Heya. I don't see Illuminate\Contracts\Application being used anywhere in both Lumen or Laravel.

don't
@driesvints check this line - its wrong.

framework/src/Illuminate/Database/Eloquent/Factories/Factory.php

Line 10 in 6bc7d1b

use Illuminate\Foundation\Application;

Because in case of Lumen we don't use Illuminate\Foundation\Application
we have Laravel\Lumen\Application;
So in this case you should use contract

Use abstract not concrete )) In case packages are used in both frameworks (Lumen + Laravel)

If you need to use those factories please use Laravel instead.

If you think that factories shouldn't be used in Lumen... Then it's up to you.
But from my point of view - if we can(and should) use illuminate packages in Lumen, then it should work correctly

Okay, I've just tried on a fresh Lumen install and factories are working fine for me. So I'm not sure if it's related to anything specific to your setup?

The same trouble with lumen 8.2.1 and 8.2.2.
Class: Illuminate\Database\Eloquent\Factories\Factory
Line 10: use Illuminate\Foundation\Application;

@vborduja maybe you should stop downvoting my comments and give me a proper way to reproduce this?

It's works )) Because it's in try - catch block. And it's returns App
But if, for some reasons we or any other users will decide to move app folder to another location, or change namespace
for example to AppTest
composer.json

    "autoload": {
        "psr-4": {
            "AppTest\\": "app/",
            "Database\\Factories\\": "database/factories/",
            "Database\\Seeders\\": "database/seeders/"
        }
    },

also change namespaces to new one, for making it works in bootstrap/app.php ( App -> AppTest)

Actually I think its just TYPO because everywhere in framework you use
Illuminate\Contracts\Foundation\Application (you can find in vendor folder)
And only at Factory.php uses
Illuminate\Foundation\Application

We don't support moving the app directory and we don't recommend changing the default namespace, sorry.

@driesvints You are right, there is no direct harm as App\ namespace is default for laravel|lumen applications.

In our case, actual issue was the terrible performance degradation of our tests due to bad setup of xdebug in laradock on windows (wsl2).
In short:

1. Every time Model::factory() is used - the Factory::appNamespace() is called in background.
2. Factory::appNamespace() requests Illuminate\Foundation\Application from the container
3. As lumen app is linked to laravel contract Illuminate\Contracts\Foundation\Application, container was throwing the BindingResolutionException.
4. Due to the laradock performance issues - xdebug was spending ~4 secs on processing every exception being thrown.
5. As final result the initial database seeding for our tests was taking up to 2 hours.

We fixed our problem by tweaking laradock setup, but during investigation was found that Factory accidentally uses direct application FQCN while illuminate contract should be used.

I've created a PR with the fix #36089

To be perfectly clear: I'm not opposed to the change to the contract itself. I'm just saying that we don't recommend changing the app directory or the namespace.