diff --git a/.github/workflows/generate.yml b/.github/workflows/generate.yml
index 4020d103..8f32a533 100644
--- a/.github/workflows/generate.yml
+++ b/.github/workflows/generate.yml
@@ -50,6 +50,81 @@ jobs:
             --git-user-id=zernio-dev \
             --git-repo-id=zernio-php
 
+      - name: Patch Configuration.php to use versioned User-Agent
+        run: |
+          # Rewrite the generated OpenAPI-Generator user agent default so it
+          # resolves to "zernio-php/<composer.json version>/PHP" at runtime.
+          # Keeps the SDK version visible to the API without depending on
+          # generation-time knowledge of the next version bump.
+          python3 - <<'PY'
+          import re, sys
+
+          path = 'lib/Configuration.php'
+          with open(path) as f:
+              src = f.read()
+
+          new_prop = (
+              "    /**\n"
+              "     * User agent of the HTTP request. Defaults to \"zernio-php/{composer.json version}/PHP\",\n"
+              "     * resolved lazily the first time getUserAgent() is called.\n"
+              "     *\n"
+              "     * @var string|null\n"
+              "     */\n"
+              "    protected \$userAgent = null;"
+          )
+          src, n = re.subn(
+              r"    /\*\*\n     \* User agent of the HTTP request[\s\S]*?protected \$userAgent = '[^']*';",
+              lambda m: new_prop,
+              src,
+              count=1,
+          )
+          if n != 1:
+              sys.exit('Failed to patch $userAgent property')
+
+          new_getter = (
+              "    public function getUserAgent()\n"
+              "    {\n"
+              "        if (\$this->userAgent === null) {\n"
+              "            \$this->userAgent = self::defaultUserAgent();\n"
+              "        }\n"
+              "        return \$this->userAgent;\n"
+              "    }\n"
+              "\n"
+              "    /**\n"
+              "     * Builds the default user agent string from the package's composer.json version.\n"
+              "     *\n"
+              "     * @return string\n"
+              "     */\n"
+              "    private static function defaultUserAgent()\n"
+              "    {\n"
+              "        static \$cached = null;\n"
+              "        if (\$cached !== null) {\n"
+              "            return \$cached;\n"
+              "        }\n"
+              "        \$version = 'unknown';\n"
+              "        \$composerPath = __DIR__ . '/../composer.json';\n"
+              "        if (is_file(\$composerPath)) {\n"
+              "            \$data = json_decode((string) file_get_contents(\$composerPath), true);\n"
+              "            if (is_array(\$data) && isset(\$data['version']) && is_string(\$data['version'])) {\n"
+              "                \$version = \$data['version'];\n"
+              "            }\n"
+              "        }\n"
+              "        return \$cached = 'zernio-php/' . \$version . '/PHP';\n"
+              "    }"
+          )
+          src, n = re.subn(
+              r"    public function getUserAgent\(\)\n    \{\n        return \$this->userAgent;\n    \}",
+              lambda m: new_getter,
+              src,
+              count=1,
+          )
+          if n != 1:
+              sys.exit('Failed to patch getUserAgent() method')
+
+          with open(path, 'w') as f:
+              f.write(src)
+          PY
+
       - name: Add Late namespace backwards-compat shim
         run: |
           # Register a lazy spl_autoloader that aliases any referenced
diff --git a/lib/Configuration.php b/lib/Configuration.php
index 539281dc..e16f3fd7 100644
--- a/lib/Configuration.php
+++ b/lib/Configuration.php
@@ -97,11 +97,12 @@ class Configuration
     protected $host = 'https://zernio.com/api';
 
     /**
-     * User agent of the HTTP request, set to "OpenAPI-Generator/{version}/PHP" by default
+     * User agent of the HTTP request. Defaults to "zernio-php/{composer.json version}/PHP",
+     * resolved lazily the first time getUserAgent() is called.
      *
-     * @var string
+     * @var string|null
      */
-    protected $userAgent = 'OpenAPI-Generator/1.0.0/PHP';
+    protected $userAgent = null;
 
     /**
      * Debug switch (default set to false)
@@ -339,9 +340,34 @@ public function setUserAgent($userAgent)
      */
     public function getUserAgent()
     {
+        if ($this->userAgent === null) {
+            $this->userAgent = self::defaultUserAgent();
+        }
         return $this->userAgent;
     }
 
+    /**
+     * Builds the default user agent string from the package's composer.json version.
+     *
+     * @return string
+     */
+    private static function defaultUserAgent()
+    {
+        static $cached = null;
+        if ($cached !== null) {
+            return $cached;
+        }
+        $version = 'unknown';
+        $composerPath = __DIR__ . '/../composer.json';
+        if (is_file($composerPath)) {
+            $data = json_decode((string) file_get_contents($composerPath), true);
+            if (is_array($data) && isset($data['version']) && is_string($data['version'])) {
+                $version = $data['version'];
+            }
+        }
+        return $cached = 'zernio-php/' . $version . '/PHP';
+    }
+
     /**
      * Sets debug flag
      *