Inside a Series/Author library folder, the back arrow was a no-op after a
cold start. `GroupHeader.handleBack` deleted the `group` query param, leaving
an empty search string; `router.replace('/library')` with an empty search
silently no-ops under the Next.js 16.2 static export (every non-web build).
This is the same root cause as #3782, which was fixed for the breadcrumb
"All" button in #3832 — but the series/author back button never got the
workaround.
It only reproduces after a cold start, when `groupBy` comes from settings
(not the URL) and sort/order/view are at defaults, so `group` is the only
query param; that is why it could not be reproduced within a session.
Fix: set `group=''` instead of deleting it (mirroring
`handleLibraryNavigation`). The resulting `/library?group=` commits, and the
existing cleanup effect in page.tsx strips the trailing empty `group=`.
Verified on-device (Android, WebView 148, static export): tapping back inside
an author folder now returns to the main list.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Huang Xin
b31699d052