calm-tokens

Define one ThemeExtension per token group (colours, type, spacing, shapes, motion) with an asserting of(context) accessor, and carry every field through copyWith and lerp. Convert CSS blur radius with (cssBlur / 2 - 0.5) / 0.57735 and em tracking with fontSize multiplied by the em value.

ColorScheme.fromSeed builds neutrals from the seed's hue at a fixed chroma, so it cannot reproduce a hand-tuned ramp whose chroma rises across surfaces. Seeding on a brand colour at hue 47 degrees regenerates warm paper surfaces as rosy pink, so the scheme must be hand-authored role by role.

Confine all colour, duration, radius and font-size literals to a single theme directory and run a grep-based CI gate that fails on raw values elsewhere. A second script can verify every ThemeExtension field appears in both copyWith and lerp, catching fields the compiler cannot see.

No. CSS blur radius is 2 sigma while Flutter converts blurRadius with r * 0.57735 + 0.5, so pasting the CSS number ships shadows 1.2 to 1.65 times too soft. The correct conversion is blurRadius = (cssBlur / 2 - 0.5) / 0.57735.

Declare a list of foreground, background and minimum-ratio triples and walk them over both light and dark theme instances in a unit test that fails the build. This turns WCAG 4.5:1 text and 3:1 non-text thresholds into a CI gate rather than a review opinion.

When its measured contrast on the surface is below 4.5:1, such as an amber due colour at 3.44:1. Structure status families as a four-rung ramp where base is the graphic dot, ink is text on tint, tint is the fill, and edge is the boundary, so widgets cannot pick an illegal pairing.