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2025 Q4 Besu

Project Health

Besu completed implementation of the Fusaka hardfork and related protocol upgrades during Q4 2025. This quarter continued making further progress on performance optimisation and syncing performance.

Major Accomplishments This Quarter

Fusaka Hardfork: Final Besu mainnet release with fork times scheduled for mainnet for Osaka, BPO1 and BPO2. Increased Ethereum mainnet gas limit from 36M to 60M per EIP-7935. Testnet support released in September and October with validation on Holesky, Sepolia, and Hoodi.

Glamsterdam Protocol Development: Ongoing implementation work for the next Ethereum network upgrade with multiple merged PRs focused on EIP-7928 Block Access Lists (BAL).

Tech Debt: Continued removal of POW from Besu. Removed PoW-specific RPC methods and CLI options as breaking changes. Removed PoW tests and JSON block importer support, added Clique mining deprecation messaging, and announced sunsetting of PoW consensus, Clique block production, and Fast Sync features.

Performance Optimizations: EQ opcode optimization, MOD-related opcode performance enhancements, EcRecover precompile and CallDataCopy optimizations, 5-6x faster toFastHex calculation for engine_getBlobsV2, engine_getPayload* method optimizations and Java 25 optimized VM options in startup scripts.

History Expiry: Implemented ERA1 file export functionality, complementing existing import capabilities for historical chain data archival and supporting Ethereum's history expiry roadmap.

Quarterly Release Summary

During Q4 2025, the Besu project released:

  • Besu 25.10.0 (October): Fusaka testnet support, PeerDAS dependency updates, and EVM opcode performance improvements
  • Besu 25.11.0 (November): Mainnet release for Fusaka with Osaka/BPO fork scheduling and 60M gas limit increase
  • Besu 25.12.0 (December): Optimisation of engine RPC blobs API, experimental callTracer tracer option in debug_trace RPCs, transaction receipt encoding fix for eth/69

Mainnet operators were required to upgrade to 25.11.0 before the December 3 deadline.

Questions/Issues for the TAC

None

Releases

Major Releases (Q4 2025)

  • Besu 25.10.0
    • Fusaka testnet support with PeerDAS dependency updates
    • Optional sender balance checks in the layered txpool
    • Manage unexpected exceptions during block creation
    • Add blockTimestamp to eth_getLogs result
    • Performance improvements to EQ opcode
    • Performance improvements for MOD related opcodes
  • Besu 25.11.0
    • Fusaka mainnet-ready release with Osaka, BPO1, and BPO2 fork scheduling and 60M gas limit increase
    • Add blockTimestamp to receipt logs for eth_getBlockReceipts and eth_getTransactionReceipt results
    • Ability to enable/disable stack, storage and returnData tracing data in debug_traceStandardBlockToFile and debug_traceStandardBadBlockToFile endpoints
    • Support blob fee market when zeroBaseFee enabled for forks with blobs
  • Besu 25.12.0
    • Linea named networks for linea_mainnet and linea_sepolia
    • Added eth_subscribe and eth_unsubscribe support to IPC service
    • Experimental callTracer tracer option to debug_trace* methods
    • 5-6x faster toFastHex calculation for engine_getBlobsV2
    • Optimise engine_getPayload* methods and engine_getBlobsV2
    • Optimise performances of AND, OR, XOR and NOT opcodes
    • Fix an issue where Besu does not support 0x80 as transaction type when decoding eth/69 receipts

Point Releases and Patches

Key fixes throughout the quarter included: - Block Access List (BAL) bug fixes and optimizations - Transaction receipt type encoding fix - Memory leak in Bonsai storage where RocksDB transactions were not being closed properly - Non-deterministic sub-protocol registration during IBFT2 to QBFT consensus migration - Ethstats integration failing to provide block updates to ethstats server

Overall Activity in the Past Quarter

Community Engagement

GitHub Activity: The Besu repository has 237 contributors and 1,737 stars. Q4 saw 207 commits merged from 28 unique contributors, with 68 new issues opened during the quarter addressing Fusaka upgrade challenges, bug reports, and feature requests. The quarter welcomed 12 first-time contributors working on performance improvements and bug fixes.

Discord and Support Channels: The Besu community had strong engagement throughout Q4, particularly around performance improvements, protocol development especially Block Access Lists, and Glamsterdam fork discussions.

Cross-Client Collaboration: Active engagement in Ethereum All Core Devs (ACDC) calls throughout Q4, coordinating Fusaka development with other execution clients.

Documentation and Developer Experience: New CLI options were documented for ethstats reporting, plugin transaction selection, transaction pool balance checking, and snap sync configuration. Documentation was added for new RPC methods and Linea named network support. Deprecation notices were published for Clique block production, Holesky/Mordor/ETC Classic networks, and PoW-specific features, with corresponding removal of deprecated PoW RPC methods and miner CLI options from documentation.

Technical Development

Protocol Implementation: Focus on Ethereum protocol upgrades with 207 commits in Q4: - EIP-7928 (Block Access Lists): Implementation with 33+ merged PRs covering parallel world state root hash calculation, nonce encoding fixes, CALL recipient inclusion logic, and BAL-based state root computation - EIP-7935 (Gas Limit Increase): Raised mainnet gas limit from 36M to 60M - Fusaka hardfork: Support for Osaka, BPO1, and BPO2 fork scheduling on mainnet (December 3) and testnets (Holesky, Sepolia, Hoodi) - Engine API updates for new payload versions and blob handling - Blob fee market support when zeroBaseFee enabled for blob-supporting forks

Performance Optimization: Continued work toward Gigagas performance targets: - EVM opcode optimizations: EQ, MOD-related operations (SMOD, ADDMOD, MULMOD), bitwise operations (AND, OR, XOR, NOT) - Engine API performance: 5-6x faster toFastHex calculation for engine_getBlobsV2, optimizations to engine_getPayload* methods - EcRecover precompile and CallDataCopy optimizations - Block header cache with preloading capability - Parallel world state root hash calculation from Block Access Lists - Updated jc-kzg dependency for PeerDAS support - Java 25 optimized VM options integration

Enterprise and Private Network Features: - Linea network support (linea_mainnet, linea_sepolia) - IBFT2 to QBFT migration improvements - Plugin transaction selection timeout controls and transaction pool balance checking - Block header caching with configurable preloading

Security and Stability

Security Response: Promptly addressed multiple security vulnerabilities.

Testnet Validation: Testing on Holesky, Sepolia, and Hoodi testnets throughout October and November before mainnet deployment.

Current Plans

BPO Monitoring: Monitor blob throughput performance following BPO1 (December 9) and BPO2 (January 7) activations to assess impact of increased blob capacity on network performance and resource utilization.

Peformance Optimisations: - Optimisation of arithmetic EVM operations - Performance improvements through optimisation of Tuweni data types - Increase parallelisation of syncing to improve initial sync time

Protocol Development: Begin implementation work for the Glamsterdam Ethereum network upgrade: - Continue development of Block Access Lists (EIP-7928) implementation based on mainnet performance data - Implementation of Considered for Inclusion and Proposed for Inclusion EIPs - Participate in specification discussions and testing coordination with other execution clients

Enterprise and Private Network Features - Bonsai archive and Bonsai archive proofs data storage options

Maintainer Diversity

Maintainer diversity held steady in Q4 with 21 active maintainers, consistent with the previous quarter::

  • Consensys: ~19 maintainers (~90%)
  • Kaleido: 1 maintainer (~5%)
  • Unknown: 1 maintainer (~5%)

Organizational diversity among maintainers continues as a challenge.

Active Contributors

Contributors beyond the core maintainer group include: - Cross-client developers: Contributors from Ethereum Foundation and other client teams focused on differential fuzzing, evmtool testing, cross-client compatibility, and EIP-7928 Block Access Lists implementation - Performance optimization contributors: Contributions from quadratic-labs on MOD opcode optimizations - Enterprise users: Bug fixes and feature enhancements from organizations deploying private networks - Individual developers: 12 first-time contributors in Q4 working on performance improvements and bug fixes

Maintainer Growth

The project continues efforts to add new maintainers from organizations building both public and private networks, focusing on contributors who demonstrate consistent engagement and technical expertise.

Project Adoption and Usage

Public Network Usage

Besu holds approximately 16% of mainnet execution layer stake maintaining its critical role in Ethereum's client diversity. Besu is the third most popular Ethereum execution client behind Geth and Nethermind.

Institutional Confidence: Major staking providers maintain Besu deployments within their multi-client infrastructure, strengthening network resilience.

Enterprise and Private Networks

Financial Services: Adoption in financial services continues, with institutions leveraging Besu's QBFT consensus and enterprise features.

Layer 2 Integration: Presence in Layer 2 scaling solutions, with Besu serving as execution layer infrastructure for rollup projects including Linea. Development of plugin APIs to support additional Layer 2 implementations.

Private Networks: Adoption for permissioned networks leveraging QBFT consensus.

This report covers the period October 1 - December 31, 2025. For additional information or clarification on any items in this report, please contact the Besu maintainer team through the project's official channels.