diff --git a/app/Mcp/Tools/Deploy.php b/app/Mcp/Tools/Deploy.php
index 769b7cacd4..980e9e051d 100644
--- a/app/Mcp/Tools/Deploy.php
+++ b/app/Mcp/Tools/Deploy.php
@@ -42,6 +42,9 @@ class Deploy extends Tool
 
         $force = filter_var($request->get('force'), FILTER_VALIDATE_BOOLEAN);
         $pullRequestId = (int) ($request->get('pull_request_id') ?? 0);
+        if ($pullRequestId < 0 || $pullRequestId > 2147483647) {
+            return $this->mcpError($request, 'pull_request_id must be between 0 and 2147483647.', ['resource_uuid' => $uuid]);
+        }
         $deploymentUuid = new_public_id();
 
         $result = queue_application_deployment(
diff --git a/tests/Feature/Mcp/McpDeployPullRequestIdRangeTest.php b/tests/Feature/Mcp/McpDeployPullRequestIdRangeTest.php
new file mode 100644
index 0000000000..a1b88dd015
--- /dev/null
+++ b/tests/Feature/Mcp/McpDeployPullRequestIdRangeTest.php
@@ -0,0 +1,77 @@
+<?php
+
+use App\Models\Application;
+use App\Models\ApplicationDeploymentQueue;
+use App\Models\Environment;
+use App\Models\InstanceSettings;
+use App\Models\Project;
+use App\Models\Server;
+use App\Models\StandaloneDocker;
+use App\Models\Team;
+use App\Models\User;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\Queue;
+
+uses(RefreshDatabase::class);
+
+beforeEach(function () {
+    config([
+        'cache.default' => 'array',
+        'session.driver' => 'array',
+        'app.maintenance.driver' => 'file',
+    ]);
+    Queue::fake();
+
+    InstanceSettings::query()->delete();
+    $settings = new InstanceSettings(['is_mcp_server_enabled' => true]);
+    $settings->id = 0;
+    $settings->save();
+
+    $this->team = Team::factory()->create();
+    $this->user = User::factory()->create();
+    $this->team->members()->attach($this->user->id, ['role' => 'owner']);
+    session(['currentTeam' => $this->team]);
+
+    $server = Server::factory()->create(['team_id' => $this->team->id]);
+    $destination = StandaloneDocker::query()->where('server_id', $server->id)->firstOrFail();
+    $project = Project::factory()->create(['team_id' => $this->team->id]);
+    $environment = $project->environments()->first()
+        ?? Environment::factory()->create(['project_id' => $project->id]);
+    $this->application = Application::factory()->create([
+        'environment_id' => $environment->id,
+        'destination_id' => $destination->id,
+        'destination_type' => $destination->getMorphClass(),
+    ]);
+});
+
+function mcpDeployPullRequestCall(array $arguments)
+{
+    auth()->forgetGuards();
+    $token = test()->user->createToken('mcp-deploy-pr', ['read', 'deploy'])->plainTextToken;
+
+    return test()->withHeaders([
+        'Content-Type' => 'application/json',
+        'Accept' => 'application/json, text/event-stream',
+        'Authorization' => 'Bearer '.$token,
+    ])->postJson('/mcp', [
+        'jsonrpc' => '2.0',
+        'id' => 1,
+        'method' => 'tools/call',
+        'params' => ['name' => 'deploy', 'arguments' => (object) $arguments],
+    ]);
+}
+
+test('deploy tool rejects a pull request id above the database integer range', function (int $pullRequestId) {
+    $response = mcpDeployPullRequestCall([
+        'uuid' => $this->application->uuid,
+        'pull_request_id' => $pullRequestId,
+    ]);
+
+    $response->assertOk();
+    expect($response->json('result.isError'))->toBeTrue()
+        ->and($response->json('result.content.0.text'))->toContain('pull_request_id must be between 0 and 2147483647')
+        ->and(ApplicationDeploymentQueue::query()->count())->toBe(0);
+})->with([
+    'above int4' => 3000000000,
+    'negative' => -1,
+]);