Contributor Workflow

Learn the practical process and guidelines for contributing.

Build and Development

Install the following dependencies for best results:

sudo apt update
sudo apt install valgrind cppcheck shellcheck libsecp256k1-dev libpq-dev

Re-run configure and build using make:

make -j$(nproc)


There are various development options enabled by running with --developer. You can log console messages with log_info() in lightningd and status_debug() in other subdaemons.

You can debug crashing subdaemons with the argument --dev-debugger=channeld, where channeld is the subdaemon name. It will run gnome-terminal by default with a gdb attached to the subdaemon when it starts. You can change the terminal used by setting the DEBUG_TERM environment variable, such as DEBUG_TERM="xterm -e" or DEBUG_TERM="konsole -e".

It will also print out (to stderr) the gdb command for manual connection. The subdaemon will be stopped (it sends itself a SIGSTOP); you'll need to continue in gdb.

make -j$(nproc)

Making BOLT Modifications

All of code for marshalling/unmarshalling BOLT protocol messages is generated directly from the spec. These are pegged to the BOLTVERSION, as specified in Makefile.

Source code analysis

An updated version of the NCC source code analysis tool is available at

It can be used to analyze the lightningd source code by running make clean && make ncc. The output (which is built in parallel with the binaries) is stored in .nccout files. You can browse it, for instance, with a command like nccnav lightningd/lightningd.nccout.

Code Coverage

Code coverage can be measured using Clang's source-based instrumentation.

First, build with the instrumentation enabled:

make clean
./configure --enable-coverage CC=clang
make -j$(nproc)

Then run the test for which you want to measure coverage. By default, the raw coverage profile will be written to ./default.profraw. You can change the output file by setting LLVM_PROFILE_FILE:

LLVM_PROFILE_FILE="full_channel.profraw" ./channeld/test/run-full_channel

Finally, generate an HTML report from the profile. We have a script to make this easier:

./contrib/ channeld/test/run-full_channel \
    full_channel.profraw full_channel.html
firefox full_channel.html

For more advanced report generation options, see the Clang coverage documentation.


There are a few subtleties you should be aware of as you modify deeper parts of the code:

  • ccan/structeq's STRUCTEQ_DEF will define safe comparison function foo_eq() for struct foo, failing the build if the structure has implied padding.
  • command_success, command_fail, and command_fail_detailed will free the cmd you pass in.
    This also means that if you tal-allocated anything from the cmd, they will also get freed at those points and will no longer be accessible afterwards.
  • When making a structure part of a list, you will instance a struct list_node. This has to be the first field of the structure, or else dev-memleak command will think your structure has leaked.

Protocol Modifications

The source tree contains CSV files extracted from the v1.0 BOLT specifications (wire/extracted_peer_wire_csv and wire/extracted_onion_wire_csv). You can regenerate these by first deleting the local copy(if any) at directory .tmp.bolts, setting BOLTDIR and BOLTVERSION appropriately, and finally running make extract-bolt-csv. By default the bolts will be retrieved from the directory ../bolts and a recent git version.

e.g., make extract-bolt-csv BOLTDIR=../bolts BOLTVERSION=ee76043271f79f45b3392e629fd35e47f1268dc8

Release checklist

Here's a checklist for the release process.

Leading Up To The Release

  1. Talk to team about whether there are any changes which MUST go in this release which may cause delay.
  2. Look through outstanding issues, to identify any problems that might be necessary to fixup before the release. Good candidates are reports of the project not building on different architectures or crashes.
  3. Identify a good lead for each outstanding issue, and ask them about a fix timeline.
  4. Create a milestone for the next release on Github, and go though open issues and PRs and mark accordingly.
  5. Ask (via email) the most significant contributor who has not already named a release to name the release (use
    devtools/credit --verbose v<PREVIOUS-VERSION> to find this contributor). CC previous namers and team.

Preparing for -rc1

  1. Check that is well formatted, ordered in areas, covers all signficant changes, and sub-ordered approximately by user impact & coolness.
  2. Use devtools/ to collect the changelog entries from pull request commit messages and merge them into the manually maintained This does API queries to GitHub, which are severely
    ratelimited unless you use an API token: set the GH_TOKEN environment variable to a Personal Access Token from
  3. Create a new heading to v<VERSION>rc1, and create a link at the bottom. Note that you should exactly copy the date and name format from a previous release, as the script relies on this.
  4. Update the contrib/pyln package versions: make update-pyln-versions NEW_VERSION=<VERSION>
  5. Create a PR with the above.

Releasing -rc1

  1. Merge the above PR.
  2. Tag it git pull && git tag -s v<VERSION>rc1. Note that you should get a prompt to give this tag a 'message'. Make sure you fill this in.
  3. Confirm that the tag will show up for builds with git describe
  4. Push the tag to remote git push --tags.
  5. Announce rc1 release on core-lightning's release-chat channel on Discord & BuildOnL2.
  6. Use devtools/credit --verbose v<PREVIOUS-VERSION> to get commits, days and contributors data for release note.
  7. Prepare draft release notes including information from above step, and share with the team for editing.
  8. Upgrade your personal nodes to the rc1, to help testing.
  9. Follow reproducible build for Builder image setup. It will create builder images cl-repro-<codename> which are required for the next step.
  10. Run tools/ bin-Fedora-28-amd64 bin-Ubuntu sign script to prepare required builds for the release. With bin-Fedora-28-amd64 bin-Ubuntu sign, it will build a zipfile, a non-reproducible Fedora, reproducible Ubuntu images. Once it is done, the script will sign the release contents and create SHA256SUMS and SHA256SUMS.asc in the release folder.
  11. RC images are not uploaded on Docker. Hence they can be removed from the target list for RC versions. Each docker image takes approx. 90 minutes to bundle but it is highly recommended to test docker setup once, if you haven't done that before. Prior to building docker images, ensure that multiarch/qemu-user-static setup is working on your system as described here.

Releasing -rc2, ..., -rcN

  1. Change rc(N-1) to rcN in
  2. Update the contrib/pyln package versions: make update-pyln-versions NEW_VERSION=<VERSION>
  3. Add a PR with the rcN.
  4. Tag it git pull && git tag -s v<VERSION>rcN && git push --tags
  5. Announce tagged rc release on core-lightning's release-chat channel on Discord & BuildOnL2.
  6. Upgrade your personal nodes to the rcN.

Tagging the Release

  1. Update the; remove -rcN in both places, update the date and add title and namer.
  2. Update the contrib/pyln package versions: make update-pyln-versions NEW_VERSION=<VERSION>
  3. Add a PR with that release.
  4. Merge the PR, then:
    • export VERSION=23.05
    • git pull
    • git tag -a -s v${VERSION} -m v${VERSION}
    • git push --tags
  5. Run tools/ to:
    • Create reproducible zipfile
    • Build non-reproducible Fedora image
    • Build reproducible Ubuntu-v18.04, Ubuntu-v20.04, Ubuntu-v22.04 images. Follow link for manually Building Ubuntu Images.
    • Build Docker images for amd64 and arm64v8
    • Create and sign checksums. Follow link for manually signing the release.
  6. The tarballs may be owned by root, so revert ownership if necessary:
    sudo chown ${USER}:${USER} *${VERSION}*
  7. Upload the resulting files to github and save as a draft.
  8. Send SHA256SUMS & SHA256SUMS.asc files to the rest of the team to check and sign the release.
  9. Team members can verify the release with the help of
    1. Rename release captain's SHA256SUMS to SHA256SUMS-v${VERSION} and SHA256SUMS.asc to SHA256SUMS-v${VERSION}.asc.
    2. Copy them in the root folder (lightning).
    3. Run tools/ --verify. It will create reproducible images, verify checksums and sign.
    4. Send your signatures from release/ to release captain.
    5. Or follow link for manual verification instructions.
  10. Append signatures shared by the team into the SHA256SUMS.asc file, verify with gpg --verify SHA256SUMS.asc and include the file in the draft release.
  11. make pyln-release to upload pyln modules to This requires keys for each of pyln-client, pyln-proto, and pyln-testing accessible to poetry. This can be done by configuring the python keyring library along with a suitable backend. Alternatively, the key can be set as an environment variable and each of the pyln releases can be built and published independently:
    • export POETRY_PYPI_TOKEN_PYPI=<pyln-client token>
    • make pyln-release-client
    • ... repeat for each pyln package.

Performing the Release

  1. Edit the GitHub draft and include the SHA256SUMS.asc file.
  2. Publish the release as not a draft.
  3. Announce the final release on core-lightning's release-chat channel on Discord & BuildOnL2.
  4. Send a mail to c-lightning and lightning-dev mailing lists, using the same wording as the Release Notes in GitHub.
  5. Write release blog, post it on Blockstream and announce the release on Twitter.


  1. Look through PRs which were delayed for release and merge them.
  2. Close out the Milestone for the now-shipped release.
  3. Update this file with any missing or changed instructions.