Bit of a supply puzzle

[PoorOldSpike]

The AI Gebirgsjager unit in the hills map-edge hex at the bottom is 'encircled' and out of supply.
I thought edge hexes provided supply, or have I overlooked something?

[scott_mathieson]

Hex either side is blocking it I presume as mountains and dense forest block supply.

[dalfrede]

The terrain of the edge of map hex counts.

In the AO39 Betas there was a major river unseen at the edge in the Orenthal scenario near one of the bonus captures. It made surrounding the French much easier. The map was revised to make it more clear.

They may be happening here, but you would have to open the map in the editor to be sure.

[PoorOldSpike]

Hex either side is blocking it I presume as mountains and dense forest block supply.

The terrain of the edge of map hex counts.
In the AO39 Betas there was a major river unseen at the edge in the Orenthal scenario near one of the bonus captures. It made surrounding the French much easier. The map was revised to make it more clear.
They may be happening here, but you would have to open the map in the editor to be sure.

Scott- The unit is sitting in a 'Hills' hex which shouldn't block supply, but perhaps the adjacent impassable thick forest and high mountain hexes affect it as you suggest.

Dalfrede- It was a 'small' map created by the random generator, so yes I agree that perhaps there's impassable terrain offmap just to the south which was cropped off by the generator.
A clue are the few trees in the partial hex at the tip of the yellow arrow, which might mean there's a thick forest in the rest of the hex.
I've photoshopped a guess at where all the invisible offmap thick forest hexes are, which would mean there's no way supply could be traced off the southern edge at that point-