diff --git a/docs/circuit-list-editor-api.md b/docs/circuit-list-editor-api.md
index 2c42938..ee2580c 100644
--- a/docs/circuit-list-editor-api.md
+++ b/docs/circuit-list-editor-api.md
@@ -156,8 +156,12 @@ These remain for migration/legacy views. New circuit-list interactions must use
   - returns all linked circuit device rows with distribution-board/circuit context and field differences
 - `POST /project-devices/projects/:projectId/:projectDeviceId/synchronize`
   - applies only explicitly selected fields to explicitly selected linked rows
+- `POST /project-devices/projects/:projectId/:projectDeviceId/restore`
+  - restores the captured pre-sync values for session-local undo
 - `POST /project-devices/projects/:projectId/:projectDeviceId/disconnect`
   - disconnects explicitly selected rows without changing their local values
+- `POST /project-devices/projects/:projectId/:projectDeviceId/reconnect`
+  - restores a disconnected link if the row has not been linked elsewhere meanwhile
 
 `displayName` is included in the comparison but is not selected by default in the UI. Updating a
 project device never triggers synchronization implicitly.
diff --git a/docs/circuit-list-editor-known-limitations.md b/docs/circuit-list-editor-known-limitations.md
index 0f88c73..70f289b 100644
--- a/docs/circuit-list-editor-known-limitations.md
+++ b/docs/circuit-list-editor-known-limitations.md
@@ -9,5 +9,3 @@
 - Sorting is view-only until users explicitly apply sorted order.
 - Cross-section circuit drag-reorder is intentionally blocked.
 - Legacy consumer and circuit-first paths coexist; migration is transitional and still requires operational discipline.
-- Project-device synchronization and disconnect actions are explicit, but are not yet connected to an undo command.
-- Multi-row project-device synchronization is sequential and not yet wrapped in one database transaction.
diff --git a/src/app/projects/[projectId]/page.tsx b/src/app/projects/[projectId]/page.tsx
index 7e889b5..dc6163c 100644
--- a/src/app/projects/[projectId]/page.tsx
+++ b/src/app/projects/[projectId]/page.tsx
@@ -20,6 +20,8 @@ import {
   listProjectDevices,
   listProjects,
   listRooms,
+  reconnectProjectDeviceRows,
+  restoreProjectDeviceRows,
   synchronizeProjectDeviceRows,
   updateProjectDevice,
   updateProjectSettings,
@@ -32,6 +34,7 @@ import type {
   GlobalDeviceDto,
   ProjectDeviceDto,
   ProjectDeviceSyncPreviewDto,
+  ProjectDeviceSyncRestoreRowDto,
   ProjectDto,
   RoomDto,
 } from "../../../frontend/types";
@@ -54,6 +57,10 @@ const projectDeviceSyncFieldLabels: Record<ProjectDeviceSyncField, string> = {
   remark: "Bemerkung",
 };
 
+type ProjectDeviceUndoState =
+  | { kind: "synchronize"; projectDeviceId: string; rows: ProjectDeviceSyncRestoreRowDto[] }
+  | { kind: "disconnect"; projectDeviceId: string; rowIds: string[] };
+
 const emptyProjectDevice: CreateProjectDeviceInput = {
   name: "",
   displayName: "",
@@ -110,6 +117,7 @@ export default function ProjectDetailPage() {
   const [syncPreview, setSyncPreview] = useState<ProjectDeviceSyncPreviewDto | null>(null);
   const [selectedSyncRowIds, setSelectedSyncRowIds] = useState<string[]>([]);
   const [selectedSyncFields, setSelectedSyncFields] = useState<ProjectDeviceSyncField[]>([]);
+  const [projectDeviceUndo, setProjectDeviceUndo] = useState<ProjectDeviceUndoState | null>(null);
   const [error, setError] = useState<string | null>(null);
   const [isSaving, setIsSaving] = useState(false);
 
@@ -347,6 +355,7 @@ export default function ProjectDetailPage() {
       return;
     }
     try {
+      setProjectDeviceUndo(null);
       const preview = await getProjectDeviceSyncPreview(projectId, projectDeviceId);
       setSyncPreview(preview);
       setSelectedSyncRowIds(preview.rows.filter((row) => row.differences.length > 0).map((row) => row.rowId));
@@ -380,14 +389,21 @@ export default function ProjectDetailPage() {
     setIsSaving(true);
     setError(null);
     try {
-      const preview = await synchronizeProjectDeviceRows(
+      const result = await synchronizeProjectDeviceRows(
         projectId,
         syncPreview.projectDevice.id,
         selectedSyncRowIds,
         selectedSyncFields
       );
-      setSyncPreview(preview);
-      setSelectedSyncRowIds(preview.rows.filter((row) => row.differences.length > 0).map((row) => row.rowId));
+      setSyncPreview(result.preview);
+      setSelectedSyncRowIds(
+        result.preview.rows.filter((row) => row.differences.length > 0).map((row) => row.rowId)
+      );
+      setProjectDeviceUndo({
+        kind: "synchronize",
+        projectDeviceId: syncPreview.projectDevice.id,
+        rows: result.undo.rows,
+      });
     } catch (err) {
       setError(err instanceof Error ? err.message : "Gerätezeilen konnten nicht synchronisiert werden.");
     } finally {
@@ -402,8 +418,17 @@ export default function ProjectDetailPage() {
     setIsSaving(true);
     setError(null);
     try {
-      await disconnectProjectDeviceRows(projectId, syncPreview.projectDevice.id, selectedSyncRowIds);
+      const result = await disconnectProjectDeviceRows(
+        projectId,
+        syncPreview.projectDevice.id,
+        selectedSyncRowIds
+      );
       await openProjectDeviceSyncPreview(syncPreview.projectDevice.id);
+      setProjectDeviceUndo({
+        kind: "disconnect",
+        projectDeviceId: syncPreview.projectDevice.id,
+        rowIds: result.undo.rowIds,
+      });
     } catch (err) {
       setError(err instanceof Error ? err.message : "Verknüpfungen konnten nicht getrennt werden.");
     } finally {
@@ -411,6 +436,35 @@ export default function ProjectDetailPage() {
     }
   }
 
+  async function handleUndoProjectDeviceOperation() {
+    if (!projectId || !projectDeviceUndo) {
+      return;
+    }
+    setIsSaving(true);
+    setError(null);
+    try {
+      const preview =
+        projectDeviceUndo.kind === "synchronize"
+          ? await restoreProjectDeviceRows(
+              projectId,
+              projectDeviceUndo.projectDeviceId,
+              projectDeviceUndo.rows
+            )
+          : await reconnectProjectDeviceRows(
+              projectId,
+              projectDeviceUndo.projectDeviceId,
+              projectDeviceUndo.rowIds
+            );
+      setSyncPreview(preview);
+      setSelectedSyncRowIds(preview.rows.filter((row) => row.differences.length > 0).map((row) => row.rowId));
+      setProjectDeviceUndo(null);
+    } catch (err) {
+      setError(err instanceof Error ? err.message : "Die letzte Aktion konnte nicht rückgängig gemacht werden.");
+    } finally {
+      setIsSaving(false);
+    }
+  }
+
   async function handleCopyGlobalToProject() {
     if (!projectId || !selectedGlobalDeviceId) {
       return;
@@ -1039,6 +1093,16 @@ export default function ProjectDetailPage() {
             </div>
 
             <div className="d-flex flex-wrap gap-2">
+              {projectDeviceUndo ? (
+                <button
+                  className="btn btn-outline-secondary"
+                  type="button"
+                  onClick={() => void handleUndoProjectDeviceOperation()}
+                  disabled={isSaving}
+                >
+                  Letzte Aktion rückgängig
+                </button>
+              ) : null}
               <button
                 className="btn btn-primary"
                 type="button"
diff --git a/src/db/repositories/circuit-device-row.repository.ts b/src/db/repositories/circuit-device-row.repository.ts
index a8dceba..b6a7974 100644
--- a/src/db/repositories/circuit-device-row.repository.ts
+++ b/src/db/repositories/circuit-device-row.repository.ts
@@ -1,11 +1,53 @@
 import crypto from "node:crypto";
-import { and, asc, eq, inArray } from "drizzle-orm";
+import { and, asc, eq, inArray, isNull } from "drizzle-orm";
 import { db } from "../client.js";
 import { circuitDeviceRows } from "../schema/circuit-device-rows.js";
 import { circuitLists } from "../schema/circuit-lists.js";
 import { circuits } from "../schema/circuits.js";
 import { distributionBoards } from "../schema/distribution-boards.js";
 
+export interface CircuitDeviceRowUpdateInput {
+  linkedProjectDeviceId?: string;
+  name: string;
+  displayName: string;
+  phaseType?: string;
+  connectionKind?: string;
+  costGroup?: string;
+  category?: string;
+  level?: string;
+  roomId?: string;
+  roomNumberSnapshot?: string;
+  roomNameSnapshot?: string;
+  quantity: number;
+  powerPerUnit: number;
+  simultaneityFactor: number;
+  cosPhi?: number;
+  remark?: string;
+  overriddenFields?: string;
+}
+
+function toUpdateValues(input: CircuitDeviceRowUpdateInput) {
+  return {
+    linkedProjectDeviceId: input.linkedProjectDeviceId ?? null,
+    name: input.name,
+    displayName: input.displayName,
+    phaseType: input.phaseType ?? null,
+    connectionKind: input.connectionKind ?? null,
+    costGroup: input.costGroup ?? null,
+    category: input.category ?? null,
+    level: input.level ?? null,
+    roomId: input.roomId ?? null,
+    roomNumberSnapshot: input.roomNumberSnapshot ?? null,
+    roomNameSnapshot: input.roomNameSnapshot ?? null,
+    quantity: input.quantity,
+    powerPerUnit: input.powerPerUnit,
+    simultaneityFactor: input.simultaneityFactor,
+    cosPhi: input.cosPhi ?? null,
+    remark: input.remark ?? null,
+    overriddenFields: input.overriddenFields ?? null,
+  };
+}
+
 export class CircuitDeviceRowRepository {
   async findById(rowId: string) {
     const [row] = await db.select().from(circuitDeviceRows).where(eq(circuitDeviceRows.id, rowId)).limit(1);
@@ -72,6 +114,21 @@ export class CircuitDeviceRowRepository {
       .orderBy(asc(distributionBoards.name), asc(circuits.equipmentIdentifier), asc(circuitDeviceRows.sortOrder));
   }
 
+  async listLinkStatesByIds(projectId: string, rowIds: string[]) {
+    if (rowIds.length === 0) {
+      return [];
+    }
+    return db
+      .select({
+        id: circuitDeviceRows.id,
+        linkedProjectDeviceId: circuitDeviceRows.linkedProjectDeviceId,
+      })
+      .from(circuitDeviceRows)
+      .innerJoin(circuits, eq(circuitDeviceRows.circuitId, circuits.id))
+      .innerJoin(circuitLists, eq(circuits.circuitListId, circuitLists.id))
+      .where(and(eq(circuitLists.projectId, projectId), inArray(circuitDeviceRows.id, rowIds)));
+  }
+
   async create(input: {
     circuitId: string;
     linkedProjectDeviceId?: string;
@@ -123,50 +180,72 @@ export class CircuitDeviceRowRepository {
 
   async update(
     rowId: string,
-    input: {
-      linkedProjectDeviceId?: string;
-      name: string;
-      displayName: string;
-      phaseType?: string;
-      connectionKind?: string;
-      costGroup?: string;
-      category?: string;
-      level?: string;
-      roomId?: string;
-      roomNumberSnapshot?: string;
-      roomNameSnapshot?: string;
-      quantity: number;
-      powerPerUnit: number;
-      simultaneityFactor: number;
-      cosPhi?: number;
-      remark?: string;
-      overriddenFields?: string;
-    }
+    input: CircuitDeviceRowUpdateInput
   ) {
     await db
       .update(circuitDeviceRows)
-      .set({
-        linkedProjectDeviceId: input.linkedProjectDeviceId ?? null,
-        name: input.name,
-        displayName: input.displayName,
-        phaseType: input.phaseType ?? null,
-        connectionKind: input.connectionKind ?? null,
-        costGroup: input.costGroup ?? null,
-        category: input.category ?? null,
-        level: input.level ?? null,
-        roomId: input.roomId ?? null,
-        roomNumberSnapshot: input.roomNumberSnapshot ?? null,
-        roomNameSnapshot: input.roomNameSnapshot ?? null,
-        quantity: input.quantity,
-        powerPerUnit: input.powerPerUnit,
-        simultaneityFactor: input.simultaneityFactor,
-        cosPhi: input.cosPhi ?? null,
-        remark: input.remark ?? null,
-        overriddenFields: input.overriddenFields ?? null,
-      })
+      .set(toUpdateValues(input))
       .where(eq(circuitDeviceRows.id, rowId));
   }
 
+  updateLinkedRowsTransactional(
+    projectDeviceId: string,
+    changes: Array<{ rowId: string; input: CircuitDeviceRowUpdateInput }>
+  ) {
+    db.transaction((tx) => {
+      for (const change of changes) {
+        const result = tx
+          .update(circuitDeviceRows)
+          .set(toUpdateValues(change.input))
+          .where(
+            and(
+              eq(circuitDeviceRows.id, change.rowId),
+              eq(circuitDeviceRows.linkedProjectDeviceId, projectDeviceId)
+            )
+          )
+          .run();
+        if (result.changes !== 1) {
+          throw new Error("A linked row changed before the operation could be completed.");
+        }
+      }
+    });
+  }
+
+  disconnectLinkedRowsTransactional(projectDeviceId: string, rowIds: string[]) {
+    db.transaction((tx) => {
+      for (const rowId of rowIds) {
+        const result = tx
+          .update(circuitDeviceRows)
+          .set({ linkedProjectDeviceId: null })
+          .where(
+            and(
+              eq(circuitDeviceRows.id, rowId),
+              eq(circuitDeviceRows.linkedProjectDeviceId, projectDeviceId)
+            )
+          )
+          .run();
+        if (result.changes !== 1) {
+          throw new Error("A linked row changed before the operation could be completed.");
+        }
+      }
+    });
+  }
+
+  reconnectRowsTransactional(projectDeviceId: string, rowIds: string[]) {
+    db.transaction((tx) => {
+      for (const rowId of rowIds) {
+        const result = tx
+          .update(circuitDeviceRows)
+          .set({ linkedProjectDeviceId: projectDeviceId })
+          .where(and(eq(circuitDeviceRows.id, rowId), isNull(circuitDeviceRows.linkedProjectDeviceId)))
+          .run();
+        if (result.changes !== 1) {
+          throw new Error("A disconnected row changed before the operation could be undone.");
+        }
+      }
+    });
+  }
+
   async delete(rowId: string) {
     await db.delete(circuitDeviceRows).where(eq(circuitDeviceRows.id, rowId));
   }
diff --git a/src/domain/services/project-device-sync.service.ts b/src/domain/services/project-device-sync.service.ts
index 3c106c0..d27a612 100644
--- a/src/domain/services/project-device-sync.service.ts
+++ b/src/domain/services/project-device-sync.service.ts
@@ -10,9 +10,22 @@ type LinkedRow = Awaited<ReturnType<CircuitDeviceRowRepository["listLinkedByProj
 
 type SyncDependencies = {
   projectDeviceRepository: Pick<ProjectDeviceRepository, "findById">;
-  deviceRowRepository: Pick<CircuitDeviceRowRepository, "listLinkedByProjectDevice" | "update">;
+  deviceRowRepository: Pick<
+    CircuitDeviceRowRepository,
+    | "listLinkedByProjectDevice"
+    | "listLinkStatesByIds"
+    | "updateLinkedRowsTransactional"
+    | "disconnectLinkedRowsTransactional"
+    | "reconnectRowsTransactional"
+  >;
 };
 
+export interface ProjectDeviceSyncRestoreRow {
+  rowId: string;
+  values: Partial<Record<ProjectDeviceSyncField, string | number | null>>;
+  overriddenFields: ProjectDeviceSyncField[];
+}
+
 export function parseOverriddenFields(value: string | null | undefined): ProjectDeviceSyncField[] {
   if (!value) {
     return [];
@@ -106,7 +119,13 @@ export class ProjectDeviceSyncService {
     const linkedRows = await this.deviceRowRepository.listLinkedByProjectDevice(projectId, projectDeviceId);
     const selectedRows = this.resolveSelectedRows(linkedRows, rowIds);
     const selectedFields = [...new Set(fields)];
+    const undoRows: ProjectDeviceSyncRestoreRow[] = selectedRows.map((row) => ({
+      rowId: row.id,
+      values: Object.fromEntries(selectedFields.map((field) => [field, row[field] ?? null])),
+      overriddenFields: parseOverriddenFields(row.overriddenFields),
+    }));
 
+    const changes = [];
     for (const row of selectedRows) {
       const next = this.copyRow(row);
       for (const field of selectedFields) {
@@ -116,24 +135,62 @@ export class ProjectDeviceSyncService {
         (field) => !selectedFields.includes(field)
       );
       next.overriddenFields = serializeOverriddenFields(remainingOverrides);
-      await this.deviceRowRepository.update(row.id, next);
+      changes.push({ rowId: row.id, input: next });
     }
+    this.deviceRowRepository.updateLinkedRowsTransactional(projectDeviceId, changes);
 
-    return this.getPreview(projectId, projectDeviceId);
+    return {
+      preview: await this.getPreview(projectId, projectDeviceId),
+      undo: { rows: undoRows },
+    };
   }
 
   async disconnect(projectId: string, projectDeviceId: string, rowIds: string[]) {
     const linkedRows = await this.deviceRowRepository.listLinkedByProjectDevice(projectId, projectDeviceId);
     const selectedRows = this.resolveSelectedRows(linkedRows, rowIds);
+    const disconnectedRowIds = selectedRows.map((row) => row.id);
 
-    for (const row of selectedRows) {
-      await this.deviceRowRepository.update(row.id, {
-        ...this.copyRow(row),
-        linkedProjectDeviceId: undefined,
-      });
+    this.deviceRowRepository.disconnectLinkedRowsTransactional(projectDeviceId, disconnectedRowIds);
+
+    return { disconnectedRowIds, undo: { rowIds: disconnectedRowIds } };
+  }
+
+  async restore(
+    projectId: string,
+    projectDeviceId: string,
+    restoreRows: ProjectDeviceSyncRestoreRow[]
+  ) {
+    const linkedRows = await this.deviceRowRepository.listLinkedByProjectDevice(projectId, projectDeviceId);
+    const selectedRows = this.resolveSelectedRows(linkedRows, restoreRows.map((row) => row.rowId));
+    const restoreById = new Map(restoreRows.map((row) => [row.rowId, row]));
+    const changes = selectedRows.map((row) => {
+      const restore = restoreById.get(row.id)!;
+      const next = this.copyRow(row);
+      for (const [field, value] of Object.entries(restore.values) as Array<
+        [ProjectDeviceSyncField, string | number | null]
+      >) {
+        Object.assign(next, { [field]: value ?? undefined });
+      }
+      next.overriddenFields = serializeOverriddenFields(restore.overriddenFields);
+      return { rowId: row.id, input: next };
+    });
+
+    this.deviceRowRepository.updateLinkedRowsTransactional(projectDeviceId, changes);
+    return this.getPreview(projectId, projectDeviceId);
+  }
+
+  async reconnect(projectId: string, projectDeviceId: string, rowIds: string[]) {
+    const projectDevice = await this.projectDeviceRepository.findById(projectId, projectDeviceId);
+    if (!projectDevice) {
+      throw new Error("Project device not found.");
     }
-
-    return { disconnectedRowIds: selectedRows.map((row) => row.id) };
+    const uniqueRowIds = [...new Set(rowIds)];
+    const linkStates = await this.deviceRowRepository.listLinkStatesByIds(projectId, uniqueRowIds);
+    if (linkStates.length !== uniqueRowIds.length || linkStates.some((row) => row.linkedProjectDeviceId !== null)) {
+      throw new Error("One or more rows cannot be reconnected.");
+    }
+    this.deviceRowRepository.reconnectRowsTransactional(projectDeviceId, uniqueRowIds);
+    return this.getPreview(projectId, projectDeviceId);
   }
 
   private resolveSelectedRows(linkedRows: LinkedRow[], rowIds: string[]) {
diff --git a/src/frontend/types.ts b/src/frontend/types.ts
index f3b1bae..a969a6d 100644
--- a/src/frontend/types.ts
+++ b/src/frontend/types.ts
@@ -210,6 +210,26 @@ export interface ProjectDeviceSyncPreviewDto {
   rows: ProjectDeviceSyncRowDto[];
 }
 
+export interface ProjectDeviceSyncRestoreRowDto {
+  rowId: string;
+  values: Partial<Record<ProjectDeviceSyncField, string | number | null>>;
+  overriddenFields: ProjectDeviceSyncField[];
+}
+
+export interface ProjectDeviceSyncResultDto {
+  preview: ProjectDeviceSyncPreviewDto;
+  undo: {
+    rows: ProjectDeviceSyncRestoreRowDto[];
+  };
+}
+
+export interface ProjectDeviceDisconnectResultDto {
+  disconnectedRowIds: string[];
+  undo: {
+    rowIds: string[];
+  };
+}
+
 export interface CircuitTreeDeviceRowDto {
   id: string;
   linkedProjectDeviceId?: string;
diff --git a/src/frontend/utils/api.ts b/src/frontend/utils/api.ts
index 2bd49cf..8de198a 100644
--- a/src/frontend/utils/api.ts
+++ b/src/frontend/utils/api.ts
@@ -10,7 +10,10 @@ import type {
   FloorDto,
   GlobalDeviceDto,
   ProjectDeviceDto,
+  ProjectDeviceDisconnectResultDto,
   ProjectDeviceSyncPreviewDto,
+  ProjectDeviceSyncRestoreRowDto,
+  ProjectDeviceSyncResultDto,
   ProjectDto,
   RoomDto,
   UpdateConsumerInput,
@@ -300,7 +303,7 @@ export function synchronizeProjectDeviceRows(
   rowIds: string[],
   fields: ProjectDeviceSyncField[]
 ) {
-  return request<ProjectDeviceSyncPreviewDto>(
+  return request<ProjectDeviceSyncResultDto>(
     `/api/project-devices/projects/${projectId}/${projectDeviceId}/synchronize`,
     {
       method: "POST",
@@ -314,7 +317,7 @@ export function disconnectProjectDeviceRows(
   projectDeviceId: string,
   rowIds: string[]
 ) {
-  return request<{ disconnectedRowIds: string[] }>(
+  return request<ProjectDeviceDisconnectResultDto>(
     `/api/project-devices/projects/${projectId}/${projectDeviceId}/disconnect`,
     {
       method: "POST",
@@ -322,3 +325,31 @@ export function disconnectProjectDeviceRows(
     }
   );
 }
+
+export function restoreProjectDeviceRows(
+  projectId: string,
+  projectDeviceId: string,
+  rows: ProjectDeviceSyncRestoreRowDto[]
+) {
+  return request<ProjectDeviceSyncPreviewDto>(
+    `/api/project-devices/projects/${projectId}/${projectDeviceId}/restore`,
+    {
+      method: "POST",
+      body: JSON.stringify({ rows }),
+    }
+  );
+}
+
+export function reconnectProjectDeviceRows(
+  projectId: string,
+  projectDeviceId: string,
+  rowIds: string[]
+) {
+  return request<ProjectDeviceSyncPreviewDto>(
+    `/api/project-devices/projects/${projectId}/${projectDeviceId}/reconnect`,
+    {
+      method: "POST",
+      body: JSON.stringify({ rowIds }),
+    }
+  );
+}
diff --git a/src/server/controllers/project-device.controller.ts b/src/server/controllers/project-device.controller.ts
index ac6cd29..c2b2f6e 100644
--- a/src/server/controllers/project-device.controller.ts
+++ b/src/server/controllers/project-device.controller.ts
@@ -5,6 +5,8 @@ import { ProjectDeviceSyncService } from "../../domain/services/project-device-s
 import {
   createProjectDeviceSchema,
   disconnectProjectDeviceRowsSchema,
+  reconnectProjectDeviceRowsSchema,
+  restoreProjectDeviceRowsSchema,
   synchronizeProjectDeviceRowsSchema,
   updateProjectDeviceSchema,
 } from "../../shared/validation/project-device.schemas.js";
@@ -116,18 +118,35 @@ export async function synchronizeProjectDeviceRows(req: Request, res: Response)
     return res.status(400).json({ error: parsed.error.flatten() });
   }
   try {
-    const preview = await projectDeviceSyncService.synchronize(
+    const result = await projectDeviceSyncService.synchronize(
       projectId,
       projectDeviceId,
       parsed.data.rowIds,
       parsed.data.fields
     );
-    return res.json(preview);
+    return res.json(result);
   } catch (error) {
     return res.status(400).json({ error: error instanceof Error ? error.message : "Failed to synchronize rows." });
   }
 }
 
+export async function restoreProjectDeviceRows(req: Request, res: Response) {
+  const { projectId, projectDeviceId } = req.params;
+  if (typeof projectId !== "string" || typeof projectDeviceId !== "string") {
+    return res.status(400).json({ error: "Invalid parameters" });
+  }
+  const parsed = restoreProjectDeviceRowsSchema.safeParse(req.body);
+  if (!parsed.success) {
+    return res.status(400).json({ error: parsed.error.flatten() });
+  }
+  try {
+    const preview = await projectDeviceSyncService.restore(projectId, projectDeviceId, parsed.data.rows);
+    return res.json(preview);
+  } catch (error) {
+    return res.status(400).json({ error: error instanceof Error ? error.message : "Failed to restore rows." });
+  }
+}
+
 export async function disconnectProjectDeviceRows(req: Request, res: Response) {
   const { projectId, projectDeviceId } = req.params;
   if (typeof projectId !== "string" || typeof projectDeviceId !== "string") {
@@ -144,3 +163,20 @@ export async function disconnectProjectDeviceRows(req: Request, res: Response) {
     return res.status(400).json({ error: error instanceof Error ? error.message : "Failed to disconnect rows." });
   }
 }
+
+export async function reconnectProjectDeviceRows(req: Request, res: Response) {
+  const { projectId, projectDeviceId } = req.params;
+  if (typeof projectId !== "string" || typeof projectDeviceId !== "string") {
+    return res.status(400).json({ error: "Invalid parameters" });
+  }
+  const parsed = reconnectProjectDeviceRowsSchema.safeParse(req.body);
+  if (!parsed.success) {
+    return res.status(400).json({ error: parsed.error.flatten() });
+  }
+  try {
+    const preview = await projectDeviceSyncService.reconnect(projectId, projectDeviceId, parsed.data.rowIds);
+    return res.json(preview);
+  } catch (error) {
+    return res.status(400).json({ error: error instanceof Error ? error.message : "Failed to reconnect rows." });
+  }
+}
diff --git a/src/server/routes/project-device.routes.ts b/src/server/routes/project-device.routes.ts
index 97f84f2..aa06112 100644
--- a/src/server/routes/project-device.routes.ts
+++ b/src/server/routes/project-device.routes.ts
@@ -6,6 +6,8 @@ import {
   disconnectProjectDeviceRows,
   getProjectDeviceSyncPreview,
   listProjectDevicesByProject,
+  reconnectProjectDeviceRows,
+  restoreProjectDeviceRows,
   synchronizeProjectDeviceRows,
   updateProjectDevice,
 } from "../controllers/project-device.controller.js";
@@ -17,6 +19,8 @@ projectDeviceRouter.post("/projects/:projectId", createProjectDevice);
 projectDeviceRouter.post("/projects/:projectId/import-global/:globalDeviceId", copyGlobalDeviceToProject);
 projectDeviceRouter.get("/projects/:projectId/:projectDeviceId/links", getProjectDeviceSyncPreview);
 projectDeviceRouter.post("/projects/:projectId/:projectDeviceId/synchronize", synchronizeProjectDeviceRows);
+projectDeviceRouter.post("/projects/:projectId/:projectDeviceId/restore", restoreProjectDeviceRows);
 projectDeviceRouter.post("/projects/:projectId/:projectDeviceId/disconnect", disconnectProjectDeviceRows);
+projectDeviceRouter.post("/projects/:projectId/:projectDeviceId/reconnect", reconnectProjectDeviceRows);
 projectDeviceRouter.put("/projects/:projectId/:projectDeviceId", updateProjectDevice);
 projectDeviceRouter.delete("/projects/:projectId/:projectDeviceId", deleteProjectDevice);
diff --git a/src/shared/validation/project-device.schemas.ts b/src/shared/validation/project-device.schemas.ts
index 2692340..941bd71 100644
--- a/src/shared/validation/project-device.schemas.ts
+++ b/src/shared/validation/project-device.schemas.ts
@@ -28,5 +28,33 @@ export const disconnectProjectDeviceRowsSchema = z.object({
   rowIds: z.array(z.string().min(1)).min(1),
 });
 
+const projectDeviceRestoreValuesSchema = z.object({
+  name: z.string().optional(),
+  displayName: z.string().optional(),
+  phaseType: z.enum(["single_phase", "three_phase"]).optional(),
+  connectionKind: z.string().nullable().optional(),
+  costGroup: z.string().nullable().optional(),
+  category: z.string().nullable().optional(),
+  quantity: z.number().min(0).optional(),
+  powerPerUnit: z.number().min(0).optional(),
+  simultaneityFactor: z.number().min(0).max(1).optional(),
+  cosPhi: z.number().min(0).max(1).nullable().optional(),
+  remark: z.string().nullable().optional(),
+});
+
+export const restoreProjectDeviceRowsSchema = z.object({
+  rows: z
+    .array(
+      z.object({
+        rowId: z.string().min(1),
+        values: projectDeviceRestoreValuesSchema,
+        overriddenFields: z.array(z.enum(projectDeviceSyncFields)),
+      })
+    )
+    .min(1),
+});
+
+export const reconnectProjectDeviceRowsSchema = disconnectProjectDeviceRowsSchema;
+
 export type CreateProjectDeviceInput = z.infer<typeof createProjectDeviceSchema>;
 export type UpdateProjectDeviceInput = z.infer<typeof updateProjectDeviceSchema>;
diff --git a/tests/project-device-sync.service.test.ts b/tests/project-device-sync.service.test.ts
index 0bcf7de..7f6d6bf 100644
--- a/tests/project-device-sync.service.test.ts
+++ b/tests/project-device-sync.service.test.ts
@@ -1,6 +1,8 @@
 import assert from "node:assert/strict";
 import { describe, it } from "node:test";
 import { ProjectDeviceSyncService } from "../src/domain/services/project-device-sync.service.js";
+import { CircuitDeviceRowRepository } from "../src/db/repositories/circuit-device-row.repository.js";
+import { db } from "../src/db/client.js";
 
 function projectDevice() {
   return {
@@ -56,6 +58,7 @@ function linkedRow() {
 function createService() {
   const rows = [linkedRow()];
   const updates: Array<Record<string, unknown>> = [];
+  let transactionCalls = 0;
   const service = new ProjectDeviceSyncService({
     projectDeviceRepository: {
       async findById() {
@@ -64,15 +67,35 @@ function createService() {
     },
     deviceRowRepository: {
       async listLinkedByProjectDevice() {
-        return rows as never;
+        return rows.filter((row) => row.linkedProjectDeviceId === "pd1") as never;
       },
-      async update(rowId, input) {
-        updates.push({ rowId, ...input });
-        Object.assign(rows[0], input);
+      async listLinkStatesByIds() {
+        return rows.map((row) => ({ id: row.id, linkedProjectDeviceId: row.linkedProjectDeviceId })) as never;
+      },
+      updateLinkedRowsTransactional(_projectDeviceId, changes) {
+        transactionCalls += 1;
+        for (const change of changes) {
+          updates.push({ rowId: change.rowId, ...change.input });
+          Object.assign(rows.find((row) => row.id === change.rowId)!, change.input);
+        }
+      },
+      disconnectLinkedRowsTransactional(_projectDeviceId, rowIds) {
+        transactionCalls += 1;
+        for (const rowId of rowIds) {
+          const row = rows.find((entry) => entry.id === rowId)!;
+          updates.push({ rowId, linkedProjectDeviceId: undefined, displayName: row.displayName, quantity: row.quantity });
+          Object.assign(row, { linkedProjectDeviceId: null });
+        }
+      },
+      reconnectRowsTransactional(projectDeviceId, rowIds) {
+        transactionCalls += 1;
+        for (const rowId of rowIds) {
+          Object.assign(rows.find((row) => row.id === rowId)!, { linkedProjectDeviceId: projectDeviceId });
+        }
       },
     } as never,
   });
-  return { service, rows, updates };
+  return { service, rows, updates, transactionCalls: () => transactionCalls };
 }
 
 describe("project device synchronization", () => {
@@ -90,13 +113,14 @@ describe("project device synchronization", () => {
   });
 
   it("synchronizes only explicitly selected fields", async () => {
-    const { service, rows } = createService();
+    const { service, rows, transactionCalls } = createService();
     await service.synchronize("p1", "pd1", ["row1"], ["quantity", "powerPerUnit"]);
 
     assert.equal(rows[0].quantity, 6);
     assert.equal(rows[0].powerPerUnit, 0.04);
     assert.equal(rows[0].displayName, "Local display name");
     assert.deepEqual(JSON.parse(rows[0].overriddenFields ?? "[]"), ["displayName"]);
+    assert.equal(transactionCalls(), 1);
   });
 
   it("rejects rows that are not linked to the selected project device", async () => {
@@ -115,4 +139,75 @@ describe("project device synchronization", () => {
     assert.equal(updates[0].displayName, "Local display name");
     assert.equal(updates[0].quantity, 2);
   });
+
+  it("restores synchronized values and override markers", async () => {
+    const { service, rows } = createService();
+    const result = await service.synchronize("p1", "pd1", ["row1"], ["quantity", "powerPerUnit"]);
+
+    await service.restore("p1", "pd1", result.undo.rows);
+
+    assert.equal(rows[0].quantity, 2);
+    assert.equal(rows[0].powerPerUnit, 0.03);
+    assert.deepEqual(JSON.parse(rows[0].overriddenFields ?? "[]"), ["displayName", "quantity"]);
+  });
+
+  it("reconnects rows only while they remain disconnected", async () => {
+    const { service, rows } = createService();
+    const result = await service.disconnect("p1", "pd1", ["row1"]);
+
+    await service.reconnect("p1", "pd1", result.undo.rowIds);
+
+    assert.equal(rows[0].linkedProjectDeviceId, "pd1");
+  });
+
+  it("executes multi-row updates inside one synchronous transaction", () => {
+    const repository = new CircuitDeviceRowRepository();
+    const originalTransaction = (db as unknown as { transaction: unknown }).transaction;
+    let transactionCalls = 0;
+    let updateCalls = 0;
+    let returnedPromise = false;
+    (db as unknown as { transaction: (callback: (tx: unknown) => unknown) => void }).transaction = (callback) => {
+      transactionCalls += 1;
+      const fakeTx = {
+        update() {
+          return {
+            set() {
+              return {
+                where() {
+                  return {
+                    run() {
+                      updateCalls += 1;
+                      return { changes: 1 };
+                    },
+                  };
+                },
+              };
+            },
+          };
+        },
+      };
+      const result = callback(fakeTx);
+      returnedPromise = Boolean(result && typeof (result as Promise<unknown>).then === "function");
+    };
+
+    try {
+      const input = {
+        linkedProjectDeviceId: "pd1",
+        name: "Luminaire",
+        displayName: "Office lighting",
+        quantity: 1,
+        powerPerUnit: 0.1,
+        simultaneityFactor: 1,
+      };
+      repository.updateLinkedRowsTransactional("pd1", [
+        { rowId: "r1", input },
+        { rowId: "r2", input },
+      ]);
+      assert.equal(transactionCalls, 1);
+      assert.equal(updateCalls, 2);
+      assert.equal(returnedPromise, false);
+    } finally {
+      (db as unknown as { transaction: unknown }).transaction = originalTransaction;
+    }
+  });
 });