diff --git a/README.de.md b/README.de.md
index 66f0b89..e4fe721 100644
--- a/README.de.md
+++ b/README.de.md
@@ -300,10 +300,11 @@ Kein `openssl_*` oder externe Extension nötig — läuft auf jeder PHP 8.0+ Ins
 **Sicherheitsgrenzen:** XOR mit statischem Salt ist Verschleierung, keine kryptografische Verschlüsselung. Für maximale Sicherheit können Keys als `wp-config.php`-Konstanten definiert werden:
 
 ```php
-define( 'BREZNGEO_OPENAI_KEY',    'sk-...' );
-define( 'BREZNGEO_ANTHROPIC_KEY', 'sk-ant-...' );
-define( 'BREZNGEO_GEMINI_KEY',    'AI...' );
-define( 'BREZNGEO_GROK_KEY',      'xai-...' );
+define( 'BREZNGEO_OPENAI_KEY',     'sk-...' );
+define( 'BREZNGEO_ANTHROPIC_KEY',  'sk-ant-...' );
+define( 'BREZNGEO_GEMINI_KEY',     'AI...' );
+define( 'BREZNGEO_GROK_KEY',       'xai-...' );
+define( 'BREZNGEO_OPENROUTER_KEY', 'sk-or-...' );
 ```
 
 ### CSRF-Schutz und Capability Checks
diff --git a/README.md b/README.md
index 7edf5a4..156eea8 100644
--- a/README.md
+++ b/README.md
@@ -409,10 +409,11 @@ Plaintext key  →  XOR(key, sha256(AUTH_KEY . SECURE_AUTH_KEY))  →  base64  
 **Security boundary:** XOR with a static salt is obfuscation, not cryptographic encryption. An attacker with access to **both** the database **and** `wp-config.php` can reconstruct the key. For maximum security, keys can be defined as `wp-config.php` constants — these take precedence over the database version:
 
 ```php
-define( 'BREZNGEO_OPENAI_KEY',    'sk-...' );
-define( 'BREZNGEO_ANTHROPIC_KEY', 'sk-ant-...' );
-define( 'BREZNGEO_GEMINI_KEY',    'AI...' );
-define( 'BREZNGEO_GROK_KEY',      'xai-...' );
+define( 'BREZNGEO_OPENAI_KEY',     'sk-...' );
+define( 'BREZNGEO_ANTHROPIC_KEY',  'sk-ant-...' );
+define( 'BREZNGEO_GEMINI_KEY',     'AI...' );
+define( 'BREZNGEO_GROK_KEY',       'xai-...' );
+define( 'BREZNGEO_OPENROUTER_KEY', 'sk-or-...' );
 ```
 
 In the admin UI, keys are always displayed masked: `••••••Ab3c9` (only the last 5 characters visible).
diff --git a/brezngeo/includes/Admin/ProviderPage.php b/brezngeo/includes/Admin/ProviderPage.php
index 37b46cb..568b516 100644
--- a/brezngeo/includes/Admin/ProviderPage.php
+++ b/brezngeo/includes/Admin/ProviderPage.php
@@ -74,6 +74,13 @@ class ProviderPage {
 				$clean['api_keys'][ $provider_id ] = $existing['api_keys'][ $provider_id ];
 			}
 		}
+		// Preserve DB-stored keys for providers whose UI field was disabled
+		// (wp-config.php constant override) and therefore never submitted.
+		foreach ( ( $existing['api_keys'] ?? array() ) as $provider_id => $stored ) {
+			if ( ! isset( $clean['api_keys'][ $provider_id ] ) ) {
+				$clean['api_keys'][ $provider_id ] = $stored;
+			}
+		}
 
 		$clean['models'] = array();
 		foreach ( ( $input['models'] ?? array() ) as $provider_id => $model ) {
diff --git a/brezngeo/includes/Admin/SettingsPage.php b/brezngeo/includes/Admin/SettingsPage.php
index 68eeed9..ea0da93 100644
--- a/brezngeo/includes/Admin/SettingsPage.php
+++ b/brezngeo/includes/Admin/SettingsPage.php
@@ -23,6 +23,12 @@ class SettingsPage {
 	 */
 	public const OPTION_KEY_SCHEMA = 'brezngeo_schema_settings';
 
+	/**
+	 * Provider IDs that support a wp-config.php constant override.
+	 * A defined constant wins over the DB value and locks the UI field.
+	 */
+	private const CONSTANT_KEY_PROVIDERS = array( 'openai', 'anthropic', 'gemini', 'grok', 'openrouter' );
+
 	/**
 	 * Returns merged settings from both option keys with defaults applied.
 	 * Called by MetaGenerator, SchemaEnhancer, BulkPage, and admin pages.
@@ -62,9 +68,37 @@ class SettingsPage {
 			$settings['api_keys'][ $id ] = $decrypted !== '' ? $decrypted : $stored;
 		}
 
+		// wp-config.php constants override the DB value and lock the admin field.
+		$settings['api_keys_locked'] = array();
+		foreach ( self::CONSTANT_KEY_PROVIDERS as $provider_id ) {
+			$constant = self::constantNameForProvider( $provider_id );
+			if ( $constant !== '' && defined( $constant ) ) {
+				$settings['api_keys'][ $provider_id ]        = (string) constant( $constant );
+				$settings['api_keys_locked'][ $provider_id ] = true;
+			}
+		}
+
 		return $settings;
 	}
 
+	/**
+	 * Returns the wp-config.php constant name for a given provider ID,
+	 * or empty string if the provider has no constant override.
+	 *
+	 * Must be pure — no WP hooks, no option reads. Called once per entry
+	 * in CONSTANT_KEY_PROVIDERS during getSettings().
+	 *
+	 * The website (de/index.html, howto.html) already promises the names
+	 * BREZNGEO_OPENAI_KEY, BREZNGEO_ANTHROPIC_KEY, BREZNGEO_GEMINI_KEY,
+	 * BREZNGEO_GROK_KEY and BREZNGEO_OPENROUTER_KEY — those are the contract.
+	 */
+	private static function constantNameForProvider( string $provider_id ): string {
+		if ( ! in_array( $provider_id, self::CONSTANT_KEY_PROVIDERS, true ) ) {
+			return '';
+		}
+		return 'BREZNGEO_' . strtoupper( $provider_id ) . '_KEY';
+	}
+
 	public static function getDefaultPrompt(): string {
 		$locale    = get_locale();
 		$is_german = str_starts_with( $locale, 'de_' );
diff --git a/brezngeo/includes/Admin/views/partials/openrouter-model-field.php b/brezngeo/includes/Admin/views/partials/openrouter-model-field.php
index d6fe1a9..5ef5e5e 100644
--- a/brezngeo/includes/Admin/views/partials/openrouter-model-field.php
+++ b/brezngeo/includes/Admin/views/partials/openrouter-model-field.php
@@ -9,31 +9,31 @@ if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }
 
-$or_models           = $provider->getModels();
-$or_saved_model      = $settings['models']['openrouter'] ?? '';
-$or_is_custom        = $or_saved_model !== '' && ! array_key_exists( $or_saved_model, $or_models );
-$or_cached_pricing   = get_transient( \BreznGEO\Providers\OpenRouterProvider::MODELS_CACHE );
-$or_cache_is_array   = is_array( $or_cached_pricing );
-$or_selected_pricing = ( $or_cache_is_array && isset( $or_cached_pricing[ $or_saved_model ] ) )
-	? $or_cached_pricing[ $or_saved_model ]
+$brezngeo_or_models           = $provider->getModels();
+$brezngeo_or_saved_model      = $settings['models']['openrouter'] ?? '';
+$brezngeo_or_is_custom        = $brezngeo_or_saved_model !== '' && ! array_key_exists( $brezngeo_or_saved_model, $brezngeo_or_models );
+$brezngeo_or_cached_pricing   = get_transient( \BreznGEO\Providers\OpenRouterProvider::MODELS_CACHE );
+$brezngeo_or_cache_is_array   = is_array( $brezngeo_or_cached_pricing );
+$brezngeo_or_selected_pricing = ( $brezngeo_or_cache_is_array && isset( $brezngeo_or_cached_pricing[ $brezngeo_or_saved_model ] ) )
+	? $brezngeo_or_cached_pricing[ $brezngeo_or_saved_model ]
 	: null;
 ?>
 <br><br>
 <label><?php esc_html_e( 'Model:', 'brezngeo' ); ?></label>
 <select name="brezngeo_settings[models][openrouter]" class="brezngeo-openrouter-model-select" id="brezngeo-openrouter-model">
-	<?php if ( empty( $or_models ) ) : ?>
+	<?php if ( empty( $brezngeo_or_models ) ) : ?>
 		<option value=""><?php esc_html_e( 'No models loaded yet — click "Load models"', 'brezngeo' ); ?></option>
 	<?php else : ?>
-		<?php foreach ( $or_models as $or_mid => $or_label ) : ?>
-			<option value="<?php echo esc_attr( $or_mid ); ?>"
-				<?php selected( $or_saved_model, $or_mid ); ?>
-				data-input="<?php echo esc_attr( isset( $or_cached_pricing[ $or_mid ]['input_cost'] ) ? $or_cached_pricing[ $or_mid ]['input_cost'] : '' ); ?>"
-				data-output="<?php echo esc_attr( isset( $or_cached_pricing[ $or_mid ]['output_cost'] ) ? $or_cached_pricing[ $or_mid ]['output_cost'] : '' ); ?>">
-				<?php echo esc_html( $or_label ); ?>
+		<?php foreach ( $brezngeo_or_models as $brezngeo_or_mid => $brezngeo_or_label ) : ?>
+			<option value="<?php echo esc_attr( $brezngeo_or_mid ); ?>"
+				<?php selected( $brezngeo_or_saved_model, $brezngeo_or_mid ); ?>
+				data-input="<?php echo esc_attr( isset( $brezngeo_or_cached_pricing[ $brezngeo_or_mid ]['input_cost'] ) ? $brezngeo_or_cached_pricing[ $brezngeo_or_mid ]['input_cost'] : '' ); ?>"
+				data-output="<?php echo esc_attr( isset( $brezngeo_or_cached_pricing[ $brezngeo_or_mid ]['output_cost'] ) ? $brezngeo_or_cached_pricing[ $brezngeo_or_mid ]['output_cost'] : '' ); ?>">
+				<?php echo esc_html( $brezngeo_or_label ); ?>
 			</option>
 		<?php endforeach; ?>
 	<?php endif; ?>
-	<option value="__custom__" <?php selected( $or_is_custom ); ?>>
+	<option value="__custom__" <?php selected( $brezngeo_or_is_custom ); ?>>
 		<?php esc_html_e( 'Custom model ID…', 'brezngeo' ); ?>
 	</option>
 </select>
@@ -42,14 +42,14 @@ $or_selected_pricing = ( $or_cache_is_array && isset( $or_cached_pricing[ $or_sa
 </button>
 <span class="brezngeo-openrouter-load-status" aria-live="polite"></span>
 
-<div class="brezngeo-openrouter-custom-wrap" style="<?php echo $or_is_custom ? '' : 'display:none;'; ?>margin-top:10px;">
+<div class="brezngeo-openrouter-custom-wrap" style="<?php echo $brezngeo_or_is_custom ? '' : 'display:none;'; ?>margin-top:10px;">
 	<label for="brezngeo-openrouter-custom">
 		<?php esc_html_e( 'Custom model ID:', 'brezngeo' ); ?>
 	</label>
 	<input type="text"
 			id="brezngeo-openrouter-custom"
 			name="brezngeo_settings[openrouter_custom_model]"
-			value="<?php echo esc_attr( $or_is_custom ? $or_saved_model : '' ); ?>"
+			value="<?php echo esc_attr( $brezngeo_or_is_custom ? $brezngeo_or_saved_model : '' ); ?>"
 			placeholder="<?php esc_attr_e( 'e.g. anthropic/claude-opus-4.7', 'brezngeo' ); ?>"
 			class="regular-text">
 	<p class="description">
@@ -69,11 +69,11 @@ $or_selected_pricing = ( $or_cache_is_array && isset( $or_cached_pricing[ $or_sa
 
 <p style="margin-top:12px;"><strong><?php esc_html_e( 'Pricing (automatically from OpenRouter, per 1M tokens):', 'brezngeo' ); ?></strong></p>
 <div class="brezngeo-openrouter-pricing-display" id="brezngeo-openrouter-pricing" style="font-size:12px;color:#555;">
-	<?php if ( $or_selected_pricing ) : ?>
-		Input $<span class="or-price-input"><?php echo esc_html( number_format( (float) $or_selected_pricing['input_cost'], 4 ) ); ?></span>
-		/ 1M · Output $<span class="or-price-output"><?php echo esc_html( number_format( (float) $or_selected_pricing['output_cost'], 4 ) ); ?></span>
+	<?php if ( $brezngeo_or_selected_pricing ) : ?>
+		Input $<span class="or-price-input"><?php echo esc_html( number_format( (float) $brezngeo_or_selected_pricing['input_cost'], 4 ) ); ?></span>
+		/ 1M · Output $<span class="or-price-output"><?php echo esc_html( number_format( (float) $brezngeo_or_selected_pricing['output_cost'], 4 ) ); ?></span>
 		/ 1M
-	<?php elseif ( $or_is_custom ) : ?>
+	<?php elseif ( $brezngeo_or_is_custom ) : ?>
 		<em><?php esc_html_e( 'Pricing unknown for custom models — will be populated after you click "Load models".', 'brezngeo' ); ?></em>
 	<?php else : ?>
 		<em><?php esc_html_e( 'Click "Load models" to fetch pricing from OpenRouter.', 'brezngeo' ); ?></em>
diff --git a/brezngeo/includes/Admin/views/provider.php b/brezngeo/includes/Admin/views/provider.php
index de65d19..a364938 100644
--- a/brezngeo/includes/Admin/views/provider.php
+++ b/brezngeo/includes/Admin/views/provider.php
@@ -36,9 +36,26 @@
 				</td>
 			</tr>
 			<?php foreach ( $providers as $id => $provider ) : // phpcs:ignore WordPress.NamingConventions.PrefixAllGlobals.NonPrefixedVariableFound ?>
+			<?php $locked = ! empty( $settings['api_keys_locked'][ $id ] ); ?>
 			<tr class="brezngeo-provider-row" data-provider="<?php echo esc_attr( $id ); ?>">
 				<th scope="row"><?php echo esc_html( $provider->getName() ); ?> <?php esc_html_e( 'API Key', 'brezngeo' ); ?></th>
 				<td>
+					<?php if ( $locked ) : ?>
+					<span class="brezngeo-key-saved">
+						<?php
+						printf(
+							/* translators: %s: wp-config.php constant name */
+							esc_html__( 'Loaded from wp-config.php: %s', 'brezngeo' ),
+							'<code>BREZNGEO_' . esc_html( strtoupper( $id ) ) . '_KEY</code>'
+						);
+						?>
+					</span><br>
+					<input type="password" value="" placeholder="&#8212;" class="regular-text" disabled>
+					<button type="button" class="button brezngeo-test-btn" data-provider="<?php echo esc_attr( $id ); ?>">
+						<?php esc_html_e( 'Test connection', 'brezngeo' ); ?>
+					</button>
+					<span class="brezngeo-test-result" id="test-result-<?php echo esc_attr( $id ); ?>"></span>
+					<?php else : ?>
 					<?php if ( ! empty( $masked_keys[ $id ] ) ) : ?>
 					<span class="brezngeo-key-saved">
 						<?php esc_html_e( 'Saved:', 'brezngeo' ); ?> <code><?php echo esc_html( $masked_keys[ $id ] ); ?></code>
@@ -54,6 +71,7 @@
 						<?php esc_html_e( 'Test connection', 'brezngeo' ); ?>
 					</button>
 					<span class="brezngeo-test-result" id="test-result-<?php echo esc_attr( $id ); ?>"></span>
+					<?php endif; ?>
 					<?php if ( $id === 'openrouter' ) : ?>
 						<?php include BREZNGEO_DIR . 'includes/Admin/views/partials/openrouter-model-field.php'; ?>
 					<?php else : ?>
diff --git a/brezngeo/readme.txt b/brezngeo/readme.txt
index f038a72..0f3badc 100644
--- a/brezngeo/readme.txt
+++ b/brezngeo/readme.txt
@@ -237,6 +237,7 @@ No data is transmitted during normal page loads or to visitors.
 * New: OpenRouter as a fifth AI provider — access to 600+ models (Claude, GPT, Gemini, Llama, Mistral, DeepSeek, and more) through a single API key.
 * New: On-demand model loader fetches OpenRouter's curated Marketing/SEO model list with live per-model pricing.
 * New: Custom model ID field lets you route to any OpenRouter model (e.g. anthropic/claude-opus-4.7) without waiting for a plugin update.
+* New: OpenRouter joins the wp-config.php key-mapping (BREZNGEO_OPENROUTER_KEY) — define any provider key as a constant to keep it out of the database entirely; the admin field becomes read-only.
 
 = 1.2.2 =
 * i18n: Added explicit load_plugin_textdomain() call for reliable translation loading on ClassicPress and other WordPress derivatives.