feat: Support custom response language (#510)

* feat: Support custom response language

* fix: Add default values for response language in config-manager.js

* chore: Update configuration file and add default response language settings

* feat: Support MCP/CLI custom response language

* chore: Update test comments to English for consistency

* docs: Auto-update and format models.md

* chore: fix format

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Ralph Khreish <35776126+Crunchyman-ralph@users.noreply.github.com>

scripts/modules/ai-services-unified.js

@@ -15,6 +15,7 @@ import {
 	getFallbackProvider,
 	getFallbackModelId,
 	getParametersForRole,
+	getResponseLanguage,
 	getUserId,
 	MODEL_MAP,
 	getDebugFlag,
@@ -551,9 +552,12 @@ async function _unifiedServiceRunner(serviceType, params) {
 			}
 
 			const messages = [];
-			if (systemPrompt) {
-				messages.push({ role: 'system', content: systemPrompt });
-			}
+			const responseLanguage = getResponseLanguage(effectiveProjectRoot);
+			const systemPromptWithLanguage = `${systemPrompt} \n\n Always respond in ${responseLanguage}.`;
+			messages.push({
+				role: 'system',
+				content: systemPromptWithLanguage.trim()
+			});
 
 			// IN THE FUTURE WHEN DOING CONTEXT IMPROVEMENTS
 			// {

scripts/modules/commands.js

@@ -42,7 +42,8 @@ import {
 	findTaskById,
 	taskExists,
 	moveTask,
-	migrateProject
+	migrateProject,
+	setResponseLanguage
 } from './task-manager.js';
 
 import {
@@ -3661,6 +3662,63 @@ Examples:
 			return; // Stop execution here
 		});
 
+	// response-language command
+	programInstance
+		.command('lang')
+		.description('Manage response language settings')
+		.option('--response <response_language>', 'Set the response language')
+		.option('--setup', 'Run interactive setup to configure response language')
+		.action(async (options) => {
+			const projectRoot = findProjectRoot(); // Find project root for context
+			const { response, setup } = options;
+			console.log(
+				chalk.blue('Response language set to:', JSON.stringify(options))
+			);
+			let responseLanguage = response || 'English';
+			if (setup) {
+				console.log(
+					chalk.blue('Starting interactive response language setup...')
+				);
+				try {
+					const userResponse = await inquirer.prompt([
+						{
+							type: 'input',
+							name: 'responseLanguage',
+							message: 'Input your preferred response language',
+							default: 'English'
+						}
+					]);
+
+					console.log(
+						chalk.blue(
+							'Response language set to:',
+							userResponse.responseLanguage
+						)
+					);
+					responseLanguage = userResponse.responseLanguage;
+				} catch (setupError) {
+					console.error(
+						chalk.red('\\nInteractive setup failed unexpectedly:'),
+						setupError.message
+					);
+				}
+			}
+
+			const result = setResponseLanguage(responseLanguage, {
+				projectRoot
+			});
+
+			if (result.success) {
+				console.log(chalk.green(`✅ ${result.data.message}`));
+			} else {
+				console.error(
+					chalk.red(
+						`❌ Error setting response language: ${result.error.message}`
+					)
+				);
+			}
+		});
+
 	// move-task command
 	programInstance
 		.command('move')

scripts/modules/config-manager.js

@@ -66,7 +66,8 @@ const DEFAULTS = {
 		defaultPriority: 'medium',
 		projectName: 'Task Master',
 		ollamaBaseURL: 'http://localhost:11434/api',
-		bedrockBaseURL: 'https://bedrock.us-east-1.amazonaws.com'
+		bedrockBaseURL: 'https://bedrock.us-east-1.amazonaws.com',
+		responseLanguage: 'English'
 	}
 };
 
@@ -425,6 +426,11 @@ function getVertexLocation(explicitRoot = null) {
 	return getGlobalConfig(explicitRoot).vertexLocation || 'us-central1';
 }
 
+function getResponseLanguage(explicitRoot = null) {
+	// Directly return value from config
+	return getGlobalConfig(explicitRoot).responseLanguage;
+}
+
 /**
  * Gets model parameters (maxTokens, temperature) for a specific role,
  * considering model-specific overrides from supported-models.json.
@@ -841,6 +847,7 @@ export {
 	getOllamaBaseURL,
 	getAzureBaseURL,
 	getBedrockBaseURL,
+	getResponseLanguage,
 	getParametersForRole,
 	getUserId,
 	// API Key Checkers (still relevant)

scripts/modules/task-manager.js

@@ -23,10 +23,12 @@ import updateSubtaskById from './task-manager/update-subtask-by-id.js';
 import removeTask from './task-manager/remove-task.js';
 import taskExists from './task-manager/task-exists.js';
 import isTaskDependentOn from './task-manager/is-task-dependent.js';
+import setResponseLanguage from './task-manager/response-language.js';
 import moveTask from './task-manager/move-task.js';
 import { migrateProject } from './task-manager/migrate.js';
 import { performResearch } from './task-manager/research.js';
 import { readComplexityReport } from './utils.js';
+
 // Export task manager functions
 export {
 	parsePRD,
@@ -49,6 +51,7 @@ export {
 	findTaskById,
 	taskExists,
 	isTaskDependentOn,
+	setResponseLanguage,
 	moveTask,
 	readComplexityReport,
 	migrateProject,

scripts/modules/task-manager/response-language.js

@@ -0,0 +1,94 @@
+import path from 'path';
+import fs from 'fs';
+import {
+	getConfig,
+	isConfigFilePresent,
+	writeConfig
+} from '../config-manager.js';
+
+function setResponseLanguage(lang, options = {}) {
+	const { mcpLog, projectRoot } = options;
+
+	const report = (level, ...args) => {
+		if (mcpLog && typeof mcpLog[level] === 'function') {
+			mcpLog[level](...args);
+		}
+	};
+
+	let configPath;
+	let configExists = false;
+
+	if (projectRoot) {
+		configPath = path.join(projectRoot, '.taskmasterconfig');
+		configExists = fs.existsSync(configPath);
+		report(
+			'info',
+			`Checking for .taskmasterconfig at: ${configPath}, exists: ${configExists}`
+		);
+	} else {
+		configExists = isConfigFilePresent();
+		report(
+			'info',
+			`Checking for .taskmasterconfig using isConfigFilePresent(), exists: ${configExists}`
+		);
+	}
+
+	if (!configExists) {
+		return {
+			success: false,
+			error: {
+				code: 'CONFIG_MISSING',
+				message:
+					'The .taskmasterconfig file is missing. Run "task-master models --setup" to create it.'
+			}
+		};
+	}
+
+	// Validate response language
+	if (typeof lang !== 'string' || lang.trim() === '') {
+		return {
+			success: false,
+			error: {
+				code: 'INVALID_RESPONSE_LANGUAGE',
+				message: `Invalid response language: ${lang}. Must be a non-empty string.`
+			}
+		};
+	}
+
+	try {
+		const currentConfig = getConfig(projectRoot);
+		currentConfig.global.responseLanguage = lang;
+		const writeResult = writeConfig(currentConfig, projectRoot);
+
+		if (!writeResult) {
+			return {
+				success: false,
+				error: {
+					code: 'WRITE_ERROR',
+					message: 'Error writing updated configuration to .taskmasterconfig'
+				}
+			};
+		}
+
+		const successMessage = `Successfully set response language to: ${lang}`;
+		report('info', successMessage);
+		return {
+			success: true,
+			data: {
+				responseLanguage: lang,
+				message: successMessage
+			}
+		};
+	} catch (error) {
+		report('error', `Error setting response language: ${error.message}`);
+		return {
+			success: false,
+			error: {
+				code: 'SET_RESPONSE_LANGUAGE_ERROR',
+				message: error.message
+			}
+		};
+	}
+}
+
+export default setResponseLanguage;