diff --git a/.stats.yml b/.stats.yml
index 660e6d2d..68c3aa80 100644
--- a/.stats.yml
+++ b/.stats.yml
@@ -1,2 +1,2 @@
 configured_endpoints: 2
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/anthropic-4f6df1026ffeed840bbfada906ac51144508d1e1b099084c593aa9bac97a3362.yml
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/anthropic-70873642f89316fbc45ceaccd3583971d0eb59d433f7864ca2fa8c321a320b4c.yml
diff --git a/src/resources/messages.ts b/src/resources/messages.ts
index b4fabb66..03497af4 100644
--- a/src/resources/messages.ts
+++ b/src/resources/messages.ts
@@ -479,6 +479,7 @@ export interface MessageCreateParamsBase {
    */
   model:
     | (string & {})
+    | 'claude-3-5-sonnet-20240620'
     | 'claude-3-opus-20240229'
     | 'claude-3-sonnet-20240229'
     | 'claude-3-haiku-20240307'
@@ -519,7 +520,7 @@ export interface MessageCreateParamsBase {
    * as specifying a particular goal or role. See our
    * [guide to system prompts](https://docs.anthropic.com/en/docs/system-prompts).
    */
-  system?: string;
+  system?: string | Array<TextBlockParam>;
 
   /**
    * Amount of randomness injected into the response.
diff --git a/tests/api-resources/messages.test.ts b/tests/api-resources/messages.test.ts
index e1c23c77..7f71c7b7 100644
--- a/tests/api-resources/messages.test.ts
+++ b/tests/api-resources/messages.test.ts
@@ -13,7 +13,7 @@ describe('resource messages', () => {
     const responsePromise = anthropic.messages.create({
       max_tokens: 1024,
       messages: [{ role: 'user', content: 'Hello, world' }],
-      model: 'claude-3-opus-20240229',
+      model: 'claude-3-5-sonnet-20240620',
     });
     const rawResponse = await responsePromise.asResponse();
     expect(rawResponse).toBeInstanceOf(Response);
@@ -28,11 +28,11 @@ describe('resource messages', () => {
     const response = await anthropic.messages.create({
       max_tokens: 1024,
       messages: [{ role: 'user', content: 'Hello, world' }],
-      model: 'claude-3-opus-20240229',
+      model: 'claude-3-5-sonnet-20240620',
       metadata: { user_id: '13803d75-b4b5-4c3e-b2a2-6f21399b021b' },
       stop_sequences: ['string', 'string', 'string'],
       stream: false,
-      system: "Today's date is 2024-01-01.",
+      system: [{ type: 'text', text: "Today's date is 2024-06-01." }],
       temperature: 1,
       tool_choice: { type: 'auto' },
       tools: [