Preserve sync state after re-pairing

Signed-off-by: Zoorpha <aaron@kubedo.com>

src/main.ts

@@ -7,7 +7,7 @@ import { RustShareVaultSyncSettingTab } from './ui/settings-tab';
 import { StatusBar } from './ui/status-bar';
 import { RustShareAPI } from './api';
 import { SyncEngine } from './sync';
-import { SyncState, createEmptySyncState, migrateSyncState, pruneTombstones } from './state';
+import { SyncState, createEmptySyncState, migrateSyncState, pruneTombstones, retargetSyncStateDevice } from './state';
 import { SyncQueue, SyncOperation } from './sync-queue';
 import { syncLog } from './sync-log';
 import { detectCloudSyncFolder, shouldIgnorePath, loadDesktopAuthToken, isValidUuid } from './utils';
@@ -294,10 +294,13 @@ export default class RustShareVaultSyncPlugin extends Plugin {
       }
 
       // Initialize sync state
-      if (!this.syncState || this.syncState.vault_id !== vaultId || this.syncState.device_id !== deviceId) {
+      if (this.syncState?.vault_id === vaultId && this.syncState.device_id !== deviceId) {
+        this.syncState = retargetSyncStateDevice(this.syncState, deviceId, this.settings.deviceName);
+      } else if (!this.syncState || this.syncState.vault_id !== vaultId) {
         this.syncState = createEmptySyncState(vaultId, deviceId, this.settings.deviceName);
       }
 
+      await this.saveSettings();
       this.statusBar.updateStatus('connected');
     } catch (e) {
       this.statusBar.updateStatus('error', `Connect failed: ${e}`);

src/state.ts

@@ -34,6 +34,14 @@ export function createEmptySyncState(vaultId: string, deviceId: string, deviceNa
   };
 }
 
+export function retargetSyncStateDevice(state: SyncState, deviceId: string, deviceName: string): SyncState {
+  return {
+    ...state,
+    device_id: deviceId,
+    device_name: deviceName,
+  };
+}
+
 export function migrateSyncState(state: Record<string, unknown>): SyncState {
   const version = typeof state.version === 'number' ? state.version : 0;
   if (version === 1) {

tests/state.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { createEmptySyncState } from '../src/state';
+import { createEmptySyncState, retargetSyncStateDevice } from '../src/state';
 
 describe('createEmptySyncState', () => {
   it('returns state with correct defaults and empty files/tombstones', () => {
@@ -13,3 +13,23 @@ describe('createEmptySyncState', () => {
     expect(state.tombstones).toEqual({});
   });
 });
+
+describe('retargetSyncStateDevice', () => {
+  it('keeps vault file history when a re-paired device gets a new id', () => {
+    const state = createEmptySyncState('vault-123', 'old-device', 'Old Laptop');
+    state.last_server_rev = 7;
+    state.files['note.md'] = {
+      sha256: 'abc',
+      server_rev: 6,
+      last_synced_at: '2026-06-23T00:00:00.000Z',
+    };
+
+    const retargeted = retargetSyncStateDevice(state, 'new-device', 'New Laptop');
+
+    expect(retargeted.device_id).toBe('new-device');
+    expect(retargeted.device_name).toBe('New Laptop');
+    expect(retargeted.vault_id).toBe('vault-123');
+    expect(retargeted.last_server_rev).toBe(7);
+    expect(retargeted.files['note.md']).toEqual(state.files['note.md']);
+  });
+});