Add TwoWay Batcher


Previously in EIP-2, a new system called trusted borrowing was added to enable wrap / unwrap batcher contracts among other use cases.

The initial batcher contract WrapOnlyBatcher, as the name suggests, allowed for significantly cheaper USDC-to-DSU wrap transactions, however this batcher could not support DSU-to-USDC unwrap transactions, due to the requirement to hold non-reserve USDC.


We propose a new batcher implementation that supports the permissionless deposit / withdraw of USDC by interested parties to fund the batcher’s supply of USDC.

By holding non-reserve USDC as well as DSU from the reserve’s trusted borrow system, we can then enable bidirectional batching. This primarily serves to enable significantly cheaper DSU-to-USDC unwraps.


  • An implementation of the TwoWayBatcher can be seen here.
  • An implementation of the reserve update to enable the TwoWayBatcher can be seen here.

This batcher implementation has been created as part of perennial protocol upgrade work, and like the WrapOnlyBatcher is today, it will be utilized by the protocol in a future update if approved.

This is an interesting proposal.

While gas is relatively low and steady right now, having this infrastructure implemented during time of peak gas will benefit the users of protocols utilising DSU for operations.

One question: You mentioned ‘interested parties’ supplying USDC to the unwrapper, is there a specific incentive to deposit beyond smoother operation for protocols utilising DSU?

For this initial implementation, there is not a directly monetary incentive to supply the USDC liquidity.

We’re thinking that for now the protocols that want to utilize this batcher contract should be on the hook for providing the liquidity since their users are the ones benefitting.

In the near future, we think this would be a really great use for Empty Set’s excess reserves, however at current time the ~14k USDC that is currently available won’t move the needle a ton.