WordPress versions from 4.7 onward receive selected security fixes after leaving active support, while Gutenberg code remains relevant to WordPress releases from 5.0 onward. Each release’s Gutenberg snapshot is maintained on a wp/X.Y branch, but its testing infrastructure has deteriorated: workflows fail or do not run because of issues such as branch filters and event targeting. Restoring reliable checks is necessary to validate Gutenberg security patches before they reach WordPress core.

Operation Tall Stack proposes repairs across more than 20 release branches through stacks of 18 to 32 focused pull requests per branch. The changes address broken CI, remove jobs unnecessary for release branches, pin actions and runner images, and align test environments with each release’s supported PHP and Node.js versions. They also repair wp-env, Composer and PHPUnit tooling, and stabilize flaky tests.

The stacked structure separates each fix for review while allowing CI on the top pull request to test the combined changes. Matching fixes use consistent names and positions across branches, making cross-branch review easier; branch-specific changes are included only where needed. Most changes follow or adapt trunk fixes, and package releases are excluded except for the development-only wp-env. With roughly 500 pull requests, review is intended to be organized by fix rather than by branch. Draft changes remain AI-produced and unverified until human review.