diff --git a/index.css b/index.css
index a96a84e..ff712ff 100644
--- a/index.css
+++ b/index.css
@@ -11,8 +11,12 @@
   --safe-bottom: 0px;
   --safe-left: 0px;
   --safe-right: 0px;
-  /* Height actually consumed by the fixed header, safe-area included. */
-  --header-offset: calc(var(--header-h) + var(--safe-top));
+  /* Height actually consumed by the fixed header, safe-area included.
+     `--header-measured` is published at runtime by HeaderComponent via a
+     ResizeObserver: the header grows when the mobile search sheet opens, when
+     an iOS safe area applies, or at high zoom, and a hardcoded value would let
+     the sticky themes bar slide under it (it was fully hidden in that case). */
+  --header-offset: var(--header-measured, calc(var(--header-h) + var(--safe-top)));
   /* Usable viewport height that follows the mobile browser chrome. */
   --app-vh: 100vh;
 }
@@ -181,18 +185,27 @@ body {
 }
 .app-avatar-btn:hover { background-color: var(--panel-2); }
 
+/* Circular user badge ("pastille"). Belt and braces: `rounded-full` from the
+   markup plus these rules, so the badge can never degrade into a rectangle if
+   a theme stylesheet overrides the radius. */
 .avatar-circle {
   display: inline-flex;
   align-items: center;
   justify-content: center;
+  flex-shrink: 0;
   width: 2rem;
   height: 2rem;
-  border-radius: 9999px;
-  border-width: 1px;
+  min-width: 2rem;
+  min-height: 2rem;
+  aspect-ratio: 1 / 1;
+  border-radius: 9999px !important;
+  border-width: 2px;
   border-style: solid;
   font-size: 0.875rem;
   font-weight: 600;
-  flex-shrink: 0;
+  line-height: 1;
+  overflow: hidden;
+  text-transform: uppercase;
 }
 
 /* The fixed app header: honours the safe area and never overflows. */
diff --git a/src/components/header/header.component.html b/src/components/header/header.component.html
index 0e5ddc0..2f8488b 100644
--- a/src/components/header/header.component.html
+++ b/src/components/header/header.component.html
@@ -1,9 +1,17 @@
 
-<header class="app-header bg-slate-800/50 backdrop-blur-sm fixed inset-x-0 top-0 z-50 shadow-lg border-b border-slate-700/60"
+<header class="app-header fixed inset-x-0 top-0 z-50 shadow-lg border-b border-slate-700/60"
         [style.paddingTop]="'var(--safe-top)'"
         [style.paddingLeft]="'var(--safe-left)'"
         [style.paddingRight]="'var(--safe-right)'">
 
+  <!-- Frosted layer lives on its own child, never on <header> itself.
+       `backdrop-filter` makes an element the containing block for
+       position:fixed descendants, so blurring the header trapped the
+       provider-picker and Ctrl+K modals inside the 64px header box (their top
+       was unreachable). The overlays below are siblings of this layer, so
+       they resolve against the viewport again. -->
+  <div aria-hidden="true" class="pointer-events-none absolute inset-0 -z-10 bg-slate-800/50 backdrop-blur-sm"></div>
+
   <!-- Top row: burger + logo (always) / search (desktop) / actions -->
   <div class="flex items-center gap-1 h-14 md:h-16 px-2 md:px-4">
 
@@ -93,7 +101,7 @@
           <div class="relative" #userMenuContainer>
             <button type="button" (click)="toggleUserMenu()" class="app-avatar-btn focus-ring" aria-haspopup="true"
                     [attr.aria-expanded]="userMenuOpen()" [attr.aria-label]="user()?.username || user()?.email || ('menu.account' | t)">
-              <span class="avatar-circle" [ngClass]="avatarClasses()">{{ avatarLetter() }}</span>
+              <span class="avatar-circle rounded-full" [ngClass]="avatarClasses()">{{ avatarLetter() }}</span>
             </button>
             @if (userMenuOpen()) {
               <div class="absolute right-0 mt-2 w-[min(20rem,calc(100vw-1rem))] overflow-hidden rounded-xl border border-slate-700 bg-slate-900 shadow-xl z-50" role="menu">
@@ -120,7 +128,7 @@
   <!-- Mobile search sheet: the same <app-search-box> instance is rendered here
        through CSS only when the user asks for it. Kept out of the flow so the
        page never reflows while typing. -->
-  <div id="mobile-search-sheet" class="md:hidden border-t border-slate-700/60 bg-slate-900/95 backdrop-blur-sm px-2 pb-2"
+  <div id="mobile-search-sheet" class="md:hidden border-t border-slate-700/60 bg-slate-900/95 px-2 pb-2"
        [class.hidden]="!mobileSearchOpen()">
     <div class="relative">
       <app-search-box [placeholder]="('search.placeholder' | t)"
@@ -183,7 +191,7 @@
     @if (user()) {
       <div class="border-t border-slate-800 px-4 py-3">
         <div class="mb-2 flex items-center gap-3">
-          <span class="avatar-circle" [ngClass]="avatarClasses()">{{ avatarLetter() }}</span>
+          <span class="avatar-circle rounded-full" [ngClass]="avatarClasses()">{{ avatarLetter() }}</span>
           <span class="min-w-0 flex-1">
             <span class="block truncate text-sm font-semibold text-slate-100">{{ user()?.username || user()?.email }}</span>
             <span class="block truncate text-xs text-slate-400">{{ user()?.email }}</span>
diff --git a/src/components/header/header.component.ts b/src/components/header/header.component.ts
index 17aefc8..360b28d 100644
--- a/src/components/header/header.component.ts
+++ b/src/components/header/header.component.ts
@@ -1,4 +1,4 @@
-import { ChangeDetectionStrategy, Component, computed, inject, signal, Input, Output, EventEmitter, HostListener, ViewChild, ViewChildren, QueryList, ElementRef } from '@angular/core';
+import { ChangeDetectionStrategy, Component, computed, inject, signal, Input, Output, EventEmitter, HostListener, ViewChild, ViewChildren, QueryList, ElementRef, DestroyRef, AfterViewInit } from '@angular/core';
 import { CommonModule } from '@angular/common';
 import { Router, RouterLink, NavigationEnd } from '@angular/router';
 import { InstanceService, Provider } from '../../services/instance.service';
@@ -26,7 +26,7 @@ import { SearchBoxComponent } from '../search/search-box.component';
     SearchBoxComponent
   ]
 })
-export class HeaderComponent {
+export class HeaderComponent implements AfterViewInit {
   private router = inject(Router);
   instances = inject(InstanceService);
   private auth = inject(AuthService);
@@ -39,6 +39,40 @@ export class HeaderComponent {
   // Two <app-search-box> instances exist (desktop slot + mobile sheet); only one
   // is ever visible, so focus must target the visible one.
   @ViewChildren(SearchBoxComponent) searchBoxes!: QueryList<SearchBoxComponent>;
+  private readonly host = inject(ElementRef);
+  private readonly destroyRef = inject(DestroyRef);
+
+  /**
+   * Publishes the header's real height as `--header-measured` so every sticky
+   * element that sits below it (themes bar, channel tabs) is offset exactly.
+   * A hardcoded `--header-h` is only a pre-measurement fallback: the header
+   * grows by ~60px when the mobile search sheet opens, which used to push the
+   * themes bar entirely under the header.
+   */
+  private syncHeaderOffset() {
+    try {
+      const el = this.host.nativeElement.querySelector('header.app-header') as HTMLElement | null;
+      if (!el) return;
+      const h = Math.ceil(el.getBoundingClientRect().height);
+      if (!h) return;
+      const root = document.documentElement.style;
+      if (root.getPropertyValue('--header-measured') !== `${h}px`) {
+        root.setProperty('--header-measured', `${h}px`);
+      }
+    } catch {}
+  }
+
+  ngAfterViewInit() {
+    try {
+      const el = this.host.nativeElement.querySelector('header.app-header') as HTMLElement | null;
+      if (el && typeof ResizeObserver !== 'undefined') {
+        const ro = new ResizeObserver(() => this.syncHeaderOffset());
+        ro.observe(el);
+        this.destroyRef.onDestroy(() => ro.disconnect());
+      }
+    } catch {}
+    this.syncHeaderOffset();
+  }
 
   /** Reflects the mobile drawer state so the burger exposes `aria-expanded`. */
   @Input() drawerOpen = false;
diff --git a/src/components/themes/themes-nav.component.html b/src/components/themes/themes-nav.component.html
index dad36dd..6a421a0 100644
--- a/src/components/themes/themes-nav.component.html
+++ b/src/components/themes/themes-nav.component.html
@@ -47,16 +47,18 @@
   </button>
 
   <!-- Replier la bande : action disponible uniquement dans le header.
-       On phones the rail is edge-to-edge with a swipe affordance instead of
-       the reserved arrow gutters. -->
+       On phones the rail is edge-to-edge and shows icons only — the labels do
+       not fit and force the strip to scroll for the first few themes. -->
   <div class="scroll-rail no-scrollbar md:overflow-x-auto" #scroll (wheel)="onWheel($event)">
-    <ul role="tablist" aria-label="Themes" class="flex min-w-max items-center gap-2 px-3 py-2 md:px-12">
+    <ul role="tablist" aria-label="Themes" class="flex min-w-max items-center gap-1.5 px-3 py-2 sm:gap-2 md:px-12">
       <li *ngFor="let t of displayedThemes(); let i = index" class="shrink-0">
         <button
           #pill
           role="tab"
           type="button"
-          class="chip px-3 py-1.5 rounded-full text-sm font-medium border transition-colors whitespace-nowrap focus:outline-none focus:ring-2 focus:ring-red-500"
+          [attr.aria-label]="themesSvc.i18nLabel(t)"
+          [attr.title]="themesSvc.i18nLabel(t)"
+          class="chip inline-flex items-center justify-center gap-1.5 rounded-full border px-3 py-1.5 text-sm font-medium transition-colors whitespace-nowrap focus:outline-none focus:ring-2 focus:ring-red-500 md:px-3.5"
           [class.bg-slate-100/10]="activeSlug() === t.slug"
           [class.text-white]="activeSlug() === t.slug"
           [class.border-red-500]="activeSlug() === t.slug"
@@ -66,8 +68,8 @@
           (click)="goToTheme(t.slug)"
           (keydown)="onKeydown($event, i)"
         >
-          <span class="mr-1 select-none">{{ t.emoji }}</span>
-          <span>{{ themesSvc.i18nLabel(t) }}</span>
+          <span class="select-none text-base leading-none md:text-base">{{ t.emoji }}</span>
+          <span class="hidden md:inline">{{ themesSvc.i18nLabel(t) }}</span>
         </button>
       </li>
     </ul>