xDai bridge: migration from Sai to Dai

Bridge Migration Re-Scheduled | New date TBD

:exclamation: The original migration date scheduled for Dec 18, 2019 has been delayed. We are conducting additional security testing to ensure post-audit changes are functioning as required. We will announce a new date soon, and anticipate the transition to occur by End of Year.

On November 15, 2019, MakerDAO launched Multi-Collateral Dai (MCD), and provided the recommendation that all projects using Sai (the new name for the previous Single-Collateral Dai token) migrate from Sai/SCD to Dai/MCD.

Since the launch, we have engaged in in-depth discussion, completed several weeks of development (#319, #244 and #245) and addressed issues from a comprehensive security audit by Quantstamp.

As a result, the xDai bridge, which allows users to swap Dai ERC20 tokens to xDai native tokens in the xDai chain, will migrate to the Multi-Collateral Dai token on TBD.

This migration will occur immediately after the bridge contracts are upgraded to the new implementation and new TokenBridge oracles are deployed on the bridge validator’s nodes.

What to Expect Following Migration

Following migration, xDai bridge users will be able to deposit both Sai/SCD and Dai/MCD tokens to the bridge. Users will transfer Sai/SCD or Dai/MCD to the bridge contract in the Ethereum Mainnet and the corresponding number of xDai native tokens will be minted on the xDai chain.

All Sai/SCD tokens transferred to the bridge contract will be automatically swapped to Dai/MCD tokens - the bridge contract balance will be maintained in Dai/MCD. When tokens are withdrawn from the xDai chain (converted from xDai to Dai), the corresponding amount of Dai/MCD will be unlocked on the Ethereum mainnet.

In addition, the TokenBridge UI will be modified to operate only with Dai/MCD tokens . This means that transferring Sai/SCD tokens to the bridge contract will be possible only by directly calling the transfer method in the token contract.

Sai/SCD token deposits will be available until the Sai Emergency Shutdown occurs. There is no exact plan from MakerDAO when the token shutdown will happen but the new bridge contract will automatically detect it without any human intervention.

Contract and Token Addresses

Bridge contract addresses will remain the same after migration:

Token addresses:

Other xDai bridge parameters will not change.


Is this on a test net somewhere?


There is no official xDai testnet (where coins are being minted as part of the bridge deposit operations). In order to verify new bridge functionality we performed the design tests for new contracts and oracle as part of the work on the PR #319.

If you want to test your solution to work with the upgraded bridge we can assist you to help deploy the test net and the bridge environment.

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thanks for the update on the delay!

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