CCIP-019: PoX 4 update

ccips/ccip-019/ccip-019-pox-4-stacking.md

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+# CCIP-019
+
+## Preamble
+
+| CCIP Number   | 019                                    |
+| ------------- | -------------------------------------- |
+| Title         | PoX 4 Stacking                         |
+| Author(s)     | Jason Schrader [email protected]  |
+|               | Tim Butterfield [email protected] |
+|               | Friedger Müffke [email protected]       |
+| Consideration | Governance, Economic, Technical        |
+| Type          | Standard                               |
+| Status        | Draft                                  |
+| Created       | 2024-01-04                             |
+| License       | BSD-2-Clause                           |
+| Supplements   | CCIP-006, CCIP-012, CCIP-013, CCIP-014 |
+
+## Introduction
+
+With the Stacks Nakomoto release[^1], a new version of the PoX contract `.pox-4` was released. The previous versions of the PoX contracts are used by the treasury contracts to perform delegated stacking (STX).
+
+The CCIP-020 has disabled stacking and mining City coin tokens. However, the future of the treasury has not been finalized. There is a strong opinion in the community to liquidate the treasury. The details will be described in CCIP-022.
+
+CCIP-022 can define to stop deelgated stacking. The treasury can be unlocked after each cycle.
+
+Based on the uncertainty of the details in CCIP-022, this CCIP intends to:
+
+- update .pox-3 to .pox-4 for delegated stacking in city treasury contracts in continuation of the current delegated stacking process.
+
+## Specification
+
+### Treasury Contracts
+
+The current treasury contracts used with mining directly call the `.pox-3` contract, which was replaced with `.pox-4` in the Stacks 2.5 release[^1].
+
+CCIP-019 will implement a new version of the treasury contract `ccd002-treasury-v3` that replaces `.pox-3` with `.pox-4`, as well as move the balances and perform the delegated stacking.
+
+The pool operator send stacking rewards to a new reward-treasury contract. The community will vote on how to spend the stacking rewards in the future.
+
+> Note: this only affects the mining treasuries for each city, the addresses for the stacking treasuries will remain the same
+
+| City | Current                   | New                       |
+| ---- | ------------------------- | ------------------------- |
+| MIA  | ccd002-treasury-mining-v2 | ccd002-treasury-mining-v3 |
+| MIA  | ccd002-treasury-stacking  | _(no change)_             |
+| NYC  | ccd002-treasury-mining-v2 | ccd002-treasury-mining-v3 |
+| NYC  | ccd002-treasury-stacking  | _(no change)_             |
+
+### Proposal Voting
+
+This proposal is a continuation of the current delegated stacking process and does not require a vote.
+
+## Backwards Compatibility
+
+This CCIP only changes the treasury contract. All traits etc. are unchanged. The treasury continues to receive rewards.
+
+## Activation
+
+The CCIP would be activate via direct execution defined in CCIP-001.
+
+## Reference Implementations
+
+The reference implementation is published in the protocol repo[^2].
+
+## Footnotes
+
+[^1]: https://stacks.org/halving-on-horizon-nakamoto
+[^2]: https://github.com/citycoins/protocol/pull/67