diff --git a/.changeset/four-cars-deliver.md b/.changeset/four-cars-deliver.md
new file mode 100644
index 000000000..bdef212d2
--- /dev/null
+++ b/.changeset/four-cars-deliver.md
@@ -0,0 +1,5 @@
+---
+"@assistant-ui/react": patch
+---
+
+fix: make AppendMessage attachments field optional for now
diff --git a/packages/react-ai-sdk/src/ui/utils/toCreateMessage.ts b/packages/react-ai-sdk/src/ui/utils/toCreateMessage.ts
index e9be5efbc..1f5714657 100644
--- a/packages/react-ai-sdk/src/ui/utils/toCreateMessage.ts
+++ b/packages/react-ai-sdk/src/ui/utils/toCreateMessage.ts
@@ -19,7 +19,7 @@ export const toCreateMessage = async (
     experimental_attachments: [
       ...images,
       ...(await Promise.all(
-        message.attachments.map(async (m) => {
+        (message.attachments ?? []).map(async (m) => {
           if (m.file == null)
             throw new Error("Attachment did not contain a file");
           return {
diff --git a/packages/react/src/types/AssistantTypes.ts b/packages/react/src/types/AssistantTypes.ts
index 3167181f0..7b51adc93 100644
--- a/packages/react/src/types/AssistantTypes.ts
+++ b/packages/react/src/types/AssistantTypes.ts
@@ -133,7 +133,8 @@ export type ThreadAssistantMessage = MessageCommonProps & {
 
 export type AppendMessage = CoreMessage & {
   parentId: string | null;
-  attachments: readonly MessageAttachment[];
+  // TODO make required in the next major version
+  attachments?: readonly MessageAttachment[];
 };
 
 export type ThreadMessage =