Live network trace via playwright showed every channel mount firing TWO
parallel GET /channels/:id/messages requests (AppLayout + MessageList
both call loadMessages on mount; neither can be removed because
MessageList is also rendered by VoiceChatPanel which doesn't call it),
and every fast-scroll burst firing N parallel loadMoreMessages calls
(handleScroll closure shares !isLoadingMore=true across the burst).
The hasMore-based guard only deduplicates calls AFTER the first
completes — it does not collapse parallel callers. On a NAT hairpin'd
LAN where some federated TCP connections hang, having N hung parallel
fetches keeps the pagination skeleton stuck while any one is still
waiting on the 30 s api-client timeout.
Fix: in-flight Promise dedup at the chatStore level. Module-level Maps
keyed on channelId; concurrent callers receive the same Promise.
Cleared in finally with self-check so a force-reload mid-flight isn't
dropped. force=true bypasses dedup (WS reconnect intent).
Jannis Braun
a189cbfba3