diff --git a/CHANGELOG.md b/CHANGELOG.md
index 569e9ef7b36..d426f81b1aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@
 - Fixed a bug where row headings within Table fields weren’t getting statically translated in the control panel. ([#13703](https://github.com/craftcms/cms/discussions/13703))
 - Fixed a bug where entry type chips within Matrix settings could be missing their action items.
 - Fixed a bug where custom field override settings’ Label, Handle, and Instructions fields could be missing their placeholder values.
+- Fixed a bug where site name and language values set to environment variables were getting replaced with their resolved values when installing Craft. ([#18780](https://github.com/craftcms/cms/issues/18780))
+- Fixed a bug where site name values set to environment variables were getting replaced with their resolved values on save. ([#18789](https://github.com/craftcms/cms/pull/18789))
 
 ## 5.9.22 - 2026-04-29
 
diff --git a/src/migrations/Install.php b/src/migrations/Install.php
index 05422ea8732..45df94c401e 100644
--- a/src/migrations/Install.php
+++ b/src/migrations/Install.php
@@ -1184,7 +1184,7 @@ public function insertDefaultData(): void
             $site = $sitesService->getPrimarySite();
             $site->setBaseUrl($this->site->getBaseUrl(false));
             $site->hasUrls = $this->site->hasUrls;
-            $site->language = $this->site->language;
+            $site->language = $this->site->getLanguage(false);
             $site->setName($this->site->getName(false));
             $sitesService->saveSite($site);
         }
@@ -1322,7 +1322,7 @@ private function _generateInitialConfig(): array
                     'baseUrl' => $this->site->getBaseUrl(false),
                     'handle' => $this->site->handle,
                     'hasUrls' => $this->site->hasUrls,
-                    'language' => $this->site->language,
+                    'language' => $this->site->getLanguage(false),
                     'name' => $this->site->getName(false),
                     'primary' => true,
                     'siteGroup' => $siteGroupUid,
diff --git a/src/models/Site.php b/src/models/Site.php
index 4cf143eb43c..3730087b2d0 100644
--- a/src/models/Site.php
+++ b/src/models/Site.php
@@ -257,13 +257,29 @@ public function attributeLabels(): array
         ];
     }
 
+    /**
+     * @inheritdoc
+     */
+    public function beforeValidate(): bool
+    {
+        if (!parent::beforeValidate()) {
+            return false;
+        }
+
+        // Can't use the `trim` rule because it replaces env vars
+        // see https://github.com/craftcms/cms/pull/18789
+        $this->setName(trim($this->getName(false)));
+
+        return true;
+    }
+
     /**
      * @inheritdoc
      */
     protected function defineRules(): array
     {
         $rules = parent::defineRules();
-        $rules[] = [['name', 'handle'], 'trim'];
+        $rules[] = [['handle'], 'trim'];
         $rules[] = [['groupId', 'name', 'handle', 'language'], 'required'];
         $rules[] = [['id', 'groupId'], 'number', 'integerOnly' => true];
         $rules[] = [['name', 'handle', 'baseUrl'], 'string', 'max' => 255];