Newsletter: roll out the modernized dashboard to 100%

[dhasilva]

Fixes #

Completes the staged rollout that #49036 set up (and that closed #48530). #49036 introduced the cohort gate held at 0% on the Jetpack side while the Simple-site rollout ran from the WordPress.com backend. With that cohort validated, this PR takes the Jetpack/Atomic side to 100% and removes the now-unneeded scaffolding.

Proposed changes

• The modernized Newsletter wp-admin dashboard, wp-admin subscriber management, and the retired Calypso "Subscribers" submenu now default on for every site (Simple, WoA/Atomic, and self-hosted Jetpack).
• Both feature filters now default to a plain true instead of the cohort result:
  • rsm_jetpack_ui_modernization_newsletter — the canonical gate for the wp-build dashboard (applied in Newsletter\Settings::is_modernized(), the wpcom/v2/subscribers/* REST route registration, the subscriptions module menu, and the jetpack-mu-wpcom admin menu).
  • jetpack_wp_admin_subscriber_management_enabled — applied in the Newsletter script data, the subscriptions module menu, and the Jetpack Redux state.
• Removed the staged-rollout scaffolding now that it always evaluates to true:
  • Newsletter\Settings::MODERNIZATION_ROLLOUT_PERCENTAGE and is_modernization_rollout_enabled() (the Automattician carve-out + the wpcom-blog-ID % 100 bucket math).
  • The inline mirror of that math in jetpack-mu-wpcom's wpcom-admin-menu.php.
  • The method_exists-guarded cross-package delegations at the three Jetpack-plugin call sites (they now pass a literal true, so there's no sibling-package call left to guard).
  • The is_automattician() test stub in the newsletter package bootstrap and the cohort/a12s unit tests; the remaining tests assert the new true default and the host opt-out.
• Opt-out is unchanged: hosts (and a11ns who want the legacy view back) can still force the legacy experience with add_filter( 'rsm_jetpack_ui_modernization_newsletter', '__return_false' ) / add_filter( 'jetpack_wp_admin_subscriber_management_enabled', '__return_false' ).
• The Backup, VideoPress, and Scan MODERNIZATION_FILTER constants are separate flags and are intentionally untouched.

Related product discussion/links

• Predecessor: Newsletter: stage the modernized dashboard rollout across all sites (held at 0%) #49036 (staged the rollout at 0%); tracking issue Newsletter: modernize into a unified wp-admin product (six-PR sequence) #48530.

Does this pull request change what data or activity we track or use?

No.

Testing instructions

• On any connected site (Simple, WoA/Atomic, or self-hosted Jetpack), as a non-Automattician, go to Jetpack → Newsletter in wp-admin and confirm the modernized wp-build dashboard loads (Subscribers / Settings tabs) instead of the legacy Settings-only screen — the experience is now on for everyone, not just the a12s carve-out / percentage cohort.
• Confirm the standalone Calypso Jetpack → Subscribers submenu is gone (replaced by the transitional announcement page where the Newsletter package registers it).
• Confirm GET /wpcom/v2/subscribers/list is registered (returns a data / 401 response, not rest_no_route).
• Confirm the host opt-out still wins: add_filter( 'rsm_jetpack_ui_modernization_newsletter', '__return_false' ); restores the legacy Settings screen and the legacy Calypso Subscribers submenu; add_filter( 'jetpack_wp_admin_subscriber_management_enabled', '__return_false' ); restores the legacy subscriber-management default.
• PHP unit tests: composer phpunit in projects/packages/newsletter (42 tests) and --filter WPCOM_Admin_Menu_Test in projects/packages/jetpack-mu-wpcom both pass.

🤖 Generated with Claude Code

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack or WordPress.com Site Helper), and enable the release/newsletter-dashboard branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack release/newsletter-dashboard

bin/jetpack-downloader test jetpack-mu-wpcom-plugin release/newsletter-dashboard

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

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---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Make sure to test your changes on all platforms that it applies to. You're responsible for the quality of the code you ship.
3. You can use GitHub's Reviewers functionality to request a review.
4. When it's reviewed and merged, you will be pinged in Slack to deploy the changes to WordPress.com simple once the build is done.

If you have questions about anything, reach out in #jetpack-developers for guidance!

---

Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly:
  • Scheduled release: July 7, 2026
  • Code freeze: July 6, 2026

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[jp-launch-control]

Code Coverage Summary

Coverage changed in 5 files.

File	Coverage	Δ%	Δ Uncovered
projects/packages/newsletter/src/class-settings.php	75/188 (39.89%)	-5.56%	5 💔
projects/plugins/jetpack/_inc/lib/admin-pages/class-jetpack-redux-state-helper.php	165/276 (59.78%)	-0.15%	0 💚
projects/plugins/jetpack/_inc/lib/core-api/wpcom-endpoints/class-wpcom-rest-api-v2-endpoint-subscribers-list.php	369/543 (67.96%)	-0.12%	0 💚
projects/plugins/jetpack/modules/subscriptions.php	63/419 (15.04%)	-0.40%	0 💚
projects/packages/jetpack-mu-wpcom/src/features/wpcom-admin-menu/wpcom-admin-menu.php	189/423 (44.68%)	-1.17%	-1 💚

Full summary · PHP report · JS report

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