diff --git a/app/Actions/Application/CleanupCancelledDeployment.php b/app/Actions/Application/CleanupCancelledDeployment.php
index 171e660e66..5da94db3cb 100644
--- a/app/Actions/Application/CleanupCancelledDeployment.php
+++ b/app/Actions/Application/CleanupCancelledDeployment.php
@@ -28,6 +28,12 @@ class CleanupCancelledDeployment
                     if (str($containerExists)->trim()->isNotEmpty()) {
                         instant_remote_process(["docker rm -f {$deploymentUuid}"], $server);
                         $containerStopped = true;
+
+                        // A removed helper cannot stop the Railpack builder, which keeps the memory of its builds.
+                        if ($deployment->application?->build_pack === 'railpack') {
+                            $helperImage = coolifyHelperImage().':'.getHelperVersion();
+                            instant_remote_process([railpackBuilderHelperCommand(railpackBuildxMetadataVolume($server), $helperImage, 'true')], $server, false);
+                        }
                     }
                 } catch (\Throwable $e) {
                     $firstError ??= $e;
diff --git a/app/Actions/Server/CleanupDocker.php b/app/Actions/Server/CleanupDocker.php
index 201f86b367..3c0e2ba7e0 100644
--- a/app/Actions/Server/CleanupDocker.php
+++ b/app/Actions/Server/CleanupDocker.php
@@ -135,9 +135,6 @@ class CleanupDocker implements ShouldBeUnique
         $helperImageWithVersion = "$helperImage:$helperImageVersion";
         $helperImageWithoutPrefix = 'coollabsio/coolify-helper';
         $helperImageWithoutPrefixVersion = "coollabsio/coolify-helper:$helperImageVersion";
-        $buildxMetadataVolume = isDev() && $server->isLocalhost()
-            ? 'coolify-buildx'
-            : '$HOME/.docker/buildx';
 
         $cleanupLog = [];
 
@@ -164,7 +161,8 @@ class CleanupDocker implements ShouldBeUnique
             'docker container prune -f --filter "label=coolify.managed=true" --filter "label!=coolify.proxy=true" --filter "label!=coolify.type=database" --filter "label!=coolify.type=application" --filter "label!=coolify.type=service"',
             $imagePruneCmd,
             'docker builder prune -af',
-            "docker run --rm -v {$buildxMetadataVolume}:/root/.docker/buildx -v /var/run/docker.sock:/var/run/docker.sock {$helperImageWithVersion} docker buildx prune --builder coolify-railpack -af 2>/dev/null || true",
+            // The prune fails on a stopped builder, so start it first.
+            railpackBuilderHelperCommand(railpackBuildxMetadataVolume($server), $helperImageWithVersion, 'docker buildx inspect --bootstrap coolify-railpack >/dev/null 2>&1; docker buildx prune --builder coolify-railpack -af'),
             "docker images --filter before=$helperImageWithVersion --filter reference=$helperImage | grep $helperImage | awk '{print $3}' | xargs -r docker rmi -f",
             "docker images --filter before=$helperImageWithoutPrefixVersion --filter reference=$helperImageWithoutPrefix | grep $helperImageWithoutPrefix | awk '{print $3}' | xargs -r docker rmi -f",
         ];
diff --git a/app/Jobs/ApplicationDeploymentJob.php b/app/Jobs/ApplicationDeploymentJob.php
index 07f77318a4..c822d35866 100644
--- a/app/Jobs/ApplicationDeploymentJob.php
+++ b/app/Jobs/ApplicationDeploymentJob.php
@@ -3350,12 +3350,20 @@ class ApplicationDeploymentJob implements ShouldBeEncrypted, ShouldQueue
         return $variables;
     }
 
+    /**
+     * Without the `...` entry, the list replaces the packages that Railpack generates
+     * (for example libatomic1, which Node.js 25+ needs at runtime).
+     */
     private function merge_railpack_deploy_apt_packages(Collection $variables): Collection
     {
         $packages = collect(preg_split('/\s+/', trim((string) $variables->get('RAILPACK_DEPLOY_APT_PACKAGES', ''))) ?: [])
             ->filter()
             ->values();
 
+        if (! $packages->contains('...')) {
+            $packages->prepend('...');
+        }
+
         foreach (['curl', 'wget'] as $package) {
             if (! $packages->contains($package)) {
                 $packages->push($package);
@@ -3439,7 +3447,7 @@ class ApplicationDeploymentJob implements ShouldBeEncrypted, ShouldQueue
             ." {$this->workdir}";
 
         return 'DOCKER_CONFIG=/root/.docker docker buildx create --name coolify-railpack --driver docker-container 2>/dev/null || true'
-            .' && '.$this->wrap_build_command_with_env_export($buildxBuildCommand);
+            ."\n".railpackBuilderLockedScript('('.$this->wrap_build_command_with_env_export($buildxBuildCommand).')');
     }
 
     private function decode_railpack_config(string $config, string $source): array
diff --git a/bootstrap/helpers/docker.php b/bootstrap/helpers/docker.php
index 059f55e333..2c1025b623 100644
--- a/bootstrap/helpers/docker.php
+++ b/bootstrap/helpers/docker.php
@@ -2109,3 +2109,37 @@ function injectDockerComposeBuildArgs(string $command, string $buildArgsString):
 
     return $modifiedCommand ?? $command;
 }
+
+/**
+ * Run a command that uses the Railpack BuildKit builder, then stop the builder when no other
+ * process uses it. An idle buildkitd keeps the memory of earlier builds until it restarts.
+ *
+ * The lock file is in the buildx metadata directory, which all helper containers of a server share.
+ * The script has no `&&`, `||`, pipe, or `$(`, because the sudo parser would put sudo into it.
+ */
+function railpackBuilderLockedScript(string $command): string
+{
+    return 'exec 9>/root/.docker/buildx/coolify-railpack.lock; if flock -s 9; then :; else exit $?; fi; '
+        ."{$command}; status=\$?; "
+        .'if flock -n -x 9; then DOCKER_CONFIG=/root/.docker docker buildx stop coolify-railpack >/dev/null 2>&1; fi; '
+        .'exit $status';
+}
+
+/**
+ * The buildx metadata of a server, as the `docker run -v` source that the deployment helper uses.
+ */
+function railpackBuildxMetadataVolume(Server $server): string
+{
+    return isDev() && $server->isLocalhost() ? 'coolify-buildx' : '$HOME/.docker/buildx';
+}
+
+/**
+ * Run a command for the Railpack builder from a temporary helper container, then stop the builder
+ * when no build uses it.
+ */
+function railpackBuilderHelperCommand(string $buildxMetadataVolume, string $helperImage, string $command): string
+{
+    $script = railpackBuilderLockedScript($command);
+
+    return "docker run --rm -v {$buildxMetadataVolume}:/root/.docker/buildx -v /var/run/docker.sock:/var/run/docker.sock {$helperImage} bash -c '{$script}' 2>/dev/null || true";
+}
diff --git a/config/constants.php b/config/constants.php
index e792499c35..657d393ab6 100644
--- a/config/constants.php
+++ b/config/constants.php
@@ -6,8 +6,8 @@ $sshCommandTimeout = (int) env('SSH_COMMAND_TIMEOUT', 3600);
 return [
     'coolify' => [
         'version' => env('COOLIFY_VERSION') ?: '4.4.2',
-        'helper_version' => '1.0.17',
-        'railpack_version' => '0.23.0',
+        'helper_version' => '1.0.18',
+        'railpack_version' => '0.40.1',
         'self_hosted' => env('SELF_HOSTED', true),
         'autoupdate' => env('AUTOUPDATE'),
         'base_config_path' => env('BASE_CONFIG_PATH', '/data/coolify'),
diff --git a/docker/coolify-helper/Dockerfile b/docker/coolify-helper/Dockerfile
index 1fe99f01c2..b3c068f437 100644
--- a/docker/coolify-helper/Dockerfile
+++ b/docker/coolify-helper/Dockerfile
@@ -12,9 +12,9 @@ ARG PACK_VERSION=0.38.2
 # https://github.com/railwayapp/nixpacks/releases
 ARG NIXPACKS_VERSION=1.41.0
 # https://github.com/railwayapp/railpack/releases
-ARG RAILPACK_VERSION=0.23.0
-# https://github.com/jdx/mise/releases — must match railpack's pinned version (https://raw.githubusercontent.com/railwayapp/railpack/refs/heads/main/core/mise/version.txt)
-ARG MISE_VERSION=2026.3.17
+ARG RAILPACK_VERSION=0.40.1
+# https://github.com/jdx/mise/releases — must match the version pinned at that railpack tag (https://raw.githubusercontent.com/railwayapp/railpack/v${RAILPACK_VERSION}/core/mise/version.txt)
+ARG MISE_VERSION=2026.9.15
 FROM quay.io/minio/aistor/mc:RELEASE.2026-09-06T02-44-40Z AS minio-client
 
 FROM ${BASE_IMAGE} AS base
@@ -36,7 +36,7 @@ RUN apk upgrade --no-cache && \
 RUN mkdir -p ~/.docker/cli-plugins
 
 # Install mise (musl build) at the path railpack expects (/tmp/railpack/mise/mise-VERSION).
-# Railpack hardcodes a glibc mise download that fails on Alpine, so we pre-place a musl binary.
+# Railpack skips its own mise download when this file exists.
 RUN mkdir -p /tmp/railpack/mise && \
     if [[ ${TARGETPLATFORM} == 'linux/amd64' ]]; then \
         curl -sSL "https://github.com/jdx/mise/releases/download/v${MISE_VERSION}/mise-v${MISE_VERSION}-linux-x64-musl.tar.gz" | tar xz && \
diff --git a/other/nightly/versions.json b/other/nightly/versions.json
index a1f7ec3a90..3f4323c7ea 100644
--- a/other/nightly/versions.json
+++ b/other/nightly/versions.json
@@ -7,7 +7,7 @@
             "version": "4.5-rc.1"
         },
         "helper": {
-            "version": "1.0.17"
+            "version": "1.0.18"
         },
         "sentinel": {
             "version": "1.0.2"
diff --git a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
index 076bbae527..6706bcda87 100644
--- a/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
+++ b/tests/Feature/ApplicationDeploymentControlVarFilteringTest.php
@@ -1372,7 +1372,7 @@ it('builds railpack variables from generic buildtime vars railpack vars and cool
     expect($variables->get('APP_ENV'))->toBe('production');
     expect($variables->get('RAILPACK_NODE_VERSION'))->toBe('20');
     expect($variables->get('RAILPACK_INSTALL_CMD'))->toBe('pnpm install --frozen-lockfile');
-    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('curl wget');
+    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('... curl wget');
     expect($variables->get('COOLIFY_RESOURCE_UUID'))->toBe($application->uuid);
     expect($variables->has('NIXPACKS_NODE_VERSION'))->toBeFalse();
     expect($variables->has('RUNTIME_ONLY'))->toBeFalse();
@@ -1424,7 +1424,7 @@ it('builds preview railpack variables without leaking stale nixpacks vars', func
 
     expect($variables->get('PREVIEW_BUILD_FLAG'))->toBe('enabled');
     expect($variables->get('RAILPACK_NODE_VERSION'))->toBe('20');
-    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('curl wget');
+    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('... curl wget');
     expect($variables->get('COOLIFY_RESOURCE_UUID'))->toBe($application->uuid);
     expect($variables->has('NIXPACKS_NODE_VERSION'))->toBeFalse();
     expect($variables->has('PREVIEW_RUNTIME_ONLY'))->toBeFalse();
diff --git a/tests/Feature/DeploymentCancellationCleanupTest.php b/tests/Feature/DeploymentCancellationCleanupTest.php
index 6912ae604a..0721fbc4d2 100644
--- a/tests/Feature/DeploymentCancellationCleanupTest.php
+++ b/tests/Feature/DeploymentCancellationCleanupTest.php
@@ -179,3 +179,16 @@ test('cancelling after switching to another team still cleans up and starts the
     assertCancelCleanupRanCorrectly($this->remoteCommands, $this->deployment);
     expect($queued->fresh()->status)->toBe(ApplicationDeploymentStatus::IN_PROGRESS->value);
 });
+
+test('cancelling a Railpack deployment stops the idle Railpack builder on the build server', function (string $buildPack, bool $stopsBuilder) {
+    $this->application->update(['build_pack' => $buildPack]);
+    $this->actingAs($this->user);
+
+    Livewire::test(DeploymentNavbar::class, ['application_deployment_queue' => $this->deployment])
+        ->call('cancel');
+
+    expect(cancelCleanupCommandsOn($this->remoteCommands, '203.0.113.20', 'docker buildx stop coolify-railpack') !== [])->toBe($stopsBuilder);
+})->with([
+    'railpack' => ['railpack', true],
+    'nixpacks' => ['nixpacks', false],
+]);
diff --git a/tests/Unit/ApplicationDeploymentRailpackConfigTest.php b/tests/Unit/ApplicationDeploymentRailpackConfigTest.php
index 168e8be881..0ba3605888 100644
--- a/tests/Unit/ApplicationDeploymentRailpackConfigTest.php
+++ b/tests/Unit/ApplicationDeploymentRailpackConfigTest.php
@@ -260,6 +260,23 @@ it('pins docker config while running railpack buildx commands', function () {
         ->toContain('DOCKER_CONFIG=/root/.docker docker buildx build --builder coolify-railpack');
 });
 
+it('stops the railpack builder after the build when no other build uses it', function () {
+    [$job, $reflection] = makeRailpackDeploymentJob([
+        'uuid' => 'application-uuid',
+    ]);
+
+    $command = invokeRailpackMethod($job, $reflection, 'railpack_build_command', ['coollabsio/coolify:test', collect([])]);
+
+    $sharedLock = strpos($command, 'flock -s 9');
+    $build = strpos($command, 'docker buildx build --builder coolify-railpack');
+    $stop = strpos($command, 'if flock -n -x 9; then DOCKER_CONFIG=/root/.docker docker buildx stop coolify-railpack');
+
+    expect($sharedLock)->not->toBeFalse()
+        ->and($build)->toBeGreaterThan($sharedLock)
+        ->and($stop)->toBeGreaterThan($build)
+        ->and($command)->toEndWith('exit $status');
+});
+
 it('filters reserved docker client variables from railpack build secrets', function () {
     [$job, $reflection] = makeRailpackDeploymentJob([
         'uuid' => 'application-uuid',
diff --git a/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php b/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
index 1dda8b8c3e..0b7d5406c9 100644
--- a/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
+++ b/tests/Unit/ApplicationDeploymentRailpackEnvParityTest.php
@@ -81,13 +81,13 @@ it('generates escaped railpack env args from resolved values and includes instal
         'RAILPACK_CUSTOM_FLAG' => 'hello world',
         'RAILPACK_JSON' => '{"token":"abc"}',
         'RAILPACK_INSTALL_CMD' => 'npm ci && npm run postinstall',
-        'RAILPACK_DEPLOY_APT_PACKAGES' => 'curl wget',
+        'RAILPACK_DEPLOY_APT_PACKAGES' => '... curl wget',
     ]);
     expect($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)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=curl wget'");
+    expect($envArgs)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=... curl wget'");
     expect($envArgs)->not->toContain('RAILPACK_NULL');
 });
 
@@ -136,7 +136,7 @@ it('uses preview railpack environment variables for preview deployments', functi
 
     expect($variables->all())->toBe([
         'RAILPACK_PREVIEW_ONLY' => 'preview-value',
-        'RAILPACK_DEPLOY_APT_PACKAGES' => 'curl wget',
+        'RAILPACK_DEPLOY_APT_PACKAGES' => '... curl wget',
     ]);
 });
 
@@ -195,7 +195,7 @@ it('merges coolify env variables into railpack build variables', function () {
 
     expect($variables->all())->toBe([
         'MY_BUILD_VAR' => 'hello',
-        'RAILPACK_DEPLOY_APT_PACKAGES' => 'curl wget',
+        'RAILPACK_DEPLOY_APT_PACKAGES' => '... curl wget',
         'COOLIFY_URL' => 'https://app.example.com',
         'COOLIFY_FQDN' => 'app.example.com',
         'COOLIFY_BRANCH' => 'main',
@@ -209,7 +209,7 @@ it('merges coolify env variables into railpack build variables', function () {
 
     expect($envArgs)->toContain("--env 'COOLIFY_URL=https://app.example.com'");
     expect($envArgs)->toContain("--env 'SOURCE_COMMIT=abc123'");
-    expect($envArgs)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=curl wget'");
+    expect($envArgs)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=... curl wget'");
     expect($envArgs)->not->toContain('EMPTY_VAR');
     expect($envArgs)->not->toContain('NULL_VAR');
 });
@@ -257,11 +257,11 @@ it('preserves user railpack deploy apt packages while adding healthcheck tools o
     $method->setAccessible(true);
     $variables = $method->invoke($job);
 
-    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('ffmpeg curl wget');
+    expect($variables->get('RAILPACK_DEPLOY_APT_PACKAGES'))->toBe('... ffmpeg curl wget');
 
     $envArgsProperty = $reflection->getProperty('env_railpack_args');
     $envArgsProperty->setAccessible(true);
     $envArgs = $envArgsProperty->getValue($job);
 
-    expect($envArgs)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=ffmpeg curl wget'");
+    expect($envArgs)->toContain("--env 'RAILPACK_DEPLOY_APT_PACKAGES=... ffmpeg curl wget'");
 });
diff --git a/tests/Unit/ParseCommandsByLineForSudoTest.php b/tests/Unit/ParseCommandsByLineForSudoTest.php
index 594ecbd046..a0ef50d1ad 100644
--- a/tests/Unit/ParseCommandsByLineForSudoTest.php
+++ b/tests/Unit/ParseCommandsByLineForSudoTest.php
@@ -863,3 +863,17 @@ test('parseCommandsByLineForSudo keeps pipes inside quoted strings unchanged', f
 
     expect($result[0])->toBe("sudo docker ps --format '{{.Names}} | {{.Image}}' | sudo grep app");
 });
+
+test('railpack builder helper command gets sudo only outside the helper script', function () {
+    $command = railpackBuilderHelperCommand('$HOME/.docker/buildx', 'coolify-helper:1.0.0', 'docker buildx prune --builder coolify-railpack -af');
+
+    $parsed = parseCommandsByLineForSudo(collect([$command]), $this->server)[0];
+
+    // The SSH user's shell must expand $HOME, so the line must not be wrapped in `sudo bash -c`.
+    expect($parsed)->toBe(
+        'sudo docker run --rm -v $HOME/.docker/buildx:/root/.docker/buildx -v /var/run/docker.sock:/var/run/docker.sock coolify-helper:1.0.0'
+        ." bash -c 'exec 9>/root/.docker/buildx/coolify-railpack.lock; if flock -s 9; then :; else exit $?; fi; docker buildx prune --builder coolify-railpack -af; status=$?;"
+        .' if flock -n -x 9; then DOCKER_CONFIG=/root/.docker docker buildx stop coolify-railpack >/dev/null 2>&1; fi;'
+        ." exit \$status' 2>/dev/null || sudo true"
+    );
+});
diff --git a/tests/Unit/RailpackBuilderLockTest.php b/tests/Unit/RailpackBuilderLockTest.php
new file mode 100644
index 0000000000..273104d6c4
--- /dev/null
+++ b/tests/Unit/RailpackBuilderLockTest.php
@@ -0,0 +1,43 @@
+<?php
+
+use Symfony\Component\Process\Process;
+
+require_once __DIR__.'/../../bootstrap/helpers/docker.php';
+
+function runRailpackLockScript(string $command, string $setup = ''): Process
+{
+    $directory = sys_get_temp_dir().'/railpack-lock-'.bin2hex(random_bytes(8));
+    mkdir($directory);
+
+    try {
+        $script = str_replace('/root/.docker/buildx/coolify-railpack.lock', $directory.'/builder.lock', $setup.railpackBuilderLockedScript($command));
+        $process = new Process(['bash', '-c', $script]);
+        $process->run();
+
+        return $process;
+    } finally {
+        @unlink($directory.'/builder.lock');
+        rmdir($directory);
+    }
+}
+
+test('a failed shared lock prevents the builder command from running', function () {
+    $process = runRailpackLockScript('printf build-ran', 'flock() { return 73; }; ');
+
+    expect($process->getExitCode())->toBe(73);
+    expect($process->getOutput())->toBe('');
+});
+
+test('the builder stops after a failed command without hiding its exit status', function () {
+    $process = runRailpackLockScript('(exit 42)', 'exec 3>&1; docker() { printf stopped >&3; return 0; }; ');
+
+    expect($process->getExitCode())->toBe(42);
+    expect($process->getOutput())->toBe('stopped');
+});
+
+test('a held shared lock prevents stopping the builder', function () {
+    $process = runRailpackLockScript('printf built', 'exec 8>/root/.docker/buildx/coolify-railpack.lock; flock -s 8; docker() { exit 99; }; ');
+
+    expect($process->getExitCode())->toBe(0);
+    expect($process->getOutput())->toBe('built');
+});
diff --git a/versions.json b/versions.json
index a1f7ec3a90..3f4323c7ea 100644
--- a/versions.json
+++ b/versions.json
@@ -7,7 +7,7 @@
             "version": "4.5-rc.1"
         },
         "helper": {
-            "version": "1.0.17"
+            "version": "1.0.18"
         },
         "sentinel": {
             "version": "1.0.2"