The Cosmos-SDK follows both 0ver and Semver. While this is confusing let's break it down: 0ver is used for the main Cosmos-SDK dependency (github.com/cosmos/cosmos-sdk) and Semver is used for all other dependencies.
Although we adhere to semantic versioning (semver), we have introduced a few modifications to accommodate the unique characteristics of blockchains. One significant divergence is that the major version (Y.x.x) is incremented solely when a consensus-breaking change occurs. On the other hand, the minor version (x.Y.x) is increased when there is a non-consensus-breaking alteration that also results in an incompatible API change. Patch versions will be bumped for all other changes that don't break the API nor Consensus.
flowchart TD
A[Change] --> B{Consensus Breaking?}
B -->|Yes| C[Increase Major Version]
B -->|No| D{API Breaking?}
D -->|Yes| E[Increase Minor Version]
D -->|No| F[Increase Patch Version]
In terms of the Cosmos-SDK dependency, we adhere to a simpler versioning approach known as 0ver. This flow differs from the previous Semver flow. Under this system, when a consensus-breaking change or an API-breaking change occurs, the Cosmos-SDK team increments the minor version (x.Y.x). Conversely, when a non-consensus-breaking change and a non-API-breaking change take place, the team bumps the patch version (x.x.Y).
flowchart TD
A[Change] --> B{Consensus Breaking?}
B -->|Yes| C[Increase Minor Version]
B -->|No| D{API Breaking?}
D -->|Yes| E[Increase Minor Version]
D -->|No| F[Increase Patch Version]