Assets are the raw content files used by templates — HTML markup, PDF files, images, and CSS stylesheets. Each asset is versioned and can reference other assets (e.g. an HTML asset can include other HTML assets as Handlebars partials, reference CSS for styling, and embed images via the {{asset_url 'alias'}} helper).

Assets follow the standard SignStack resource lifecycle: iterate in a draft, then publish to an immutable semver. Templates that pin a specific asset version (e.g. letterhead@1.0.0) keep rendering against the exact bytes they were built against, even after newer versions ship.