feat (core): support converting attachments to file parts

.changeset/silly-pigs-judge.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+feat (core): support converting attachments to file parts

packages/ai/core/prompt/attachments-to-parts.ts

@@ -1,11 +1,11 @@
 import { Attachment } from '@ai-sdk/ui-utils';
-import { ImagePart, TextPart } from './content-part';
+import { FilePart, ImagePart, TextPart } from './content-part';
 import {
   convertDataContentToUint8Array,
   convertUint8ArrayToText,
 } from './data-content';
 
-type ContentPart = TextPart | ImagePart;
+type ContentPart = TextPart | ImagePart | FilePart;
 
 /**
  * Converts a list of attachments to a list of content parts
@@ -29,6 +29,18 @@ export function attachmentsToParts(attachments: Attachment[]): ContentPart[] {
       case 'https:': {
         if (attachment.contentType?.startsWith('image/')) {
           parts.push({ type: 'image', image: url });
+        } else {
+          if (!attachment.contentType) {
+            throw new Error(
+              'If the attachment is not an image, it must specify a content type',
+            );
+          }
+
+          parts.push({
+            type: 'file',
+            data: url,
+            mimeType: attachment.contentType,
+          });
         }
         break;
       }
@@ -61,6 +73,18 @@ export function attachmentsToParts(attachments: Attachment[]): ContentPart[] {
               convertDataContentToUint8Array(base64Content),
             ),
           });
+        } else {
+          if (!attachment.contentType) {
+            throw new Error(
+              'If the attachment is not an image or text, it must specify a content type',
+            );
+          }
+
+          parts.push({
+            type: 'file',
+            data: base64Content,
+            mimeType: attachment.contentType,
+          });
         }
 
         break;

packages/ai/core/prompt/convert-to-core-messages.test.ts

@@ -45,6 +45,35 @@ describe('user message', () => {
     ]);
   });
 
+  it('should handle user message with attachments (file)', () => {
+    const attachment: Attachment = {
+      contentType: 'application/pdf',
+      url: 'https://example.com/document.pdf',
+    };
+
+    const result = convertToCoreMessages([
+      {
+        role: 'user',
+        content: 'Check this document',
+        experimental_attachments: [attachment],
+      },
+    ]);
+
+    expect(result).toEqual([
+      {
+        role: 'user',
+        content: [
+          { type: 'text', text: 'Check this document' },
+          {
+            type: 'file',
+            data: new URL('https://example.com/document.pdf'),
+            mimeType: 'application/pdf',
+          },
+        ],
+      },
+    ]);
+  });
+
   it('should handle user message with attachment URLs', () => {
     const attachment: Attachment = {
       contentType: 'image/jpeg',
@@ -70,6 +99,35 @@ describe('user message', () => {
     ]);
   });
 
+  it('should handle user message with attachment URLs (file)', () => {
+    const attachment: Attachment = {
+      contentType: 'application/pdf',
+      url: 'data:application/pdf;base64,dGVzdA==',
+    };
+
+    const result = convertToCoreMessages([
+      {
+        role: 'user',
+        content: 'Check this document',
+        experimental_attachments: [attachment],
+      },
+    ]);
+
+    expect(result).toEqual([
+      {
+        role: 'user',
+        content: [
+          { type: 'text', text: 'Check this document' },
+          {
+            type: 'file',
+            data: 'dGVzdA==',
+            mimeType: 'application/pdf',
+          },
+        ],
+      },
+    ]);
+  });
+
   it('should throw an error for invalid attachment URLs', () => {
     const attachment: Attachment = {
       contentType: 'image/jpeg',
@@ -87,6 +145,24 @@ describe('user message', () => {
     }).toThrow('Invalid URL: invalid-url');
   });
 
+  it('should throw an error for file attachments without contentType', () => {
+    const attachment: Attachment = {
+      url: 'data:application/pdf;base64,dGVzdA==',
+    };
+
+    expect(() => {
+      convertToCoreMessages([
+        {
+          role: 'user',
+          content: 'Check this file',
+          experimental_attachments: [attachment],
+        },
+      ]);
+    }).toThrow(
+      'If the attachment is not an image or text, it must specify a content type',
+    );
+  });
+
   it('should throw an error for invalid data URL format', () => {
     const attachment: Attachment = {
       contentType: 'image/jpeg',