diff --git a/framework/core/src/Foundation/Config.php b/framework/core/src/Foundation/Config.php
new file mode 100644
index 000000000..e540bedfa
--- /dev/null
+++ b/framework/core/src/Foundation/Config.php
@@ -0,0 +1,75 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Foundation;
+
+use ArrayAccess;
+use Illuminate\Support\Arr;
+use InvalidArgumentException;
+use Laminas\Diactoros\Uri;
+use Psr\Http\Message\UriInterface;
+use RuntimeException;
+
+class Config implements ArrayAccess
+{
+    private $data;
+
+    public function __construct(array $data)
+    {
+        $this->data = $data;
+
+        $this->requireKeys('url');
+    }
+
+    public function url(): UriInterface
+    {
+        return new Uri(rtrim($this->data['url'], '/'));
+    }
+
+    public function inDebugMode(): bool
+    {
+        return $this->data['debug'] ?? false;
+    }
+
+    public function inMaintenanceMode(): bool
+    {
+        return $this->data['offline'] ?? false;
+    }
+
+    private function requireKeys(...$keys)
+    {
+        foreach ($keys as $key) {
+            if (! array_key_exists($key, $this->data)) {
+                throw new InvalidArgumentException(
+                    "Configuration is invalid without a $key key"
+                );
+            }
+        }
+    }
+
+    public function offsetGet($offset)
+    {
+        return Arr::get($this->data, $offset);
+    }
+
+    public function offsetExists($offset)
+    {
+        return Arr::has($this->data, $offset);
+    }
+
+    public function offsetSet($offset, $value)
+    {
+        throw new RuntimeException('The Config is immutable');
+    }
+
+    public function offsetUnset($offset)
+    {
+        throw new RuntimeException('The Config is immutable');
+    }
+}
diff --git a/framework/core/tests/unit/Foundation/ConfigTest.php b/framework/core/tests/unit/Foundation/ConfigTest.php
new file mode 100644
index 000000000..a80acf2b7
--- /dev/null
+++ b/framework/core/tests/unit/Foundation/ConfigTest.php
@@ -0,0 +1,155 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\unit\Foundation;
+
+use Flarum\Foundation\Config;
+use Flarum\Tests\unit\TestCase;
+use InvalidArgumentException;
+use RuntimeException;
+
+class ConfigTest extends TestCase
+{
+    /** @test */
+    public function it_complains_when_base_url_is_missing()
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        new Config([]);
+    }
+
+    /** @test */
+    public function it_wraps_base_url_in_value_object()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local/myforum/',
+        ]);
+
+        $url = $config->url();
+        $this->assertEquals('https', $url->getScheme());
+        $this->assertEquals('/myforum', $url->getPath()); // Note that trailing slashes are removed
+        $this->assertEquals('https://flarum.local/myforum', (string) $url);
+    }
+
+    /** @test */
+    public function it_has_a_helper_for_debug_mode()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'debug' => false,
+        ]);
+
+        $this->assertFalse($config->inDebugMode());
+
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'debug' => true,
+        ]);
+
+        $this->assertTrue($config->inDebugMode());
+    }
+
+    /** @test */
+    public function it_turns_off_debug_mode_by_default()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+        ]);
+
+        $this->assertFalse($config->inDebugMode());
+    }
+
+    /** @test */
+    public function it_has_a_helper_for_maintenance_mode()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'offline' => false,
+        ]);
+
+        $this->assertFalse($config->inMaintenanceMode());
+
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'offline' => true,
+        ]);
+
+        $this->assertTrue($config->inMaintenanceMode());
+    }
+
+    /** @test */
+    public function it_turns_off_maintenance_mode_by_default()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+        ]);
+
+        $this->assertFalse($config->inMaintenanceMode());
+    }
+
+    /** @test */
+    public function it_exposes_additional_keys_via_array_access()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'custom_a' => 'b',
+        ]);
+
+        $this->assertEquals('b', $config['custom_a']);
+    }
+
+    /** @test */
+    public function it_exposes_nested_keys_via_dot_syntax()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'nested' => [
+                'first' => '1',
+                'second' => '2',
+            ],
+        ]);
+
+        $this->assertEquals('1', $config['nested.first']);
+        $this->assertEquals('2', $config['nested.second']);
+    }
+
+    /** @test */
+    public function it_does_not_allow_mutation_via_array_access()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'custom_a' => 'b',
+        ]);
+
+        try {
+            $config['custom_a'] = 'c';
+        } catch (RuntimeException $_) {
+        }
+
+        // Ensure the value was not changed
+        $this->assertEquals('b', $config['custom_a']);
+    }
+
+    /** @test */
+    public function it_does_not_allow_removal_via_array_access()
+    {
+        $config = new Config([
+            'url' => 'https://flarum.local',
+            'custom_a' => 'b',
+        ]);
+
+        try {
+            unset($config['custom_a']);
+        } catch (RuntimeException $_) {
+        }
+
+        // Ensure the value was not changed
+        $this->assertEquals('b', $config['custom_a']);
+    }
+}