diff --git a/frontend/src/App.vue b/frontend/src/App.vue
index 480e7a2..34b51a1 100644
--- a/frontend/src/App.vue
+++ b/frontend/src/App.vue
@@ -1,6 +1,6 @@
 <script setup>
 import { ref, computed, watch, onMounted, nextTick } from 'vue'
-import { fetchGuides, fetchTopics, createTopic as apiCreateTopic, deleteTopic as apiDeleteTopic, createGuide as apiCreate, deleteGuide, cancelGuide as apiCancel, fetchBausteineStatus, fetchActiveBausteine, createBausteine as apiCreateBausteine, cancelBausteine as apiCancelBausteine, deleteBausteine as apiDeleteBausteine, fetchProjects, deleteProject as apiDeleteProject, fetchProviders, fetchStats, fetchTopicFortschritt } from './api.js'
+import { fetchGuides, fetchTopics, createTopic as apiCreateTopic, deleteTopic as apiDeleteTopic, createGuide as apiCreate, deleteGuide, cancelGuide as apiCancel, fetchBausteineStatus, fetchActiveBausteine, createBausteine as apiCreateBausteine, cancelBausteine as apiCancelBausteine, deleteBausteine as apiDeleteBausteine, fetchProjects, deleteProject as apiDeleteProject, fetchProviders, fetchStats, fetchTopicFortschritt, fetchGuideLocks } from './api.js'
 import { usePolling } from './composables/usePolling.js'
 import TopicSidebar from './components/TopicSidebar.vue'
 import TopicDetail from './components/TopicDetail.vue'
@@ -26,6 +26,8 @@ const provider = ref(localStorage.getItem('provider') || 'claude')
 const providers = ref([])
 const stats = ref(null)
 const fortschritt = ref({})
+const locks = ref({})       // Sperr-Gründe pro Format (Backend = einzige Regel-Quelle)
+const uiError = ref(null)   // abgewiesene Aktionen (409/400) sichtbar machen
 const elementsOpen = ref(false)      // rechte Sidebar
 const elementsView = ref(false)      // Übersicht im Hauptbereich
 const elementsVersion = ref(0)       // Erhöhung = Übersicht neu laden
@@ -126,21 +128,27 @@ async function loadTopics() {
   }
 }
 
-// Fehlermeldungen verhalten sich wie Flash-Messages: × blendet aus,
-// beim Reload sind Alt-Fehler von vornherein ausgeblendet.
-const dismissedErrors = ref(new Set())
-let errorsInitialized = false
+// Weggeklickte Fehler bleiben weggeklickt — auch über Reloads (localStorage).
+// Nicht weggeklickte Fehler bleiben sichtbar, bis der Nutzer sie schließt.
+const dismissedErrors = ref(new Set(JSON.parse(localStorage.getItem('dismissedErrors') || '[]')))
+
+function persistDismissed() {
+  localStorage.setItem('dismissedErrors', JSON.stringify([...dismissedErrors.value]))
+}
 
 function handleDismissError(guideId) {
   dismissedErrors.value = new Set([...dismissedErrors.value, guideId])
+  persistDismissed()
 }
 
 async function loadGuides() {
   try {
     guides.value = await fetchGuides()
-    if (!errorsInitialized) {
-      errorsInitialized = true
-      dismissedErrors.value = new Set(guides.value.filter((g) => g.status === 'error').map((g) => g.id))
+    // IDs prunen, deren Guide nicht mehr als Fehler existiert
+    const errorIds = new Set(guides.value.filter((g) => g.status === 'error').map((g) => g.id))
+    if ([...dismissedErrors.value].some((id) => !errorIds.has(id))) {
+      dismissedErrors.value = new Set([...dismissedErrors.value].filter((id) => errorIds.has(id)))
+      persistDismissed()
     }
     loadStats()
   } catch (e) {
@@ -154,9 +162,11 @@ async function loadBausteine() {
     if (selectedTopic.value) {
       bausteine.value = await fetchBausteineStatus(selectedTopic.value)
       fortschritt.value = await fetchTopicFortschritt(selectedTopic.value)
+      locks.value = await fetchGuideLocks(selectedTopic.value)
     } else {
       bausteine.value = { ...EMPTY_BAUSTEINE }
       fortschritt.value = {}
+      locks.value = {}
     }
     if (activeBausteine.value.length && !polling.running()) startPolling()
   } catch (e) {
@@ -224,7 +234,13 @@ async function handleResetBausteine() {
 
 async function handleBausteineClick({ instructions }) {
   if (!selectedTopic.value) return
-  await apiCreateBausteine(selectedTopic.value, instructions, provider.value)
+  uiError.value = null
+  try {
+    await apiCreateBausteine(selectedTopic.value, instructions, provider.value)
+  } catch (e) {
+    uiError.value = e.message
+    return
+  }
   await loadBausteine()
   startPolling()
 }
@@ -237,7 +253,13 @@ async function handleFormatClick({ format, instructions }) {
       && (g.status === 'generating' || g.status === 'queued'),
   )
   if (running) return
-  await apiCreate(selectedTopic.value, format, instructions, provider.value)
+  uiError.value = null
+  try {
+    await apiCreate(selectedTopic.value, format, instructions, provider.value)
+  } catch (e) {
+    uiError.value = e.message
+    return
+  }
   await loadGuides()
   startPolling()
 }
@@ -327,6 +349,8 @@ onMounted(async () => {
       :selectedTopic="selectedTopic"
       :stats="stats"
       :fortschritt="fortschritt"
+      :locks="locks"
+      :uiError="uiError"
       :doneByFormat="doneByFormat"
       :latestByFormat="latestByFormat"
       :allGuides="guides"
@@ -350,6 +374,7 @@ onMounted(async () => {
       @cancelGuide="handleCancel"
       @deleteGuide="handleDeleteGuide"
       @dismissError="handleDismissError"
+      @dismissUiError="uiError = null"
       @preview="handlePreview"
       @openElements="handleOpenElements"
       @togglePin="toggleSidebarPin"
diff --git a/frontend/src/api.js b/frontend/src/api.js
index 1d4d7b6..bd05e41 100644
--- a/frontend/src/api.js
+++ b/frontend/src/api.js
@@ -1,17 +1,35 @@
 const BASE = '/api'
 
+// Backend-Fehler (400/409 mit detail) als Error werfen statt sie zu verschlucken
+async function jsonOrThrow(res) {
+  if (!res.ok) {
+    let detail = `Fehler (HTTP ${res.status})`
+    try {
+      const data = await res.json()
+      if (data.detail) detail = typeof data.detail === 'string' ? data.detail : JSON.stringify(data.detail)
+    } catch { /* kein JSON-Body */ }
+    throw new Error(detail)
+  }
+  return res.json()
+}
+
 export async function fetchGuides() {
   const res = await fetch(`${BASE}/guides`)
   return res.json()
 }
 
+export async function fetchGuideLocks(topic) {
+  const res = await fetch(`${BASE}/guides/locks?topic=${encodeURIComponent(topic)}`)
+  return res.json()
+}
+
 export async function createGuide(topic, format, instructions = '', provider = 'claude') {
   const res = await fetch(`${BASE}/guides`, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ topic, format, instructions, provider }),
   })
-  return res.json()
+  return jsonOrThrow(res)
 }
 
 export async function fetchActiveBausteine() {
@@ -30,7 +48,7 @@ export async function createBausteine(topic, instructions = '', provider = 'clau
     headers: { 'Content-Type': 'application/json' },
     body: JSON.stringify({ topic, instructions, provider }),
   })
-  return res.json()
+  return jsonOrThrow(res)
 }
 
 export async function cancelBausteine(topic) {
diff --git a/frontend/src/components/TopicDetail.vue b/frontend/src/components/TopicDetail.vue
index be4abfe..639e13d 100644
--- a/frontend/src/components/TopicDetail.vue
+++ b/frontend/src/components/TopicDetail.vue
@@ -95,6 +95,12 @@ function closeChat() {
   chat.reset()
 }
 
+// Mobil schließen sich Chat und Elemente-Sidebar gegenseitig aus —
+// nebeneinander ist kein Platz, die Sidebar würde den Chat überdecken.
+watch(() => props.elementsOpen, (open) => {
+  if (open && chatOpen.value && window.matchMedia('(max-width: 768px)').matches) closeChat()
+})
+
 function onDocMouseDown(e) {
   if (!chatOpen.value) return
   if (panelEl.value && panelEl.value.contains(e.target)) return
@@ -540,6 +546,14 @@ function extractContext() {
   right: calc(1.5rem + 320px);
 }
 
+/* Mobil liegt die Elemente-Sidebar als Overlay über dem Chat — FAB/Panel ausblenden */
+@media (max-width: 768px) {
+  .chat-fab.shifted,
+  .chat-panel.shifted {
+    display: none;
+  }
+}
+
 .chat-panel {
   position: fixed;
   right: 1.5rem;
diff --git a/frontend/src/components/TopicSidebar.vue b/frontend/src/components/TopicSidebar.vue
index 0184a31..096992e 100644
--- a/frontend/src/components/TopicSidebar.vue
+++ b/frontend/src/components/TopicSidebar.vue
@@ -8,6 +8,8 @@ const props = defineProps({
   selectedTopic: { type: String, default: null },
   stats: { type: Object, default: null },
   fortschritt: { type: Object, default: () => ({}) },
+  locks: { type: Object, default: () => ({}) },
+  uiError: { type: String, default: null },
   doneByFormat: { type: Object, default: () => ({}) },
   latestByFormat: { type: Object, default: () => ({}) },
   allGuides: { type: Array, default: () => [] },
@@ -20,7 +22,7 @@ const props = defineProps({
   providers: { type: Array, default: () => [] },
 })
 
-const emit = defineEmits(['select', 'create', 'formatClick', 'bausteineClick', 'cancelBausteine', 'resetBausteine', 'deleteTopic', 'deleteProject', 'cancelGuide', 'deleteGuide', 'dismissError', 'preview', 'openElements', 'togglePin', 'sidebarLeave', 'toggleDark', 'setProvider'])
+const emit = defineEmits(['select', 'create', 'formatClick', 'bausteineClick', 'cancelBausteine', 'resetBausteine', 'deleteTopic', 'deleteProject', 'cancelGuide', 'deleteGuide', 'dismissError', 'dismissUiError', 'preview', 'openElements', 'togglePin', 'sidebarLeave', 'toggleDark', 'setProvider'])
 
 function providerAvailable(id) {
   const p = props.providers.find((x) => x.id === id)
@@ -54,12 +56,13 @@ const bausteineState = computed(() => {
   return props.bausteine.ready ? 'done' : 'none'
 })
 
+// Nur FREMDE Themen — das gewählte Thema zeigt seinen Fortschritt inline an der Zeile
 const activeGenerations = computed(() => {
-  const bausteinLines = props.activeBausteine.map(
-    (b) => `${b.topic} – Bausteine: ${b.progress || 'Wartend…'}`,
-  )
+  const bausteinLines = props.activeBausteine
+    .filter((b) => b.topic !== props.selectedTopic)
+    .map((b) => `${b.topic} – Bausteine: ${b.progress || 'Wartend…'}`)
   const guideLines = props.allGuides
-    .filter((g) => g.status === 'generating' || g.status === 'queued')
+    .filter((g) => (g.status === 'generating' || g.status === 'queued') && g.topic !== props.selectedTopic)
     .map((g) => `${g.topic} – ${g.format}: ${g.progress || 'Wartend…'}`)
   return [...bausteinLines, ...guideLines]
 })
@@ -118,6 +121,7 @@ function guideSteps(format) {
 function errorMsg(format) {
   const latest = props.latestByFormat[format]
   if (latest?.status !== 'error' || props.dismissedErrors.has(latest.id)) return ''
+  if (abgebrochen(format)) return '' // kein roter Fehler — das Pausiert-Badge zeigt den Zustand
   return latest.error_msg || 'Fehler bei der Generierung'
 }
 
@@ -134,28 +138,11 @@ function handleFormatClick(format) {
   }
 }
 
-// Lernschulden-Regeln (nur Neu-Erstellungen; Resume + Neu-Generieren bestehender erlaubt):
-// Progression pro Thema (MiniGuide → Guide → FullGuide) + max. 3 offene je Format.
-const VORSTUFE = { Guide: 'MiniGuide', FullGuide: 'Guide' }
-
-function offeneGuides(format) {
-  const f = props.stats?.formate?.[format]
-  return (f?.erstellt ?? 0) - (f?.absolviert ?? 0)
-}
-
+// Sperr-Gründe kommen vom Backend (GET /guides/locks) — die Regeln existieren
+// nur noch dort. Solange locks noch nicht geladen sind: Button frei, das
+// Backend weist ungültige Starts ohnehin ab (sichtbar über uiError).
 function playLock(format) {
-  if (format === 'OnePager') return null
-  if (!props.bausteine.ready) return 'Erst Bausteine erstellen'
-  if (props.doneByFormat[format] || abgebrochen(format)) return null
-  const vorstufe = VORSTUFE[format]
-  if (vorstufe && !props.fortschritt?.[vorstufe]) {
-    return `Erst den ${vorstufe} dieses Themas absolvieren`
-  }
-  const offen = offeneGuides(format)
-  if (offen >= 3) {
-    return `Erst ${format}s absolvieren — ${offen} offen (max. 3)`
-  }
-  return null
+  return props.locks?.[format] ?? null
 }
 
 function handlePlay(format) {
@@ -240,12 +227,21 @@ function confirmDeleteProject(name) {
       >{{ PROVIDER_LABELS[p.id] || p.id }}</button>
     </div>
     <div class="format-section" v-if="selectedTopic">
+      <div class="format-error ui-error" v-if="uiError">
+        <span class="format-error-text">{{ uiError }}</span>
+        <button class="format-error-x" title="Ausblenden" @click="emit('dismissUiError')">×</button>
+      </div>
       <div class="progress-info" v-if="activeGenerations.length">
         <div v-for="(line, i) in activeGenerations" :key="i">{{ line }}</div>
       </div>
       <div class="format-row bausteine-row ord-bausteine">
         <div class="format-name bausteine-name">
           <span class="format-label">Bausteine</span>
+          <span
+            v-if="bausteine.partial && bausteineState !== 'generating'"
+            class="resume-badge"
+            title="Abgebrochen — ▶ setzt fort"
+          >Pausiert</span>
           <span class="step-dots">
             <span
               v-for="s in (bausteine.steps || [])"
@@ -280,7 +276,10 @@ function confirmDeleteProject(name) {
           </template>
         </div>
       </div>
-      <div v-if="bausteine.error" class="format-error ord-bausteine">
+      <div v-if="bausteineState === 'generating'" class="format-progress ord-bausteine">
+        {{ bausteine.progress || 'Wartend…' }}
+      </div>
+      <div v-if="bausteine.error && !bausteine.error.startsWith('Abgebrochen')" class="format-error ord-bausteine">
         <span class="format-error-text">{{ bausteine.error }}</span>
       </div>
 <!-- OnePager (unabhängig von Bausteinen) steht per CSS-order vor der Bausteine-Zeile -->
@@ -288,6 +287,11 @@ function confirmDeleteProject(name) {
         <div :class="['format-row', 'fmt-' + guideStatus(f.key)]">
           <button class="format-name" @click="handleFormatClick(f.key)">
             <span class="format-label">{{ f.label }}</span>
+            <span
+              v-if="abgebrochen(f.key)"
+              class="resume-badge"
+              title="Abgebrochen — ▶ setzt fort"
+            >Pausiert</span>
             <span class="step-dots" v-if="guideSteps(f.key).length">
               <span
                 v-for="s in guideSteps(f.key)"
@@ -316,6 +320,10 @@ function confirmDeleteProject(name) {
             </template>
           </div>
         </div>
+        <div
+          v-if="guideStatus(f.key) === 'generating' || guideStatus(f.key) === 'queued'"
+          class="format-progress"
+        >{{ latestByFormat[f.key]?.progress || 'Wartend…' }}</div>
         <div v-if="errorMsg(f.key)" class="format-error">
           <span class="format-error-text">{{ errorMsg(f.key) }}</span>
           <button class="format-error-x" title="Ausblenden" @click="dismissError(f.key)">×</button>
@@ -653,6 +661,35 @@ function confirmDeleteProject(name) {
   animation: pulse 1.5s ease-in-out infinite;
 }
 
+/* Abgewiesene Aktion (409/400) — oberhalb aller Format-Zeilen */
+.ui-error {
+  order: 0;
+  padding: 0.4rem 0.75rem;
+  background: var(--warning-soft);
+}
+
+/* Fortschritts-Text direkt unter der laufenden Format-Zeile */
+.format-progress {
+  padding: 0 0.75rem 5px calc(0.75rem + 8px);
+  font-size: 0.72rem;
+  color: var(--warning);
+  line-height: 1.3;
+  animation: pulse 1.5s ease-in-out infinite;
+}
+
+.resume-badge {
+  flex: 0 0 auto;
+  font-size: 0.6rem;
+  font-weight: 700;
+  text-transform: uppercase;
+  letter-spacing: 0.03em;
+  color: var(--warning);
+  background: var(--warning-soft);
+  border: 1px solid var(--warning-border);
+  border-radius: 4px;
+  padding: 1px 5px;
+}
+
 .format-row {
   display: flex;
   align-items: center;