Do you care to share then? Because anyone I know with any sense right now is aware that "planning for the next forty or so years" is genuinely impossible at this point, especially in mathematics, and the right approach is to remain on your toes, ride the waves, and diversify as much as possible. Heck, even planning for the next five years seems absurd. This is a time of immense uncertainty, and to think otherwise is foolish.

A few years ago I was in a pure math degree, but I switched and graduated with a combined degree in math and computer science. Once I finish my masters degree I intend to work on industry applications of formal methods, which I anticipate will be a high-growth area for the next few years. The idea is to take advantage of the growing ability to generate proofs/code and work on keeping the messy human side of the equation up to speed. So I plan on addressing the social and operational aspects which come with delegating more work to AI. I'll work on integrating these gains into the industry, on building trust in the work that AI produces, and I'll work on the interface that lets us ensure that this trust is deserved.

But nothing is certain. I am trying to avoid overspecialization and remain flexible, just as you advise. If this path fails I might become a paramedic or physiotherapist.