Bitcoin Core

Bitcoin Core is the reference full node software for Bitcoin. It validates blocks and transactions, enforces consensus rules, and relays data across the peer-to-peer network. Running it is how anyone can verify Bitcoin without trusting a third party.

OpenSats began funding Bitcoin Core contributors in 2023 through its LTS program. LTS grantees include Marco Falke, Josie Baker, Sjors Provoost, Vasil Dimov, Gleb Naumenko, Furszy, Will Clark, 0xB10C, Bruno Garcia, Jon Atack, and Andrew Toth. Additional contributors joined through Caring for Core, More for Core, and 5 Grants to Strengthen Bitcoin Development: tdb3, David Gumberg, Hodlinator, L0rinc, kevkevinpal, Daniela Brozzoni, janb84, Naiyoma, and Daniel Pfeifer.

Why fund it?

Fewer than 50 people regularly contribute code to the software running a trillion-dollar network. For comparison, Meta employs around 20,000 engineers for a similar market cap. The combined annual budget across all Bitcoin Core development organizations is around $8 million.

Most of that budget pays for maintenance: bug fixes, test coverage, CI upkeep, build system work, release engineering, and the edge cases users run into. By one estimate, maintenance accounts for more than 70% of all project activity, even though it rarely shows up in release announcements.

The 2024 CoreDev contributor survey ranked "lack of reviewers" as the top source of friction. 71% of the code comes from the top 15 contributors. When one of them steps away, years of context about the codebase, the test suite, and the long tail of historical decisions go with them. Steady funding lets contributors stay long enough to mentor newer reviewers.

What's next?

Review is the main bottleneck. Large pull requests can sit for months waiting for reviewers with the time to dig in, test on real hardware, and stay engaged as the patch goes through rebase after rebase.

Andrew Toth is working on a block validation speedup that would improve both Initial Block Download and processing at the chain tip. L0rinc is benchmarking Core on everything from cloud servers to Raspberry Pis and looking at ways to cut memory usage. Marco Falke maintains the test framework and CI infrastructure the rest of the project depends on.

Private transaction broadcast merged this year. Toth has follow-up work to improve reliability across restarts and give node operators more control over the feature.

Sjors Provoost maintains the Bitcoin Core side of Stratum V2, fixing bugs surfaced by SRI testing and building out the IPC methods mining software needs. He is also working on MuSig2 support through HWI and reviewing the BIP54 consensus cleanup.

The libbitcoinkernel project is pulling Core's consensus engine into a standalone library. janb84 joined a working group tackling the global cs_main lock, replacing it with finer-grained locking so third-party applications can embed the kernel without running a full node.

On the network side, Julien Urraca brought ASMap generation under ten minutes and coordinated collaborative runs to produce canonical ASmaps for Core. Naiyoma is researching P2P fingerprinting defenses.

Build tooling, CI, fuzzing, and release engineering get used on every release but rarely get talked about. Without people maintaining them, none of the rest of this work would ship.