feat(auth): add resume lane diagnostics and recovery

- add runtime-aware resume lane diagnostics and auth backup flows

- warn when account resume uses a different plain ccs continuity lane

- surface lane mismatch guidance in the accounts dashboard, docs, and tests

README.md

@@ -522,6 +522,29 @@ accounts:
 
 Shared context with `standard` depth links project workspace data. `deeper` depth links additional continuity artifacts. Credentials remain isolated per account.
 
+Resume is lane-scoped:
+
+- plain `ccs -r` resumes the lane that plain `ccs` currently uses
+- `ccs <account> -r` resumes that account's lane only
+- those lanes can differ, even when an account is `shared + deeper`
+
+If you do most of your work with plain `ccs` and want future resumes to line up with an auth account:
+
+```bash
+ccs auth default work
+```
+
+If you need to protect local continuity files before changing account sync settings:
+
+```bash
+ccs auth backup work
+ccs auth backup default
+```
+
+- `ccs auth backup work` backs up the local continuity lane for that auth account
+- `ccs auth backup default` backs up the lane plain `ccs` would use right now
+- this backs up local continuity artifacts only; Claude-hosted resume behavior still depends on upstream state
+
 #### Cross-Profile Continuity Inheritance (Claude Target)
 
 You can map non-account profiles (API, CLIProxy, Copilot, or `default`) to reuse continuity artifacts from an account profile:
@@ -532,6 +555,7 @@ continuity:
     glm: pro
     gemini: pro
     copilot: pro
+    default: pro
 ```
 
 With this config, `ccs glm`, `ccs gemini`, and `ccs copilot` run with `pro`'s `CLAUDE_CONFIG_DIR` continuity context while keeping each profile's own provider credentials/settings.

docs/session-sharing-technical-analysis.md

@@ -1,6 +1,6 @@
 # Session Sharing Technical Analysis
 
-Last Updated: 2026-02-26
+Last Updated: 2026-04-04
 
 ## Summary
 
@@ -69,6 +69,30 @@ Behavior:
 - Reuses `CLAUDE_CONFIG_DIR` from mapped account profile after normal account context policy resolution
 - Invalid/missing mapped accounts are skipped safely
 
+### Resume Lane Note
+
+Resume follows the active `CLAUDE_CONFIG_DIR`, not just the continuity group:
+
+- plain `ccs -r` resumes the lane plain `ccs` is using right now
+- `ccs <account> -r` resumes only that account lane
+- those two commands can point at different continuity inventories
+
+That means `shared + deeper` on an account does **not** automatically make old plain-`ccs` resume history appear inside `ccs <account> -r`.
+
+If you want future plain `ccs` sessions to use an account lane, either:
+
+```bash
+ccs auth default work
+```
+
+or map the default profile explicitly:
+
+```yaml
+continuity:
+  inherit_from_account:
+    default: work
+```
+
 ## User Workflows
 
 ### New account with shared context
@@ -88,6 +112,19 @@ ccs auth create backup2 --context-group sprint-a --deeper-continuity
 
 No account recreation required for this workflow.
 
+### Backup Before Changing Sync
+
+CCS can back up local continuity artifacts before you change settings:
+
+```bash
+ccs auth backup work
+ccs auth backup default
+```
+
+- `ccs auth backup work` backs up the selected account lane
+- `ccs auth backup default` backs up the lane plain `ccs` would use right now
+- this is a local continuity backup, not a guaranteed export of all upstream Claude-hosted resume state
+
 ## Current Limitations
 
 - Shared context is local filesystem sharing. It does not bypass remote provider permission models.

src/auth/auth-commands.ts

@@ -21,6 +21,7 @@ import packageJson from '../../package.json';
 import {
   type CommandContext,
   handleCreate,
+  handleBackup,
   handleList,
   handleShow,
   handleRemove,
@@ -68,6 +69,9 @@ class AuthCommands {
     console.log('');
     console.log(subheader('Commands'));
     console.log(`  ${color('create <profile>', 'command')}        Create new profile and login`);
+    console.log(
+      `  ${color('backup <profile>', 'command')}        Backup local continuity for an account`
+    );
     console.log(`  ${color('list', 'command')}                   List all saved profiles`);
     console.log(`  ${color('show <profile>', 'command')}         Show profile details`);
     console.log(`  ${color('remove <profile>', 'command')}       Remove saved profile`);
@@ -97,6 +101,12 @@ class AuthCommands {
     console.log(`  ${dim('# Set work as default')}`);
     console.log(`  ${color('ccs auth default work', 'command')}`);
     console.log('');
+    console.log(`  ${dim('# Backup the local continuity lane for an account or plain ccs')}`);
+    console.log(`  ${color('ccs auth backup work', 'command')}`);
+    console.log(
+      `  ${color('ccs auth backup default', 'command')}  ${dim('# backup plain ccs lane')}`
+    );
+    console.log('');
     console.log(`  ${dim('# Restore original CCS behavior')}`);
     console.log(`  ${color('ccs auth reset-default', 'command')}`);
     console.log('');
@@ -162,6 +172,10 @@ class AuthCommands {
     return handleCreate(this.getContext(), args);
   }
 
+  async handleBackup(args: string[]): Promise<void> {
+    return handleBackup(this.getContext(), args);
+  }
+
   /**
    * List all profiles - delegates to list-command.ts
    */
@@ -227,6 +241,10 @@ class AuthCommands {
         await this.handleList(commandArgs);
         break;
 
+      case 'backup':
+        await this.handleBackup(commandArgs);
+        break;
+
       case 'show':
         await this.handleShow(commandArgs);
         break;

src/auth/commands/backup-command.ts

@@ -0,0 +1,139 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import { initUI, color, dim, fail, info, ok } from '../../utils/ui';
+import { exitWithError } from '../../errors';
+import { ExitCode } from '../../errors/exit-codes';
+import {
+  createTimestampStamp,
+  getAuthBackupRoot,
+  getContinuityArtifactNames,
+  resolveRuntimePlainCcsResumeLane,
+} from '../resume-lane-diagnostics';
+import { isAccountContextMetadata, resolveAccountContextPolicy } from '../account-context';
+import { CommandContext, parseArgs } from './types';
+
+interface BackupManifest {
+  target: string;
+  source_config_dir: string;
+  created_at: string;
+  copied: string[];
+  skipped: string[];
+}
+
+function copyDirectoryIfPresent(sourcePath: string, targetPath: string): boolean {
+  if (!fs.existsSync(sourcePath)) {
+    return false;
+  }
+
+  fs.cpSync(sourcePath, targetPath, {
+    recursive: true,
+    dereference: true,
+    force: false,
+    errorOnExist: false,
+  });
+  return true;
+}
+
+export async function handleBackup(ctx: CommandContext, args: string[]): Promise<void> {
+  await initUI();
+  const { profileName, json } = parseArgs(args);
+
+  if (!profileName) {
+    console.log(fail('Profile name is required'));
+    console.log('');
+    console.log(`Usage: ${color('ccs auth backup <profile|default> [--json]', 'command')}`);
+    exitWithError('Profile name is required', ExitCode.PROFILE_ERROR);
+  }
+
+  try {
+    let sourceConfigDir = '';
+    let backupLabel = profileName;
+    let artifactNames: string[] = [];
+
+    if (profileName === 'default') {
+      const lane = await resolveRuntimePlainCcsResumeLane();
+      sourceConfigDir = lane.configDir;
+      backupLabel = lane.accountName ? `default-${lane.accountName}` : 'default';
+      artifactNames = getContinuityArtifactNames('default');
+    } else {
+      const profiles = ctx.registry.getAllProfilesMerged();
+      const profile = profiles[profileName];
+      if (!profile || profile.type !== 'account') {
+        exitWithError(
+          `Backup supports auth accounts or "default". Not found: ${profileName}`,
+          ExitCode.PROFILE_ERROR
+        );
+      }
+
+      const contextPolicy = resolveAccountContextPolicy(
+        isAccountContextMetadata(profile) ? profile : undefined
+      );
+      sourceConfigDir = await ctx.instanceMgr.ensureInstance(profileName, contextPolicy, {
+        bare: profile.bare === true,
+      });
+      artifactNames = getContinuityArtifactNames('account');
+    }
+
+    const backupRoot = path.join(getAuthBackupRoot(), backupLabel, createTimestampStamp());
+    fs.mkdirSync(backupRoot, { recursive: true, mode: 0o700 });
+
+    const copied: string[] = [];
+    const skipped: string[] = [];
+
+    for (const artifactName of artifactNames) {
+      const sourcePath = path.join(sourceConfigDir, artifactName);
+      const targetPath = path.join(backupRoot, artifactName);
+      if (copyDirectoryIfPresent(sourcePath, targetPath)) {
+        copied.push(artifactName);
+      } else {
+        skipped.push(artifactName);
+      }
+    }
+
+    const manifest: BackupManifest = {
+      target: profileName,
+      source_config_dir: sourceConfigDir,
+      created_at: new Date().toISOString(),
+      copied,
+      skipped,
+    };
+    fs.writeFileSync(
+      path.join(backupRoot, 'manifest.json'),
+      `${JSON.stringify(manifest, null, 2)}\n`,
+      {
+        encoding: 'utf8',
+        mode: 0o600,
+      }
+    );
+
+    if (json) {
+      console.log(
+        JSON.stringify(
+          {
+            target: profileName,
+            backup_path: backupRoot,
+            copied,
+            skipped,
+          },
+          null,
+          2
+        )
+      );
+      return;
+    }
+
+    console.log(ok(`Continuity backup created: ${backupRoot}`));
+    console.log('');
+    console.log(info(`Source lane: ${sourceConfigDir}`));
+    console.log(`  ${dim(`Copied: ${copied.length > 0 ? copied.join(', ') : 'none'}`)}`);
+    if (skipped.length > 0) {
+      console.log(`  ${dim(`Skipped: ${skipped.join(', ')}`)}`);
+    }
+    console.log('');
+  } catch (error) {
+    exitWithError(
+      `Failed to create continuity backup: ${(error as Error).message}`,
+      ExitCode.GENERAL_ERROR
+    );
+  }
+}

src/auth/commands/index.ts

@@ -16,6 +16,7 @@ export {
 
 // Command handlers
 export { handleCreate } from './create-command';
+export { handleBackup } from './backup-command';
 export { handleList } from './list-command';
 export { handleShow } from './show-command';
 export { handleRemove } from './remove-command';

src/auth/profile-continuity-inheritance.ts

@@ -100,6 +100,19 @@ function resolveMappedAccount(
   return undefined;
 }
 
+export function resolveConfiguredContinuitySourceAccount(
+  profileName: string,
+  profileType: ProfileType
+): string | undefined {
+  const inheritFromAccount = getContinuityInheritanceMap();
+  return (
+    resolveMappedAccount(profileName, profileType, inheritFromAccount) ??
+    (!isUnifiedMode()
+      ? resolveMappedAccount(profileName, profileType, loadLegacyContinuityInheritanceMap())
+      : undefined)
+  );
+}
+
 /**
  * Resolve optional cross-profile continuity inheritance.
  *
@@ -115,16 +128,10 @@ export async function resolveProfileContinuityInheritance(
     return {};
   }
 
-  const inheritFromAccount = getContinuityInheritanceMap();
+  const sourceAccount = resolveConfiguredContinuitySourceAccount(
-  const sourceAccount =
+    input.profileName,
-    resolveMappedAccount(input.profileName, input.profileType, inheritFromAccount) ??
+    input.profileType
-    (!isUnifiedMode()
+  );
-      ? resolveMappedAccount(
-          input.profileName,
-          input.profileType,
-          loadLegacyContinuityInheritanceMap()
-        )
-      : undefined);
   if (!sourceAccount) {
     return {};
   }

src/auth/profile-detector.ts

@@ -462,6 +462,14 @@ class ProfileDetector {
     };
   }
 
+  /**
+   * Public wrapper for diagnostics and tooling that need to inspect how
+   * plain `ccs` resolves without duplicating the default-profile logic.
+   */
+  resolveDefaultProfileResult(): ProfileDetectionResult {
+    return this.resolveDefaultProfile();
+  }
+
   /**
    * List available profiles (for error messages)
    */

src/auth/resume-lane-diagnostics.ts

@@ -0,0 +1,163 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import { getDefaultClaudeConfigDir } from '../utils/claude-config-path';
+import { getCcsDir } from '../utils/config-manager';
+import InstanceManager from '../management/instance-manager';
+import ProfileDetector from './profile-detector';
+import { resolveConfiguredContinuitySourceAccount } from './profile-continuity-inheritance';
+import type { ProfileType } from '../types/profile';
+
+export type ResumeLaneKind =
+  | 'native'
+  | 'account-default'
+  | 'account-inherited'
+  | 'profile-default'
+  | 'ambient';
+
+export interface ResumeLaneSummary {
+  kind: ResumeLaneKind;
+  label: string;
+  configDir: string;
+  accountName?: string;
+  profileName?: string;
+  projectCount: number;
+}
+
+export interface ResumeFlagIntent {
+  implicit: boolean;
+  explicitSessionId?: string;
+}
+
+function countTopLevelProjectDirs(projectsDir: string): number {
+  try {
+    return fs
+      .readdirSync(projectsDir, { withFileTypes: true })
+      .filter((entry) => entry.isDirectory()).length;
+  } catch {
+    return 0;
+  }
+}
+
+function resolveNativeLaneSummary(
+  kind: ResumeLaneKind = 'native',
+  profileName?: string
+): ResumeLaneSummary {
+  const configDir = getDefaultClaudeConfigDir();
+  const label =
+    kind === 'profile-default' && profileName
+      ? `profile "${profileName}" via native Claude lane`
+      : 'native Claude lane';
+
+  return {
+    kind,
+    label,
+    configDir,
+    profileName,
+    projectCount: countTopLevelProjectDirs(path.join(configDir, 'projects')),
+  };
+}
+
+function resolveAccountLaneSummary(
+  kind: Extract<ResumeLaneKind, 'account-default' | 'account-inherited'>,
+  accountName: string
+): ResumeLaneSummary {
+  const instanceMgr = new InstanceManager();
+  const configDir = instanceMgr.getInstancePath(accountName);
+
+  return {
+    kind,
+    label:
+      kind === 'account-inherited'
+        ? `plain ccs inherits from account "${accountName}"`
+        : `plain ccs defaults to account "${accountName}"`,
+    configDir,
+    accountName,
+    projectCount: countTopLevelProjectDirs(path.join(configDir, 'projects')),
+  };
+}
+
+export async function resolveConfiguredPlainCcsResumeLane(): Promise<ResumeLaneSummary> {
+  const detector = new ProfileDetector();
+  const defaultProfile = detector.resolveDefaultProfileResult();
+
+  if (defaultProfile.type === 'account') {
+    return resolveAccountLaneSummary('account-default', defaultProfile.name);
+  }
+
+  const inheritedAccount = resolveConfiguredContinuitySourceAccount(
+    defaultProfile.name,
+    defaultProfile.type
+  );
+  if (inheritedAccount) {
+    return resolveAccountLaneSummary('account-inherited', inheritedAccount);
+  }
+
+  if (defaultProfile.type !== 'default') {
+    return resolveNativeLaneSummary('profile-default', defaultProfile.name);
+  }
+
+  return resolveNativeLaneSummary();
+}
+
+export async function resolveRuntimePlainCcsResumeLane(): Promise<ResumeLaneSummary> {
+  if (process.env.CLAUDE_CONFIG_DIR) {
+    const configDir = path.resolve(process.env.CLAUDE_CONFIG_DIR);
+    return {
+      kind: 'ambient',
+      label: 'current shell CLAUDE_CONFIG_DIR',
+      configDir,
+      projectCount: countTopLevelProjectDirs(path.join(configDir, 'projects')),
+    };
+  }
+
+  return resolveConfiguredPlainCcsResumeLane();
+}
+
+export function parseResumeFlagIntent(args: string[]): ResumeFlagIntent | null {
+  for (let index = 0; index < args.length; index += 1) {
+    const arg = args[index];
+    if (arg === '-r') {
+      return { implicit: true };
+    }
+
+    if (arg === '--resume') {
+      const next = args[index + 1];
+      if (next && !next.startsWith('-')) {
+        return { implicit: false, explicitSessionId: next };
+      }
+      return { implicit: true };
+    }
+
+    if (arg.startsWith('--resume=')) {
+      const sessionId = arg.slice('--resume='.length).trim();
+      return sessionId ? { implicit: false, explicitSessionId: sessionId } : { implicit: true };
+    }
+  }
+
+  return null;
+}
+
+export function getAuthBackupRoot(): string {
+  return path.join(getCcsDir(), 'backups', 'auth-continuity');
+}
+
+export function createTimestampStamp(date = new Date()): string {
+  const yyyy = date.getFullYear();
+  const mm = String(date.getMonth() + 1).padStart(2, '0');
+  const dd = String(date.getDate()).padStart(2, '0');
+  const hh = String(date.getHours()).padStart(2, '0');
+  const min = String(date.getMinutes()).padStart(2, '0');
+  const ss = String(date.getSeconds()).padStart(2, '0');
+  return `${yyyy}${mm}${dd}_${hh}${min}${ss}`;
+}
+
+export function getContinuityArtifactNames(profileType: ProfileType): string[] {
+  const sharedItems = ['projects'];
+  const deeperItems = ['session-env', 'file-history', 'shell-snapshots', 'todos'];
+
+  if (profileType === 'default' || profileType === 'account') {
+    return [...sharedItems, ...deeperItems];
+  }
+
+  return sharedItems;
+}

src/ccs.ts

@@ -1,6 +1,7 @@
 import './utils/fetch-proxy-setup';
 
 import * as fs from 'fs';
+import * as path from 'path';
 import { detectClaudeCli } from './utils/claude-detector';
 import {
   getSettingsPath,
@@ -64,6 +65,10 @@ import { tryHandleRootCommand } from './commands/root-command-router';
 // Import extracted utility functions
 import { execClaude } from './utils/shell-executor';
 import { isDeprecatedGlmtProfileName, normalizeDeprecatedGlmtEnv } from './utils/glmt-deprecation';
+import {
+  parseResumeFlagIntent,
+  resolveRuntimePlainCcsResumeLane,
+} from './auth/resume-lane-diagnostics';
 
 // Import target adapter system
 import {
@@ -259,6 +264,43 @@ function shouldPassthroughNativeCodexFlagCommand(args: string[]): boolean {
   return getNativeCodexPassthroughArgs(args) !== null;
 }
 
+async function maybeWarnAboutResumeLaneMismatch(
+  profileName: string,
+  accountConfigDir: string,
+  args: string[]
+): Promise<void> {
+  const resumeIntent = parseResumeFlagIntent(args);
+  if (!resumeIntent) {
+    return;
+  }
+
+  const plainLane = await resolveRuntimePlainCcsResumeLane();
+  if (path.resolve(plainLane.configDir) === path.resolve(accountConfigDir)) {
+    return;
+  }
+
+  console.error(
+    warn(
+      `Resume for account "${profileName}" will search that account lane, not the current plain ccs lane.`
+    )
+  );
+  console.error(info(`  Account lane: ${accountConfigDir}`));
+  console.error(info(`  Plain ccs lane: ${plainLane.label} (${plainLane.configDir})`));
+  if (resumeIntent.explicitSessionId) {
+    console.error(
+      info(
+        `  This explicit session ID may have been created in a different lane, so Claude may not find it here.`
+      )
+    );
+  }
+  console.error(info(`  Recover the original lane first: ccs -r`));
+  console.error(info(`  Back it up before changing setup: ccs auth backup default`));
+  console.error(
+    info(`  For future work, align plain ccs with this account: ccs auth default ${profileName}`)
+  );
+  console.error('');
+}
+
 function getNativeCodexPassthroughArgs(args: string[]): string[] | null {
   const targetArgs = stripTargetFlag(args);
   if (resolveTargetType(args) !== 'codex' || targetArgs.length === 0) {
@@ -1269,6 +1311,7 @@ async function main(): Promise<void> {
         CCS_WEBSEARCH_SKIP: '1',
         CCS_IMAGE_ANALYSIS_SKIP: '1',
       };
+      await maybeWarnAboutResumeLaneMismatch(profileInfo.name, instancePath, remainingArgs);
       const launchArgs = resolveNativeClaudeLaunchArgs(remainingArgs, 'account', instancePath);
       execClaude(claudeCli, launchArgs, envVars);
     } else {

src/commands/command-catalog.ts

@@ -215,6 +215,7 @@ export const ROOT_COMMAND_FLAGS = [
 ] as const;
 export const AUTH_SUBCOMMANDS = [
   'create',
+  'backup',
   'list',
   'show',
   'remove',

src/commands/completion-backend.ts

@@ -94,6 +94,8 @@ function getSuggestionsForCommand(tokensBeforeCurrent: string[]): CompletionSugg
       return completeSubcommands(ROOT_HELP_TOPICS.map((topic) => topic.name));
     case 'auth':
       if (!subcommand) return completeSubcommands(AUTH_SUBCOMMANDS);
+      if (subcommand === 'backup')
+        return completeSubcommands(['default', ...getProfileNames('accounts')], ['--json']);
       if (subcommand === 'show')
         return completeSubcommands(getProfileNames('accounts'), ['--json']);
       if (subcommand === 'remove')

src/web-server/routes/account-routes.ts

@@ -32,6 +32,7 @@ import {
   type MergedAccountEntry,
 } from './account-route-helpers';
 import type { AccountConfig } from '../../config/unified-config-types';
+import { resolveConfiguredPlainCcsResumeLane } from '../../auth/resume-lane-diagnostics';
 
 const router = Router();
 
@@ -59,7 +60,7 @@ function hasAuthAccount(name: string): boolean {
 /**
  * GET /api/accounts - List accounts from both profiles.json and config.yaml
  */
-router.get('/', (_req: Request, res: Response): void => {
+router.get('/', async (_req: Request, res: Response): Promise<void> => {
   try {
     const registry = createProfileRegistry();
 
@@ -147,8 +148,19 @@ router.get('/', (_req: Request, res: Response): void => {
 
     // Get default from unified config first, fallback to legacy
     const defaultProfile = registry.getDefaultUnified() ?? registry.getDefaultProfile() ?? null;
+    const plainCcsLane = await resolveConfiguredPlainCcsResumeLane();
 
-    res.json({ accounts, default: defaultProfile });
+    res.json({
+      accounts,
+      default: defaultProfile,
+      plain_ccs_lane: {
+        kind: plainCcsLane.kind,
+        label: plainCcsLane.label,
+        account_name: plainCcsLane.accountName ?? null,
+        profile_name: plainCcsLane.profileName ?? null,
+        project_count: plainCcsLane.projectCount,
+      },
+    });
   } catch (error) {
     res.status(500).json({ error: (error as Error).message });
   }

tests/unit/auth/backup-command.test.ts

@@ -0,0 +1,99 @@
+import { afterEach, beforeEach, describe, expect, it, spyOn } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import ProfileRegistry from '../../../src/auth/profile-registry';
+import { InstanceManager } from '../../../src/management/instance-manager';
+import { handleBackup } from '../../../src/auth/commands/backup-command';
+
+describe('auth backup command', () => {
+  let tempHome = '';
+  let originalCcsHome: string | undefined;
+  let originalUnified: string | undefined;
+
+  beforeEach(() => {
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-auth-backup-'));
+    originalCcsHome = process.env.CCS_HOME;
+    originalUnified = process.env.CCS_UNIFIED_CONFIG;
+    process.env.CCS_HOME = tempHome;
+    process.env.CCS_UNIFIED_CONFIG = '1';
+  });
+
+  afterEach(() => {
+    if (originalCcsHome !== undefined) process.env.CCS_HOME = originalCcsHome;
+    else delete process.env.CCS_HOME;
+
+    if (originalUnified !== undefined) process.env.CCS_UNIFIED_CONFIG = originalUnified;
+    else delete process.env.CCS_UNIFIED_CONFIG;
+
+    if (tempHome && fs.existsSync(tempHome)) {
+      fs.rmSync(tempHome, { recursive: true, force: true });
+    }
+  });
+
+  function writeConfig(): void {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 12',
+        'accounts:',
+        '  work:',
+        '    created: "2026-04-04T00:00:00.000Z"',
+        '    context_mode: shared',
+        '    context_group: default',
+        '    continuity_mode: deeper',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+  }
+
+  it('creates a JSON backup for an auth account continuity lane', async () => {
+    writeConfig();
+    const instanceMgr = new InstanceManager();
+    const registry = new ProfileRegistry();
+    const instancePath = await instanceMgr.ensureInstance('work', {
+      mode: 'shared',
+      group: 'default',
+      continuityMode: 'deeper',
+    });
+
+    fs.mkdirSync(path.join(instancePath, 'projects', 'demo-project'), { recursive: true });
+    fs.writeFileSync(
+      path.join(instancePath, 'projects', 'demo-project', 'history.jsonl'),
+      '{}\n',
+      'utf8'
+    );
+    fs.writeFileSync(path.join(instancePath, 'todos', 'todo.md'), '- keep this\n', 'utf8');
+
+    const consoleSpy = spyOn(console, 'log').mockImplementation(() => {});
+    try {
+      await handleBackup(
+        {
+          registry,
+          instanceMgr,
+          version: 'test',
+        },
+        ['work', '--json']
+      );
+    } finally {
+      consoleSpy.mockRestore();
+    }
+
+    const backupBase = path.join(tempHome, '.ccs', 'backups', 'auth-continuity', 'work');
+    const [latestBackupDir] = fs.readdirSync(backupBase).sort().reverse();
+    expect(latestBackupDir).toBeTruthy();
+    const backupPath = path.join(backupBase, latestBackupDir as string);
+    expect(fs.existsSync(path.join(backupPath, 'manifest.json'))).toBe(true);
+    expect(
+      fs.existsSync(path.join(backupPath, 'projects', 'demo-project', 'history.jsonl'))
+    ).toBe(true);
+    expect(fs.existsSync(path.join(backupPath, 'todos', 'todo.md'))).toBe(true);
+  });
+});

tests/unit/auth/resume-lane-diagnostics.test.ts

@@ -0,0 +1,143 @@
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import {
+  parseResumeFlagIntent,
+  resolveConfiguredPlainCcsResumeLane,
+} from '../../../src/auth/resume-lane-diagnostics';
+
+describe('resume lane diagnostics', () => {
+  let tempHome = '';
+  let originalCcsHome: string | undefined;
+  let originalUnified: string | undefined;
+
+  beforeEach(() => {
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-resume-lane-'));
+    originalCcsHome = process.env.CCS_HOME;
+    originalUnified = process.env.CCS_UNIFIED_CONFIG;
+    process.env.CCS_HOME = tempHome;
+    process.env.CCS_UNIFIED_CONFIG = '1';
+  });
+
+  afterEach(() => {
+    if (originalCcsHome !== undefined) process.env.CCS_HOME = originalCcsHome;
+    else delete process.env.CCS_HOME;
+
+    if (originalUnified !== undefined) process.env.CCS_UNIFIED_CONFIG = originalUnified;
+    else delete process.env.CCS_UNIFIED_CONFIG;
+
+    if (tempHome && fs.existsSync(tempHome)) {
+      fs.rmSync(tempHome, { recursive: true, force: true });
+    }
+  });
+
+  function writeConfig(lines: string[]): void {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    fs.writeFileSync(path.join(ccsDir, 'config.yaml'), `${lines.join('\n')}\n`, 'utf8');
+  }
+
+  it('parses implicit and explicit resume flags', () => {
+    expect(parseResumeFlagIntent(['-r'])).toEqual({ implicit: true });
+    expect(parseResumeFlagIntent(['--resume'])).toEqual({ implicit: true });
+    expect(parseResumeFlagIntent(['--resume', 'abc123'])).toEqual({
+      implicit: false,
+      explicitSessionId: 'abc123',
+    });
+    expect(parseResumeFlagIntent(['--resume=xyz'])).toEqual({
+      implicit: false,
+      explicitSessionId: 'xyz',
+    });
+    expect(parseResumeFlagIntent(['hello'])).toBeNull();
+  });
+
+  it('defaults to the native lane when no account/default mapping exists', async () => {
+    writeConfig([
+      'version: 12',
+      'accounts: {}',
+      'profiles: {}',
+      'cliproxy:',
+      '  oauth_accounts: {}',
+      '  providers: {}',
+      '  variants: {}',
+    ]);
+
+    const lane = await resolveConfiguredPlainCcsResumeLane();
+    expect(lane.kind).toBe('native');
+    expect(lane.configDir).toBe(path.join(tempHome, '.claude'));
+  });
+
+  it('resolves the plain ccs lane to a default account when configured', async () => {
+    writeConfig([
+      'version: 12',
+      'default: work',
+      'accounts:',
+      '  work:',
+      '    created: "2026-04-04T00:00:00.000Z"',
+      '    context_mode: shared',
+      '    context_group: default',
+      '    continuity_mode: deeper',
+      'profiles: {}',
+      'cliproxy:',
+      '  oauth_accounts: {}',
+      '  providers: {}',
+      '  variants: {}',
+    ]);
+
+    const lane = await resolveConfiguredPlainCcsResumeLane();
+    expect(lane.kind).toBe('account-default');
+    expect(lane.accountName).toBe('work');
+    expect(lane.configDir).toBe(path.join(tempHome, '.ccs', 'instances', 'work'));
+  });
+
+  it('resolves the plain ccs lane to inherited account continuity when configured', async () => {
+    writeConfig([
+      'version: 12',
+      'accounts:',
+      '  work:',
+      '    created: "2026-04-04T00:00:00.000Z"',
+      '    context_mode: shared',
+      '    context_group: default',
+      '    continuity_mode: deeper',
+      'profiles: {}',
+      'continuity:',
+      '  inherit_from_account:',
+      '    default: work',
+      'cliproxy:',
+      '  oauth_accounts: {}',
+      '  providers: {}',
+      '  variants: {}',
+    ]);
+
+    const lane = await resolveConfiguredPlainCcsResumeLane();
+    expect(lane.kind).toBe('account-inherited');
+    expect(lane.accountName).toBe('work');
+    expect(lane.configDir).toBe(path.join(tempHome, '.ccs', 'instances', 'work'));
+  });
+
+  it('resolves a non-account default profile through continuity inheritance', async () => {
+    writeConfig([
+      'version: 12',
+      'default: glm',
+      'accounts:',
+      '  work:',
+      '    created: "2026-04-04T00:00:00.000Z"',
+      'profiles:',
+      '  glm:',
+      '    type: api',
+      '    settings: ~/.ccs/glm.settings.json',
+      'continuity:',
+      '  inherit_from_account:',
+      '    glm: work',
+      'cliproxy:',
+      '  oauth_accounts: {}',
+      '  providers: {}',
+      '  variants: {}',
+    ]);
+
+    const lane = await resolveConfiguredPlainCcsResumeLane();
+    expect(lane.kind).toBe('account-inherited');
+    expect(lane.accountName).toBe('work');
+  });
+});

tests/unit/commands/completion-backend.test.ts

@@ -15,7 +15,9 @@ function suggestionValues(
   current = '',
   shell: 'bash' | 'fish' | 'powershell' | 'zsh' = 'bash'
 ): string[] {
-  return getCompletionSuggestions({ tokensBeforeCurrent, current, shell }).map((entry) => entry.value);
+  return getCompletionSuggestions({ tokensBeforeCurrent, current, shell }).map(
+    (entry) => entry.value
+  );
 }
 
 beforeEach(() => {
@@ -100,7 +102,9 @@ describe('completion backend', () => {
 
   test('suggests lifecycle subcommands for api', () => {
     const values = suggestionValues(['api']);
-    expect(values).toEqual(expect.arrayContaining(['create', 'discover', 'copy', 'export', 'import', 'remove']));
+    expect(values).toEqual(
+      expect.arrayContaining(['create', 'discover', 'copy', 'export', 'import', 'remove'])
+    );
   });
 
   test('suggests account profiles for auth show', () => {
@@ -109,6 +113,13 @@ describe('completion backend', () => {
     expect(values).toContain('--json');
   });
 
+  test('suggests default lane and account profiles for auth backup', () => {
+    const values = suggestionValues(['auth', 'backup']);
+    expect(values).toContain('default');
+    expect(values).toContain('work');
+    expect(values).toContain('--json');
+  });
+
   test('suggests cliproxy variants for variant-scoped commands', () => {
     const values = suggestionValues(['cliproxy', 'edit']);
     expect(values).toContain('my-codex');
@@ -116,7 +127,9 @@ describe('completion backend', () => {
 
   test('suggests env format values after the format flag', () => {
     const values = suggestionValues(['env', '--format']);
-    expect(values).toEqual(expect.arrayContaining(['openai', 'anthropic', 'raw', 'claude-extension']));
+    expect(values).toEqual(
+      expect.arrayContaining(['openai', 'anthropic', 'raw', 'claude-extension'])
+    );
   });
 
   test('includes live doctor and cliproxy flags from the shared catalog', () => {

tests/unit/web-server/account-routes-context.test.ts

@@ -164,6 +164,104 @@ describe('web-server account-routes context normalization', () => {
     expect(work?.continuity_inferred).toBe(true);
   });
 
+  it('reports the plain ccs lane as native when no account default or inheritance exists', async () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 12',
+        'accounts:',
+        '  work:',
+        '    created: "2026-02-01T00:00:00.000Z"',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const payload = await getJson<{
+      plain_ccs_lane?: {
+        kind: string;
+        account_name?: string | null;
+      };
+    }>(baseUrl, '/api/accounts');
+
+    expect(payload.plain_ccs_lane?.kind).toBe('native');
+    expect(payload.plain_ccs_lane?.account_name).toBeNull();
+  });
+
+  it('reports the plain ccs lane as an account when default profile is an auth account', async () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 12',
+        'default: work',
+        'accounts:',
+        '  work:',
+        '    created: "2026-02-01T00:00:00.000Z"',
+        '    context_mode: shared',
+        '    context_group: default',
+        '    continuity_mode: deeper',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const payload = await getJson<{
+      plain_ccs_lane?: {
+        kind: string;
+        account_name?: string | null;
+      };
+    }>(baseUrl, '/api/accounts');
+
+    expect(payload.plain_ccs_lane?.kind).toBe('account-default');
+    expect(payload.plain_ccs_lane?.account_name).toBe('work');
+  });
+
+  it('does not initialize an account instance as a side effect of listing accounts', async () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    fs.writeFileSync(
+      path.join(ccsDir, 'config.yaml'),
+      [
+        'version: 12',
+        'default: work',
+        'accounts:',
+        '  work:',
+        '    created: "2026-02-01T00:00:00.000Z"',
+        '    context_mode: shared',
+        '    context_group: default',
+        '    continuity_mode: deeper',
+        'profiles: {}',
+        'cliproxy:',
+        '  oauth_accounts: {}',
+        '  providers: {}',
+        '  variants: {}',
+      ].join('\n'),
+      'utf8'
+    );
+
+    const instancePath = path.join(ccsDir, 'instances', 'work');
+    expect(fs.existsSync(instancePath)).toBe(false);
+
+    await getJson(baseUrl, '/api/accounts');
+
+    expect(fs.existsSync(instancePath)).toBe(false);
+  });
+
   it('does not delete metadata when instance deletion fails', async () => {
     const ccsDir = path.join(tempHome, '.ccs');
     fs.mkdirSync(ccsDir, { recursive: true });

ui/src/components/account/accounts-table.tsx

@@ -35,14 +35,21 @@ import {
   useUpdateAccountContext,
 } from '@/hooks/use-accounts';
 import type { AuthAccountRow, SharedGroupSummary } from '@/lib/account-continuity';
+import type { PlainCcsLane } from '@/lib/api-client';
 
 interface AccountsTableProps {
   data: AuthAccountRow[];
   defaultAccount: string | null;
   groupSummaries: SharedGroupSummary[];
+  plainCcsLane: PlainCcsLane | null;
 }
 
-export function AccountsTable({ data, defaultAccount, groupSummaries }: AccountsTableProps) {
+export function AccountsTable({
+  data,
+  defaultAccount,
+  groupSummaries,
+  plainCcsLane,
+}: AccountsTableProps) {
   const { t } = useTranslation();
   const setDefaultMutation = useSetDefaultAccount();
   const deleteMutation = useDeleteAccount();
@@ -114,7 +121,7 @@ export function AccountsTable({ data, defaultAccount, groupSummaries }: Accounts
                   variant="outline"
                   className={`font-mono text-[10px] uppercase px-1.5 py-0 border ${isDeeper ? 'text-indigo-700 border-indigo-300/60 bg-indigo-50/50 dark:text-indigo-300 dark:border-indigo-900/40 dark:bg-indigo-900/20' : 'text-emerald-700 border-emerald-300/60 bg-emerald-50/50 dark:text-emerald-300 dark:border-emerald-900/40 dark:bg-emerald-900/20'}`}
                 >
-                  {isDeeper ? 'Deeper' : 'Shared'}
+                  {isDeeper ? t('accountsTable.badges.deeper') : t('accountsTable.badges.shared')}
                 </Badge>
                 <span className="text-xs font-semibold text-foreground/80">{group}</span>
               </div>
@@ -136,7 +143,7 @@ export function AccountsTable({ data, defaultAccount, groupSummaries }: Accounts
                 variant="outline"
                 className="text-amber-700 border-amber-300/60 bg-amber-50/50 dark:text-amber-400 dark:border-amber-900/40 dark:bg-amber-900/20 font-mono text-[10px] uppercase px-1.5 py-0"
               >
-                Legacy
+                {t('accountsTable.badges.legacy')}
               </Badge>
               <p className="text-[10px] text-amber-700/80 dark:text-amber-400/80 whitespace-nowrap">
                 {t('accountsTable.legacyReview')}
@@ -151,7 +158,7 @@ export function AccountsTable({ data, defaultAccount, groupSummaries }: Accounts
               variant="secondary"
               className="font-mono text-[10px] uppercase px-1.5 py-0 text-muted-foreground bg-muted/60 border-transparent shadow-none"
             >
-              Isolated
+              {t('accountsTable.badges.isolated')}
             </Badge>
           </div>
         );
@@ -321,6 +328,7 @@ export function AccountsTable({ data, defaultAccount, groupSummaries }: Accounts
         <EditAccountContextDialog
           account={contextTarget}
           groupSummaries={groupSummaries}
+          plainCcsLane={plainCcsLane}
           onClose={() => setContextTarget(null)}
         />
       )}

ui/src/components/account/continuity-overview.tsx

@@ -12,10 +12,13 @@ import { useTranslation } from 'react-i18next';
 import { Badge } from '@/components/ui/badge';
 import { Button } from '@/components/ui/button';
 import { Card, CardContent } from '@/components/ui/card';
+import { CopyButton } from '@/components/ui/copy-button';
 import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
+import type { PlainCcsLane } from '@/lib/api-client';
 
 interface ContinuityOverviewProps {
   totalAccounts: number;
+  primaryAccountName?: string | null;
   isolatedCount: number;
   sharedStandardCount: number;
   deeperSharedCount: number;
@@ -27,6 +30,7 @@ interface ContinuityOverviewProps {
   deeperReadyGroups: string[];
   legacyTargetCount: number;
   cliproxyCount: number;
+  plainCcsLane: PlainCcsLane | null;
 }
 
 type ReadinessState =
@@ -45,6 +49,7 @@ const InfoTooltip = ({ titleKey, descKey }: { titleKey: string; descKey: string
         <Button
           variant="ghost"
           size="icon"
+          aria-label={t(titleKey)}
           className="h-5 w-5 rounded-full hover:bg-muted text-muted-foreground/70 transition-colors"
         >
           <Info className="h-3 w-3" />
@@ -64,6 +69,7 @@ const InfoTooltip = ({ titleKey, descKey }: { titleKey: string; descKey: string
 
 export function ContinuityOverview({
   totalAccounts,
+  primaryAccountName,
   isolatedCount,
   sharedStandardCount,
   deeperSharedCount,
@@ -74,8 +80,26 @@ export function ContinuityOverview({
   deeperReadyGroups,
   legacyTargetCount,
   cliproxyCount,
+  plainCcsLane,
 }: ContinuityOverviewProps) {
   const { t } = useTranslation();
+  const laneLabel = plainCcsLane
+    ? plainCcsLane.kind === 'native'
+      ? t('continuityOverview.lane.native')
+      : plainCcsLane.kind === 'account-default'
+        ? t('continuityOverview.lane.accountDefault', {
+            name: plainCcsLane.account_name || '',
+          })
+        : plainCcsLane.kind === 'account-inherited'
+          ? t('continuityOverview.lane.accountInherited', {
+              name: plainCcsLane.account_name || '',
+            })
+          : plainCcsLane.kind === 'profile-default'
+            ? t('continuityOverview.lane.profileDefault', {
+                name: plainCcsLane.profile_name || 'default',
+              })
+            : plainCcsLane.label
+    : '';
 
   const readiness: ReadinessState =
     totalAccounts < 2
@@ -110,6 +134,11 @@ export function ContinuityOverview({
   };
 
   const currentIcon = iconMap[readiness];
+  const plainLaneUsesPrimaryAccount =
+    !!primaryAccountName && plainCcsLane?.account_name === primaryAccountName;
+  const showPlainLaneRecovery =
+    totalAccounts > 0 && !!plainCcsLane && (!primaryAccountName || !plainLaneUsesPrimaryAccount);
+  const showSharedRecoverySteps = totalAccounts > 1 && readiness !== 'ready';
 
   return (
     <div className="flex flex-col gap-4">
@@ -167,7 +196,7 @@ export function ContinuityOverview({
                 variant="secondary"
                 className="font-mono text-[11px] px-2 bg-muted/50 text-muted-foreground border-transparent"
               >
-                Recommend: {highlightGroup}
+                {t('continuityOverview.recommendBadge', { group: highlightGroup })}
               </Badge>
             )}
             {hasMixedState && (
@@ -175,13 +204,70 @@ export function ContinuityOverview({
                 variant="secondary"
                 className="font-mono text-[11px] px-2 bg-muted/50 text-muted-foreground border-transparent"
               >
-                Partial sync ({highlightGroup})
+                {t('continuityOverview.partialBadge', { group: highlightGroup })}
               </Badge>
             )}
           </div>
         </CardContent>
       </Card>
 
+      {(showPlainLaneRecovery || showSharedRecoverySteps) && (
+        <Card className="border-dashed">
+          <CardContent className="p-5 space-y-4">
+            {showPlainLaneRecovery && (
+              <div className="space-y-3">
+                <div>
+                  <p className="text-sm font-semibold text-foreground">
+                    {t('continuityOverview.plainLaneTitle')}
+                  </p>
+                  <p className="text-sm text-muted-foreground">
+                    {t('continuityOverview.plainLaneDescription', {
+                      lane: laneLabel || 'plain ccs',
+                    })}
+                  </p>
+                </div>
+                <div className="space-y-2">
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">ccs -r</span>
+                    <CopyButton value="ccs -r" size="icon" />
+                  </div>
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">ccs auth backup default</span>
+                    <CopyButton value="ccs auth backup default" size="icon" />
+                  </div>
+                  {primaryAccountName ? (
+                    <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                      <span className="flex-1 break-all">
+                        {`ccs auth default ${primaryAccountName}`}
+                      </span>
+                      <CopyButton value={`ccs auth default ${primaryAccountName}`} size="icon" />
+                    </div>
+                  ) : (
+                    <p className="text-xs text-muted-foreground">
+                      {t('continuityOverview.setDefaultHint')}
+                    </p>
+                  )}
+                </div>
+              </div>
+            )}
+
+            {showSharedRecoverySteps && (
+              <div className="space-y-2">
+                <p className="text-sm font-semibold text-foreground">
+                  {t('continuityReadiness.stepsTitle')}
+                </p>
+                <ol className="space-y-1 pl-5 text-sm text-muted-foreground">
+                  <li>{t('continuityReadiness.steps.syncBoth')}</li>
+                  <li>{t('continuityReadiness.steps.sameGroup', { group: highlightGroup })}</li>
+                  <li>{t('continuityReadiness.steps.enableDeeper')}</li>
+                  <li>{t('continuityReadiness.steps.resumeOriginal')}</li>
+                </ol>
+              </div>
+            )}
+          </CardContent>
+        </Card>
+      )}
+
       {/* Horizontal Progression Chain */}
       <div className="flex flex-col md:flex-row items-center gap-3">
         <div className="flex-1 w-full flex items-center justify-between p-3.5 rounded-xl border border-blue-300/40 bg-blue-50/50 dark:border-blue-900/30 dark:bg-blue-900/10 shadow-sm transition-colors hover:bg-blue-100/40 dark:hover:bg-blue-900/20">

ui/src/components/account/edit-account-context-dialog.tsx

@@ -1,4 +1,4 @@
-import { useMemo, useState } from 'react';
+import { useMemo, useState, type KeyboardEvent } from 'react';
 import {
   Dialog,
   DialogContent,
@@ -14,7 +14,9 @@ import { Label } from '@/components/ui/label';
 import { Unlink, Link2, Waves, ShieldAlert, Info } from 'lucide-react';
 import { useTranslation } from 'react-i18next';
 import type { AuthAccountRow, SharedGroupSummary } from '@/lib/account-continuity';
+import type { PlainCcsLane } from '@/lib/api-client';
 import { useUpdateAccountContext } from '@/hooks/use-accounts';
+import { CopyButton } from '@/components/ui/copy-button';
 
 type ContextMode = 'isolated' | 'shared';
 type ContinuityMode = 'standard' | 'deeper';
@@ -25,12 +27,14 @@ const CONTEXT_GROUP_PATTERN = /^[a-zA-Z][a-zA-Z0-9_-]*$/;
 interface EditAccountContextDialogProps {
   account: AuthAccountRow;
   groupSummaries: SharedGroupSummary[];
+  plainCcsLane: PlainCcsLane | null;
   onClose: () => void;
 }
 
 export function EditAccountContextDialog({
   account,
   groupSummaries,
+  plainCcsLane,
   onClose,
 }: EditAccountContextDialogProps) {
   const { t } = useTranslation();
@@ -73,6 +77,43 @@ export function EditAccountContextDialog({
           0
         )
       : 0;
+  const plainLaneUsesThisAccount = plainCcsLane?.account_name === account.name;
+  const showPlainLaneMismatch = !!plainCcsLane && !plainLaneUsesThisAccount;
+  const defaultCommand = `ccs auth default ${account.name}`;
+  const accountBackupCommand = `ccs auth backup ${account.name}`;
+  const handleRadioKeyDown = <T extends string>(
+    event: KeyboardEvent<HTMLButtonElement>,
+    current: T,
+    values: readonly T[],
+    setValue: (value: T) => void
+  ) => {
+    if (!['ArrowLeft', 'ArrowRight', 'ArrowUp', 'ArrowDown'].includes(event.key)) {
+      return;
+    }
+
+    event.preventDefault();
+    const currentIndex = values.indexOf(current);
+    const direction = event.key === 'ArrowLeft' || event.key === 'ArrowUp' ? -1 : 1;
+    const nextIndex = (currentIndex + direction + values.length) % values.length;
+    setValue(values[nextIndex] as T);
+  };
+  const laneLabel = plainCcsLane
+    ? plainCcsLane.kind === 'native'
+      ? t('continuityOverview.lane.native')
+      : plainCcsLane.kind === 'account-default'
+        ? t('continuityOverview.lane.accountDefault', {
+            name: plainCcsLane.account_name || '',
+          })
+        : plainCcsLane.kind === 'account-inherited'
+          ? t('continuityOverview.lane.accountInherited', {
+              name: plainCcsLane.account_name || '',
+            })
+          : plainCcsLane.kind === 'profile-default'
+            ? t('continuityOverview.lane.profileDefault', {
+                name: plainCcsLane.profile_name || 'default',
+              })
+            : plainCcsLane.label
+    : '';
 
   const handleSave = () => {
     if (!canSubmit) {
@@ -124,7 +165,11 @@ export function EditAccountContextDialog({
                 type="button"
                 role="radio"
                 aria-checked={mode === 'isolated'}
+                tabIndex={mode === 'isolated' ? 0 : -1}
                 onClick={() => setMode('isolated')}
+                onKeyDown={(event) =>
+                  handleRadioKeyDown(event, mode, ['isolated', 'shared'] as const, setMode)
+                }
                 className={`flex-1 flex justify-center items-center gap-2 px-3 py-1.5 rounded-[10px] text-sm font-medium transition-all duration-200 overflow-hidden ${
                   mode === 'isolated'
                     ? 'bg-background text-blue-600 dark:text-blue-400 shadow-sm ring-1 ring-border/50'
@@ -138,7 +183,11 @@ export function EditAccountContextDialog({
                 type="button"
                 role="radio"
                 aria-checked={mode === 'shared'}
+                tabIndex={mode === 'shared' ? 0 : -1}
                 onClick={() => setMode('shared')}
+                onKeyDown={(event) =>
+                  handleRadioKeyDown(event, mode, ['isolated', 'shared'] as const, setMode)
+                }
                 className={`flex-1 flex justify-center items-center gap-2 px-3 py-1.5 rounded-[10px] text-sm font-medium transition-all duration-200 overflow-hidden ${
                   mode === 'shared'
                     ? 'bg-background text-emerald-600 dark:text-emerald-400 shadow-sm ring-1 ring-border/50'
@@ -191,7 +240,16 @@ export function EditAccountContextDialog({
                   type="button"
                   role="radio"
                   aria-checked={continuityMode === 'standard'}
+                  tabIndex={continuityMode === 'standard' ? 0 : -1}
                   onClick={() => setContinuityMode('standard')}
+                  onKeyDown={(event) =>
+                    handleRadioKeyDown(
+                      event,
+                      continuityMode,
+                      ['standard', 'deeper'] as const,
+                      setContinuityMode
+                    )
+                  }
                   className={`flex-1 flex justify-center items-center gap-2 px-3 py-1.5 rounded-[10px] text-sm font-medium transition-all duration-200 overflow-hidden ${
                     continuityMode === 'standard'
                       ? 'bg-background text-emerald-600 dark:text-emerald-400 shadow-sm ring-1 ring-border/50'
@@ -205,7 +263,16 @@ export function EditAccountContextDialog({
                   type="button"
                   role="radio"
                   aria-checked={continuityMode === 'deeper'}
+                  tabIndex={continuityMode === 'deeper' ? 0 : -1}
                   onClick={() => setContinuityMode('deeper')}
+                  onKeyDown={(event) =>
+                    handleRadioKeyDown(
+                      event,
+                      continuityMode,
+                      ['standard', 'deeper'] as const,
+                      setContinuityMode
+                    )
+                  }
                   className={`flex-1 flex justify-center items-center gap-2 px-3 py-1.5 rounded-[10px] text-sm font-medium transition-all duration-200 overflow-hidden ${
                     continuityMode === 'deeper'
                       ? 'bg-background text-indigo-600 dark:text-indigo-400 shadow-sm ring-1 ring-border/50'
@@ -228,6 +295,40 @@ export function EditAccountContextDialog({
             {t('editAccountContext.credentialsIsolated')}
           </p>
 
+          {showPlainLaneMismatch && (
+            <div className="rounded-[14px] border border-amber-200 bg-amber-50/50 p-4 text-xs shadow-sm dark:border-amber-900/40 dark:bg-amber-900/10">
+              <div className="space-y-2">
+                <p className="font-medium text-foreground">
+                  {t('continuityOverview.plainLaneTitle')}
+                </p>
+                <p className="text-muted-foreground leading-relaxed">
+                  {t('continuityOverview.plainLaneDescription', {
+                    lane: laneLabel || 'plain ccs',
+                    name: account.name,
+                  })}
+                </p>
+                <div className="space-y-2">
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">ccs -r</span>
+                    <CopyButton value="ccs -r" size="icon" />
+                  </div>
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">ccs auth backup default</span>
+                    <CopyButton value="ccs auth backup default" size="icon" />
+                  </div>
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">{accountBackupCommand}</span>
+                    <CopyButton value={accountBackupCommand} size="icon" />
+                  </div>
+                  <div className="rounded-md border bg-background px-2 py-2 font-mono text-[11px] flex items-start gap-2">
+                    <span className="flex-1 break-all">{defaultCommand}</span>
+                    <CopyButton value={defaultCommand} size="icon" />
+                  </div>
+                </div>
+              </div>
+            </div>
+          )}
+
           <div
             className={`rounded-[14px] border p-4 text-xs shadow-sm transition-colors ${mode === 'isolated' ? 'bg-blue-50/50 border-blue-200 dark:bg-blue-900/10 dark:border-blue-800/40' : 'bg-muted/40 border-border/60'}`}
           >

ui/src/hooks/use-accounts.ts

@@ -5,7 +5,7 @@
 
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { api } from '@/lib/api-client';
-import type { Account } from '@/lib/api-client';
+import type { Account, PlainCcsLane } from '@/lib/api-client';
 import {
   summarizeAuthAccountContinuity,
   type AuthAccountRow,
@@ -30,6 +30,7 @@ export interface AuthAccountsView {
   deeperReadyGroups: string[];
   sharedGroups: string[];
   groupSummaries: SharedGroupSummary[];
+  plainCcsLane: PlainCcsLane | null;
 }
 
 export function useAccounts() {
@@ -61,6 +62,7 @@ export function useAccounts() {
         deeperReadyGroups: continuity.deeperReadyGroups,
         sharedGroups: continuity.sharedGroups,
         groupSummaries: continuity.groupSummaries,
+        plainCcsLane: data.plain_ccs_lane ?? null,
       };
     },
   });

ui/src/lib/api-client.ts

@@ -733,6 +733,14 @@ export interface Account {
   displayName?: string;
 }
 
+export interface PlainCcsLane {
+  kind: 'native' | 'account-default' | 'account-inherited' | 'profile-default' | 'ambient';
+  label: string;
+  account_name?: string | null;
+  profile_name?: string | null;
+  project_count: number;
+}
+
 export interface UpdateAccountContext {
   context_mode: 'isolated' | 'shared';
   context_group?: string;
@@ -1120,7 +1128,10 @@ export const api = {
     },
   },
   accounts: {
-    list: () => request<{ accounts: Account[]; default: string | null }>('/accounts'),
+    list: () =>
+      request<{ accounts: Account[]; default: string | null; plain_ccs_lane?: PlainCcsLane }>(
+        '/accounts'
+      ),
     setDefault: (name: string) =>
       request('/accounts/default', {
         method: 'POST',

ui/src/lib/i18n.ts

@@ -540,6 +540,21 @@ const resources = {
             'If the original conversation is important, keep resuming it from the original account until the second account is ready.',
         },
       },
+      continuityOverview: {
+        plainLaneTitle: 'Plain ccs is using a different resume lane',
+        plainLaneDescription:
+          'Plain ccs currently resumes from {{lane}}, not this account lane. Recover the original lane first before changing sync settings.',
+        setDefaultHint:
+          'Use the Set Default action on the account you want plain ccs to follow in future sessions.',
+        recommendBadge: 'Recommend {{group}}',
+        partialBadge: 'Partial sync {{group}}',
+        lane: {
+          native: 'native Claude (~/.claude)',
+          accountDefault: 'account {{name}}',
+          accountInherited: 'account {{name}} via continuity inheritance',
+          profileDefault: 'default profile {{name}} via native Claude lane',
+        },
+      },
       accountsTable: {
         name: 'Name',
         type: 'Type',
@@ -573,6 +588,12 @@ const resources = {
         sameGroupPeerCount_other: '{{count}} same-group peers',
         legacyReview: 'Review and confirm this inferred default.',
         noHandoff: 'Cross-account resume stays in the original account.',
+        badges: {
+          shared: 'Shared',
+          deeper: 'Deeper',
+          legacy: 'Legacy',
+          isolated: 'Isolated',
+        },
       },
       addAccountDialog: {
         title: 'Add {{displayName}} Account',
@@ -1820,6 +1841,20 @@ const resources = {
           resumeOriginal: '在第二个账号配置完成之前，重要会话仍应从原账号继续恢复。',
         },
       },
+      continuityOverview: {
+        plainLaneTitle: '普通 ccs 正在使用不同的续接通道',
+        plainLaneDescription:
+          '普通 ccs 当前会从 {{lane}} 续接，而不是这个账号通道。请先恢复原通道中的会话，再修改同步设置。',
+        setDefaultHint: '如果希望以后普通 ccs 跟随某个账号，请使用该账号行上的“设为默认”。',
+        recommendBadge: '建议 {{group}}',
+        partialBadge: '部分同步 {{group}}',
+        lane: {
+          native: '原生 Claude（~/.claude）',
+          accountDefault: '账号 {{name}}',
+          accountInherited: '通过连续性继承使用账号 {{name}}',
+          profileDefault: '默认配置 {{name}}（仍走原生 Claude 通道）',
+        },
+      },
       accountsTable: {
         name: '名称',
         type: '类型',
@@ -1853,6 +1888,12 @@ const resources = {
         sameGroupPeerCount_other: '{{count}} 个同组账号',
         legacyReview: '请检查并确认这个推断出的默认状态。',
         noHandoff: '跨账号续接仍会回到原账号。',
+        badges: {
+          shared: '共享',
+          deeper: '更深',
+          legacy: '旧策略',
+          isolated: '隔离',
+        },
       },
       addAccountDialog: {
         title: '添加 {{displayName}} 账号',
@@ -3118,6 +3159,21 @@ const resources = {
             'Cho đến khi tài khoản thứ hai sẵn sàng, các cuộc trò chuyện quan trọng vẫn nên được resume từ tài khoản gốc.',
         },
       },
+      continuityOverview: {
+        plainLaneTitle: 'Plain ccs đang dùng một lane resume khác',
+        plainLaneDescription:
+          'Plain ccs hiện resume từ {{lane}}, không phải lane của tài khoản này. Hãy khôi phục lane gốc trước khi đổi cài đặt sync.',
+        setDefaultHint:
+          'Nếu muốn plain ccs theo một tài khoản trong các phiên sau, hãy dùng hành động Set Default trên dòng tài khoản đó.',
+        recommendBadge: 'Đề xuất {{group}}',
+        partialBadge: 'Đồng bộ một phần {{group}}',
+        lane: {
+          native: 'Claude gốc (~/.claude)',
+          accountDefault: 'tài khoản {{name}}',
+          accountInherited: 'tài khoản {{name}} qua continuity inheritance',
+          profileDefault: 'profile mặc định {{name}} qua lane Claude gốc',
+        },
+      },
       accountsTable: {
         name: 'Tên',
         type: 'Kiểu',
@@ -3152,6 +3208,12 @@ const resources = {
         sameGroupPeerCount_other: '{{count}} tài khoản cùng nhóm',
         legacyReview: 'Hãy xem lại và xác nhận trạng thái suy ra này.',
         noHandoff: 'Resume xuyên tài khoản vẫn sẽ quay về tài khoản gốc.',
+        badges: {
+          shared: 'Chia sẻ',
+          deeper: 'Sâu hơn',
+          legacy: 'Kế thừa',
+          isolated: 'Tách biệt',
+        },
       },
       addAccountDialog: {
         title: 'Thêm tài khoản {{displayName}}',
@@ -4454,6 +4516,21 @@ const resources = {
             '2 つ目のアカウントが整うまでは、重要な会話は元のアカウントから再開し続けてください。',
         },
       },
+      continuityOverview: {
+        plainLaneTitle: '通常の ccs は別の再開レーンを使っています',
+        plainLaneDescription:
+          '通常の ccs は現在 {{lane}} から再開しており、このアカウントのレーンではありません。同期設定を変える前に元のレーンを先に復旧してください。',
+        setDefaultHint:
+          '今後の通常の ccs を特定のアカウントに合わせたい場合は、その行の「既定に設定」を使ってください。',
+        recommendBadge: '推奨 {{group}}',
+        partialBadge: '部分同期 {{group}}',
+        lane: {
+          native: 'ネイティブ Claude（~/.claude）',
+          accountDefault: 'アカウント {{name}}',
+          accountInherited: '継続性継承によるアカウント {{name}}',
+          profileDefault: '既定プロファイル {{name}}（ネイティブ Claude レーン）',
+        },
+      },
       accountsTable: {
         name: '名前',
         type: '種別',
@@ -4488,6 +4565,12 @@ const resources = {
         sameGroupPeerCount_other: '{{count}} 件の同グループアカウント',
         legacyReview: 'この推定された既定状態を確認して明示的に確定してください。',
         noHandoff: 'アカウント間再開は元のアカウントに残ります。',
+        badges: {
+          shared: '共有',
+          deeper: '拡張',
+          legacy: 'レガシー',
+          isolated: '分離',
+        },
       },
       addAccountDialog: {
         title: '{{displayName}} アカウントを追加',

ui/src/pages/accounts.tsx

@@ -39,6 +39,7 @@ export function AccountsPage() {
   const deeperReadyGroups = data?.deeperReadyGroups || [];
   const sharedGroups = data?.sharedGroups || [];
   const groupSummaries = data?.groupSummaries || [];
+  const plainCcsLane = data?.plainCcsLane || null;
 
   const legacyTargets = authAccounts.filter(
     (account) => account.context_inferred || account.continuity_inferred
@@ -189,6 +190,7 @@ export function AccountsPage() {
           <div className="flex-1 min-h-0 p-5 space-y-4 overflow-y-auto">
             <ContinuityOverview
               totalAccounts={authAccounts.length}
+              primaryAccountName={authAccounts.length === 1 ? authAccounts[0]?.name : null}
               isolatedCount={isolatedCount}
               sharedStandardCount={sharedStandardCount}
               deeperSharedCount={deeperSharedCount}
@@ -200,6 +202,7 @@ export function AccountsPage() {
               deeperReadyGroups={deeperReadyGroups}
               legacyTargetCount={legacyTargetCount}
               cliproxyCount={cliproxyCount}
+              plainCcsLane={plainCcsLane}
             />
 
             <Card className="flex flex-col">
@@ -217,6 +220,7 @@ export function AccountsPage() {
                     data={authAccounts}
                     defaultAccount={data?.default ?? null}
                     groupSummaries={groupSummaries}
+                    plainCcsLane={plainCcsLane}
                   />
                 )}
               </CardContent>
@@ -264,6 +268,7 @@ export function AccountsPage() {
 
         <ContinuityOverview
           totalAccounts={authAccounts.length}
+          primaryAccountName={authAccounts.length === 1 ? authAccounts[0]?.name : null}
           isolatedCount={isolatedCount}
           sharedStandardCount={sharedStandardCount}
           deeperSharedCount={deeperSharedCount}
@@ -275,6 +280,7 @@ export function AccountsPage() {
           deeperReadyGroups={deeperReadyGroups}
           legacyTargetCount={legacyTargetCount}
           cliproxyCount={cliproxyCount}
+          plainCcsLane={plainCcsLane}
         />
 
         <Card>
@@ -289,6 +295,7 @@ export function AccountsPage() {
                 data={authAccounts}
                 defaultAccount={data?.default ?? null}
                 groupSummaries={groupSummaries}
+                plainCcsLane={plainCcsLane}
               />
             )}
           </CardContent>