The Fault Proofs upgrade is a change that many Superchain and OP Stack chains (OP Mainnet, Base, World Chain, Zora, etc) have either already gone through or will need to go through.
When a chain is upgraded to support fault proofs, the underlying proof submission mechanism changes, invalidating any currently inflight and proven but not finalized withdrawals.
After the upgrade is live, you will be able to prove and finalize withdrawals as normal. If a withdrawal was proven but not finalized before the upgrade, it will need to be reproven.
Superbridge does everything it can to prevent users initiating withdrawals that will be delayed or submitting prove operations that will be invalidated, but sometimes we only learn of chain upgrades a few days before they happen.
Upgrade 13: OPCM and incident response improvements
As part of changes to the fault proof mechanism, OP governance has approved a release of the fault proof system which will invalidate any in-flight or pending withdrawals.
As chains undergo this upgrade, the process will be very similar in nature to when a chain first upgrades to support fault proofs.
One benefit of this release is that future upgrades should not invalidate pending withdrawals, but for this release withdrawals will be invalidated. Timelines for the upgrade for each network can be found in the Optimism documentation.