Multitenancy

Three concepts:

• Supported locales (config('localizer.supported_locales')): static union, evaluated at boot. Drives route registration. Cannot change per request without breaking route:cache.
• Active locales (runtime): subset the user can reach in the current request. Defaults to supported. Narrow via Localizer::setActiveLocales([...]).
• Default locale (runtime): which locale is unprefixed when hide_default_locale is on. Defaults to config('app.fallback_locale'). Override per request via Localizer::setActiveDefaultLocale(...).

Use case: each tenant exposes a different subset of the globally supported locales, possibly with a different default. Configure the union in supported_locales, narrow + redefine the default per request.

Tenant middleware

// app/Http/Middleware/TenantLocales.php
use Closure;
use Illuminate\Http\Request;
use NielsNumbers\LaravelLocalizer\Facades\Localizer;

class TenantLocales
{
    public function handle(Request $request, Closure $next)
    {
        $tenant = $request->tenant(); // your resolver

        Localizer::setActiveLocales($tenant->supported_locales);
        Localizer::setActiveDefaultLocale($tenant->default_locale);

        try {
            return $next($request);
        } finally {
            // Reset for long-running workers (Octane, queue).
            // The Localizer is a singleton; without reset the
            // override leaks into the next request on the worker.
            Localizer::setActiveLocales(null);
            Localizer::setActiveDefaultLocale(null);
        }
    }
}

Middleware order

TenantLocales runs before SetLocale so detection respects the narrowed subset and the tenant default:

->withMiddleware(function (Middleware $middleware) {
    $middleware->web(remove: [
        \Illuminate\Routing\Middleware\SubstituteBindings::class,
    ]);
    $middleware->web(append: [
        \App\Http\Middleware\TenantLocales::class,
        \NielsNumbers\LaravelLocalizer\Middleware\SetLocale::class,
        \NielsNumbers\LaravelLocalizer\Middleware\RedirectLocale::class,
        \Illuminate\Routing\Middleware\SubstituteBindings::class,
    ]);
})

Why not Config::set('app.fallback_locale', ...)?

Three problems:

1. Overloaded. fallback_locale is also Laravel's translation fallback. Mutating it per tenant changes translation behavior, not just URL behavior.
2. Octane leaks. The Config repository survives across requests. Without a reset hook, Tenant A's value bleeds into Tenant B.
3. Boot-time consumers. Some package internals read config at boot. Mid-request mutations don't reach them.

setActiveDefaultLocale() lives on the Localizer singleton (request-scoped), doesn't touch translation config, and is read at request time by every consumer that needs it.

What changes vs. default

• /fr/about on a tenant where fr isn't active: SetLocale ignores the prefix and falls back to the resolution chain; RedirectLocale doesn't strip or add it.
• Route::localizedSwitcherUrl() still iterates supportedLocales(). Filter against Localizer::activeLocales() yourself when rendering.
• route('about') resolves the same as before. Inactive-locale routes still exist physically; the package just won't route the user there.
• hide_default_locale follows the active default. With Tenant B (fr default), route('about') for fr returns /about; /fr/about gets 302'd to /about by RedirectLocale.

Caveat: Route::translate() and per-tenant defaults

Route::translate() does not work correctly when tenants have different default locales. Use Route::localize() instead.

Timing: routes register at boot, your TenantLocales middleware runs at request time. Boot first, middleware second - so when TranslateMacro::register() decides which locale gets the unprefixed variant, no override exists yet, and it falls back to config('app.fallback_locale').

1. BOOT (once per worker)
   Route::translate(...) -> reads config('app.fallback_locale') = 'en'
   registers:
     translated_en.about  -> /en/about
     translated_de.about  -> /de/ueber
     without_locale.about -> /about        ← baked against 'en'

2. REQUEST (Tenant B with 'de' default)
   TenantLocales::handle()
   -> Localizer::setActiveDefaultLocale('de')   ← too late!
   -> routes are fixed; unprefixed = /about, not /ueber

Route::localize() doesn't have this problem: every locale shares the same URI; only the prefix differs, stripped at URL-generation time.

If you really need translated paths and per-tenant defaults, register per-locale without_locale.* routes yourself and extend UrlGenerator to pick between them - see TranslateMacro for a starting point.

API summary

Method	Purpose
Localizer::supportedLocales()	Static union (boot-time).
Localizer::activeLocales()	Runtime subset; defaults to supported.
Localizer::isSupported($locale)	Membership in supported.
Localizer::isActive($locale)	Membership in active.
Localizer::setActiveLocales($array|null)	Narrow (or reset with null).
Localizer::defaultLocale()	Runtime default; defaults to app.fallback_locale.
Localizer::setActiveDefaultLocale($string|null)	Override (or reset with null).