Protocol Alpha

This page contains all the relevant information for protocol Alpha, a development version of the Tezos protocol.

The code can be found in the src/proto_alpha directory of the master branch of Tezos.

This page documents the changes brought by protocol Alpha with respect to Florence.

The main novelties in the Alpha protocol are:

  • an upgrade of the consensus algorithm Emmy+ to Emmy*, which brings smaller block times and faster finality

  • a 2.5 tez per block subsidy to a CPMM contract to generate liquidity between tez and tzBTC

Here is the complete list of changes:


Emmy* updates Emmy+ by:

  • a tweak in the definition of the minimal delay function, and

  • an increase in the number of endorsement slots per block

Concretely, in Emmy* a block can be produced with a delay of 30 seconds with respect to the previous block if it has priority 0 and more than 60% of the total endorsing power per block, which has been increased to 256 (from 32) endorsement slots per block.

The baking and endorsing rewards are updated as follows:

  • The reward producing a block at priority 0 is updated from e * 1.25 tez to e * 0.078125 tez, and for producing a block at priority 1 or higher, is updated from e * 0.1875 tez to e * 0.011719 tez, where e is the endorsing power of the endorsements contained in the block.

  • The reward for endorsing a block of priority 0 is updated from 1.25 tez to 0.078125 tez per endorsement slot, and for endorsing a block at priority 1 or higher is updated from 0.833333 tez to 0.052083 tez per endorsement slot.

The values of the security deposits are updated from 512 tez to 640 tez for baking, and from 64 tez to 2.5 tez for endorsing.

The constant hard_gas_limit_per_block is updated from 10,400,000 to 5,200,000 gas units.

The Michelson NOW instruction keeps the same intuitive meaning, namely it pushes the minimal injection time on the stack for the current block. However, this minimal injection time is not 1 minute after the previous block’s timestamp as before, instead it is 30 seconds after.

The values of the BLOCKS_PER_* constants has doubled in order to match the reduced block times, as follows: BLOCKS_PER_CYCLE = 8192, BLOCKS_PER_COMMITMENT = 64, BLOCKS_PER_ROLL_SNAPSHOT = 512, and BLOCKS_PER_VOTING_PERIOD = 40960. This partially solves issue: tezos#1027

Liquidity Baking

2.5 tez per block is credited to a constant product market making (CPMM) contract, the contract’s %default entrypoint is called to update its storage, and the credit is included in block metadata as a balance update with a new update_origin type, Subsidy.

The liquidity baking subsidy shuts off automatically at a fixed level if not renewed in a future upgrade. The sunset level is included in constants.

At any time bakers can vote to shut off the liquidity baking subsidy by setting a boolean flag in protocol_data. An exponential moving average (ema) of this escape flag is calculated with a window size of 1000 blocks and the subsidy permanently shuts off if the ema is ever over a threshold included in constants (half the window size with precision of 1000 added for integer computation).

More detailed docs for liquidity baking can be found here.

RPC changes

  • Remove deprecated RPCs and deprecated fields in RPC answers related to voting periods. (MR tezos!2763, addresses issue `tezos#1204 <>__.)

  • The RPC ../<block_id>/required_endorsements has been removed.

  • Replace deposit by deposits in frozen_balance RPC.

  • All the protocol-specific RPCs under the helpers path have been

moved from the protocol to the recently introduced RPC plugin. This change should not be visible for end-users but improves the maintainability of these RPCs.

Minor changes