Corner stone wall insulation board

[fredob]

Hello everyone, I'm new to the forum.
I am renovating an old farmhouse with stone walls (Pyrenees between Toulouse and Tarbes), I have walls of around 60 cm and my problem, or rather that of my father, is hunting for thermal bridges. I will leave an interior wall in visible stone which will be insulated by the exterior (north face) with wooden cladding. The rest of the interior walls will be isolated and the exteriors have been stitched and then joined.
So I would like to have advice to limit the thermal bridge that the wall angle will cause. Hoping to be clear. Thank you (drawing in addition)

[ATE.Conseil]

Hi,

Indeed, you end up with two thermal bridges difficult to treat ... and in addition, this kind of thermal bridges is likely to create condensation in the corners and therefore rot, mold ... etc
Not all that good! In your place, I would also isolate the entire wall above the one on the left in the drawing.
To break the thermal corner bridge, you must at least move away from 1m from the angle ... even if you do that, you might as well do it all.

Another possibility, since it is an old wall, you can also opt for an exterior insulation plaster based on warmth (Unilit 20 style) which - of course is not as effective as a traditional insulation , but will break the thermal bridge and keep an old appearance on the exterior walls

Greetings