• Docs: typed ICU and MF2 arguments - the README section "ICU and MF2 with the App Router" now describes parseInterpolation: 'icu' / 'mf2' (i18next 26.5.0): the options of t from getT and useT and the values of IcuTrans and IcuTransWithoutContext (react-i18next 17.1.0) are type-checked against the message's arguments, with the resources file from npx i18next-cli types for literal message types. parseInterpolation: false stays the setting for i18next 26.2.0 to 26.4.x. No code changes: getT and useT return i18next's TFunction, so they get the checks as is.
• Example app-router-icu uses parseInterpolation: 'icu' with an i18next.config.ts and a generated @types/resources.d.ts.