Part of:

• Guidelines: Evolve CPT to enable support for skills, memory, and plans via taxonomy #77230

Summary

Restores standard WP_REST_Posts_Controller behavior on /wp/v2/guidelines so any wp_guideline post can be created, listed, updated, and deleted with the usual fields (title, content, excerpt, author, taxonomy terms). The site-wide singleton — the post tagged with the content term in wp_guideline_type — moves to a new /wp/v2/content-guidelines route backed by Gutenberg_Content_Guidelines_REST_Controller. That controller preserves the existing custom guideline_categories schema, the ?status / ?category / ?block filters, the singleton-create guard, and the revision/restore semantics (now under Gutenberg_Content_Guidelines_Revisions_Controller mounted at /wp/v2/content-guidelines/{id}/revisions).

The singleton routes are scoped to actual content-typed posts: /content-guidelines/{id} and its revisions sub-routes return 404 when the requested post lacks the content term, so artifact-typed guidelines stay reachable only via the standard collection. The wp-admin Guidelines UI client and the e2e helper are updated to point at /wp/v2/content-guidelines.

Singleton writes (POST/PATCH/DELETE on /content-guidelines, plus revision DELETE and restore) require manage_options; reads use the post type's standard edit_posts cap so editors can view but not modify the singleton. The standard /wp/v2/guidelines collection inherits the post type's full capability map (now extended with publish_posts, read_private_posts, edit_private_posts, and delete_private_posts) so editors can create and manage artifact-typed guidelines through the default REST flow.

Things to consider

The wp_guideline post type advertises only the supports needed to make the editing flow functional today — title, editor, excerpt, author, and revisions. The post type is internal (public: false, publicly_queryable: false), so there is no front-of-site to worry about, and the schema isn't a hard floor. Now that the standard /wp/v2/guidelines endpoint is fully functional, it's worth deciding whether to widen it to be more page-like, since pages and posts share the same generic WP_REST_Posts_Controller and the only thing that distinguishes them at the REST layer is the post type's supports flags. The two changes most worth considering are adding thumbnail (so artifacts can carry a featured image, which helps in admin lists and pickers) and adding page-attributes together with flipping hierarchical to true so guidelines can nest — Brand → Voice → Tone — alongside the flat wp_guideline_type tag. Skipping custom-fields and comments seems right: the former only adds the legacy admin UI (register_post_meta() already exposes meta via the REST meta field), and the latter is out of band for guideline authoring. None of this changes the singleton route's hand-rolled schema; it only widens the standard /guidelines endpoint.

A second thing to consider is that singleton enforcement is now advisory rather than authoritative. Because /wp/v2/guidelines is open, an admin can POST a second content-typed guideline directly to the standard collection and the new controller's "rest_guidelines_exists" guard won't catch it. If hard enforcement matters later, it would need to move into a pre_post_* / save_post_wp_guideline hook at the data layer. The acceptance here is that the singleton constraint is a UI affordance, not a data invariant.

Test plan

• vendor/bin/phpcs lib/experimental/guidelines phpunit/experimental/guidelines
• npm run test:unit:php:base -- --filter Guidelines — covers singleton CRUD, singleton-create guard, the query-param filters, the artifact-rejection guard on /content-guidelines/{id} and revisions, revision creation, restore, admin-only write enforcement, the revision deletion lock, the singleton schema, capability mapping, and artifact CRUD via /wp/v2/guidelines
• npm run lint:js -- routes/guidelines/api.ts test/e2e/specs/admin/guidelines.spec.js
• Manually verify GET /wp/v2/content-guidelines returns the singleton and POST to it errors when one already exists
• Manually verify GET /wp/v2/guidelines lists artifact posts and POST /wp/v2/guidelines creates an artifact (auto-tagged with the artifact term via the existing save_post_wp_guideline hook)
• Manually verify PATCH /wp/v2/content-guidelines/{ARTIFACT_ID} returns 404 (rest_post_invalid_id)
• wp-admin Guidelines page (Settings → Guidelines) loads, edits, saves, and shows revision history

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