refactor(plugin-chatbot): drop the inert blanket cast on useChat's options object

.changeset/issue-8378-usechat-options-cast.md

@@ -0,0 +1,11 @@
+---
+---
+
+Removes the inert blanket `as any` on `useChat`'s options object in
+`useObjectChat` (objectui#8378). Publishes nothing: the assertion lives inside a
+function body whose export already carries an explicit return-type annotation, so
+it is erased at emit. Measured rather than assumed — building
+`@object-ui/plugin-chatbot` from this branch and from the merge-base produced a
+byte-identical `dist` across all 34 published artifacts (`.d.ts`, `.js`, `.cjs`,
+`.css`), and the comparison was proved live by a control mutation to an emitted
+string literal, which the same comparison reported as differing.

packages/plugin-chatbot/src/useObjectChat.ts

@@ -701,6 +701,14 @@ export function useObjectChat(options: UseObjectChatOptions = {}): UseObjectChat
   const chatRef = useRef<any>(null);
   const chatResult = useChat({
     transport,
+    // The `as any` here is the LIVE suppression on this call, and it is the only
+    // one: `aiInitialMessages` builds `parts` as `Record<string, unknown>[]`, which
+    // is not a `UIMessagePart` union, so dropping this cast turns the call red with
+    // TS2322 (measured, objectui#8378). The blanket `as any` that used to sit on the
+    // whole options object was removed there because it hid nothing this one does not
+    // already absorb — but it also switched off checking of `transport`, `onError`
+    // and excess properties. Fix the builder before deleting this cast; do NOT
+    // re-widen the call by casting the options object again.
     messages: isApiMode && aiInitialMessages.length > 0 ? (aiInitialMessages as any) : undefined,
     onError: isApiMode
       ? (err: Error) => {
@@ -732,7 +740,7 @@ export function useObjectChat(options: UseObjectChatOptions = {}): UseObjectChat
           onError?.(err);
         }
       : undefined,
-  } as any);
+  });
   chatRef.current = chatResult;
 
   // ADR-0057 #8 — refresh the AI usage indicator when a turn finishes. On the