feat(robustheit): optimistische Nebenläufigkeit (featuresVersion + Konflikt-Erkennung)

Verhindert stilles Überschreiben neuerer Änderungen durch veralteten Stand
(z.B. nach Offline-Reconnect oder Lock-Ablauf bei Multi-Device).

- Project.featuresVersion (Schema + Auto-Migration), pro Features-Speichern +1
- Features-PUT: optimistischer Lock in interaktiver Transaktion
  (updateMany WHERE featuresVersion=baseVersion -> atomar; count=0 => 409 Konflikt)
- Bei Konflikt liefert der Server den aktuellen Stand zurück (409 + features + version)
- Client sendet baseVersion (Auto-Save, manuell, Beacon, Offline-Queue), übernimmt
  bei 409 den Server-Stand und warnt den Nutzer (statt still zu überschreiben)
- Offline-Queue verwirft konfligierende 4xx (kein Clobber beim Reconnect)
- Transaktions-Timeout 15s für grosse Zeichnungen auf langsamer DB

Version 1.4.11

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ROADMAP.md

@@ -52,6 +52,17 @@ Legende Aufwand: 🟢 klein · 🟡 mittel · 🔴 gross
   - Live-Sync für Journal existierte bereits (Socket → journal-refresh).
   - _Offen (Kür): echtes gleichzeitiges Zeichnen (Co-Drawing) — bewusst nicht gebaut._
 
+## Zusatz – Robustheit / Datensicherheit ✅
+
+- [x] Features-Speichern atomar (`prisma.$transaction`) — kein Totalverlust-Fenster mehr
+- [x] localStorage-Features pro Projekt (`lageplan-features-<id>`) statt globalem Key
+- [x] Sync-Queue verwirft dauerhafte 4xx-Fehler (kein Endlos-Retry/verstopfte Queue)
+- [x] `beforeunload` persistiert auch leere Listen (gelöschte Elemente gehen nicht verloren)
+- [x] **5: Optimistische Nebenläufigkeit** — `Project.featuresVersion` + Versions-Check
+  beim Speichern. Ein veralteter (z.B. offline) Stand überschreibt neuere Änderungen nicht
+  mehr still, sondern erzeugt 409 → Client übernimmt Server-Stand + Warnung. Offline-Queue
+  verwirft konfliktierende 4xx. (Merge pro Element / echtes Co-Drawing weiterhin offen.)
+
 ## Zusatz – Leitungsrechner professionalisiert ✅
 
 - [x] Formel zentralisiert in `src/lib/hose-calc.ts` (eine Quelle, typisiert, testbar)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "lageplan",
-  "version": "1.4.9",
+  "version": "1.4.11",
   "description": "Feuerwehr Lageplan - Krokier-App für Einsatzdokumentation",
   "private": true,
   "scripts": {

prisma/migrate.js

@@ -73,6 +73,7 @@ async function migrate() {
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "journalfuehrer" TEXT`,
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "mode" TEXT NOT NULL DEFAULT 'EINSATZ'`,
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "exerciseEvaluation" TEXT`,
+    `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "featuresVersion" INTEGER NOT NULL DEFAULT 0`,
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "editingById" TEXT`,
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "editingUserName" TEXT`,
     `ALTER TABLE projects ADD COLUMN IF NOT EXISTS "editingSessionId" TEXT`,

prisma/schema.prisma

@@ -166,6 +166,10 @@ model Project {
   mapCenter      Json     @default("{\"lng\": 8.5417, \"lat\": 47.3769}")
   mapZoom        Float    @default(15)
   isLocked    Boolean  @default(false)
+  // Optimistische Nebenläufigkeit: wird bei jedem Features-Speichern hochgezählt.
+  // Verhindert, dass ein veralteter (z.B. offline zwischengespeicherter) Stand
+  // neuere Änderungen stillschweigend überschreibt.
+  featuresVersion Int   @default(0)
 
   // Live editing lock (session-based for same-account multi-device)
   editingById       String?

src/app/api/projects/[id]/features/route.ts

@@ -20,12 +20,15 @@ export async function GET(
       return NextResponse.json({ error: 'Projekt nicht gefunden' }, { status: 404 })
     }
 
-    const features = await (prisma as any).feature.findMany({
+    const [features, proj] = await Promise.all([
-      where: { projectId: id },
+      (prisma as any).feature.findMany({
-      orderBy: { createdAt: 'asc' },
+        where: { projectId: id },
-    })
+        orderBy: { createdAt: 'asc' },
+      }),
+      (prisma as any).project.findUnique({ where: { id }, select: { featuresVersion: true } }),
+    ])
 
-    return NextResponse.json({ features })
+    return NextResponse.json({ features, featuresVersion: proj?.featuresVersion ?? 0 })
   } catch (error) {
     console.error('Error fetching features:', error)
     return NextResponse.json({ error: 'Serverfehler' }, { status: 500 })
@@ -113,40 +116,74 @@ export async function PUT(
     }
 
     const body = await request.json()
-    const { features, mapCenter, mapZoom } = body as {
+    const { features, mapCenter, mapZoom, baseVersion } = body as {
       features: Array<{ id?: string; type: string; geometry: object; properties?: object }>
       mapCenter?: { lng: number; lat: number }
       mapZoom?: number
+      baseVersion?: number
     }
 
-    // Persist map viewport alongside features (if provided)
+    try {
-    if (mapCenter && mapZoom !== undefined) {
+      // ATOMAR + optimistischer Lock in EINER interaktiven Transaktion:
-      await (prisma as any).project.update({
+      // - Version prüfen/hochzählen (verhindert Überschreiben durch veralteten Stand)
-        where: { id },
+      // - Features löschen + neu anlegen (kein Totalverlust-Fenster)
-        data: { mapCenter, mapZoom },
+      const result = await (prisma as any).$transaction(async (tx: any) => {
-      })
+        if (typeof baseVersion === 'number') {
+          // Nur speichern, wenn die Version noch stimmt (atomar über WHERE-Bedingung)
+          const bump = await tx.project.updateMany({
+            where: { id, featuresVersion: baseVersion },
+            data: { featuresVersion: { increment: 1 } },
+          })
+          if (bump.count === 0) {
+            const conflict: any = new Error('VERSION_CONFLICT')
+            conflict.code = 'VERSION_CONFLICT'
+            throw conflict
+          }
+        } else {
+          // Kein baseVersion mitgeschickt (Alt-Client/Beacon) → nur hochzählen
+          await tx.project.update({ where: { id }, data: { featuresVersion: { increment: 1 } } })
+        }
+
+        if (mapCenter && mapZoom !== undefined) {
+          await tx.project.update({ where: { id }, data: { mapCenter, mapZoom } })
+        }
+
+        await tx.feature.deleteMany({ where: { projectId: id } })
+        if (features && features.length > 0) {
+          await tx.feature.createMany({
+            data: features.map((f: any) => ({
+              projectId: id,
+              type: f.type,
+              geometry: f.geometry,
+              properties: f.properties || {},
+            })),
+          })
+        }
+
+        const [updatedFeatures, proj] = await Promise.all([
+          tx.feature.findMany({ where: { projectId: id } }),
+          tx.project.findUnique({ where: { id }, select: { featuresVersion: true } }),
+        ])
+        return { features: updatedFeatures, featuresVersion: proj?.featuresVersion ?? 0 }
+      }, { timeout: 15000, maxWait: 5000 })
+
+      return NextResponse.json(result)
+    } catch (txError: any) {
+      if (txError?.code === 'VERSION_CONFLICT') {
+        // Konflikt: aktuellen Server-Stand zurückgeben, damit der Client abgleichen kann
+        const [currentFeatures, proj] = await Promise.all([
+          (prisma as any).feature.findMany({ where: { projectId: id }, orderBy: { createdAt: 'asc' } }),
+          (prisma as any).project.findUnique({ where: { id }, select: { featuresVersion: true } }),
+        ])
+        return NextResponse.json({
+          error: 'Der Einsatz wurde zwischenzeitlich geändert.',
+          conflict: true,
+          features: currentFeatures,
+          featuresVersion: proj?.featuresVersion ?? 0,
+        }, { status: 409 })
+      }
+      throw txError
     }
-
-    await (prisma as any).feature.deleteMany({
-      where: { projectId: id },
-    })
-
-    if (features && features.length > 0) {
-      await (prisma as any).feature.createMany({
-        data: features.map((f: any) => ({
-          projectId: id,
-          type: f.type,
-          geometry: f.geometry,
-          properties: f.properties || {},
-        })),
-      })
-    }
-
-    const updatedFeatures = await (prisma as any).feature.findMany({
-      where: { projectId: id },
-    })
-
-    return NextResponse.json({ features: updatedFeatures })
   } catch (error) {
     console.error('Error updating features:', error)
     return NextResponse.json({ error: 'Serverfehler' }, { status: 500 })

src/app/app/page.tsx

@@ -72,6 +72,9 @@ export default function AppPage() {
   const featuresRef = useRef<DrawFeature[]>(features)
   useEffect(() => { featuresRef.current = features }, [features])
 
+  // Optimistischer Lock: Features-Version des aktuellen Projekts mitführen
+  const featuresVersionRef = useRef<number>(0)
+
   // Ref for undo-draw-point (removes last point during line drawing)
   const undoDrawPointRef = useRef<(() => boolean) | null>(null)
 
@@ -385,6 +388,24 @@ export default function AppPage() {
   const canEdit = canEditMap // Abwärtskompatibel für Karten-bezogene Stellen
   const isReadOnly = !!editingBy && !isEditingByMe
 
+  // Features-Version bei Projektwechsel initialisieren
+  useEffect(() => {
+    featuresVersionRef.current = (currentProject as any)?.featuresVersion ?? 0
+  }, [currentProject?.id])
+
+  // Speicher-Konflikt: Server-Stand übernehmen und den Nutzer warnen
+  const handleSaveConflict = useCallback((serverFeatures: DrawFeature[], serverVersion: number) => {
+    setFeatures(serverFeatures)
+    featuresVersionRef.current = serverVersion
+    undoStackRef.current = []
+    redoStackRef.current = []
+    toast({
+      title: 'Konflikt erkannt',
+      description: 'Der Einsatz wurde von jemand anderem geändert — der aktuelle Stand wurde geladen. Bitte prüfe deine Änderungen und mache sie ggf. erneut.',
+      variant: 'destructive',
+    })
+  }, [toast])
+
   // Auto-save: localStorage persistence + debounced API save + beacon on unload
   useAutoSave({
     currentProject,
@@ -394,6 +415,8 @@ export default function AppPage() {
     socketRef,
     isEditingByMe,
     setSyncQueueCount,
+    featuresVersionRef,
+    onConflict: handleSaveConflict,
   })
 
   // Fullscreen toggle
@@ -437,7 +460,7 @@ export default function AppPage() {
               if (apiFeatures.length > 0) {
                 setFeatures(apiFeatures)
               } else {
-                const savedFeatures = localStorage.getItem('lageplan-features')
+                const savedFeatures = localStorage.getItem(`lageplan-features-${proj.id}`)
                 if (savedFeatures) setFeatures(JSON.parse(savedFeatures))
               }
             })
@@ -445,14 +468,14 @@ export default function AppPage() {
             // Project not accessible (different tenant, deleted, etc.) — clear
             console.log('[Restore] Project not accessible for current user, clearing')
             localStorage.removeItem('lageplan-project')
-            localStorage.removeItem('lageplan-features')
+            localStorage.removeItem(`lageplan-features-${proj.id}`)
             setCurrentProject(null)
             setFeatures([])
           }
         }).catch(() => {
-          // Network error — use cached data as fallback
+          // Network error — use cached data as fallback (nur Features DESSELBEN Projekts)
           setCurrentProject(proj)
-          const savedFeatures = localStorage.getItem('lageplan-features')
+          const savedFeatures = localStorage.getItem(`lageplan-features-${proj.id}`)
           if (savedFeatures) setFeatures(JSON.parse(savedFeatures))
         })
       }
@@ -508,7 +531,7 @@ export default function AppPage() {
       undoStackRef.current = []
       redoStackRef.current = []
       localStorage.removeItem('lageplan-project')
-      localStorage.removeItem('lageplan-features')
+      localStorage.removeItem(`lageplan-features-${deletedId}`)
     }
     addAudit(`Einsatz gelöscht`)
     toast({
@@ -522,7 +545,7 @@ export default function AppPage() {
 
     setIsSaving(true)
     try {
-      const saveBody: any = { features }
+      const saveBody: any = { features, baseVersion: featuresVersionRef.current }
       if (mapRef.current) {
         const c = mapRef.current.getCenter()
         saveBody.mapCenter = { lng: c.lng, lat: c.lat }
@@ -554,19 +577,34 @@ export default function AppPage() {
         }
         const created = await createRes.json()
         setCurrentProject(created.project)
+        featuresVersionRef.current = created.project?.featuresVersion ?? 0
         // Retry save with new project ID
         res = await fetch(`/api/projects/${created.project.id}/features`, {
           method: 'PUT',
           headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({ features }),
+          body: JSON.stringify({ features, baseVersion: featuresVersionRef.current }),
         })
       }
 
+      // Versionskonflikt: Server-Stand übernehmen statt zu überschreiben
+      if (res.status === 409) {
+        const data = await res.json().catch(() => null)
+        if (data?.conflict) {
+          handleSaveConflict(data.features || [], data.featuresVersion ?? featuresVersionRef.current)
+          return
+        }
+      }
+
       if (!res.ok) {
         const err = await res.json().catch(() => ({}))
         throw new Error(err.error || 'Speichern fehlgeschlagen')
       }
 
+      const okData = await res.json().catch(() => null)
+      if (okData && typeof okData.featuresVersion === 'number') {
+        featuresVersionRef.current = okData.featuresVersion
+      }
+
       // Broadcast features to other clients
       socketRef.current?.emit('features-updated', {
         projectId: currentProject.id,
@@ -588,6 +626,22 @@ export default function AppPage() {
     }
   }
 
+  // Einsatz beenden: speichern, Bearbeitungs-Lock lösen und zurück zur Übersicht.
+  const handleEndProject = async () => {
+    if (!currentProject) return
+    if (!confirm(`Einsatz "${currentProject.title}" beenden? Alle Änderungen werden gespeichert und der Einsatz geschlossen.`)) return
+    const title = currentProject.title
+    try { await handleSaveProject() } catch { /* Save meldet Fehler selbst */ }
+    if (isEditingByMe) { try { await handleStopEditing() } catch { /* ignore */ } }
+    addAudit(`Einsatz "${title}" beendet`)
+    setCurrentProject(null)
+    setFeatures([])
+    undoStackRef.current = []
+    redoStackRef.current = []
+    localStorage.removeItem('lageplan-project')
+    toast({ title: 'Einsatz beendet', description: 'Gespeichert und geschlossen.' })
+  }
+
   const handleFeaturesChange = useCallback((newFeatures: DrawFeature[]) => {
     undoStackRef.current.push(featuresRef.current)
     redoStackRef.current = []
@@ -798,6 +852,7 @@ export default function AppPage() {
         <Topbar
           project={currentProject}
           onNewProject={handleNewProject}
+          onEndProject={handleEndProject}
           onSaveProject={handleSaveProject}
           onLoadProject={handleProjectLoaded}
           onDeleteProject={handleDeleteProject}

src/components/layout/topbar.tsx

@@ -42,6 +42,7 @@ import {
   HelpCircle,
   Lock,
   Unlock,
+  CheckCircle2,
 } from 'lucide-react'
 import { HoseSettingsDialog } from '@/components/dialogs/hose-settings-dialog'
 import type { Project, DrawFeature, ProjectMode } from '@/types'
@@ -51,6 +52,7 @@ import { Logo } from '@/components/ui/logo'
 interface TopbarProps {
   project: Project | null
   onNewProject: (mode?: ProjectMode) => void
+  onEndProject?: () => void
   onSaveProject: () => void
   onLoadProject: (project: Project, features: DrawFeature[]) => void
   onDeleteProject?: (projectId: string) => void
@@ -76,6 +78,7 @@ interface TopbarProps {
 export function Topbar({
   project,
   onNewProject,
+  onEndProject,
   onSaveProject,
   onLoadProject,
   onDeleteProject,
@@ -285,19 +288,17 @@ export function Topbar({
           {isFullscreen ? <Minimize className="w-4 h-4" /> : <Maximize className="w-4 h-4" />}
         </Button>
 
-        <Button
+        {project && onEndProject && (
-          variant={isAuditOpen ? 'default' : 'outline'}
+          <Button
-          className="hidden md:flex h-9 px-2 relative"
+            variant="outline"
-          onClick={onToggleAudit}
+            className="hidden md:flex h-9 px-2 md:px-3 border-red-300 text-red-600 hover:bg-red-50 hover:text-red-700 dark:border-red-800 dark:text-red-400 dark:hover:bg-red-950/40"
-          title="Audit Trail"
+            onClick={onEndProject}
-        >
+            title="Einsatz speichern und schliessen"
-          <ClipboardList className="w-4 h-4" />
+          >
-          {auditLog.length > 0 && (
+            <CheckCircle2 className="w-4 h-4 lg:mr-1" />
-            <span className="absolute -top-1 -right-1 w-4 h-4 bg-primary text-primary-foreground text-[10px] rounded-full flex items-center justify-center font-bold">
+            <span className="hidden lg:inline">Einsatz beenden</span>
-              {auditLog.length > 99 ? '99' : auditLog.length}
+          </Button>
-            </span>
+        )}
-          )}
-        </Button>
 
         {/* Desktop: User menu dropdown */}
         {userName && onLogout && (
@@ -366,10 +367,6 @@ export function Topbar({
               <Settings className="w-4 h-4 mr-2" />
               Einstellungen
             </DropdownMenuItem>
-            <DropdownMenuItem onClick={onToggleAudit}>
-              <ClipboardList className="w-4 h-4 mr-2" />
-              Audit Trail {auditLog.length > 0 && `(${auditLog.length})`}
-            </DropdownMenuItem>
             {onLogout && (
               <DropdownMenuItem onClick={onLogout} className="text-destructive">
                 <LogOut className="w-4 h-4 mr-2" />

src/components/map/measure-panel.tsx

@@ -103,18 +103,18 @@ export function MeasurePanel({ measurement, hoseTypes, onClose }: MeasurePanelPr
 
           <div className="grid grid-cols-[1fr_auto] gap-2">
             <Select value={selectedHoseName} onValueChange={setSelectedHoseName}>
-              <SelectTrigger className="h-8 text-xs"><SelectValue placeholder="Schlauchtyp" /></SelectTrigger>
+              <SelectTrigger className="h-8 text-xs min-w-0"><SelectValue placeholder="Schlauchtyp" /></SelectTrigger>
-              <SelectContent>
+              <SelectContent className="z-[2000]">
                 {hoseTypes.map(h => (
                   <SelectItem key={h.name} value={h.name}>
-                    {h.name} · {h.diameterMm}mm · {h.flowRateLpm} l/min{h.isDefault ? ' ★' : ''}
+                    {h.name}{h.isDefault ? ' ★' : ''} · {h.flowRateLpm} l/min
                   </SelectItem>
                 ))}
               </SelectContent>
             </Select>
             <Select value={nozzlePressure} onValueChange={setNozzlePressure}>
-              <SelectTrigger className="h-8 text-xs w-[92px]" title="Druck am Strahlrohr/Verteiler"><SelectValue /></SelectTrigger>
+              <SelectTrigger className="h-8 text-xs w-[92px] shrink-0" title="Druck am Strahlrohr/Verteiler"><SelectValue /></SelectTrigger>
-              <SelectContent>
+              <SelectContent className="z-[2000]">
                 {['4', '5', '6', '8'].map(p => <SelectItem key={p} value={p}>{p} bar</SelectItem>)}
               </SelectContent>
             </Select>

src/hooks/use-auto-save.ts

@@ -10,6 +10,10 @@ interface UseAutoSaveOptions {
   socketRef: React.MutableRefObject<any>
   isEditingByMe: boolean
   setSyncQueueCount: (count: number) => void
+  /** Aktuelle Features-Version des Projekts (optimistischer Lock) */
+  featuresVersionRef: React.MutableRefObject<number>
+  /** Wird bei einem Speicher-Konflikt (409) mit dem Server-Stand aufgerufen */
+  onConflict: (serverFeatures: DrawFeature[], serverVersion: number) => void
 }
 
 export function useAutoSave({
@@ -20,11 +24,15 @@ export function useAutoSave({
   socketRef,
   isEditingByMe,
   setSyncQueueCount,
+  featuresVersionRef,
+  onConflict,
 }: UseAutoSaveOptions) {
-  // Persist features to localStorage on change (including empty array to reflect deletions)
+  // Persist features to localStorage on change (per project — verhindert, dass Features
+  // eines Projekts in ein anderes "bluten"). Inkl. leerem Array (spiegelt Löschungen).
   useEffect(() => {
-    localStorage.setItem('lageplan-features', JSON.stringify(features))
+    if (!currentProject?.id) return
-  }, [features])
+    localStorage.setItem(`lageplan-features-${currentProject.id}`, JSON.stringify(features))
+  }, [features, currentProject?.id])
 
   // Auto-save to API — debounced 2s after every feature change + fallback interval
   const saveTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
@@ -32,7 +40,7 @@ export function useAutoSave({
     if (!currentProject?.id) return
     const url = `/api/projects/${currentProject.id}/features`
     const mapInstance = mapRef.current
-    const body: any = { features: featuresRef.current }
+    const body: any = { features: featuresRef.current, baseVersion: featuresVersionRef.current }
     if (mapInstance) {
       const c = mapInstance.getCenter()
       body.mapCenter = { lng: c.lng, lat: c.lat }
@@ -54,11 +62,22 @@ export function useAutoSave({
         body: JSON.stringify(body),
       })
       if (res.ok) {
+        const data = await res.json().catch(() => null)
+        if (data && typeof data.featuresVersion === 'number') {
+          featuresVersionRef.current = data.featuresVersion
+        }
         console.log('[Auto-Save] Features gespeichert')
         socketRef.current?.emit('features-updated', {
           projectId: currentProject.id,
           features: featuresRef.current,
         })
+      } else if (res.status === 409) {
+        // Konflikt: jemand anderes hat zwischenzeitlich gespeichert → Server-Stand übernehmen
+        const data = await res.json().catch(() => null)
+        if (data?.conflict) {
+          console.warn('[Auto-Save] Versionskonflikt — Server-Stand übernehmen')
+          onConflict(data.features || [], data.featuresVersion ?? featuresVersionRef.current)
+        }
       } else if (res.status === 404) {
         console.warn('[Auto-Save] Projekt nicht in DB')
       }
@@ -68,7 +87,7 @@ export function useAutoSave({
       setSyncQueueCount(getSyncQueue().length)
       console.warn('[Auto-Save] Netzwerkfehler — in Sync-Queue:', e)
     }
-  }, [currentProject, mapRef, featuresRef, socketRef, setSyncQueueCount])
+  }, [currentProject, mapRef, featuresRef, socketRef, setSyncQueueCount, featuresVersionRef, onConflict])
 
   // Debounced save on every feature change (2s delay)
   useEffect(() => {
@@ -81,8 +100,10 @@ export function useAutoSave({
   // Also save on page unload / tab switch
   useEffect(() => {
     const handleBeforeUnload = () => {
-      if (currentProject?.id && featuresRef.current.length > 0) {
+      // Nur der aktive Bearbeiter persistiert beim Schliessen — auch eine leere Liste,
-        const payload = JSON.stringify({ features: featuresRef.current })
+      // damit "alles gelöscht + Tab zu" nicht die alten Elemente in der DB stehen lässt.
+      if (currentProject?.id && isEditingByMe) {
+        const payload = JSON.stringify({ features: featuresRef.current, baseVersion: featuresVersionRef.current })
         navigator.sendBeacon(`/api/projects/${currentProject.id}/features`, new Blob([payload], { type: 'application/json' }))
       }
     }

src/lib/offline-sync.ts

@@ -58,8 +58,12 @@ export async function flushSyncQueue(): Promise<{ success: number; failed: numbe
       })
       if (res.ok) {
         success++
+      } else if (res.status >= 400 && res.status < 500) {
+        // Client-Fehler (403/404/...) = dauerhaft. Retry bringt nichts → verwerfen,
+        // damit die Queue nicht verstopft und nicht ewig "Sync-Fehler" meldet.
+        failed++
       } else {
-        // Server error — keep in queue for retry
+        // Server-Fehler (5xx) — später erneut versuchen
         remaining.push(item)
         failed++
       }

src/types/index.ts

@@ -12,6 +12,7 @@ export interface Project {
   mapCenter: { lng: number; lat: number }
   mapZoom: number
   isLocked: boolean
+  featuresVersion?: number
   editingById?: string | null
   editingUserName?: string | null
   editingStartedAt?: string | null