Part 4: Upgrades

Capella

The consensus layer's Capella upgrade took place at 22:27:35 UTC on April the 12th, 2023, at the same time as the execution layer's Shanghai upgrade. This was the first coordinated, simultaneous upgrade of the two layers. The combined upgrade was known by the name "Shapella".

Capella included the following updates:

• it enabled automatic withdrawals from the beacon chain to Eth1 accounts;
• it provided a way for stakers to make a one-time change from BLS-style withdrawal credentials to Eth1-style withdrawal credentials;
• the way historical roots are stored in the beacon state was modified; and,
• there was a big refactor of the fork choice rule specification, along with some behavioural changes.

By finally enabling withdrawals, Capella in some sense completed The Merge, fulfilling the promise to stakers made 2.5 years earlier that they would eventually be able to claim their rewards and reclaim their stakes.

Two withdrawal mechanisms were implemented.

1. Exited and withdrawable validators have their full balances automatically transferred to their withdrawal addresses.
2. Excess balances from active validators are regularly swept into their withdrawal addresses.

The overall description of the changes between Bellatrix and Capella is in the Capella specs.

My Capella annotated specification remains available.