diff --git a/backend/utils/clientPatcher.js b/backend/utils/clientPatcher.js
index 8fa9518..33e2df2 100644
--- a/backend/utils/clientPatcher.js
+++ b/backend/utils/clientPatcher.js
@@ -291,12 +291,29 @@ class ClientPatcher {
     }
 
     // 2. Patch main domain (hytale.com -> mainDomain)
+    // Try length-prefixed format first, then fall back to pure UTF-16LE
     console.log(`  Patching domain: ${ORIGINAL_DOMAIN} -> ${strategy.mainDomain}`);
-    const domainResult = this.replaceBytes(
-        result,
-        this.stringToLengthPrefixed(ORIGINAL_DOMAIN),
-        this.stringToLengthPrefixed(strategy.mainDomain)
-    );
+
+    // Check for HYTALE_PATCH_MODE env var to test different formats
+    const patchMode = process.env.HYTALE_PATCH_MODE || 'length-prefixed';
+    console.log(`  Patch mode: ${patchMode}`);
+
+    let domainResult;
+    if (patchMode === 'utf16le') {
+      // Pure UTF-16LE replacement (no length prefix)
+      const oldUtf16 = this.stringToUtf16LE(ORIGINAL_DOMAIN);
+      const newUtf16 = this.stringToUtf16LE(strategy.mainDomain);
+      console.log(`    UTF-16LE: old=${oldUtf16.length} bytes, new=${newUtf16.length} bytes`);
+      domainResult = this.replaceBytes(result, oldUtf16, newUtf16);
+    } else {
+      // Length-prefixed format (default)
+      domainResult = this.replaceBytes(
+          result,
+          this.stringToLengthPrefixed(ORIGINAL_DOMAIN),
+          this.stringToLengthPrefixed(strategy.mainDomain)
+      );
+    }
+
     result = domainResult.buffer;
     if (domainResult.count > 0) {
       console.log(`    Replaced ${domainResult.count} domain occurrence(s)`);