diff --git a/src/lib/ab-testing/server.ts b/src/lib/ab-testing/server.ts
index 8dd9032787f..51577136a63 100644
--- a/src/lib/ab-testing/server.ts
+++ b/src/lib/ab-testing/server.ts
@@ -28,8 +28,11 @@ export const getABTestAssignment = async (
   const headers = await import("next/headers").then((m) => m.headers())
 
   // Get IP and user agent (primary identifier)
+  // x-forwarded-for contains: "client_ip, proxy1, proxy2, ..." - extract only client IP
   const forwardedFor =
-    headers.get("x-forwarded-for") || headers.get("x-real-ip") || "unknown"
+    headers.get("x-forwarded-for")?.split(",")[0]?.trim() ||
+    headers.get("x-real-ip") ||
+    "unknown"
   const userAgent = headers.get("user-agent") || ""
 
   // Add privacy-preserving entropy sources