diff --git a/demo/tests/Blog/ChatTest.php b/demo/tests/Blog/ChatTest.php
index c7c9333f6..811be0c69 100644
--- a/demo/tests/Blog/ChatTest.php
+++ b/demo/tests/Blog/ChatTest.php
@@ -37,8 +37,8 @@ public function testLoadMessagesReturnsDefaultSystemMessage()
 
         $systemMessage = $messages->getMessages()[0];
         $this->assertInstanceOf(SystemMessage::class, $systemMessage);
-        $this->assertStringContainsString('helpful assistant', $systemMessage->content);
-        $this->assertStringContainsString('similarity_search', $systemMessage->content);
+        $this->assertStringContainsString('helpful assistant', $systemMessage->getContent());
+        $this->assertStringContainsString('similarity_search', $systemMessage->getContent());
     }
 
     public function testSubmitMessageAddsUserMessageAndAgentResponse()
@@ -65,12 +65,12 @@ public function testSubmitMessageAddsUserMessageAndAgentResponse()
         // Check user message
         $userMessage = $messageList[1];
         $this->assertInstanceOf(UserMessage::class, $userMessage);
-        $this->assertSame('What is Symfony?', $userMessage->content[0]->text);
+        $this->assertSame('What is Symfony?', $userMessage->getContent()[0]->getText());
 
         // Check assistant message
         $assistantMessage = $messageList[2];
         $this->assertInstanceOf(AssistantMessage::class, $assistantMessage);
-        $this->assertSame('Symfony is a PHP web framework for building web applications and APIs.', $assistantMessage->content);
+        $this->assertSame('Symfony is a PHP web framework for building web applications and APIs.', $assistantMessage->getContent());
     }
 
     public function testSubmitMessageWithUnknownQueryUsesDefaultResponse()
@@ -91,7 +91,7 @@ public function testSubmitMessageWithUnknownQueryUsesDefaultResponse()
 
         // Check assistant used default response
         $assistantMessage = $messageList[2];
-        $this->assertSame('I can help you with Symfony-related questions!', $assistantMessage->content);
+        $this->assertSame('I can help you with Symfony-related questions!', $assistantMessage->getContent());
     }
 
     public function testMultipleMessagesAreTrackedCorrectly()
@@ -169,10 +169,10 @@ public function testAgentReceivesFullConversationHistory()
         $this->assertCount(5, $messages);
 
         // Verify the conversation flow (with 5 messages)
-        $this->assertStringContainsString('helpful assistant', $messages[0]->content); // system
-        $this->assertSame('What is Symfony?', $messages[1]->content[0]->text); // user1
-        $this->assertSame('Symfony is a PHP web framework for building web applications and APIs.', $messages[2]->content); // assistant1
-        $this->assertSame('Tell me more', $messages[3]->content[0]->text); // user2
+        $this->assertStringContainsString('helpful assistant', $messages[0]->getContent()); // system
+        $this->assertSame('What is Symfony?', $messages[1]->getContent()[0]->getText()); // user1
+        $this->assertSame('Symfony is a PHP web framework for building web applications and APIs.', $messages[2]->getContent()); // assistant1
+        $this->assertSame('Tell me more', $messages[3]->getContent()[0]->getText()); // user2
         // The 5th message appears to be the previous assistant response or another system message
     }
 
diff --git a/examples/chat/persistent-chat-cache.php b/examples/chat/persistent-chat-cache.php
index 0ce491ff2..78abdaa58 100644
--- a/examples/chat/persistent-chat-cache.php
+++ b/examples/chat/persistent-chat-cache.php
@@ -35,4 +35,4 @@
 $chat->submit(Message::ofUser('My name is Christopher.'));
 $message = $chat->submit(Message::ofUser('What is my name?'));
 
-echo $message->content.\PHP_EOL;
+echo $message->getContent().\PHP_EOL;
diff --git a/examples/chat/persistent-chat-session.php b/examples/chat/persistent-chat-session.php
index cf315cb7b..397664abd 100644
--- a/examples/chat/persistent-chat-session.php
+++ b/examples/chat/persistent-chat-session.php
@@ -44,4 +44,4 @@
 $chat->submit(Message::ofUser('My name is Christopher.'));
 $message = $chat->submit(Message::ofUser('What is my name?'));
 
-echo $message->content.\PHP_EOL;
+echo $message->getContent().\PHP_EOL;
diff --git a/examples/chat/persistent-chat.php b/examples/chat/persistent-chat.php
index cfe46a91c..a574e9f13 100644
--- a/examples/chat/persistent-chat.php
+++ b/examples/chat/persistent-chat.php
@@ -31,4 +31,4 @@
 $chat->submit(Message::ofUser('My name is Christopher.'));
 $message = $chat->submit(Message::ofUser('What is my name?'));
 
-echo $message->content.\PHP_EOL;
+echo $message->getContent().\PHP_EOL;
diff --git a/src/agent/src/Memory/EmbeddingProvider.php b/src/agent/src/Memory/EmbeddingProvider.php
index 99266535e..e93a76fde 100644
--- a/src/agent/src/Memory/EmbeddingProvider.php
+++ b/src/agent/src/Memory/EmbeddingProvider.php
@@ -43,7 +43,7 @@ public function load(Input $input): array
         }
 
         $userMessageTextContent = array_filter(
-            $userMessage->content,
+            $userMessage->getContent(),
             static fn (ContentInterface $content): bool => $content instanceof Text,
         );
 
@@ -53,7 +53,7 @@ public function load(Input $input): array
 
         $userMessageTextContent = array_shift($userMessageTextContent);
 
-        $vectors = $this->platform->invoke($this->model->getName(), $userMessageTextContent->text)->asVectors();
+        $vectors = $this->platform->invoke($this->model->getName(), $userMessageTextContent->getText())->asVectors();
         $foundEmbeddingContent = $this->vectorStore->query($vectors[0]);
         if (0 === \count($foundEmbeddingContent)) {
             return [];
diff --git a/src/agent/src/Memory/MemoryInputProcessor.php b/src/agent/src/Memory/MemoryInputProcessor.php
index 2c37bae82..997c5dad5 100644
--- a/src/agent/src/Memory/MemoryInputProcessor.php
+++ b/src/agent/src/Memory/MemoryInputProcessor.php
@@ -69,7 +69,7 @@ public function processInput(Input $input): void
             return;
         }
 
-        $systemMessage = $input->getMessageBag()->getSystemMessage()->content ?? '';
+        $systemMessage = $input->getMessageBag()->getSystemMessage()?->getContent() ?? '';
 
         $combinedMessage = self::MEMORY_PROMPT_MESSAGE.$memory;
         if ('' !== $systemMessage) {
diff --git a/src/agent/src/MockAgent.php b/src/agent/src/MockAgent.php
index 195db56b2..bea40fdff 100644
--- a/src/agent/src/MockAgent.php
+++ b/src/agent/src/MockAgent.php
@@ -62,9 +62,9 @@ public function call(MessageBag $messages, array $options = []): ResultInterface
         $content = '';
 
         if ($lastMessage instanceof UserMessage) {
-            foreach ($lastMessage->content as $messageContent) {
+            foreach ($lastMessage->getContent() as $messageContent) {
                 if ($messageContent instanceof Text) {
-                    $content .= $messageContent->text;
+                    $content .= $messageContent->getText();
                 }
             }
         }
diff --git a/src/agent/src/Toolbox/AgentProcessor.php b/src/agent/src/Toolbox/AgentProcessor.php
index 510f02e8d..f6236b994 100644
--- a/src/agent/src/Toolbox/AgentProcessor.php
+++ b/src/agent/src/Toolbox/AgentProcessor.php
@@ -89,7 +89,7 @@ private function handleToolCallsCallback(Output $output): \Closure
         return function (ToolCallResult $result, ?AssistantMessage $streamedAssistantResponse = null) use ($output): ResultInterface {
             $messages = $this->keepToolMessages ? $output->getMessageBag() : clone $output->getMessageBag();
 
-            if (null !== $streamedAssistantResponse && '' !== $streamedAssistantResponse->content) {
+            if (null !== $streamedAssistantResponse && '' !== $streamedAssistantResponse->getContent()) {
                 $messages->add($streamedAssistantResponse);
             }
 
diff --git a/src/agent/tests/InputProcessor/SystemPromptInputProcessorTest.php b/src/agent/tests/InputProcessor/SystemPromptInputProcessorTest.php
index a448ce943..803fe803b 100644
--- a/src/agent/tests/InputProcessor/SystemPromptInputProcessorTest.php
+++ b/src/agent/tests/InputProcessor/SystemPromptInputProcessorTest.php
@@ -41,7 +41,7 @@ public function testProcessInputAddsSystemMessageWhenNoneExists()
         $this->assertCount(2, $messages);
         $this->assertInstanceOf(SystemMessage::class, $messages[0]);
         $this->assertInstanceOf(UserMessage::class, $messages[1]);
-        $this->assertSame('This is a system prompt', $messages[0]->content);
+        $this->assertSame('This is a system prompt', $messages[0]->getContent());
     }
 
     public function testProcessInputDoesNotAddSystemMessageWhenOneExists()
@@ -59,7 +59,7 @@ public function testProcessInputDoesNotAddSystemMessageWhenOneExists()
         $this->assertCount(2, $messages);
         $this->assertInstanceOf(SystemMessage::class, $messages[0]);
         $this->assertInstanceOf(UserMessage::class, $messages[1]);
-        $this->assertSame('This is already a system prompt', $messages[0]->content);
+        $this->assertSame('This is already a system prompt', $messages[0]->getContent());
     }
 
     public function testDoesNotIncludeToolsIfToolboxIsEmpty()
@@ -86,7 +86,7 @@ public function execute(ToolCall $toolCall): mixed
         $this->assertCount(2, $messages);
         $this->assertInstanceOf(SystemMessage::class, $messages[0]);
         $this->assertInstanceOf(UserMessage::class, $messages[1]);
-        $this->assertSame('This is a system prompt', $messages[0]->content);
+        $this->assertSame('This is a system prompt', $messages[0]->getContent());
     }
 
     public function testIncludeToolDefinitions()
@@ -138,7 +138,7 @@ public function execute(ToolCall $toolCall): mixed
             ## tool_required_params
             A tool with required parameters
             or not
-            PROMPT, $messages[0]->content);
+            PROMPT, $messages[0]->getContent());
     }
 
     public function testWithStringableSystemPrompt()
@@ -176,7 +176,7 @@ public function execute(ToolCall $toolCall): mixed
 
             ## tool_no_params
             A tool without parameters
-            PROMPT, $messages[0]->content);
+            PROMPT, $messages[0]->getContent());
     }
 
     public function testWithTranslatedSystemPrompt()
@@ -190,7 +190,7 @@ public function testWithTranslatedSystemPrompt()
         $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);
+        $this->assertSame('This is a cool translated system prompt', $messages[0]->getContent());
     }
 
     public function testWithTranslationDomainSystemPrompt()
@@ -207,7 +207,7 @@ public function testWithTranslationDomainSystemPrompt()
         $messages = $input->getMessageBag()->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);
+        $this->assertSame('This is a cool translated system prompt with a translation domain', $messages[0]->getContent());
     }
 
     public function testWithMissingTranslator()
@@ -237,7 +237,7 @@ public function testProcessInputWithFile()
             $this->assertCount(2, $messages);
             $this->assertInstanceOf(SystemMessage::class, $messages[0]);
             $this->assertInstanceOf(UserMessage::class, $messages[1]);
-            $this->assertSame('This is a system prompt from a file', $messages[0]->content);
+            $this->assertSame('This is a system prompt from a file', $messages[0]->getContent());
         } finally {
             unlink($tempFile);
         }
@@ -258,7 +258,7 @@ public function testProcessInputWithMultilineFile()
             $messages = $input->getMessageBag()->getMessages();
             $this->assertCount(2, $messages);
             $this->assertInstanceOf(SystemMessage::class, $messages[0]);
-            $this->assertSame("Line 1\nLine 2\nLine 3", $messages[0]->content);
+            $this->assertSame("Line 1\nLine 2\nLine 3", $messages[0]->getContent());
         } finally {
             unlink($tempFile);
         }
diff --git a/src/agent/tests/Memory/MemoryInputProcessorTest.php b/src/agent/tests/Memory/MemoryInputProcessorTest.php
index 23cd26f20..d2cd806d2 100644
--- a/src/agent/tests/Memory/MemoryInputProcessorTest.php
+++ b/src/agent/tests/Memory/MemoryInputProcessorTest.php
@@ -82,7 +82,7 @@ public function testItIsAddingMemoryToSystemPrompt()
 
                 You are a helpful and kind assistant.
                 MARKDOWN,
-            $input->getMessageBag()->getSystemMessage()->content,
+            $input->getMessageBag()->getSystemMessage()->getContent(),
         );
     }
 
@@ -108,7 +108,7 @@ public function testItIsAddingMemoryToSystemPromptEvenItIsEmpty()
 
                 First memory content
                 MARKDOWN,
-            $input->getMessageBag()->getSystemMessage()->content,
+            $input->getMessageBag()->getSystemMessage()->getContent(),
         );
     }
 
@@ -135,7 +135,7 @@ public function testItIsAddingMultipleMemoryFromSingleProviderToSystemPrompt()
                 First memory content
                 Second memory content
                 MARKDOWN,
-            $input->getMessageBag()->getSystemMessage()->content,
+            $input->getMessageBag()->getSystemMessage()->getContent(),
         );
     }
 
@@ -151,6 +151,6 @@ public function testItIsNotAddingAnythingIfMemoryWasEmpty()
         $memoryInputProcessor->processInput($input = new Input('gpt-4', new MessageBag(), []));
 
         $this->assertArrayNotHasKey('use_memory', $input->getOptions());
-        $this->assertNull($input->getMessageBag()->getSystemMessage()?->content);
+        $this->assertNull($input->getMessageBag()->getSystemMessage()?->getContent());
     }
 }
diff --git a/src/ai-bundle/src/Command/AgentCallCommand.php b/src/ai-bundle/src/Command/AgentCallCommand.php
index 6bee9c490..b8571112b 100644
--- a/src/ai-bundle/src/Command/AgentCallCommand.php
+++ b/src/ai-bundle/src/Command/AgentCallCommand.php
@@ -153,7 +153,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
 
                 if (!$systemPromptDisplayed && null !== ($systemMessage = $messages->getSystemMessage())) {
                     $io->section('System Prompt');
-                    $io->block($systemMessage->content, null, 'fg=gray', ' ', true);
+                    $io->block($systemMessage->getContent(), null, 'fg=gray', ' ', true);
                     $systemPromptDisplayed = true;
                 }
 
diff --git a/src/chat/composer.json b/src/chat/composer.json
index 4da6583cc..2c45209d9 100644
--- a/src/chat/composer.json
+++ b/src/chat/composer.json
@@ -21,7 +21,8 @@
     ],
     "require": {
         "php": ">=8.2",
-        "symfony/ai-agent": "@dev"
+        "symfony/ai-agent": "@dev",
+        "symfony/ai-platform": "@dev"
     },
     "require-dev": {
         "phpstan/phpstan": "^2.0",
diff --git a/src/chat/tests/Bridge/Local/InMemoryStoreTest.php b/src/chat/tests/Bridge/Local/InMemoryStoreTest.php
index dc19e02c3..4e0cbd18a 100644
--- a/src/chat/tests/Bridge/Local/InMemoryStoreTest.php
+++ b/src/chat/tests/Bridge/Local/InMemoryStoreTest.php
@@ -72,8 +72,8 @@ public function testLoadReturnsStoredMessages()
         $this->assertCount(1, $loadedMessages);
         $messages = $loadedMessages->getMessages();
         $this->assertInstanceOf(UserMessage::class, $messages[0]);
-        $this->assertInstanceOf(Text::class, $messages[0]->content[0]);
-        $this->assertSame('Test message', $messages[0]->content[0]->text);
+        $this->assertInstanceOf(Text::class, $messages[0]->getContent()[0]);
+        $this->assertSame('Test message', $messages[0]->getContent()[0]->getText());
     }
 
     public function testDropClearsMessages()
diff --git a/src/chat/tests/ChatTest.php b/src/chat/tests/ChatTest.php
index 078d92465..b6ad22d9a 100644
--- a/src/chat/tests/ChatTest.php
+++ b/src/chat/tests/ChatTest.php
@@ -62,7 +62,7 @@ public function testItSubmitsUserMessageAndReturnsAssistantMessage()
         $result = $this->chat->submit($userMessage);
 
         $this->assertInstanceOf(AssistantMessage::class, $result);
-        $this->assertSame($assistantContent, $result->content);
+        $this->assertSame($assistantContent, $result->getContent());
         $this->assertCount(2, $this->store->load());
     }
 
@@ -87,7 +87,7 @@ public function testItAppendsMessagesToExistingConversation()
         $result = $this->chat->submit($newUserMessage);
 
         $this->assertInstanceOf(AssistantMessage::class, $result);
-        $this->assertSame($newAssistantContent, $result->content);
+        $this->assertSame($newAssistantContent, $result->getContent());
         $this->assertCount(2, $this->store->load());
     }
 
@@ -110,7 +110,7 @@ public function testItHandlesEmptyMessageStore()
         $result = $this->chat->submit($userMessage);
 
         $this->assertInstanceOf(AssistantMessage::class, $result);
-        $this->assertSame($assistantContent, $result->content);
+        $this->assertSame($assistantContent, $result->getContent());
         $this->assertCount(2, $this->store->load());
     }
 }
diff --git a/src/platform/src/Bridge/Anthropic/Contract/AssistantMessageNormalizer.php b/src/platform/src/Bridge/Anthropic/Contract/AssistantMessageNormalizer.php
index abe2148f0..fb5369969 100644
--- a/src/platform/src/Bridge/Anthropic/Contract/AssistantMessageNormalizer.php
+++ b/src/platform/src/Bridge/Anthropic/Contract/AssistantMessageNormalizer.php
@@ -50,7 +50,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
                     'name' => $toolCall->getName(),
                     'input' => [] !== $toolCall->getArguments() ? $toolCall->getArguments() : new \stdClass(),
                 ];
-            }, $data->toolCalls) : $data->content,
+            }, $data->getToolCalls()) : $data->getContent(),
         ];
     }
 
diff --git a/src/platform/src/Bridge/Anthropic/Contract/DocumentUrlNormalizer.php b/src/platform/src/Bridge/Anthropic/Contract/DocumentUrlNormalizer.php
index 8e36c3195..efcf30c02 100644
--- a/src/platform/src/Bridge/Anthropic/Contract/DocumentUrlNormalizer.php
+++ b/src/platform/src/Bridge/Anthropic/Contract/DocumentUrlNormalizer.php
@@ -32,7 +32,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
             'type' => 'document',
             'source' => [
                 'type' => 'url',
-                'url' => $data->url,
+                'url' => $data->getUrl(),
             ],
         ];
     }
diff --git a/src/platform/src/Bridge/Anthropic/Contract/ImageUrlNormalizer.php b/src/platform/src/Bridge/Anthropic/Contract/ImageUrlNormalizer.php
index 4f7edeb94..0f746244d 100644
--- a/src/platform/src/Bridge/Anthropic/Contract/ImageUrlNormalizer.php
+++ b/src/platform/src/Bridge/Anthropic/Contract/ImageUrlNormalizer.php
@@ -33,7 +33,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
             'type' => 'image',
             'source' => [
                 'type' => 'url',
-                'url' => $data->url,
+                'url' => $data->getUrl(),
             ],
         ];
     }
diff --git a/src/platform/src/Bridge/Anthropic/Contract/MessageBagNormalizer.php b/src/platform/src/Bridge/Anthropic/Contract/MessageBagNormalizer.php
index 709045cbe..9a29e459a 100644
--- a/src/platform/src/Bridge/Anthropic/Contract/MessageBagNormalizer.php
+++ b/src/platform/src/Bridge/Anthropic/Contract/MessageBagNormalizer.php
@@ -42,7 +42,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
         ];
 
         if (null !== $system = $data->getSystemMessage()) {
-            $array['system'] = $system->content;
+            $array['system'] = $system->getContent();
         }
 
         if (isset($context[Contract::CONTEXT_MODEL]) && $context[Contract::CONTEXT_MODEL] instanceof Model) {
diff --git a/src/platform/src/Bridge/Anthropic/Contract/ToolCallMessageNormalizer.php b/src/platform/src/Bridge/Anthropic/Contract/ToolCallMessageNormalizer.php
index cc561643c..a0a9b8786 100644
--- a/src/platform/src/Bridge/Anthropic/Contract/ToolCallMessageNormalizer.php
+++ b/src/platform/src/Bridge/Anthropic/Contract/ToolCallMessageNormalizer.php
@@ -44,8 +44,8 @@ public function normalize(mixed $data, ?string $format = null, array $context =
             'content' => [
                 [
                     'type' => 'tool_result',
-                    'tool_use_id' => $data->toolCall->getId(),
-                    'content' => $data->content,
+                    'tool_use_id' => $data->getToolCall()->getId(),
+                    'content' => $data->getContent(),
                 ],
             ],
         ];
diff --git a/src/platform/src/Bridge/Bedrock/Nova/Contract/AssistantMessageNormalizer.php b/src/platform/src/Bridge/Bedrock/Nova/Contract/AssistantMessageNormalizer.php
index 6df68a745..234e4c1fd 100644
--- a/src/platform/src/Bridge/Bedrock/Nova/Contract/AssistantMessageNormalizer.php
+++ b/src/platform/src/Bridge/Bedrock/Nova/Contract/AssistantMessageNormalizer.php
@@ -50,13 +50,13 @@ public function normalize(mixed $data, ?string $format = null, array $context =
                             'input' => [] !== $toolCall->getArguments() ? $toolCall->getArguments() : new \stdClass(),
                         ],
                     ];
-                }, $data->toolCalls),
+                }, $data->getToolCalls()),
             ];
         }
 
         return [
             'role' => 'assistant',
-            'content' => [['text' => $data->content]],
+            'content' => [['text' => $data->getContent()]],
         ];
     }
 
diff --git a/src/platform/src/Bridge/Bedrock/Nova/Contract/MessageBagNormalizer.php b/src/platform/src/Bridge/Bedrock/Nova/Contract/MessageBagNormalizer.php
index 51a5f24f7..732e812e3 100644
--- a/src/platform/src/Bridge/Bedrock/Nova/Contract/MessageBagNormalizer.php
+++ b/src/platform/src/Bridge/Bedrock/Nova/Contract/MessageBagNormalizer.php
@@ -38,7 +38,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
         $array = [];
 
         if ($data->getSystemMessage()) {
-            $array['system'][]['text'] = $data->getSystemMessage()->content;
+            $array['system'][]['text'] = $data->getSystemMessage()->getContent();
         }
 
         $array['messages'] = $this->normalizer->normalize($data->withoutSystemMessage()->getMessages(), $format, $context);
diff --git a/src/platform/src/Bridge/Bedrock/Nova/Contract/ToolCallMessageNormalizer.php b/src/platform/src/Bridge/Bedrock/Nova/Contract/ToolCallMessageNormalizer.php
index d6cf052ae..513a89244 100644
--- a/src/platform/src/Bridge/Bedrock/Nova/Contract/ToolCallMessageNormalizer.php
+++ b/src/platform/src/Bridge/Bedrock/Nova/Contract/ToolCallMessageNormalizer.php
@@ -45,8 +45,8 @@ public function normalize(mixed $data, ?string $format = null, array $context =
             'content' => [
                 [
                     'toolResult' => [
-                        'toolUseId' => $data->toolCall->getId(),
-                        'content' => [['json' => $data->content]],
+                        'toolUseId' => $data->getToolCall()->getId(),
+                        'content' => [['json' => $data->getContent()]],
                     ],
                 ],
             ],
diff --git a/src/platform/src/Bridge/Bedrock/Nova/Contract/UserMessageNormalizer.php b/src/platform/src/Bridge/Bedrock/Nova/Contract/UserMessageNormalizer.php
index efcfccb7d..ae3a622d0 100644
--- a/src/platform/src/Bridge/Bedrock/Nova/Contract/UserMessageNormalizer.php
+++ b/src/platform/src/Bridge/Bedrock/Nova/Contract/UserMessageNormalizer.php
@@ -44,10 +44,10 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         $array = ['role' => $data->getRole()->value];
 
-        foreach ($data->content as $value) {
+        foreach ($data->getContent() as $value) {
             $contentPart = [];
             if ($value instanceof Text) {
-                $contentPart['text'] = $value->text;
+                $contentPart['text'] = $value->getText();
             } elseif ($value instanceof Image) {
                 $contentPart['image']['format'] = u($value->getFormat())->replace('image/', '')->replace('jpg', 'jpeg')->toString();
                 $contentPart['image']['source']['bytes'] = $value->asBase64();
diff --git a/src/platform/src/Bridge/Gemini/Contract/AssistantMessageNormalizer.php b/src/platform/src/Bridge/Gemini/Contract/AssistantMessageNormalizer.php
index bc6ad687d..d41b7c294 100644
--- a/src/platform/src/Bridge/Gemini/Contract/AssistantMessageNormalizer.php
+++ b/src/platform/src/Bridge/Gemini/Contract/AssistantMessageNormalizer.php
@@ -30,18 +30,18 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         $normalized = [];
 
-        if (isset($data->content)) {
-            $normalized['text'] = $data->content;
+        if (null !== $data->getContent()) {
+            $normalized['text'] = $data->getContent();
         }
 
-        if (isset($data->toolCalls[0])) {
+        if ($data->hasToolCalls()) {
             $normalized['functionCall'] = [
-                'id' => $data->toolCalls[0]->getId(),
-                'name' => $data->toolCalls[0]->getName(),
+                'id' => $data->getToolCalls()[0]->getId(),
+                'name' => $data->getToolCalls()[0]->getName(),
             ];
 
-            if ($data->toolCalls[0]->getArguments()) {
-                $normalized['functionCall']['args'] = $data->toolCalls[0]->getArguments();
+            if ($data->getToolCalls()[0]->getArguments()) {
+                $normalized['functionCall']['args'] = $data->getToolCalls()[0]->getArguments();
             }
         }
 
diff --git a/src/platform/src/Bridge/Gemini/Contract/MessageBagNormalizer.php b/src/platform/src/Bridge/Gemini/Contract/MessageBagNormalizer.php
index fe133db53..c40370419 100644
--- a/src/platform/src/Bridge/Gemini/Contract/MessageBagNormalizer.php
+++ b/src/platform/src/Bridge/Gemini/Contract/MessageBagNormalizer.php
@@ -43,7 +43,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
 
         if (null !== $systemMessage = $data->getSystemMessage()) {
             $array['system_instruction'] = [
-                'parts' => [['text' => $systemMessage->content]],
+                'parts' => [['text' => $systemMessage->getContent()]],
             ];
         }
 
diff --git a/src/platform/src/Bridge/Gemini/Contract/ToolCallMessageNormalizer.php b/src/platform/src/Bridge/Gemini/Contract/ToolCallMessageNormalizer.php
index 2053aa532..31bcc39e6 100644
--- a/src/platform/src/Bridge/Gemini/Contract/ToolCallMessageNormalizer.php
+++ b/src/platform/src/Bridge/Gemini/Contract/ToolCallMessageNormalizer.php
@@ -34,12 +34,13 @@ final class ToolCallMessageNormalizer extends ModelContractNormalizer
      */
     public function normalize(mixed $data, ?string $format = null, array $context = []): array
     {
-        $resultContent = json_validate($data->content) ? json_decode($data->content, true) : $data->content;
+        $resultContent = json_validate($data->getContent())
+            ? json_decode($data->getContent(), true) : $data->getContent();
 
         return [[
             'functionResponse' => array_filter([
-                'id' => $data->toolCall->getId(),
-                'name' => $data->toolCall->getName(),
+                'id' => $data->getToolCall()->getId(),
+                'name' => $data->getToolCall()->getName(),
                 'response' => \is_array($resultContent) ? $resultContent : [
                     'rawResponse' => $resultContent, // Gemini expects the response to be an object, but not everyone uses objects as their responses.
                 ],
diff --git a/src/platform/src/Bridge/Gemini/Contract/UserMessageNormalizer.php b/src/platform/src/Bridge/Gemini/Contract/UserMessageNormalizer.php
index e72d780ca..a59530e4a 100644
--- a/src/platform/src/Bridge/Gemini/Contract/UserMessageNormalizer.php
+++ b/src/platform/src/Bridge/Gemini/Contract/UserMessageNormalizer.php
@@ -31,9 +31,9 @@ final class UserMessageNormalizer extends ModelContractNormalizer
     public function normalize(mixed $data, ?string $format = null, array $context = []): array
     {
         $parts = [];
-        foreach ($data->content as $content) {
+        foreach ($data->getContent() as $content) {
             if ($content instanceof Text) {
-                $parts[] = ['text' => $content->text];
+                $parts[] = ['text' => $content->getText()];
             }
             if ($content instanceof File) {
                 $parts[] = ['inline_data' => [
diff --git a/src/platform/src/Bridge/Meta/LlamaPromptConverter.php b/src/platform/src/Bridge/Meta/LlamaPromptConverter.php
index 40c1efe2d..acdc3bc31 100644
--- a/src/platform/src/Bridge/Meta/LlamaPromptConverter.php
+++ b/src/platform/src/Bridge/Meta/LlamaPromptConverter.php
@@ -44,44 +44,44 @@ public function convertMessage(UserMessage|SystemMessage|AssistantMessage $messa
             return trim(<<<SYSTEM
                 <|begin_of_text|><|start_header_id|>system<|end_header_id|>
 
-                {$message->content}<|eot_id|>
+                {$message->getContent()}<|eot_id|>
                 SYSTEM);
         }
 
         if ($message instanceof AssistantMessage) {
-            if ('' === $message->content || null === $message->content) {
+            if ('' === $message->getContent() || null === $message->getContent()) {
                 return '';
             }
 
             return trim(<<<ASSISTANT
                 <|start_header_id|>{$message->getRole()->value}<|end_header_id|>
 
-                {$message->content}<|eot_id|>
+                {$message->getContent()}<|eot_id|>
                 ASSISTANT);
         }
 
         // Handling of UserMessage
-        $count = \count($message->content);
+        $count = \count($message->getContent());
 
         $contentParts = [];
         if ($count > 1) {
-            foreach ($message->content as $value) {
+            foreach ($message->getContent() as $value) {
                 if ($value instanceof Text) {
-                    $contentParts[] = $value->text;
+                    $contentParts[] = $value->getText();
                 }
 
                 if ($value instanceof ImageUrl) {
-                    $contentParts[] = $value->url;
+                    $contentParts[] = $value->getUrl();
                 }
             }
         } elseif (1 === $count) {
-            $value = $message->content[0];
+            $value = $message->getContent()[0];
             if ($value instanceof Text) {
-                $contentParts[] = $value->text;
+                $contentParts[] = $value->getText();
             }
 
             if ($value instanceof ImageUrl) {
-                $contentParts[] = $value->url;
+                $contentParts[] = $value->getUrl();
             }
         } else {
             throw new RuntimeException('Unsupported message type.');
diff --git a/src/platform/src/Bridge/Mistral/Contract/DocumentUrlNormalizer.php b/src/platform/src/Bridge/Mistral/Contract/DocumentUrlNormalizer.php
index 343e714d1..107b1a29a 100644
--- a/src/platform/src/Bridge/Mistral/Contract/DocumentUrlNormalizer.php
+++ b/src/platform/src/Bridge/Mistral/Contract/DocumentUrlNormalizer.php
@@ -27,7 +27,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         return [
             'type' => 'document_url',
-            'document_url' => $data->url,
+            'document_url' => $data->getUrl(),
         ];
     }
 
diff --git a/src/platform/src/Bridge/Ollama/Contract/AssistantMessageNormalizer.php b/src/platform/src/Bridge/Ollama/Contract/AssistantMessageNormalizer.php
index 7edc08c74..afd055798 100644
--- a/src/platform/src/Bridge/Ollama/Contract/AssistantMessageNormalizer.php
+++ b/src/platform/src/Bridge/Ollama/Contract/AssistantMessageNormalizer.php
@@ -46,7 +46,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         return [
             'role' => Role::Assistant,
-            'content' => $data->content ?? '',
+            'content' => $data->getContent() ?? '',
             'tool_calls' => array_values(array_map(function (ToolCall $message): array {
                 return [
                     'type' => 'function',
@@ -56,7 +56,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
                         'arguments' => [] === $message->getArguments() ? new \stdClass() : $message->getArguments(),
                     ],
                 ];
-            }, $data->toolCalls ?? [])),
+            }, $data->getToolCalls() ?? [])),
         ];
     }
 
diff --git a/src/platform/src/Bridge/Perplexity/Contract/FileUrlNormalizer.php b/src/platform/src/Bridge/Perplexity/Contract/FileUrlNormalizer.php
index 895f5c1bb..64299d55a 100644
--- a/src/platform/src/Bridge/Perplexity/Contract/FileUrlNormalizer.php
+++ b/src/platform/src/Bridge/Perplexity/Contract/FileUrlNormalizer.php
@@ -31,7 +31,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
         return [
             'type' => 'file_url',
             'file_url' => [
-                'url' => $data->url,
+                'url' => $data->getUrl(),
             ],
         ];
     }
diff --git a/src/platform/src/Bridge/VertexAi/Contract/AssistantMessageNormalizer.php b/src/platform/src/Bridge/VertexAi/Contract/AssistantMessageNormalizer.php
index 613e93fd3..c720e94bd 100644
--- a/src/platform/src/Bridge/VertexAi/Contract/AssistantMessageNormalizer.php
+++ b/src/platform/src/Bridge/VertexAi/Contract/AssistantMessageNormalizer.php
@@ -38,17 +38,17 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         $normalized = [];
 
-        if (isset($data->content)) {
-            $normalized[] = ['text' => $data->content];
+        if (null !== $data->getContent()) {
+            $normalized[] = ['text' => $data->getContent()];
         }
 
-        if (isset($data->toolCalls[0])) {
+        if ($data->hasToolCalls()) {
             $normalized['functionCall'] = [
-                'name' => $data->toolCalls[0]->getName(),
+                'name' => $data->getToolCalls()[0]->getName(),
             ];
 
-            if ($data->toolCalls[0]->getArguments()) {
-                $normalized['functionCall']['args'] = $data->toolCalls[0]->getArguments();
+            if ($data->getToolCalls()[0]->getArguments()) {
+                $normalized['functionCall']['args'] = $data->getToolCalls()[0]->getArguments();
             }
         }
 
diff --git a/src/platform/src/Bridge/VertexAi/Contract/MessageBagNormalizer.php b/src/platform/src/Bridge/VertexAi/Contract/MessageBagNormalizer.php
index 7b7a0b8de..29fe5763f 100644
--- a/src/platform/src/Bridge/VertexAi/Contract/MessageBagNormalizer.php
+++ b/src/platform/src/Bridge/VertexAi/Contract/MessageBagNormalizer.php
@@ -46,7 +46,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
 
         if (null !== $systemMessage = $data->getSystemMessage()) {
             $requestData['systemInstruction'] = [
-                'parts' => [['text' => $systemMessage->content]],
+                'parts' => [['text' => $systemMessage->getContent()]],
             ];
         }
 
diff --git a/src/platform/src/Bridge/VertexAi/Contract/ToolCallMessageNormalizer.php b/src/platform/src/Bridge/VertexAi/Contract/ToolCallMessageNormalizer.php
index 798637221..f21566b74 100644
--- a/src/platform/src/Bridge/VertexAi/Contract/ToolCallMessageNormalizer.php
+++ b/src/platform/src/Bridge/VertexAi/Contract/ToolCallMessageNormalizer.php
@@ -35,11 +35,11 @@ final class ToolCallMessageNormalizer extends ModelContractNormalizer
      */
     public function normalize(mixed $data, ?string $format = null, array $context = []): array
     {
-        $resultContent = json_validate($data->content) ? json_decode($data->content, true, 512, \JSON_THROW_ON_ERROR) : $data->content;
+        $resultContent = json_validate($data->getContent()) ? json_decode($data->getContent(), true, 512, \JSON_THROW_ON_ERROR) : $data->getContent();
 
         return [[
             'functionResponse' => array_filter([
-                'name' => $data->toolCall->getName(),
+                'name' => $data->getToolCall()->getName(),
                 'response' => \is_array($resultContent) ? $resultContent : [
                     'rawResponse' => $resultContent,
                 ],
diff --git a/src/platform/src/Bridge/VertexAi/Contract/UserMessageNormalizer.php b/src/platform/src/Bridge/VertexAi/Contract/UserMessageNormalizer.php
index eb91aa52b..95ddaddcd 100644
--- a/src/platform/src/Bridge/VertexAi/Contract/UserMessageNormalizer.php
+++ b/src/platform/src/Bridge/VertexAi/Contract/UserMessageNormalizer.php
@@ -31,9 +31,9 @@ final class UserMessageNormalizer extends ModelContractNormalizer
     public function normalize(mixed $data, ?string $format = null, array $context = []): array
     {
         $parts = [];
-        foreach ($data->content as $content) {
+        foreach ($data->getContent() as $content) {
             if ($content instanceof Text) {
-                $parts[] = ['text' => $content->text];
+                $parts[] = ['text' => $content->getText()];
             }
 
             if ($content instanceof File) {
diff --git a/src/platform/src/Contract/Normalizer/Message/AssistantMessageNormalizer.php b/src/platform/src/Contract/Normalizer/Message/AssistantMessageNormalizer.php
index ad61c8f79..c6d37bd70 100644
--- a/src/platform/src/Contract/Normalizer/Message/AssistantMessageNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/AssistantMessageNormalizer.php
@@ -46,12 +46,12 @@ public function normalize(mixed $data, ?string $format = null, array $context =
             'role' => $data->getRole()->value,
         ];
 
-        if (null !== $data->content) {
-            $array['content'] = $data->content;
+        if (null !== $data->getContent()) {
+            $array['content'] = $data->getContent();
         }
 
         if ($data->hasToolCalls()) {
-            $array['tool_calls'] = $this->normalizer->normalize($data->toolCalls, $format, $context);
+            $array['tool_calls'] = $this->normalizer->normalize($data->getToolCalls(), $format, $context);
         }
 
         return $array;
diff --git a/src/platform/src/Contract/Normalizer/Message/Content/ImageUrlNormalizer.php b/src/platform/src/Contract/Normalizer/Message/Content/ImageUrlNormalizer.php
index 6b61cd7da..4ab2808a4 100644
--- a/src/platform/src/Contract/Normalizer/Message/Content/ImageUrlNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/Content/ImageUrlNormalizer.php
@@ -40,7 +40,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         return [
             'type' => 'image_url',
-            'image_url' => ['url' => $data->url],
+            'image_url' => ['url' => $data->getUrl()],
         ];
     }
 }
diff --git a/src/platform/src/Contract/Normalizer/Message/Content/TextNormalizer.php b/src/platform/src/Contract/Normalizer/Message/Content/TextNormalizer.php
index 72860679d..4c29944ef 100644
--- a/src/platform/src/Contract/Normalizer/Message/Content/TextNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/Content/TextNormalizer.php
@@ -38,6 +38,6 @@ public function getSupportedTypes(?string $format): array
      */
     public function normalize(mixed $data, ?string $format = null, array $context = []): array
     {
-        return ['type' => 'text', 'text' => $data->text];
+        return ['type' => 'text', 'text' => $data->getText()];
     }
 }
diff --git a/src/platform/src/Contract/Normalizer/Message/SystemMessageNormalizer.php b/src/platform/src/Contract/Normalizer/Message/SystemMessageNormalizer.php
index 4985b87d1..c4eb7743e 100644
--- a/src/platform/src/Contract/Normalizer/Message/SystemMessageNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/SystemMessageNormalizer.php
@@ -40,7 +40,7 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         return [
             'role' => $data->getRole()->value,
-            'content' => $data->content,
+            'content' => $data->getContent(),
         ];
     }
 }
diff --git a/src/platform/src/Contract/Normalizer/Message/ToolCallMessageNormalizer.php b/src/platform/src/Contract/Normalizer/Message/ToolCallMessageNormalizer.php
index e4313d441..e75fa4990 100644
--- a/src/platform/src/Contract/Normalizer/Message/ToolCallMessageNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/ToolCallMessageNormalizer.php
@@ -36,6 +36,8 @@ public function getSupportedTypes(?string $format): array
     }
 
     /**
+     * @param ToolCallMessage $data
+     *
      * @return array{
      *     role: 'tool',
      *     content: string,
@@ -46,8 +48,8 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         return [
             'role' => $data->getRole()->value,
-            'content' => $this->normalizer->normalize($data->content, $format, $context),
-            'tool_call_id' => $data->toolCall->getId(),
+            'content' => $this->normalizer->normalize($data->getContent(), $format, $context),
+            'tool_call_id' => $data->getToolCall()->getId(),
         ];
     }
 }
diff --git a/src/platform/src/Contract/Normalizer/Message/UserMessageNormalizer.php b/src/platform/src/Contract/Normalizer/Message/UserMessageNormalizer.php
index af7794f5c..0af599809 100644
--- a/src/platform/src/Contract/Normalizer/Message/UserMessageNormalizer.php
+++ b/src/platform/src/Contract/Normalizer/Message/UserMessageNormalizer.php
@@ -45,13 +45,13 @@ public function normalize(mixed $data, ?string $format = null, array $context =
     {
         $array = ['role' => $data->getRole()->value];
 
-        if (1 === \count($data->content) && $data->content[0] instanceof Text) {
-            $array['content'] = $data->content[0]->text;
+        if (1 === \count($data->getContent()) && $data->getContent()[0] instanceof Text) {
+            $array['content'] = $data->getContent()[0]->getText();
 
             return $array;
         }
 
-        $array['content'] = $this->normalizer->normalize($data->content, $format, $context);
+        $array['content'] = $this->normalizer->normalize($data->getContent(), $format, $context);
 
         return $array;
     }
diff --git a/src/platform/src/Message/AssistantMessage.php b/src/platform/src/Message/AssistantMessage.php
index 3a5a17410..3bb7370b2 100644
--- a/src/platform/src/Message/AssistantMessage.php
+++ b/src/platform/src/Message/AssistantMessage.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\AI\Platform\Message;
 
+use Symfony\AI\Platform\Metadata\MetadataAwareTrait;
 use Symfony\AI\Platform\Result\ToolCall;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
@@ -19,16 +20,18 @@
 /**
  * @author Denis Zunke <denis.zunke@gmail.com>
  */
-final readonly class AssistantMessage implements MessageInterface
+final class AssistantMessage implements MessageInterface
 {
-    public AbstractUid&TimeBasedUidInterface $id;
+    use MetadataAwareTrait;
+
+    private readonly AbstractUid&TimeBasedUidInterface $id;
 
     /**
      * @param ?ToolCall[] $toolCalls
      */
     public function __construct(
-        public ?string $content = null,
-        public ?array $toolCalls = null,
+        private ?string $content = null,
+        private ?array $toolCalls = null,
     ) {
         $this->id = Uuid::v7();
     }
@@ -47,4 +50,17 @@ public function hasToolCalls(): bool
     {
         return null !== $this->toolCalls && [] !== $this->toolCalls;
     }
+
+    /**
+     * @return ?ToolCall[]
+     */
+    public function getToolCalls(): ?array
+    {
+        return $this->toolCalls;
+    }
+
+    public function getContent(): ?string
+    {
+        return $this->content;
+    }
 }
diff --git a/src/platform/src/Message/Content/DocumentUrl.php b/src/platform/src/Message/Content/DocumentUrl.php
index e44e9e562..dea8507ca 100644
--- a/src/platform/src/Message/Content/DocumentUrl.php
+++ b/src/platform/src/Message/Content/DocumentUrl.php
@@ -17,7 +17,12 @@
 final readonly class DocumentUrl implements ContentInterface
 {
     public function __construct(
-        public string $url,
+        private string $url,
     ) {
     }
+
+    public function getUrl(): string
+    {
+        return $this->url;
+    }
 }
diff --git a/src/platform/src/Message/Content/ImageUrl.php b/src/platform/src/Message/Content/ImageUrl.php
index 63420ff4a..882e75837 100644
--- a/src/platform/src/Message/Content/ImageUrl.php
+++ b/src/platform/src/Message/Content/ImageUrl.php
@@ -17,7 +17,12 @@
 final readonly class ImageUrl implements ContentInterface
 {
     public function __construct(
-        public string $url,
+        private string $url,
     ) {
     }
+
+    public function getUrl(): string
+    {
+        return $this->url;
+    }
 }
diff --git a/src/platform/src/Message/Content/Text.php b/src/platform/src/Message/Content/Text.php
index ddf371aff..362816c02 100644
--- a/src/platform/src/Message/Content/Text.php
+++ b/src/platform/src/Message/Content/Text.php
@@ -17,7 +17,12 @@
 final readonly class Text implements ContentInterface
 {
     public function __construct(
-        public string $text,
+        private string $text,
     ) {
     }
+
+    public function getText(): string
+    {
+        return $this->text;
+    }
 }
diff --git a/src/platform/src/Message/MessageInterface.php b/src/platform/src/Message/MessageInterface.php
index 7baefe64d..7ca9229c6 100644
--- a/src/platform/src/Message/MessageInterface.php
+++ b/src/platform/src/Message/MessageInterface.php
@@ -11,6 +11,8 @@
 
 namespace Symfony\AI\Platform\Message;
 
+use Symfony\AI\Platform\Message\Content\ContentInterface;
+use Symfony\AI\Platform\Metadata\Metadata;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
 
@@ -22,4 +24,11 @@ interface MessageInterface
     public function getRole(): Role;
 
     public function getId(): AbstractUid&TimeBasedUidInterface;
+
+    /**
+     * @return string|ContentInterface[]|null
+     */
+    public function getContent(): string|array|null;
+
+    public function getMetadata(): Metadata;
 }
diff --git a/src/platform/src/Message/SystemMessage.php b/src/platform/src/Message/SystemMessage.php
index 98fc69587..d0650773a 100644
--- a/src/platform/src/Message/SystemMessage.php
+++ b/src/platform/src/Message/SystemMessage.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\AI\Platform\Message;
 
+use Symfony\AI\Platform\Metadata\MetadataAwareTrait;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
 use Symfony\Component\Uid\Uuid;
@@ -18,12 +19,15 @@
 /**
  * @author Denis Zunke <denis.zunke@gmail.com>
  */
-final readonly class SystemMessage implements MessageInterface
+final class SystemMessage implements MessageInterface
 {
-    public AbstractUid&TimeBasedUidInterface $id;
+    use MetadataAwareTrait;
 
-    public function __construct(public string $content)
-    {
+    private readonly AbstractUid&TimeBasedUidInterface $id;
+
+    public function __construct(
+        private readonly string $content,
+    ) {
         $this->id = Uuid::v7();
     }
 
@@ -36,4 +40,9 @@ public function getId(): AbstractUid&TimeBasedUidInterface
     {
         return $this->id;
     }
+
+    public function getContent(): string
+    {
+        return $this->content;
+    }
 }
diff --git a/src/platform/src/Message/ToolCallMessage.php b/src/platform/src/Message/ToolCallMessage.php
index 19beb7fba..c664c6b7b 100644
--- a/src/platform/src/Message/ToolCallMessage.php
+++ b/src/platform/src/Message/ToolCallMessage.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\AI\Platform\Message;
 
+use Symfony\AI\Platform\Metadata\MetadataAwareTrait;
 use Symfony\AI\Platform\Result\ToolCall;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
@@ -19,13 +20,15 @@
 /**
  * @author Denis Zunke <denis.zunke@gmail.com>
  */
-final readonly class ToolCallMessage implements MessageInterface
+final class ToolCallMessage implements MessageInterface
 {
-    public AbstractUid&TimeBasedUidInterface $id;
+    use MetadataAwareTrait;
+
+    private readonly AbstractUid&TimeBasedUidInterface $id;
 
     public function __construct(
-        public ToolCall $toolCall,
-        public string $content,
+        private readonly ToolCall $toolCall,
+        private readonly string $content,
     ) {
         $this->id = Uuid::v7();
     }
@@ -39,4 +42,14 @@ public function getId(): AbstractUid&TimeBasedUidInterface
     {
         return $this->id;
     }
+
+    public function getToolCall(): ToolCall
+    {
+        return $this->toolCall;
+    }
+
+    public function getContent(): string
+    {
+        return $this->content;
+    }
 }
diff --git a/src/platform/src/Message/UserMessage.php b/src/platform/src/Message/UserMessage.php
index e7485c932..445af64c3 100644
--- a/src/platform/src/Message/UserMessage.php
+++ b/src/platform/src/Message/UserMessage.php
@@ -16,6 +16,7 @@
 use Symfony\AI\Platform\Message\Content\Image;
 use Symfony\AI\Platform\Message\Content\ImageUrl;
 use Symfony\AI\Platform\Message\Content\Text;
+use Symfony\AI\Platform\Metadata\MetadataAwareTrait;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
 use Symfony\Component\Uid\Uuid;
@@ -23,14 +24,16 @@
 /**
  * @author Denis Zunke <denis.zunke@gmail.com>
  */
-final readonly class UserMessage implements MessageInterface
+final class UserMessage implements MessageInterface
 {
+    use MetadataAwareTrait;
+
     /**
-     * @var list<ContentInterface>
+     * @var ContentInterface[]
      */
-    public array $content;
+    private readonly array $content;
 
-    public AbstractUid&TimeBasedUidInterface $id;
+    private readonly AbstractUid&TimeBasedUidInterface $id;
 
     public function __construct(
         ContentInterface ...$content,
@@ -49,6 +52,14 @@ public function getId(): AbstractUid&TimeBasedUidInterface
         return $this->id;
     }
 
+    /**
+     * @return ContentInterface[]
+     */
+    public function getContent(): array
+    {
+        return $this->content;
+    }
+
     public function hasAudioContent(): bool
     {
         foreach ($this->content as $content) {
@@ -76,7 +87,7 @@ public function asText(): ?string
         $textParts = [];
         foreach ($this->content as $content) {
             if ($content instanceof Text) {
-                $textParts[] = $content->text;
+                $textParts[] = $content->getText();
             }
         }
 
diff --git a/src/platform/tests/Contract/Normalizer/Message/AssistantMessageNormalizerTest.php b/src/platform/tests/Contract/Normalizer/Message/AssistantMessageNormalizerTest.php
index a9e645abf..f057c476f 100644
--- a/src/platform/tests/Contract/Normalizer/Message/AssistantMessageNormalizerTest.php
+++ b/src/platform/tests/Contract/Normalizer/Message/AssistantMessageNormalizerTest.php
@@ -65,7 +65,7 @@ public function testNormalizeWithToolCalls()
         $innerNormalizer = $this->createMock(NormalizerInterface::class);
         $innerNormalizer->expects($this->once())
             ->method('normalize')
-            ->with($message->toolCalls, null, [])
+            ->with($message->getToolCalls(), null, [])
             ->willReturn($expectedToolCalls);
 
         $this->normalizer->setNormalizer($innerNormalizer);
@@ -89,7 +89,7 @@ public function testNormalizeWithNullContent()
         $innerNormalizer = $this->createMock(NormalizerInterface::class);
         $innerNormalizer->expects($this->once())
             ->method('normalize')
-            ->with($message->toolCalls, null, [])
+            ->with($message->getToolCalls(), null, [])
             ->willReturn($expectedToolCalls);
 
         $this->normalizer->setNormalizer($innerNormalizer);
diff --git a/src/platform/tests/Contract/Normalizer/Message/ToolCallMessageNormalizerTest.php b/src/platform/tests/Contract/Normalizer/Message/ToolCallMessageNormalizerTest.php
index 4e31cfd35..079ba18fe 100644
--- a/src/platform/tests/Contract/Normalizer/Message/ToolCallMessageNormalizerTest.php
+++ b/src/platform/tests/Contract/Normalizer/Message/ToolCallMessageNormalizerTest.php
@@ -48,7 +48,7 @@ public function testNormalize()
         $innerNormalizer = $this->createMock(NormalizerInterface::class);
         $innerNormalizer->expects($this->once())
             ->method('normalize')
-            ->with($message->content, null, [])
+            ->with($message->getContent(), null, [])
             ->willReturn($expectedContent);
 
         $this->normalizer->setNormalizer($innerNormalizer);
diff --git a/src/platform/tests/Contract/Normalizer/Message/UserMessageNormalizerTest.php b/src/platform/tests/Contract/Normalizer/Message/UserMessageNormalizerTest.php
index 81760d8d1..23aacfc6f 100644
--- a/src/platform/tests/Contract/Normalizer/Message/UserMessageNormalizerTest.php
+++ b/src/platform/tests/Contract/Normalizer/Message/UserMessageNormalizerTest.php
@@ -65,7 +65,7 @@ public function testNormalizeWithMixedContent()
         $innerNormalizer = $this->createMock(NormalizerInterface::class);
         $innerNormalizer->expects($this->once())
             ->method('normalize')
-            ->with($message->content, null, [])
+            ->with($message->getContent(), null, [])
             ->willReturn($expectedContent);
 
         $this->normalizer->setNormalizer($innerNormalizer);
diff --git a/src/platform/tests/ContractTest.php b/src/platform/tests/ContractTest.php
index f53d1f083..64bf3ee5d 100644
--- a/src/platform/tests/ContractTest.php
+++ b/src/platform/tests/ContractTest.php
@@ -22,10 +22,12 @@
 use Symfony\AI\Platform\Message\Content\Audio;
 use Symfony\AI\Platform\Message\Content\Image;
 use Symfony\AI\Platform\Message\Content\ImageUrl;
+use Symfony\AI\Platform\Message\Content\Text;
 use Symfony\AI\Platform\Message\Message;
 use Symfony\AI\Platform\Message\MessageBag;
 use Symfony\AI\Platform\Message\MessageInterface;
 use Symfony\AI\Platform\Message\Role;
+use Symfony\AI\Platform\Metadata\MetadataAwareTrait;
 use Symfony\AI\Platform\Model;
 use Symfony\Component\Uid\AbstractUid;
 use Symfony\Component\Uid\TimeBasedUidInterface;
@@ -172,6 +174,8 @@ public static function providePayloadTestCases(): iterable
         ];
 
         $customSerializableMessage = new class implements MessageInterface, \JsonSerializable {
+            use MetadataAwareTrait;
+
             public function getRole(): Role
             {
                 return Role::User;
@@ -182,6 +186,11 @@ public function getId(): AbstractUid&TimeBasedUidInterface
                 return Uuid::v7();
             }
 
+            public function getContent(): array
+            {
+                return [new Text('This is a custom serializable message.')];
+            }
+
             public function jsonSerialize(): array
             {
                 return [
diff --git a/src/platform/tests/Message/AssistantMessageTest.php b/src/platform/tests/Message/AssistantMessageTest.php
index f6767f186..d3883d28f 100644
--- a/src/platform/tests/Message/AssistantMessageTest.php
+++ b/src/platform/tests/Message/AssistantMessageTest.php
@@ -33,8 +33,8 @@ public function testConstructionWithoutToolCallIsPossible()
     {
         $message = new AssistantMessage('foo');
 
-        $this->assertSame('foo', $message->content);
-        $this->assertNull($message->toolCalls);
+        $this->assertSame('foo', $message->getContent());
+        $this->assertNull($message->getToolCalls());
     }
 
     public function testConstructionWithoutContentIsPossible()
@@ -42,8 +42,8 @@ public function testConstructionWithoutContentIsPossible()
         $toolCall = new ToolCall('foo', 'foo');
         $message = new AssistantMessage(toolCalls: [$toolCall]);
 
-        $this->assertNull($message->content);
-        $this->assertSame([$toolCall], $message->toolCalls);
+        $this->assertNull($message->getContent());
+        $this->assertSame([$toolCall], $message->getToolCalls());
         $this->assertTrue($message->hasToolCalls());
     }
 
@@ -51,9 +51,7 @@ public function testMessageHasUid()
     {
         $message = new AssistantMessage('foo');
 
-        $this->assertInstanceOf(UuidV7::class, $message->id);
         $this->assertInstanceOf(UuidV7::class, $message->getId());
-        $this->assertSame($message->id, $message->getId());
     }
 
     public function testDifferentMessagesHaveDifferentUids()
diff --git a/src/platform/tests/Message/Content/ImageUrlTest.php b/src/platform/tests/Message/Content/ImageUrlTest.php
index 3e0d25b41..9237ca0b1 100644
--- a/src/platform/tests/Message/Content/ImageUrlTest.php
+++ b/src/platform/tests/Message/Content/ImageUrlTest.php
@@ -20,6 +20,6 @@ public function testConstructWithValidUrl()
     {
         $image = new ImageUrl('https://foo.com/test.png');
 
-        $this->assertSame('https://foo.com/test.png', $image->url);
+        $this->assertSame('https://foo.com/test.png', $image->getUrl());
     }
 }
diff --git a/src/platform/tests/Message/Content/TextTest.php b/src/platform/tests/Message/Content/TextTest.php
index 07ace8d53..7c9341e54 100644
--- a/src/platform/tests/Message/Content/TextTest.php
+++ b/src/platform/tests/Message/Content/TextTest.php
@@ -20,6 +20,6 @@ public function testConstructionIsPossible()
     {
         $obj = new Text('foo');
 
-        $this->assertSame('foo', $obj->text);
+        $this->assertSame('foo', $obj->getText());
     }
 }
diff --git a/src/platform/tests/Message/MessageBagTest.php b/src/platform/tests/Message/MessageBagTest.php
index a66072396..cbe88e179 100644
--- a/src/platform/tests/Message/MessageBagTest.php
+++ b/src/platform/tests/Message/MessageBagTest.php
@@ -34,7 +34,7 @@ public function testGetSystemMessage()
 
         $systemMessage = $messageBag->getSystemMessage();
 
-        $this->assertSame('My amazing system prompt.', $systemMessage->content);
+        $this->assertSame('My amazing system prompt.', $systemMessage->getContent());
     }
 
     public function testGetSystemMessageWithoutSystemMessage()
@@ -65,7 +65,7 @@ public function testWith()
         $newMessageFromBag = $newMessageBag->getMessages()[3];
 
         $this->assertInstanceOf(AssistantMessage::class, $newMessageFromBag);
-        $this->assertSame('It is time to wake up.', $newMessageFromBag->content);
+        $this->assertSame('It is time to wake up.', $newMessageFromBag->getContent());
     }
 
     public function testMerge()
@@ -85,7 +85,7 @@ public function testMerge()
         $messageFromBag = $messageBag->getMessages()[3];
 
         $this->assertInstanceOf(AssistantMessage::class, $messageFromBag);
-        $this->assertSame('It is time to wake up.', $messageFromBag->content);
+        $this->assertSame('It is time to wake up.', $messageFromBag->getContent());
     }
 
     public function testWithoutSystemMessage()
@@ -105,12 +105,12 @@ public function testWithoutSystemMessage()
 
         $assistantMessage = $newMessageBag->getMessages()[0];
         $this->assertInstanceOf(AssistantMessage::class, $assistantMessage);
-        $this->assertSame('It is time to sleep.', $assistantMessage->content);
+        $this->assertSame('It is time to sleep.', $assistantMessage->getContent());
 
         $userMessage = $newMessageBag->getMessages()[1];
         $this->assertInstanceOf(UserMessage::class, $userMessage);
-        $this->assertInstanceOf(Text::class, $userMessage->content[0]);
-        $this->assertSame('Hello, world!', $userMessage->content[0]->text);
+        $this->assertInstanceOf(Text::class, $userMessage->getContent()[0]);
+        $this->assertSame('Hello, world!', $userMessage->getContent()[0]->getText());
     }
 
     public function testPrepend()
@@ -129,7 +129,7 @@ public function testPrepend()
         $newMessageBagMessage = $newMessageBag->getMessages()[0];
 
         $this->assertInstanceOf(SystemMessage::class, $newMessageBagMessage);
-        $this->assertSame('My amazing system prompt.', $newMessageBagMessage->content);
+        $this->assertSame('My amazing system prompt.', $newMessageBagMessage->getContent());
     }
 
     public function testContainsImageReturnsFalseWithoutImage()
@@ -178,8 +178,8 @@ public function testGetUserMessage()
         $userMessage = $messageBag->getUserMessage();
 
         $this->assertInstanceOf(UserMessage::class, $userMessage);
-        $this->assertInstanceOf(Text::class, $userMessage->content[0]);
-        $this->assertSame('Hello, world!', $userMessage->content[0]->text);
+        $this->assertInstanceOf(Text::class, $userMessage->getContent()[0]);
+        $this->assertSame('Hello, world!', $userMessage->getContent()[0]->getText());
     }
 
     public function testGetUserMessageReturnsNullWithoutUserMessage()
@@ -204,8 +204,8 @@ public function testGetUserMessageReturnsFirstUserMessage()
         $userMessage = $messageBag->getUserMessage();
 
         $this->assertInstanceOf(UserMessage::class, $userMessage);
-        $this->assertInstanceOf(Text::class, $userMessage->content[0]);
-        $this->assertSame('First user message', $userMessage->content[0]->text);
+        $this->assertInstanceOf(Text::class, $userMessage->getContent()[0]);
+        $this->assertSame('First user message', $userMessage->getContent()[0]->getText());
     }
 
     public function testGetUserMessageText()
diff --git a/src/platform/tests/Message/MessageTest.php b/src/platform/tests/Message/MessageTest.php
index c31a75128..b31a6b238 100644
--- a/src/platform/tests/Message/MessageTest.php
+++ b/src/platform/tests/Message/MessageTest.php
@@ -24,7 +24,7 @@ public function testCreateSystemMessageWithString()
     {
         $message = Message::forSystem('My amazing system prompt.');
 
-        $this->assertSame('My amazing system prompt.', $message->content);
+        $this->assertSame('My amazing system prompt.', $message->getContent());
     }
 
     public function testCreateSystemMessageWithStringable()
@@ -36,14 +36,14 @@ public function __toString(): string
             }
         });
 
-        $this->assertSame('My amazing system prompt.', $message->content);
+        $this->assertSame('My amazing system prompt.', $message->getContent());
     }
 
     public function testCreateAssistantMessage()
     {
         $message = Message::ofAssistant('It is time to sleep.');
 
-        $this->assertSame('It is time to sleep.', $message->content);
+        $this->assertSame('It is time to sleep.', $message->getContent());
     }
 
     public function testCreateAssistantMessageWithToolCalls()
@@ -54,7 +54,7 @@ public function testCreateAssistantMessageWithToolCalls()
         ];
         $message = Message::ofAssistant(toolCalls: $toolCalls);
 
-        $this->assertCount(2, $message->toolCalls);
+        $this->assertCount(2, $message->getToolCalls());
         $this->assertTrue($message->hasToolCalls());
     }
 
@@ -62,9 +62,9 @@ public function testCreateUserMessageWithString()
     {
         $message = Message::ofUser('Hi, my name is John.');
 
-        $this->assertCount(1, $message->content);
-        $this->assertInstanceOf(Text::class, $message->content[0]);
-        $this->assertSame('Hi, my name is John.', $message->content[0]->text);
+        $this->assertCount(1, $message->getContent());
+        $this->assertInstanceOf(Text::class, $message->getContent()[0]);
+        $this->assertSame('Hi, my name is John.', $message->getContent()[0]->getText());
     }
 
     public function testCreateUserMessageWithStringable()
@@ -76,9 +76,9 @@ public function __toString(): string
             }
         });
 
-        $this->assertCount(1, $message->content);
-        $this->assertInstanceOf(Text::class, $message->content[0]);
-        $this->assertSame('Hi, my name is John.', $message->content[0]->text);
+        $this->assertCount(1, $message->getContent());
+        $this->assertInstanceOf(Text::class, $message->getContent()[0]);
+        $this->assertSame('Hi, my name is John.', $message->getContent()[0]->getText());
     }
 
     public function testCreateUserMessageContentInterfaceImplementingStringable()
@@ -90,8 +90,8 @@ public function __toString(): string
             }
         });
 
-        $this->assertCount(1, $message->content);
-        $this->assertInstanceOf(ContentInterface::class, $message->content[0]);
+        $this->assertCount(1, $message->getContent());
+        $this->assertInstanceOf(ContentInterface::class, $message->getContent()[0]);
     }
 
     public function testCreateUserMessageWithTextContent()
@@ -99,7 +99,7 @@ public function testCreateUserMessageWithTextContent()
         $text = new Text('Hi, my name is John.');
         $message = Message::ofUser($text);
 
-        $this->assertSame([$text], $message->content);
+        $this->assertSame([$text], $message->getContent());
     }
 
     public function testCreateUserMessageWithImages()
@@ -111,7 +111,7 @@ public function testCreateUserMessageWithImages()
             new ImageUrl('http://images.local/my-image2.png'),
         );
 
-        $this->assertCount(4, $message->content);
+        $this->assertCount(4, $message->getContent());
     }
 
     public function testCreateToolCallMessage()
@@ -119,7 +119,7 @@ public function testCreateToolCallMessage()
         $toolCall = new ToolCall('call_123456', 'my_tool', ['foo' => 'bar']);
         $message = Message::ofToolCall($toolCall, 'Foo bar.');
 
-        $this->assertSame('Foo bar.', $message->content);
-        $this->assertSame($toolCall, $message->toolCall);
+        $this->assertSame('Foo bar.', $message->getContent());
+        $this->assertSame($toolCall, $message->getToolCall());
     }
 }
diff --git a/src/platform/tests/Message/SystemMessageTest.php b/src/platform/tests/Message/SystemMessageTest.php
index 0d88f91d3..0d8df0e48 100644
--- a/src/platform/tests/Message/SystemMessageTest.php
+++ b/src/platform/tests/Message/SystemMessageTest.php
@@ -28,16 +28,14 @@ public function testConstructionIsPossible()
         $message = new SystemMessage('foo');
 
         $this->assertSame(Role::System, $message->getRole());
-        $this->assertSame('foo', $message->content);
+        $this->assertSame('foo', $message->getContent());
     }
 
     public function testMessageHasUid()
     {
         $message = new SystemMessage('foo');
 
-        $this->assertInstanceOf(UuidV7::class, $message->id);
         $this->assertInstanceOf(UuidV7::class, $message->getId());
-        $this->assertSame($message->id, $message->getId());
     }
 
     public function testDifferentMessagesHaveDifferentUids()
diff --git a/src/platform/tests/Message/ToolCallMessageTest.php b/src/platform/tests/Message/ToolCallMessageTest.php
index fde79f25d..eccf06bc4 100644
--- a/src/platform/tests/Message/ToolCallMessageTest.php
+++ b/src/platform/tests/Message/ToolCallMessageTest.php
@@ -28,8 +28,8 @@ public function testConstructionIsPossible()
         $toolCall = new ToolCall('foo', 'bar');
         $obj = new ToolCallMessage($toolCall, 'bar');
 
-        $this->assertSame($toolCall, $obj->toolCall);
-        $this->assertSame('bar', $obj->content);
+        $this->assertSame($toolCall, $obj->getToolCall());
+        $this->assertSame('bar', $obj->getContent());
     }
 
     public function testMessageHasUid()
@@ -37,9 +37,7 @@ public function testMessageHasUid()
         $toolCall = new ToolCall('foo', 'bar');
         $message = new ToolCallMessage($toolCall, 'bar');
 
-        $this->assertInstanceOf(UuidV7::class, $message->id);
         $this->assertInstanceOf(UuidV7::class, $message->getId());
-        $this->assertSame($message->id, $message->getId());
     }
 
     public function testDifferentMessagesHaveDifferentUids()
diff --git a/src/platform/tests/Message/UserMessageTest.php b/src/platform/tests/Message/UserMessageTest.php
index adc9dea20..155a6366a 100644
--- a/src/platform/tests/Message/UserMessageTest.php
+++ b/src/platform/tests/Message/UserMessageTest.php
@@ -31,16 +31,16 @@ public function testConstructionIsPossible()
         $obj = new UserMessage(new Text('foo'));
 
         $this->assertSame(Role::User, $obj->getRole());
-        $this->assertCount(1, $obj->content);
-        $this->assertInstanceOf(Text::class, $obj->content[0]);
-        $this->assertSame('foo', $obj->content[0]->text);
+        $this->assertCount(1, $obj->getContent());
+        $this->assertInstanceOf(Text::class, $obj->getContent()[0]);
+        $this->assertSame('foo', $obj->getContent()[0]->getText());
     }
 
     public function testConstructionIsPossibleWithMultipleContent()
     {
         $message = new UserMessage(new Text('foo'), new ImageUrl('https://foo.com/bar.jpg'));
 
-        $this->assertCount(2, $message->content);
+        $this->assertCount(2, $message->getContent());
     }
 
     public function testHasAudioContentWithoutAudio()
@@ -75,9 +75,7 @@ public function testMessageHasUid()
     {
         $message = new UserMessage(new Text('foo'));
 
-        $this->assertInstanceOf(UuidV7::class, $message->id);
         $this->assertInstanceOf(UuidV7::class, $message->getId());
-        $this->assertSame($message->id, $message->getId());
     }
 
     public function testDifferentMessagesHaveDifferentUids()