feat(railpack): add buildpack control var filtering and dev seeder

Extract NIXPACKS_/RAILPACK_ prefix filtering into a reusable
`scopeWithoutBuildpackControlVariables` query scope on EnvironmentVariable.
Apply scope consistently to runtime vars, runtime preview vars, and
buildtime var generation in ApplicationDeploymentJob.

Refactor `generate_railpack_env_variables` to return a Collection.
Add `RAILPACK_FRONTEND_IMAGE` constant and bake it into the
coolify-helper Dockerfile as a build arg.

Add DevelopmentRailpackExamplesSeeder (dev/local env only) for
seeding example Railpack apps, wired into DatabaseSeeder.

Add tests:
- ApplicationDeploymentControlVarFilteringTest: verifies control vars
  are excluded from runtime and buildtime envs
- DevelopmentRailpackExamplesSeederTest: verifies seeder behavior
- ApplicationDeploymentRailpackEnvParityTest: parity checks for env
  handling across build/runtime paths

tests/Feature/ApplicationDeploymentControlVarFilteringTest.php

@@ -0,0 +1,287 @@
+<?php
+
+use App\Jobs\ApplicationDeploymentJob;
+use App\Models\Application;
+use App\Models\ApplicationDeploymentQueue;
+use App\Models\ApplicationPreview;
+use App\Models\Environment;
+use App\Models\EnvironmentVariable;
+use App\Models\Project;
+use App\Models\Server;
+use App\Models\Team;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Collection;
+
+uses(RefreshDatabase::class);
+
+class TestableControlVarFilteringDeploymentJob extends ApplicationDeploymentJob
+{
+    public array $recordedCommands = [];
+
+    public ?string $writtenDockerfile = null;
+
+    public function __construct() {}
+
+    public function execute_remote_command(...$commands)
+    {
+        $this->recordedCommands[] = $commands;
+
+        foreach ($commands as $command) {
+            $commandString = is_array($command) ? ($command['command'] ?? $command[0] ?? null) : $command;
+
+            if (! is_string($commandString)) {
+                continue;
+            }
+
+            if (preg_match('/echo .*?([A-Za-z0-9+\\/=]{16,}).*?\\| base64 -d \\| tee \\/artifacts\\/test-app\\/Dockerfile > \\/dev\\/null/', $commandString, $matches) === 1) {
+                $this->writtenDockerfile = base64_decode($matches[1]) ?: null;
+            }
+        }
+    }
+}
+
+function makeDeploymentControlVarFixture(array $applicationAttributes = []): array
+{
+    $team = Team::create([
+        'name' => 'Control Var Team',
+        'description' => 'Team for deployment control var tests.',
+        'personal_team' => false,
+        'show_boarding' => false,
+    ]);
+    $project = Project::create([
+        'name' => 'Control Var Project',
+        'team_id' => $team->id,
+    ]);
+    $environment = Environment::where('project_id', $project->id)->firstOrFail();
+    $server = Server::factory()->create([
+        'team_id' => $team->id,
+    ]);
+
+    $application = Application::factory()->create([
+        'environment_id' => $environment->id,
+        'build_pack' => 'dockerfile',
+        ...$applicationAttributes,
+    ]);
+
+    $application->settings()->update([
+        'inject_build_args_to_dockerfile' => true,
+        'include_source_commit_in_build' => false,
+        'is_env_sorting_enabled' => false,
+    ]);
+
+    return [$application->fresh(), $server];
+}
+
+function createApplicationEnvironmentVariable(Application $application, array $attributes): EnvironmentVariable
+{
+    return EnvironmentVariable::create([
+        'resourceable_type' => Application::class,
+        'resourceable_id' => $application->id,
+        'is_preview' => false,
+        'is_runtime' => true,
+        'is_buildtime' => true,
+        'is_multiline' => false,
+        'is_literal' => false,
+        ...$attributes,
+    ]);
+}
+
+function makeControlVarFilteringJob(Application $application, Server $server, array $overrides = []): array
+{
+    $job = new TestableControlVarFilteringDeploymentJob;
+    $reflection = new ReflectionClass(ApplicationDeploymentJob::class);
+
+    $queue = Mockery::mock(ApplicationDeploymentQueue::class);
+    $queue->shouldReceive('addLogEntry')->andReturnNull();
+
+    $properties = [
+        'application' => $application->fresh(),
+        'application_deployment_queue' => $queue,
+        'build_pack' => $application->build_pack,
+        'mainServer' => $server,
+        'pull_request_id' => 0,
+        'commit' => 'HEAD',
+        'workdir' => '/artifacts/test-app',
+        'deployment_uuid' => 'deployment-uuid',
+        'dockerfile_location' => '/Dockerfile',
+        'container_name' => 'control-var-app',
+        'coolify_variables' => null,
+        'dockerSecretsSupported' => false,
+    ];
+
+    $mergedProperties = array_merge($properties, $overrides);
+    $mergedProperties['saved_outputs'] = new Collection($overrides['saved_outputs'] ?? []);
+
+    if (($mergedProperties['pull_request_id'] ?? 0) !== 0 && ! array_key_exists('preview', $mergedProperties)) {
+        $mergedProperties['preview'] = ApplicationPreview::create([
+            'application_id' => $application->id,
+            'pull_request_id' => $mergedProperties['pull_request_id'],
+            'pull_request_html_url' => 'https://example.com/pr/'.$mergedProperties['pull_request_id'],
+            'fqdn' => 'https://preview.example.com',
+        ]);
+    }
+
+    foreach ($mergedProperties as $property => $value) {
+        $reflectionProperty = $reflection->getProperty($property);
+        $reflectionProperty->setAccessible(true);
+        $reflectionProperty->setValue($job, $value);
+    }
+
+    return [$job, $reflection];
+}
+
+function invokeDeploymentJobMethod(object $job, ReflectionClass $reflection, string $method): mixed
+{
+    $reflectionMethod = $reflection->getMethod($method);
+    $reflectionMethod->setAccessible(true);
+
+    return $reflectionMethod->invoke($job);
+}
+
+function readDeploymentJobProperty(object $job, ReflectionClass $reflection, string $property): mixed
+{
+    $reflectionProperty = $reflection->getProperty($property);
+    $reflectionProperty->setAccessible(true);
+
+    return $reflectionProperty->getValue($job);
+}
+
+it('filters buildpack control vars from generic build args', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'APP_ENV',
+        'value' => 'production',
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'NIXPACKS_NODE_VERSION',
+        'value' => '22',
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'RAILPACK_NODE_VERSION',
+        'value' => '20',
+    ]);
+
+    [$job, $reflection] = makeControlVarFilteringJob($application, $server);
+
+    invokeDeploymentJobMethod($job, $reflection, 'generate_env_variables');
+
+    /** @var Collection $envArgs */
+    $envArgs = readDeploymentJobProperty($job, $reflection, 'env_args');
+
+    expect($envArgs->get('APP_ENV'))->toBe('production');
+    expect($envArgs->has('NIXPACKS_NODE_VERSION'))->toBeFalse();
+    expect($envArgs->has('RAILPACK_NODE_VERSION'))->toBeFalse();
+});
+
+it('filters buildpack control vars from preview build-time env files', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'APP_ENV',
+        'value' => 'production',
+        'is_preview' => true,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'NIXPACKS_NODE_VERSION',
+        'value' => '22',
+        'is_preview' => true,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'RAILPACK_NODE_VERSION',
+        'value' => '20',
+        'is_preview' => true,
+    ]);
+
+    [$job, $reflection] = makeControlVarFilteringJob($application, $server, [
+        'pull_request_id' => 42,
+    ]);
+
+    /** @var Collection $buildtimeEnvs */
+    $buildtimeEnvs = invokeDeploymentJobMethod($job, $reflection, 'generate_buildtime_environment_variables');
+
+    expect($buildtimeEnvs->contains(fn (string $env) => str($env)->startsWith('APP_ENV=')))->toBeTrue();
+    expect($buildtimeEnvs->contains(fn (string $env) => str($env)->startsWith('NIXPACKS_NODE_VERSION=')))->toBeFalse();
+    expect($buildtimeEnvs->contains(fn (string $env) => str($env)->startsWith('RAILPACK_NODE_VERSION=')))->toBeFalse();
+});
+
+it('filters buildpack control vars from preview runtime env fallback', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'APP_NAME',
+        'value' => 'coolify',
+        'is_runtime' => true,
+        'is_buildtime' => false,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'NIXPACKS_NODE_VERSION',
+        'value' => '22',
+        'is_runtime' => true,
+        'is_buildtime' => false,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'RAILPACK_NODE_VERSION',
+        'value' => '20',
+        'is_runtime' => true,
+        'is_buildtime' => false,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'PREVIEW_FLAG',
+        'value' => 'enabled',
+        'is_preview' => true,
+        'is_runtime' => true,
+        'is_buildtime' => false,
+    ]);
+
+    $application->environment_variables_preview()
+        ->whereIn('key', ['APP_NAME', 'NIXPACKS_NODE_VERSION', 'RAILPACK_NODE_VERSION'])
+        ->delete();
+
+    [$job, $reflection] = makeControlVarFilteringJob($application, $server, [
+        'pull_request_id' => 99,
+    ]);
+
+    /** @var Collection $runtimeEnvs */
+    $runtimeEnvs = invokeDeploymentJobMethod($job, $reflection, 'generate_runtime_environment_variables');
+
+    expect($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('APP_NAME=')))->toBeTrue();
+    expect($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('PREVIEW_FLAG=')))->toBeTrue();
+    expect($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('NIXPACKS_NODE_VERSION=')))->toBeFalse();
+    expect($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('RAILPACK_NODE_VERSION=')))->toBeFalse();
+});
+
+it('filters buildpack control vars from dockerfile arg injection', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'APP_ENV',
+        'value' => 'production',
+        'is_runtime' => false,
+        'is_buildtime' => true,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'NIXPACKS_NODE_VERSION',
+        'value' => '22',
+        'is_runtime' => false,
+        'is_buildtime' => true,
+    ]);
+    createApplicationEnvironmentVariable($application, [
+        'key' => 'RAILPACK_NODE_VERSION',
+        'value' => '20',
+        'is_runtime' => false,
+        'is_buildtime' => true,
+    ]);
+
+    [$job, $reflection] = makeControlVarFilteringJob($application, $server, [
+        'saved_outputs' => [
+            'dockerfile' => "FROM php:8.4-cli\nRUN php -v",
+        ],
+    ]);
+
+    invokeDeploymentJobMethod($job, $reflection, 'add_build_env_variables_to_dockerfile');
+
+    expect($job->writtenDockerfile)->toContain('ARG APP_ENV=production');
+    expect($job->writtenDockerfile)->not->toContain('ARG NIXPACKS_NODE_VERSION=');
+    expect($job->writtenDockerfile)->not->toContain('ARG RAILPACK_NODE_VERSION=');
+});

tests/Feature/DevelopmentRailpackExamplesSeederTest.php

@@ -0,0 +1,121 @@
+<?php
+
+use App\Models\Application;
+use App\Models\GithubApp;
+use App\Models\PrivateKey;
+use App\Models\Project;
+use App\Models\Server;
+use App\Models\StandaloneDocker;
+use App\Models\Team;
+use Database\Seeders\DevelopmentRailpackExamplesSeeder;
+use Database\Seeders\GithubAppSeeder;
+use Database\Seeders\PrivateKeySeeder;
+use Database\Seeders\ProjectSeeder;
+use Database\Seeders\ServerSeeder;
+use Database\Seeders\StandaloneDockerSeeder;
+use Database\Seeders\TeamSeeder;
+use Database\Seeders\UserSeeder;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+uses(RefreshDatabase::class);
+
+function seedRailpackExamplePrerequisites(): void
+{
+    test()->seed([
+        UserSeeder::class,
+        TeamSeeder::class,
+        PrivateKeySeeder::class,
+        ServerSeeder::class,
+        ProjectSeeder::class,
+        StandaloneDockerSeeder::class,
+        GithubAppSeeder::class,
+    ]);
+}
+
+it('can seed the railpack examples directly on a clean development database', function () {
+    config()->set('app.env', 'local');
+
+    $this->seed(DevelopmentRailpackExamplesSeeder::class);
+
+    expect(Team::query()->find(0))->not->toBeNull();
+    expect(PrivateKey::query()->find(1))->not->toBeNull();
+    expect(Server::query()->find(0))->not->toBeNull();
+    expect(StandaloneDocker::query()->find(0))->not->toBeNull();
+    expect(GithubApp::query()->find(0))->not->toBeNull();
+    expect(Project::query()->where('uuid', DevelopmentRailpackExamplesSeeder::PROJECT_UUID)->exists())->toBeTrue();
+    expect(Application::query()->count())->toBe(count(DevelopmentRailpackExamplesSeeder::examples()));
+});
+
+it('seeds the railpack examples in development mode', function () {
+    config()->set('app.env', 'local');
+
+    seedRailpackExamplePrerequisites();
+    $this->seed(DevelopmentRailpackExamplesSeeder::class);
+
+    $project = Project::query()
+        ->where('uuid', DevelopmentRailpackExamplesSeeder::PROJECT_UUID)
+        ->first();
+
+    expect($project)
+        ->not->toBeNull()
+        ->and($project->name)->toBe('Railpack Examples')
+        ->and($project->environments)->toHaveCount(1)
+        ->and($project->environments->first()->uuid)->toBe(DevelopmentRailpackExamplesSeeder::ENVIRONMENT_UUID);
+
+    $applications = $project->applications()->with('settings')->orderBy('uuid')->get();
+
+    expect($applications)->toHaveCount(count(DevelopmentRailpackExamplesSeeder::examples()));
+    expect($applications->every(fn (Application $application) => $application->build_pack === 'railpack'))->toBeTrue();
+    expect($applications->every(fn (Application $application) => $application->git_repository === DevelopmentRailpackExamplesSeeder::GIT_REPOSITORY))->toBeTrue();
+    expect($applications->every(fn (Application $application) => $application->git_branch === DevelopmentRailpackExamplesSeeder::GIT_BRANCH))->toBeTrue();
+
+    $nestjs = $applications->firstWhere('uuid', 'railpack-nestjs');
+    $angularStatic = $applications->firstWhere('uuid', 'railpack-angular-static');
+    $eleventyStatic = $applications->firstWhere('uuid', 'railpack-eleventy-static');
+
+    expect($nestjs)
+        ->not->toBeNull()
+        ->and($nestjs->base_directory)->toBe('/node/nestjs')
+        ->and($nestjs->ports_exposes)->toBe('3000')
+        ->and($nestjs->build_command)->toBe('npm run build')
+        ->and($nestjs->start_command)->toBe('npm run start:prod')
+        ->and($nestjs->settings->is_static)->toBeFalse();
+
+    expect($angularStatic)
+        ->not->toBeNull()
+        ->and($angularStatic->publish_directory)->toBe('/dist/static/browser')
+        ->and($angularStatic->ports_exposes)->toBe('80')
+        ->and($angularStatic->settings->is_static)->toBeTrue()
+        ->and($angularStatic->settings->is_spa)->toBeTrue();
+
+    expect($eleventyStatic)
+        ->not->toBeNull()
+        ->and($eleventyStatic->publish_directory)->toBe('/_site')
+        ->and($eleventyStatic->settings->is_static)->toBeTrue()
+        ->and($eleventyStatic->settings->is_spa)->toBeFalse();
+});
+
+it('skips the railpack examples outside development mode', function () {
+    config()->set('app.env', 'testing');
+
+    seedRailpackExamplePrerequisites();
+    $this->seed(DevelopmentRailpackExamplesSeeder::class);
+
+    expect(Project::query()->where('uuid', DevelopmentRailpackExamplesSeeder::PROJECT_UUID)->exists())->toBeFalse();
+    expect(Application::query()->where('uuid', 'railpack-nextjs-ssr')->exists())->toBeFalse();
+});
+
+it('is idempotent when run multiple times', function () {
+    config()->set('app.env', 'local');
+
+    seedRailpackExamplePrerequisites();
+    $this->seed(DevelopmentRailpackExamplesSeeder::class);
+    $this->seed(DevelopmentRailpackExamplesSeeder::class);
+
+    $project = Project::query()
+        ->where('uuid', DevelopmentRailpackExamplesSeeder::PROJECT_UUID)
+        ->first();
+
+    expect($project)->not->toBeNull();
+    expect($project->applications()->count())->toBe(count(DevelopmentRailpackExamplesSeeder::examples()));
+});

tests/Unit/ApplicationDeploymentRailpackConfigTest.php

@@ -30,6 +30,9 @@ function makeRailpackDeploymentJob(array $applicationAttributes = [], array $sav
         'deployment_uuid' => 'deployment-uuid',
         'saved_outputs' => new Collection($savedOutputs),
         'env_railpack_args' => "--env 'RAILPACK_NODE_VERSION=22'",
+        'force_rebuild' => false,
+        'addHosts' => '',
+        'secrets_hash_key' => 'testing-app-key',
     ] as $property => $value) {
         $reflectionProperty = $reflection->getProperty($property);
         $reflectionProperty->setAccessible(true);
@@ -175,6 +178,9 @@ it('builds railpack prepare command using railpack env for install and cli flags
             'start_command' => 'node server.js',
         ],
     );
+    $envRailpackArgsProperty = $reflection->getProperty('env_railpack_args');
+    $envRailpackArgsProperty->setAccessible(true);
+    $envRailpackArgsProperty->setValue($job, "--env 'RAILPACK_NODE_VERSION=22' --env 'RAILPACK_INSTALL_CMD=npm ci'");
 
     $command = invokeRailpackMethod(
         $job,
@@ -184,8 +190,8 @@ it('builds railpack prepare command using railpack env for install and cli flags
     );
 
     expect($command)->toContain('railpack prepare');
-    expect($command)->toContain('--env '.escapeshellarg('RAILPACK_INSTALL_CMD=npm ci'));
     expect($command)->toContain("--env 'RAILPACK_NODE_VERSION=22'");
+    expect($command)->toContain("--env 'RAILPACK_INSTALL_CMD=npm ci'");
     expect($command)->toContain('--build-cmd '.escapeshellarg('npm run build'));
     expect($command)->toContain('--start-cmd '.escapeshellarg('node server.js'));
     expect($command)->toContain('--config-file '.escapeshellarg('.coolify/railpack.generated.json'));
@@ -195,3 +201,32 @@ it('builds railpack prepare command using railpack env for install and cli flags
     expect($command)->not->toContain('RAILPACK_BUILD_CMD=');
     expect($command)->not->toContain('RAILPACK_START_CMD=');
 });
+
+it('builds railpack docker command with matching env and secret flags for all railpack variables', function () {
+    [$job, $reflection] = makeRailpackDeploymentJob([
+        'uuid' => 'application-uuid',
+    ]);
+
+    $command = invokeRailpackMethod(
+        $job,
+        $reflection,
+        'railpack_build_command',
+        [
+            'coollabsio/coolify:test',
+            collect([
+                'RAILPACK_NODE_VERSION' => '22',
+                'RAILPACK_INSTALL_CMD' => 'npm ci && npm run postinstall',
+                'SECRET_JSON' => '{"token":"abc"}',
+            ]),
+        ],
+    );
+
+    expect($command)->toContain("env RAILPACK_NODE_VERSION='22'");
+    expect($command)->toContain("RAILPACK_INSTALL_CMD='npm ci && npm run postinstall'");
+    expect($command)->toContain("SECRET_JSON='{\"token\":\"abc\"}'");
+    expect($command)->toContain('--secret id=RAILPACK_NODE_VERSION,env=RAILPACK_NODE_VERSION');
+    expect($command)->toContain('--secret id=RAILPACK_INSTALL_CMD,env=RAILPACK_INSTALL_CMD');
+    expect($command)->toContain('--secret id=SECRET_JSON,env=SECRET_JSON');
+    expect($command)->toContain(' --build-arg secrets-hash=');
+    expect($command)->toContain('--build-arg BUILDKIT_SYNTAX="${RAILPACK_FRONTEND_IMAGE}"');
+});

tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php

@@ -0,0 +1,124 @@
+<?php
+
+use App\Jobs\ApplicationDeploymentJob;
+use App\Models\Application;
+use App\Models\EnvironmentVariable;
+use App\Models\Server;
+
+it('generates escaped railpack env args from resolved values and includes install command', function () {
+    $application = Mockery::mock(Application::class);
+    $application->shouldReceive('getAttribute')->with('install_command')->andReturn('npm ci && npm run postinstall');
+
+    $nodeVersion = Mockery::mock(EnvironmentVariable::class)->makePartial();
+    $nodeVersion->forceFill([
+        'key' => 'RAILPACK_NODE_VERSION',
+        'is_literal' => false,
+        'is_multiline' => false,
+    ]);
+    $nodeVersion->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn('22');
+
+    $literalValue = Mockery::mock(EnvironmentVariable::class)->makePartial();
+    $literalValue->forceFill([
+        'key' => 'RAILPACK_CUSTOM_FLAG',
+        'is_literal' => true,
+        'is_multiline' => false,
+    ]);
+    $literalValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn("'hello world'");
+
+    $jsonValue = Mockery::mock(EnvironmentVariable::class)->makePartial();
+    $jsonValue->forceFill([
+        'key' => 'RAILPACK_JSON',
+        'is_literal' => false,
+        'is_multiline' => false,
+    ]);
+    $jsonValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn('{"token":"abc"}');
+
+    $nullValue = Mockery::mock(EnvironmentVariable::class)->makePartial();
+    $nullValue->forceFill([
+        'key' => 'RAILPACK_NULL',
+        'is_literal' => false,
+        'is_multiline' => false,
+    ]);
+    $nullValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn(null);
+
+    $application->shouldReceive('getAttribute')
+        ->with('railpack_environment_variables')
+        ->andReturn(collect([$nodeVersion, $literalValue, $jsonValue, $nullValue]));
+
+    $job = Mockery::mock(ApplicationDeploymentJob::class)->makePartial();
+    $job->shouldAllowMockingProtectedMethods();
+
+    $reflection = new ReflectionClass(ApplicationDeploymentJob::class);
+    $applicationProperty = $reflection->getProperty('application');
+    $applicationProperty->setAccessible(true);
+    $applicationProperty->setValue($job, $application);
+
+    $pullRequestProperty = $reflection->getProperty('pull_request_id');
+    $pullRequestProperty->setAccessible(true);
+    $pullRequestProperty->setValue($job, 0);
+
+    $mainServerProperty = $reflection->getProperty('mainServer');
+    $mainServerProperty->setAccessible(true);
+    $mainServerProperty->setValue($job, Mockery::mock(Server::class));
+
+    $method = $reflection->getMethod('generate_railpack_env_variables');
+    $method->setAccessible(true);
+    $variables = $method->invoke($job);
+
+    $envArgsProperty = $reflection->getProperty('env_railpack_args');
+    $envArgsProperty->setAccessible(true);
+    $envArgs = $envArgsProperty->getValue($job);
+
+    expect($variables->all())->toBe([
+        'RAILPACK_NODE_VERSION' => '22',
+        'RAILPACK_CUSTOM_FLAG' => 'hello world',
+        'RAILPACK_JSON' => '{"token":"abc"}',
+        'RAILPACK_INSTALL_CMD' => 'npm ci && npm run postinstall',
+    ]);
+    expect($envArgs)->toContain("--env 'RAILPACK_NODE_VERSION=22'");
+    expect($envArgs)->toContain("--env 'RAILPACK_CUSTOM_FLAG=hello world'");
+    expect($envArgs)->toContain("--env 'RAILPACK_JSON={\"token\":\"abc\"}'");
+    expect($envArgs)->toContain("--env 'RAILPACK_INSTALL_CMD=npm ci && npm run postinstall'");
+    expect($envArgs)->not->toContain('RAILPACK_NULL');
+});
+
+it('uses preview railpack environment variables for preview deployments', function () {
+    $application = Mockery::mock(Application::class);
+    $application->shouldReceive('getAttribute')->with('install_command')->andReturn(null);
+
+    $previewValue = Mockery::mock(EnvironmentVariable::class)->makePartial();
+    $previewValue->forceFill([
+        'key' => 'RAILPACK_PREVIEW_ONLY',
+        'is_literal' => false,
+        'is_multiline' => false,
+    ]);
+    $previewValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn('preview-value');
+
+    $application->shouldReceive('getAttribute')
+        ->with('railpack_environment_variables_preview')
+        ->andReturn(collect([$previewValue]));
+
+    $job = Mockery::mock(ApplicationDeploymentJob::class)->makePartial();
+    $job->shouldAllowMockingProtectedMethods();
+
+    $reflection = new ReflectionClass(ApplicationDeploymentJob::class);
+    $applicationProperty = $reflection->getProperty('application');
+    $applicationProperty->setAccessible(true);
+    $applicationProperty->setValue($job, $application);
+
+    $pullRequestProperty = $reflection->getProperty('pull_request_id');
+    $pullRequestProperty->setAccessible(true);
+    $pullRequestProperty->setValue($job, 42);
+
+    $mainServerProperty = $reflection->getProperty('mainServer');
+    $mainServerProperty->setAccessible(true);
+    $mainServerProperty->setValue($job, Mockery::mock(Server::class));
+
+    $method = $reflection->getMethod('generate_railpack_env_variables');
+    $method->setAccessible(true);
+    $variables = $method->invoke($job);
+
+    expect($variables->all())->toBe([
+        'RAILPACK_PREVIEW_ONLY' => 'preview-value',
+    ]);
+});