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": "^7.3",
         "symfony/type-info": "^7.2.3"
     },
     "require-dev": {

src/agent/src/InputProcessor/SystemPromptInputProcessor.php

@@ -18,6 +18,7 @@
 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 +32,7 @@
     public function __construct(
         private \Stringable|string $systemPrompt,
         private ?ToolboxInterface $toolbox = null,
+        private ?TranslatorInterface $translator = null,
         private LoggerInterface $logger = new NullLogger(),
     ) {
     }
@@ -45,7 +47,9 @@ public function processInput(Input $input): void
             return;
         }
 
-        $message = (string) $this->systemPrompt;
+        $message = $this->translator
+            ? $this->translator->trans((string) $this->systemPrompt)
+            : (string) $this->systemPrompt;
 
         if ($this->toolbox instanceof ToolboxInterface
             && [] !== $this->toolbox->getTools()

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)]
@@ -186,4 +187,37 @@ public function execute(ToolCall $toolCall): mixed
             A tool without parameters
             PROMPT, $messages[0]->content);
     }
+
+    public function testWithTranslatedSystemPrompt()
+    {
+        $processor = new SystemPromptInputProcessor(
+            systemPrompt: 'This is a',
+            toolbox: null,
+            translator: $this->getTranslator()
+        );
+
+        $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 getTranslator(): TranslatorInterface
+    {
+        return new class implements TranslatorInterface {
+            public function trans(string $id, array $parameters = [], ?string $domain = null, ?string $locale = null): string
+            {
+                return \sprintf('%s cool translated system prompt', $id);
+            }
+
+            public function getLocale(): string
+            {
+                return 'en';
+            }
+        };
+    }
 }