CS-BOLD-013 Informational 7.1: Backed Tokens Can Be Redeemed Unproportionally

[bingen]

In CollateralRegistry, the redeemCollateral function has a special case for when all active branches are fully "backed". In this case the function will redeem from all active branches proportionally to the branch debt.

However, an edge case that is not explicitly handled is when there is a branch with more than zero unbacked debt, but less than the requested _boldAmount (and the other branches are fully backed). In this case, the function will redeem only from this branch, even though the branch will also become fully backed during the redemption process. This means that "fully backed" branches can be redeemed unproportionally.

It is not clearly specified if this is expected behavior or not.

[bingen]

there is a branch with more than zero unbacked debt, but less than the requested _boldAmount (and the other branches are fully backed)

If all the branches are fully backed except one, then the max amount that can be redeemed is the unbacked portion of that one branch, otherwise the sum of all SPs would exceed the total supply. So it seems to me that this scenario is impossible.