fix: make FTS5 optional for template search (fixes Claude Desktop compatibility)

- Added runtime FTS5 detection in database adapters
- Removed FTS5 from required schema to prevent "no such module" errors
- FTS5 tables/triggers created conditionally only if supported
- Template search automatically falls back to LIKE when FTS5 unavailable
- Works in ALL SQLite environments (Claude Desktop, restricted envs, etc.)

This ensures search_templates() works correctly regardless of SQLite build,
while still providing optimal performance when FTS5 is available.

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

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

docs/CHANGELOG.md

@@ -25,6 +25,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Removed unnecessary searchInfo messages that appeared on every search
   - Fixed HTTP node type comparison case sensitivity issue
   - Implemented relevance-based ranking with special boosting for primary nodes
+- **search_templates FTS5 Error**: Fixed "no such module: fts5" error in environments without FTS5 support (fixes Claude Desktop issue)
+  - Made FTS5 completely optional - detects support at runtime
+  - Removed FTS5 from required schema to prevent initialization failures
+  - Automatically falls back to LIKE search when FTS5 is unavailable
+  - FTS5 tables and triggers created conditionally only if supported
+  - Template search now works in ALL SQLite environments
 
 ### Added
 - **FTS5 Full-Text Search**: Added SQLite FTS5 support for faster and more intelligent node searching
@@ -32,6 +38,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Supports advanced search modes: OR (default), AND (all terms required), FUZZY (typo-tolerant)
   - Significantly improves search performance for large databases
   - FUZZY mode now uses edit distance (Levenshtein) for better typo tolerance
+- **FTS5 Detection**: Added runtime detection of FTS5 support
+  - `checkFTS5Support()` method in database adapters
+  - Conditional initialization of FTS5 features
+  - Graceful degradation when FTS5 not available
 
 ## [Unreleased]
 

src/database/database-adapter.ts

@@ -13,6 +13,7 @@ export interface DatabaseAdapter {
   pragma(key: string, value?: any): any;
   readonly inTransaction: boolean;
   transaction<T>(fn: () => T): T;
+  checkFTS5Support(): boolean;
 }
 
 export interface PreparedStatement {
@@ -174,6 +175,17 @@ class BetterSQLiteAdapter implements DatabaseAdapter {
   transaction<T>(fn: () => T): T {
     return this.db.transaction(fn)();
   }
+  
+  checkFTS5Support(): boolean {
+    try {
+      // Test if FTS5 is available
+      this.exec("CREATE VIRTUAL TABLE IF NOT EXISTS test_fts5 USING fts5(content);");
+      this.exec("DROP TABLE IF EXISTS test_fts5;");
+      return true;
+    } catch (error) {
+      return false;
+    }
+  }
 }
 
 /**
@@ -234,6 +246,18 @@ class SQLJSAdapter implements DatabaseAdapter {
     }
   }
   
+  checkFTS5Support(): boolean {
+    try {
+      // Test if FTS5 is available
+      this.exec("CREATE VIRTUAL TABLE IF NOT EXISTS test_fts5 USING fts5(content);");
+      this.exec("DROP TABLE IF EXISTS test_fts5;");
+      return true;
+    } catch (error) {
+      // sql.js doesn't support FTS5
+      return false;
+    }
+  }
+  
   private scheduleSave(): void {
     if (this.saveTimer) {
       clearTimeout(this.saveTimer);

src/database/schema.sql

@@ -47,7 +47,5 @@ CREATE INDEX IF NOT EXISTS idx_template_nodes ON templates(nodes_used);
 CREATE INDEX IF NOT EXISTS idx_template_updated ON templates(updated_at);
 CREATE INDEX IF NOT EXISTS idx_template_name ON templates(name);
 
--- Full-text search for templates
-CREATE VIRTUAL TABLE IF NOT EXISTS templates_fts USING fts5(
-  name, description, content=templates
-);
+-- Note: FTS5 tables are created conditionally at runtime if FTS5 is supported
+-- See template-repository.ts initializeFTS5() method

src/templates/template-repository.ts

@@ -23,9 +23,57 @@ export interface StoredTemplate {
 
 export class TemplateRepository {
   private sanitizer: TemplateSanitizer;
+  private hasFTS5Support: boolean = false;
   
   constructor(private db: DatabaseAdapter) {
     this.sanitizer = new TemplateSanitizer();
+    this.initializeFTS5();
+  }
+  
+  /**
+   * Initialize FTS5 tables if supported
+   */
+  private initializeFTS5(): void {
+    this.hasFTS5Support = this.db.checkFTS5Support();
+    
+    if (this.hasFTS5Support) {
+      try {
+        // Create FTS5 virtual table
+        this.db.exec(`
+          CREATE VIRTUAL TABLE IF NOT EXISTS templates_fts USING fts5(
+            name, description, content=templates
+          );
+        `);
+        
+        // Create triggers to keep FTS5 in sync
+        this.db.exec(`
+          CREATE TRIGGER IF NOT EXISTS templates_ai AFTER INSERT ON templates BEGIN
+            INSERT INTO templates_fts(rowid, name, description)
+            VALUES (new.id, new.name, new.description);
+          END;
+        `);
+        
+        this.db.exec(`
+          CREATE TRIGGER IF NOT EXISTS templates_au AFTER UPDATE ON templates BEGIN
+            UPDATE templates_fts SET name = new.name, description = new.description
+            WHERE rowid = new.id;
+          END;
+        `);
+        
+        this.db.exec(`
+          CREATE TRIGGER IF NOT EXISTS templates_ad AFTER DELETE ON templates BEGIN
+            DELETE FROM templates_fts WHERE rowid = old.id;
+          END;
+        `);
+        
+        logger.info('FTS5 support enabled for template search');
+      } catch (error) {
+        logger.warn('Failed to initialize FTS5 for templates:', error);
+        this.hasFTS5Support = false;
+      }
+    } else {
+      logger.info('FTS5 not available, using LIKE search for templates');
+    }
   }
   
   /**
@@ -110,16 +158,41 @@ export class TemplateRepository {
    * Search templates by name or description
    */
   searchTemplates(query: string, limit: number = 20): StoredTemplate[] {
-    // Use FTS for search
-    const ftsQuery = query.split(' ').map(term => `"${term}"`).join(' OR ');
+    // If FTS5 is not supported, go straight to LIKE search
+    if (!this.hasFTS5Support) {
+      return this.searchTemplatesLIKE(query, limit);
+    }
+    
+    try {
+      // Use FTS for search
+      const ftsQuery = query.split(' ').map(term => `"${term}"`).join(' OR ');
+      
+      return this.db.prepare(`
+        SELECT t.* FROM templates t
+        JOIN templates_fts ON t.id = templates_fts.rowid
+        WHERE templates_fts MATCH ?
+        ORDER BY rank, t.views DESC
+        LIMIT ?
+      `).all(ftsQuery, limit) as StoredTemplate[];
+    } catch (error: any) {
+      // If FTS5 query fails, fallback to LIKE search
+      logger.warn('FTS5 template search failed, using LIKE fallback:', error.message);
+      return this.searchTemplatesLIKE(query, limit);
+    }
+  }
+  
+  /**
+   * Fallback search using LIKE when FTS5 is not available
+   */
+  private searchTemplatesLIKE(query: string, limit: number = 20): StoredTemplate[] {
+    const likeQuery = `%${query}%`;
     
     return this.db.prepare(`
-      SELECT t.* FROM templates t
-      JOIN templates_fts ON t.id = templates_fts.rowid
-      WHERE templates_fts MATCH ?
-      ORDER BY rank, t.views DESC
+      SELECT * FROM templates 
+      WHERE name LIKE ? OR description LIKE ?
+      ORDER BY views DESC, created_at DESC
       LIMIT ?
-    `).all(ftsQuery, limit) as StoredTemplate[];
+    `).all(likeQuery, likeQuery, limit) as StoredTemplate[];
   }
   
   /**
@@ -208,4 +281,32 @@ export class TemplateRepository {
     this.db.exec('DELETE FROM templates');
     logger.info('Cleared all templates from database');
   }
+  
+  /**
+   * Rebuild the FTS5 index for all templates
+   * This is needed when templates are bulk imported or when FTS5 gets out of sync
+   */
+  rebuildTemplateFTS(): void {
+    // Skip if FTS5 is not supported
+    if (!this.hasFTS5Support) {
+      return;
+    }
+    
+    try {
+      // Clear existing FTS data
+      this.db.exec('DELETE FROM templates_fts');
+      
+      // Repopulate from templates table
+      this.db.exec(`
+        INSERT INTO templates_fts(rowid, name, description)
+        SELECT id, name, description FROM templates
+      `);
+      
+      const count = this.getTemplateCount();
+      logger.info(`Rebuilt FTS5 index for ${count} templates`);
+    } catch (error) {
+      logger.warn('Failed to rebuild template FTS5 index:', error);
+      // Non-critical error - search will fallback to LIKE
+    }
+  }
 }

src/templates/template-service.ts

@@ -132,6 +132,11 @@ export class TemplateService {
       }
       
       logger.info(`Successfully saved ${saved} templates to database`);
+      
+      // Rebuild FTS5 index after bulk import
+      logger.info('Rebuilding FTS5 index for templates');
+      this.repository.rebuildTemplateFTS();
+      
       progressCallback?.('Complete', saved, saved);
     } catch (error) {
       logger.error('Error fetching templates:', error);