Prototype : Implement slug generation feature with UI and tests - #897

What?

Closes #876

This PR introduces the Slug Generation experimental feature (ai/slug-generation ability & experiment). It provides AI-assisted permalink suggestions directly inside the WordPress Block Editor based on post title, content, and additional context.

Open Questions

Pre-publish panel, sidebar-next-to-slug, or both? See above, this affects where the ability gets wired into the editor UI. [I think starting with just the sidebar-next-to-slug would suffice]

Both entry points (sidebar popover + pre-publish panel) are currently supported in prototype.

Should slug suggestions consider existing permalinks on the site to avoid near-duplicate slugs, or is that out of scope for v1?

WordPress core natively enforces slug uniqueness on post save, not sure if we should cover this in Slug generation

Does this warrant a WP-CLI command for bulk slug review/regeneration on existing content, similar to the alt-text bulk command?

Not covered in prototype, but we can cover if required.

Why?

Creating concise, keyword-rich, and SEO-friendly permalink slugs often requires extra effort from content creators. This feature streamlines the publishing workflow by automatically suggesting URL-safe slugs within the permalink inspector popover and the pre-publish panel.

How?

• Abilities API Integration:

  • Implemented WordPress\AI\Abilities\Slug_Generation\Slug_Generation extending Abstract_Ability.
  • Added system instructions (system-instruction.php) enforcing URL-safe, lowercase, hyphenated slug generation.
  • Sanitizes and validates outputs using sanitize_title().

• Experiment Framework:

  • Added WordPress\AI\Experiments\Slug_Generation\Slug_Generation under Experiment_Category::EDITOR.
  • Localized configuration settings (minimum content length requirement, number of suggestions).

• Block Editor UI Components:

  • Permalink Inspector Button: Injects a "Generate Slug" button into the Block Editor permalink popover (.editor-post-url).
  • Interactive Modal (SlugGenerationModal): Renders a modal interface allowing users to preview, manually edit, select, or regenerate slug options.
  • Pre-Publish Panel (SlugPrePublishPanel): Adds a PluginPrePublishPanel sidebar card to review or change the post slug prior to publishing.

• Automated Tests:

  • Added PHP integration test coverage (Slug_GenerationTest.php) for ability execution, argument validation, and permissions.
  • Updated E2E helper routines (helpers.ts) for reliable REST API save synchronization during bulk toggle tests.

Use of AI Tools

AI assistance: Yes
Tool(s): Antigravity AI
Model(s): Gemini 3.6 Flash
Used for: Initial implementation of ability and experiment classes, React UI components, unit/integration tests, and code documentation. Final changes reviewed and verified by human developer.

Testing Instructions

1. Ensure global AI features and an AI Connector with text generation capabilities are active.
2. Navigate to Settings > AI and enable the Slug Generation experiment under Editor Experiments.
3. Create a new post in the Block Editor and add a post title and content (at least 250 characters).
4. Click on the Permalink / URL field in the document sidebar to open the permalink popover.
5. Click Generate Slug. Verify the modal pops up with 3 generated slug suggestions.
6. Select a suggested slug (or edit it in the input field) and click Insert. Verify the post permalink updates.
7. Click Publish to open the pre-publish panel. Verify the Suggested Slugs pre-publish panel appears and allows applying suggestions.

Screenshots or screencast

Changelog Entry

Feature : Slug generation feature to suggest SEO-friendly permalinks in the Block Editor.