Since version 0.3.5, a Delta site can use Automatic.css (ACSS) as its design system, in place of Delta’s own seed.
What Delta is
Delta is a WordPress theme you build and maintain through an AI agent. The agent connects to the site over MCP and works with Delta’s abilities: it creates pages and templates as plain HTML and CSS, keeps notes on the project, and takes a snapshot before changes so they can be undone.
Every Delta site has one design system: the names for colours, type and spacing that all pages use. A new site starts on Delta’s own, called the seed. A site can also use another system, such as a stylesheet you already have or a framework like ACSS.
Why register ACSS
With ACSS only installed, the site has two sets of names for the same jobs, such as --color-action and --primary, and automatic.css prints after the site’s stylesheet. Registered as the design system, ACSS becomes the one source of names: Delta’s map lists the ACSS name for each job, the agent writes CSS with those names, ACSS loads before Delta’s site.css, and Delta does not edit ACSS’s files.
The switch
The agent maps each seed name in use to an ACSS name and shows you the table. A dry run reports any name that would be left without a value. Then Delta takes a snapshot, renames the names, saves the map and changes the mode in one step. On our test site: 37 renames, no name without a value. Afterwards, values change in ACSS: a new base-space or heading weight reached every page.
Delta alone, and with SchemaWP
On its own, Delta gives the agent basic access to ACSS: it can read the variables and settings and change settings, with a snapshot before each change. It does not carry knowledge of the ACSS domain: which keys belong together, which values are generated, and how each part of the framework is meant to be used.
SchemaWP adds that knowledge. When its Agent Connection is on, Delta offers SchemaWP’s abilities in place of its own: patches checked against a registry of ACSS keys, the site’s design rules and context, skills for each domain (colours, typography, spacing, buttons and links, cards, forms, surfaces, shadows and more), kits, history and a health check. Delta still takes a snapshot before each change, and one switch in Delta’s Abilities screen controls whether the agent may change ACSS settings.
Limits
ACSS writes a variable only for a setting that has a value, so fill empty settings such as fonts and weights before the switch. A few jobs have no ACSS setting, such as a control height or a code font; they stay as site names in site.css. Status colour families ship switched off in ACSS; turn them on in the ACSS dashboard.
Where to start
Give your agent the recipe Switch from the seed to Automatic.css. Details are in Use your own design system.