Experiment: Add Suggest Reply experiment

[Infinite-Null]

Closes: #508

Suggest Reply Experiment

Description

This PR implements the Suggest Reply experiment, which adds an AI-powered "Suggest reply" action to both the Comments admin screen and the Activity dashboard widget.

This feature allows moderators to generate contextual reply suggestions based on the comment's content, the parent post's context, and optional editorial guidelines.

Key Features

• WP Ability Integration: Registers the ai/reply-suggestion WP Ability which handles the context building and communication with the AI client.
• Interactive Modal UI:
  • Allows selecting a reply tone (Friendly, Professional, or Casual).
  • Includes a textarea for optional free-text editorial guidelines (e.g. "always mention our support email").
  • Generates and displays the AI suggestion.
• Quick Actions:
  • Use this reply: Automatically opens the WordPress inline comment reply form, populates it with the generated suggestion, and focuses the textarea.
  • Copy: Includes a transient "Copied!" button to easily grab the text for manual usage.

Testing Instructions

1. Ensure you have an AI provider connected and enabled in Settings → AI and also Suggest Reply experiment is enabled under Admin Experiments in /wp-admin/options-general.php?page=ai-wp-admin .
2. Go to the Comments screen in the WordPress admin.
3. Hover over a comment and click Suggest reply.
4. Test changing the tone and adding custom guidelines, then click Generate.
5. Click Use this reply to verify the inline reply form opens and populates correctly.
6. Click Copy to verify clipboard functionality.
7. Go to the Dashboard and repeat the tests from the Activity (Recent Comments) widget.

Screenshot/Screencast

Usage

WhatsApp.Video.2026-06-16.at.7.30.39.PM.mp4

Screen.Recording.2026-06-16.at.7.16.22.PM.mov

Error Examples

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Infinite-Null <ankitkumarshah@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[Infinite-Null]

Hi @jeffpaul and @dkotter,

I've completed the implementation for this experiment and updated the flow based on the feedback shared in the issue discussion.

The PR is ready for review. Thank you!

[codecov]

Codecov Report

❌ Patch coverage is 4.54545% with 147 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.01%. Comparing base (77f116e) to head (02e6d3a).
⚠️ Report is 60 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ludes/Abilities/Suggest_Reply/Reply_Suggestion.php	0.00%	106 Missing ⚠️
...cludes/Experiments/Suggest_Reply/Suggest_Reply.php	15.90%	37 Missing ⚠️
...des/Abilities/Suggest_Reply/system-instruction.php	0.00%	4 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #724      +/-   ##
=============================================
+ Coverage      74.45%   75.01%   +0.56%     
- Complexity      1740     1858     +118     
=============================================
  Files             85       90       +5     
  Lines           7521     7918     +397     
=============================================
+ Hits            5600     5940     +340     
- Misses          1921     1978      +57     

Flag	Coverage Δ
unit	75.01% <4.54%> (+0.56%)	⬆️

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[Infinite-Null]

I’m marking this PR as draft temporarily to complete the test coverage. The implementation itself is complete; I just need to add the tests and will mark it ready for review again once they’re done.