diff --git a/src/Site/Core/Config.php b/src/Site/Core/Config.php
index c7e3003..976edc6 100644
--- a/src/Site/Core/Config.php
+++ b/src/Site/Core/Config.php
@@ -12,10 +12,6 @@ declare(strict_types=1);
 
 namespace SiteWeaver\Core;
 
-use Infisical\SDK\InfisicalSDK;
-use Infisical\SDK\Services\UniversalAuthService;
-use Infisical\SDK\Models\MachineIdentityCredential;
-
 /**
  * Configuration service that loads environment variables and optionally fetches secrets from Infisical.
  */
@@ -31,6 +27,22 @@ class Config
         return $this->values[$key] ?? $default;
     }
 
+    /**
+     * Explicitly set or overwrite a configuration value.
+     *
+     * @param string $key   The configuration key.
+     * @param mixed  $value The new value.
+     */
+    public function set(string $key, mixed $value, bool $override = false): void
+    {
+        if ($override || !array_key_exists($key, $this->values)) {
+            // Allow null values to be stored as well.
+            if ($key !== null) {
+                $this->values[$key] = $value;
+            }
+        }
+    }
+
     /**
      * Return all configuration values.
      */
@@ -47,4 +59,3 @@ class Config
         }
     }
 }
-
diff --git a/tests/unit/Core/ConfigTest.php b/tests/unit/Core/ConfigTest.php
index 26035e6..c74b814 100644
--- a/tests/unit/Core/ConfigTest.php
+++ b/tests/unit/Core/ConfigTest.php
@@ -39,4 +39,35 @@ final class ConfigTest extends TestCase
 
         $this->assertSame($env, $config->all());
     }
+
+    public function testNoOverrideByDefault(): void {
+        $env = [
+            'FOO' => 'bar',
+            'BAZ' => 123,
+        ];
+
+        $config = new Config();
+        $config->load($env);
+        $config->set('FOO', 'asdf');
+
+        $this->assertSame($env, $config->all());
+    }
+
+    public function testForcedOverride(): void {
+        $env = [
+            'FOO' => 'bar',
+            'BAZ' => 123,
+        ];
+
+        $config = new Config();
+        $config->load($env);
+        $config->set('FOO', 'asdf', true);
+
+        $new_env = [
+            'FOO' => 'asdf',
+            'BAZ' => 123,
+        ];
+
+        $this->assertSame($new_env, $config->all());
+    }
 }