Sit with your butt on the edge of your chair (don't use the back rest at all) ... Your back will be naturally straight and your core muscles will gain endurance. I learned this by using an exercise ball as a chair for six months.
That's nonsense, I'm perfectly capable of slouching without the assistance of a back rest.
Op must have an iron rod for a spine. I naturally slouch lying down. Cats are less fluid than my posture at 4pm-second-wind, two-screens-of-code-and-one-of-data full-crunch-engaged mode.
Get a standing desk and put on something with a beat. Same style, but it's better for your spine and you don't need fidget toys for when you're pegging your CPU.
the only solution appear to be a reverse standing desk. you get one of those reclinable planks to hang yourself upside down at an incline and have gravity fix your posture
Ok, we found a graduate of Tom Cruise's programming school (Mission Impossible) .
As a musician coder, I always sit that way in chairs.