fix(amazon-bedrock): return request body from doGenerate and doStream

Add `request: { body: args }` to the return objects of both
`doGenerate()` and `doStream()` in BedrockChatLanguageModel, matching
the pattern used by `@ai-sdk/anthropic` and other providers.

Previously the Bedrock provider omitted the request field (with a
`// TODO request?` comment in doStream), causing observability
frameworks like Mastra to receive `undefined` when reading
`request.body` for tracing span inputs.

Fixes #13927

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: giulio-leone

.changeset/bedrock-request-body.md

@@ -0,0 +1,5 @@
+---
+'@ai-sdk/amazon-bedrock': patch
+---
+
+Return `request: { body }` from `doGenerate()` and `doStream()` in the Bedrock chat language model, matching the pattern used by other providers (e.g. `@ai-sdk/anthropic`). This enables observability frameworks to access the request body for tracing and debugging.

packages/amazon-bedrock/src/__snapshots__/bedrock-chat-language-model.test.ts.snap

@@ -35,6 +35,29 @@ There are 3 r's.",
       },
     },
   },
+  "request": {
+    "body": {
+      "additionalModelRequestFields": undefined,
+      "additionalModelResponseFieldPaths": [
+        "/delta/stop_sequence",
+      ],
+      "messages": [
+        {
+          "content": [
+            {
+              "text": "Hello",
+            },
+          ],
+          "role": "user",
+        },
+      ],
+      "system": [
+        {
+          "text": "System Prompt",
+        },
+      ],
+    },
+  },
   "response": {
     "headers": {
       "content-length": "865",
@@ -92,6 +115,29 @@ There are **3** "r"s in "strawberry."",
       },
     },
   },
+  "request": {
+    "body": {
+      "additionalModelRequestFields": undefined,
+      "additionalModelResponseFieldPaths": [
+        "/delta/stop_sequence",
+      ],
+      "messages": [
+        {
+          "content": [
+            {
+              "text": "Hello",
+            },
+          ],
+          "role": "user",
+        },
+      ],
+      "system": [
+        {
+          "text": "System Prompt",
+        },
+      ],
+    },
+  },
   "response": {
     "headers": {
       "content-length": "435",

packages/amazon-bedrock/src/bedrock-chat-language-model.test.ts

@@ -270,6 +270,19 @@ describe('doStream', () => {
         }
       `);
     });
+
+    it('should include request body', async () => {
+      const result = await model.doStream({
+        prompt: TEST_PROMPT,
+        includeRawChunks: false,
+      });
+
+      expect(result.request).toBeDefined();
+      expect(result.request?.body).toBeDefined();
+      expect(result.request?.body).toMatchObject({
+        messages: expect.any(Array),
+      });
+    });
   });
 
   describe('reasoning', () => {
@@ -3133,6 +3146,18 @@ describe('doGenerate', () => {
         }
       `);
     });
+
+    it('should include request body', async () => {
+      const { request } = await model.doGenerate({
+        prompt: TEST_PROMPT,
+      });
+
+      expect(request).toBeDefined();
+      expect(request?.body).toBeDefined();
+      expect(request?.body).toMatchObject({
+        messages: expect.any(Array),
+      });
+    });
   });
 
   describe('reasoning', () => {

packages/amazon-bedrock/src/bedrock-chat-language-model.ts

@@ -575,6 +575,7 @@ export class BedrockChatLanguageModel implements LanguageModelV4 {
         raw: response.stopReason ?? undefined,
       },
       usage: convertBedrockUsage(response.usage),
+      request: { body: args },
       response: {
         id: responseHeaders?.['x-amzn-requestid'] ?? undefined,
         timestamp:
@@ -979,7 +980,7 @@ export class BedrockChatLanguageModel implements LanguageModelV4 {
           },
         }),
       ),
-      // TODO request?
+      request: { body: args },
       response: { headers: responseHeaders },
     };
   }