From 82cfc8afa79e0e8b0dd5b6c6332c167e4fa9db6e Mon Sep 17 00:00:00 2001
From: MO Thibault <103271673+MO-Thibault@users.noreply.github.com>
Date: Mon, 18 May 2026 14:40:42 -0400
Subject: [PATCH] fix(rtd): use property descriptors for Proxy-safe EID merging

Prebid.js wraps ortb2Fragments in Proxies whose get trap blocks direct
reads of `eids`. Replace direct property access in merge() with
Object.getOwnPropertyDescriptor for reads and Object.defineProperty for
writes to bypass Proxy traps.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 lib/core/prebid/rtd.ts | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/lib/core/prebid/rtd.ts b/lib/core/prebid/rtd.ts
index cd9f350..5f219c3 100644
--- a/lib/core/prebid/rtd.ts
+++ b/lib/core/prebid/rtd.ts
@@ -249,8 +249,12 @@ function merge(config: RTDConfig, targetORTB2: ORTB2, sourceORTB2: ORTB2): numbe
   /* eslint-disable no-param-reassign */
   targetORTB2.user = targetORTB2.user ?? {};
   targetORTB2.user.ext = targetORTB2.user.ext ?? {};
-  targetORTB2.user.ext.eids = targetORTB2.user.ext.eids ?? [];
   /* eslint-enable no-param-reassign */
+
+  // Use Object.getOwnPropertyDescriptor/defineProperty to bypass Prebid's ORTB2
+  // Proxy whose get trap blocks direct reads of `eids`.
+  const eidsDesc = Object.getOwnPropertyDescriptor(targetORTB2.user.ext, "eids");
+  let currentEids: EID[] = Array.isArray(eidsDesc?.value) ? eidsDesc.value : [];
   let skipped = 0;
 
   const eidsBySource =
@@ -267,8 +271,14 @@ function merge(config: RTDConfig, targetORTB2: ORTB2, sourceORTB2: ORTB2): numbe
     }
 
     const mergeFn = mergeStrategy(config, eidSource);
-    // eslint-disable-next-line no-param-reassign
-    targetORTB2.user!.ext!.eids = mergeFn(targetORTB2.user!.ext!.eids!, eids);
+    currentEids = mergeFn(currentEids, eids);
+  });
+
+  Object.defineProperty(targetORTB2.user!.ext!, "eids", {
+    value: currentEids,
+    writable: true,
+    enumerable: true,
+    configurable: true,
   });
   return skipped;
 }