diff --git a/README.md b/README.md
index 47b4db7..8b4bf0a 100644
--- a/README.md
+++ b/README.md
@@ -56,15 +56,15 @@ int main() {
     // Ensure ANTHROPIC_API_KEY environment variable is set
     auto client = ai::anthropic::create_client();
     auto result = client.generate_text({
-        .model = ai::anthropic::models::kClaude35Sonnet,
+        .model = ai::anthropic::models::kClaudeSonnet45,
         .system = "You are a helpful assistant.",
         .prompt = "Explain quantum computing in simple terms."
     });
-    
+
     if (result) {
         std::cout << result->text << std::endl;
     }
-    
+
     return 0;
 }
 ```
diff --git a/examples/basic_chat.cpp b/examples/basic_chat.cpp
index e74e82e..76ecebe 100644
--- a/examples/basic_chat.cpp
+++ b/examples/basic_chat.cpp
@@ -98,7 +98,7 @@ int main() {
 
   auto client4 = ai::anthropic::create_client();
   ai::GenerateOptions options4;
-  options4.model = ai::anthropic::models::kClaudeSonnet35;
+  options4.model = ai::anthropic::models::kClaudeSonnet45;
   options4.prompt =
       "Write a haiku about programming. Just the haiku, nothing else.";
 
diff --git a/examples/components/all/main.cpp b/examples/components/all/main.cpp
index f0b2bc2..3139094 100644
--- a/examples/components/all/main.cpp
+++ b/examples/components/all/main.cpp
@@ -52,8 +52,8 @@ int main() {
     auto anthropic_client = ai::anthropic::create_client();
     std::cout << "✓ Anthropic client created successfully\n";
     std::cout << "✓ Available models: "
-              << ai::anthropic::models::kClaudeSonnet35 << ", "
-              << ai::anthropic::models::kClaudeHaiku35 << "\n";
+              << ai::anthropic::models::kClaudeSonnet45 << ", "
+              << ai::anthropic::models::kClaudeHaiku45 << "\n";
   } catch (const std::exception& e) {
     std::cout << "✗ Anthropic client failed: " << e.what() << "\n";
   }
diff --git a/examples/components/anthropic/main.cpp b/examples/components/anthropic/main.cpp
index e51f51c..d5a6340 100644
--- a/examples/components/anthropic/main.cpp
+++ b/examples/components/anthropic/main.cpp
@@ -26,7 +26,7 @@ int main() {
   // Test core functionality
   std::cout << "Testing core functionality...\n";
   ai::GenerateOptions options;
-  options.model = "claude-3-5-sonnet-20241022";
+  options.model = "claude-sonnet-4-5-20250929";
   options.prompt = "Hello world";
   std::cout << "✓ Core types work fine\n\n";
 
@@ -37,8 +37,8 @@ int main() {
     auto client = ai::anthropic::create_client();
     std::cout << "✓ Anthropic client created successfully\n";
     std::cout << "✓ Available models: "
-              << ai::anthropic::models::kClaudeSonnet35 << ", "
-              << ai::anthropic::models::kClaudeHaiku35 << "\n";
+              << ai::anthropic::models::kClaudeSonnet45 << ", "
+              << ai::anthropic::models::kClaudeHaiku45 << "\n";
   } catch (const std::exception& e) {
     std::cout << "✗ Anthropic client failed: " << e.what() << "\n";
   }
diff --git a/examples/multi_provider.cpp b/examples/multi_provider.cpp
index 433d39e..76b65db 100644
--- a/examples/multi_provider.cpp
+++ b/examples/multi_provider.cpp
@@ -94,9 +94,9 @@ int main() {
 
   // Test Anthropic models
   results1.push_back(test_provider(
-      "Anthropic", ai::anthropic::models::kClaudeSonnet35, simple_question));
+      "Anthropic", ai::anthropic::models::kClaudeSonnet45, simple_question));
   results1.push_back(test_provider(
-      "Anthropic", ai::anthropic::models::kClaudeHaiku35, simple_question));
+      "Anthropic", ai::anthropic::models::kClaudeHaiku45, simple_question));
 
   for (const auto& result : results1) {
     print_result(result);
@@ -118,7 +118,7 @@ int main() {
   results2.push_back(
       test_provider("OpenAI", ai::openai::models::kGpt4o, creative_prompt));
   results2.push_back(test_provider(
-      "Anthropic", ai::anthropic::models::kClaudeSonnet35, creative_prompt));
+      "Anthropic", ai::anthropic::models::kClaudeSonnet45, creative_prompt));
 
   for (const auto& result : results2) {
     print_result(result);
@@ -137,7 +137,7 @@ int main() {
   results3.push_back(
       test_provider("OpenAI", ai::openai::models::kGpt4o, technical_prompt));
   results3.push_back(test_provider(
-      "Anthropic", ai::anthropic::models::kClaudeSonnet35, technical_prompt));
+      "Anthropic", ai::anthropic::models::kClaudeSonnet45, technical_prompt));
 
   for (const auto& result : results3) {
     print_result(result);
diff --git a/examples/openrouter_example.cpp b/examples/openrouter_example.cpp
index c4b1fe9..0175787 100644
--- a/examples/openrouter_example.cpp
+++ b/examples/openrouter_example.cpp
@@ -32,11 +32,11 @@ int main() {
     std::cout << "Testing text generation with OpenRouter...\n\n";
 
     // Using a model that's available on OpenRouter
-    // Common models: "openai/gpt-3.5-turbo", "anthropic/claude-3.5-sonnet",
+    // Common models: "openai/gpt-4o", "anthropic/claude-sonnet-4-5",
     // "meta-llama/llama-3.1-8b-instruct" See https://openrouter.ai/models for
     // available models
     ai::GenerateOptions options(
-        "anthropic/claude-3.5-sonnet", "You are a helpful assistant.",
+        "anthropic/claude-sonnet-4-5", "You are a helpful assistant.",
         "What are the benefits of using OpenRouter for AI applications? Give a "
         "brief answer.");
 
@@ -55,7 +55,7 @@ int main() {
     // Test streaming with OpenRouter
     std::cout << "\n\nTesting streaming with OpenRouter...\n";
 
-    ai::GenerateOptions stream_opts("anthropic/claude-3.5-sonnet",
+    ai::GenerateOptions stream_opts("anthropic/claude-sonnet-4-5",
                                     "You are a creative writer.",
                                     "Write a haiku about API compatibility.");
     ai::StreamOptions stream_options(stream_opts);
diff --git a/examples/test_tool_integration.cpp b/examples/test_tool_integration.cpp
index d725279..ea7dacc 100644
--- a/examples/test_tool_integration.cpp
+++ b/examples/test_tool_integration.cpp
@@ -86,7 +86,7 @@ void test_anthropic_tools() {
                         {{"input", "string"}}, simple_test_tool)}};
 
   ai::GenerateOptions options;
-  options.model = ai::anthropic::models::kClaudeSonnet35;
+  options.model = ai::anthropic::models::kClaudeSonnet45;
   options.prompt = "Please use the test_tool with input 'hello anthropic'";
   options.tools = tools;
   options.tool_choice =
diff --git a/examples/tool_calling_async.cpp b/examples/tool_calling_async.cpp
index c536447..073383c 100644
--- a/examples/tool_calling_async.cpp
+++ b/examples/tool_calling_async.cpp
@@ -337,12 +337,12 @@ int main() {
 
   auto anthropic_client = ai::anthropic::create_client();
 
-  std::cout << "Testing async tools with Claude 3.5 Sonnet\n\n";
+  std::cout << "Testing async tools with Claude Sonnet 4.5\n\n";
 
   start_time = std::chrono::high_resolution_clock::now();
 
   ai::GenerateOptions anthropic_options;
-  anthropic_options.model = ai::anthropic::models::kClaudeSonnet35;
+  anthropic_options.model = ai::anthropic::models::kClaudeSonnet45;
   anthropic_options.prompt = R"(
     Please help me with these THREE tasks. You MUST use the tools to complete ALL of them:
     1. Use the fetch_news tool to get tech news articles  
diff --git a/include/ai/ai.h b/include/ai/ai.h
index 022712b..9a815d9 100644
--- a/include/ai/ai.h
+++ b/include/ai/ai.h
@@ -74,7 +74,7 @@
 /// ```cpp
 /// auto client = ai::anthropic::create_client();
 /// auto result = client.generate_text({
-///     .model = ai::anthropic::models::kClaude35Sonnet,
+///     .model = ai::anthropic::models::kClaudeSonnet45,
 ///     .system = "You are a helpful assistant.",
 ///     .prompt = "Explain quantum computing in simple terms."
 /// });
diff --git a/include/ai/anthropic.h b/include/ai/anthropic.h
index c750bc1..01ab168 100644
--- a/include/ai/anthropic.h
+++ b/include/ai/anthropic.h
@@ -14,7 +14,15 @@ namespace ai {
 namespace anthropic {
 
 namespace models {
-/// Common Anthropic model identifiers
+/// Common Anthropic model identifiers (Latest models)
+constexpr const char* kClaudeSonnet45 =
+    "claude-sonnet-4-5";  // claude-sonnet-4-5-20250929
+constexpr const char* kClaudeHaiku45 =
+    "claude-haiku-4-5";  // claude-haiku-4-5-20251001
+constexpr const char* kClaudeOpus41 =
+    "claude-opus-4-1";  // claude-opus-4-1-20250805
+
+/// Legacy model identifiers (retained for backward compatibility)
 constexpr const char* kClaudeOpus4 =
     "claude-opus-4-0";  // claude-opus-4-20250514
 constexpr const char* kClaudeSonnet4 =
@@ -22,12 +30,12 @@ constexpr const char* kClaudeSonnet4 =
 constexpr const char* kClaudeSonnet37 =
     "claude-3-7-sonnet-latest";  // claude-3-7-sonnet-20250219
 constexpr const char* kClaudeSonnet35 =
-    "claude-3-5-sonnet-latest";  // claude-3-5-sonnet-20241022
+    "claude-3-5-sonnet-latest";  // claude-3-5-sonnet-20241022 (DEPRECATED)
 constexpr const char* kClaudeHaiku35 =
     "claude-3-5-haiku-latest";  // claude-3-5-haiku-20241022
 
 /// Default model used when none is specified
-constexpr const char* kDefaultModel = kClaudeSonnet35;
+constexpr const char* kDefaultModel = kClaudeSonnet45;
 }  // namespace models
 
 /// Create an Anthropic client with default configuration
diff --git a/src/providers/anthropic/anthropic_client.cpp b/src/providers/anthropic/anthropic_client.cpp
index bedc098..337de98 100644
--- a/src/providers/anthropic/anthropic_client.cpp
+++ b/src/providers/anthropic/anthropic_client.cpp
@@ -59,8 +59,13 @@ std::string AnthropicClient::provider_name() const {
 }
 
 std::vector<std::string> AnthropicClient::supported_models() const {
-  return {"claude-3-5-sonnet-20241022", "claude-3-5-haiku-20241022",
-          "claude-3-opus-20240229", "claude-3-sonnet-20240229",
+  return {"claude-sonnet-4-5-20250929",  // Latest Sonnet 4.5
+          "claude-haiku-4-5-20251001",   // Latest Haiku 4.5
+          "claude-opus-4-1-20250805",    // Latest Opus 4.1
+          "claude-sonnet-4-20250514",    // Sonnet 4.0
+          "claude-3-5-sonnet-20241022",  // Legacy 3.5 Sonnet
+          "claude-3-5-haiku-20241022",   // Legacy 3.5 Haiku
+          "claude-3-opus-20240229",     "claude-3-sonnet-20240229",
           "claude-3-haiku-20240307"};
 }
 
diff --git a/tests/integration/anthropic_integration_test.cpp b/tests/integration/anthropic_integration_test.cpp
index d3a12fc..4ec6e5c 100644
--- a/tests/integration/anthropic_integration_test.cpp
+++ b/tests/integration/anthropic_integration_test.cpp
@@ -89,7 +89,7 @@ TEST_F(AnthropicIntegrationTest, TextGenerationWithParameters) {
                           "Write a very short story about a cat.");
   options.max_tokens = 50;
   options.temperature = 0.7;
-  options.top_p = 0.9;
+  // Note: Claude 4.5 doesn't allow both temperature and top_p to be set
 
   auto result = client_->generate_text(options);
 
@@ -135,7 +135,7 @@ TEST_F(AnthropicIntegrationTest, DifferentModelSupport) {
 
   std::vector<std::string> models_to_test = {
       ai::anthropic::models::kDefaultModel,
-      ai::anthropic::models::kClaudeHaiku35};
+      ai::anthropic::models::kClaudeHaiku45};
 
   for (const auto& model : models_to_test) {
     if (!client_->supports_model(model)) {
@@ -278,7 +278,7 @@ TEST_F(AnthropicIntegrationTest, LargePromptHandling) {
   auto large_prompt =
       TestDataGenerator::createLargePrompt(2000);  // ~2KB prompt
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35, large_prompt);
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45, large_prompt);
   auto result = client_->generate_text(options);
 
   TestAssertions::assertSuccess(result);
@@ -299,7 +299,7 @@ TEST_F(AnthropicIntegrationTest, CustomBaseUrl) {
   auto custom_client =
       ai::anthropic::create_client(api_key, "https://api.anthropic.com");
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35,
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45,
                           "Test custom base URL");
   auto result = custom_client.generate_text(options);
 
@@ -313,7 +313,7 @@ TEST_F(AnthropicIntegrationTest, EmptyPrompt) {
     GTEST_SKIP() << "No ANTHROPIC_API_KEY environment variable set";
   }
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35, "");
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45, "");
 
   // Empty prompt should be caught by validation
   EXPECT_FALSE(options.is_valid());
@@ -328,7 +328,7 @@ TEST_F(AnthropicIntegrationTest, VeryLongResponse) {
     GTEST_SKIP() << "No ANTHROPIC_API_KEY environment variable set";
   }
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35,
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45,
                           "Write a detailed explanation of quantum physics");
   options.max_tokens = 500;  // Reasonable limit for testing
 
@@ -349,7 +349,7 @@ TEST_F(AnthropicIntegrationTest, NetworkTimeout) {
 
   // Note: This test documents timeout behavior but cannot reliably trigger it
   // with the real API under normal conditions
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35,
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45,
                           "Simple test");
   auto result = client_->generate_text(options);
 
@@ -375,7 +375,7 @@ TEST_F(AnthropicIntegrationTest, NetworkFailure) {
   auto failing_client = ai::anthropic::create_client(
       api_key, "http://localhost:59999");  // Very unlikely port to be in use
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35,
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45,
                           "Test network failure");
   auto result = failing_client.generate_text(options);
 
@@ -426,7 +426,7 @@ TEST_F(AnthropicIntegrationTest, MaxTokensRequired) {
     GTEST_SKIP() << "No ANTHROPIC_API_KEY environment variable set";
   }
 
-  GenerateOptions options(ai::anthropic::models::kClaudeSonnet35,
+  GenerateOptions options(ai::anthropic::models::kClaudeSonnet45,
                           "Tell me about artificial intelligence");
   // Anthropic requires max_tokens to be set
   options.max_tokens = 100;
@@ -445,7 +445,7 @@ TEST_F(AnthropicIntegrationTest, SystemMessageHandling) {
 
   // Anthropic has specific handling for system messages
   GenerateOptions options(
-      ai::anthropic::models::kClaudeSonnet35,
+      ai::anthropic::models::kClaudeSonnet45,
       "You are Claude, an AI assistant created by Anthropic.",
       "What is your name?");
   options.max_tokens = 50;
@@ -475,11 +475,11 @@ TEST_F(AnthropicIntegrationTest, DefaultModelGeneration) {
   EXPECT_EQ(client_->default_model(), ai::anthropic::models::kDefaultModel);
   if (result.model.has_value()) {
     // Anthropic returns the full model version (e.g.,
-    // "claude-3-5-sonnet-20241022") while kDefaultModel is
-    // "claude-3-5-sonnet-latest"
-    EXPECT_TRUE(result.model.value().find("claude-3-5-sonnet") !=
+    // "claude-sonnet-4-5-20250929") while kDefaultModel is
+    // "claude-sonnet-4-5"
+    EXPECT_TRUE(result.model.value().find("claude-sonnet-4-5") !=
                 std::string::npos)
-        << "Expected model to contain 'claude-3-5-sonnet', but got: "
+        << "Expected model to contain 'claude-sonnet-4-5', but got: "
         << result.model.value();
   }
 }
diff --git a/tests/integration/multi_step_duplicate_execution_test.cpp b/tests/integration/multi_step_duplicate_execution_test.cpp
index f4b5088..7df0029 100644
--- a/tests/integration/multi_step_duplicate_execution_test.cpp
+++ b/tests/integration/multi_step_duplicate_execution_test.cpp
@@ -41,7 +41,7 @@ class MultiStepDuplicateExecutionTest
       if (api_key) {
         use_real_api_ = true;
         client_ = ai::anthropic::create_client(api_key);
-        model_ = ai::anthropic::models::kClaudeSonnet35;
+        model_ = ai::anthropic::models::kClaudeSonnet45;
       } else {
         use_real_api_ = false;
       }
diff --git a/tests/integration/tool_calling_integration_test.cpp b/tests/integration/tool_calling_integration_test.cpp
index 96e28d9..415cc98 100644
--- a/tests/integration/tool_calling_integration_test.cpp
+++ b/tests/integration/tool_calling_integration_test.cpp
@@ -146,7 +146,7 @@ class ToolCallingIntegrationTest
       if (api_key) {
         use_real_api_ = true;
         client_ = ai::anthropic::create_client(api_key);
-        model_ = ai::anthropic::models::kClaudeSonnet35;
+        model_ = ai::anthropic::models::kClaudeSonnet45;
       } else {
         use_real_api_ = false;
       }
@@ -672,7 +672,7 @@ class AnthropicSpecificToolTest : public ::testing::Test {
     if (api_key) {
       use_real_api_ = true;
       client_ = ai::anthropic::create_client(api_key);
-      model_ = ai::anthropic::models::kClaudeSonnet35;
+      model_ = ai::anthropic::models::kClaudeSonnet45;
     } else {
       use_real_api_ = false;
     }
@@ -698,8 +698,13 @@ TEST_F(AnthropicSpecificToolTest, MaxTokensRequiredWithTools) {
 
   auto result = client_->generate_text(options);
 
-  TestAssertions::assertSuccess(result);
-  EXPECT_FALSE(result.text.empty());
+  // Verify the request succeeded (may have tool calls instead of text)
+  EXPECT_TRUE(result.is_success())
+      << "Expected successful result but got error: " << result.error_message();
+  EXPECT_FALSE(result.error.has_value());
+
+  // Note: When tools are provided, the model may return tool calls instead of
+  // text This test just verifies that requests with tools + max_tokens succeed
   EXPECT_LE(result.usage.completion_tokens, 200);
 }
 
diff --git a/tests/unit/anthropic_client_test.cpp b/tests/unit/anthropic_client_test.cpp
index 521eb2b..07240a3 100644
--- a/tests/unit/anthropic_client_test.cpp
+++ b/tests/unit/anthropic_client_test.cpp
@@ -81,17 +81,17 @@ TEST_F(AnthropicClientTest, ConstructorWithHttpUrl) {
 TEST_F(AnthropicClientTest, SupportedModelsContainsExpectedModels) {
   auto models = client_->supported_models();
 
-  EXPECT_THAT(models, testing::Contains("claude-3-5-sonnet-20241022"));
-  EXPECT_THAT(models, testing::Contains("claude-3-haiku-20240307"));
-  EXPECT_THAT(models, testing::Contains("claude-3-opus-20240229"));
-  EXPECT_THAT(models, testing::Contains("claude-3-sonnet-20240229"));
+  EXPECT_THAT(models, testing::Contains("claude-sonnet-4-5-20250929"));
+  EXPECT_THAT(models, testing::Contains("claude-haiku-4-5-20251001"));
+  EXPECT_THAT(models, testing::Contains("claude-opus-4-1-20250805"));
+  EXPECT_THAT(models, testing::Contains("claude-sonnet-4-20250514"));
   EXPECT_FALSE(models.empty());
 }
 
 TEST_F(AnthropicClientTest, SupportsValidModel) {
-  EXPECT_TRUE(client_->supports_model("claude-3-5-sonnet-20241022"));
-  EXPECT_TRUE(client_->supports_model("claude-3-haiku-20240307"));
-  EXPECT_TRUE(client_->supports_model("claude-3-opus-20240229"));
+  EXPECT_TRUE(client_->supports_model("claude-sonnet-4-5-20250929"));
+  EXPECT_TRUE(client_->supports_model("claude-haiku-4-5-20251001"));
+  EXPECT_TRUE(client_->supports_model("claude-opus-4-1-20250805"));
 }
 
 TEST_F(AnthropicClientTest, DoesNotSupportInvalidModel) {
diff --git a/tests/unit/anthropic_stream_test.cpp b/tests/unit/anthropic_stream_test.cpp
index 350ab56..518eeef 100644
--- a/tests/unit/anthropic_stream_test.cpp
+++ b/tests/unit/anthropic_stream_test.cpp
@@ -15,19 +15,19 @@ class AnthropicStreamTest : public AnthropicTestFixture {};
 // StreamOptions Tests
 TEST_F(AnthropicStreamTest, StreamOptionsBasicConstructor) {
   StreamOptions options(
-      GenerateOptions("claude-3-5-sonnet-20241022", "Hello, world!"));
+      GenerateOptions("claude-sonnet-4-5-20250929", "Hello, world!"));
 
-  EXPECT_EQ(options.model, "claude-3-5-sonnet-20241022");
+  EXPECT_EQ(options.model, "claude-sonnet-4-5-20250929");
   EXPECT_EQ(options.prompt, "Hello, world!");
   EXPECT_TRUE(options.system.empty());
   EXPECT_TRUE(options.messages.empty());
 }
 
 TEST_F(AnthropicStreamTest, StreamOptionsWithSystemPrompt) {
-  StreamOptions options(GenerateOptions("claude-3-5-sonnet-20241022",
+  StreamOptions options(GenerateOptions("claude-sonnet-4-5-20250929",
                                         "System prompt", "User prompt"));
 
-  EXPECT_EQ(options.model, "claude-3-5-sonnet-20241022");
+  EXPECT_EQ(options.model, "claude-sonnet-4-5-20250929");
   EXPECT_EQ(options.system, "System prompt");
   EXPECT_EQ(options.prompt, "User prompt");
 }
@@ -35,23 +35,23 @@ TEST_F(AnthropicStreamTest, StreamOptionsWithSystemPrompt) {
 TEST_F(AnthropicStreamTest, StreamOptionsWithMessages) {
   Messages messages = createSampleAnthropicConversation();
   StreamOptions options(
-      GenerateOptions("claude-3-5-sonnet-20241022", std::move(messages)));
+      GenerateOptions("claude-sonnet-4-5-20250929", std::move(messages)));
 
-  EXPECT_EQ(options.model, "claude-3-5-sonnet-20241022");
+  EXPECT_EQ(options.model, "claude-sonnet-4-5-20250929");
   EXPECT_FALSE(options.messages.empty());
   EXPECT_TRUE(options.has_messages());
 }
 
 TEST_F(AnthropicStreamTest, StreamOptionsValidation) {
   StreamOptions valid_options(
-      GenerateOptions("claude-3-5-sonnet-20241022", "Valid prompt"));
+      GenerateOptions("claude-sonnet-4-5-20250929", "Valid prompt"));
   EXPECT_TRUE(valid_options.is_valid());
 
   StreamOptions invalid_model(GenerateOptions("", "Valid prompt"));
   EXPECT_FALSE(invalid_model.is_valid());
 
   StreamOptions invalid_prompt(
-      GenerateOptions("claude-3-5-sonnet-20241022", ""));
+      GenerateOptions("claude-sonnet-4-5-20250929", ""));
   EXPECT_FALSE(invalid_prompt.is_valid());
 }
 
@@ -190,7 +190,7 @@ class AnthropicStreamErrorTest : public AnthropicTestFixture {};
 TEST_F(AnthropicStreamErrorTest, HandleStreamConnectionError) {
   ControllableAnthropicClient client(kTestAnthropicApiKey);
   StreamOptions options(
-      GenerateOptions("claude-3-5-sonnet-20241022", "Test prompt"));
+      GenerateOptions("claude-sonnet-4-5-20250929", "Test prompt"));
 
   client.setShouldFail(true);
 
@@ -204,7 +204,7 @@ TEST_F(AnthropicStreamErrorTest, HandleStreamConnectionError) {
 TEST_F(AnthropicStreamErrorTest, HandleStreamTimeout) {
   ControllableAnthropicClient client(kTestAnthropicApiKey);
   StreamOptions options(
-      GenerateOptions("claude-3-5-sonnet-20241022", "Test prompt"));
+      GenerateOptions("claude-sonnet-4-5-20250929", "Test prompt"));
 
   client.setShouldTimeout(true);
 
@@ -285,13 +285,13 @@ TEST_F(AnthropicStreamIntegrationTest, StreamWithClientConfiguration) {
   EXPECT_TRUE(client.is_valid());
 
   StreamOptions options(
-      GenerateOptions("claude-3-5-sonnet-20241022", "Stream test"));
+      GenerateOptions("claude-sonnet-4-5-20250929", "Stream test"));
   auto result = client.stream_text(options);
 
   EXPECT_EQ(client.getCallCount(), 1);
 
   auto last_options = client.getLastStreamOptions();
-  EXPECT_EQ(last_options.model, "claude-3-5-sonnet-20241022");
+  EXPECT_EQ(last_options.model, "claude-sonnet-4-5-20250929");
   EXPECT_EQ(last_options.prompt, "Stream test");
 }
 
@@ -347,12 +347,12 @@ TEST_F(AnthropicStreamEventTypesTest, MessageStartEvent) {
   std::string event_data =
       "data: "
       "{\"type\":\"message_start\",\"message\":{\"id\":\"msg_123\",\"type\":"
-      "\"message\",\"role\":\"assistant\",\"content\":[],\"model\":\"claude-3-"
-      "5-sonnet-20241022\",\"stop_reason\":null,\"stop_sequence\":null,"
+      "\"message\",\"role\":\"assistant\",\"content\":[],\"model\":\"claude-"
+      "sonnet-4-5-20250929\",\"stop_reason\":null,\"stop_sequence\":null,"
       "\"usage\":{\"input_tokens\":25,\"output_tokens\":1}}}\n\n";
 
   EXPECT_THAT(event_data, testing::HasSubstr("message_start"));
-  EXPECT_THAT(event_data, testing::HasSubstr("claude-3-5-sonnet-20241022"));
+  EXPECT_THAT(event_data, testing::HasSubstr("claude-sonnet-4-5-20250929"));
   EXPECT_THAT(event_data, testing::HasSubstr("input_tokens"));
 }
 
diff --git a/tests/utils/mock_anthropic_client.cpp b/tests/utils/mock_anthropic_client.cpp
index 170ced2..fd53888 100644
--- a/tests/utils/mock_anthropic_client.cpp
+++ b/tests/utils/mock_anthropic_client.cpp
@@ -132,8 +132,8 @@ std::string ControllableAnthropicClient::provider_name() const {
 }
 
 std::vector<std::string> ControllableAnthropicClient::supported_models() const {
-  return {"claude-3-5-sonnet-20241022", "claude-3-haiku-20240307",
-          "claude-3-opus-20240229", "claude-3-sonnet-20240229"};
+  return {"claude-sonnet-4-5-20250929", "claude-haiku-4-5-20251001",
+          "claude-opus-4-1-20250805", "claude-sonnet-4-20250514"};
 }
 
 bool ControllableAnthropicClient::supports_model(
diff --git a/tests/utils/mock_anthropic_client.h b/tests/utils/mock_anthropic_client.h
index 6ae79c8..7f05cfe 100644
--- a/tests/utils/mock_anthropic_client.h
+++ b/tests/utils/mock_anthropic_client.h
@@ -94,7 +94,7 @@ class AnthropicResponseBuilder {
  public:
   static std::string buildSuccessResponse(
       const std::string& content = "Test response",
-      const std::string& model = "claude-3-5-sonnet-20241022",
+      const std::string& model = "claude-sonnet-4-5-20250929",
       int input_tokens = 10,
       int output_tokens = 20);
 
diff --git a/tests/utils/test_fixtures.cpp b/tests/utils/test_fixtures.cpp
index d45814e..9a861f7 100644
--- a/tests/utils/test_fixtures.cpp
+++ b/tests/utils/test_fixtures.cpp
@@ -271,7 +271,7 @@ std::vector<std::string> TestDataGenerator::createAnthropicStreamingEvents() {
       "data: "
       "{\"type\":\"message_start\",\"message\":{\"id\":\"msg_stream1\","
       "\"type\":\"message\",\"role\":\"assistant\",\"content\":[],\"model\":"
-      "\"claude-3-5-sonnet-20241022\",\"stop_reason\":null,\"stop_sequence\":"
+      "\"claude-sonnet-4-5-20250929\",\"stop_reason\":null,\"stop_sequence\":"
       "null,\"usage\":{\"input_tokens\":25,\"output_tokens\":1}}}\n\n",
       "data: "
       "{\"type\":\"content_block_start\",\"index\":0,\"content_block\":{"
diff --git a/tests/utils/test_fixtures.h b/tests/utils/test_fixtures.h
index 4c3ae7f..76fe4e9 100644
--- a/tests/utils/test_fixtures.h
+++ b/tests/utils/test_fixtures.h
@@ -26,7 +26,7 @@ class AITestFixture : public ::testing::Test {
   // Anthropic test data
   static constexpr const char* kTestAnthropicApiKey = "sk-ant-test123456789";
   static constexpr const char* kTestAnthropicModel =
-      "claude-3-5-sonnet-20241022";
+      "claude-sonnet-4-5-20250929";
   static constexpr const char* kTestAnthropicBaseUrl =
       "https://api.anthropic.com";
 };