#molt build

Build the distribution artifacts -- an sdist and a wheel per package -- for the packages a publish plan will ship.

This is the pack stage of the publish pipeline. The command you type is molt build; the artifacts it produces are what molt publish --from-pack-dir uploads.

#Synopsis

molt build [OPTIONS]

#Description

On PyPI, building is mandatory and produces two artifacts -- a source distribution (.tar.gz) and a wheel (.whl) -- for every package. There is no implicit build at upload time. molt build runs the ecosystem's build (for example uv build / python -m build) for each package a plan will publish, writes the artifacts to an output directory, and records an enriched publish plan that adds each artifact's path and a sha256 integrity hash to the plan entries.

molt build can compute the plan itself, or take a precomputed one from molt publish-plan via --from-publish-plan. Splitting build from upload lets CI build once and upload from a separate, credentialed job.

If a build fails, molt surfaces the error and writes no plan file -- there is no half-built output to clean up.

#Options

The publish plan is a versioned envelope ({ "version": 1, "plan": [...] }); a plan file with an unrecognized version is rejected. The check is equality, not a floor -- an older envelope is a different document, not a compatible one -- and it also rejects a missing version, a plan that is not a list of chunks, and an envelope that is not an object at all. Nothing is built before the file is accepted.

Each publish entry gains an artifacts list of exactly two entries, sdist first and wheel second, each with a path relative to the output directory and an integrity of the form sha256=<hex>. Paths are written with forward slashes on every platform, so a plan built on Windows is readable by the Linux job that uploads it. Tag-only entries pass through untouched and never gain an artifacts key -- they are never built and never uploaded.

molt build has no --repository flag. When it computes the plan itself it therefore targets the default index, which means the snapshot guardrail applies. To build a snapshot release, compute the plan against your own index first and hand the file over:

molt publish-plan --repository https://packages.internal.example/simple/ --output publish-plan.json
molt build --from-publish-plan publish-plan.json --out-dir dist

#Exit codes

#Examples

Build everything in the current plan into dist/:

molt build

Build from a precomputed plan, into a chosen directory:

molt publish-plan --output publish-plan.json
molt build --from-publish-plan publish-plan.json --out-dir artifacts

Then upload the built artifacts from another job:

molt publish --from-pack-dir artifacts

#See also

• molt publish -- uploads what molt build produces.
• Publishing.