Tezos upgrades itself by on-chain vote instead of hard forks

A blockchain that upgrades itself

Most blockchains upgrade by persuading node operators to install new software. When participants disagree, the result can be a chain split. @tezos takes a different approach: Tezos incorporates a built-in, on-chain mechanism for proposing, selecting, testing, and activating protocol upgrades without the need to hard fork.

On many other chains, decisions are often made by a small group and imposed on the ecosystem, and when participants disagree the result can be a hard fork that splits the chain into two or more competing versions. The self-amendment mechanism writes upgrade procedures into the blockchain itself, so the network can modify its own rules without requiring hard forks.

The process starts with a delegate submitting the hash of a proposal's source code on-chain. The self-amendment process is split into five automatically scheduled periods: a Proposal period, where delegates submit and upvote amendment proposals; an Exploration period, where users vote on the top proposal; and a Cooldown period before the final vote takes place. A Promotion period follows, and finally an Adoption period during which the network prepares to activate the change.

How votes are counted and what happens next

Only delegates can vote on proposals. A delegate's voting power equals the amount of $XTZ it has staked plus the $XTZ that delegators have delegated to it, also known as its staking balance. Delegates vote Yea, Nay, or Pass. The Pass option allows a delegate to contribute towards the quorum without contributing towards the supermajority.

Each of the five periods lasts 14 baking cycles, roughly 14 days, meaning the full process from proposal to activation takes almost two months. Should any period fail to meet the required threshold, the whole process reverts to the Proposal period, effectively restarting from the beginning.

If an amendment is approved by stakeholders via the governance mechanism, all nodes are automatically upgraded with no manual intervention needed. Once the Adoption period ends and the new protocol is live, a fresh Proposal period opens automatically.

Broader debate about what to build happens separately. This self-amendment process is distinct from the off-chain and less formal Tezos Improvement Process. That off-chain layer is where ideas are discussed and refined before anyone commits code to a formal on-chain proposal.

Sources:
Tezos Documentation: Governance and Self-Amendment
OpenTezos: On-Chain Governance
Octez Documentation: The Amendment and Voting Process