auto PR のベースブランチをブランチ作成前の現在ブランチに設定

createPullRequest の全呼び出し箇所で base が未指定だったため、
PR が常にリポジトリデフォルトブランチ（main）向けに作成されていた。
ブランチ作成/clone作成の直前に getCurrentBranch() で元ブランチを
取得し、PR作成時に base として渡すように修正。

src/__tests__/cli-worktree.test.ts

@@ -10,6 +10,11 @@ vi.mock('../shared/prompt/index.js', () => ({
   selectOptionWithDefault: vi.fn(),
 }));
 
+vi.mock('../infra/task/git.js', () => ({
+  stageAndCommit: vi.fn(),
+  getCurrentBranch: vi.fn(() => 'main'),
+}));
+
 vi.mock('../infra/task/clone.js', () => ({
   createSharedClone: vi.fn(),
   removeClone: vi.fn(),

src/__tests__/getCurrentBranch.test.ts

@@ -0,0 +1,57 @@
+/**
+ * Tests for getCurrentBranch
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { execFileSync } from 'node:child_process';
+
+vi.mock('node:child_process', () => ({
+  execFileSync: vi.fn(),
+}));
+
+const mockExecFileSync = vi.mocked(execFileSync);
+
+import { getCurrentBranch } from '../infra/task/git.js';
+
+beforeEach(() => {
+  vi.clearAllMocks();
+});
+
+describe('getCurrentBranch', () => {
+  it('should return the current branch name', () => {
+    // Given
+    mockExecFileSync.mockReturnValue('feature/my-branch\n');
+
+    // When
+    const result = getCurrentBranch('/project');
+
+    // Then
+    expect(result).toBe('feature/my-branch');
+    expect(mockExecFileSync).toHaveBeenCalledWith(
+      'git',
+      ['rev-parse', '--abbrev-ref', 'HEAD'],
+      { cwd: '/project', encoding: 'utf-8', stdio: 'pipe' },
+    );
+  });
+
+  it('should trim whitespace from output', () => {
+    // Given
+    mockExecFileSync.mockReturnValue('  main  \n');
+
+    // When
+    const result = getCurrentBranch('/project');
+
+    // Then
+    expect(result).toBe('main');
+  });
+
+  it('should propagate errors from git', () => {
+    // Given
+    mockExecFileSync.mockImplementation(() => {
+      throw new Error('not a git repository');
+    });
+
+    // When / Then
+    expect(() => getCurrentBranch('/not-a-repo')).toThrow('not a git repository');
+  });
+});

src/__tests__/it-pipeline-modes.test.ts

@@ -65,6 +65,7 @@ vi.mock('../infra/github/pr.js', () => ({
 
 vi.mock('../infra/task/git.js', () => ({
   stageAndCommit: vi.fn().mockReturnValue('abc1234'),
+  getCurrentBranch: vi.fn().mockReturnValue('main'),
 }));
 
 vi.mock('../shared/ui/index.js', () => ({

src/__tests__/pipelineExecution.test.ts

@@ -218,6 +218,37 @@ describe('executePipeline', () => {
     );
   });
 
+  it('should pass baseBranch as base to createPullRequest', async () => {
+    // Given: getCurrentBranch returns 'develop' before branch creation
+    mockExecFileSync.mockImplementation((_cmd: string, args: string[]) => {
+      if (args[0] === 'rev-parse' && args[1] === '--abbrev-ref') {
+        return 'develop\n';
+      }
+      return 'abc1234\n';
+    });
+    mockExecuteTask.mockResolvedValueOnce(true);
+    mockCreatePullRequest.mockReturnValueOnce({ success: true, url: 'https://github.com/test/pr/1' });
+
+    // When
+    const exitCode = await executePipeline({
+      task: 'Fix the bug',
+      piece: 'default',
+      branch: 'fix/my-branch',
+      autoPr: true,
+      cwd: '/tmp/test',
+    });
+
+    // Then
+    expect(exitCode).toBe(0);
+    expect(mockCreatePullRequest).toHaveBeenCalledWith(
+      '/tmp/test',
+      expect.objectContaining({
+        branch: 'fix/my-branch',
+        base: 'develop',
+      }),
+    );
+  });
+
   it('should use --task when both --task and positional task are provided', async () => {
     mockExecuteTask.mockResolvedValueOnce(true);
 

src/__tests__/selectAndExecute-autoPr.test.ts

@@ -23,6 +23,7 @@ vi.mock('../infra/task/index.js', () => ({
   createSharedClone: vi.fn(),
   autoCommitAndPush: vi.fn(),
   summarizeTaskName: vi.fn(),
+  getCurrentBranch: vi.fn(() => 'main'),
 }));
 
 vi.mock('../shared/ui/index.js', () => ({

src/__tests__/taskExecution.test.ts

@@ -25,6 +25,11 @@ vi.mock('../infra/task/clone.js', async (importOriginal) => ({
   removeClone: vi.fn(),
 }));
 
+vi.mock('../infra/task/git.js', async (importOriginal) => ({
+  ...(await importOriginal<Record<string, unknown>>()),
+  getCurrentBranch: vi.fn(() => 'main'),
+}));
+
 vi.mock('../infra/task/autoCommit.js', async (importOriginal) => ({
   ...(await importOriginal<Record<string, unknown>>()),
   autoCommitAndPush: vi.fn(),
@@ -68,12 +73,14 @@ vi.mock('../shared/constants.js', () => ({
 }));
 
 import { createSharedClone } from '../infra/task/clone.js';
+import { getCurrentBranch } from '../infra/task/git.js';
 import { summarizeTaskName } from '../infra/task/summarize.js';
 import { info } from '../shared/ui/index.js';
 import { resolveTaskExecution } from '../features/tasks/index.js';
 import type { TaskInfo } from '../infra/task/index.js';
 
 const mockCreateSharedClone = vi.mocked(createSharedClone);
+const mockGetCurrentBranch = vi.mocked(getCurrentBranch);
 const mockSummarizeTaskName = vi.mocked(summarizeTaskName);
 const mockInfo = vi.mocked(info);
 
@@ -150,11 +157,13 @@ describe('resolveTaskExecution', () => {
       branch: undefined,
       taskSlug: 'add-auth',
     });
+    expect(mockGetCurrentBranch).toHaveBeenCalledWith('/project');
     expect(result).toEqual({
       execCwd: '/project/../20260128T0504-add-auth',
       execPiece: 'default',
       isWorktree: true,
       branch: 'takt/20260128T0504-add-auth',
+      baseBranch: 'main',
     });
   });
 
@@ -396,4 +405,50 @@ describe('resolveTaskExecution', () => {
     // Then
     expect(result.autoPr).toBe(false);
   });
+
+  it('should capture baseBranch from getCurrentBranch when worktree is used', async () => {
+    // Given: Task with worktree, on 'develop' branch
+    mockGetCurrentBranch.mockReturnValue('develop');
+    const task: TaskInfo = {
+      name: 'task-on-develop',
+      content: 'Task on develop branch',
+      filePath: '/tasks/task.yaml',
+      data: {
+        task: 'Task on develop branch',
+        worktree: true,
+      },
+    };
+
+    mockSummarizeTaskName.mockResolvedValue('task-develop');
+    mockCreateSharedClone.mockReturnValue({
+      path: '/project/../task-develop',
+      branch: 'takt/task-develop',
+    });
+
+    // When
+    const result = await resolveTaskExecution(task, '/project', 'default');
+
+    // Then
+    expect(mockGetCurrentBranch).toHaveBeenCalledWith('/project');
+    expect(result.baseBranch).toBe('develop');
+  });
+
+  it('should not set baseBranch when worktree is not used', async () => {
+    // Given: Task without worktree
+    const task: TaskInfo = {
+      name: 'task-no-worktree',
+      content: 'Task without worktree',
+      filePath: '/tasks/task.yaml',
+      data: {
+        task: 'Task without worktree',
+      },
+    };
+
+    // When
+    const result = await resolveTaskExecution(task, '/project', 'default');
+
+    // Then
+    expect(mockGetCurrentBranch).not.toHaveBeenCalled();
+    expect(result.baseBranch).toBeUndefined();
+  });
 });

src/features/pipeline/execute.ts

@@ -19,7 +19,7 @@ import {
   buildPrBody,
   type GitHubIssue,
 } from '../../infra/github/index.js';
-import { stageAndCommit } from '../../infra/task/index.js';
+import { stageAndCommit, getCurrentBranch } from '../../infra/task/index.js';
 import { executeTask, type TaskExecutionOptions, type PipelineExecutionOptions } from '../tasks/index.js';
 import { loadGlobalConfig } from '../../infra/config/index.js';
 import { info, error, success, status, blankLine } from '../../shared/ui/index.js';
@@ -136,7 +136,9 @@ export async function executePipeline(options: PipelineExecutionOptions): Promis
 
   // --- Step 2: Create branch (skip if --skip-git) ---
   let branch: string | undefined;
+  let baseBranch: string | undefined;
   if (!skipGit) {
+    baseBranch = getCurrentBranch(cwd);
     branch = options.branch ?? generatePipelineBranchName(pipelineConfig, options.issueNumber);
     info(`Creating branch: ${branch}`);
     try {
@@ -206,6 +208,7 @@ export async function executePipeline(options: PipelineExecutionOptions): Promis
         branch,
         title: prTitle,
         body: prBody,
+        base: baseBranch,
         repo: options.repo,
       });
 

src/features/tasks/execute/selectAndExecute.ts

@@ -17,7 +17,7 @@ import {
   loadGlobalConfig,
 } from '../../../infra/config/index.js';
 import { confirm } from '../../../shared/prompt/index.js';
-import { createSharedClone, autoCommitAndPush, summarizeTaskName } from '../../../infra/task/index.js';
+import { createSharedClone, autoCommitAndPush, summarizeTaskName, getCurrentBranch } from '../../../infra/task/index.js';
 import { DEFAULT_PIECE_NAME } from '../../../shared/constants.js';
 import { info, error, success } from '../../../shared/ui/index.js';
 import { createLogger } from '../../../shared/utils/index.js';
@@ -111,6 +111,8 @@ export async function confirmAndCreateWorktree(
     return { execCwd: cwd, isWorktree: false };
   }
 
+  const baseBranch = getCurrentBranch(cwd);
+
   info('Generating branch name...');
   const taskSlug = await summarizeTaskName(task, { cwd });
 
@@ -121,7 +123,7 @@ export async function confirmAndCreateWorktree(
   });
   info(`Clone created: ${result.path} (branch: ${result.branch})`);
 
-  return { execCwd: result.path, isWorktree: true, branch: result.branch };
+  return { execCwd: result.path, isWorktree: true, branch: result.branch, baseBranch };
 }
 
 /**
@@ -161,7 +163,7 @@ export async function selectAndExecuteTask(
     return;
   }
 
-  const { execCwd, isWorktree, branch } = await confirmAndCreateWorktree(
+  const { execCwd, isWorktree, branch, baseBranch } = await confirmAndCreateWorktree(
     cwd,
     task,
     options?.createWorktree,
@@ -206,6 +208,7 @@ export async function selectAndExecuteTask(
         branch,
         title: task.length > 100 ? `${task.slice(0, 97)}...` : task,
         body: prBody,
+        base: baseBranch,
         repo: options?.repo,
       });
       if (prResult.success) {

src/features/tasks/execute/taskExecution.ts

@@ -3,7 +3,7 @@
  */
 
 import { loadPieceByIdentifier, isPiecePath, loadGlobalConfig } from '../../../infra/config/index.js';
-import { TaskRunner, type TaskInfo, createSharedClone, autoCommitAndPush, summarizeTaskName } from '../../../infra/task/index.js';
+import { TaskRunner, type TaskInfo, createSharedClone, autoCommitAndPush, summarizeTaskName, getCurrentBranch } from '../../../infra/task/index.js';
 import {
   header,
   info,
@@ -78,7 +78,7 @@ export async function executeAndCompleteTask(
   const executionLog: string[] = [];
 
   try {
-    const { execCwd, execPiece, isWorktree, branch, startMovement, retryNote, autoPr } = await resolveTaskExecution(task, cwd, pieceName);
+    const { execCwd, execPiece, isWorktree, branch, baseBranch, startMovement, retryNote, autoPr } = await resolveTaskExecution(task, cwd, pieceName);
 
     // cwd is always the project root; pass it as projectCwd so reports/sessions go there
     const taskSuccess = await executeTask({
@@ -115,6 +115,7 @@ export async function executeAndCompleteTask(
           branch,
           title: task.name.length > 100 ? `${task.name.slice(0, 97)}...` : task.name,
           body: prBody,
+          base: baseBranch,
         });
         if (prResult.success) {
           success(`PR created: ${prResult.url}`);
@@ -222,7 +223,7 @@ export async function resolveTaskExecution(
   task: TaskInfo,
   defaultCwd: string,
   defaultPiece: string
-): Promise<{ execCwd: string; execPiece: string; isWorktree: boolean; branch?: string; startMovement?: string; retryNote?: string; autoPr?: boolean }> {
+): Promise<{ execCwd: string; execPiece: string; isWorktree: boolean; branch?: string; baseBranch?: string; startMovement?: string; retryNote?: string; autoPr?: boolean }> {
   const data = task.data;
 
   // No structured data: use defaults
@@ -233,9 +234,11 @@ export async function resolveTaskExecution(
   let execCwd = defaultCwd;
   let isWorktree = false;
   let branch: string | undefined;
+  let baseBranch: string | undefined;
 
   // Handle worktree (now creates a shared clone)
   if (data.worktree) {
+    baseBranch = getCurrentBranch(defaultCwd);
     // Summarize task content to English slug using AI
     info('Generating branch name...');
     const taskSlug = await summarizeTaskName(task.content, { cwd: defaultCwd });
@@ -271,5 +274,5 @@ export async function resolveTaskExecution(
     autoPr = globalConfig.autoPr;
   }
 
-  return { execCwd, execPiece, isWorktree, branch, startMovement, retryNote, autoPr };
+  return { execCwd, execPiece, isWorktree, branch, baseBranch, startMovement, retryNote, autoPr };
 }

src/features/tasks/execute/types.ts

@@ -91,6 +91,7 @@ export interface WorktreeConfirmationResult {
   execCwd: string;
   isWorktree: boolean;
   branch?: string;
+  baseBranch?: string;
 }
 
 export interface SelectAndExecuteOptions {

src/infra/task/git.ts

@@ -4,6 +4,17 @@
 
 import { execFileSync } from 'node:child_process';
 
+/**
+ * Get the current branch name.
+ */
+export function getCurrentBranch(cwd: string): string {
+  return execFileSync('git', ['rev-parse', '--abbrev-ref', 'HEAD'], {
+    cwd,
+    encoding: 'utf-8',
+    stdio: 'pipe',
+  }).trim();
+}
+
 /**
  * Stage all changes and create a commit.
  * Returns the short commit hash if changes were committed, undefined if no changes.

src/infra/task/index.ts

@@ -43,7 +43,7 @@ export {
   getOriginalInstruction,
   buildListItems,
 } from './branchList.js';
-export { stageAndCommit } from './git.js';
+export { stageAndCommit, getCurrentBranch } from './git.js';
 export { autoCommitAndPush, type AutoCommitResult } from './autoCommit.js';
 export { summarizeTaskName } from './summarize.js';
 export { TaskWatcher, type TaskWatcherOptions } from './watcher.js';