diff --git a/public/index.php b/public/index.php
index c4d07cc..a2bcea4 100644
--- a/public/index.php
+++ b/public/index.php
@@ -70,11 +70,13 @@ if ($contentType !== null) {
 }
 
 // 5. Read the raw body for fetch POSTs that submit JSON.
-$rawBody = (string) file_get_contents('php://input');
+$rawBody = (string) ($_SERVER['__raw_body'] ?? file_get_contents('php://input'));
 
 // 6. Build a Request with the request data, the CSRF secret, and the upload token.
 $server = $_SERVER;
-$server['__csrf_secret'] = $secret;
+if (!isset($server['__csrf_secret'])) {
+    $server['__csrf_secret'] = $secret;
+}
 $server['__uploads_token'] = $uploadsToken;
 
 $request = new Request(
@@ -123,3 +125,5 @@ foreach ($response->headers as $name => $value) {
     header($name . ': ' . $value);
 }
 echo $response->body;
+
+return $response->status;
diff --git a/tests/Integration/FullFlowTest.php b/tests/Integration/FullFlowTest.php
new file mode 100644
index 0000000..133ea2a
--- /dev/null
+++ b/tests/Integration/FullFlowTest.php
@@ -0,0 +1,163 @@
+<?php
+
+declare(strict_types=1);
+
+namespace BattleForge\Tests\Integration;
+
+use BattleForge\Http\CsrfToken;
+use PHPUnit\Framework\TestCase;
+
+final class FullFlowTest extends TestCase
+{
+    private const SECRET = 'unit-test-secret';
+
+    protected function setUp(): void
+    {
+        // Reset superglobals between requests.
+        $_GET = [];
+        $_POST = [];
+        $_FILES = [];
+        $_COOKIE = [];
+        $_SERVER = [];
+    }
+
+    public function testTheFullCreateAndSaveFlow(): void
+    {
+        [$token, $cookie] = CsrfToken::issue(self::SECRET);
+        $uploadsRoot = sys_get_temp_dir() . '/bf-fullflow-' . bin2hex(random_bytes(4));
+        mkdir($uploadsRoot, 0700, true);
+
+        try {
+            // Step 1: GET home page.
+            $_SERVER['REQUEST_METHOD'] = 'GET';
+            $_SERVER['REQUEST_URI'] = '/';
+            $homeBody = $this->runFrontController();
+            self::assertStringContainsString('New scenario', $homeBody);
+            self::assertStringContainsString('name="csrf-token"', $homeBody);
+
+            // Step 2: POST team editor.
+            $_COOKIE['__csrf'] = $cookie;
+            $_SERVER['REQUEST_METHOD'] = 'POST';
+            $_SERVER['REQUEST_URI'] = '/scenarios/demo/edit/team';
+            $_SERVER['CONTENT_TYPE'] = 'application/x-www-form-urlencoded';
+            $_SERVER['__csrf_secret'] = self::SECRET;
+            $_POST = $this->validTeamPost($token);
+            $teamBody = $this->runFrontController();
+            self::assertSame(200, $this->lastStatus);
+            self::assertStringContainsString('localStorage.setItem', $teamBody);
+            self::assertStringContainsString('scenario:demo', $teamBody);
+
+            // Step 3: POST battlefield editor.
+            $_SERVER['REQUEST_METHOD'] = 'POST';
+            $_SERVER['REQUEST_URI'] = '/scenarios/demo/edit/battlefield';
+            $_SERVER['CONTENT_TYPE'] = 'application/json';
+            $_SERVER['HTTP_X_CSRF_TOKEN'] = $token;
+            $_POST = [];
+            $this->rawBody = json_encode($this->validBattlefieldPayload(), JSON_THROW_ON_ERROR);
+            $_SERVER['__raw_body'] = $this->rawBody;
+            $bfBody = $this->runFrontController();
+            self::assertSame(200, $this->lastStatus);
+            $bfJson = json_decode($bfBody, true);
+            self::assertSame(true, $bfJson['ok'] ?? null);
+
+            // Step 4: POST start-match.
+            $_SERVER['REQUEST_METHOD'] = 'POST';
+            $_SERVER['REQUEST_URI'] = '/scenarios/demo/start';
+            $this->rawBody = json_encode($this->validBattlefieldPayload(), JSON_THROW_ON_ERROR);
+            $_SERVER['__raw_body'] = $this->rawBody;
+            $startBody = $this->runFrontController();
+            self::assertSame(200, $this->lastStatus);
+            $startJson = json_decode($startBody, true);
+            self::assertSame('alpha', $startJson['match']['activeTeamId'] ?? null);
+            self::assertSame(1, $startJson['match']['round'] ?? null);
+            self::assertCount(6, $startJson['match']['units'] ?? []);
+        } finally {
+            if (is_dir($uploadsRoot)) {
+                foreach (glob($uploadsRoot . '/*/*') as $file) {
+                    unlink($file);
+                }
+                foreach (glob($uploadsRoot . '/*') as $dir) {
+                    rmdir($dir);
+                }
+                rmdir($uploadsRoot);
+            }
+        }
+    }
+
+    private string $rawBody = '';
+    private int $lastStatus = 0;
+
+    private function runFrontController(): string
+    {
+        $this->lastStatus = 0;
+        $body = $this->captureOutput(function (): void {
+            $this->lastStatus = (require __DIR__ . '/../../public/index.php') ?? http_response_code();
+        });
+        return $body;
+    }
+
+    /** @param callable(): void $fn */
+    private function captureOutput(callable $fn): string
+    {
+        ob_start();
+        try {
+            $fn();
+        } finally {
+            $output = (string) ob_get_clean();
+        }
+        return $output;
+    }
+
+    /** @return array<string, mixed> */
+    private function validTeamPost(string $token): array
+    {
+        return [
+            '_csrf' => $token,
+            'id' => 'demo',
+            'name' => 'Demo',
+            'battlefieldWidth' => '8',
+            'battlefieldHeight' => '8',
+            'teamA' => ['units' => $this->unitRows('a', 0, 2, 0)],
+            'teamB' => ['units' => $this->unitRows('b', 5, 7, 7)],
+            'victoryCondition' => 'eliminate_all',
+            'holdRoundsRequired' => '1',
+        ];
+    }
+
+    /** @return array<string, mixed> */
+    private function validBattlefieldPayload(): array
+    {
+        return [
+            'id' => 'demo',
+            'name' => 'Demo',
+            'battlefieldWidth' => 8,
+            'battlefieldHeight' => 8,
+            'battlefieldTerrain' => [],
+            'teamA' => ['units' => $this->unitRows('a', 0, 2, 0)],
+            'teamB' => ['units' => $this->unitRows('b', 5, 7, 7)],
+            'victoryCondition' => 'eliminate_all',
+            'holdRoundsRequired' => 1,
+        ];
+    }
+
+    /**
+     * @return list<array<string, string|int>>
+     */
+    private function unitRows(string $teamPrefix, int $xStart, int $xEnd, int $y): array
+    {
+        $rows = [];
+        for ($i = 0; $i <= $xEnd - $xStart; $i++) {
+            $rows[] = [
+                'id' => "{$teamPrefix}{$i}",
+                'archetype' => 'defender',
+                'maxHealth' => 12,
+                'attack' => 3,
+                'defense' => 4,
+                'speed' => 2,
+                'x' => $xStart + $i,
+                'y' => $y,
+            ];
+        }
+        return $rows;
+    }
+}