A more reliable method for filleting inside corners?

I am trying to write a definition that finds and isolates tangent circles that fit in inside corners. The purpose is for creating remachining toolpaths for CNC (using a smaller radius tool only for the tight spots, in order to speed up cutting).

The end goal is to create the magenta curves shown here (these were created manually):

There are conditions where fillet components fail, like this one:

The short straight line prevents a 0.125 radius fillet where it’s needed. So I tried another method, using offset curves, their discontinuities, and some sorting. It kinda works. Here’s the definition:
remach profiles.gh (101.0 KB)

As you can see, it will place tangent circles even when short curves would have disrupted a fillet command.

However… Offset curve (in green) is also unreliable. :frowning:

It also creates other issues, missing spots if the offset covers up a “bay” or “inlet” in a curve:

My Questions:

Broadly, does anyone have suggestions for how to do filleting like this more effectively? Am I using the right strategy or chasing a dead end?

Is there a method I can use to prevent offsets from failing like they do on the capital B?

Is there a method I can use to get offsets to produce more than one curve, so that the interior “bay” in a lowercase e or other situation produces a result along with the rest of the curve?

I think I’m 85-90% of the way there, but I’m stuck. Please help. Thanks!

These kinds of offsets are unfortunately unreliable in rhino. You could try using clipper, which will not have any problems with these offsets, however the output is polylines. since this is for CAM, I presume you want to maintain arcs? If your machine can handle lots of tiny linear moves then clipper might be an option. You can tweek the tolerance too