When You Leave, What Comes with You?

This one is a bit of a ramble but I have some loose questions bouncing around rn.

Who owns the Agentic capabilities you create for yourself in the course of working somewhere? When you learn something during your day job, it’s tacitly agreed upon that the knowledge in your meat machine is yours to keep. It’s not like the company has direct access to it anyway, they have to use You as an Interface to get access to it anyway. They own the code you create, but not the knowledge of how to re-create that code (outside of some strict trade-secret agreements I guess).

Can the same be said of personal Harness artifacts you create? Do they own the skills you create for yourself to use? The lawyers can figure that one out, and judging every employment agreement I have signed I would assume yes since it was created on company time and created with company resources (tokens + laptop).

So lets say that you air-gap your Harness customization and re-create the important bits into your non-work-truly-personal Harness. Do you then bring that to a new company directly? Is the expectation that all modern Software Engineers come with some level of tooling off the jump, If so, do they own that version?

If the Harness was really only meant to be useful to you, does it get thrown out when you leave? Do you have to re-create a new work harness from scratch when you start working at a new place? Even if a lot of it is already wired up for general use, surely you want to customize it to fit your tastes more closely.