This task is a blocker for WE6.4.2 ([FY25-26 Q1](https://meta.wikimedia.org/wiki/Wikimedia_Foundation_Annual_Plan/2025-2026/Product_%26_Technology_OKRs#Q1)), as tracked by the parent task {T360995}.
>>! Step 2 of the **[PHP upgrade process § Test checklist](https://wikitech.wikimedia.org/wiki/PHP_upgrade_process_for_MediaWiki#Test)**:
> * QTE, MW, SRE: Validation and end-to-end testing, especially areas not covered by CI.
This testing step is the last phase before SRE may start the rollout and send (a percentage of) live web requests in production to the PHP 8.3 containers.
This task represents the testing for **MediaWiki Platform Team** components as listed on [mw:Maintainers](https://www.mediawiki.org/wiki/Developers/Maintainers). It is up to the team to judge and decide what components warrant testing at this stage, and what/how much testing to do.
> MediaWiki core:
> * [x] Authentication and Authorization
> * [x] BagOStuff
> * [x] Benchmarker
> * [ ] Notifications
> * [x] Profiler
> * [x] ResourceLoader
> * [x] StatsLib
>
> MediaWiki extensions:
> * [x] CentralAuth
> * [x] OATHAuth
> * [x] OAuth
> * [ ] OAuthRateLimiter
> * [x] WebAuthn
>
> MediaWiki libs:
> * [x] wikimedia/cssjanus
> * ~~OOjs~~ (not PHP)
> * ~~jquery-client~~ (not PHP)
> * [x] wikimedia/less.php
> * [x] wikimedia/minify
> * [ ] wikimedia/php-session-serializer
> * [x] wikimedia/relpath
> * [x] wikimedia/wrappedstring
>
> Misc service-level components:
> * [x] php-excimer
> * ~~poolcounter~~ (not PHP)
How to test:
* Enable [WikimediaDebug](https://wikitech.wikimedia.org/wiki/WikimediaDebug) in your browser and choose the k8s-mwdebug-**next** option. This routes wikipedia.org and wikimedia.org requests from your browser to the new MediaWiki containers that run PHP 8.3 instead of PHP 8.1.
* Report any problems under {T401855}, via the button on that task.
* Even if you see no problems in the user interface, check the [Logstash: mwdebug](https://logstash.wikimedia.org/app/dashboards#/view/mwdebug1002) for any errors during your debug session. For example, non-fatal errors (such as PHP Deprecation, PHP Notice, and PHP Warning messages), and post-send exceptions (such as via a DeferredUpdate) would not show in the user interface, but are reported to Logstash.
* We will by default **delay** the rollout until subtasks of T401855 are resolved. If an issue you found is considered non-blocking, please leave a comment on the subtask in question.
Once your team is satisfied with testing and has discovered any issues you want to discover before rollout, feel free to close this task.