Contenu source (brut)
<p>Many thanks to Lucas Bruder, Sebastian Hauer, Alejandro Morante, and Mert for reviewing earlier versions of this work.</p><h2>Actionable Insights</h2><ul class="list-bullet"><li value=1>Today, Solana leaders have sole authority over transaction ordering during their slots, offering limited transparency into how blocks are constructed. BAM introduces a verifiable, decentralized alternative that makes sequencing logic auditable.</li><li value=2>The BAM network clearly separates responsibilities: BAM nodes manage sourcing, prioritization, and filtering of Solana transactions, while BAM validators handle execution, consensus, and state management. This approach moves Solana closer to a Proposer-Builder Separation (PBS) like architecture.</li><li value=3>BAM’s plugin framework allows developers to define custom ordering logic and introduce new scheduling primitives. This enables Application-Controlled Execution (ACE), where apps can enforce their own transaction scheduling rules.</li><li value=4>Jito has committed to eventually open-sourcing BAM and designing it with transparency at its core. This marks a major improvement over the current Jito block engine, which is closed-source and run by a single trusted party.</li><li value=5>BAM nodes will run on AMD processors, which support enhanced Secure Encrypted Virtualization with Secure Nested Paging (SEV-SNP). Thanks to hardware acceleration, SEV-SNP introduces only 2–5% overhead, fast enough for real-time processing.</li><li value=6>The first implemented scheduler for BAM nodes will run periodic intra-block auctions within their mempools, subdividing the block into N slots and equally allocating CUs across each auction.</li><li value=7>Application-Controlled Execution (ACE) may reduce the need for rollups or network extensions to enforce custom logic, helping retain more activity on Solana mainnet. It also significantly expands the design space for novel applications that leverage programmable blockspace.</li><li value=8>Jito plans to route 100% of protocol fees from both the Block Engine and the upcoming BAM system to the Jito DAO Treasury. Currently, Jito charges a 6% fee on tips, split evenly between Jito Labs and the DAO. In Q2 2025, the DAO earned 22,391.31 SOL (~$4 million) from these fees via the Tip Router.</li><li value=9>BAM draws inspiration from Flashbots’ BuilderNet, adopting a similar approach of block building within trusted execution environments. On Ethereum mainnet, approximately 40% of blocks are already built in TEEs.</li></ul><h2>Introduction</h2><p>Jito’s Block Assembly Marketplace (BAM) represents the most ambitious redesign of Solana’s block construction process to date. Over eight months in development, BAM was born out of the desire for more privacy, transparency, and deterministic intra-slot execution on Solana to enable the next wave of advanced applications. The result is a re-imagined transaction pipeline that replaces today’s opaque, validator-driven ordering model with a private, programmable, and provably fair system for sequencing transactions.</p><p></p><p>BAM introduces an encrypted mempool running inside Trusted Execution Environments (TEEs), where all transactions remain confidential until execution. This privacy-preserving architecture aims to significantly reduce, if not eliminate, many of the most extractive forms of MEV, providing users with stronger execution guarantees and better pricing. Validators gain the ability to offer higher-quality execution, while developers and searchers can build directly on top of a new programmable layer of blockspace.</p><p></p><p>BAM introduces application-controlled execution (ACE) logic via a plugin system. This enables use cases such as maker-priority matching for perpetuals, just-in-time oracle updates, time-in-force order enforcement, and other forms of custom routing and execution. With fine-grained control over transaction ordering, developers can build more sophisticated and reliable financial primitives on Solana, including central limit order books, dark pools, and aggregator layers.</p><p></p><p>In doing so, BAM directly addresses many of the longstanding criticisms of Solana’s block production model: opaque validator behavior, inconsistent execution quality, and the proliferation of gray markets through private mempools and out-of-band deals. Today, Solana leaders have unilateral control over transaction ordering during their slots, with little insight into how final blocks are assembled. BAM replaces this with a verifiable, decentralized alternative that still integrates cleanly with Solana’s high-performance runtime.</p><p></p><p>BAM builds on real-world precedent and draws inspiration from <a href="https://collective.flashbots.net/t/introducing-buildernet/4173"><span style="text-decoration: underline">Flashbots’ BuilderNet</span></a>, adopting a similar approach of block building within trusted execution environments. On Ethereum mainnet, approximately <a href="https://x.com/DistributedMarz/status/1947459241348108603"><span style="text-decoration: underline">40% of blocks are already built in TEEs</span></a>, while on Unichain (Uniswap’s custom L2), that number reaches 100%. BAM extends this model to Solana, with the advantage of native support for application-level programmability, low-latency execution, and deep integration with the Jito validator clients, which today <a href="https://reports.firedancer.io/"><span style="text-decoration: underline">secure over 89% of total stake</span></a> across Jito-Agave and Jito-Firedancer.</p><p></p><p>Crucially, Jito has committed to eventually open-sourcing BAM and designing it with transparency at its core. This marks a major improvement over the current Jito block engine, which is closed-source and run by a single trusted party. BAM generates on-chain attestations, cryptographically signed proofs that confirm exactly what code was run and how transactions were ordered, enabling any observer to verify fair execution.</p><h2>High-Level Overview of BAM</h2><p>At its core, BAM is a transaction sequencing network. BAM nodes handle the sourcing, prioritization, and filtering of Solana transactions, while BAM validators focus on execution, consensus, and state management. This separation of concerns preserves the core responsibilities critical to network liveness within the validator while enabling greater flexibility and experimentation around sequencing logic within BAM nodes.</p><p></p><p>The BAM node itself comprises a transaction processing unit (TPU) and a transaction scheduler, operating within a TEE. It also runs a gRPC server to enable communication with connected validators. The modified Jito-validator client features a first-in-first-out (FIFO) executor, optimized for concurrency and parallelism through account-aware locking.</p><p></p><p>Each BAM node can support multiple validators, though each validator connects to only one BAM node at a time. Currently, Jito operates <a href="https://docs.jito.wtf/lowlatencytxnsend/#api"><span style="text-decoration: underline">seven block engines</span></a>. With BAM, the network aims to scale significantly, targeting 50 to 100+ BAM nodes distributed across all major geographic regions for greater decentralization and redundancy. Communication between the BAM node and the validator occurs via a bidirectional gRPC stream, with execution results streamed back from the validator to the BAM node for real-time feedback.</p><p></p><img src="/_next/image?url=/api/media/file/BAM-transaction-flow.PNG&w=3840&q=90" alt="BAM Transaction Flow" /><p></p><p>All transactions within BAM nodes are encrypted within Trusted Execution Environments (TEEs) until the moment of execution, ensuring that the transaction flow remains private until it is executed.</p><p></p><p>To guarantee fair execution, the ordering of transactions is verifiably recorded using attestations. These are cryptographic proofs, signed and timestamped by BAM nodes, that confi
