The group room's composer (new-thread box and reply-in-thread box) rendered
a plain SDK Input. The plugin's mention provider is registered against
COMPOSER_AREAS.atCompletions, which only mounts in the main chat composer —
workspace tiles never see it, so typing @ or / in a group chat did nothing
despite the placeholder advertising "@name to direct, @everyone for all".
Fix: a member-scoped GroupMentionInput wrapper in the plugin itself —
caret-aware @-token detection, popover offering @everyone/@all plus each
seated member's handle (same botHandle the parser uses), keyboard nav
(Up/Down/Enter/Tab/Escape), and insertion that produces exactly the
"@handle " strings parseGroupChatMentions resolves. Both group composers
(GroupChatWorkspace main box + thread reply box) mount it; the per-bot
composer path is untouched.
Root cause traced by the reporter of #89049 — confirmed against source.
Teknium
daca386967