feat: Add AI-generated commit messages

Integrate Claude Haiku to automatically generate commit messages when
committing worktree changes. Shows a sparkle animation while generating
and auto-populates the commit message field.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/server/src/routes/worktree/index.ts

@@ -17,6 +17,7 @@ import { createDeleteHandler } from './routes/delete.js';
 import { createCreatePRHandler } from './routes/create-pr.js';
 import { createPRInfoHandler } from './routes/pr-info.js';
 import { createCommitHandler } from './routes/commit.js';
+import { createGenerateCommitMessageHandler } from './routes/generate-commit-message.js';
 import { createPushHandler } from './routes/push.js';
 import { createPullHandler } from './routes/pull.js';
 import { createCheckoutBranchHandler } from './routes/checkout-branch.js';
@@ -64,6 +65,12 @@ export function createWorktreeRoutes(events: EventEmitter): Router {
     requireGitRepoOnly,
     createCommitHandler()
   );
+  router.post(
+    '/generate-commit-message',
+    validatePathParams('worktreePath'),
+    requireGitRepoOnly,
+    createGenerateCommitMessageHandler()
+  );
   router.post(
     '/push',
     validatePathParams('worktreePath'),

apps/server/src/routes/worktree/routes/generate-commit-message.ts

@@ -0,0 +1,178 @@
+/**
+ * POST /worktree/generate-commit-message endpoint - Generate an AI commit message from git diff
+ *
+ * Uses Claude Haiku to generate a concise, conventional commit message from git changes.
+ */
+
+import type { Request, Response } from 'express';
+import { exec } from 'child_process';
+import { promisify } from 'util';
+import { query } from '@anthropic-ai/claude-agent-sdk';
+import { createLogger } from '@automaker/utils';
+import { CLAUDE_MODEL_MAP } from '@automaker/model-resolver';
+import { getErrorMessage, logError } from '../common.js';
+
+const logger = createLogger('GenerateCommitMessage');
+const execAsync = promisify(exec);
+
+interface GenerateCommitMessageRequestBody {
+  worktreePath: string;
+}
+
+interface GenerateCommitMessageSuccessResponse {
+  success: true;
+  message: string;
+}
+
+interface GenerateCommitMessageErrorResponse {
+  success: false;
+  error: string;
+}
+
+const SYSTEM_PROMPT = `You are a git commit message generator. Your task is to create a clear, concise commit message based on the git diff provided.
+
+Rules:
+- Output ONLY the commit message, nothing else
+- First line should be a short summary (50 chars or less) in imperative mood
+- Start with a conventional commit type if appropriate (feat:, fix:, refactor:, docs:, etc.)
+- Keep it concise and descriptive
+- Focus on WHAT changed and WHY (if clear from the diff), not HOW
+- No quotes, backticks, or extra formatting
+- If there are multiple changes, provide a brief summary on the first line
+
+Examples:
+- feat: Add dark mode toggle to settings
+- fix: Resolve login validation edge case
+- refactor: Extract user authentication logic
+- docs: Update installation instructions`;
+
+async function extractTextFromStream(
+  stream: AsyncIterable<{
+    type: string;
+    subtype?: string;
+    result?: string;
+    message?: {
+      content?: Array<{ type: string; text?: string }>;
+    };
+  }>
+): Promise<string> {
+  let responseText = '';
+
+  for await (const msg of stream) {
+    if (msg.type === 'assistant' && msg.message?.content) {
+      for (const block of msg.message.content) {
+        if (block.type === 'text' && block.text) {
+          responseText += block.text;
+        }
+      }
+    } else if (msg.type === 'result' && msg.subtype === 'success') {
+      responseText = msg.result || responseText;
+    }
+  }
+
+  return responseText;
+}
+
+export function createGenerateCommitMessageHandler(): (
+  req: Request,
+  res: Response
+) => Promise<void> {
+  return async (req: Request, res: Response): Promise<void> => {
+    try {
+      const { worktreePath } = req.body as GenerateCommitMessageRequestBody;
+
+      if (!worktreePath || typeof worktreePath !== 'string') {
+        const response: GenerateCommitMessageErrorResponse = {
+          success: false,
+          error: 'worktreePath is required and must be a string',
+        };
+        res.status(400).json(response);
+        return;
+      }
+
+      logger.info(`Generating commit message for worktree: ${worktreePath}`);
+
+      // Get git diff of staged and unstaged changes
+      let diff = '';
+      try {
+        // First try to get staged changes
+        const { stdout: stagedDiff } = await execAsync('git diff --cached', {
+          cwd: worktreePath,
+          maxBuffer: 1024 * 1024 * 5, // 5MB buffer
+        });
+
+        // If no staged changes, get unstaged changes
+        if (!stagedDiff.trim()) {
+          const { stdout: unstagedDiff } = await execAsync('git diff', {
+            cwd: worktreePath,
+            maxBuffer: 1024 * 1024 * 5, // 5MB buffer
+          });
+          diff = unstagedDiff;
+        } else {
+          diff = stagedDiff;
+        }
+      } catch (error) {
+        logger.error('Failed to get git diff:', error);
+        const response: GenerateCommitMessageErrorResponse = {
+          success: false,
+          error: 'Failed to get git changes',
+        };
+        res.status(500).json(response);
+        return;
+      }
+
+      if (!diff.trim()) {
+        const response: GenerateCommitMessageErrorResponse = {
+          success: false,
+          error: 'No changes to commit',
+        };
+        res.status(400).json(response);
+        return;
+      }
+
+      // Truncate diff if too long (keep first 10000 characters to avoid token limits)
+      const truncatedDiff =
+        diff.length > 10000 ? diff.substring(0, 10000) + '\n\n[... diff truncated ...]' : diff;
+
+      const userPrompt = `Generate a commit message for these changes:\n\n\`\`\`diff\n${truncatedDiff}\n\`\`\``;
+
+      const stream = query({
+        prompt: userPrompt,
+        options: {
+          model: CLAUDE_MODEL_MAP.haiku,
+          systemPrompt: SYSTEM_PROMPT,
+          maxTurns: 1,
+          allowedTools: [],
+          permissionMode: 'default',
+        },
+      });
+
+      const message = await extractTextFromStream(stream);
+
+      if (!message || message.trim().length === 0) {
+        logger.warn('Received empty response from Claude');
+        const response: GenerateCommitMessageErrorResponse = {
+          success: false,
+          error: 'Failed to generate commit message - empty response',
+        };
+        res.status(500).json(response);
+        return;
+      }
+
+      logger.info(`Generated commit message: ${message.trim().substring(0, 100)}...`);
+
+      const response: GenerateCommitMessageSuccessResponse = {
+        success: true,
+        message: message.trim(),
+      };
+      res.json(response);
+    } catch (error) {
+      logError(error, 'Generate commit message failed');
+      const response: GenerateCommitMessageErrorResponse = {
+        success: false,
+        error: getErrorMessage(error),
+      };
+      res.status(500).json(response);
+    }
+  };
+}