Aptos has shifted its Layer 1 to Block-STM v2 as the default parallel transaction execution engine, replacing the previous execution path without requiring developers to redesign their applications around explicit concurrency rules. The change makes the second-generation Block-STM architecture the standard execution mode for Aptos mainnet nodes.
The transition entered the mainnet software through the aptos-node v1.49.1 release, published September 23, which includes a specific change enabling Block-STM v2 by default. Aptos Labs subsequently confirmed the deployment publicly on October 15. Version 1.49.1 marks where the default changed, although newer 1.49.x node releases have since superseded that software build.
Block-STM has been part of Aptos since mainnet launch and uses optimistic parallel execution to process transactions concurrently. Transactions initially execute under the assumption that they will not conflict, after which the engine validates their state dependencies and reruns operations where required. Developers do not need to declare transaction dependencies or manually partition application workloads for the network to exploit available parallelism.
Block-STM v2 Pushes Parallel Execution Further
The architecture uses multi-version memory to track different versions of blockchain state while transactions execute simultaneously. When one transaction depends on another whose result is not yet valid, the engine can suspend that dependent work until the required value becomes available rather than repeatedly executing against state that is likely to change.
That dynamic dependency handling is designed to reduce wasted computation as transaction contention increases. It is particularly relevant for workloads in which many transactions interact with shared contracts, such as decentralized exchanges, liquidations and automated trading systems.
Aptos Labs has positioned Block-STM v2 as an improvement in multicore scalability, targeting increasingly powerful validator hardware and execution environments with as many as 256 CPU cores. However, the 256-core figure is an architectural scaling target rather than a verified mainnet throughput benchmark for Block-STM v2. The v1.49.1 release itself does not publish a measured increase in live network TPS attributable to the new engine.
That distinction separates execution capacity from network throughput. Aptos can execute independent operations concurrently, but end-to-end performance also depends on consensus, networking, storage, state synchronization and the composition of actual transaction workloads.
The upgrade fits a broader infrastructure strategy aimed at handling more demanding automated workloads. Aptos Foundation and Aptos Labs have already committed more than $50 million toward infrastructure for AI agents and machine-driven markets, where transaction frequency and automated execution can place different demands on a blockchain than conventional human interaction.
Encrypted Mempool Adds Opt-In Transaction Privacy
Parallel execution is arriving alongside another mainnet-level change: Aptos’ encrypted mempool. Approved through AIP-144 and now activated, the system allows users to keep a transaction’s function call and arguments encrypted while validators determine its position inside a block.
Encryption happens client-side before submission. After consensus fixes the block ordering, validators collectively reconstruct the decryption key using a stake-weighted threshold process and reveal the payload immediately before execution. Senders and transaction fees remain visible, so the feature protects transaction intent rather than providing complete transaction anonymity.
Petra Wallet already gives users an option to encrypt eligible transactions at signing. Existing Move contracts do not need to be rewritten to receive encrypted-mempool transactions, while Decibel plans to expose the capability to traders as part of its onchain trading infrastructure.
The privacy mechanism complements Block-STM v2 but solves a different problem. Block-STM addresses execution concurrency, while the encrypted mempool limits how much transaction intent is visible before ordering, reducing opportunities for forms of MEV such as frontrunning and sandwich attacks.
Both changes also arrive after Aptos reset its public Testnet following more than 10 billion transactions, an infrastructure-maintenance operation designed to control storage requirements rather than modify mainnet history.
Aptos is therefore changing several layers of its transaction pipeline at once, but the effects should remain separated. Block-STM v2 is now the default mainnet execution engine and encrypted mempool privacy is live as an optional transaction path; neither development, by itself, demonstrates a corresponding increase in real-world transaction demand or mainnet throughput.
Jack Reynolds is SatoshiPick’s infrastructure mind. Based in Denmark, he follows Bitcoin, Ethereum, Layer 1 networks, stablecoins and DeFi with a practical question always in the background: does this actually make crypto work better?
His articles focus on the systems beneath the headlines: settlement rails, protocol upgrades, stablecoin usage, DeFi coordination and the regulatory limits around them. Jack avoids turning technical coverage into a maze. He explains what is live, what is still experimental and why the difference matters.