diff --git a/backend/src/database/DatabaseInterface.ts b/backend/src/database/DatabaseInterface.ts
index 380eacb..d1798e5 100644
--- a/backend/src/database/DatabaseInterface.ts
+++ b/backend/src/database/DatabaseInterface.ts
@@ -112,7 +112,7 @@ export interface DatabaseInterface {
   listUsers(): DBUser[];
 
   // Projects
-  listProjects(): DBProject[];
+  listProjects(ownerId?: string): DBProject[];
   getProject(id: string): DBProject | null;
   createProject(data: Partial<DBProject>): DBProject;
   updateProject(id: string, data: Partial<DBProject>): DBProject | null;
diff --git a/backend/src/database/SqliteAdapter.ts b/backend/src/database/SqliteAdapter.ts
index 6fc4ea4..834d0ff 100644
--- a/backend/src/database/SqliteAdapter.ts
+++ b/backend/src/database/SqliteAdapter.ts
@@ -73,7 +73,10 @@ export class SqliteAdapter implements DatabaseInterface {
   }
 
   // ─── Projects ──────────────────────────────────────
-  listProjects(): DBProject[] {
+  listProjects(ownerId?: string): DBProject[] {
+    if (ownerId) {
+      return this.db.prepare('SELECT * FROM projects WHERE owner_id = ? ORDER BY updated_at DESC').all(ownerId) as DBProject[];
+    }
     return this.db.prepare('SELECT * FROM projects ORDER BY updated_at DESC').all() as DBProject[];
   }
 
diff --git a/backend/src/routes/projects.ts b/backend/src/routes/projects.ts
index d14acc2..22cc27f 100644
--- a/backend/src/routes/projects.ts
+++ b/backend/src/routes/projects.ts
@@ -7,10 +7,11 @@ import { requireAuth } from '../auth/authMiddleware.js';
 import type { AuthService } from '../auth/AuthService.js';
 
 export function registerProjectRoutes(fastify: FastifyInstance, db: DatabaseInterface, authService: AuthService) {
-  // List all projects
+  // List projects owned by the authenticated user
   fastify.get('/api/projects', async (request, reply) => {
-    if (!requireAuth(request, reply, authService)) return;
-    return db.listProjects();
+    const user = requireAuth(request, reply, authService);
+    if (!user) return;
+    return db.listProjects(user.id);
   });
 
   // Get single project
@@ -24,10 +25,11 @@ export function registerProjectRoutes(fastify: FastifyInstance, db: DatabaseInte
 
   // Create project
   fastify.post('/api/projects', async (request, reply) => {
-    if (!requireAuth(request, reply, authService)) return;
+    const user = requireAuth(request, reply, authService);
+    if (!user) return;
     const body = request.body as Partial<DBProject>;
     if (!body.name) return reply.code(400).send({ error: 'Name is required' });
-    return reply.code(201).send(db.createProject(body));
+    return reply.code(201).send(db.createProject({ ...body, owner_id: user.id }));
   });
 
   // Update project
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index f4434b1..231e08a 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -534,7 +534,13 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
   const handleRenameBlock = useCallback((id: string, name: string) => {
     setBlocks((prev) => prev.map((b) => b.id === id ? { ...b, name } : b));
     setCommandHistory((prev) => [...prev, { prefix: '·', text: `Block umbenannt: ${name}`, type: 'info' }]);
-  }, []);
+    // Persist rename to backend
+    if (token) {
+      updateBlock(token, id, { name }).catch((err) => {
+        console.error('Failed to save block rename:', err);
+      });
+    }
+  }, [token]);
 
   const handleDuplicateBlock = useCallback((id: string) => {
     setBlocks((prev) => {
@@ -547,10 +553,16 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
         name: `${block.name} (Kopie)`,
         elements: block.elements.map((el) => ({ ...el, id: `${el.id}_copy_${Date.now()}` })),
       };
+      // Persist duplicate to backend
+      if (drawingId && token) {
+        createBlockTyped(token, drawingId, copy).catch((err) => {
+          console.error('Failed to save duplicated block:', err);
+        });
+      }
       return [...prev, copy];
     });
     setCommandHistory((prev) => [...prev, { prefix: '·', text: 'Block dupliziert', type: 'info' }]);
-  }, []);
+  }, [drawingId, token]);
 
   const handleDeleteBlock = useCallback((id: string) => {
     setBlocks((prev) => prev.filter((b) => b.id !== id));
@@ -643,15 +655,42 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     const result = await importFile(file);
     if (result.success) {
       setElements((prev) => [...prev, ...result.elements]);
+      // Push imported elements to Yjs and backend
+      for (const el of result.elements) {
+        collab.setElement(el);
+      }
+      if (drawingId && token) {
+        setSavedStatus('Speichert…');
+        Promise.all(result.elements.map(el => createElementTyped(token, drawingId, el)))
+          .then(() => setSavedStatus('gespeichert'))
+          .catch((err) => {
+            console.error('Failed to save imported elements:', err);
+            setSavedStatus('Fehler beim Speichern');
+          });
+      }
       if (result.layers && result.layers.length > 0) {
-        setLayers((prev) => {
-          const existingIds = new Set(prev.map(l => l.id));
-          const newLayers = result.layers!.filter(l => !existingIds.has(l.id));
-          return [...prev, ...newLayers];
-        });
+        const existingIds = new Set(layers.map(l => l.id));
+        const newLayers = result.layers.filter(l => !existingIds.has(l.id));
+        setLayers((prev) => [...prev, ...newLayers]);
+        // Push imported layers to Yjs and backend
+        for (const layer of newLayers) {
+          collab.setLayer(layer);
+        }
+        if (drawingId && token) {
+          Promise.all(newLayers.map(l => createLayerTyped(token, drawingId, l)))
+            .catch((err) => console.error('Failed to save imported layers:', err));
+        }
       }
       if (result.blocks && result.blocks.length > 0) {
         setBlocks((prev) => [...prev, ...result.blocks!]);
+        // Push imported blocks to Yjs and backend
+        for (const block of result.blocks) {
+          collab.setBlock(block);
+        }
+        if (drawingId && token) {
+          Promise.all(result.blocks.map(b => createBlockTyped(token, drawingId, b)))
+            .catch((err) => console.error('Failed to save imported blocks:', err));
+        }
       }
       setCommandHistory((prev) => [...prev, { prefix: '·', text: `Importiert: ${result.elements.length} Elemente aus ${file.name}`, type: 'info' }]);
       if (result.warnings.length > 0) {
@@ -660,7 +699,7 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     } else {
       setCommandHistory((prev) => [...prev, { prefix: '·', text: `Import fehlgeschlagen: ${result.error || 'Unbekannter Fehler'}`, type: 'info' }]);
     }
-  }, []);
+  }, [drawingId, token, collab, layers]);
 
   const handleExport = useCallback(async (format: ExportFormat) => {
     const projectData: ProjectData = {
@@ -866,8 +905,20 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     });
   }, [drawingId, token]);
   const handleToggleLayer = useCallback((id: string) => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, visible: !l.visible } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, visible: !l.visible } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { visible: changed.visible }).catch((err) => {
+            console.error('Failed to save layer visibility:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
   const handleDeleteLayer = useCallback((id: string) => {
     setLayers((prev) => prev.filter((l) => l.id !== id));
     // Delete from backend
@@ -878,29 +929,95 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     }
   }, [token]);
   const handleRenameLayer = useCallback((id: string, name: string) => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, name } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, name } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { name }).catch((err) => {
+            console.error('Failed to save layer rename:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
   const handleDuplicateLayer = useCallback((id: string) => {
     setLayers((prev) => {
       const layer = prev.find((l) => l.id === id);
       if (!layer) return prev;
       const newId = `layer-${Date.now()}`;
       const copy: CADLayer = { ...layer, id: newId, name: `${layer.name} (Kopie)`, sortOrder: prev.length };
+      collab.setLayer(copy);
+      if (drawingId && token) {
+        createLayerTyped(token, drawingId, copy).catch((err) => {
+          console.error('Failed to save duplicated layer:', err);
+        });
+      }
       return [...prev, copy];
     });
-  }, []);
+  }, [drawingId, token, collab]);
   const handleToggleLock = useCallback((id: string) => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, locked: !l.locked } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, locked: !l.locked } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { locked: changed.locked }).catch((err) => {
+            console.error('Failed to save layer lock state:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
   const handleUpdateLayerColor = useCallback((id: string, color: string) => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, color } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, color } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { color }).catch((err) => {
+            console.error('Failed to save layer color:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
   const handleUpdateLayerLineType = useCallback((id: string, lineType: 'solid' | 'dashed' | 'dotted') => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, lineType } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, lineType } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { lineType }).catch((err) => {
+            console.error('Failed to save layer line type:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
   const handleUpdateLayerTransparency = useCallback((id: string, transparency: number) => {
-    setLayers((prev) => prev.map((l) => l.id === id ? { ...l, transparency } : l));
-  }, []);
+    setLayers((prev) => {
+      const updated = prev.map((l) => l.id === id ? { ...l, transparency } : l);
+      const changed = updated.find((l) => l.id === id);
+      if (changed) {
+        collab.setLayer(changed);
+        if (token) {
+          updateLayer(token, id, { transparency }).catch((err) => {
+            console.error('Failed to save layer transparency:', err);
+          });
+        }
+      }
+      return updated;
+    });
+  }, [token, collab]);
 
   const handleZoomIn = useCallback(() => {
     setCommandHistory((prev) => [...prev, { prefix: '·', text: 'Zoom: vergrößert', type: 'info' }]);