CometBFT

Byzantine-Fault Tolerant State Machine Replication. Or Blockchain, for short.

Branch	Tests	Linting
main
v1.x
v0.38.x
v0.37.x
v0.34.x

CometBFT is a Byzantine Fault Tolerant (BFT) middleware that takes a state transition machine - written in any programming language - and securely replicates it on many machines. In modular blockchain terminology, CometBFT can be thought of as a sequencer layer and is indeed used in modern decentralized (shared) sequencer implementations.

CometBFT is the canonical implementation of the Tendermint consensus algorithm and is a primary building block for the Interchain Stack. Historically, CometBFT originated as a fork of Tendermint Core in early 2023 (announcement here) and since then it diverged significantly by adopting modern features such as PBTS or ABCI v2. CometBFT provides optimistic responsiveness guarantees.

For protocol details, refer to the CometBFT Specification.

For detailed analysis of the Tendermint consensus protocol, including safety and liveness proofs, read our paper, "The latest gossip on BFT consensus".

For general links, including communications and announcements: linktr.ee/cometbft

Documentation

Complete documentation can be found on the website.

Releases

Please do not depend on main as your production branch, as it may receive significant breaking changes at any time. Use releases instead.

If you intend to run CometBFT in production, we're happy to help. To contact us, in order of preference:

• Create a new discussion on GitHub
• Reach out to us via Telegram
• Join the Cosmos Network Discord and discuss in #cometbft

More on how releases are conducted can be found here.

Support Policy

CometBFT aligns with other components of the Interchain Stack and we offer long-term support (LTS) guarantees for certain releases. The complete End of Life (EOL) schedule, LTS plans, and the general support policy is in documented and regularly updated in the discussion Support policy for CometBFT releases #590.

Security

Please see SECURITY.md.

Minimum requirements

Install

See the install guide.

Quick Start

• Single node

Contributing

Please abide by the Code of Conduct in all interactions.

Before contributing to the project, please take a look at the contributing guidelines and the style guide. You may also find it helpful to read the specifications, and familiarize yourself with our Architectural Decision Records (ADRs) and Request For Comments (RFCs).

Versioning

As of v1, CometBFT uses the following approach to versioning:

• Major version bumps, such as v1.0.0 to v2.0.0, would generally involve changes that force users to perform a coordinated upgrade in order to use the new version, such as protocol-breaking changes (e.g. changes to how block hashes are computed and thus what the network considers to be "valid blocks", or how the consensus protocol works, or changes that affect network-level compatibility between nodes, etc.).
• Minor version bumps, such as v1.1.0 to v1.2.0, are reserved for rolling out new features or substantial changes that do not force a coordinated upgrade (i.e. not protocol-breaking), but could potentially break Go APIs.
• Patch version bumps, such as v1.0.0 to v1.0.1, are reserved for bug/security fixes that are not protocol- or Go API-breaking.

Upgrades

We do not guarantee compatibility between major releases of CometBFT. Minor releases of the same major release series (v1.1, v1.2, etc.) should, unless otherwise specified, be compatible with each other. Patch releases of the same minor release series (v1.0.1, v1.0.2, etc.) are guaranteed to be compatible with each other.

For more detailed information on upgrading from one version to another, see UPGRADING.md.

Supported Versions

Because we are a small core team, we have limited capacity to ship patch updates, including security updates. Consequently, we strongly recommend keeping CometBFT up-to-date. Upgrading instructions can be found in UPGRADING.md.

Currently supported versions include:

• v1.x: Currently in pre-release with no guarantees as to API stability until a release candidate is cut. See RELEASES.md for details on our process as to API stability guarantees that can be expected of CometBFT pre-releases.
• v0.38.x: CometBFT v0.38 introduces ABCI 2.0, which implements the entirety of ABCI++
• v0.37.x: CometBFT v0.37 introduces ABCI 1.0, which is the first major step towards the full ABCI++ implementation in ABCI 2.0
• v0.34.x: The CometBFT v0.34 series is compatible with the Tendermint Core v0.34 series

Resources

Libraries

• Cosmos SDK: A framework for building high-value public blockchain applications in Go
• Tendermint in Rust
• ABCI Tower

Applications

• Cosmos Hub
• Celestia
• Anoma
• Vocdoni

Research

Below are links to the original Tendermint consensus algorithm and relevant whitepapers, which CometBFT will continue to build on.

• The latest gossip on BFT consensus
• Master's Thesis on Tendermint
• Original Whitepaper: "Tendermint: Consensus Without Mining"

Join us

CometBFT is currently maintained by Informal Systems. If you'd like to work full-time on CometBFT, we're hiring!

Funding for CometBFT development comes primarily from the Interchain Foundation, a Swiss non-profit. Informal Systems also maintains cometbft.com.