feat: opt-in auto_fetch and base_branch config for clone

Replace the always-on syncDefaultBranch with opt-in resolveBaseBranch:

- Add auto_fetch config (default: false) — only fetch when enabled
- Add base_branch config (project and global) — fallback to current branch
- Fetch-only mode: git fetch origin without modifying local branches
- Use fetched commit hash (origin/<base_branch>) to reset clone to latest
- No more git merge --ff-only or git fetch origin main:main

Config example:
  # ~/.takt/config.yaml or .takt/config.yaml
  auto_fetch: true
  base_branch: develop

Addresses review feedback: opt-in behavior, no local branch changes,
configurable base branch with current-branch fallback.

src/__tests__/clone.test.ts

@@ -56,6 +56,11 @@ describe('cloneAndIsolate git config propagation', () => {
       const argsArr = args as string[];
       const options = opts as { cwd?: string };
 
+      // git rev-parse --abbrev-ref HEAD (resolveBaseBranch: getCurrentBranch)
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref' && argsArr[2] === 'HEAD') {
+        return 'main\n';
+      }
+
       // git clone
       if (argsArr[0] === 'clone') {
         return Buffer.from('');
@@ -176,6 +181,11 @@ describe('branch and worktree path formatting with issue numbers', () => {
     mockExecFileSync.mockImplementation((cmd, args) => {
       const argsArr = args as string[];
 
+      // git rev-parse --abbrev-ref HEAD (resolveBaseBranch: getCurrentBranch)
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref' && argsArr[2] === 'HEAD') {
+        return 'main\n';
+      }
+
       // git clone
       if (argsArr[0] === 'clone') {
         const clonePath = argsArr[argsArr.length - 1];
@@ -313,3 +323,133 @@ describe('branch and worktree path formatting with issue numbers', () => {
     expect(result.path).toMatch(/\/\d{8}T\d{4}$/);
   });
 });
+
+describe('resolveBaseBranch', () => {
+  it('should not fetch when auto_fetch is disabled (default)', () => {
+    // Given: auto_fetch is off (default), HEAD is on main
+    const fetchCalls: string[][] = [];
+
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'fetch') {
+        fetchCalls.push(argsArr);
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref') {
+        return 'main\n';
+      }
+      if (argsArr[0] === 'clone') return Buffer.from('');
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--verify') {
+        throw new Error('branch not found');
+      }
+      if (argsArr[0] === 'checkout') return Buffer.from('');
+      return Buffer.from('');
+    });
+
+    // When
+    createSharedClone('/project', {
+      worktree: true,
+      taskSlug: 'test-no-fetch',
+    });
+
+    // Then: no fetch was performed
+    expect(fetchCalls).toHaveLength(0);
+  });
+
+  it('should use current branch as base when no base_branch config', () => {
+    // Given: HEAD is on develop
+    const cloneCalls: string[][] = [];
+
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref') {
+        return 'develop\n';
+      }
+      if (argsArr[0] === 'clone') {
+        cloneCalls.push(argsArr);
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--verify') {
+        throw new Error('branch not found');
+      }
+      if (argsArr[0] === 'checkout') return Buffer.from('');
+      return Buffer.from('');
+    });
+
+    // When
+    createSharedClone('/project', {
+      worktree: true,
+      taskSlug: 'use-current-branch',
+    });
+
+    // Then: clone was called with --branch develop (current branch)
+    expect(cloneCalls).toHaveLength(1);
+    expect(cloneCalls[0]).toContain('--branch');
+    expect(cloneCalls[0]).toContain('develop');
+  });
+
+  it('should continue clone creation when fetch fails (network error)', () => {
+    // Given: fetch throws (no network)
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'fetch') {
+        throw new Error('Could not resolve host: github.com');
+      }
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref') {
+        return 'main\n';
+      }
+      if (argsArr[0] === 'clone') return Buffer.from('');
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      if (argsArr[0] === 'rev-parse') throw new Error('branch not found');
+      if (argsArr[0] === 'checkout') return Buffer.from('');
+      return Buffer.from('');
+    });
+
+    // When/Then: should not throw, clone still created
+    const result = createSharedClone('/project', {
+      worktree: true,
+      taskSlug: 'offline-task',
+    });
+
+    expect(result.branch).toMatch(/offline-task$/);
+  });
+
+  it('should also resolve base branch before createTempCloneForBranch', () => {
+    // Given
+    mockExecFileSync.mockImplementation((_cmd, args) => {
+      const argsArr = args as string[];
+
+      if (argsArr[0] === 'rev-parse' && argsArr[1] === '--abbrev-ref') {
+        return 'main\n';
+      }
+      if (argsArr[0] === 'clone') return Buffer.from('');
+      if (argsArr[0] === 'remote') return Buffer.from('');
+      if (argsArr[0] === 'config') {
+        if (argsArr[1] === '--local') throw new Error('not set');
+        return Buffer.from('');
+      }
+      return Buffer.from('');
+    });
+
+    // When/Then: should not throw
+    const result = createTempCloneForBranch('/project', 'existing-branch');
+    expect(result.branch).toBe('existing-branch');
+  });
+});

src/__tests__/pipelineExecution.test.ts

@@ -31,10 +31,11 @@ vi.mock('../features/tasks/index.js', () => ({
   executeTask: mockExecuteTask,
 }));
 
-const mockResolveConfigValues = vi.fn();
-vi.mock('../infra/config/index.js', () => ({
-  resolveConfigValues: mockResolveConfigValues,
-}));
+const mockResolveConfigValues = vi.fn();
+vi.mock('../infra/config/index.js', () => ({
+  resolveConfigValues: mockResolveConfigValues,
+  resolveConfigValue: vi.fn(() => undefined),
+}));
 
 // Mock execFileSync for git operations
 const mockExecFileSync = vi.fn();
@@ -67,13 +68,13 @@ vi.mock('../shared/utils/index.js', async (importOriginal) => ({
 const { executePipeline } = await import('../features/pipeline/index.js');
 
 describe('executePipeline', () => {
-  beforeEach(() => {
-    vi.clearAllMocks();
-    // Default: git operations succeed
-    mockExecFileSync.mockReturnValue('abc1234\n');
-    // Default: no pipeline config
-    mockResolveConfigValues.mockReturnValue({ pipeline: undefined });
-  });
+  beforeEach(() => {
+    vi.clearAllMocks();
+    // Default: git operations succeed
+    mockExecFileSync.mockReturnValue('abc1234\n');
+    // Default: no pipeline config
+    mockResolveConfigValues.mockReturnValue({ pipeline: undefined });
+  });
 
   it('should return exit code 2 when neither --issue nor --task is specified', async () => {
     const exitCode = await executePipeline({
@@ -305,11 +306,11 @@ describe('executePipeline', () => {
 
   describe('PipelineConfig template expansion', () => {
     it('should use commit_message_template when configured', async () => {
-      mockResolveConfigValues.mockReturnValue({
-        pipeline: {
-          commitMessageTemplate: 'fix: {title} (#{issue})',
-        },
-      });
+      mockResolveConfigValues.mockReturnValue({
+        pipeline: {
+          commitMessageTemplate: 'fix: {title} (#{issue})',
+        },
+      });
 
       mockFetchIssue.mockReturnValueOnce({
         number: 42,
@@ -337,11 +338,11 @@ describe('executePipeline', () => {
     });
 
     it('should use default_branch_prefix when configured', async () => {
-      mockResolveConfigValues.mockReturnValue({
-        pipeline: {
-          defaultBranchPrefix: 'feat/',
-        },
-      });
+      mockResolveConfigValues.mockReturnValue({
+        pipeline: {
+          defaultBranchPrefix: 'feat/',
+        },
+      });
 
       mockFetchIssue.mockReturnValueOnce({
         number: 10,
@@ -369,11 +370,11 @@ describe('executePipeline', () => {
     });
 
     it('should use pr_body_template when configured for PR creation', async () => {
-      mockResolveConfigValues.mockReturnValue({
-        pipeline: {
-          prBodyTemplate: '## Summary\n{issue_body}\n\nCloses #{issue}',
-        },
-      });
+      mockResolveConfigValues.mockReturnValue({
+        pipeline: {
+          prBodyTemplate: '## Summary\n{issue_body}\n\nCloses #{issue}',
+        },
+      });
 
       mockFetchIssue.mockReturnValueOnce({
         number: 50,

src/core/models/persisted-global-config.ts

@@ -123,6 +123,10 @@ export interface PersistedGlobalConfig {
   concurrency: number;
   /** Polling interval in ms for picking up new tasks during takt run (default: 500, range: 100-5000) */
   taskPollIntervalMs: number;
+  /** Opt-in: fetch remote before cloning to keep clones up-to-date (default: false) */
+  autoFetch?: boolean;
+  /** Base branch to clone from (default: current branch) */
+  baseBranch?: string;
 }
 
 /** Project-level configuration */
@@ -132,4 +136,6 @@ export interface ProjectConfig {
   providerOptions?: MovementProviderOptions;
   /** Provider-specific permission profiles */
   providerProfiles?: ProviderPermissionProfiles;
+  /** Base branch to clone from (overrides global baseBranch) */
+  baseBranch?: string;
 }

src/core/models/schemas.ts

@@ -481,6 +481,10 @@ export const GlobalConfigSchema = z.object({
   concurrency: z.number().int().min(1).max(10).optional().default(1),
   /** Polling interval in ms for picking up new tasks during takt run (default: 500, range: 100-5000) */
   task_poll_interval_ms: z.number().int().min(100).max(5000).optional().default(500),
+  /** Opt-in: fetch remote before cloning to keep clones up-to-date (default: false) */
+  auto_fetch: z.boolean().optional().default(false),
+  /** Base branch to clone from (default: current branch) */
+  base_branch: z.string().optional(),
 });
 
 /** Project config schema */
@@ -489,4 +493,6 @@ export const ProjectConfigSchema = z.object({
   provider: z.enum(['claude', 'codex', 'opencode', 'mock']).optional(),
   provider_options: MovementProviderOptionsSchema,
   provider_profiles: ProviderPermissionProfilesSchema,
+  /** Base branch to clone from (overrides global base_branch) */
+  base_branch: z.string().optional(),
 });

src/features/pipeline/execute.ts

@@ -19,7 +19,7 @@ import {
   buildPrBody,
   type GitHubIssue,
 } from '../../infra/github/index.js';
-import { stageAndCommit, getCurrentBranch } from '../../infra/task/index.js';
+import { stageAndCommit, resolveBaseBranch } from '../../infra/task/index.js';
 import { executeTask, type TaskExecutionOptions, type PipelineExecutionOptions } from '../tasks/index.js';
 import { resolveConfigValues } from '../../infra/config/index.js';
 import { info, error, success, status, blankLine } from '../../shared/ui/index.js';
@@ -134,11 +134,12 @@ export async function executePipeline(options: PipelineExecutionOptions): Promis
     return EXIT_ISSUE_FETCH_FAILED;
   }
 
-  // --- Step 2: Create branch (skip if --skip-git) ---
+  // --- Step 2: Sync & create branch (skip if --skip-git) ---
   let branch: string | undefined;
   let baseBranch: string | undefined;
   if (!skipGit) {
-    baseBranch = getCurrentBranch(cwd);
+    const resolved = resolveBaseBranch(cwd);
+    baseBranch = resolved.branch;
     branch = options.branch ?? generatePipelineBranchName(pipelineConfig, options.issueNumber);
     info(`Creating branch: ${branch}`);
     try {

src/infra/config/env/config-env-overrides.ts

@@ -124,6 +124,8 @@ const GLOBAL_ENV_SPECS: readonly EnvSpec[] = [
   { path: 'verbose', type: 'boolean' },
   { path: 'concurrency', type: 'number' },
   { path: 'task_poll_interval_ms', type: 'number' },
+  { path: 'auto_fetch', type: 'boolean' },
+  { path: 'base_branch', type: 'string' },
 ];
 
 const PROJECT_ENV_SPECS: readonly EnvSpec[] = [
@@ -140,6 +142,7 @@ const PROJECT_ENV_SPECS: readonly EnvSpec[] = [
   { path: 'provider_options.claude.sandbox.allow_unsandboxed_commands', type: 'boolean' },
   { path: 'provider_options.claude.sandbox.excluded_commands', type: 'json' },
   { path: 'provider_profiles', type: 'json' },
+  { path: 'base_branch', type: 'string' },
 ];
 
 export function applyGlobalConfigEnvOverrides(target: Record<string, unknown>): void {

src/infra/config/global/globalConfig.ts

@@ -220,6 +220,8 @@ export class GlobalConfigManager {
       verbose: parsed.verbose,
       concurrency: parsed.concurrency,
       taskPollIntervalMs: parsed.task_poll_interval_ms,
+      autoFetch: parsed.auto_fetch,
+      baseBranch: parsed.base_branch,
     };
     validateProviderModelCompatibility(config.provider, config.model);
     this.cachedConfig = config;
@@ -350,6 +352,12 @@ export class GlobalConfigManager {
     if (config.taskPollIntervalMs !== undefined && config.taskPollIntervalMs !== 500) {
       raw.task_poll_interval_ms = config.taskPollIntervalMs;
     }
+    if (config.autoFetch !== undefined) {
+      raw.auto_fetch = config.autoFetch;
+    }
+    if (config.baseBranch) {
+      raw.base_branch = config.baseBranch;
+    }
     writeFileSync(configPath, stringifyYaml(raw), 'utf-8');
     this.invalidateCache();
     invalidateAllResolvedConfigCache();

src/infra/config/resolveConfigValue.ts

@@ -79,6 +79,8 @@ const RESOLUTION_REGISTRY: Partial<{ [K in ConfigParameterKey]: ResolutionRule<K
   draftPr: { layers: ['local', 'global'] },
   analytics: { layers: ['local', 'global'], mergeMode: 'analytics' },
   verbose: { layers: ['local', 'global'], defaultValue: false },
+  autoFetch: { layers: ['global'], defaultValue: false },
+  baseBranch: { layers: ['local', 'global'] },
 };
 
 function resolveAnalyticsMerged(
@@ -128,6 +130,8 @@ function getLocalLayerValue<K extends ConfigParameterKey>(
       return project.providerOptions as LoadedConfig[K] | undefined;
     case 'providerProfiles':
       return project.providerProfiles as LoadedConfig[K] | undefined;
+    case 'baseBranch':
+      return (project as Record<string, unknown>).base_branch as LoadedConfig[K] | undefined;
     default:
       return undefined;
   }

src/infra/task/clone.ts

@@ -124,6 +124,64 @@ export class CloneManager {
     return projectDir;
   }
 
+  /**
+   * Resolve the base branch for cloning and optionally fetch from remote.
+   *
+   * When `auto_fetch` config is true:
+   *   1. Runs `git fetch origin` (without modifying local branches)
+   *   2. Resolves base branch from config `base_branch` → current branch fallback
+   *   3. Returns the branch name and the fetched commit hash of `origin/<baseBranch>`
+   *
+   * When `auto_fetch` is false (default):
+   *   Returns only the branch name (config `base_branch` → current branch fallback)
+   *
+   * Any failure (network, no remote, etc.) is non-fatal.
+   */
+  static resolveBaseBranch(projectDir: string): { branch: string; fetchedCommit?: string } {
+    const configBaseBranch = resolveConfigValue(projectDir, 'baseBranch') as string | undefined;
+    const autoFetch = resolveConfigValue(projectDir, 'autoFetch') as boolean | undefined;
+
+    // Determine base branch: config base_branch → current branch
+    const baseBranch = configBaseBranch ?? CloneManager.getCurrentBranch(projectDir);
+
+    if (!autoFetch) {
+      return { branch: baseBranch };
+    }
+
+    try {
+      // Fetch only — do not modify any local branch refs
+      execFileSync('git', ['fetch', 'origin'], {
+        cwd: projectDir,
+        stdio: 'pipe',
+      });
+
+      // Get the latest commit hash from the remote-tracking ref
+      const fetchedCommit = execFileSync(
+        'git', ['rev-parse', `origin/${baseBranch}`],
+        { cwd: projectDir, encoding: 'utf-8', stdio: 'pipe' },
+      ).trim();
+
+      log.info('Fetched remote and resolved base branch', { baseBranch, fetchedCommit });
+      return { branch: baseBranch, fetchedCommit };
+    } catch (err) {
+      // Network errors, no remote, no tracking ref — all non-fatal
+      log.info('Failed to fetch from remote, continuing with local state', { baseBranch, error: String(err) });
+      return { branch: baseBranch };
+    }
+  }
+
+  /** Get current branch name */
+  private static getCurrentBranch(projectDir: string): string {
+    try {
+      return execFileSync(
+        'git', ['rev-parse', '--abbrev-ref', 'HEAD'],
+        { cwd: projectDir, encoding: 'utf-8', stdio: 'pipe' },
+      ).trim();
+    } catch {
+      return 'main';
+    }
+  }
+
   /** Clone a repository and remove origin to isolate from the main repo.
    *  When `branch` is specified, `--branch` is passed to `git clone` so the
    *  branch is checked out as a local branch *before* origin is removed.
@@ -180,6 +238,8 @@ export class CloneManager {
 
   /** Create a git clone for a task */
   createSharedClone(projectDir: string, options: WorktreeOptions): WorktreeResult {
+    const { branch: baseBranch, fetchedCommit } = CloneManager.resolveBaseBranch(projectDir);
+
     const clonePath = CloneManager.resolveClonePath(projectDir, options);
     const branch = CloneManager.resolveBranchName(options);
 
@@ -188,7 +248,12 @@ export class CloneManager {
     if (CloneManager.branchExists(projectDir, branch)) {
       CloneManager.cloneAndIsolate(projectDir, clonePath, branch);
     } else {
-      CloneManager.cloneAndIsolate(projectDir, clonePath);
+      // Clone from the base branch so the task starts from latest state
+      CloneManager.cloneAndIsolate(projectDir, clonePath, baseBranch);
+      // If we fetched a newer commit from remote, reset to it
+      if (fetchedCommit) {
+        execFileSync('git', ['reset', '--hard', fetchedCommit], { cwd: clonePath, stdio: 'pipe' });
+      }
       execFileSync('git', ['checkout', '-b', branch], { cwd: clonePath, stdio: 'pipe' });
     }
 
@@ -200,6 +265,8 @@ export class CloneManager {
 
   /** Create a temporary clone for an existing branch */
   createTempCloneForBranch(projectDir: string, branch: string): WorktreeResult {
+    CloneManager.resolveBaseBranch(projectDir);
+
     const timestamp = CloneManager.generateTimestamp();
     const clonePath = path.join(CloneManager.resolveCloneBaseDir(projectDir), `tmp-${timestamp}`);
 
@@ -285,3 +352,7 @@ export function removeCloneMeta(projectDir: string, branch: string): void {
 export function cleanupOrphanedClone(projectDir: string, branch: string): void {
   defaultManager.cleanupOrphanedClone(projectDir, branch);
 }
+
+export function resolveBaseBranch(projectDir: string): { branch: string; fetchedCommit?: string } {
+  return CloneManager.resolveBaseBranch(projectDir);
+}

src/infra/task/index.ts

@@ -44,6 +44,7 @@ export {
   saveCloneMeta,
   removeCloneMeta,
   cleanupOrphanedClone,
+  resolveBaseBranch,
 } from './clone.js';
 export {
   detectDefaultBranch,