Input Output Adds Leios Consensus Features to Cardano Dev Branch for December 2026 Mainnet

Consensus Features Land on the Leios Branch

Building a certification block on the Leios prototype for Cardano (ADA) now takes milliseconds, down from a maximum of 0.9 seconds, and the same development cycle carried the scaling design's consensus machinery onto the main development branch. Input Output (IOG), the firm behind Cardano's core development, said in its November 6 weekly development report that its consensus team added endorsement block generation, certificate checks inside the chain selection process and vote relay functions to the branch. The report files the additions under development work, not a mainnet release, and the distinction matters for throughput claims: none of the branch code has touched the live network. The branch additions change what developers can exercise, not what users experience.

The prototype release notes for rc-2026w44 list adaptive endorsement, a mechanism under which block producers shrink an endorsement block when voting support falls short. The setting ships disabled, so using it on the Musashi test network requires a separate manual switch. Its presence in a prototype does not, by itself, increase current mainnet throughput. The earlier rc-2026w43 prototype carried the timing change: creating a certification block no longer re-applies every transaction held in the mempool, which cut the measured task time from up to 0.9 seconds into the millisecond range. IOG measured that interval inside the prototype's certification process and cautioned that it says nothing about confirmation times or user-perceived speed on the mainnet.

Leios extends Ouroboros Praos, the proof-of-stake scheme that currently produces Cardano's blocks. The design keeps the existing block flow and layers endorsement blocks plus a voting procedure on top to widen transaction capacity. Endorsement blocks carry references that point at transactions rather than the transactions themselves, and the voting stage exists to verify that information. Actual processing performance can only be judged once the design runs on the production blockchain network.

Node 11.1.3 and the 11.3 Candidate

Several steps separate the branch from a mainnet activation. Intersect's November 6 weekly update puts the recommended mainnet node at version 11.1.3. Intersect, the member-based organization that coordinates ecosystem upgrades, publishes the node guidance operators follow. An 11.2 pre-release under trial on DijkstraNet supports only BLS key registration for operators of staking pools and excludes the full Leios feature set. BLS key registration is the pool-operator step that prepares signature material for the upgraded scheme, and the 11.2 pre-release is the only node line supporting it today. The rc-2026w44 prototype, which bundles the full linear Leios functions, remains classified for the Musashi network. Intersect expects an 11.3 release candidate combining all of the features at least two to three weeks after its update, placing the earliest cut in late November.

IOG set out the mainnet route in an October 20 pathway document: a Dijkstra hard fork, BLS key registration by pool operators, mainnet load testing and a governance-approved parameter change, in that order. The document treats code integration as an early stage, with network testing and approvals still ahead of any activation. Throughput targets there are planning figures, not measurements. The first phase aims for roughly 3 to 5 times current capacity, and parameter changes after it would target roughly 10 to 15 times. Load testing on the mainnet follows the hard fork and key registration, and the parameter change needs an on-chain governance approval before it takes effect. The stake pool base that must adopt these keys is already shifting: on-chain records show 131.63 million Cardano (ADA) sitting idle in retired stake pools. For operators weighing their role, a walkthrough of how to choose a Cardano stake pool covers delegation mechanics and selection criteria. The 11.1.3 recommendation means mainnet operators can sit out the pre-release entirely until the Leios candidate matures.

IOG Labs' Leios project page, checked on November 9, holds the mainnet deployment target at December 2026 and lists community review and on-chain governance as deployment conditions. That leaves about seven weeks for an 11.3 release candidate that had not been cut when Intersect wrote on November 6, followed by load testing and parameter approvals. The weekly report carried no ADA price reaction and no fee figures, and the prototype's millisecond timing does not translate into faster mainnet confirmations on its own. The December 2026 date is the deadline the new branch features now have to absorb, and the 11.3 candidate is the next checkpoint on the way to it.