[elmerfud]

If they are leaving for management positions because they believe it furthers their careers then there's likely not much you can do. They are resume building for the long term. You would need to be able to offer them something equivalent that they can put on their resume. With only a single small team, I'm not sure what that would be.

Unfortunately there is age bias and this prompts those who many not really want management positions to pursue them. when you think of the life of your career you may be an excellent software engineer in your 20s and 30s but as you move up and get older it becomes harder and harder tofind positions at companies into your 40s and 50s and 60s as simply a software engineer. Moving into a management role it is much easier to find positions at those ages.

Offering money or title is a short term carrot and those thinking long term won't fall for it. If people have outgrown what you can offer them in terms career advancement, it may be best to wish them well as they move on.