diff --git a/MILESTONES.md b/MILESTONES.md
index d5710c6..d0634d3 100644
--- a/MILESTONES.md
+++ b/MILESTONES.md
@@ -14,15 +14,17 @@ Phred supports REST and JSON:API via env setting; batteries-included defaults, s
   * ~~Integrate `nikic/fast-route` with a RouteCollector and dispatcher.~~
   * ~~Define route → controller resolution (invokable controllers).~~
   * ~~Add minimal app bootstrap (front controller) and DI container wiring (`PHP-DI`).~~
+  * ~~Addendum: Route groups (prefix only) via `Router::group()`~~
 * ~~Acceptance:~~
   * ~~Sample route returning a JSON 200 via controller.~~
   * ~~Controllers are invokable (`__invoke(Request)`), one route per controller.~~
-## M2 — Configuration and environment
-* Tasks:
-  * Load `.env` via `vlucas/phpdotenv` and expose `Phred\Support\Config`.
-  * Define configuration precedence and document keys (e.g., `API_FORMAT`, `APP_ENV`, `APP_DEBUG`).
-* Acceptance:
-  * App reads config from `.env`; unit test demonstrates override behavior.
+  * ~~Route groups (prefix only) work and are tested.~~
+## ~~M2 — Configuration and environment~~
+* ~~Tasks:~~
+  * ~~Load `.env` via `vlucas/phpdotenv` and expose `Phred\Support\Config`.~~
+  * ~~Define configuration precedence and document keys (e.g., `API_FORMAT`, `APP_ENV`, `APP_DEBUG`).~~
+* ~~Acceptance:~~
+  * ~~App reads config from `.env`; unit test demonstrates override behavior.~~
 ## M3 — API formats and content negotiation
 * Tasks:
   * Finalize `ContentNegotiationMiddleware` using `.env` and `Accept` header.
diff --git a/README.md b/README.md
index 286b865..8b6cd99 100644
--- a/README.md
+++ b/README.md
@@ -123,3 +123,28 @@ return new class extends Command {
     public function handle(Input $in, Output $out): int { $out->writeln('Hello!'); return 0; }
 };
 ```
+
+Configuration and environment
+
+- Phred uses `vlucas/phpdotenv` to load a `.env` file from your project root (loaded in `bootstrap/app.php`).
+- Access configuration anywhere via `Phred\Support\Config::get(<key>, <default>)`.
+  - Precedence: environment variables > config files > provided default.
+  - Keys may be provided in either UPPER_SNAKE (e.g., `APP_ENV`) or dot.notation (e.g., `app.env`).
+  - Config files live under `config/*.php` and return arrays; dot keys are addressed as `<file>.<path>` (e.g., `app.timezone`).
+
+Common keys
+
+- `APP_ENV` (default from config/app.php: `local`)
+- `APP_DEBUG` (`true`/`false`)
+- `APP_TIMEZONE` (default `UTC`)
+- `API_FORMAT` (`rest` | `jsonapi`; default `rest`)
+
+Examples
+
+```php
+use Phred\Support\Config;
+
+$env = Config::get('APP_ENV', 'local');      // reads from env, then config/app.php, else 'local'
+$tz  = Config::get('app.timezone', 'UTC');   // reads nested key from config files
+$fmt = strtolower(Config::get('API_FORMAT', 'rest'));
+```
diff --git a/src/Http/Router.php b/src/Http/Router.php
index ec97a8e..3b268ce 100644
--- a/src/Http/Router.php
+++ b/src/Http/Router.php
@@ -36,4 +36,17 @@ final class Router
     {
         $this->collector->addRoute('DELETE', $path, $handler);
     }
+
+    /**
+     * Group routes under a common path prefix.
+     *
+     * Example:
+     * $router->group('/api', function (Router $r) { $r->get('/health', Handler::class); });
+     */
+    public function group(string $prefix, callable $routes): void
+    {
+        $this->collector->addGroup($prefix, function (RouteCollector $rc) use ($routes): void {
+            $routes(new Router($rc));
+        });
+    }
 }
diff --git a/src/Support/Config.php b/src/Support/Config.php
index 6ddae6e..edc5dad 100644
--- a/src/Support/Config.php
+++ b/src/Support/Config.php
@@ -6,21 +6,23 @@ namespace Phred\Support;
 
 final class Config
 {
+    /** @var array<string,mixed>|null */
+    private static ?array $store = null;
+
     /**
-     * Get a config value from environment variables or return default.
-     * Accepts both UPPER_CASE and dot.notation keys (the latter is for future file-based config).
+     * Get configuration value with precedence:
+     * 1) Environment variables (UPPER_CASE or dot.notation translated)
+     * 2) Loaded config files from config/*.php, accessible via dot.notation (e.g., app.env)
+     * 3) Provided $default
      */
     public static function get(string $key, mixed $default = null): mixed
     {
-        // Support dot.notation by converting to uppercase with underscores for env lookup.
+        // 1) Environment lookup (supports dot.notation by converting to UPPER_SNAKE)
         $envKey = strtoupper(str_replace('.', '_', $key));
-
         $value = getenv($envKey);
         if ($value !== false) {
             return $value;
         }
-
-        // Fallback to server superglobal if present.
         if (isset($_SERVER[$envKey])) {
             return $_SERVER[$envKey];
         }
@@ -28,6 +30,64 @@ final class Config
             return $_ENV[$envKey];
         }
 
+        // 2) Config files (lazy load once)
+        self::ensureLoaded();
+        if (self::$store) {
+            $fromStore = self::getFromStore($key);
+            if ($fromStore !== null) {
+                return $fromStore;
+            }
+        }
+
+        // 3) Default
         return $default;
     }
+
+    private static function ensureLoaded(): void
+    {
+        if (self::$store !== null) {
+            return;
+        }
+        self::$store = [];
+        $root = getcwd();
+        $configDir = $root . DIRECTORY_SEPARATOR . 'config';
+        if (!is_dir($configDir)) {
+            return; // no config directory; keep empty store
+        }
+        foreach (glob($configDir . '/*.php') ?: [] as $file) {
+            $key = basename($file, '.php');
+            try {
+                $data = require $file;
+                if (is_array($data)) {
+                    self::$store[$key] = $data;
+                }
+            } catch (\Throwable) {
+                // ignore malformed config files to avoid breaking runtime
+            }
+        }
+    }
+
+    private static function getFromStore(string $key): mixed
+    {
+        // dot.notation: first segment is file key, remaining traverse array
+        if (str_contains($key, '.')) {
+            $parts = explode('.', $key);
+            $rootKey = array_shift($parts);
+            if ($rootKey === null || !isset(self::$store[$rootKey])) {
+                return null;
+            }
+            $cursor = self::$store[$rootKey];
+            foreach ($parts as $p) {
+                if (is_array($cursor) && array_key_exists($p, $cursor)) {
+                    $cursor = $cursor[$p];
+                } else {
+                    return null;
+                }
+            }
+            return $cursor;
+        }
+
+        // non-dotted: try exact file key
+        return self::$store[$key] ?? null;
+    }
 }
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
new file mode 100644
index 0000000..d6e08e6
--- /dev/null
+++ b/tests/ConfigTest.php
@@ -0,0 +1,40 @@
+<?php
+declare(strict_types=1);
+
+namespace Phred\Tests;
+
+use Phred\Support\Config;
+use PHPUnit\Framework\TestCase;
+
+final class ConfigTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        // Clean up env changes
+        putenv('APP_ENV');
+        unset($_ENV['APP_ENV'], $_SERVER['APP_ENV']);
+        putenv('APP_DEBUG');
+        unset($_ENV['APP_DEBUG'], $_SERVER['APP_DEBUG']);
+        putenv('API_FORMAT');
+        unset($_ENV['API_FORMAT'], $_SERVER['API_FORMAT']);
+    }
+
+    public function testEnvOverridesConfigFile(): void
+    {
+        // config/app.php sets 'env' => 'local' by default; ensure ENV wins
+        putenv('APP_ENV=production');
+        $this->assertSame('production', Config::get('APP_ENV'));
+        $this->assertSame('production', Config::get('app.env'));
+    }
+
+    public function testReadsFromConfigFileWhenEnvMissing(): void
+    {
+        // From config/app.php
+        $this->assertSame('UTC', Config::get('app.timezone'));
+    }
+
+    public function testReturnsDefaultWhenNotFound(): void
+    {
+        $this->assertSame('fallback', Config::get('nonexistent.key', 'fallback'));
+    }
+}
diff --git a/tests/RouterGroupTest.php b/tests/RouterGroupTest.php
new file mode 100644
index 0000000..e4830d9
--- /dev/null
+++ b/tests/RouterGroupTest.php
@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace Phred\Tests;
+
+use FastRoute\Dispatcher;
+use FastRoute\RouteCollector;
+use Nyholm\Psr7\Factory\Psr17Factory;
+use Nyholm\Psr7Server\ServerRequestCreator;
+use PHPUnit\Framework\TestCase;
+use Phred\Http\Router;
+use function FastRoute\simpleDispatcher;
+
+final class RouterGroupTest extends TestCase
+{
+    public function testGroupPrefixesRoutes(): void
+    {
+        $dispatcher = simpleDispatcher(function (RouteCollector $rc): void {
+            $router = new Router($rc);
+            $router->group('/api', function (Router $r): void {
+                $r->get('/health', [\Phred\Http\Controllers\HealthController::class, '__invoke']);
+            });
+        });
+
+        $psr17 = new Psr17Factory();
+        $creator = new ServerRequestCreator($psr17, $psr17, $psr17, $psr17);
+        $req = $creator->fromGlobals()->withMethod('GET')->withUri($psr17->createUri('/api/health'));
+
+        $routeInfo = $dispatcher->dispatch($req->getMethod(), $req->getUri()->getPath());
+        $this->assertSame(Dispatcher::FOUND, $routeInfo[0] ?? null, 'Route in group should be found with prefixed path');
+        $this->assertIsArray($routeInfo[1] ?? null);
+    }
+}