I rarely talk about it - its the power user of power users features.
I didn't want to clobber the existing file search in Claude Code, so I put it behind // instead of @ inside the CLI -- its hidden.
But it's one of my most used features and one of the reasons I can't imagine not using Subspace.
You can type // from anywhere (agents, comments, terminal) to autocomplete files, slash commands, skills, mcps, shell commands, mention workspaces, etc.