Add optional translation to system prompts

So that system prompts can be written in any locale

Author: paulinevos

src/agent/CHANGELOG.md

@@ -54,3 +54,4 @@ CHANGELOG
  * Add model capability detection before processing
  * Add comprehensive type safety with full PHP type hints
  * Add clear exception hierarchy for different error scenarios
+ * Add translation support for system prompts

src/agent/composer.json

@@ -30,6 +30,7 @@
         "symfony/property-access": "^6.4 || ^7.1",
         "symfony/property-info": "^6.4 || ^7.1",
         "symfony/serializer": "^6.4 || ^7.1",
+        "symfony/translation": "^6.4 || ^7.1",
         "symfony/type-info": "^7.2.3"
     },
     "require-dev": {

src/agent/src/InputProcessor/SystemPromptInputProcessor.php

@@ -13,11 +13,13 @@
 
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
+use Symfony\AI\Agent\Exception\RuntimeException;
 use Symfony\AI\Agent\Input;
 use Symfony\AI\Agent\InputProcessorInterface;
 use Symfony\AI\Agent\Toolbox\ToolboxInterface;
 use Symfony\AI\Platform\Message\Message;
 use Symfony\AI\Platform\Tool\Tool;
+use Symfony\Contracts\Translation\TranslatorInterface;
 
 /**
  * @author Christopher Hertel <mail@christopher-hertel.de>
@@ -31,6 +33,9 @@
     public function __construct(
         private \Stringable|string $systemPrompt,
         private ?ToolboxInterface $toolbox = null,
+        private ?TranslatorInterface $translator = null,
+        private bool $enableTranslation = false,
+        private ?string $translationDomain = null,
         private LoggerInterface $logger = new NullLogger(),
     ) {
     }
@@ -45,7 +50,7 @@ public function processInput(Input $input): void
             return;
         }
 
-        $message = (string) $this->systemPrompt;
+        $message = $this->translateIfEnabled();
 
         if ($this->toolbox instanceof ToolboxInterface
             && [] !== $this->toolbox->getTools()
@@ -61,7 +66,7 @@ public function processInput(Input $input): void
             ));
 
             $message = <<<PROMPT
-                {$this->systemPrompt}
+                {$message}
 
                 # Tools
 
@@ -73,4 +78,15 @@ public function processInput(Input $input): void
 
         $input->messages = $messages->prepend(Message::forSystem($message));
     }
+
+    private function translateIfEnabled(): string
+    {
+        if ($this->enableTranslation && !$this->translator) {
+            throw new RuntimeException('Prompt translation is enabled but no translator was provided.');
+        }
+
+        return $this->enableTranslation
+            ? $this->translator->trans((string) $this->systemPrompt, [], $this->translationDomain)
+            : (string) $this->systemPrompt;
+    }
 }

src/agent/tests/InputProcessor/SystemPromptInputProcessorTest.php

@@ -29,6 +29,7 @@
 use Symfony\AI\Platform\Result\ToolCall;
 use Symfony\AI\Platform\Tool\ExecutionReference;
 use Symfony\AI\Platform\Tool\Tool;
+use Symfony\Contracts\Translation\TranslatorInterface;
 
 #[CoversClass(SystemPromptInputProcessor::class)]
 #[UsesClass(Gpt::class)]
@@ -89,7 +90,7 @@ public function execute(ToolCall $toolCall): mixed
                 {
                     return null;
                 }
-            }
+            },
         );
 
         $input = new Input(new Gpt(), new MessageBag(Message::ofUser('This is a user message')));
@@ -105,7 +106,7 @@ public function execute(ToolCall $toolCall): mixed
     public function testIncludeToolDefinitions()
     {
         $processor = new SystemPromptInputProcessor(
-            'This is a system prompt',
+            'This is a',
             new class implements ToolboxInterface {
                 public function getTools(): array
                 {
@@ -127,7 +128,9 @@ public function execute(ToolCall $toolCall): mixed
                 {
                     return null;
                 }
-            }
+            },
+            $this->getTranslator(),
+            true,
         );
 
         $input = new Input(new Gpt(), new MessageBag(Message::ofUser('This is a user message')));
@@ -138,7 +141,7 @@ public function execute(ToolCall $toolCall): mixed
         $this->assertInstanceOf(SystemMessage::class, $messages[0]);
         $this->assertInstanceOf(UserMessage::class, $messages[1]);
         $this->assertSame(<<<PROMPT
-            This is a system prompt
+            This is a cool translated system prompt
 
             # Tools
 
@@ -169,7 +172,7 @@ public function execute(ToolCall $toolCall): mixed
                 {
                     return null;
                 }
-            }
+            },
         );
 
         $input = new Input(new Gpt(), new MessageBag(Message::ofUser('This is a user message')));
@@ -190,4 +193,69 @@ public function execute(ToolCall $toolCall): mixed
             A tool without parameters
             PROMPT, $messages[0]->content);
     }
+
+    public function testWithTranslatedSystemPrompt()
+    {
+        $processor = new SystemPromptInputProcessor('This is a', null, $this->getTranslator(), true);
+
+        $input = new Input(new Gpt(), new MessageBag(Message::ofUser('This is a user message')), []);
+        $processor->processInput($input);
+
+        $messages = $input->messages->getMessages();
+        $this->assertCount(2, $messages);
+        $this->assertInstanceOf(SystemMessage::class, $messages[0]);
+        $this->assertInstanceOf(UserMessage::class, $messages[1]);
+        $this->assertSame('This is a cool translated system prompt', $messages[0]->content);
+    }
+
+    public function testWithTranslationDomainSystemPrompt()
+    {
+        $processor = new SystemPromptInputProcessor(
+            'This is a',
+            null,
+            $this->getTranslator(),
+            true,
+            'prompts'
+        );
+
+        $input = new Input(new Gpt(), new MessageBag(), []);
+        $processor->processInput($input);
+
+        $messages = $input->messages->getMessages();
+        $this->assertCount(1, $messages);
+        $this->assertInstanceOf(SystemMessage::class, $messages[0]);
+        $this->assertSame('This is a cool translated system prompt with a translation domain', $messages[0]->content);
+    }
+
+    public function testWithMissingTranslator()
+    {
+        $processor = new SystemPromptInputProcessor(
+            'This is a',
+            null,
+            null,
+            true,
+        );
+
+        $input = new Input(new Gpt(), new MessageBag(), []);
+
+        $this->expectExceptionMessage('Prompt translation is enabled but no translator was provided');
+        $processor->processInput($input);
+    }
+
+    private function getTranslator(): TranslatorInterface
+    {
+        return new class implements TranslatorInterface {
+            public function trans(string $id, array $parameters = [], ?string $domain = null, ?string $locale = null): string
+            {
+                $translated = \sprintf('%s cool translated system prompt', $id);
+
+                return $domain ? $translated.' with a translation domain' : $translated;
+            }
+
+            public function getLocale(): string
+            {
+                return 'en';
+            }
+        };
+    }
 }

src/ai-bundle/config/options.php

@@ -162,6 +162,14 @@
                                     ->info('Include tool definitions at the end of the system prompt')
                                     ->defaultFalse()
                                 ->end()
+                                ->booleanNode('enable_translation')
+                                    ->info('Enable translation for the system prompt')
+                                    ->defaultFalse()
+                                ->end()
+                                ->scalarNode('translation_domain')
+                                    ->info('The translation domain for the system prompt')
+                                    ->defaultNull()
+                                ->end()
                             ->end()
                         ->end()
                         ->arrayNode('tools')

src/ai-bundle/src/AiBundle.php

@@ -611,6 +611,9 @@ private function processAgentConfig(string $name, array $config, ContainerBuilde
                 ->setArguments([
                     $config['prompt']['text'],
                     $includeTools ? new Reference('ai.toolbox.'.$name) : null,
+                    new Reference('translator', ContainerInterface::NULL_ON_INVALID_REFERENCE),
+                    $config['prompt']['enable_translation'],
+                    $config['prompt']['translation_domain'],
                     new Reference('logger', ContainerInterface::IGNORE_ON_INVALID_REFERENCE),
                 ])
                 ->addTag('ai.agent.input_processor', ['agent' => $agentId, 'priority' => -30]);

src/ai-bundle/tests/DependencyInjection/AiBundleTest.php

@@ -471,11 +471,13 @@ public function testMultipleAgentsWithProcessors()
         $firstSystemPrompt = $container->getDefinition('ai.agent.first_agent.system_prompt_processor');
         $firstSystemTags = $firstSystemPrompt->getTag('ai.agent.input_processor');
         $this->assertSame($firstAgentId, $firstSystemTags[0]['agent']);
+        $this->assertCount(3, array_filter($firstSystemPrompt->getArguments()));
 
         // Second agent system prompt processor
         $secondSystemPrompt = $container->getDefinition('ai.agent.second_agent.system_prompt_processor');
         $secondSystemTags = $secondSystemPrompt->getTag('ai.agent.input_processor');
         $this->assertSame($secondAgentId, $secondSystemTags[0]['agent']);
+        $this->assertCount(3, array_filter($secondSystemPrompt->getArguments()));
     }
 
     #[TestDox('Processors work correctly when using the default toolbox')]
@@ -658,6 +660,8 @@ public function testSystemPromptWithArrayStructure()
                         'model' => ['class' => 'Symfony\AI\Platform\Bridge\OpenAi\Gpt'],
                         'prompt' => [
                             'text' => 'You are a helpful assistant.',
+                            'enable_translation' => true,
+                            'translation_domain' => 'prompts',
                         ],
                         'tools' => [
                             ['service' => 'some_tool', 'description' => 'Test tool'],
@@ -673,6 +677,8 @@ public function testSystemPromptWithArrayStructure()
 
         $this->assertSame('You are a helpful assistant.', $arguments[0]);
         $this->assertNull($arguments[1]); // include_tools is false, so null reference
+        $this->assertTrue($arguments[3]);
+        $this->assertSame('prompts', $arguments[4]);
     }
 
     #[TestDox('System prompt with include_tools enabled works correctly')]