• feat(types): new strictInterpolationChecks type option (default false). With strictInterpolationChecks: true in CustomTypeOptions, t() needs its options for a string with {{variables}}: for 'Hello {{name}}!', t('greeting') is a type error and t('greeting', { name }) compiles. Left out, the variable reaches the UI as the raw {{name}} placeholder. This applies to string keys, selectors, selector arrays and getFixedT, and with strictKeyChecks also to t(key, defaultValue). Without the flag nothing changes. With the flag on, a wrapper that passes on a key type ((key: ParseKeys<'ns'>) => t(key), or a generic K extends ParseKeys) no longer compiles without options, as the variables of its string are not known there. parseInterpolation: 'icu' and 'mf2' require their arguments as before. Thanks @Alex0007 (#2465).
• fix(types): an array of selectors with a plural member now requires count, as a single selector does since v25.9.0. Without count, i18next skips the plural member at runtime, so t([($) => $.item, ($) => $.plain]) returned the plain value while typed as the plural forms. An array of selectors with defaultValue now returns the literal values and the default value ('a' | 'b' | 'x') instead of string. Thanks @Alex0007 (#2465).