fix(js): stabilize HTML islands when streaming content type switches

js/src/chat/state.ts

@@ -118,11 +118,11 @@ export function chatReducer(state: ChatState, action: AnyAction): ChatState {
           ? last.content + action.content
           : action.content
 
-      // Update contentType if the chunk provides one (e.g., transition
-      // from "markdown" to "html" when UI elements appear mid-stream)
-      const contentType = action.content_type ?? last.contentType
-
-      return { ...state, streamingMessage: { ...last, content, contentType } }
+      // Do not update contentType mid-stream: switching processors between
+      // chunks causes HAST structural changes that unmount/remount HTML islands
+      // (e.g. <shinychat-raw-html>). The markdownProcessor already handles raw
+      // HTML via rehypeRaw, so the chunk_start contentType is sufficient.
+      return { ...state, streamingMessage: { ...last, content } }
     }
 
     case "chunk_end": {

js/src/markdown/MarkdownContent.tsx

@@ -15,9 +15,10 @@ import { RawHTML } from "../chat/RawHTML"
 const baseAssistantComponents: Record<string, ComponentType<unknown>> = {
   pre: CopyableCodeBlock as ComponentType<unknown>,
   table: BootstrapTable as ComponentType<unknown>,
-  "shinychat-raw-html": (({ node }: { node?: Element }) => (
-    <RawHTML html={node ? toHtml(node.children) : ""} displayContents />
-  )) as ComponentType<unknown>,
+  "shinychat-raw-html": (({ node }: { node?: Element }) => {
+    const html = node ? toHtml(node.children) : ""
+    return <RawHTML html={html} displayContents />
+  }) as ComponentType<unknown>,
 }
 
 const baseUserComponents: Record<string, ComponentType<unknown>> = {
@@ -48,6 +49,7 @@ export function MarkdownContent({
     : isUser
       ? userMarkdownProcessor
       : markdownProcessor
+
   const resolvedTagToComponentMap = useMemo(
     () =>
       isUser

js/src/markdown/processors.ts

@@ -25,13 +25,13 @@ export const markdownProcessor = unified()
   .use(remarkParse)
   .use(remarkGfm)
   .use(remarkRehype, { allowDangerousHtml: true })
+  .use(rehypeHighlight, { detect: false, ignoreMissing: true })
   .use(rehypeRaw)
   .use(rehypeLazyContinuation)
   .use(rehypeUnwrapBlockCEs)
   .use(rehypeUncontrolledInputs)
   .use(rehypeAccessibleSuggestions)
   .use(rehypeExternalLinks)
-  .use(rehypeHighlight, { detect: false, ignoreMissing: true })
   .freeze()
 
 /**

js/tests/chat/state.test.ts

@@ -191,7 +191,7 @@ describe("chatReducer", () => {
       expect(next.messages).toBe(state.messages)
     })
 
-    it("updates contentType when chunk provides one", () => {
+    it("ignores contentType provided by a chunk (locked to chunk_start)", () => {
       const msg = makeAssistantMsg({
         streaming: true,
         contentType: "markdown",
@@ -203,7 +203,7 @@ describe("chatReducer", () => {
         operation: "append",
         content_type: "html",
       })
-      expect(next.streamingMessage!.contentType).toBe("html")
+      expect(next.streamingMessage!.contentType).toBe("markdown")
     })
 
     it("keeps contentType when chunk does not provide one", () => {

pkg-py/src/shinychat/www/GIT_VERSION

@@ -1 +1 @@
-c21dd47a2b512aa40c4ac37455ea4e71db1eeedc
+bbbb76dcd6598cbfafdc830efb72c9bc4ba5b06d

pkg-r/inst/lib/shiny/GIT_VERSION

@@ -1 +1 @@
-c21dd47a2b512aa40c4ac37455ea4e71db1eeedc
+bbbb76dcd6598cbfafdc830efb72c9bc4ba5b06d