X_UI_CONTRAST_INSUFFICIENT
Means
a brand palette pairing does not meet WCAG 2.2 AA
Typical cause
a defineTheme() override whose RESOLVED channels — the app's overrides on top of the shipped palette — put a pairing in CONTRAST_PAIRS below its floor: 4.5:1 for text (WCAG 2.2 1.4.3), 3:1 for the focus ring (1.4.11), 1.4:1 for a border. Only pairings the brand can have CHANGED are measured, because blaming an app for the framework's own colours is how a rule gets switched off — and half a pairing is the usual defect: a new accent against the shipped white accent-fg. AA and never APCA: APCA is not a standard, and AA is the operative legal benchmark (EN 301 549, ADA Title II, the EAA)
Fix
darken or lighten the named role's channels in defineTheme({ colors: { <theme>: { '<role>': '<R G B>' } } }) until contrastRatio() answers the required number — @ultimat3/ui exports contrastRatio and roleContrast to measure a candidate before shipping it