Bendy bones keep constant length

Beny bones are quite handy when moving cord-like legs. But you can by bending and stretching make the legs longer. I want to keep the length of the legs of my character constant at all time.

Is there a way to keep the length constant?
So it kan be stretched for bending and moving but no added length?

Blendfile: https://gofile.io/d/y1yT14

The first leg (left) is my standard. the second is stretched.

the handle bones of the bendy bone are not usually used for keying animation . Those are usually a sub-rig to modify the deformations but the animation chain should remain a simple two bones chain.
Then you constraint your handle bones to the Fk chain.

thank you bourdul for the quick reply. I see what you mean, a sub-rig.

So if I understand correctly the 2 armature main rig can be coupled to the bendy-bone rig.

Can you tell me what bone constraint to use ?
I am guessing the bendy bone rig is the one with the bone constraint applied to it.

copy transform in world space, use head/tail at 1 for the last anchor

Thanks, I will try this