[Performance][iOS] Severe production crash after Firebase 12.16.0 in NSURLSession delegate instrumentation

[codeDancer668]

Description

This is a production crash report related to Firebase iOS SDK issue #16469:
#16469

We are opening a separate issue as requested by Firebase Support, because we are seeing the same crash signature in production after affected apps upgraded to Firebase Apple SDK 12.16.0.

Impact:

• This is a severe production stability issue.
• The crash volume is significant enough to require urgent investigation.
• We need Firebase Performance Monitoring team assistance to confirm the root cause and provide a fix or workaround.

Crash signature:

objc_loadWeakRetained
-[PAGWeakProxy respondsToSelector:]
-[__NSCFURLSessionDelegateWrapper didBecomeInvalidWithError:]
-[NSURLSession finalizeDelegateWithError:]
__NSURLSessionLocal _onqueue_invokeInvalidateCallback

Evidence:

• The crash appeared after affected apps upgraded to Firebase Apple SDK 12.16.0.
• In before/after app comparisons, Firebase / Google measurement components were upgraded to 12.16.0, while the Pangle SDK version and PAGWeakProxy implementation stayed unchanged.
• The crash stack consistently points to:
  objc_loadWeakRetained -> -[PAGWeakProxy respondsToSelector:] -> CFNetwork NSURLSession delegate invalidation.
• Firebase 12.16.0 includes a Firebase Performance change for NSProxy NSURLSession delegates:
  https://firebase.google.com/support/release-notes/ios#version_12160_-_july_8_2026
• The related Firebase Performance source path is:
  FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.m
  This code is involved in discovering objects behind NSProxy delegates for NSURLSession instrumentation.
• The related Firebase Performance change appears to be:
  b1df9f0
• PAGWeakProxy is an NSProxy NSURLSession delegate wrapper with a weak forwarding target. The crash occurs when CFNetwork calls respondsToSelector: and PAGWeakProxy reads that weak target.

Request:
Could the Firebase Performance Monitoring team please prioritize this issue and provide:

• Firebase-side root-cause confirmation.
• A fix as soon as possible.

Reproducing the issue

Observed in production after affected apps upgraded to Firebase Apple SDK 12.16.0.
The crash occurs during NSURLSession delegate invalidation when CFNetwork calls respondsToSelector: on an NSProxy-based delegate wrapper.

Firebase SDK Version

12.16.0

Xcode Version

N/A. This is a production runtime crash.

Installation Method

N/A

Firebase Product(s)

Performance

Targeted Platforms

iOS

Relevant Log Output

If using Swift Package Manager, the project's Package.resolved

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If using CocoaPods, the project's Podfile.lock

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