Sustaining Bitcoin Development and Review

OpenSats is pleased to announce four first-time grants and one renewal from our General Fund supporting work on Bitcoin Core and the open-source infrastructure around it. The work in this wave spans Bitcoin Core's release process, validation architecture, and wallet, with a shared focus on keeping critical software maintainable and verifiable.

The first time grant recipients we cover in this wave are:

@futurile
@Yuvicc
@polespinasa
@pablomartin4btc

We have also awarded a grant renewal to:

@jan84 (Mar. 2026)

If you would like to help us continue supporting Bitcoin developers and the open-source projects they depend on, please consider making a one-time or recurring donation.

Let's take a closer look at the respective projects and the work these grants will support.

Futurile

Futurile is a Guix contributor whose work in 2025 included publishing the project's user and contributor survey results and authoring its proposal for regular annual releases. He will continue his work on Guix, a universal build, configuration, and software distribution system. Bitcoin Core uses it to build release binaries deterministically. Independent builders can reproduce the same release, compare the outputs, and publish attestations in guix.sigs. Guix is also used as a per-user package manager and as a full GNU/Linux system.

The grant will support build and distribution infrastructure, performance work, and security automation. Futurile plans to add mirrors and improve how they are selected and operated, build a framework for examining package evaluation and interdependencies, and automate more security updates. These are areas where Guix currently has limited dedicated contributor time.

Repository: guix/guix
PRs: created; reviewed
License: GPLv3 or later

Yuvicc

Yuvicc will spend his time working on The Bitcoin Kernel Project, also known as libbitcoinkernel, to extract Bitcoin Core's validation engine into a reusable C library. One reason for doing so is to let other Bitcoin projects use validation code maintained in Core directly, avoiding the need to rewrite it from scratch. Having to reimplement consensus rules can introduce bugs that cause discrepancies about which transactions are valid, potentially leading to consensus splits. Yuvicc's recent work has touched block headers, serialization, validation-state handling, and context-free block checks.

He also maintains bitcoinkernel-jdk, the JVM wrapper for the C API. Planned work includes improving the C API structure, exposing script and validation errors, adding more context-free consensus methods, and reviewing Kernel-related pull requests. Yuvicc will also continue developing bitcoinkernel-jdk as the upstream API changes. The rest of the grant covers Bitcoin Core testing and review, including mempool and validation tests, chain-reorganization tests, and regular PR review.

Repositories: bitcoin/bitcoin; yuvicc/bitcoinkernel-jdk
PRs: created; reviewed
Licenses: MIT

Pol Espinasa

Pol is a Bitcoin Core contributor who has been focusing primarily on the wallet, with additional work across peer-to-peer networking, the Qt graphical interface, and the functional test framework. His wallet contributions include improvements to fee-setting behavior and internal fee-rate handling, along with review and testing of other contributors' work. His descriptor-import interface was merged into Bitcoin Core in September 2026. The new interface gives the Qt wallet a path to work with imported descriptors, including setups that can be used for multisig.

With support from OpenSats, Pol will continue improving the wallet's maintainability, interoperability, and usability. Planned work includes moving user-facing fee units toward sat/vB, developing support for importing BIP-39 mnemonic phrases and defining how they interact with BIP-380 output descriptors, and working on further improvements around hardware wallets, multisig, and user safety. He will also continue reviewing wallet pull requests and contributing elsewhere in Bitcoin Core when useful. Outside the codebase, Pol organizes BitDevs Barcelona and has helped establish a Spanish-language Bitcoin Core PR Review Club on Discord for contributors learning how to review changes to the project.

Repository: bitcoin/bitcoin
PRs: created, reviewed
License: MIT

Pablo Martin

Pablo Martin has contributed code, reviews, and tests to Bitcoin Core and its graphical interfaces since 2022. His recent work includes command-line option handling and wallet recovery documentation. Pablo has also reviewed peer-to-peer networking changes and mining interfaces, including work on validating block templates from external mining software.

With this grant, Pablo will continue testing and reviewing wallet, command-line, and GUI changes, alongside his own improvements and bug fixes. He plans to increase his involvement in peer-to-peer networking and expand his mining and multiprocess work, including the interfaces that let separate processes exchange requests and data (IPC). His priorities will follow the development work underway, with continued collaboration on longer-running changes.

Repository: bitcoin/bitcoin
PRs: created; reviewed
License: MIT

Release tooling, validation, wallet development, and network interfaces occupy different parts of Bitcoin Core and its supporting infrastructure. Each one needs sustained attention, including the testing and review that sits alongside new code. These grants give five contributors more time to focus on that work as the projects continue to develop.

If you are working on Bitcoin or on free and open-source software that Bitcoin depends on, visit the OpenSats application page to learn about upcoming funding windows and application requirements.

This work is possible because of our donors. To help sustain Bitcoin development and its open-source foundations, please consider supporting the General Fund with a one-time or recurring donation.