feat: implement XML extraction utilities and enhance feature handling

- Introduced a new xml-extractor module with functions for XML parsing, including escaping/unescaping XML characters, extracting sections and elements, and managing implemented features.
- Added functionality to add, remove, update, and check for implemented features in the app_spec.txt file.
- Enhanced the create and update feature handlers to check for duplicate titles and trigger synchronization with app_spec.txt on status changes.
- Updated tests to cover new XML extraction utilities and feature handling logic, ensuring robust functionality and reliability.

apps/server/src/lib/app-spec-format.ts

@@ -13,7 +13,7 @@ export { specOutputSchema } from '@automaker/types';
  * Escape special XML characters
  * Handles undefined/null values by converting them to empty strings
  */
-function escapeXml(str: string | undefined | null): string {
+export function escapeXml(str: string | undefined | null): string {
   if (str == null) {
     return '';
   }

apps/server/src/lib/xml-extractor.ts

@@ -0,0 +1,466 @@
+/**
+ * XML Extraction Utilities
+ *
+ * Robust XML parsing utilities for extracting and updating sections
+ * from app_spec.txt XML content. Uses regex-based parsing which is
+ * sufficient for our controlled XML structure.
+ *
+ * Note: If more complex XML parsing is needed in the future, consider
+ * using a library like 'fast-xml-parser' or 'xml2js'.
+ */
+
+import { createLogger } from '@automaker/utils';
+import type { SpecOutput } from '@automaker/types';
+
+const logger = createLogger('XmlExtractor');
+
+/**
+ * Represents an implemented feature extracted from XML
+ */
+export interface ImplementedFeature {
+  name: string;
+  description: string;
+  file_locations?: string[];
+}
+
+/**
+ * Logger interface for optional custom logging
+ */
+export interface XmlExtractorLogger {
+  debug: (message: string, ...args: unknown[]) => void;
+  warn?: (message: string, ...args: unknown[]) => void;
+}
+
+/**
+ * Options for XML extraction operations
+ */
+export interface ExtractXmlOptions {
+  /** Custom logger (defaults to internal logger) */
+  logger?: XmlExtractorLogger;
+}
+
+/**
+ * Escape special XML characters
+ * Handles undefined/null values by converting them to empty strings
+ */
+export function escapeXml(str: string | undefined | null): string {
+  if (str == null) {
+    return '';
+  }
+  return str
+    .replace(/&/g, '&')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&apos;');
+}
+
+/**
+ * Unescape XML entities back to regular characters
+ */
+export function unescapeXml(str: string): string {
+  return str
+    .replace(/&apos;/g, "'")
+    .replace(/&quot;/g, '"')
+    .replace(/&gt;/g, '>')
+    .replace(/&lt;/g, '<')
+    .replace(/&amp;/g, '&');
+}
+
+/**
+ * Extract the content of a specific XML section
+ *
+ * @param xmlContent - The full XML content
+ * @param tagName - The tag name to extract (e.g., 'implemented_features')
+ * @param options - Optional extraction options
+ * @returns The content between the tags, or null if not found
+ */
+export function extractXmlSection(
+  xmlContent: string,
+  tagName: string,
+  options: ExtractXmlOptions = {}
+): string | null {
+  const log = options.logger || logger;
+
+  const regex = new RegExp(`<${tagName}>([\\s\\S]*?)<\\/${tagName}>`, 'i');
+  const match = xmlContent.match(regex);
+
+  if (match) {
+    log.debug(`Extracted <${tagName}> section`);
+    return match[1];
+  }
+
+  log.debug(`Section <${tagName}> not found`);
+  return null;
+}
+
+/**
+ * Extract all values from repeated XML elements
+ *
+ * @param xmlContent - The XML content to search
+ * @param tagName - The tag name to extract values from
+ * @param options - Optional extraction options
+ * @returns Array of extracted values (unescaped)
+ */
+export function extractXmlElements(
+  xmlContent: string,
+  tagName: string,
+  options: ExtractXmlOptions = {}
+): string[] {
+  const log = options.logger || logger;
+  const values: string[] = [];
+
+  const regex = new RegExp(`<${tagName}>(.*?)<\\/${tagName}>`, 'g');
+  const matches = xmlContent.matchAll(regex);
+
+  for (const match of matches) {
+    values.push(unescapeXml(match[1].trim()));
+  }
+
+  log.debug(`Extracted ${values.length} <${tagName}> elements`);
+  return values;
+}
+
+/**
+ * Extract implemented features from app_spec.txt XML content
+ *
+ * @param specContent - The full XML content of app_spec.txt
+ * @param options - Optional extraction options
+ * @returns Array of implemented features with name, description, and optional file_locations
+ */
+export function extractImplementedFeatures(
+  specContent: string,
+  options: ExtractXmlOptions = {}
+): ImplementedFeature[] {
+  const log = options.logger || logger;
+  const features: ImplementedFeature[] = [];
+
+  // Match <implemented_features>...</implemented_features> section
+  const implementedSection = extractXmlSection(specContent, 'implemented_features', options);
+
+  if (!implementedSection) {
+    log.debug('No implemented_features section found');
+    return features;
+  }
+
+  // Extract individual feature blocks
+  const featureRegex = /<feature>([\s\S]*?)<\/feature>/g;
+  const featureMatches = implementedSection.matchAll(featureRegex);
+
+  for (const featureMatch of featureMatches) {
+    const featureContent = featureMatch[1];
+
+    // Extract name
+    const nameMatch = featureContent.match(/<name>(.*?)<\/name>/);
+    const name = nameMatch ? unescapeXml(nameMatch[1].trim()) : '';
+
+    // Extract description
+    const descMatch = featureContent.match(/<description>(.*?)<\/description>/);
+    const description = descMatch ? unescapeXml(descMatch[1].trim()) : '';
+
+    // Extract file_locations if present
+    const locationsSection = extractXmlSection(featureContent, 'file_locations', options);
+    const file_locations = locationsSection
+      ? extractXmlElements(locationsSection, 'location', options)
+      : undefined;
+
+    if (name) {
+      features.push({
+        name,
+        description,
+        ...(file_locations && file_locations.length > 0 ? { file_locations } : {}),
+      });
+    }
+  }
+
+  log.debug(`Extracted ${features.length} implemented features`);
+  return features;
+}
+
+/**
+ * Extract only the feature names from implemented_features section
+ *
+ * @param specContent - The full XML content of app_spec.txt
+ * @param options - Optional extraction options
+ * @returns Array of feature names
+ */
+export function extractImplementedFeatureNames(
+  specContent: string,
+  options: ExtractXmlOptions = {}
+): string[] {
+  const features = extractImplementedFeatures(specContent, options);
+  return features.map((f) => f.name);
+}
+
+/**
+ * Generate XML for a single implemented feature
+ *
+ * @param feature - The feature to convert to XML
+ * @param indent - The base indentation level (default: 2 spaces)
+ * @returns XML string for the feature
+ */
+export function featureToXml(feature: ImplementedFeature, indent: string = '  '): string {
+  const i1 = indent;
+  const i2 = indent + indent;
+  const i3 = indent + indent + indent;
+  const i4 = indent + indent + indent + indent;
+
+  let xml = `${i2}<feature>
+${i3}<name>${escapeXml(feature.name)}</name>
+${i3}<description>${escapeXml(feature.description)}</description>`;
+
+  if (feature.file_locations && feature.file_locations.length > 0) {
+    xml += `
+${i3}<file_locations>
+${feature.file_locations.map((loc) => `${i4}<location>${escapeXml(loc)}</location>`).join('\n')}
+${i3}</file_locations>`;
+  }
+
+  xml += `
+${i2}</feature>`;
+
+  return xml;
+}
+
+/**
+ * Generate XML for an array of implemented features
+ *
+ * @param features - Array of features to convert to XML
+ * @param indent - The base indentation level (default: 2 spaces)
+ * @returns XML string for the implemented_features section content
+ */
+export function featuresToXml(features: ImplementedFeature[], indent: string = '  '): string {
+  return features.map((f) => featureToXml(f, indent)).join('\n');
+}
+
+/**
+ * Update the implemented_features section in XML content
+ *
+ * @param specContent - The full XML content
+ * @param newFeatures - The new features to set
+ * @param options - Optional extraction options
+ * @returns Updated XML content with the new implemented_features section
+ */
+export function updateImplementedFeaturesSection(
+  specContent: string,
+  newFeatures: ImplementedFeature[],
+  options: ExtractXmlOptions = {}
+): string {
+  const log = options.logger || logger;
+  const indent = '  ';
+
+  // Generate new section content
+  const newSectionContent = featuresToXml(newFeatures, indent);
+
+  // Build the new section
+  const newSection = `<implemented_features>
+${newSectionContent}
+${indent}</implemented_features>`;
+
+  // Check if section exists
+  const sectionRegex = /<implemented_features>[\s\S]*?<\/implemented_features>/;
+
+  if (sectionRegex.test(specContent)) {
+    log.debug('Replacing existing implemented_features section');
+    return specContent.replace(sectionRegex, newSection);
+  }
+
+  // If section doesn't exist, try to insert after core_capabilities
+  const coreCapabilitiesEnd = '</core_capabilities>';
+  const insertIndex = specContent.indexOf(coreCapabilitiesEnd);
+
+  if (insertIndex !== -1) {
+    const insertPosition = insertIndex + coreCapabilitiesEnd.length;
+    log.debug('Inserting implemented_features after core_capabilities');
+    return (
+      specContent.slice(0, insertPosition) +
+      '\n\n' +
+      indent +
+      newSection +
+      specContent.slice(insertPosition)
+    );
+  }
+
+  // As a fallback, insert before </project_specification>
+  const projectSpecEnd = '</project_specification>';
+  const fallbackIndex = specContent.indexOf(projectSpecEnd);
+
+  if (fallbackIndex !== -1) {
+    log.debug('Inserting implemented_features before </project_specification>');
+    return (
+      specContent.slice(0, fallbackIndex) +
+      indent +
+      newSection +
+      '\n' +
+      specContent.slice(fallbackIndex)
+    );
+  }
+
+  log.warn?.('Could not find appropriate insertion point for implemented_features');
+  log.debug('Could not find appropriate insertion point for implemented_features');
+  return specContent;
+}
+
+/**
+ * Add a new feature to the implemented_features section
+ *
+ * @param specContent - The full XML content
+ * @param newFeature - The feature to add
+ * @param options - Optional extraction options
+ * @returns Updated XML content with the new feature added
+ */
+export function addImplementedFeature(
+  specContent: string,
+  newFeature: ImplementedFeature,
+  options: ExtractXmlOptions = {}
+): string {
+  const log = options.logger || logger;
+
+  // Extract existing features
+  const existingFeatures = extractImplementedFeatures(specContent, options);
+
+  // Check for duplicates by name
+  const isDuplicate = existingFeatures.some(
+    (f) => f.name.toLowerCase() === newFeature.name.toLowerCase()
+  );
+
+  if (isDuplicate) {
+    log.debug(`Feature "${newFeature.name}" already exists, skipping`);
+    return specContent;
+  }
+
+  // Add the new feature
+  const updatedFeatures = [...existingFeatures, newFeature];
+
+  log.debug(`Adding feature "${newFeature.name}"`);
+  return updateImplementedFeaturesSection(specContent, updatedFeatures, options);
+}
+
+/**
+ * Remove a feature from the implemented_features section by name
+ *
+ * @param specContent - The full XML content
+ * @param featureName - The name of the feature to remove
+ * @param options - Optional extraction options
+ * @returns Updated XML content with the feature removed
+ */
+export function removeImplementedFeature(
+  specContent: string,
+  featureName: string,
+  options: ExtractXmlOptions = {}
+): string {
+  const log = options.logger || logger;
+
+  // Extract existing features
+  const existingFeatures = extractImplementedFeatures(specContent, options);
+
+  // Filter out the feature to remove
+  const updatedFeatures = existingFeatures.filter(
+    (f) => f.name.toLowerCase() !== featureName.toLowerCase()
+  );
+
+  if (updatedFeatures.length === existingFeatures.length) {
+    log.debug(`Feature "${featureName}" not found, no changes made`);
+    return specContent;
+  }
+
+  log.debug(`Removing feature "${featureName}"`);
+  return updateImplementedFeaturesSection(specContent, updatedFeatures, options);
+}
+
+/**
+ * Update an existing feature in the implemented_features section
+ *
+ * @param specContent - The full XML content
+ * @param featureName - The name of the feature to update
+ * @param updates - Partial updates to apply to the feature
+ * @param options - Optional extraction options
+ * @returns Updated XML content with the feature modified
+ */
+export function updateImplementedFeature(
+  specContent: string,
+  featureName: string,
+  updates: Partial<ImplementedFeature>,
+  options: ExtractXmlOptions = {}
+): string {
+  const log = options.logger || logger;
+
+  // Extract existing features
+  const existingFeatures = extractImplementedFeatures(specContent, options);
+
+  // Find and update the feature
+  let found = false;
+  const updatedFeatures = existingFeatures.map((f) => {
+    if (f.name.toLowerCase() === featureName.toLowerCase()) {
+      found = true;
+      return {
+        ...f,
+        ...updates,
+        // Preserve the original name if not explicitly updated
+        name: updates.name ?? f.name,
+      };
+    }
+    return f;
+  });
+
+  if (!found) {
+    log.debug(`Feature "${featureName}" not found, no changes made`);
+    return specContent;
+  }
+
+  log.debug(`Updating feature "${featureName}"`);
+  return updateImplementedFeaturesSection(specContent, updatedFeatures, options);
+}
+
+/**
+ * Check if a feature exists in the implemented_features section
+ *
+ * @param specContent - The full XML content
+ * @param featureName - The name of the feature to check
+ * @param options - Optional extraction options
+ * @returns True if the feature exists
+ */
+export function hasImplementedFeature(
+  specContent: string,
+  featureName: string,
+  options: ExtractXmlOptions = {}
+): boolean {
+  const features = extractImplementedFeatures(specContent, options);
+  return features.some((f) => f.name.toLowerCase() === featureName.toLowerCase());
+}
+
+/**
+ * Convert extracted features to SpecOutput.implemented_features format
+ *
+ * @param features - Array of extracted features
+ * @returns Features in SpecOutput format
+ */
+export function toSpecOutputFeatures(
+  features: ImplementedFeature[]
+): SpecOutput['implemented_features'] {
+  return features.map((f) => ({
+    name: f.name,
+    description: f.description,
+    ...(f.file_locations && f.file_locations.length > 0
+      ? { file_locations: f.file_locations }
+      : {}),
+  }));
+}
+
+/**
+ * Convert SpecOutput.implemented_features to ImplementedFeature format
+ *
+ * @param specFeatures - Features from SpecOutput
+ * @returns Features in ImplementedFeature format
+ */
+export function fromSpecOutputFeatures(
+  specFeatures: SpecOutput['implemented_features']
+): ImplementedFeature[] {
+  return specFeatures.map((f) => ({
+    name: f.name,
+    description: f.description,
+    ...(f.file_locations && f.file_locations.length > 0
+      ? { file_locations: f.file_locations }
+      : {}),
+  }));
+}

apps/server/src/routes/features/routes/create.ts

@@ -23,6 +23,19 @@ export function createCreateHandler(featureLoader: FeatureLoader) {
         return;
       }
 
+      // Check for duplicate title if title is provided
+      if (feature.title && feature.title.trim()) {
+        const duplicate = await featureLoader.findDuplicateTitle(projectPath, feature.title);
+        if (duplicate) {
+          res.status(409).json({
+            success: false,
+            error: `A feature with title "${feature.title}" already exists`,
+            duplicateFeatureId: duplicate.id,
+          });
+          return;
+        }
+      }
+
       const created = await featureLoader.create(projectPath, feature);
       res.json({ success: true, feature: created });
     } catch (error) {

apps/server/src/routes/features/routes/update.ts

@@ -4,8 +4,14 @@
 
 import type { Request, Response } from 'express';
 import { FeatureLoader } from '../../../services/feature-loader.js';
-import type { Feature } from '@automaker/types';
+import type { Feature, FeatureStatus } from '@automaker/types';
 import { getErrorMessage, logError } from '../common.js';
+import { createLogger } from '@automaker/utils';
+
+const logger = createLogger('features/update');
+
+// Statuses that should trigger syncing to app_spec.txt
+const SYNC_TRIGGER_STATUSES: FeatureStatus[] = ['verified', 'completed'];
 
 export function createUpdateHandler(featureLoader: FeatureLoader) {
   return async (req: Request, res: Response): Promise<void> => {
@@ -34,6 +40,28 @@ export function createUpdateHandler(featureLoader: FeatureLoader) {
         return;
       }
 
+      // Check for duplicate title if title is being updated
+      if (updates.title && updates.title.trim()) {
+        const duplicate = await featureLoader.findDuplicateTitle(
+          projectPath,
+          updates.title,
+          featureId // Exclude the current feature from duplicate check
+        );
+        if (duplicate) {
+          res.status(409).json({
+            success: false,
+            error: `A feature with title "${updates.title}" already exists`,
+            duplicateFeatureId: duplicate.id,
+          });
+          return;
+        }
+      }
+
+      // Get the current feature to detect status changes
+      const currentFeature = await featureLoader.get(projectPath, featureId);
+      const previousStatus = currentFeature?.status as FeatureStatus | undefined;
+      const newStatus = updates.status as FeatureStatus | undefined;
+
       const updated = await featureLoader.update(
         projectPath,
         featureId,
@@ -42,6 +70,22 @@ export function createUpdateHandler(featureLoader: FeatureLoader) {
         enhancementMode,
         preEnhancementDescription
       );
+
+      // Trigger sync to app_spec.txt when status changes to verified or completed
+      if (newStatus && SYNC_TRIGGER_STATUSES.includes(newStatus) && previousStatus !== newStatus) {
+        try {
+          const synced = await featureLoader.syncFeatureToAppSpec(projectPath, updated);
+          if (synced) {
+            logger.info(
+              `Synced feature "${updated.title || updated.id}" to app_spec.txt on status change to ${newStatus}`
+            );
+          }
+        } catch (syncError) {
+          // Log the sync error but don't fail the update operation
+          logger.error(`Failed to sync feature to app_spec.txt:`, syncError);
+        }
+      }
+
       res.json({ success: true, feature: updated });
     } catch (error) {
       logError(error, 'Update feature failed');

apps/server/src/services/auto-mode-service.ts

@@ -2101,6 +2101,16 @@ Format your response as a structured markdown document.`;
         feature.justFinishedAt = undefined;
       }
       await secureFs.writeFile(featurePath, JSON.stringify(feature, null, 2));
+
+      // Sync completed/verified features to app_spec.txt
+      if (status === 'verified' || status === 'completed') {
+        try {
+          await this.featureLoader.syncFeatureToAppSpec(projectPath, feature);
+        } catch (syncError) {
+          // Log but don't fail the status update if sync fails
+          logger.warn(`Failed to sync feature ${featureId} to app_spec.txt:`, syncError);
+        }
+      }
     } catch {
       // Feature file may not exist
     }

apps/server/src/services/feature-loader.ts

@@ -11,8 +11,10 @@ import {
   getFeaturesDir,
   getFeatureDir,
   getFeatureImagesDir,
+  getAppSpecPath,
   ensureAutomakerDir,
 } from '@automaker/platform';
+import { addImplementedFeature, type ImplementedFeature } from '../lib/xml-extractor.js';
 
 const logger = createLogger('FeatureLoader');
 
@@ -236,6 +238,69 @@ export class FeatureLoader {
     }
   }
 
+  /**
+   * Normalize a title for comparison (case-insensitive, trimmed)
+   */
+  private normalizeTitle(title: string): string {
+    return title.toLowerCase().trim();
+  }
+
+  /**
+   * Find a feature by its title (case-insensitive match)
+   * @param projectPath - Path to the project
+   * @param title - Title to search for
+   * @returns The matching feature or null if not found
+   */
+  async findByTitle(projectPath: string, title: string): Promise<Feature | null> {
+    if (!title || !title.trim()) {
+      return null;
+    }
+
+    const normalizedTitle = this.normalizeTitle(title);
+    const features = await this.getAll(projectPath);
+
+    for (const feature of features) {
+      if (feature.title && this.normalizeTitle(feature.title) === normalizedTitle) {
+        return feature;
+      }
+    }
+
+    return null;
+  }
+
+  /**
+   * Check if a title already exists on another feature (for duplicate detection)
+   * @param projectPath - Path to the project
+   * @param title - Title to check
+   * @param excludeFeatureId - Optional feature ID to exclude from the check (for updates)
+   * @returns The duplicate feature if found, null otherwise
+   */
+  async findDuplicateTitle(
+    projectPath: string,
+    title: string,
+    excludeFeatureId?: string
+  ): Promise<Feature | null> {
+    if (!title || !title.trim()) {
+      return null;
+    }
+
+    const normalizedTitle = this.normalizeTitle(title);
+    const features = await this.getAll(projectPath);
+
+    for (const feature of features) {
+      // Skip the feature being updated (if provided)
+      if (excludeFeatureId && feature.id === excludeFeatureId) {
+        continue;
+      }
+
+      if (feature.title && this.normalizeTitle(feature.title) === normalizedTitle) {
+        return feature;
+      }
+    }
+
+    return null;
+  }
+
   /**
    * Get a single feature by ID
    */
@@ -460,4 +525,64 @@ export class FeatureLoader {
       }
     }
   }
+
+  /**
+   * Sync a completed feature to the app_spec.txt implemented_features section
+   *
+   * When a feature is completed, this method adds it to the implemented_features
+   * section of the project's app_spec.txt file. This keeps the spec in sync
+   * with the actual state of the codebase.
+   *
+   * @param projectPath - Path to the project
+   * @param feature - The feature to sync (must have title or description)
+   * @param fileLocations - Optional array of file paths where the feature was implemented
+   * @returns True if the spec was updated, false if no spec exists or feature was skipped
+   */
+  async syncFeatureToAppSpec(
+    projectPath: string,
+    feature: Feature,
+    fileLocations?: string[]
+  ): Promise<boolean> {
+    try {
+      const appSpecPath = getAppSpecPath(projectPath);
+
+      // Read the current app_spec.txt
+      let specContent: string;
+      try {
+        specContent = (await secureFs.readFile(appSpecPath, 'utf-8')) as string;
+      } catch (error) {
+        if ((error as NodeJS.ErrnoException).code === 'ENOENT') {
+          logger.info(`No app_spec.txt found for project, skipping sync for feature ${feature.id}`);
+          return false;
+        }
+        throw error;
+      }
+
+      // Build the implemented feature entry
+      const featureName = feature.title || `Feature: ${feature.id}`;
+      const implementedFeature: ImplementedFeature = {
+        name: featureName,
+        description: feature.description,
+        ...(fileLocations && fileLocations.length > 0 ? { file_locations: fileLocations } : {}),
+      };
+
+      // Add the feature to the implemented_features section
+      const updatedSpecContent = addImplementedFeature(specContent, implementedFeature);
+
+      // Check if the content actually changed (feature might already exist)
+      if (updatedSpecContent === specContent) {
+        logger.info(`Feature "${featureName}" already exists in app_spec.txt, skipping`);
+        return false;
+      }
+
+      // Write the updated spec back to the file
+      await secureFs.writeFile(appSpecPath, updatedSpecContent, 'utf-8');
+
+      logger.info(`Synced feature "${featureName}" to app_spec.txt`);
+      return true;
+    } catch (error) {
+      logger.error(`Failed to sync feature ${feature.id} to app_spec.txt:`, error);
+      throw error;
+    }
+  }
 }

apps/server/tests/unit/services/feature-loader.test.ts

@@ -442,4 +442,471 @@ describe('feature-loader.ts', () => {
       );
     });
   });
+
+  describe('findByTitle', () => {
+    it('should find feature by exact title match (case-insensitive)', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+        { name: 'feature-2', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile)
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-1000-abc',
+            title: 'Login Feature',
+            category: 'auth',
+            description: 'Login implementation',
+          })
+        )
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-2000-def',
+            title: 'Logout Feature',
+            category: 'auth',
+            description: 'Logout implementation',
+          })
+        );
+
+      const result = await loader.findByTitle(testProjectPath, 'LOGIN FEATURE');
+
+      expect(result).not.toBeNull();
+      expect(result?.id).toBe('feature-1000-abc');
+      expect(result?.title).toBe('Login Feature');
+    });
+
+    it('should return null when title is not found', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile).mockResolvedValueOnce(
+        JSON.stringify({
+          id: 'feature-1000-abc',
+          title: 'Login Feature',
+          category: 'auth',
+          description: 'Login implementation',
+        })
+      );
+
+      const result = await loader.findByTitle(testProjectPath, 'Nonexistent Feature');
+
+      expect(result).toBeNull();
+    });
+
+    it('should return null for empty or whitespace title', async () => {
+      const result1 = await loader.findByTitle(testProjectPath, '');
+      const result2 = await loader.findByTitle(testProjectPath, '   ');
+
+      expect(result1).toBeNull();
+      expect(result2).toBeNull();
+    });
+
+    it('should skip features without titles', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+        { name: 'feature-2', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile)
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-1000-abc',
+            // no title
+            category: 'auth',
+            description: 'Login implementation',
+          })
+        )
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-2000-def',
+            title: 'Login Feature',
+            category: 'auth',
+            description: 'Another login',
+          })
+        );
+
+      const result = await loader.findByTitle(testProjectPath, 'Login Feature');
+
+      expect(result).not.toBeNull();
+      expect(result?.id).toBe('feature-2000-def');
+    });
+  });
+
+  describe('findDuplicateTitle', () => {
+    it('should find duplicate title', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile).mockResolvedValueOnce(
+        JSON.stringify({
+          id: 'feature-1000-abc',
+          title: 'My Feature',
+          category: 'ui',
+          description: 'Feature description',
+        })
+      );
+
+      const result = await loader.findDuplicateTitle(testProjectPath, 'my feature');
+
+      expect(result).not.toBeNull();
+      expect(result?.id).toBe('feature-1000-abc');
+    });
+
+    it('should exclude specified feature ID from duplicate check', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+        { name: 'feature-2', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile)
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-1000-abc',
+            title: 'My Feature',
+            category: 'ui',
+            description: 'Feature 1',
+          })
+        )
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-2000-def',
+            title: 'Other Feature',
+            category: 'ui',
+            description: 'Feature 2',
+          })
+        );
+
+      // Should not find duplicate when excluding the feature that has the title
+      const result = await loader.findDuplicateTitle(
+        testProjectPath,
+        'My Feature',
+        'feature-1000-abc'
+      );
+
+      expect(result).toBeNull();
+    });
+
+    it('should find duplicate when title exists on different feature', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+        { name: 'feature-2', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile)
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-1000-abc',
+            title: 'My Feature',
+            category: 'ui',
+            description: 'Feature 1',
+          })
+        )
+        .mockResolvedValueOnce(
+          JSON.stringify({
+            id: 'feature-2000-def',
+            title: 'Other Feature',
+            category: 'ui',
+            description: 'Feature 2',
+          })
+        );
+
+      // Should find duplicate because feature-1000-abc has the title and we're excluding feature-2000-def
+      const result = await loader.findDuplicateTitle(
+        testProjectPath,
+        'My Feature',
+        'feature-2000-def'
+      );
+
+      expect(result).not.toBeNull();
+      expect(result?.id).toBe('feature-1000-abc');
+    });
+
+    it('should return null for empty or whitespace title', async () => {
+      const result1 = await loader.findDuplicateTitle(testProjectPath, '');
+      const result2 = await loader.findDuplicateTitle(testProjectPath, '   ');
+
+      expect(result1).toBeNull();
+      expect(result2).toBeNull();
+    });
+
+    it('should handle titles with leading/trailing whitespace', async () => {
+      vi.mocked(fs.access).mockResolvedValue(undefined);
+      vi.mocked(fs.readdir).mockResolvedValue([
+        { name: 'feature-1', isDirectory: () => true } as any,
+      ]);
+
+      vi.mocked(fs.readFile).mockResolvedValueOnce(
+        JSON.stringify({
+          id: 'feature-1000-abc',
+          title: 'My Feature',
+          category: 'ui',
+          description: 'Feature description',
+        })
+      );
+
+      const result = await loader.findDuplicateTitle(testProjectPath, '  My Feature  ');
+
+      expect(result).not.toBeNull();
+      expect(result?.id).toBe('feature-1000-abc');
+    });
+  });
+
+  describe('syncFeatureToAppSpec', () => {
+    const sampleAppSpec = `<?xml version="1.0" encoding="UTF-8"?>
+<project_specification>
+  <project_name>Test Project</project_name>
+  <core_capabilities>
+    <capability>Testing</capability>
+  </core_capabilities>
+  <implemented_features>
+    <feature>
+      <name>Existing Feature</name>
+      <description>Already implemented</description>
+    </feature>
+  </implemented_features>
+</project_specification>`;
+
+    const appSpecWithoutFeatures = `<?xml version="1.0" encoding="UTF-8"?>
+<project_specification>
+  <project_name>Test Project</project_name>
+  <core_capabilities>
+    <capability>Testing</capability>
+  </core_capabilities>
+</project_specification>`;
+
+    it('should add feature to app_spec.txt', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'New Feature',
+        category: 'ui',
+        description: 'A new feature description',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(true);
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.stringContaining('app_spec.txt'),
+        expect.stringContaining('New Feature'),
+        'utf-8'
+      );
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('A new feature description'),
+        'utf-8'
+      );
+    });
+
+    it('should add feature with file locations', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'Feature With Locations',
+        category: 'backend',
+        description: 'Feature with file locations',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature, [
+        'src/feature.ts',
+        'src/utils/helper.ts',
+      ]);
+
+      expect(result).toBe(true);
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('src/feature.ts'),
+        'utf-8'
+      );
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('src/utils/helper.ts'),
+        'utf-8'
+      );
+    });
+
+    it('should return false when app_spec.txt does not exist', async () => {
+      const error: any = new Error('File not found');
+      error.code = 'ENOENT';
+      vi.mocked(fs.readFile).mockRejectedValueOnce(error);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'New Feature',
+        category: 'ui',
+        description: 'A new feature description',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(false);
+      expect(fs.writeFile).not.toHaveBeenCalled();
+    });
+
+    it('should return false when feature already exists (duplicate)', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+
+      const feature = {
+        id: 'feature-5678-xyz',
+        title: 'Existing Feature', // Same name as existing feature
+        category: 'ui',
+        description: 'Different description',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(false);
+      expect(fs.writeFile).not.toHaveBeenCalled();
+    });
+
+    it('should use feature ID as fallback name when title is missing', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        category: 'ui',
+        description: 'Feature without title',
+        // No title property
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(true);
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('Feature: feature-1234-abc'),
+        'utf-8'
+      );
+    });
+
+    it('should handle app_spec without implemented_features section', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(appSpecWithoutFeatures);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'First Feature',
+        category: 'ui',
+        description: 'First implemented feature',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(true);
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('<implemented_features>'),
+        'utf-8'
+      );
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('First Feature'),
+        'utf-8'
+      );
+    });
+
+    it('should throw on non-ENOENT file read errors', async () => {
+      const error = new Error('Permission denied');
+      vi.mocked(fs.readFile).mockRejectedValueOnce(error);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'New Feature',
+        category: 'ui',
+        description: 'A new feature description',
+      };
+
+      await expect(loader.syncFeatureToAppSpec(testProjectPath, feature)).rejects.toThrow(
+        'Permission denied'
+      );
+    });
+
+    it('should preserve existing features when adding a new one', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'New Feature',
+        category: 'ui',
+        description: 'A new feature',
+      };
+
+      await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      // Verify both old and new features are in the output
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('Existing Feature'),
+        'utf-8'
+      );
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('New Feature'),
+        'utf-8'
+      );
+    });
+
+    it('should escape special characters in feature name and description', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'Feature with <special> & "chars"',
+        category: 'ui',
+        description: 'Description with <tags> & "quotes"',
+      };
+
+      const result = await loader.syncFeatureToAppSpec(testProjectPath, feature);
+
+      expect(result).toBe(true);
+      // The XML should have escaped characters
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('&lt;special&gt;'),
+        'utf-8'
+      );
+      expect(fs.writeFile).toHaveBeenCalledWith(
+        expect.any(String),
+        expect.stringContaining('&amp;'),
+        'utf-8'
+      );
+    });
+
+    it('should not add empty file_locations array', async () => {
+      vi.mocked(fs.readFile).mockResolvedValueOnce(sampleAppSpec);
+      vi.mocked(fs.writeFile).mockResolvedValue(undefined);
+
+      const feature = {
+        id: 'feature-1234-abc',
+        title: 'Feature Without Locations',
+        category: 'ui',
+        description: 'No file locations',
+      };
+
+      await loader.syncFeatureToAppSpec(testProjectPath, feature, []);
+
+      // File locations should not be included when array is empty
+      const writeCall = vi.mocked(fs.writeFile).mock.calls[0];
+      const writtenContent = writeCall[1] as string;
+
+      // Count occurrences of file_locations - should only have the one from Existing Feature if any
+      // The new feature should not add file_locations
+      expect(writtenContent).toContain('Feature Without Locations');
+    });
+  });
 });