Every locale carries the same keys as the source

Every locale must define exactly the keys the source locale defines.

Why it is a rule

Typed translation keys prove a key exists in the source locale. Nothing proves it was copied to the others, so a key added to one locale alone silently falls back at runtime for every other language. The problem is visible only to users of those languages, which is usually nobody on the team.

What is expected

Add the key to the source locale, then add the identical key to every other locale. Copying the source text verbatim is the convention until a translation arrives; a placeholder in the wrong language is better than a missing key.

Keys the source does not have

These are reported too. They are usually a rename applied to one locale but not the rest.

Layouts

Two catalog layouts are supported, selected with the layout option:

• directory-per-locale (default): locales/<locale>/<namespace>.json, one directory per locale, one JSON file per namespace.
• file-per-locale: locales/<locale>.json, one flat JSON file per locale. Region codes such as en-US.json work.

Locales are discovered from the layout. Pass locales explicitly to pin the set, for example when the directory also holds files that are not catalogs.