diff --git a/services/web/app/src/Features/Errors/ErrorController.mjs b/services/web/app/src/Features/Errors/ErrorController.mjs
index 810c44ef1c..a03963d074 100644
--- a/services/web/app/src/Features/Errors/ErrorController.mjs
+++ b/services/web/app/src/Features/Errors/ErrorController.mjs
@@ -5,14 +5,26 @@ import {
 } from '@overleaf/validation-tools'
 import Errors, { NotFoundError } from './Errors.js'
 import SessionManager from '../Authentication/SessionManager.mjs'
+import UserGetter from '../User/UserGetter.mjs'
 import SamlLogHandler from '../SamlLog/SamlLogHandler.mjs'
 import HttpErrorHandler from './HttpErrorHandler.mjs'
 import { plainTextResponse } from '../../infrastructure/Response.mjs'
 import { expressifyErrorHandler } from '@overleaf/promise-utils'
 
-function notFound(req, res) {
+async function notFound(req, res) {
   res.status(404)
-  res.render('general/404', { title: 'page_not_found' })
+  const sessionUser = SessionManager.getSessionUser(req.session)
+  let isLumiere = false
+  if (sessionUser?._id) {
+    try {
+      const user = await UserGetter.promises.getUser(sessionUser._id, {
+        'ace.overallTheme': 1,
+        signUpDate: 1,
+      })
+      isLumiere = (user?.ace?.overallTheme ?? '') === 'lumiere-'
+    } catch {}
+  }
+  res.render('general/404', { title: 'page_not_found', isLumiere })
 }
 
 function forbidden(req, res) {
diff --git a/services/web/app/views/layout-base.pug b/services/web/app/views/layout-base.pug
index 8691b39969..1556a93b9e 100644
--- a/services/web/app/views/layout-base.pug
+++ b/services/web/app/views/layout-base.pug
@@ -106,6 +106,7 @@ html(
 			'red-nav-bar-for-admins': !settings.isDevEnv && hasFeature('saas') && hasAdminAccess(),
 		}
 		data-theme='light'
+		data-lumiere=isLumiere ? 'true' : 'false'
 	)
 		if settings.recaptcha && settings.recaptcha.siteKeyV3
 			script(
diff --git a/services/web/frontend/js/features/project-list/components/project-list-lumiere.tsx b/services/web/frontend/js/features/project-list/components/project-list-lumiere.tsx
index 3f77935149..33e656c9fd 100644
--- a/services/web/frontend/js/features/project-list/components/project-list-lumiere.tsx
+++ b/services/web/frontend/js/features/project-list/components/project-list-lumiere.tsx
@@ -32,6 +32,7 @@ import OwnerCell from './table/cells/owner-cell'
 import LastUpdatedCell from './table/cells/last-updated-cell'
 import ActionsCell from './table/cells/actions-cell'
 import InlineTags from './table/cells/inline-tags'
+import WelcomePageContent from './welcome-page-content'
 
 // ── Tile zoom ─────────────────────────────────────────────────────────────────
 
@@ -227,6 +228,7 @@ export function ProjectListLumiere() {
   const {
     error,
     visibleProjects,
+    totalProjectsCount,
     searchText,
     setSearchText,
     filter,
@@ -344,7 +346,9 @@ export function ProjectListLumiere() {
                   </button>
                 </div>
               )}
-              {visibleProjects.length === 0 ? (
+              {totalProjectsCount === 0 ? (
+                <WelcomePageContent />
+              ) : visibleProjects.length === 0 ? (
                 <p className="lumiere-empty">{t('no_projects')}</p>
               ) : (
                 <div
diff --git a/services/web/frontend/js/features/project-list/components/project-list-root.tsx b/services/web/frontend/js/features/project-list/components/project-list-root.tsx
index 12bdd1d8a4..0050d38392 100644
--- a/services/web/frontend/js/features/project-list/components/project-list-root.tsx
+++ b/services/web/frontend/js/features/project-list/components/project-list-root.tsx
@@ -100,6 +100,14 @@ function ProjectListPageContent() {
     return loadingComponent
   }
 
+  if (overallTheme === 'lumiere-') {
+    return (
+      <DsNavStyleProvider>
+        <ProjectListLumiere />
+      </DsNavStyleProvider>
+    )
+  }
+
   if (totalProjectsCount === 0) {
     return (
       <>
@@ -111,14 +119,6 @@ function ProjectListPageContent() {
     )
   }
 
-  if (overallTheme === 'lumiere-') {
-    return (
-      <DsNavStyleProvider>
-        <ProjectListLumiere />
-      </DsNavStyleProvider>
-    )
-  }
-
   return (
     <DsNavStyleProvider>
       <ProjectListDsNav />
diff --git a/services/web/frontend/stylesheets/pages/error-pages.scss b/services/web/frontend/stylesheets/pages/error-pages.scss
index ac21364f9d..76f93c6868 100644
--- a/services/web/frontend/stylesheets/pages/error-pages.scss
+++ b/services/web/frontend/stylesheets/pages/error-pages.scss
@@ -1,3 +1,39 @@
+// Lumière-themed overrides for 404 / error pages.
+// $lum-* vars are declared in project-list-lumiere.scss which is imported
+// earlier in all.scss, so they are available here.
+[data-lumiere='true'] {
+  .error-container {
+    min-height: 60vh;
+    justify-content: center;
+  }
+
+  .error-details {
+    background: rgba(255, 255, 255, 0.88);
+    border-radius: 16px;
+    padding: 3rem;
+    box-shadow: 0 4px 24px rgba(42, 157, 143, 0.12);
+  }
+
+  .error-status {
+    color: #2a9d8f;
+  }
+
+  .error-description {
+    color: #64748b;
+  }
+
+  .error-btn {
+    background: #2a9d8f !important;
+    border-color: #2a9d8f !important;
+    border-radius: 8px;
+
+    &:hover {
+      background: #21867a !important;
+      border-color: #21867a !important;
+    }
+  }
+}
+
 .error-container {
   display: flex;
   align-items: center;
diff --git a/services/web/frontend/stylesheets/pages/project-list-lumiere.scss b/services/web/frontend/stylesheets/pages/project-list-lumiere.scss
index 783752380c..7a07804b32 100644
--- a/services/web/frontend/stylesheets/pages/project-list-lumiere.scss
+++ b/services/web/frontend/stylesheets/pages/project-list-lumiere.scss
@@ -746,7 +746,7 @@ $lum-noise: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' wi
   .lumiere-compact-row {
     display: grid;
     // checkbox | name+tags | format | owner | date | actions
-    grid-template-columns: 28px 1fr 70px 130px 160px auto;
+    grid-template-columns: 28px 1fr 96px 120px 150px auto;
     align-items: center;
     column-gap: 0.85rem;
     padding: 0.45rem 0.75rem;
@@ -987,3 +987,33 @@ $lum-noise: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' wi
   --link-hover-color: #{$lum-teal};
   --link-visited-color: #64748b;
 }
+
+// ── Global Lumière rules (apply to every page when data-lumiere is set) ────
+// These cover pages that don't carry .project-list-lumiere (404, welcome).
+
+[data-lumiere='true'] {
+  background: linear-gradient(160deg, #f0faf8 0%, #e4f4f1 50%, #daeef5 100%);
+  min-height: 100vh;
+
+  // Shared white navbar with teal accent stripe (marketing pages + welcome)
+  .navbar-default {
+    background-color: #ffffff !important;
+    border-bottom: none !important;
+    box-shadow: 0 1px 0 rgba(0, 0, 0, 0.06), 0 2px 8px rgba(0, 0, 0, 0.04);
+    position: relative;
+
+    &::before {
+      content: '';
+      position: absolute;
+      top: 0;
+      left: 0;
+      right: 0;
+      height: 3px;
+      background: linear-gradient(90deg, $lum-teal 0%, $lum-blue 100%);
+    }
+
+    .navbar-brand { color: $lum-text !important; }
+    .navbar-nav > li > a { color: $lum-text-sub !important; }
+    .navbar-nav > li > a:hover { color: $lum-teal !important; }
+  }
+}