Introduction
Harmonic: open block-building infrastructure for Solana
Harmonic is a highly-configurable, open block-building system for Solana. Validators have full autonomy over how their blocks are built, with the freedom to choose their builder and their scheduling strategy. The result is higher validator revenue potential, stronger network decentralization, and the market structure Solana needs to scale.
Run Harmonic on your validator. Get your validator identity whitelisted by the Harmonic team, then choose your scheduling strategy in your client config. Onboard your validator →
The challenge: block building
Solana wins with performance and open, fair markets. But as Solana scales, building the most profitable and efficient blocks becomes increasingly complex, and that complexity has driven a reliance on specialized, often centralized, block builders.
This presents several challenges:
Lack of competition. Validators may be locked into a single builder solution, hindering their ability to capture value or limiting them to a single sequencing strategy.
Limited control. Validators often have to accept an all-or-nothing block, ceding control over the content and transactions included.
Centralization. Relying on a single builder undermines the network's decentralization, introducing single points of failure and potential censorship.
Inefficient markets. A closed market for block building means the network may not realize its full potential for efficiency and value capture.
Applications also have a growing need that is currently underserved. They need fast and reliable transaction inclusion, predictable sequencing behavior, and the ability to choose what kind of market structure their flow lands in. A closed builder market does not give them that. Competition does.
The solution: a configurable, open block-building system
Harmonic is built on a simple principle: validators, not Harmonic, decide how their blocks are built.
Every validator picks its own scheduling strategy and its own builder. A validator participating in the Solana Foundation Delegation Program can run an SFDP-compliant strategy. A validator prioritizing raw revenue can run MREV. A validator with bespoke requirements can commission a custom scheduler. Harmonic provides the platform; the operator chooses what runs on it.
How Harmonic works
Each validator running Harmonic is bound to a block builder running the scheduling strategy the validator selects. That builder constructs the validator's blocks, and the validator broadcasts the result to the rest of the network. For a deeper look at how blocks flow under this model, see Streaming and the Architecture page.
Core roles
Remote TPU. Aggregates incoming transactions and forwards them to all connected block builders.
Block Builders. Construct blocks using their scheduling strategies.
Block Engine. Connects validators to block builders and routes traffic between them.
Validator. Executes and broadcasts blocks each slot.
Why Harmonic
Harmonic's core principle is validator autonomy. Operators have complete control over how their blocks are built, and Harmonic does not prescribe a path.
Pro-validator. Validators pick their own scheduling strategy and their own builder. The operator owns the decision and the trade-offs that come with it.
Pro-network. Solana's performance ceiling rises when its markets are open and competitive.
Pro-retail. Fair inclusion, no artificial latency, and lower sandwich exposure.
Market structure, incentives, and network health
Harmonic brings Solana closer to being the on-chain NASDAQ. For Solana to reach one million TPS, it needs healthy competition and solutions focused on improving the network. Harmonic complements upcoming network upgrades like higher compute limits.
Harmonic improves market quality because:
When many builders compete, the network wins.
Better, bigger blocks push value to validators and the network, not a single intermediary.
Builder diversity reduces correlated failures and lock-in risk.
Validators get the option to pick a strategy that aligns with their downstream consumers.
Our thesis is simple: fast and fair markets outperform fast but closed systems over the long term. Healthy competition is critical for the long-term health of Solana. The network thrives when builders compete, validators earn more, and users trade inside tighter, more honest spreads.
Decentralization and validator sustainability
Solana's long-term security depends on a large, economically sustainable validator set. Today, many validators operate at thin margins, which concentrates stake among a few large operators and weakens the network's decentralization guarantees.
Harmonic addresses this directly. By giving every validator access to competitive block-building infrastructure and configurable scheduling strategies, Harmonic raises the revenue floor for validators of all sizes. Operators who previously could not justify the economics of running a validator can now capture meaningful block rewards without building proprietary MEV infrastructure or relying on a single intermediary.
The result: more validators can operate sustainably, stake distributes more broadly, and Solana's validator set grows more resilient. Harmonic does not just improve individual validator economics; it strengthens the network by making decentralization economically viable.
Get started
Run a Harmonic validator:
Setup: set up and run a Harmonic validator.
Onboard as a validator →: get your validator identity whitelisted and bound to a builder.
Send bundles as a searcher:
Harmonic Bundles: submit bundles via the searcher gRPC interface.
Bundle Control Accounts: protect your transactions from frontrunning and unwanted bundling.
Apply for searcher access →: get your searcher pubkey whitelisted to send bundles.
Understand the model:
Community
Harmonic is an active project with public client repos:
Socials and support:
Discord — public support for validators and searchers. Good place to ask questions before onboarding, or any time after. Onboarded validators also have a private Telegram or Slack channel with the Harmonic team for day-to-day operational requests.
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