Impeccable gives coding agents a design vocabulary: same model, same brief, a page built around one night view instead of the cream default

Without design guidance, coding agents repeatedly produce the same templated interfaces: Inter for everything, purple-to-blue gradients, cards nested in cards, gray text on colored backgrounds, and a rounded-square icon tile above every heading. Previously, asking an agent for a page with no other guidance made these styles show up again and again across models and projects. With the same model, Fable 5.1, and the same brief for a fourteen-room family guesthouse on the Ligurian coast, the run without Impeccable produced the tasteful default: cream page, thin serif, italic accent and pill buttons.

With Impeccable installed, the page from the same brief is built around one picture: the house at night, seen from the water. The comparison is the default produced without it, with the model and the brief unchanged. This contrast comes from two generations under the guesthouse brief and is an example given by the releaser, not a cross-task statistic.

The workflow starts with one initialization per project, which reads the code, asks only what it cannot infer, and writes PRODUCT.md, which every later command reads. Previously design intent could only be conveyed through vague requests such as making it pop, leaving the agent to guess. Initialization runs once per project; the document command captures the existing visual system in DESIGN.md so later changes stay on-brand.

Commands are split by target: bolder loads a playbook written for one specific move and points it at one target, critique scores design against usability heuristics and ranks what to fix first, and audit checks accessibility, performance, theming and responsive behavior with findings ranked P0 to P3. Review is no longer a single glance at a whole page but is aimed at one component or flow. The releaser recommends picking one component, such as running critique on the pricing cards; narrow targets get better results, and one section reviewed closely beats a whole page at a glance.

The releaser states that Impeccable is strongest on interfaces that already exist; it also builds new pages, but that is the harder mode. Live mode edits a local checkout only and should not be injected into a deployed site or have a production CSP weakened to make it work.

The 62 rules are described as deterministic, with no LLM and no API key, but the material gives no false-positive or false-negative behavior for these rules on real projects; the page difference with and without Impeccable comes from a single example given by the releaser.