ConstGerman (de) — reviewed translations (Sie-Form). Localized decline messages follow the register a PSP uses: calm, non-technical, reassuring.
English — the source of truth. Adapters produce these user-safe messages directly; other locales translate by CODE, never by string-matching English.
Spanish (es) — reviewed translations (usted, neutral international). Localized decline messages follow the register a PSP uses: calm, non-technical, reassuring.
French (fr) — reviewed translations (vouvoiement). Localized decline messages follow the register a PSP uses: calm, non-technical, reassuring.
The locales PayFanout ships translated error + UI catalogs for out of the box. Hosts extend or override any of them at the edge via
registerErrorMessages/registerUiLabels, and add entirely new locales the same way — these are just the batteries included.