diff --git a/apps/app/src/react-app/shell/session-list-cache.ts b/apps/app/src/react-app/shell/session-list-cache.ts
new file mode 100644
index 000000000..0736f40af
--- /dev/null
+++ b/apps/app/src/react-app/shell/session-list-cache.ts
@@ -0,0 +1,64 @@
+import { useEffect } from "react";
+import { getReactQueryClient } from "../infra/query-client";
+
+const SESSION_LIST_KEY = ["workspace-session-list"] as const;
+
+export function sessionListQueryKey(workspaceId: string) {
+  return [...SESSION_LIST_KEY, workspaceId] as const;
+}
+
+export function sessionListQueryKeyPattern() {
+  return { queryKey: SESSION_LIST_KEY, exact: false };
+}
+
+export function cacheSessionList(workspaceId: string, sessions: unknown[]) {
+  getReactQueryClient().setQueryData(sessionListQueryKey(workspaceId), sessions);
+}
+
+export function invalidateSessionLists() {
+  getReactQueryClient().invalidateQueries(sessionListQueryKeyPattern());
+}
+
+export function isTabVisible(): boolean {
+  return typeof document === "undefined" || document.visibilityState === "visible";
+}
+
+/**
+ * Sets up a visibility-aware polling loop that invalidates workspace session
+ * lists at a fixed interval so that sessions created externally (by automations,
+ * messaging bots like Slack/Telegram, or other clients) appear in the sidebar
+ * without requiring manual refresh.  Only fires when the browser tab is visible
+ * to avoid unnecessary network requests while the user is working elsewhere.
+ *
+ * The `refetch` callback is responsible for performing the actual fetch and
+ * writing results into both the TanStack Query cache and the imperative state
+ * used by the sidebar.  The caller is responsible for providing its own
+ * in-flight guard so two ticks (or a tick that races with another refresh
+ * path) cannot overlap.
+ *
+ * Visibility restore is intentionally NOT handled here: callers in this
+ * codebase already wire up a `visibilitychange` listener that runs a heavier
+ * route-level refresh, and firing `refetch` from here as well caused two
+ * concurrent session-list refreshes on every tab focus.
+ *
+ * Fixes [#1262]{@link https://github.com/different-ai/openwork/issues/1262}
+ */
+export function useSessionListPolling(
+  refetch: () => void | Promise<void>,
+  intervalMs: number = 30_000,
+) {
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+
+    const tick = () => {
+      if (!isTabVisible()) return;
+      void refetch();
+    };
+
+    const id = window.setInterval(tick, intervalMs);
+
+    return () => {
+      window.clearInterval(id);
+    };
+  }, [refetch, intervalMs]);
+}