Harmonic is an open block-building system for Solana, designed to make the network faster, fairer, and more decentralized. It aggregates blocks from multiple independent builders to optimize validator revenue and network throughput while minimizing MEV and latency. With features like policy-compliant block inclusion, MEV-aware scheduling, and optional ACE (Application Controlled Execution) support, Harmonic empowers validators, developers, and users to participate in a transparent, competitive block market.