First, your data is safe. The Agents Window builds its sidebar from a session index in your workspace storage, not directly from the transcript files, and that index can fall out of sync (usually after an update), so the linked agents drop off even though the worktrees themselves are untouched. This is a known issue we’re tracking.
For the agents stuck on “New Agent loading,” try Cmd+Shift+P → Developer: Reload Window. If any are still stuck, fully quit with Cmd+Q and reopen - that clears the stuck state in most cases.
Your past worktree sessions are still on disk under ~/.cursor/projects/<project>/agent-transcripts/, so nothing’s lost. There isn’t a built-in way to rebuild the sidebar from those files yet, so older worktree agents may stay missing from the panel even after a reload.
Did this start right after a Cursor update? That’ll help us narrow down which variant you’re hitting.