diff --git a/README.md b/README.md
index a5d606c..6c54e2f 100644
--- a/README.md
+++ b/README.md
@@ -3,8 +3,8 @@
 **Contributors:** octanist
 **Tags:** tracking, analytics, forms, leads, conversions
 **Requires at least:** 6.0
-**Tested up to:** 7.0
-**Stable tag:** 4.0.1
+**Tested up to:** 7.1
+**Stable tag:** 4.1.0
 **License:** GPLv2 or later
 **License URI:** https://www.gnu.org/licenses/gpl-2.0.html
 
@@ -20,6 +20,7 @@ The plugin acts as a first-party proxy for the Octanist pixel:
 
 - **Pixel proxy:** The tracking script is served from your own WordPress site at `/wp-json/oct/p` from a local cache, with refreshes handled in the background.
 - **Event proxy:** Events from the pixel POST to `/wp-json/oct/e`; the plugin forwards them immediately with a one-second upstream timeout so onboarding and live reporting stay responsive. Pixel failures are not persisted in WordPress, which prevents an upstream outage from filling the site database.
+- **Call tracking proxy:** The pixel can request a dynamic number at `/wp-json/oct/call-tracking/assign`. The plugin forwards that request to Octanist so website numbers stay first-party.
 - **Server-side form capture:** Form submissions from supported plugins are captured via server-side action hooks and forwarded synchronously with a longer timeout. Confirmed failures are queued for retry.
 
 Supported form plugins:
@@ -46,6 +47,13 @@ Listener mode and consent mode are optional settings.
 
 ## Changelog
 
+### 4.1.0
+
+- Added an optional Call tracking setting, off by default.
+- Added a first-party proxy for call tracking assignment (`POST /wp-json/oct/call-tracking/assign`).
+- Setup codes can include a call tracking flag (`OCTA1.OCT-XXXXXXXX.s.a.t`).
+- Tested up to WordPress 7.1.
+
 ### 4.0.1
 
 - Pixel serving now uses the local cache immediately and refreshes upstream in the background.
diff --git a/includes/class-octanist-api.php b/includes/class-octanist-api.php
index b81abb8..a48c4e9 100644
--- a/includes/class-octanist-api.php
+++ b/includes/class-octanist-api.php
@@ -8,8 +8,10 @@ class Octanist_Api
     const COOKIE_PREFIX     = 'octa_';
     const PIXEL_PATH        = '/p';
     const EVENT_PATH        = '/e';
+    const ASSIGN_PATH       = '/call-tracking/assign';
     const PIXEL_TIMEOUT     = 1;
     const COLLECT_TIMEOUT   = 1;
+    const ASSIGN_TIMEOUT    = 8;
     const FORM_TIMEOUT      = 10;
     const RETRY_TIMEOUT     = 3;
     const FORWARD_TIMEOUT   = 1;
@@ -145,6 +147,38 @@ public static function forward_event(array $payload, array $opts = [])
         return $response;
     }
 
+    /**
+     * Forward a DNI assignment request to the upstream /call-tracking/assign endpoint.
+     * Blocking: the pixel needs the leased number in the same request.
+     */
+    public static function forward_call_tracking_assignment(array $payload, array $signals = [])
+    {
+        $headers = [
+            'Content-Type' => 'application/json',
+        ];
+
+        if (!empty($signals['ip'])) {
+            $headers['X-Forwarded-For']           = $signals['ip'];
+            $headers['X-Octanist-Client-IP']      = $signals['ip'];
+        }
+        if (!empty($signals['country'])) {
+            $headers['X-Octanist-Client-Country'] = $signals['country'];
+        }
+        if (!empty($signals['ua'])) {
+            $headers['X-Octanist-Client-UA']      = $signals['ua'];
+        }
+
+        return wp_remote_post(OCTANIST_UPSTREAM . self::ASSIGN_PATH, [
+            'method'              => 'POST',
+            'timeout'             => self::ASSIGN_TIMEOUT,
+            'redirection'         => 0,
+            'blocking'            => true,
+            'headers'             => $headers,
+            'body'                => wp_json_encode($payload),
+            'limit_response_size' => 4096,
+        ]);
+    }
+
     public static function pixel_delivery_is_paused(): bool
     {
         return (bool) get_transient(self::PIXEL_CIRCUIT_TRANSIENT);
diff --git a/includes/class-octanist-rest.php b/includes/class-octanist-rest.php
index f368d50..d5869aa 100644
--- a/includes/class-octanist-rest.php
+++ b/includes/class-octanist-rest.php
@@ -8,6 +8,7 @@ class Octanist_Rest
     const NAMESPACE  = 'oct';
     const PIXEL      = 'p';
     const COLLECT    = 'e';
+    const ASSIGN     = 'call-tracking/assign';
     const MAX_BODY   = 65536; // 64 KB
 
     public static function register(): void
@@ -28,6 +29,12 @@ public static function register_routes(): void
             'callback'            => [__CLASS__, 'collect'],
             'permission_callback' => '__return_true',
         ]);
+
+        register_rest_route(self::NAMESPACE, '/' . self::ASSIGN, [
+            'methods'             => 'POST',
+            'callback'            => [__CLASS__, 'assign'],
+            'permission_callback' => '__return_true',
+        ]);
     }
 
     public static function pixel_url(): string
@@ -169,6 +176,50 @@ public static function collect(WP_REST_Request $request)
         return $rest_response;
     }
 
+    public static function assign(WP_REST_Request $request)
+    {
+        $raw = $request->get_body();
+        if (strlen($raw) > self::MAX_BODY) {
+            return self::assignment_unavailable();
+        }
+
+        $payload = json_decode($raw, true);
+        if (!is_array($payload)) {
+            return new WP_REST_Response(null, 400);
+        }
+
+        $settings = Octanist_Settings::get();
+        if (!empty($settings['measurement_id']) && empty($payload['mid'])) {
+            $payload['mid'] = $settings['measurement_id'];
+        }
+
+        $signals = Octanist_Api::collect_client_signals();
+        $response = Octanist_Api::forward_call_tracking_assignment($payload, $signals);
+
+        if (is_wp_error($response)) {
+            return self::assignment_unavailable();
+        }
+
+        $code = (int) wp_remote_retrieve_response_code($response);
+        $body = json_decode((string) wp_remote_retrieve_body($response), true);
+        if (!is_array($body)) {
+            return self::assignment_unavailable();
+        }
+
+        return new WP_REST_Response($body, $code >= 200 && $code < 600 ? $code : 200);
+    }
+
+    private static function assignment_unavailable(): WP_REST_Response
+    {
+        return new WP_REST_Response([
+            'success'     => false,
+            'enabled'     => false,
+            'available'   => false,
+            'phoneNumber' => null,
+            'reason'      => 'assignment_unavailable',
+        ], 200);
+    }
+
     private static function send_headers(array $headers): void
     {
         foreach ($headers as $name => $value) {
diff --git a/includes/class-octanist-settings.php b/includes/class-octanist-settings.php
index e9ba738..1560259 100644
--- a/includes/class-octanist-settings.php
+++ b/includes/class-octanist-settings.php
@@ -26,6 +26,7 @@ public static function get(): array
             'measurement_id' => '',
             'listener_mode'  => 'server',
             'consent_mode'   => 'auto',
+            'call_tracking'  => false,
         ];
         $settings = get_option(self::OPTION, []);
         if (!is_array($settings)) {
@@ -52,6 +53,9 @@ public static function pixel_data_attrs(): array
             'data-consent-mode' => $s['consent_mode'],
             'data-cookie-mode'  => 'server',
         ];
+        if (!empty($s['call_tracking'])) {
+            $attrs['data-call-tracking'] = 'true';
+        }
         if ($s['listener_mode'] === 'client') {
             // Value-less attribute, browser pixel binds to forms itself.
             $attrs['data-forms'] = '';
@@ -92,6 +96,7 @@ public static function register_settings(): void
                 'measurement_id' => '',
                 'listener_mode'  => 'server',
                 'consent_mode'   => 'auto',
+                'call_tracking'  => false,
             ],
         ]);
     }
@@ -116,6 +121,9 @@ public static function sanitize($input): array
                 $input['measurement_id'] = $decoded['measurement_id'];
                 $input['listener_mode']  = $decoded['listener_mode'];
                 $input['consent_mode']   = $decoded['consent_mode'];
+                if (array_key_exists('call_tracking', $decoded)) {
+                    $input['call_tracking'] = $decoded['call_tracking'];
+                }
 
                 add_settings_error(
                     self::OPTION,
@@ -149,6 +157,7 @@ public static function sanitize($input): array
             'measurement_id' => $mid,
             'listener_mode'  => $listener,
             'consent_mode'   => $consent,
+            'call_tracking'  => !empty($input['call_tracking']),
         ];
     }
 
@@ -166,7 +175,7 @@ private static function decode_setup_code(string $code)
         }
 
         $parts = explode('.', $code);
-        if (count($parts) !== 4) {
+        if (count($parts) !== 4 && count($parts) !== 5) {
             return new WP_Error(
                 'octanist_setup_code_shape',
                 __('Setup code should look like OCTA1.OCT-XXXXXXXX.s.a.', 'octanist')
@@ -211,11 +220,24 @@ private static function decode_setup_code(string $code)
             );
         }
 
-        return [
+        $decoded = [
             'measurement_id' => $measurement_id,
             'listener_mode'  => $listener_mode,
             'consent_mode'   => $consent_mode,
         ];
+
+        if (isset($parts[4])) {
+            $call_code = sanitize_key((string) $parts[4]);
+            if (!in_array($call_code, ['t', 'n'], true)) {
+                return new WP_Error(
+                    'octanist_setup_code_call_tracking',
+                    __('Setup code contains an invalid call tracking flag.', 'octanist')
+                );
+            }
+            $decoded['call_tracking'] = $call_code === 't';
+        }
+
+        return $decoded;
     }
 
     public static function enqueue_assets($hook): void
@@ -362,6 +384,11 @@ class="octanist-input octanist-input--wide"
                                         <dd><?php echo esc_html(self::format_consent_mode($settings['consent_mode'])); ?></dd>
                                         <span><?php echo esc_html(self::format_consent_mode_help($settings['consent_mode'])); ?></span>
                                     </div>
+                                    <div class="octanist-summary-tile">
+                                        <dt><?php esc_html_e('Call tracking', 'octanist'); ?></dt>
+                                        <dd><?php echo esc_html(self::format_call_tracking($settings['call_tracking'])); ?></dd>
+                                        <span><?php echo esc_html(self::format_call_tracking_help($settings['call_tracking'])); ?></span>
+                                    </div>
                                 </dl>
                             </div>
 
@@ -413,6 +440,18 @@ class="octanist-input"
                                                 <option value="denied" <?php selected($settings['consent_mode'], 'denied'); ?>><?php esc_html_e('Denied, always off', 'octanist'); ?></option>
                                             </select>
                                         </label>
+
+                                        <div class="octanist-field">
+                                            <span class="octanist-field__label"><?php esc_html_e('Call tracking', 'octanist'); ?></span>
+                                            <input type="hidden" name="<?php echo esc_attr(self::OPTION); ?>[call_tracking]" value="0">
+                                            <label class="octanist-option <?php echo !empty($settings['call_tracking']) ? 'is-active' : ''; ?>">
+                                                <input type="checkbox" name="<?php echo esc_attr(self::OPTION); ?>[call_tracking]" value="1" <?php checked(!empty($settings['call_tracking'])); ?>>
+                                                <span class="octanist-option__content">
+                                                    <span class="octanist-option__title"><?php esc_html_e('Replace website phone numbers', 'octanist'); ?></span>
+                                                    <span class="octanist-option__desc"><?php esc_html_e('Turn this on after Octanist has enabled call tracking for this site.', 'octanist'); ?></span>
+                                                </span>
+                                            </label>
+                                        </div>
                                     </div>
                                 </details>
 
@@ -428,7 +467,7 @@ class="octanist-input octanist-input--wide"
                                             autocomplete="off"
                                             spellcheck="false"
                                             aria-label="<?php esc_attr_e('Setup code', 'octanist'); ?>">
-                                        <p class="octanist-help"><?php esc_html_e('Saving a setup code replaces the current measurement ID, form capture mode, and consent mode.', 'octanist'); ?></p>
+                                        <p class="octanist-help"><?php esc_html_e('Saving a setup code replaces the current measurement ID, form capture mode, consent mode, and call tracking setting when the code includes that flag.', 'octanist'); ?></p>
                                     </div>
                                 </details>
                             </div>
@@ -530,6 +569,20 @@ private static function format_consent_mode_help(string $mode): string
         return $labels[$mode] ?? $labels['auto'];
     }
 
+    private static function format_call_tracking($enabled): string
+    {
+        return !empty($enabled)
+            ? __('On', 'octanist')
+            : __('Off', 'octanist');
+    }
+
+    private static function format_call_tracking_help($enabled): string
+    {
+        return !empty($enabled)
+            ? __('The pixel can replace website phone numbers.', 'octanist')
+            : __('Leave this off unless Octanist enabled call tracking for this site.', 'octanist');
+    }
+
     private static function format_time($ts): string
     {
         if (empty($ts)) {
diff --git a/languages/octanist.pot b/languages/octanist.pot
index e2f38d7..e194c4a 100644
--- a/languages/octanist.pot
+++ b/languages/octanist.pot
@@ -2,7 +2,7 @@
 # This file is distributed under the same license as the Octanist plugin.
 msgid ""
 msgstr ""
-"Project-Id-Version: Octanist 4.0.1\n"
+"Project-Id-Version: Octanist 4.1.0\n"
 "Report-Msgid-Bugs-To: https://wordpress.org/support/plugin/octanist\n"
 "POT-Creation-Date: 2026-06-08 08:31+0000\n"
 "MIME-Version: 1.0\n"
diff --git a/octanist.php b/octanist.php
index ca6aad1..fe13561 100644
--- a/octanist.php
+++ b/octanist.php
@@ -1,22 +1,22 @@
 <?php
 /**
  * Plugin Name:         Octanist
- * Description:         First-party proxy for the Octanist pixel. Serves the tracking script, forwards events, and captures form submissions server-side from popular form plugins.
- * Version:             4.0.1
+ * Description:         First-party proxy for the Octanist pixel. Serves the tracking script, forwards events and call-tracking assignments, and captures form submissions server-side from popular form plugins.
+ * Version:             4.1.0
  * Author:              Octanist
  * Author URI:          https://www.octanist.com/
  * Text Domain:         octanist
  * License:             GPLv2 or later
  * License URI:         https://www.gnu.org/licenses/gpl-2.0.html
  * Requires at least:   6.0
- * Tested up to:        7.0
+ * Tested up to:        7.1
  */
 
 if (!defined('ABSPATH')) {
     exit;
 }
 
-define('OCTANIST_VERSION', '4.0.1');
+define('OCTANIST_VERSION', '4.1.0');
 define('OCTANIST_PATH', plugin_dir_path(__FILE__));
 define('OCTANIST_URL', plugin_dir_url(__FILE__));
 define('OCTANIST_FILE', __FILE__);
diff --git a/package-lock.json b/package-lock.json
index d25d3cd..158f584 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "octanist-wp-plugin",
-  "version": "4.0.1",
+  "version": "4.1.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "octanist-wp-plugin",
-      "version": "4.0.1",
+      "version": "4.1.0",
       "devDependencies": {
         "@wordpress/env": "^10.0.0"
       }
diff --git a/package.json b/package.json
index c5117cf..951723d 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "octanist-wp-plugin",
   "private": true,
-  "version": "4.0.1",
+  "version": "4.1.0",
   "description": "Development tooling for the Octanist WordPress plugin.",
   "scripts": {
     "start": "wp-env start",
diff --git a/readme.txt b/readme.txt
index 5882d0a..a2ec859 100644
--- a/readme.txt
+++ b/readme.txt
@@ -2,8 +2,8 @@
 Contributors: octanist
 Tags: tracking, analytics, forms, leads, conversions
 Requires at least: 6.0
-Tested up to: 7.0
-Stable tag: 4.0.1
+Tested up to: 7.1
+Stable tag: 4.1.0
 License: GPLv2 or later
 License URI: https://www.gnu.org/licenses/gpl-2.0.html
 
@@ -19,6 +19,7 @@ The plugin acts as a first-party proxy for the Octanist pixel:
 
 *   **Pixel proxy.** The tracking script is served from your own WordPress site (`/wp-json/oct/p`) from a local cache and refreshed from Octanist in the background. No third-party domain, no DNS setup, no ad-blocker signal to match on.
 *   **Event proxy.** Events from the pixel POST to `/wp-json/oct/e`; the plugin forwards them immediately with a one-second upstream timeout so onboarding and live reporting stay responsive. Pixel failures are not persisted in WordPress, which prevents an upstream outage from filling the site database.
+*   **Call tracking proxy.** The pixel can request a dynamic number at `/wp-json/oct/call-tracking/assign`. The plugin forwards that request to Octanist so website phone numbers stay first-party.
 *   **Server-side form capture.** Form submissions from Gravity Forms, Contact Form 7, WPForms, Ninja Forms, Elementor Pro, Fluent Forms, Formidable Forms, Forminator, SureForms, and Divi Contact Form are captured server-side via action hooks and forwarded synchronously with a longer timeout. Confirmed failures are queued for retry.
 
 ### Setup
@@ -61,6 +62,12 @@ Pixel events are forwarded immediately through the first-party WordPress endpoin
 
 == Changelog ==
 
+= 4.1.0 =
+*   **NEW:** Optional call tracking setting (off by default). When enabled, the pixel can replace website phone numbers.
+*   **NEW:** First-party proxy for call tracking assignment (`POST /wp-json/oct/call-tracking/assign`).
+*   **NEW:** Setup codes can include a call tracking flag (`OCTA1.OCT-XXXXXXXX.s.a.t`).
+*   **COMPATIBILITY:** Tested up to WordPress 7.1.
+
 = 4.0.1 =
 *   **PERFORMANCE:** The pixel endpoint serves its local cache immediately and refreshes Octanist upstream in the background.
 *   **UPGRADE:** Existing v4 caches are migrated and refreshed through a non-blocking runtime upgrade routine.