Letterpress is one Hex package and two coordinated npm packages. Install the pinned toolchain, then run:

mix setup
mix check

Changes to grammar, profiles, diagnostics, schemas, artifacts, or browser metadata start in docs/specs/LP.01-letterpress-contract.md. Regenerate with pnpm build:compiler; never hand-edit generated contract files.

Add cross-runtime behavior to conformance/fixtures.json. Use focused unit tests for worker supervision, render budgets, and component lifecycle. Public Elixir modules need docs and specs. Commits use Conventional Commit subjects.

Do not publish packages from a workstation. Follow RELEASING.md; one tag coordinates all three registry artifacts.