Disable admin view transitions in Chromium

[akirk]

What?

This PR aims to solve #3845 by disabling browser-native View Transitions for wp-admin pages when Playground is running in a Chromium-based browser.

Why?

Chrome/Edge/Opera can crash when navigating to wp-admin pages such as Appearance -> Themes while admin View Transitions are enabled. Firefox does not appear to hit the same crash, so this keeps the opt-out scoped to Chromium-based browsers by default.

How?

• Detect Chromium-based browsers inside the remote boot path while generating Playground runtime options.
• Define PLAYGROUND_DISABLE_ADMIN_VIEW_TRANSITIONS in a runtime MU plugin when the remote context is Chromium based.
• In the Playground MU plugin, skip Playground fallback View Transitions and dequeue/deregister Core's wp-view-transitions-admin style for wp-admin requests.
• Allow repros with ?with-admin-transitions, which forwards through remote.html to the worker and keeps admin View Transitions enabled.

Testing

• php -l packages/playground/remote/src/lib/playground-mu-plugin/0-playground.php
• npx nx test playground-client --testFile=blueprints-v1-handler.spec.ts
• npx nx typecheck playground-client
• npx nx typecheck playground-remote
• npx nx lint playground-remote
• git diff --check trunk
• Manual headed Chrome 149 check: loaded Playground wp-admin, clicked Appearance -> Themes, confirmed themes.php loaded without a page crash and no View Transition styles were present.
• Manual headed Chrome 149 repro override check: loaded ?with-admin-transitions&storage=temp&url=/wp-admin/, confirmed wp-view-transitions-admin-inline-css was present, clicked Appearance -> Themes, and reproduced the page crash.

Debugging Details

Props @adamziel for this dump analysis (Google Chrome 149.0.7827.201 (Official Build) (arm64) Revision 6a7b3dbec3b2ca25877c2553b5473b2f277ef644-refs/branch-heads/7827_196@{#6}):

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Disables browser-native View Transitions on wp-admin pages when Playground runs in Chromium-based browsers to avoid crashes during admin navigation.

Changes:

• Adds a runtime MU-plugin generated by the worker to define a flag for disabling admin View Transitions in Chromium-based browsers.
• Updates the Playground MU-plugin to (a) skip Playground fallback View Transitions and (b) dequeue/deregister Core’s wp-view-transitions-admin stylesheet for admin requests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
packages/playground/remote/src/lib/playground-worker-endpoint.ts	Generates a runtime MU-plugin and adds Chromium-based browser detection to define PLAYGROUND_DISABLE_ADMIN_VIEW_TRANSITIONS.
packages/playground/remote/src/lib/playground-mu-plugin/0-playground.php	Uses the runtime flag to opt out of Playground View Transitions in wp-admin and removes Core’s admin view transitions style.

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[akirk]

I am trying a CI crash repro using a non-headless approach and during that i'll disable the other CI jobs, thus marking this as draft during those commits are in.

[akirk]

Ok ready for review again, I preserved the files during the repro and reported my findings at the Chromium bug report: https://issues.chromium.org/issues/530704642#comment2

[adamziel]

Looks good. I proposed adjusting some names and comments since the word should in names such as playground_should_disable_view_transitions doesn't communicate what's the intention.