Announcing Hangzhou2

# Announcing Hangzhou2 As announced in our [previous blog post](https://marigold.dev/blog/communicating-about-view-issue-hangzhou/), a critical bug was found in the implemention of views introduced in protocol proposal `PtHangzHo`. Through the joint efforts of [Marigold](https://marigold.dev/), [Nomadic Labs](https://www.nomadic-labs.com/), and [Trilitech](https://trili.tech/), we have developed a patched protocol `PtHangz2a` that includes a fix to this bug, as well as several other bug fixes implemented after injection of `PtHangzHo`. ## Going Forward We are currently in the Promotion Period for `PtHangzHo`. If, at the end of this period on November 18th, `PtHangzHo` has a quorum and supermajority of approving votes, it will be adopted on Mainnet. Yesterday, Nomadic Labs has made available [a new release candidate for Octez: `11.0~rc2`](https://forum.tezosagora.org/t/release-candidate-version-11-0-rc2-of-octez/3855). This version includes a _user activated protocol override_: nodes running this software will automatically switch to `PtHangz2a` on Mainnet, if `PtHangzHo` is adopted. If `PtHangzHo` is accepted, all bakers and nodes running v11 of Octez will automatically switch to `PtHangz2a`. _In this event it is crucial for all bakers and nodes to upgrade to v11, or they will find themselves unable to participate in the consensus._ If `PtHangzHo` is rejected, we will inject either `PtHangz2a` or a successor in the next cycle. ## Changes in PtHangz2a ### Fix to Views The most critical fix was a correction of the semantics of views so that the step constants `BALANCE`, `AMOUNT`, `SENDER`, `SELF`, and `SELF_ADDRESS` are properly restored after returning from the view. This fix was introduced in [MR 3654](https://gitlab.com/tezos/tezos/-/merge_requests/3654). ### Fixes to RPC Endpoints A bug was discovered during the testing of Hangzhou in the `entrypoints` RPC endpoint related to the new global constants feature such that the endpoint failed for any contracts that used global constants. The bug was fixed in [MR 3731](https://gitlab.com/tezos/tezos/-/merge_requests/3731). Additionally, Hangzhou introduced two "fixed" constants `cache_layout` and `michelson_maximum_type_size` that were missing from the the `context/constants` RPC endpoint. This was fixed in [MR 3454](https://gitlab.com/tezos/tezos/-/merge_requests/3454). Lastly, the new cache feature introduced a new RPC `context/cache/contract_rank`. In [MR 3717](https://gitlab.com/tezos/tezos/-/merge_requests/3717), this path was changed to `context/cache/contracts/rank` for consistency with other RPC's. ### Gas Related Improvements Several gas improvements related to the features introduced in H were made in [MR 3441](https://gitlab.com/tezos/tezos/-/merge_requests/3441) and [MR 3724](https://gitlab.com/tezos/tezos/-/merge_requests/3724). ### Shell-related Improvements While not part of the protocol, the shell-related improvements in Octez `11.0~rc2` are critical for proper migration. Altogether they cut migration block baking time by a factor of 2 and greatly reduce memory consumption. Those interested in the technical details can see MR's [3679]( https://gitlab.com/tezos/tezos/-/merge_requests/3679), [3722](https://gitlab.com/tezos/tezos/-/merge_requests/3722), [3383](https://gitlab.com/tezos/tezos/-/merge_requests/3383 ), and [3735](https://gitlab.com/tezos/tezos/-/merge_requests/3735).