Ouroboros Leios: What It Is and How It Aims to Scale Cardano

If you landed here searching “Ouroboros Leios”, you probably heard that Cardano is finally going to scale. The short answer: Ouroboros Leios is an evolution of Cardano’s consensus protocol designed to substantially increase throughput while preserving security and decentralization. As of August 2026, it is in research, development, and public testnet — not on mainnet. This article explains what it is, how it works, what’s behind the numbers floating around, and what it means for stake pool operators.

What Is Ouroboros Leios

Ouroboros Leios is the next iteration of the proof-of-stake protocol family that powers Cardano. Three things to get oriented:

• It is not a new network. It is an evolution of the current consensus (Ouroboros Praos), not a replacement.
• It does not replace Praos. It works as an additional layer that activates when the network faces high demand. As its product manager puts it: “the king is still Praos.”
• It is under development. The official documentation classifies it as “in research and development”; the code and testnet are public, but there is no mainnet date.

The project is led by Input Output (IOG) and was presented as Cardano’s next scalability bet (official announcement, repository).

How Leios Works

The core idea is simple: instead of processing transactions one after another in a single line, Leios processes them in parallel by separating two functions that currently go together — producing blocks and certifying transactions.

The original paper proposed three block types. The current implementation, known as Linear Leios, simplified the design to two block types in order to ship within a reasonable timeframe. This is not a cut in ambition — it is the natural path any protocol takes from paper to implementation.

The result: larger blocks during congestion and multiple stake pools validating transactions in parallel. The protocol maintains Ouroboros security guarantees — but like everything in blockchain, that needs to be verified under real load.

Two heavens as one. Miyamoto Musashi (宮本武蔵, 1584–1645) — swordsman turned strategist, painter, and writer — founded a school of strategy he called Niten Ichi-ryū (二天一流, “two heavens as one”): two complementary swords, one long and one short, stronger together than either alone, because no single tool handles every condition.

Ouroboros Leios is built on the same idea. The small, fast Praos block that has been Cardano’s heartbeat for years gets a companion: a large endorser block, brought to bear when transaction load demands throughput. Neither replaces the other. The strength is in how the two move together.

— Original text from musashi.network. Image: Musashi Dojo / Input Output.

What Leios’ Product Manager Says

Carlos López de Lara, Product Manager for Leios at IOG, explained it on the podcast Descentralización Total (July 10, 2026). Quotes come from the episode’s automated transcript (ASR), which may contain errors in technical terms; normative data should be checked against the official Leios documentation:

“Leios does not replace the current protocol, which is Praos. It is a protocol that works like an overlay, an additional layer, a protocol that activates only when necessary… the king is still Praos.” — 13:07–14:24

On the design simplification, the transcript describes how the original paper proposed three block types and the current implementation moved to two — referred to as Linear Leios in the documentation and “Linear layers” in the transcript — to accelerate development and reach testnet within a realistic timeframe (08:09–12:12).

On the role of stake pools, he explained that during congestion periods a pool can announce an additional, larger block (endorser block) capable of accepting many more transactions, and the other pools validate it until reaching a quorum of approximately 75% of stake (14:26–15:42).

The full interview (54 min) also covers what activates Leios, Dixtra, the Cardano Constitution, and the path to mainnet — watch video.

What Is Musashi Dojo

Musashi Dojo is the public testnet where Leios is tested under real-world conditions (musashi.network, Leios hub):

• It is a test environment, not the main network. Everything measured there is a performance candidate, not a deployed capacity.
• When does it reach mainnet? There is no confirmed date. The official documentation keeps Leios in R&D. The healthy rule: follow official milestones and validate every announcement against primary sources.

The Numbers: What’s Tested and What’s a Projection

This is where the community gets most confused. The numbers circulating come from different pages with different statuses:

Figure	Official Source	Status
Up to 30–65× throughput	Leios FAQ	Projection, not a testnet measurement
Up to 50× (spec: 30–50×)	“What is Leios”	Design target
~100 TPS (short term) and 1,000+ TPS (long term)	Leios Use Cases	Goal subject to validation

Reading rule: every Leios figure today is a target, projection, or testnet result — not a confirmed production capacity. If a headline does not make this clear, be skeptical.

What Changes for Stake Pools

ChileStakePo operates a stake pool on Cardano, so this hits close to home:

• Hardware and connectivity. Leios may demand more from nodes: bandwidth for moving larger blocks, processing power for parallel validation. A serious pool watches what real requirements emerge on testnet, not what a paper promises.
• Latency and propagation. Performance depends on how blocks travel through the real world — physics rules, as always.
• Endorser blocks. During congestion, a pool can announce an additional, larger block that others certify. This changes the validation dynamic: it is no longer just producing your block and waiting for the next one.
• Security. The Ouroboros family maintains its formal security properties, but behavior under real load needs to be verified.
• For delegators. If you delegate ADA, what matters is not the TPS number in the headline, but how the protocol behaves in production and which pools implement it with technical judgment. ADA stays in your wallet while delegated to a stake pool.

Frequently Asked Questions

• Is Leios on mainnet yet? No. It is in research, development, and testnet. Official documentation keeps it in R&D.
• Does Leios “solve the trilemma”? This is a phrase circulating in the community, not a verified technical claim. We use it as an attributed term, not as our own conclusion.
• What is Linear Leios? The current simplified design (two block types instead of three) to accelerate development and testing.
• Do I need to do anything with my ADA? No. Leios is a protocol change under development, not a wallet update or a fork.

Conclusion: Leios, Without the Hype

Ouroboros Leios is one of Cardano’s most serious bets for scaling without breaking its security and decentralization thesis. What’s missing is not enthusiasm — it’s operational evidence: seeing the protocol behave under load, on testnet first, and on mainnet only when it’s ready.

ChileStakePo will follow Leios’ evolution from the operational side: what’s proven, what’s being tested, and what still needs validation. This is a series — if you found this useful, follow us for the next installment.

Important: Ouroboros Leios remains in research, development, and testnet. This publication does not represent a deployed mainnet capacity or a promise of performance or returns.

Sources: leios.cardano-scaling.org (FAQ, What is Leios, Use Cases, Strategy), docs.cardano.org (Ouroboros overview), github.com/input-output-hk/ouroboros-leios, musashi.network, interview with Carlos López de Lara (Leios PM at IOG) on Descentralización Total, July 10, 2026 — video. Figures verified 2026-08-03. Note: the interview transcript is auto-generated (ASR); normative data should be checked against the official Leios documentation.