Member of Technical Staff
Member of Technical Staff is a title, not a rank on an org chart. It comes from the industrial research lab tradition. Bell Labs used it. Xerox PARC used it. Engineering-heavy companies still do, especially the ones that want technical people to stay technical.
The work is individual contributor work. You are hired as a technical peer and trusted with hard, ambiguous problems. You are expected to exercise judgment without waiting for a manager title to authorize it. You can do this for an entire career. The title stays flat on purpose. It does not advertise seniority the way Staff Engineer or Vice President does.
I am a Member of Technical Staff at Argentum AI, working on the future of large-scale compute, with an eye to the stars.