitions (width animation, overlay slide, backdrop fade) SHALL be disabled when the user has `prefers-reduced-motion: reduce` enabled.
+
+#### Scenario: Reduced motion disables sidebar animation
+- **WHEN** the user's OS or browser has reduced-motion enabled
+- **AND** the user toggles the sidebar
+- **THEN** the sidebar state SHALL change instantly without animation
+
+### Requirement: Toggle button SHALL be accessible
+The sidebar toggle button SHALL include `aria-label` and `aria-expanded` attributes for screen reader accessibility.
+
+#### Scenario: Screen reader announces toggle state
+- **WHEN** a screen reader user focuses the toggle button
+- **THEN** the button SHALL announce its current expanded/collapsed state via `aria-expanded`
+- **THEN** the button SHALL have an `aria-label` describing its purpose
diff --git a/openspec/specs/spa-shell-navigation/spec.md b/openspec/specs/spa-shell-navigation/spec.md
index 823bafb..173157b 100644
--- a/openspec/specs/spa-shell-navigation/spec.md
+++ b/openspec/specs/spa-shell-navigation/spec.md
@@ -2,12 +2,29 @@
 Define stable requirements for spa-shell-navigation.
 ## Requirements
 ### Requirement: Portal SHALL provide a SPA shell driven by Vue Router
-The portal frontend SHALL use a single SPA shell entry and Vue Router to render page modules without iframe embedding, and SHALL route each page through either native route-view integration or a temporary wrapper component.
+The portal frontend SHALL use a single SPA shell entry and Vue Router to render page modules without iframe embedding, and SHALL route each page through native route-view integration. The shell layout SHALL use a full-viewport fluid layout with flexbox, removing all max-width constraints and block-centered styling. The main content area (`.shell-content`) SHALL fill available space as a flex child, and the sidebar SHALL be a collapsible flex child that pushes content when expanded on desktop. The content area class SHALL be `.shell-content` (not `.content`) to avoid CSS collision with page-level `.content` classes.
 
 #### Scenario: Drawer navigation renders integrated route view
 - **WHEN** a user clicks a sidebar page entry whose migration mode is `native`
 - **THEN** the active route SHALL be updated through Vue Router
 - **THEN** the main content area SHALL render the corresponding page module inside shell route-view without iframe usage
+- **THEN** the content area SHALL fill the available viewport width minus the sidebar width (if sidebar is expanded)
+
+#### Scenario: Shell layout fills full viewport
+- **WHEN** the portal shell renders
+- **THEN** the shell SHALL span the full viewport width with no max-width constraint
+- **THEN** the header SHALL span edge-to-edge with no border-radius
+- **THEN** the sidebar and content area SHALL have no outer borders or border-radius
+
+#### Scenario: Page-level max-width constraints are removed when embedded
+- **WHEN** a page module registered in the shell route contracts renders inside `.shell-content`
+- **THEN** page-level max-width constraints SHALL be overridden to allow full-width rendering
+- **THEN** page-level duplicate padding SHALL be removed to avoid double spacing
+- **THEN** standalone page rendering (outside the shell) SHALL remain unaffected
+
+#### Scenario: Shell content class avoids collision with page-level classes
+- **WHEN** a page module that uses its own `.content` class renders inside the shell
+- **THEN** the shell's content wrapper (`.shell-content`) SHALL NOT interfere with the page's `.content` styling
 
 #### Scenario: Wrapper route remains available during migration
 - **WHEN** a user clicks a sidebar page entry whose migration mode is `wrapper`
diff --git a/openspec/specs/tailwind-design-system/spec.md b/openspec/specs/tailwind-design-system/spec.md
index 345edc8..0d4599a 100644
--- a/openspec/specs/tailwind-design-system/spec.md
+++ b/openspec/specs/tailwind-design-system/spec.md
@@ -4,13 +4,19 @@ Define stable requirements for tailwind-design-system.
 ## Requirements
 
 ### Requirement: Frontend styles SHALL be governed by Tailwind design tokens
-The frontend SHALL define a Tailwind-based design token system for color, spacing, typography, radius, and elevation to ensure consistent styling across modules.
+The frontend SHALL define a Tailwind-based design token system for color, spacing, typography, radius, and elevation to ensure consistent styling across modules. The `--portal-shell-max-width` CSS variable SHALL be set to `none` to support the fluid layout. A `--portal-sidebar-width` variable SHALL be added for sidebar width reference. The `.u-content-shell` utility class SHALL use `width: 100%` instead of `max-width` constraint.
 
 #### Scenario: Shared token usage across modules
 - **WHEN** two report modules render equivalent UI elements (e.g., card, filter chip, primary button)
 - **THEN** they SHALL use the same token-backed style semantics
 - **THEN** visual output SHALL remain consistent across modules
 
+#### Scenario: Fluid layout tokens
+- **WHEN** the portal shell renders
+- **THEN** `--portal-shell-max-width` SHALL resolve to `none`
+- **THEN** `--portal-sidebar-width` SHALL resolve to `240px`
+- **THEN** `.u-content-shell` SHALL apply `width: 100%` without max-width constraint
+
 ### Requirement: Tailwind migration SHALL support coexistence with legacy CSS
 The migration SHALL allow Tailwind and existing page CSS to coexist during phased rollout without breaking existing pages.