[AI Bundle][Platform] Integrate template rendering into Message API

examples/platform/template/01-system-message.php

@@ -0,0 +1,47 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\AI\Platform\Bridge\OpenAi\PlatformFactory;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\Template;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+require_once dirname(__DIR__, 2).'/bootstrap.php';
+
+$eventDispatcher = new EventDispatcher();
+$rendererRegistry = new ChainTemplateRenderer([
+    new StringTemplateRenderer(),
+]);
+$templateListener = new TemplateRendererListener($rendererRegistry);
+$eventDispatcher->addSubscriber($templateListener);
+
+$platform = PlatformFactory::create(env('OPENAI_API_KEY'), http_client(), eventDispatcher: $eventDispatcher);
+
+echo "SystemMessage with template\n";
+echo "===========================\n\n";
+
+$template = Template::string('You are a {domain} expert assistant.');
+$messages = new MessageBag(
+    Message::forSystem($template),
+    Message::ofUser('What is PHP?')
+);
+
+$result = $platform->invoke('gpt-4o-mini', $messages, [
+    'template_vars' => ['domain' => 'programming'],
+]);
+
+echo "SystemMessage template: You are a {domain} expert assistant.\n";
+echo "Variables: ['domain' => 'programming']\n";
+echo 'Response: '.$result->asText()."\n";

examples/platform/template/02-user-message.php

@@ -0,0 +1,46 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\AI\Platform\Bridge\OpenAi\PlatformFactory;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\Template;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+require_once dirname(__DIR__, 2).'/bootstrap.php';
+
+$eventDispatcher = new EventDispatcher();
+$rendererRegistry = new ChainTemplateRenderer([
+    new StringTemplateRenderer(),
+]);
+$templateListener = new TemplateRendererListener($rendererRegistry);
+$eventDispatcher->addSubscriber($templateListener);
+
+$platform = PlatformFactory::create(env('OPENAI_API_KEY'), http_client(), eventDispatcher: $eventDispatcher);
+
+echo "UserMessage with template\n";
+echo "=========================\n\n";
+
+$messages = new MessageBag(
+    Message::forSystem('You are a helpful assistant.'),
+    Message::ofUser(Template::string('Tell me about {topic}'))
+);
+
+$result = $platform->invoke('gpt-4o-mini', $messages, [
+    'template_vars' => ['topic' => 'PHP'],
+]);
+
+echo "UserMessage template: Tell me about {topic}\n";
+echo "Variables: ['topic' => 'PHP']\n";
+echo 'Response: '.$result->asText()."\n";

examples/platform/template/03-multiple-messages.php

@@ -0,0 +1,53 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\AI\Platform\Bridge\OpenAi\PlatformFactory;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\Template;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+require_once dirname(__DIR__, 2).'/bootstrap.php';
+
+$eventDispatcher = new EventDispatcher();
+$rendererRegistry = new ChainTemplateRenderer([
+    new StringTemplateRenderer(),
+]);
+$templateListener = new TemplateRendererListener($rendererRegistry);
+$eventDispatcher->addSubscriber($templateListener);
+
+$platform = PlatformFactory::create(env('OPENAI_API_KEY'), http_client(), eventDispatcher: $eventDispatcher);
+
+echo "Multiple messages with templates\n";
+echo "=================================\n\n";
+
+$systemTemplate = Template::string('You are a {domain} assistant.');
+$userTemplate = Template::string('Calculate {operation}');
+
+$messages = new MessageBag(
+    Message::forSystem($systemTemplate),
+    Message::ofUser($userTemplate)
+);
+
+$result = $platform->invoke('gpt-4o-mini', $messages, [
+    'template_vars' => [
+        'domain' => 'math',
+        'operation' => '2 + 2',
+    ],
+]);
+
+echo "System template: You are a {domain} assistant.\n";
+echo "User template: Calculate {operation}\n";
+echo "Variables: ['domain' => 'math', 'operation' => '2 + 2']\n";
+echo 'Response: '.$result->asText()."\n";

examples/platform/template/04-mixed-content.php

@@ -0,0 +1,46 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\AI\Platform\Bridge\OpenAi\PlatformFactory;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\Template;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+require_once dirname(__DIR__, 2).'/bootstrap.php';
+
+$eventDispatcher = new EventDispatcher();
+$rendererRegistry = new ChainTemplateRenderer([
+    new StringTemplateRenderer(),
+]);
+$templateListener = new TemplateRendererListener($rendererRegistry);
+$eventDispatcher->addSubscriber($templateListener);
+
+$platform = PlatformFactory::create(env('OPENAI_API_KEY'), http_client(), eventDispatcher: $eventDispatcher);
+
+echo "UserMessage with mixed content\n";
+echo "==============================\n\n";
+
+$messages = new MessageBag(
+    Message::forSystem('You are a helpful assistant.'),
+    Message::ofUser('I need help with', Template::string(' {task}'))
+);
+
+$result = $platform->invoke('gpt-4o-mini', $messages, [
+    'template_vars' => ['task' => 'debugging'],
+]);
+
+echo "UserMessage: 'Plain text' + Template('{task}')\n";
+echo "Variables: ['task' => 'debugging']\n";
+echo 'Response: '.$result->asText()."\n";

src/ai-bundle/config/services.php

@@ -62,6 +62,10 @@
 use Symfony\AI\Platform\Contract;
 use Symfony\AI\Platform\Contract\JsonSchema\DescriptionParser;
 use Symfony\AI\Platform\Contract\JsonSchema\Factory as SchemaFactory;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\ExpressionLanguageTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
 use Symfony\AI\Platform\Serializer\StructuredOutputSerializer;
 use Symfony\AI\Platform\StructuredOutput\PlatformSubscriber;
 use Symfony\AI\Platform\StructuredOutput\ResponseFormatFactory;
@@ -70,6 +74,7 @@
 use Symfony\AI\Store\Command\IndexCommand;
 use Symfony\AI\Store\Command\RetrieveCommand;
 use Symfony\AI\Store\Command\SetupStoreCommand;
+use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
 
 return static function (ContainerConfigurator $container): void {
     $container->services()
@@ -112,6 +117,30 @@
         ->set('ai.platform.model_catalog.vertexai.gemini', VertexAiModelCatalog::class)
         ->set('ai.platform.model_catalog.voyage', VoyageModelCatalog::class)
 
+        // message templates
+        ->set('ai.platform.template_renderer.string', StringTemplateRenderer::class)
+            ->tag('ai.platform.template_renderer');
+
+    if (class_exists(ExpressionLanguage::class)) {
+        $container->services()
+            ->set('ai.platform.template_renderer.expression', ExpressionLanguageTemplateRenderer::class)
+                ->args([
+                    service('expression_language'),
+                ])
+                ->tag('ai.platform.template_renderer');
+    }
+
+    $container->services()
+        ->set('ai.platform.template_renderer_registry', ChainTemplateRenderer::class)
+            ->args([
+                tagged_iterator('ai.platform.template_renderer'),
+            ])
+        ->set('ai.platform.template_renderer_listener', TemplateRendererListener::class)
+            ->args([
+                service('ai.platform.template_renderer_registry'),
+            ])
+            ->tag('kernel.event_subscriber')
+
         // structured output
         ->set('ai.agent.response_format_factory', ResponseFormatFactory::class)
             ->args([

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

@@ -30,6 +30,10 @@
 use Symfony\AI\Platform\Bridge\ElevenLabs\PlatformFactory;
 use Symfony\AI\Platform\Bridge\Ollama\OllamaApiCatalog;
 use Symfony\AI\Platform\Capability;
+use Symfony\AI\Platform\EventListener\TemplateRendererListener;
+use Symfony\AI\Platform\Message\TemplateRenderer\ChainTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\ExpressionLanguageTemplateRenderer;
+use Symfony\AI\Platform\Message\TemplateRenderer\StringTemplateRenderer;
 use Symfony\AI\Platform\Model;
 use Symfony\AI\Platform\PlatformInterface;
 use Symfony\AI\Store\Bridge\AzureSearch\SearchStore as AzureStore;
@@ -72,6 +76,7 @@
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
 use Symfony\Component\HttpClient\HttpClient;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 
@@ -6853,6 +6858,42 @@ public function testModelConfigurationIsIgnoredForUnknownPlatform()
         $this->assertSame([], $definition->getArguments());
     }
 
+    public function testTemplateRendererServicesAreRegistered()
+    {
+        $container = $this->buildContainer([
+            'ai' => [
+                'platform' => [
+                    'anthropic' => [
+                        'api_key' => 'test_key',
+                    ],
+                ],
+            ],
+        ]);
+
+        // Verify string template renderer is registered
+        $this->assertTrue($container->hasDefinition('ai.platform.template_renderer.string'));
+        $stringRendererDefinition = $container->getDefinition('ai.platform.template_renderer.string');
+        $this->assertSame(StringTemplateRenderer::class, $stringRendererDefinition->getClass());
+        $this->assertTrue($stringRendererDefinition->hasTag('ai.platform.template_renderer'));
+
+        // Verify expression template renderer is registered
+        $this->assertTrue($container->hasDefinition('ai.platform.template_renderer.expression'));
+        $expressionRendererDefinition = $container->getDefinition('ai.platform.template_renderer.expression');
+        $this->assertSame(ExpressionLanguageTemplateRenderer::class, $expressionRendererDefinition->getClass());
+        $this->assertTrue($expressionRendererDefinition->hasTag('ai.platform.template_renderer'));
+
+        // Verify template renderer registry is registered
+        $this->assertTrue($container->hasDefinition('ai.platform.template_renderer_registry'));
+        $registryDefinition = $container->getDefinition('ai.platform.template_renderer_registry');
+        $this->assertSame(ChainTemplateRenderer::class, $registryDefinition->getClass());
+
+        // Verify template renderer listener is registered as event subscriber
+        $this->assertTrue($container->hasDefinition('ai.platform.template_renderer_listener'));
+        $listenerDefinition = $container->getDefinition('ai.platform.template_renderer_listener');
+        $this->assertSame(TemplateRendererListener::class, $listenerDefinition->getClass());
+        $this->assertTrue($listenerDefinition->hasTag('kernel.event_subscriber'));
+    }
+
     private function buildContainer(array $configuration): ContainerBuilder
     {
         $container = new ContainerBuilder();

src/platform/AGENTS.md

@@ -13,13 +13,15 @@ Unified abstraction for AI platforms (OpenAI, Anthropic, Azure, Gemini, VertexAI
 - **Model**: AI models with provider-specific configurations
 - **Contract**: Abstract contracts for AI capabilities (chat, embedding, speech)
 - **Message**: Message system for AI interactions
+- **Template**: Message templating with pluggable rendering strategies
 - **Tool**: Function calling capabilities
 - **Bridge**: Provider-specific implementations
 
 ### Key Directories
 - `src/Bridge/`: Provider implementations
 - `src/Contract/`: Abstract contracts and interfaces
-- `src/Message/`: Message handling system
+- `src/Message/`: Message handling system with Template support
+- `src/Message/TemplateRenderer/`: Template rendering strategies
 - `src/Tool/`: Function calling and tool definitions
 - `src/Result/`: Result types and converters
 - `src/Exception/`: Platform-specific exceptions
@@ -54,11 +56,50 @@ composer install
 composer update
 ```
 
+## Usage Patterns
+
+### Message Templates
+
+Templates support variable substitution with type-based rendering. SystemMessage and UserMessage support templates.
+
+```php
+use Symfony\AI\Platform\Message\Message;
+use Symfony\AI\Platform\Message\MessageBag;
+use Symfony\AI\Platform\Message\Template;
+
+// SystemMessage with template
+$template = Template::string('You are a {role} assistant.');
+$message = Message::forSystem($template);
+
+// UserMessage with template
+$message = Message::ofUser(Template::string('Calculate {operation}'));
+
+// Multiple messages with templates
+$messages = new MessageBag(
+    Message::forSystem(Template::string('You are a {role} assistant.')),
+    Message::ofUser(Template::string('Calculate {operation}'))
+);
+
+$result = $platform->invoke('gpt-4o-mini', $messages, [
+    'template_vars' => [
+        'role' => 'helpful',
+        'operation' => '2 + 2',
+    ],
+]);
+
+// Expression template (requires symfony/expression-language)
+$template = Template::expression('price * quantity');
+```
+
+Rendering happens externally during `Platform.invoke()` when `template_vars` option is provided.
+
 ## Development Notes
 
 - PHPUnit 11+ with strict configuration
 - Test fixtures in `../../fixtures` for multimodal content
 - MockHttpClient pattern preferred
 - Follows Symfony coding standards
 - Bridge pattern for provider implementations
-- Consistent contract interfaces across providers
+- Consistent contract interfaces across providers
+- Template system uses type-based rendering (not renderer injection)
+- Template rendering via TemplateRendererListener during invocation