Allow threads to run in the background

packages/react-headless/src/hooks/useIsThreadStreaming.ts

@@ -0,0 +1,16 @@
+import { useStore } from "zustand";
+import { useChatStore } from "../store/ChatContext";
+
+/**
+ * Whether `threadId` is currently streaming in the **background** — i.e. it has a
+ * run in flight while NOT being the active thread. Background streams are exactly
+ * the keys of {@link ChatStore.inFlightThreads} (the active thread lives in the
+ * flat store fields and is never here, and an entry is dropped the moment its run
+ * completes), so this is the direct signal for the sidebar loader.
+ *
+ * @category Hooks
+ */
+export function useIsThreadStreaming(threadId: string | null): boolean {
+  const store = useChatStore();
+  return useStore(store, (s) => threadId != null && threadId in s.inFlightThreads);
+}

packages/react-headless/src/hooks/useThread.ts

@@ -12,6 +12,7 @@ import type {
 type ThreadSlice = ThreadState & ThreadActions;
 type ThreadListSlice = ThreadListState & ThreadListActions;
 
+// The active thread lives directly in the store's flat fields.
 const threadSelector = (s: ChatStore): ThreadSlice => ({
   messages: s.messages,
   isRunning: s.isRunning,
@@ -32,6 +33,7 @@ const threadListSelector = (s: ChatStore): ThreadListSlice => ({
   threadListError: s.threadListError,
   selectedThreadId: s.selectedThreadId,
   hasMoreThreads: s.hasMoreThreads,
+  isCreatingThread: s.isCreatingThread,
   loadThreads: s.loadThreads,
   loadMoreThreads: s.loadMoreThreads,
   switchToNewThread: s.switchToNewThread,

packages/react-headless/src/index.ts

@@ -4,6 +4,7 @@ export type { ArtifactListFilter } from "./hooks/useArtifactList";
 export { useArtifactRenderer } from "./hooks/useArtifactRenderer";
 export { useDetailedView } from "./hooks/useDetailedView";
 export { useDetailedViewPortalTarget } from "./hooks/useDetailedViewPortalTarget";
+export { useIsThreadStreaming } from "./hooks/useIsThreadStreaming";
 export { MessageContext, MessageProvider, useMessage } from "./hooks/useMessage";
 export { useThread, useThreadList } from "./hooks/useThread";
 export { useToolActivities } from "./hooks/useToolActivities";
@@ -78,6 +79,7 @@ export type {
   ThreadListActions,
   ThreadListState,
   ThreadState,
+  ThreadStateEntry,
 } from "./store/types";
 
 export type {