diff --git a/src/Assets/JsAssetEntry.php b/src/Assets/JsAssetEntry.php
new file mode 100644
index 00000000..96c1aa93
--- /dev/null
+++ b/src/Assets/JsAssetEntry.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+/**
+ * A single resolved JavaScript asset: its filesystem path, public URI and
+ * the application it was resolved against.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+final class JsAssetEntry
+{
+    public function __construct(
+        public readonly string $fsPath,
+        public readonly string $uri,
+        public readonly ?string $app = null,
+    ) {}
+}
diff --git a/src/Assets/JsDiscoverer.php b/src/Assets/JsDiscoverer.php
index 3ed9f0ed..10d16d93 100644
--- a/src/Assets/JsDiscoverer.php
+++ b/src/Assets/JsDiscoverer.php
@@ -26,4 +26,11 @@ public function resolve(string $file, string $app = 'horde'): ?string;
 
     /** @return array<string, ?string> Map of file => uri (null if not found) */
     public function resolveMany(array $files, string $app = 'horde'): array;
+
+    /**
+     * Resolve theme-shipped JavaScript for a request.
+     *
+     * Implementations without theme knowledge return an empty result.
+     */
+    public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult;
 }
diff --git a/src/Assets/JsDiscoveryRequest.php b/src/Assets/JsDiscoveryRequest.php
new file mode 100644
index 00000000..77d377b9
--- /dev/null
+++ b/src/Assets/JsDiscoveryRequest.php
@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+/**
+ * Describes a theme-aware JavaScript discovery request.
+ *
+ * Parallel to {@see CssDiscoveryRequest}. When $files is empty the discoverer
+ * derives the file list from the theme's own declarations (info.php
+ * $theme_scripts).
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+final class JsDiscoveryRequest
+{
+    /** @param list<string> $files */
+    public function __construct(
+        public readonly array $files = [],
+        public readonly string $app = 'horde',
+        public readonly string $theme = 'default',
+    ) {}
+}
diff --git a/src/Assets/JsDiscoveryResult.php b/src/Assets/JsDiscoveryResult.php
new file mode 100644
index 00000000..9aee808f
--- /dev/null
+++ b/src/Assets/JsDiscoveryResult.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+use ArrayIterator;
+use Countable;
+use IteratorAggregate;
+
+/**
+ * The ordered set of JavaScript assets discovered for a theme.
+ *
+ * Parallel to {@see CssDiscoveryResult}.
+ *
+ * @implements IteratorAggregate<int, JsAssetEntry>
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+final class JsDiscoveryResult implements IteratorAggregate, Countable
+{
+    /** @param list<JsAssetEntry> $entries */
+    public function __construct(
+        private readonly array $entries,
+        private readonly string $theme,
+        private readonly string $app,
+    ) {}
+
+    /** @return ArrayIterator<int, JsAssetEntry> */
+    public function getIterator(): ArrayIterator
+    {
+        return new ArrayIterator($this->entries);
+    }
+
+    public function count(): int
+    {
+        return count($this->entries);
+    }
+
+    public function getTheme(): string
+    {
+        return $this->theme;
+    }
+
+    public function getApp(): string
+    {
+        return $this->app;
+    }
+
+    public function isEmpty(): bool
+    {
+        return $this->entries === [];
+    }
+
+    /** @return list<JsAssetEntry> */
+    public function toArray(): array
+    {
+        return $this->entries;
+    }
+}
diff --git a/src/Assets/PathBasedJsDiscoverer.php b/src/Assets/PathBasedJsDiscoverer.php
index c3af3dc0..39cf3fea 100644
--- a/src/Assets/PathBasedJsDiscoverer.php
+++ b/src/Assets/PathBasedJsDiscoverer.php
@@ -51,4 +51,11 @@ public function resolveMany(array $files, string $app = 'horde'): array
 
         return $result;
     }
+
+    public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+    {
+        /* This discoverer has no theme knowledge; theme scripts are handled
+         * by ThemeJsDiscoverer. */
+        return new JsDiscoveryResult([], $request->theme, $request->app);
+    }
 }
diff --git a/src/Assets/PhpThemeInfoReader.php b/src/Assets/PhpThemeInfoReader.php
new file mode 100644
index 00000000..7281be45
--- /dev/null
+++ b/src/Assets/PhpThemeInfoReader.php
@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+use Horde\Core\Path\PathBuilderInterface;
+
+/**
+ * Reads theme asset declarations from a theme's info.php on the local
+ * filesystem.
+ *
+ * Applies the same validation as the legacy Horde_Themes_Cache::themeScripts():
+ * theme names and script file names are constrained so a declaration can never
+ * escape the theme directory.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+class PhpThemeInfoReader implements ThemeInfoReader
+{
+    /**
+     * Plain directory name: no separators, no '..'. Theme names originate from
+     * user prefs/options, so this guards the info.php include against path
+     * traversal.
+     */
+    private const THEME_NAME = '/^[A-Za-z0-9_-]+$/';
+
+    /**
+     * Plain *.js file name. Combined with the explicit '..' check below this
+     * keeps a declared script inside the theme directory.
+     */
+    private const SCRIPT_NAME = '/^[A-Za-z0-9_.-]+\.js$/';
+
+    public function __construct(
+        private readonly PathBuilderInterface $pathBuilder,
+        private readonly AssetFilesystem $filesystem,
+    ) {}
+
+    public function readScripts(string $app, string $theme): array
+    {
+        if (!preg_match(self::THEME_NAME, $theme)) {
+            return [];
+        }
+
+        $scripts = [];
+        foreach ($this->declaredScripts($app, $theme) as $script) {
+            $script = (string) $script;
+            if (!preg_match(self::SCRIPT_NAME, $script) || strpos($script, '..') !== false) {
+                continue;
+            }
+
+            $fsPath = (string) $this->pathBuilder
+                ->withAppThemesDir($app)
+                ->withSlug($theme)
+                ->withPart($script);
+
+            if ($this->filesystem->isReadable($fsPath)) {
+                $scripts[] = $script;
+            }
+        }
+
+        return $scripts;
+    }
+
+    /**
+     * Include the theme's info.php in an isolated scope and return its
+     * declared $theme_scripts. Any read/parse failure yields an empty array.
+     *
+     * @return array<int|string, mixed>
+     */
+    private function declaredScripts(string $app, string $theme): array
+    {
+        $info = (string) $this->pathBuilder
+            ->withAppThemesDir($app)
+            ->withSlug($theme)
+            ->withPart('info.php');
+
+        if (!$this->filesystem->isReadable($info)) {
+            return [];
+        }
+
+        /* Declared before the include so the theme file only ever augments a
+         * known-shape local; nothing from the outer scope leaks in. */
+        $theme_scripts = [];
+
+        include $info;
+
+        return (array) $theme_scripts;
+    }
+}
diff --git a/src/Assets/ThemeInfoReader.php b/src/Assets/ThemeInfoReader.php
new file mode 100644
index 00000000..ed724bf9
--- /dev/null
+++ b/src/Assets/ThemeInfoReader.php
@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+use Horde\Core\Factory\ThemeInfoReaderFactory;
+use Horde\Injector\Attribute\Factory;
+
+/**
+ * Reads a theme's own asset declarations from its info.php.
+ *
+ * Themes may ship JavaScript alongside their CSS, images and sounds by
+ * declaring plain file names in the theme directory's info.php:
+ *
+ *   $theme_scripts = array('theme.js');
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+#[Factory(factory: ThemeInfoReaderFactory::class, method: 'create')]
+interface ThemeInfoReader
+{
+    /**
+     * Return the validated, readable script file names declared by a theme.
+     *
+     * Only plain *.js file names are returned; anything with a directory
+     * separator, a '..' segment, a non-.js extension or a missing/unreadable
+     * target file is dropped. A theme name that is not a plain directory name
+     * yields an empty list.
+     *
+     * @param string $app    Application the theme belongs to.
+     * @param string $theme  Theme name (as stored in user prefs/options).
+     *
+     * @return list<string> Validated script file names, in declaration order.
+     */
+    public function readScripts(string $app, string $theme): array;
+}
diff --git a/src/Assets/ThemeJsDiscoverer.php b/src/Assets/ThemeJsDiscoverer.php
new file mode 100644
index 00000000..578ad8d1
--- /dev/null
+++ b/src/Assets/ThemeJsDiscoverer.php
@@ -0,0 +1,113 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Assets;
+
+use Horde\Core\Path\PathBuilderInterface;
+use Horde\Core\Uri\UriBuilderInterface;
+
+/**
+ * Theme-aware JavaScript discoverer.
+ *
+ * The flat resolve()/resolveMany() API keeps its existing app-JS-dir
+ * behaviour. discoverTheme() adds a theme cascade parallel to the CSS
+ * discoverer: a theme may ship its own scripts (declared in info.php) and
+ * an application-level theme layers on top of the base 'horde' theme, so an
+ * app can add to or override the scripts a shared theme ships.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+class ThemeJsDiscoverer implements JsDiscoverer
+{
+    public function __construct(
+        private readonly PathBuilderInterface $pathBuilder,
+        private readonly UriBuilderInterface $uriBuilder,
+        private readonly AssetFilesystem $filesystem,
+        private readonly ThemeInfoReader $themeInfo,
+    ) {}
+
+    public function resolve(string $file, string $app = 'horde'): ?string
+    {
+        $fsPath = (string) $this->pathBuilder
+            ->withAppJsDir($app)
+            ->withPart($file);
+
+        if (!$this->filesystem->fileExists($fsPath)) {
+            return null;
+        }
+
+        return (string) $this->uriBuilder
+            ->withJsUri($app)
+            ->withPart($file);
+    }
+
+    public function resolveMany(array $files, string $app = 'horde'): array
+    {
+        $result = [];
+        foreach ($files as $file) {
+            $result[$file] = $this->resolve($file, $app);
+        }
+
+        return $result;
+    }
+
+    public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+    {
+        $entries = [];
+
+        /* Base 'horde' theme first, then the application theme on top. */
+        $this->collectLevel($entries, 'horde', $request->theme, $request->files);
+        if ($request->app !== 'horde') {
+            $this->collectLevel($entries, $request->app, $request->theme, $request->files);
+        }
+
+        return new JsDiscoveryResult($entries, $request->theme, $request->app);
+    }
+
+    /**
+     * @param list<JsAssetEntry> $entries
+     * @param list<string>       $explicitFiles  Caller-supplied files; when
+     *                                           empty the theme's own
+     *                                           declarations are used.
+     */
+    private function collectLevel(array &$entries, string $app, string $theme, array $explicitFiles): void
+    {
+        $files = $explicitFiles !== []
+            ? $explicitFiles
+            : $this->themeInfo->readScripts($app, $theme);
+
+        foreach ($files as $file) {
+            $fsPath = (string) $this->pathBuilder
+                ->withAppThemesDir($app)
+                ->withSlug($theme)
+                ->withPart($file);
+
+            if (!$this->filesystem->fileExists($fsPath)) {
+                continue;
+            }
+
+            $uri = (string) $this->uriBuilder
+                ->withThemesUri($app)
+                ->withSlug($theme)
+                ->withPart($file);
+
+            $entries[] = new JsAssetEntry($fsPath, $uri, $app);
+        }
+    }
+}
diff --git a/src/Factory/JsDiscovererFactory.php b/src/Factory/JsDiscovererFactory.php
index 5bba8c39..d0ae9a3b 100644
--- a/src/Factory/JsDiscovererFactory.php
+++ b/src/Factory/JsDiscovererFactory.php
@@ -18,7 +18,8 @@
 
 use Horde\Core\Assets\AssetFilesystem;
 use Horde\Core\Assets\JsDiscoverer;
-use Horde\Core\Assets\PathBasedJsDiscoverer;
+use Horde\Core\Assets\ThemeInfoReader;
+use Horde\Core\Assets\ThemeJsDiscoverer;
 use Horde\Core\Path\PathBuilderInterface;
 use Horde\Core\Uri\UriBuilderInterface;
 use Horde\Injector\Injector;
@@ -30,7 +31,8 @@ public function create(Injector $injector): JsDiscoverer
         $pathBuilder = $injector->getInstance(PathBuilderInterface::class);
         $uriBuilder = $injector->getInstance(UriBuilderInterface::class);
         $filesystem = $injector->getInstance(AssetFilesystem::class);
+        $themeInfo = $injector->getInstance(ThemeInfoReader::class);
 
-        return new PathBasedJsDiscoverer($pathBuilder, $uriBuilder, $filesystem);
+        return new ThemeJsDiscoverer($pathBuilder, $uriBuilder, $filesystem, $themeInfo);
     }
 }
diff --git a/src/Factory/ThemeInfoReaderFactory.php b/src/Factory/ThemeInfoReaderFactory.php
new file mode 100644
index 00000000..e2ba96a9
--- /dev/null
+++ b/src/Factory/ThemeInfoReaderFactory.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category  Horde
+ * @copyright 2026 The Horde Project
+ * @license   http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ * @package   Core
+ */
+
+namespace Horde\Core\Factory;
+
+use Horde\Core\Assets\AssetFilesystem;
+use Horde\Core\Assets\PhpThemeInfoReader;
+use Horde\Core\Assets\ThemeInfoReader;
+use Horde\Core\Path\PathBuilderInterface;
+use Horde\Injector\Injector;
+
+class ThemeInfoReaderFactory
+{
+    public function create(Injector $injector): ThemeInfoReader
+    {
+        return new PhpThemeInfoReader(
+            $injector->getInstance(PathBuilderInterface::class),
+            $injector->getInstance(AssetFilesystem::class),
+        );
+    }
+}
diff --git a/src/PageOutput/DesktopChromeRenderer.php b/src/PageOutput/DesktopChromeRenderer.php
index 6ec84eea..ec559d5d 100644
--- a/src/PageOutput/DesktopChromeRenderer.php
+++ b/src/PageOutput/DesktopChromeRenderer.php
@@ -17,6 +17,7 @@
 namespace Horde\Core\PageOutput;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
 use Horde\Core\Sidebar\SidebarRenderer;
 use Horde\Core\Topbar\TopbarBuilder;
 use Horde\Core\Topbar\TopbarRenderer;
@@ -34,6 +35,7 @@ public function __construct(
         private readonly TopbarRenderer $topbarRenderer,
         private readonly SidebarRenderer $sidebarRenderer,
         private readonly JsDiscoverer $jsDiscoverer,
+        private readonly string $theme = 'default',
     ) {}
 
     public function renderPage(PageContent $content, ServerRequestInterface $request): string
@@ -53,6 +55,14 @@ public function renderPage(PageContent $content, ServerRequestInterface $request
             }
         }
 
+        /* Scripts the active theme ships for itself (info.php $theme_scripts). */
+        $themeScripts = $this->jsDiscoverer->discoverTheme(
+            new JsDiscoveryRequest(app: $content->app, theme: $this->theme),
+        );
+        foreach ($themeScripts as $entry) {
+            $this->assetCollector->addScript($entry->uri);
+        }
+
         $meta = new PageMeta(title: $content->title);
         $html = $this->pageComposer->renderHead($meta);
 
diff --git a/src/PageOutput/DesktopChromeRendererFactory.php b/src/PageOutput/DesktopChromeRendererFactory.php
index 03e272bb..7d2f50fe 100644
--- a/src/PageOutput/DesktopChromeRendererFactory.php
+++ b/src/PageOutput/DesktopChromeRendererFactory.php
@@ -17,6 +17,8 @@
 namespace Horde\Core\PageOutput;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\ThemeResolver;
+use Horde\Core\Session\SessionAccess;
 use Horde\Core\Sidebar\SidebarRenderer;
 use Horde\Core\Topbar\TopbarBuilder;
 use Horde\Core\Topbar\TopbarRenderer;
@@ -26,6 +28,12 @@ class DesktopChromeRendererFactory
 {
     public function create(Injector $injector): DesktopChromeRenderer
     {
+        $session = $injector->getInstance(SessionAccess::class);
+        $themeResolver = $injector->get(ThemeResolver::class);
+
+        $authUid = $session->getAuthId();
+        $theme = $authUid !== null ? $themeResolver->resolve($authUid) : 'default';
+
         return new DesktopChromeRenderer(
             $injector->getInstance(AssetCollector::class),
             $injector->getInstance(PageComposer::class),
@@ -34,6 +42,7 @@ public function create(Injector $injector): DesktopChromeRenderer
             $injector->getInstance(TopbarRenderer::class),
             $injector->getInstance(SidebarRenderer::class),
             $injector->getInstance(JsDiscoverer::class),
+            $theme,
         );
     }
 }
diff --git a/src/PageOutput/ResponsiveChromeRenderer.php b/src/PageOutput/ResponsiveChromeRenderer.php
index 277e15a5..adb2ac46 100644
--- a/src/PageOutput/ResponsiveChromeRenderer.php
+++ b/src/PageOutput/ResponsiveChromeRenderer.php
@@ -20,6 +20,7 @@
 use Horde\Core\Assets\CssDiscoverer;
 use Horde\Core\Assets\CssDiscoveryRequest;
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
 use Horde\Injector\Attribute\Factory;
 use Psr\Http\Message\ServerRequestInterface;
 
@@ -36,6 +37,7 @@ public function __construct(
         private readonly CssDiscoverer $cssDiscoverer,
         private readonly JsDiscoverer $jsDiscoverer,
         Closure $topbarFactory,
+        private readonly string $theme = 'default',
     ) {
         $this->topbarFactory = $topbarFactory;
     }
@@ -96,6 +98,14 @@ private function buildJsUrls(string $app, array $extraFiles): array
             $jsUrls[] = $uri;
         }
 
+        /* Scripts the active theme ships for itself (info.php $theme_scripts). */
+        $themeScripts = $this->jsDiscoverer->discoverTheme(
+            new JsDiscoveryRequest(app: $app, theme: $this->theme),
+        );
+        foreach ($themeScripts as $entry) {
+            $jsUrls[] = $entry->uri;
+        }
+
         return $jsUrls;
     }
 
diff --git a/src/PageOutput/ResponsiveChromeRendererFactory.php b/src/PageOutput/ResponsiveChromeRendererFactory.php
index 2e3d8a8e..cdcec1d2 100644
--- a/src/PageOutput/ResponsiveChromeRendererFactory.php
+++ b/src/PageOutput/ResponsiveChromeRendererFactory.php
@@ -48,6 +48,7 @@ public function create(Injector $injector): ResponsiveChromeRenderer
             $injector->get(CssDiscoverer::class),
             $injector->get(JsDiscoverer::class),
             $topbarFactory,
+            $theme,
         );
     }
 }
diff --git a/test/Unit/Assets/JsDiscoveryRequestTest.php b/test/Unit/Assets/JsDiscoveryRequestTest.php
new file mode 100644
index 00000000..abe3af59
--- /dev/null
+++ b/test/Unit/Assets/JsDiscoveryRequestTest.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\Core\Test\Unit\Assets;
+
+use Horde\Core\Assets\JsDiscoveryRequest;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(JsDiscoveryRequest::class)]
+class JsDiscoveryRequestTest extends TestCase
+{
+    #[Test]
+    public function defaults(): void
+    {
+        $request = new JsDiscoveryRequest();
+
+        self::assertSame([], $request->files);
+        self::assertSame('horde', $request->app);
+        self::assertSame('default', $request->theme);
+    }
+
+    #[Test]
+    public function customValues(): void
+    {
+        $request = new JsDiscoveryRequest(
+            files: ['theme.js'],
+            app: 'turba',
+            theme: 'silver',
+        );
+
+        self::assertSame(['theme.js'], $request->files);
+        self::assertSame('turba', $request->app);
+        self::assertSame('silver', $request->theme);
+    }
+}
diff --git a/test/Unit/Assets/JsDiscoveryResultTest.php b/test/Unit/Assets/JsDiscoveryResultTest.php
new file mode 100644
index 00000000..e56b4839
--- /dev/null
+++ b/test/Unit/Assets/JsDiscoveryResultTest.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\Core\Test\Unit\Assets;
+
+use Horde\Core\Assets\JsAssetEntry;
+use Horde\Core\Assets\JsDiscoveryResult;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(JsDiscoveryResult::class)]
+#[CoversClass(JsAssetEntry::class)]
+class JsDiscoveryResultTest extends TestCase
+{
+    #[Test]
+    public function emptyResult(): void
+    {
+        $result = new JsDiscoveryResult([], 'default', 'horde');
+
+        self::assertTrue($result->isEmpty());
+        self::assertCount(0, $result);
+        self::assertSame([], $result->toArray());
+        self::assertSame('default', $result->getTheme());
+        self::assertSame('horde', $result->getApp());
+    }
+
+    #[Test]
+    public function iteratesEntriesInOrder(): void
+    {
+        $a = new JsAssetEntry('/fs/a.js', '/uri/a.js', 'horde');
+        $b = new JsAssetEntry('/fs/b.js', '/uri/b.js', 'turba');
+        $result = new JsDiscoveryResult([$a, $b], 'silver', 'turba');
+
+        self::assertFalse($result->isEmpty());
+        self::assertCount(2, $result);
+
+        $collected = [];
+        foreach ($result as $entry) {
+            $collected[] = $entry->uri;
+        }
+
+        self::assertSame(['/uri/a.js', '/uri/b.js'], $collected);
+        self::assertSame([$a, $b], $result->toArray());
+    }
+
+    #[Test]
+    public function entryExposesFields(): void
+    {
+        $entry = new JsAssetEntry('/fs/theme.js', '/uri/theme.js', 'turba');
+
+        self::assertSame('/fs/theme.js', $entry->fsPath);
+        self::assertSame('/uri/theme.js', $entry->uri);
+        self::assertSame('turba', $entry->app);
+    }
+}
diff --git a/test/Unit/Assets/PathBasedJsDiscovererTest.php b/test/Unit/Assets/PathBasedJsDiscovererTest.php
index 1537ceb7..b750c9d5 100644
--- a/test/Unit/Assets/PathBasedJsDiscovererTest.php
+++ b/test/Unit/Assets/PathBasedJsDiscovererTest.php
@@ -6,6 +6,7 @@
 
 use Horde\Core\Assets\AssetFilesystem;
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
 use Horde\Core\Assets\PathBasedJsDiscoverer;
 use Horde\Core\Path\PathBuilderInterface;
 use Horde\Core\Uri\UriBuilderInterface;
@@ -112,6 +113,18 @@ public function resolveManyEmpty(): void
         self::assertSame([], $result);
     }
 
+    #[Test]
+    public function discoverThemeIsAlwaysEmpty(): void
+    {
+        $discoverer = new PathBasedJsDiscoverer($this->pathBuilder, $this->uriBuilder, $this->filesystem);
+        $result = $discoverer->discoverTheme(new JsDiscoveryRequest(app: 'turba', theme: 'silver'));
+
+        self::assertTrue($result->isEmpty());
+        self::assertCount(0, $result);
+        self::assertSame('silver', $result->getTheme());
+        self::assertSame('turba', $result->getApp());
+    }
+
     /** @param array<string, string> $appJsDirs */
     private function createPathMock(array $appJsDirs): PathBuilderInterface
     {
diff --git a/test/Unit/Assets/PhpThemeInfoReaderTest.php b/test/Unit/Assets/PhpThemeInfoReaderTest.php
new file mode 100644
index 00000000..94f54294
--- /dev/null
+++ b/test/Unit/Assets/PhpThemeInfoReaderTest.php
@@ -0,0 +1,215 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\Core\Test\Unit\Assets;
+
+use Horde\Core\Assets\AssetFilesystem;
+use Horde\Core\Assets\LocalAssetFilesystem;
+use Horde\Core\Assets\PhpThemeInfoReader;
+use Horde\Core\Assets\ThemeInfoReader;
+use Horde\Core\Path\PathBuilderInterface;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use SplFileInfo;
+
+#[CoversClass(PhpThemeInfoReader::class)]
+class PhpThemeInfoReaderTest extends TestCase
+{
+    private string $root;
+    private PathBuilderInterface $pathBuilder;
+    private AssetFilesystem $filesystem;
+
+    protected function setUp(): void
+    {
+        $this->root = sys_get_temp_dir() . '/horde-theme-info-' . uniqid('', true);
+        $this->pathBuilder = $this->createPathMock($this->root);
+        $this->filesystem = new LocalAssetFilesystem();
+    }
+
+    protected function tearDown(): void
+    {
+        $this->removeTree($this->root);
+    }
+
+    #[Test]
+    public function implementsInterface(): void
+    {
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertInstanceOf(ThemeInfoReader::class, $reader);
+    }
+
+    #[Test]
+    public function returnsDeclaredReadableScript(): void
+    {
+        $this->writeTheme('horde', 'silver', "<?php\n\$theme_scripts = array('theme.js');\n", ['theme.js']);
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame(['theme.js'], $reader->readScripts('horde', 'silver'));
+    }
+
+    #[Test]
+    public function dropsDeclaredButMissingFile(): void
+    {
+        $this->writeTheme('horde', 'silver', "<?php\n\$theme_scripts = array('theme.js', 'ghost.js');\n", ['theme.js']);
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame(['theme.js'], $reader->readScripts('horde', 'silver'));
+    }
+
+    #[Test]
+    public function rejectsUnsafeScriptNames(): void
+    {
+        $this->writeTheme(
+            'horde',
+            'silver',
+            "<?php\n\$theme_scripts = array('../evil.js', 'a/b.js', 'http://x/y.js', 'theme.css', 'plain', '..js');\n",
+            [],
+        );
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame([], $reader->readScripts('horde', 'silver'));
+    }
+
+    #[Test]
+    public function rejectsUnsafeThemeName(): void
+    {
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame([], $reader->readScripts('horde', '../etc'));
+        self::assertSame([], $reader->readScripts('horde', 'foo/bar'));
+        self::assertSame([], $reader->readScripts('horde', ''));
+    }
+
+    #[Test]
+    public function missingInfoFileYieldsEmpty(): void
+    {
+        // Theme dir exists but no info.php.
+        $dir = $this->root . '/horde/silver';
+        mkdir($dir, 0777, true);
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame([], $reader->readScripts('horde', 'silver'));
+    }
+
+    #[Test]
+    public function infoWithoutScriptsYieldsEmpty(): void
+    {
+        $this->writeTheme('horde', 'silver', "<?php\n\$theme_covers = array('imp');\n", []);
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame([], $reader->readScripts('horde', 'silver'));
+    }
+
+    #[Test]
+    public function resolvesPerApp(): void
+    {
+        $this->writeTheme('turba', 'silver', "<?php\n\$theme_scripts = array('contacts.js');\n", ['contacts.js']);
+
+        $reader = new PhpThemeInfoReader($this->pathBuilder, $this->filesystem);
+
+        self::assertSame(['contacts.js'], $reader->readScripts('turba', 'silver'));
+        self::assertSame([], $reader->readScripts('horde', 'silver'));
+    }
+
+    /**
+     * @param list<string> $scriptFiles Script files to create alongside info.php.
+     */
+    private function writeTheme(string $app, string $theme, string $info, array $scriptFiles): void
+    {
+        $dir = $this->root . '/' . $app . '/' . $theme;
+        mkdir($dir, 0777, true);
+        file_put_contents($dir . '/info.php', $info);
+        foreach ($scriptFiles as $file) {
+            file_put_contents($dir . '/' . $file, '// js');
+        }
+    }
+
+    private function removeTree(string $path): void
+    {
+        if (!is_dir($path)) {
+            return;
+        }
+        $items = scandir($path);
+        foreach ($items === false ? [] : $items as $item) {
+            if ($item === '.' || $item === '..') {
+                continue;
+            }
+            $full = $path . '/' . $item;
+            is_dir($full) ? $this->removeTree($full) : unlink($full);
+        }
+        rmdir($path);
+    }
+
+    private function createPathMock(string $root): PathBuilderInterface
+    {
+        return new class ($root) implements PathBuilderInterface {
+            private string $path = '';
+
+            public function __construct(private readonly string $root) {}
+
+            public function withComponentRoot(): static
+            {
+                return $this;
+            }
+            public function withAppFileroot(string $app): static
+            {
+                return $this;
+            }
+
+            public function withAppThemesDir(string $app): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->root . '/' . $app;
+                return $clone;
+            }
+
+            public function withAppJsDir(string $app): static
+            {
+                return $this;
+            }
+            public function withStaticDir(): static
+            {
+                return $this;
+            }
+            public function withConfigDir(?string $app = null): static
+            {
+                return $this;
+            }
+            public function withTmpDir(): static
+            {
+                return $this;
+            }
+
+            public function withSlug(string $slug): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $slug;
+                return $clone;
+            }
+
+            public function withPart(string $part): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $part;
+                return $clone;
+            }
+
+            public function toSplFileInfo(): SplFileInfo
+            {
+                return new SplFileInfo($this->path);
+            }
+            public function __toString(): string
+            {
+                return $this->path;
+            }
+        };
+    }
+}
diff --git a/test/Unit/Assets/ThemeJsDiscovererTest.php b/test/Unit/Assets/ThemeJsDiscovererTest.php
new file mode 100644
index 00000000..ab26ac66
--- /dev/null
+++ b/test/Unit/Assets/ThemeJsDiscovererTest.php
@@ -0,0 +1,382 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\Core\Test\Unit\Assets;
+
+use Horde\Core\Assets\AssetFilesystem;
+use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
+use Horde\Core\Assets\LocalAssetFilesystem;
+use Horde\Core\Assets\ThemeInfoReader;
+use Horde\Core\Assets\ThemeJsDiscoverer;
+use Horde\Core\Path\PathBuilderInterface;
+use Horde\Core\Uri\UriBuilderInterface;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use SplFileInfo;
+use Stringable;
+
+#[CoversClass(ThemeJsDiscoverer::class)]
+class ThemeJsDiscovererTest extends TestCase
+{
+    private string $root;
+    private PathBuilderInterface $pathBuilder;
+    private UriBuilderInterface $uriBuilder;
+    private AssetFilesystem $filesystem;
+
+    protected function setUp(): void
+    {
+        $this->root = sys_get_temp_dir() . '/horde-theme-js-' . uniqid('', true);
+        mkdir($this->root, 0777, true);
+        $this->pathBuilder = $this->createPathMock($this->root);
+        $this->uriBuilder = $this->createUriMock();
+        $this->filesystem = new LocalAssetFilesystem();
+    }
+
+    protected function tearDown(): void
+    {
+        $this->removeTree($this->root);
+    }
+
+    #[Test]
+    public function implementsJsDiscoverer(): void
+    {
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::never())->method('readScripts');
+
+        $discoverer = $this->discoverer($reader);
+
+        self::assertInstanceOf(JsDiscoverer::class, $discoverer);
+    }
+
+    #[Test]
+    public function flatResolveStillUsesAppJsDir(): void
+    {
+        $this->createFile('horde/js/topbar.js');
+
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::never())->method('readScripts');
+
+        $discoverer = $this->discoverer($reader);
+
+        self::assertSame('/uri/horde/js/topbar.js', $discoverer->resolve('topbar.js'));
+        self::assertNull($discoverer->resolve('missing.js'));
+    }
+
+    #[Test]
+    public function discoverThemeUsesThemeDeclarations(): void
+    {
+        $this->createFile('horde/themes/silver/theme.js');
+
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::atLeastOnce())
+            ->method('readScripts')
+            ->with('horde', 'silver')
+            ->willReturn(['theme.js']);
+
+        $result = $this->discoverer($reader)
+            ->discoverTheme(new JsDiscoveryRequest(app: 'horde', theme: 'silver'));
+
+        self::assertCount(1, $result);
+        self::assertSame('/uri/horde/themes/silver/theme.js', $result->toArray()[0]->uri);
+    }
+
+    #[Test]
+    public function discoverThemeCascadesHordeThenApp(): void
+    {
+        $this->createFile('horde/themes/silver/base.js');
+        $this->createFile('turba/themes/silver/app.js');
+
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::atLeastOnce())
+            ->method('readScripts')
+            ->willReturnMap([
+                ['horde', 'silver', ['base.js']],
+                ['turba', 'silver', ['app.js']],
+            ]);
+
+        $result = $this->discoverer($reader)
+            ->discoverTheme(new JsDiscoveryRequest(app: 'turba', theme: 'silver'));
+
+        $uris = array_map(static fn($e): string => $e->uri, $result->toArray());
+
+        self::assertSame([
+            '/uri/horde/themes/silver/base.js',
+            '/uri/turba/themes/silver/app.js',
+        ], $uris);
+    }
+
+    #[Test]
+    public function discoverThemeSkipsMissingDeclaredFile(): void
+    {
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::atLeastOnce())
+            ->method('readScripts')
+            ->with('horde', 'silver')
+            ->willReturn(['ghost.js']);
+
+        $result = $this->discoverer($reader)
+            ->discoverTheme(new JsDiscoveryRequest(app: 'horde', theme: 'silver'));
+
+        self::assertTrue($result->isEmpty());
+    }
+
+    #[Test]
+    public function discoverThemeEmptyWhenNoDeclarations(): void
+    {
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::atLeastOnce())
+            ->method('readScripts')
+            ->with('horde', 'default')
+            ->willReturn([]);
+
+        $result = $this->discoverer($reader)
+            ->discoverTheme(new JsDiscoveryRequest(app: 'horde', theme: 'default'));
+
+        self::assertTrue($result->isEmpty());
+    }
+
+    #[Test]
+    public function discoverThemeExplicitFilesBypassReader(): void
+    {
+        $this->createFile('horde/themes/silver/given.js');
+
+        $reader = $this->createMock(ThemeInfoReader::class);
+        $reader->expects(self::never())->method('readScripts');
+
+        $result = $this->discoverer($reader)->discoverTheme(
+            new JsDiscoveryRequest(files: ['given.js'], app: 'horde', theme: 'silver'),
+        );
+
+        self::assertCount(1, $result);
+        self::assertSame('/uri/horde/themes/silver/given.js', $result->toArray()[0]->uri);
+    }
+
+    private function discoverer(ThemeInfoReader $reader): ThemeJsDiscoverer
+    {
+        return new ThemeJsDiscoverer($this->pathBuilder, $this->uriBuilder, $this->filesystem, $reader);
+    }
+
+    private function createFile(string $relative): void
+    {
+        $full = $this->root . '/' . $relative;
+        $dir = dirname($full);
+        if (!is_dir($dir)) {
+            mkdir($dir, 0777, true);
+        }
+        file_put_contents($full, '// js');
+    }
+
+    private function removeTree(string $path): void
+    {
+        if (!is_dir($path)) {
+            return;
+        }
+        $items = scandir($path);
+        foreach ($items === false ? [] : $items as $item) {
+            if ($item === '.' || $item === '..') {
+                continue;
+            }
+            $full = $path . '/' . $item;
+            is_dir($full) ? $this->removeTree($full) : unlink($full);
+        }
+        rmdir($path);
+    }
+
+    private function createPathMock(string $root): PathBuilderInterface
+    {
+        return new class ($root) implements PathBuilderInterface {
+            private string $path = '';
+
+            public function __construct(private readonly string $root)
+            {
+                $this->path = $root;
+            }
+
+            public function withComponentRoot(): static
+            {
+                return $this;
+            }
+            public function withAppFileroot(string $app): static
+            {
+                return $this;
+            }
+
+            public function withAppThemesDir(string $app): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->root . '/' . $app . '/themes';
+                return $clone;
+            }
+
+            public function withAppJsDir(string $app): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->root . '/' . $app . '/js';
+                return $clone;
+            }
+
+            public function withStaticDir(): static
+            {
+                return $this;
+            }
+            public function withConfigDir(?string $app = null): static
+            {
+                return $this;
+            }
+            public function withTmpDir(): static
+            {
+                return $this;
+            }
+
+            public function withSlug(string $slug): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $slug;
+                return $clone;
+            }
+
+            public function withPart(string $part): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $part;
+                return $clone;
+            }
+
+            public function toSplFileInfo(): SplFileInfo
+            {
+                return new SplFileInfo($this->path);
+            }
+            public function __toString(): string
+            {
+                return $this->path;
+            }
+        };
+    }
+
+    private function createUriMock(): UriBuilderInterface
+    {
+        return new class implements UriBuilderInterface, Stringable {
+            private string $path = '/uri';
+
+            public function withAppWebroot(string $app): static
+            {
+                return $this;
+            }
+
+            public function withThemesUri(string $app): static
+            {
+                $clone = clone $this;
+                $clone->path = '/uri/' . $app . '/themes';
+                return $clone;
+            }
+
+            public function withJsUri(string $app): static
+            {
+                $clone = clone $this;
+                $clone->path = '/uri/' . $app . '/js';
+                return $clone;
+            }
+
+            public function withStaticUri(): static
+            {
+                return $this;
+            }
+            public function withNamedRoute(string $app, string $name, array $params = []): static
+            {
+                return $this;
+            }
+            public function withQueryParams(array $params): static
+            {
+                return $this;
+            }
+
+            public function withSlug(string $slug): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $slug;
+                return $clone;
+            }
+
+            public function withPart(string $part): static
+            {
+                $clone = clone $this;
+                $clone->path = $this->path . '/' . $part;
+                return $clone;
+            }
+
+            public function toHordeUrl(): \Horde\Url\Url
+            {
+                return new \Horde\Url\Url($this->path);
+            }
+            public function getScheme(): string
+            {
+                return '';
+            }
+            public function getAuthority(): string
+            {
+                return '';
+            }
+            public function getUserInfo(): string
+            {
+                return '';
+            }
+            public function getHost(): string
+            {
+                return '';
+            }
+            public function getPort(): ?int
+            {
+                return null;
+            }
+            public function getPath(): string
+            {
+                return $this->path;
+            }
+            public function getQuery(): string
+            {
+                return '';
+            }
+            public function getFragment(): string
+            {
+                return '';
+            }
+            public function withScheme(string $scheme): static
+            {
+                return $this;
+            }
+            public function withUserInfo(string $user, ?string $password = null): static
+            {
+                return $this;
+            }
+            public function withHost(string $host): static
+            {
+                return $this;
+            }
+            public function withPort(?int $port): static
+            {
+                return $this;
+            }
+            public function withPath(string $path): static
+            {
+                $c = clone $this;
+                $c->path = $path;
+                return $c;
+            }
+            public function withQuery(string $query): static
+            {
+                return $this;
+            }
+            public function withFragment(string $fragment): static
+            {
+                return $this;
+            }
+            public function __toString(): string
+            {
+                return $this->path;
+            }
+        };
+    }
+}
diff --git a/test/Unit/PageOutput/DesktopChromeRendererTest.php b/test/Unit/PageOutput/DesktopChromeRendererTest.php
index 5ce36bec..16b28485 100644
--- a/test/Unit/PageOutput/DesktopChromeRendererTest.php
+++ b/test/Unit/PageOutput/DesktopChromeRendererTest.php
@@ -5,6 +5,7 @@
 namespace Horde\Core\Test\Unit\PageOutput;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryResult;
 use Horde\Core\PageOutput\AssetCollector;
 use Horde\Core\PageOutput\DesktopChromeRenderer;
 use Horde\Core\PageOutput\PageComposer;
@@ -98,9 +99,20 @@ private function defaultJsDiscoverer(): MockObject
     {
         $mock = $this->createMock(JsDiscoverer::class);
         $mock->expects($this->never())->method('resolve');
+        $this->stubDiscoverTheme($mock);
         return $mock;
     }
 
+    /**
+     * The renderer always asks for theme scripts; stub an empty result since
+     * JsDiscoveryResult is final and cannot be auto-generated by the mock.
+     */
+    private function stubDiscoverTheme(MockObject $mock): void
+    {
+        $mock->method('discoverTheme')
+            ->willReturn(new JsDiscoveryResult([], 'default', 'horde'));
+    }
+
     private function createRequest(RenderingMode $mode = RenderingMode::DYNAMIC): ServerRequest
     {
         $request = new ServerRequest('GET', 'http://localhost/horde/', [], null, '1.1', []);
@@ -208,6 +220,7 @@ public function renderPageResolvesExtraJsFiles(): void
             ->method('resolve')
             ->with('tasks.js', 'nag')
             ->willReturn('/js/nag/tasks.js');
+        $this->stubDiscoverTheme($jsDiscoverer);
 
         $renderer = $this->createRenderer(
             collector: $collector,
diff --git a/test/Unit/PageOutput/ResponsiveChromeRendererTest.php b/test/Unit/PageOutput/ResponsiveChromeRendererTest.php
index bc53b215..e0642692 100644
--- a/test/Unit/PageOutput/ResponsiveChromeRendererTest.php
+++ b/test/Unit/PageOutput/ResponsiveChromeRendererTest.php
@@ -8,6 +8,7 @@
 use Horde\Core\Assets\CssDiscoverer;
 use Horde\Core\Assets\CssDiscoveryResult;
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryResult;
 use Horde\Core\PageOutput\PageContent;
 use Horde\Core\PageOutput\RenderingMode;
 use Horde\Core\PageOutput\ResponsiveChromeRenderer;
@@ -51,10 +52,21 @@ private function defaultJsDiscoverer(): MockObject
             ->willReturnCallback(function (string $file) {
                 return '/js/' . $file;
             });
+        $this->stubDiscoverTheme($mock);
 
         return $mock;
     }
 
+    /**
+     * The renderer always asks for theme scripts; stub an empty result since
+     * JsDiscoveryResult is final and cannot be auto-generated by the mock.
+     */
+    private function stubDiscoverTheme(MockObject $mock): void
+    {
+        $mock->method('discoverTheme')
+            ->willReturn(new JsDiscoveryResult([], 'default', 'horde'));
+    }
+
     private function createRenderer(
         ?MockObject $cssDiscoverer = null,
         ?MockObject $jsDiscoverer = null,
@@ -201,6 +213,7 @@ public function renderPageHandlesNoJsResolutions(): void
         $jsDiscoverer = $this->createMock(JsDiscoverer::class);
         $jsDiscoverer->expects($this->atLeastOnce())
             ->method('resolve')->willReturn(null);
+        $this->stubDiscoverTheme($jsDiscoverer);
 
         $renderer = $this->createRenderer(jsDiscoverer: $jsDiscoverer);
         $content = new PageContent(title: 'Test', bodyHtml: '');
diff --git a/test/Unit/PageOutput/ViewModeConfiguratorDiscovererTest.php b/test/Unit/PageOutput/ViewModeConfiguratorDiscovererTest.php
index 1e0cf771..dc2d981f 100644
--- a/test/Unit/PageOutput/ViewModeConfiguratorDiscovererTest.php
+++ b/test/Unit/PageOutput/ViewModeConfiguratorDiscovererTest.php
@@ -5,6 +5,8 @@
 namespace Horde\Core\Test\Unit\PageOutput;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
+use Horde\Core\Assets\JsDiscoveryResult;
 use Horde\Core\PageOutput\AssetCollector;
 use Horde\Core\PageOutput\ViewMode;
 use Horde\Core\PageOutput\ViewModeConfigurator;
@@ -43,6 +45,11 @@ public function resolveMany(array $files, string $app = 'horde'): array
                 }
                 return $result;
             }
+
+            public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+            {
+                return new JsDiscoveryResult([], $request->theme, $request->app);
+            }
         };
     }
 
@@ -225,6 +232,11 @@ public function resolveMany(array $files, string $app = 'horde'): array
                 $this->apps[] = $app;
                 return array_combine($files, array_map(fn($f) => '/js/' . $f, $files));
             }
+
+            public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+            {
+                return new JsDiscoveryResult([], $request->theme, $request->app);
+            }
         };
 
         // BASIC mode without an authenticated user only consults the session.
diff --git a/test/Unit/Sidebar/SidebarRendererScriptRegistrationTest.php b/test/Unit/Sidebar/SidebarRendererScriptRegistrationTest.php
index d499536f..6bb01d96 100644
--- a/test/Unit/Sidebar/SidebarRendererScriptRegistrationTest.php
+++ b/test/Unit/Sidebar/SidebarRendererScriptRegistrationTest.php
@@ -5,6 +5,8 @@
 namespace Horde\Core\Test\Unit\Sidebar;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
+use Horde\Core\Assets\JsDiscoveryResult;
 use Horde\Core\PageOutput\AssetCollector;
 use Horde\Core\Sidebar\SidebarContainer;
 use Horde\Core\Sidebar\SidebarData;
@@ -42,6 +44,11 @@ public function resolveMany(array $files, string $app = 'horde'): array
                 }
                 return $result;
             }
+
+            public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+            {
+                return new JsDiscoveryResult([], $request->theme, $request->app);
+            }
         };
     }
 
diff --git a/test/Unit/Topbar/TopbarRendererScriptRegistrationTest.php b/test/Unit/Topbar/TopbarRendererScriptRegistrationTest.php
index d2bf0ed3..81cce032 100644
--- a/test/Unit/Topbar/TopbarRendererScriptRegistrationTest.php
+++ b/test/Unit/Topbar/TopbarRendererScriptRegistrationTest.php
@@ -5,6 +5,8 @@
 namespace Horde\Core\Test\Unit\Topbar;
 
 use Horde\Core\Assets\JsDiscoverer;
+use Horde\Core\Assets\JsDiscoveryRequest;
+use Horde\Core\Assets\JsDiscoveryResult;
 use Horde\Core\PageOutput\AssetCollector;
 use Horde\Core\Topbar\TopbarData;
 use Horde\Core\Topbar\TopbarRenderer;
@@ -41,6 +43,11 @@ public function resolveMany(array $files, string $app = 'horde'): array
                 }
                 return $result;
             }
+
+            public function discoverTheme(JsDiscoveryRequest $request): JsDiscoveryResult
+            {
+                return new JsDiscoveryResult([], $request->theme, $request->app);
+            }
         };
     }