What is Cardano's Musashi Dojo Testnet & Leios Upgrade?

Musashi Dojo is the public testnet for Ouroboros Leios, Cardano's (@Cardano) next major scaling upgrade. It went live on June 23, 2026, kicking off a multi-phase program to test the Leios prototype before a planned mainnet upgrade later this year.

The launch is the first time Leios has run on a public network rather than in simulations. It gives stake pool operators and developers a place to break the new system before it ships. Here is how it works, and what each phase is meant to prove.

What is the Leios upgrade?

Ouroboros Leios is an optimistic consensus protocol that builds on Cardano's current Ouroboros Praos. Its job is to push far more transactions through the base layer while keeping Praos's security model, including resistance to an adversary controlling up to roughly half the network's stake. The design is set out in CIP-0164, "Ouroboros Linear Leios - Greater transaction throughput," published in August 2025.

The headline number is throughput. The proposal targets a 10x to 65x increase in transaction capacity, with the official roadmap describing a move from roughly 4.5 KB/s today toward 200 KB/s. Input Output product manager Carlos Lopez de Lara has said the mainnet rollout would start conservatively at around 2x to 5x current capacity, with the higher ceiling unlocked as demand grows.

There is an economic reason behind the engineering. Cardano's staking rewards lean on a reserve that shrinks over time. Higher throughput means more fee revenue, which the project sees as the way to keep paying stake pools once those reserves run low.

How does Leios work?

Leios runs as an overlay on top of Praos rather than replacing it. Under the hood, block producers continue to produce standard Praos blocks, called Ranking Blocks (RBs), on the usual schedule. When demand is high, they can also produce larger Endorser Blocks (EBs) that reference extra transactions in parallel. To keep bandwidth in check, an EB lists transaction hashes rather than full transaction bodies.

Those Endorser Blocks are not trusted automatically. A stake-weighted committee votes on each one using BLS signatures, and only once an EB clears a high voting threshold are its transactions folded into the ledger through later Ranking Blocks. The result is a dual-track system that puts network and compute capacity to work that Praos normally leaves idle.

For stake pool operators, the practical change is small but real. Running a Leios node means generating and registering one extra cryptographic key, a BLS key, alongside the VRF and KES keys they already manage, plus a modest increase in compute and bandwidth.

Why is it called Musashi Dojo?

The testnet is named after Miyamoto Musashi, the 16th-century swordsman, and his strategy text The Book of Five Rings. Its five testing phases borrow the book's five elements, and each one targets a different kind of stress:

• Earth (Chi): basic protocol design validation.
• Water (Sui): exploring and tuning protocol parameters.
• Fire (Ka): real-world conditions, the most demanding phase for stake pool operators testing software, hardware, and node setups.
• Wind (Fu): adversarial testing and stress scenarios.
• Void (Ku): final preparation for mainnet readiness.

The phased structure is the point. Rather than flip a switch, the program ramps up from basic design checks to adversarial stress, so problems surface on a testnet rather than on mainnet.

When does Leios reach mainnet?

Input Output is targeting a mainnet hard fork in late 2026, with Lopez de Lara (@carloslodelar) pointing to a November window, though that depends on the testnet phases going smoothly and the wider ecosystem being ready.

The work is funded. In late May 2026, Cardano's delegated representatives (DReps) approved a treasury proposal of 27.7 million ADA (27,714,342) with about 84% support. Authored by Lopez de Lara and Sebastian Nagel (@ch1bo_), it covers moving Leios from a testnet prototype to a mainnet-ready release candidate, with funds released against milestones and any unused $ADA returned to the treasury.

The longer-term goal is outlined in Cardano's 2030 plan, which aims to lift the network from roughly 800,000 transactions per month to more than 27 million. Praos alone cannot get there. Whether Leios can is what the next several months of testing inside the Musashi Dojo are designed to answer.

Sources:

• Cardano is ready to grow. Leios is how it gets there Official announcement of the 27.7M treasury proposal, the 10x to 65x target, and the milestone-gated, phased rollout to late 2026.
• Ouroboros Leios Official Leios research and development site, with an overview, resources, and monthly review videos.
• CIP-0164 The formal specification for Ouroboros Linear Leios, covering protocol design, security analysis, and throughput targets.
• Ouroboros Leios GitHub Prototype code, impact analysis, technical reports, and the live development tracker.
• Block//45 Input Output's interview with product manager Carlos Lopez de Lara on the testnet, throughput targets, and node changes.