Linux: Auto migrate safeStorage backend between kwallet5 and kwallet6

app/main.main.ts

@@ -139,6 +139,7 @@ import { appRelaunch } from '../ts/util/relaunch.main.ts';
 import { getAppRootDir } from '../ts/util/appRootDir.main.ts';
 import { trackHeapSize } from '../ts/util/oomNotifier.node.ts';
 import { sendDummyKeystroke } from './WindowsNotifications.main.ts';
+import { maybeMigrateSafeStorageBackend } from '../ts/util/linuxPasswordStoreMigration.main.ts';
 
 const { chmod, realpath, writeFile } = fsExtra;
 const { get, pick, isNumber, isBoolean, some, debounce, noop } = lodash;
@@ -1892,6 +1893,17 @@ const onDatabaseInitializationError = async (error: Error) => {
     defaultButtonId = copyErrorAndQuitButtonIndex;
   } else if (error instanceof SafeStorageBackendChangeError) {
     const { currentBackend, previousBackend } = error;
+
+    // Attempt automatic migration
+    if (await maybeMigrateSafeStorageBackend(previousBackend, currentBackend)) {
+      log.info(
+        `Performed auto migration of safeStorage backend from ${previousBackend} to ${currentBackend}. Restarting.`
+      );
+      app.relaunch();
+      app.exit(1);
+      return;
+    }
+
     const previousBackendFlag = getOwn(
       LINUX_PASSWORD_STORE_FLAGS,
       previousBackend

ts/util/linuxPasswordStoreMigration.main.ts

@@ -0,0 +1,68 @@
+// Copyright 2026 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+/* oxlint-disable no-console */
+
+import { exec } from 'node:child_process';
+import { userConfig } from '../../app/user_config.main.ts';
+
+export async function maybeMigrateSafeStorageBackend(
+  previousBackend: string,
+  newBackend: string
+): Promise<boolean> {
+  if (previousBackend === 'kwallet5' && newBackend === 'kwallet6') {
+    return upgradeKWallet5To6();
+  }
+
+  if (previousBackend === 'kwallet6' && newBackend === 'kwallet5') {
+    return downgradeKWallet6To5();
+  }
+
+  return false;
+}
+
+async function upgradeKWallet5To6(): Promise<boolean> {
+  if (await checkCommandSuccess('kwalletd5 --version')) {
+    console.log(
+      'kwalletd5 --version check did not fail, so it may still be installed. Aborting upgrade.'
+    );
+    return false;
+  }
+
+  if (!(await checkCommandSuccess('kwalletd6 --version'))) {
+    console.log(
+      'kwalletd6 --version check did not succeed, so it may not be installed. Aborting upgrade'
+    );
+    return false;
+  }
+
+  userConfig.set('safeStorageBackend', 'kwallet6');
+  return true;
+}
+
+async function downgradeKWallet6To5(): Promise<boolean> {
+  if (await checkCommandSuccess('kwalletd6 --version')) {
+    console.log(
+      'kwalletd6 --version check did not fail, so it may still be installed. Aborting upgrade.'
+    );
+    return false;
+  }
+
+  if (!(await checkCommandSuccess('kwalletd5 --version'))) {
+    console.log(
+      'kwalletd5 --version check did not succeed, so it may not be installed. Aborting upgrade'
+    );
+    return false;
+  }
+
+  userConfig.set('safeStorageBackend', 'kwallet5');
+  return true;
+}
+
+function checkCommandSuccess(command: string): Promise<boolean> {
+  return new Promise(resolve => {
+    exec(command).on('exit', code => {
+      resolve(code === 0);
+    });
+  });
+}