diff --git a/.changeset/fair-terms-jam.md b/.changeset/fair-terms-jam.md
new file mode 100644
index 000000000..2d10b4393
--- /dev/null
+++ b/.changeset/fair-terms-jam.md
@@ -0,0 +1,5 @@
+---
+"@assistant-ui/react": patch
+---
+
+fix: useContentPartText backwards compat type
diff --git a/packages/react/src/primitive-hooks/contentPart/useContentPartDisplay.tsx b/packages/react/src/primitive-hooks/contentPart/useContentPartDisplay.tsx
index c7cd8a69c..7ff2acd8f 100644
--- a/packages/react/src/primitive-hooks/contentPart/useContentPartDisplay.tsx
+++ b/packages/react/src/primitive-hooks/contentPart/useContentPartDisplay.tsx
@@ -9,7 +9,7 @@ export const useContentPartDisplay = () => {
         "This component can only be used inside ui content parts.",
       );
 
-    return c as ContentPartState & UIContentPart;
+    return c as ContentPartState & UIContentPart & { part: UIContentPart };
   });
 
   return display;
diff --git a/packages/react/src/primitive-hooks/contentPart/useContentPartImage.tsx b/packages/react/src/primitive-hooks/contentPart/useContentPartImage.tsx
index c6816539c..775382de7 100644
--- a/packages/react/src/primitive-hooks/contentPart/useContentPartImage.tsx
+++ b/packages/react/src/primitive-hooks/contentPart/useContentPartImage.tsx
@@ -9,7 +9,8 @@ export const useContentPartImage = () => {
         "ContentPartImage can only be used inside image content parts.",
       );
 
-    return c as ContentPartState & ImageContentPart;
+    return c as ContentPartState &
+      ImageContentPart & { part: ImageContentPart };
   });
 
   return image;
diff --git a/packages/react/src/primitive-hooks/contentPart/useContentPartText.tsx b/packages/react/src/primitive-hooks/contentPart/useContentPartText.tsx
index 16c2a07af..5631c5c24 100644
--- a/packages/react/src/primitive-hooks/contentPart/useContentPartText.tsx
+++ b/packages/react/src/primitive-hooks/contentPart/useContentPartText.tsx
@@ -9,7 +9,7 @@ export const useContentPartText = () => {
         "ContentPartText can only be used inside text content parts.",
       );
 
-    return c as ContentPartState & TextContentPart;
+    return c as ContentPartState & TextContentPart & { part: TextContentPart };
   });
 
   return text;
diff --git a/packages/react/src/types/AssistantTypes.ts b/packages/react/src/types/AssistantTypes.ts
index 21eca41f4..8046ac511 100644
--- a/packages/react/src/types/AssistantTypes.ts
+++ b/packages/react/src/types/AssistantTypes.ts
@@ -108,17 +108,12 @@ export type MessageStatus =
 export type ThreadSystemMessage = MessageCommonProps & {
   role: "system";
   content: [TextContentPart];
-  status?: undefined;
-  attachments?: undefined;
-  metadata?: undefined;
 };
 
 export type ThreadUserMessage = MessageCommonProps & {
   role: "user";
   content: ThreadUserContentPart[];
   attachments: readonly CompleteAttachment[];
-  status?: undefined;
-  metadata?: undefined;
   // TODO metadata
 };
 
@@ -126,7 +121,6 @@ export type ThreadAssistantMessage = MessageCommonProps & {
   role: "assistant";
   content: ThreadAssistantContentPart[];
   status: MessageStatus;
-  attachments?: undefined;
   /**
    * @deprecated Use `metadata.roundtrips` instead.
    */
@@ -143,10 +137,19 @@ export type AppendMessage = CoreMessage & {
   attachments?: readonly CompleteAttachment[] | undefined;
 };
 
-export type ThreadMessage =
-  | ThreadSystemMessage
-  | ThreadUserMessage
-  | ThreadAssistantMessage;
+type BaseThreadMessage = {
+  role: "user" | "system" | "assistant";
+  content:
+    | ThreadUserMessage["content"]
+    | ThreadSystemMessage["content"]
+    | ThreadAssistantMessage["content"];
+  status?: ThreadAssistantMessage["status"];
+  metadata?: ThreadAssistantMessage["metadata"];
+  attachments?: ThreadUserMessage["attachments"];
+};
+
+export type ThreadMessage = BaseThreadMessage &
+  (ThreadSystemMessage | ThreadUserMessage | ThreadAssistantMessage);
 
 /** Core Message Types (without UI content parts) */