diff --git a/app/Jobs/ApplicationDeploymentJob.php b/app/Jobs/ApplicationDeploymentJob.php
index 420fe8fd4..6f9aabfd5 100644
--- a/app/Jobs/ApplicationDeploymentJob.php
+++ b/app/Jobs/ApplicationDeploymentJob.php
@@ -2483,15 +2483,6 @@ private function generate_railpack_env_variables(): Collection
         return $variables;
     }
 
-    private function railpack_environment_variables_collection(): Collection
-    {
-        if ($this->pull_request_id === 0) {
-            return $this->application->railpack_environment_variables;
-        }
-
-        return $this->application->railpack_environment_variables_preview;
-    }
-
     private function normalize_resolved_build_variable_value(EnvironmentVariable $environmentVariable): ?string
     {
         $resolvedValue = $environmentVariable->getResolvedValueWithServer($this->mainServer);
@@ -2506,9 +2497,23 @@ private function normalize_resolved_build_variable_value(EnvironmentVariable $en
         return $resolvedValue;
     }
 
+    /**
+     * All buildtime variables that must reach the Railpack build.
+     *
+     * Railpack's BuildKit frontend treats every `--env` passed to `railpack prepare`
+     * as a build secret entry in the generated plan, then pairs it with `--secret id=,env=`
+     * on `docker buildx build`. Because Railpack's schema disallows top-level `variables`
+     * (unlike Nixpacks, which bakes variables into the plan), this `--env` → `--secret`
+     * channel is the only way user-defined buildtime variables become available to
+     * commands declared with `useSecrets: true`.
+     */
     private function railpack_build_variables(): Collection
     {
-        $variables = $this->railpack_environment_variables_collection()
+        $envCollection = $this->pull_request_id === 0
+            ? $this->application->environment_variables()->where('is_buildtime', true)->get()
+            : $this->application->environment_variables_preview()->where('is_buildtime', true)->get();
+
+        $variables = $envCollection
             ->mapWithKeys(function (EnvironmentVariable $environmentVariable) {
                 $value = $this->normalize_resolved_build_variable_value($environmentVariable);
                 if (is_null($value) || $value === '') {
diff --git a/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php b/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
index 8ed7b2c41..487268fb6 100644
--- a/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
+++ b/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
@@ -41,9 +41,10 @@
     ]);
     $nullValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn(null);
 
-    $application->shouldReceive('getAttribute')
-        ->with('railpack_environment_variables')
-        ->andReturn(collect([$nodeVersion, $literalValue, $jsonValue, $nullValue]));
+    $envQuery = Mockery::mock();
+    $envQuery->shouldReceive('where')->with('is_buildtime', true)->once()->andReturnSelf();
+    $envQuery->shouldReceive('get')->once()->andReturn(collect([$nodeVersion, $literalValue, $jsonValue, $nullValue]));
+    $application->shouldReceive('environment_variables')->once()->andReturn($envQuery);
 
     $job = Mockery::mock(ApplicationDeploymentJob::class)->makePartial();
     $job->shouldAllowMockingProtectedMethods();
@@ -94,9 +95,10 @@
     ]);
     $previewValue->shouldReceive('getResolvedValueWithServer')->once()->with(Mockery::type(Server::class))->andReturn('preview-value');
 
-    $application->shouldReceive('getAttribute')
-        ->with('railpack_environment_variables_preview')
-        ->andReturn(collect([$previewValue]));
+    $previewQuery = Mockery::mock();
+    $previewQuery->shouldReceive('where')->with('is_buildtime', true)->once()->andReturnSelf();
+    $previewQuery->shouldReceive('get')->once()->andReturn(collect([$previewValue]));
+    $application->shouldReceive('environment_variables_preview')->once()->andReturn($previewQuery);
 
     $job = Mockery::mock(ApplicationDeploymentJob::class)->makePartial();
     $job->shouldAllowMockingProtectedMethods();