I got a call last week from a client running a high-traffic WooCommerce store—we’re talking 15k SKUs and a very custom block-based checkout. They’d seen the announcement for the WordPress 6.9 Release Candidate 3 and, being “proactive,” decided to hit the update button on their live production server. Total nightmare. Within ten minutes, their checkout was throwing 500 errors because of a minor data-attribute change in a block they’d customized. They thought a point release was just a minor tweak. It wasn’t.
Reaching the RC3 phase is a huge milestone for the community, but as I told that client, an RC is still software under development. It’s for testing, not for running your bread and butter. If you’re seeing the buzz around the WordPress 6.9 Testing phase, you need to treat it with the respect a senior dev gives to any unvetted core change. You don’t just “wing it” with your database.
My first instinct when I saw their broken checkout was to just write a quick filter in the theme’s functions.php to bypass the validation error. I figured I could just bridge the gap until the official release. And that worked… for about five minutes. Then I realized my “quick fix” was preventing tax calculations from firing correctly. I fell into the classic trap of trying to patch a core bug on a live site instead of doing the right thing: rolling back to a stable version and moving the testing to a staging environment.
Handling WordPress 6.9 Testing the Right Way
If you want to actually help the community and protect your clients, you have to test this the right way. According to the official notes on the WordPress News site, there are four main ways to get RC3 running. I personally prefer WP-CLI because it’s fast and keeps me out of the dashboard when things are breaking. You can just run wp core update --version=6.9-RC3 on your local dev environment and see what happens to your custom hooks.
The Field Guide for 6.9 is where the real meat is. If you’re a developer, you need to be looking at the Gutenberg commits and the Trac tickets mentioned in the 6.9 Field Guide. This is where you’ll see the subtle changes to the block editor or the REST API that might nuke your custom integrations. Trust me on this, reading those notes now will save you a twelve-hour Sunday shift later.
/**
* A simple utility to prevent beta/RC updates on production
* and log environment-specific data for testing.
*/
function bbioon_protect_production_environment() {
if ( defined( 'WP_ENVIRONMENT_TYPE' ) && 'production' === WP_ENVIRONMENT_TYPE ) {
// Just a safety check to ensure we aren't running dev logic here
return;
}
// Logic for staging/local testing with WordPress 6.9 RC3
error_log( 'bbioon: Running compatibility check on ' . get_bloginfo( 'version' ) );
}
add_action( 'admin_init', 'bbioon_protect_production_environment' );For theme and plugin authors, this is the final stretch. If you haven’t tested your “Tested up to” headers, now is the time. But do it in a sandbox. Use the WordPress Playground instance if you don’t want to spin up a whole local site. It’s literally a browser-based instance that lets you break things without any consequences. No setup, no cleanup, just straight-to-the-point testing.
Lessons from the Trenches
The takeaway here isn’t just “don’t update production.” It’s about understanding the release cycle. RC3 is the last call for major bug reports before the scheduled release on December 2, 2025. Here is how you should actually approach it:
- Never trust an RC on a mission-critical site. Period.
- Use WP-CLI or the Beta Tester plugin only on staging or local.
- Check your “Tested up to” versions now so you aren’t scrambling on release day.
- If you find a bug, report it to the Alpha/Beta area of the support forums. Don’t just sit on it.
Look, this stuff gets complicated fast, especially when you have custom APIs or complex WooCommerce workflows involved. If you’re tired of debugging someone else’s mess and just want your site to work through the next major core update, drop my team a line. We’ve probably seen it before.
Are you planning to test 6.9 on a local build this week, or are you waiting for the final release to see what breaks?
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