diff --git a/app/Jobs/ApplicationDeploymentJob.php b/app/Jobs/ApplicationDeploymentJob.php
index 944f9b3bb5..70931ece2e 100644
--- a/app/Jobs/ApplicationDeploymentJob.php
+++ b/app/Jobs/ApplicationDeploymentJob.php
@@ -2018,6 +2018,14 @@ class ApplicationDeploymentJob implements ShouldBeEncrypted, ShouldQueue
                 $envs->push($this->runtimeEnvironmentAssignment($env));
             }
 
+            // A preview from before v4.5.1 also gets the production variables that have no preview copy.
+            if ($this->preview?->keeps_production_values && $runtime_environment_variables_preview->isNotEmpty()) {
+                $previewKeys = $runtime_environment_variables_preview->pluck('key')->all();
+                $sorted_environment_variables
+                    ->filter(fn (EnvironmentVariable $env) => $env->is_runtime && ! in_array($env->key, $previewKeys, true) && ! $this->shouldOmitBlankComposeEnvironmentVariable($env))
+                    ->each(fn (EnvironmentVariable $env) => $envs->push($this->runtimeEnvironmentAssignment($env)));
+            }
+
             // Add PORT if not exists, use the first port as default
             if ($this->build_pack !== 'dockercompose') {
                 if ($this->deployedPreviewVariables()->where('key', 'PORT')->isEmpty()) {
@@ -2619,7 +2627,7 @@ class ApplicationDeploymentJob implements ShouldBeEncrypted, ShouldQueue
             return $this->previewVariableIdsWithProductionValues;
         }
 
-        if ($this->pull_request_id === 0 || ! $this->application->settings->is_pr_deployments_public_enabled) {
+        if ($this->pull_request_id === 0 || ! $this->application->settings->is_pr_deployments_public_enabled || $this->preview?->keeps_production_values) {
             return $this->previewVariableIdsWithProductionValues = [];
         }
 
diff --git a/app/Models/ApplicationPreview.php b/app/Models/ApplicationPreview.php
index 22b1856814..2309fb128e 100644
--- a/app/Models/ApplicationPreview.php
+++ b/app/Models/ApplicationPreview.php
@@ -34,6 +34,7 @@ class ApplicationPreview extends BaseModel
         'last_online_at',
         'domain_dns_statuses',
         'domain_port_overrides',
+        'keeps_production_values',
     ];
 
     protected $hidden = [
@@ -44,6 +45,7 @@ class ApplicationPreview extends BaseModel
         'pull_request_id' => 'integer',
         'domain_dns_statuses' => 'array',
         'domain_port_overrides' => 'array',
+        'keeps_production_values' => 'boolean',
     ];
 
     protected static function booted(): void
diff --git a/app/Services/ServerTransfer/ServerTransferExporter.php b/app/Services/ServerTransfer/ServerTransferExporter.php
index 66254ae647..20957defe6 100644
--- a/app/Services/ServerTransfer/ServerTransferExporter.php
+++ b/app/Services/ServerTransfer/ServerTransferExporter.php
@@ -1644,6 +1644,7 @@ class ServerTransferExporter
                 'docker_registry_image_tag' => $preview->docker_registry_image_tag,
                 'domain_port_overrides' => $preview->domain_port_overrides,
                 'max_restart_count' => $preview->max_restart_count,
+                'keeps_production_values' => $preview->keeps_production_values,
                 'persistent_storages' => method_exists($preview, 'persistentStorages')
                     ? $this->exportPersistentStorages($preview->persistentStorages)
                     : [],
diff --git a/app/Services/ServerTransfer/ServerTransferImporter.php b/app/Services/ServerTransfer/ServerTransferImporter.php
index 7362160471..1cc4aed13e 100644
--- a/app/Services/ServerTransfer/ServerTransferImporter.php
+++ b/app/Services/ServerTransfer/ServerTransferImporter.php
@@ -2333,6 +2333,7 @@ class ServerTransferImporter
                 'docker_registry_image_tag' => data_get($previewPayload, 'docker_registry_image_tag'),
                 'domain_port_overrides' => data_get($previewPayload, 'domain_port_overrides'),
                 'max_restart_count' => (int) data_get($previewPayload, 'max_restart_count', 0),
+                'keeps_production_values' => (bool) data_get($previewPayload, 'keeps_production_values', false),
             ];
 
             if ($preview) {
diff --git a/bootstrap/helpers/parsers.php b/bootstrap/helpers/parsers.php
index 041e56ff0a..7aa5ef279e 100644
--- a/bootstrap/helpers/parsers.php
+++ b/bootstrap/helpers/parsers.php
@@ -1150,8 +1150,11 @@ function applicationParser(Application $resource, int $pull_request_id = 0, ?int
 
     $pullRequestId = $pull_request_id;
     $isPullRequest = $pullRequestId == 0 ? false : true;
-    // A public preview can run the compose file of a fork pull request.
-    $isPublicPullRequest = $isPullRequest && (bool) data_get($resource, 'settings.is_pr_deployments_public_enabled');
+    $pullRequestPreview = $isPullRequest
+        ? ($resource->previews()->find($preview_id) ?? ApplicationPreview::where('application_id', $resource->id)->where('pull_request_id', $pullRequestId)->first())
+        : null;
+    // A public preview can run the compose file of a fork pull request. A preview from before v4.5.1 keeps the production values.
+    $isPublicPullRequest = $isPullRequest && (bool) data_get($resource, 'settings.is_pr_deployments_public_enabled') && ! $pullRequestPreview?->keeps_production_values;
     $server = data_get($resource, 'destination.server');
     try {
         $yaml = parseDockerComposeYaml($compose);
diff --git a/database/migrations/2026_10_28_103619_add_keeps_production_values_to_application_previews_table.php b/database/migrations/2026_10_28_103619_add_keeps_production_values_to_application_previews_table.php
new file mode 100644
index 0000000000..3b187d1502
--- /dev/null
+++ b/database/migrations/2026_10_28_103619_add_keeps_production_values_to_application_previews_table.php
@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Until v4.5.1, previews used production values: the production variables that had no preview copy,
+     * and on public pull requests also the preview copies with the production value. Existing previews
+     * keep them, so their databases and services keep working. Previews created later do not get them.
+     */
+    public function up(): void
+    {
+        Schema::table('application_previews', function (Blueprint $table) {
+            $table->boolean('keeps_production_values')->default(false);
+        });
+
+        DB::table('application_previews')->update(['keeps_production_values' => true]);
+    }
+
+    public function down(): void
+    {
+        Schema::table('application_previews', function (Blueprint $table) {
+            $table->dropColumn('keeps_production_values');
+        });
+    }
+};
diff --git a/docs/server-transfer-full-coverage.md b/docs/server-transfer-full-coverage.md
index 25a7835e03..3391120322 100644
--- a/docs/server-transfer-full-coverage.md
+++ b/docs/server-transfer-full-coverage.md
@@ -103,7 +103,7 @@ When you add a model or a setting to the transfer, add it to this file too.
 | ✅ | Volume backup | on the persistent volume: S3 on, stop during backup, all retention values, timeout, missing-backup days |
 | ✅ | Scheduled tasks | the seed has one; add a disabled one with container + timeout |
 | ✅ | Tag | |
-| ✅ | Preview deployment | PR preview with domain port overrides + max restart count (needs the GitHub App, or create it in the database) |
+| ✅ | Preview deployment | PR preview with domain port overrides + max restart count + keeps production values (previews from before v4.5.1) (needs the GitHub App, or create it in the database) |
 | ✅ | Secret manager link | the app loads variables from the secret manager token |
 | ✅ | Managed DNS record | owned record in the Cloudflare zone for the app domain. Expected: the target takes ownership (provider comment changes) |
 
diff --git a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
index caf92c69e4..4abe239679 100644
--- a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
+++ b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
@@ -2050,3 +2050,29 @@ it('does not warn about a PORT mismatch when readonly labels are disabled', func
 
     expect(collect($job->recordedLogEntries)->contains(fn (string $entry) => str_contains($entry, 'PORT environment variable')))->toBeFalse();
 });
+
+it('gives a preview from before v4.5.1 the production values it had', function () {
+    [$application, $server] = makeDeploymentControlVarFixture();
+    $application->settings()->update(['is_pr_deployments_public_enabled' => true]);
+
+    createApplicationEnvironmentVariable($application, ['key' => 'DB_PASSWORD', 'value' => 'production-secret', 'is_buildtime' => false]);
+    createApplicationEnvironmentVariable($application, ['key' => 'APP_NAME', 'value' => 'coolify', 'is_buildtime' => false]);
+    $application->environment_variables_preview()->where('key', 'APP_NAME')->delete();
+
+    [$job, $reflection] = makeControlVarFilteringJob($application->fresh(), $server, [
+        'pull_request_id' => 99,
+        'remote_secrets_cache' => [],
+        'preview' => ApplicationPreview::create([
+            'application_id' => $application->id,
+            'pull_request_id' => 99,
+            'pull_request_html_url' => 'https://example.com/pr/99',
+            'keeps_production_values' => true,
+        ]),
+    ]);
+
+    /** @var Collection $runtimeEnvs */
+    $runtimeEnvs = invokeDeploymentJobMethod($job, $reflection, 'generate_runtime_environment_variables');
+
+    expect($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('DB_PASSWORD=') && str($env)->contains('production-secret')))->toBeTrue()
+        ->and($runtimeEnvs->contains(fn (string $env) => str($env)->startsWith('APP_NAME=') && str($env)->contains('coolify')))->toBeTrue();
+});
diff --git a/tests/Feature/ComposePreviewMagicVariablesTest.php b/tests/Feature/ComposePreviewMagicVariablesTest.php
index fcdf777695..d7c393c011 100644
--- a/tests/Feature/ComposePreviewMagicVariablesTest.php
+++ b/tests/Feature/ComposePreviewMagicVariablesTest.php
@@ -215,3 +215,24 @@ it('replaces an existing preview copy of a production magic value for a public p
         ->not->toBeEmpty()
         ->not->toBe($production['SERVICE_PASSWORD_DB']);
 });
+
+it('keeps the production magic value of a public pull request preview from before v4.5.1', function () {
+    composePreviewMagicParse($this->application);
+    $production = composePreviewMagicValues($this->application)['production'];
+    $this->application->environment_variables_preview()->create([
+        'key' => 'SERVICE_PASSWORD_DB',
+        'value' => $production['SERVICE_PASSWORD_DB'],
+        'is_preview' => true,
+    ]);
+    ApplicationPreview::query()->create([
+        'application_id' => $this->application->id,
+        'pull_request_id' => 7,
+        'pull_request_html_url' => 'https://github.com/example/repository/pull/7',
+        'keeps_production_values' => true,
+    ]);
+    $this->application->settings->update(['is_pr_deployments_public_enabled' => true]);
+
+    composePreviewMagicParse($this->application, 7);
+
+    expect(composePreviewMagicValues($this->application)['preview']['SERVICE_PASSWORD_DB'])->toBe($production['SERVICE_PASSWORD_DB']);
+});
diff --git a/tests/Unit/ServerTransfer/ServerTransferExporterImporterTest.php b/tests/Unit/ServerTransfer/ServerTransferExporterImporterTest.php
index 63f416eb6b..c5a55af722 100644
--- a/tests/Unit/ServerTransfer/ServerTransferExporterImporterTest.php
+++ b/tests/Unit/ServerTransfer/ServerTransferExporterImporterTest.php
@@ -859,6 +859,7 @@ test('service nested apps dbs volumes backups and db file storages round-trip',
         'fqdn' => 'https://pr-42.app.example.com',
         'status' => 'running:healthy',
         'git_type' => 'github',
+        'keeps_production_values' => true,
     ]);
     $preview->uuid = 'preview-pr-42';
     $preview->save();
@@ -969,6 +970,7 @@ test('service nested apps dbs volumes backups and db file storages round-trip',
     expect($importedApp)->not->toBeNull()
         ->and($importedApp->previews)->toHaveCount(1)
         ->and($importedApp->previews->first()->uuid)->toBe('preview-pr-42')
+        ->and($importedApp->previews->first()->keeps_production_values)->toBeTrue()
         ->and($importedApp->previews->first()->persistentStorages)->toHaveCount(1);
 
     $importedVolBackup = ScheduledVolumeBackup::where('uuid', 'svc-app-vol-backup')->first();