Style states: fix state deselection when selecting the already selected block

[talldan]

What?

Fixes #81254, the selected style state was being lost whenever clicking into the already selected block.

How?

The bug was due to an incorrect case in the reducer for the selected style state. The SELECTION_CHANGE action usually dispatches a start.clientId and end.clientId, not just a clientId. The reducer was not handling this.

The code is now updated to preserve the selected state for single block selections if the selected block doesn't change.

Testing Instructions

1. Add a button block
2. Open the inspector and select the 'Hover' state
3. Click the button in the canvas

In trunk: The 'Hover' state becomes deselected
In this PR: The 'Hover' state remains

Screenshots or screencast

Kapture.2026-08-06.at.11.37.10.mp4

Use of AI Tools

OpenCode / Codex

[github-actions]

Size Change: +17 B (0%)

Total Size: 7.81 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	434 kB	+17 B (0%)

_{compressed-size-action}

[github-actions]

Flaky tests detected in a8ee280.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/31094135715
📝 Reported tests:

As a user I want to be able to create a navigation overlay for a specific navigation block in /test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js, passed after 1 failed attempt.

TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for getByRole('region', { name: /(Editor publish|Save panel)/ }).getByRole('button', { name: 'Save', exact: true })

    at Editor.saveSiteEditorEntities (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/editor/site-editor.ts:45:5)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/site-editor/navigation-overlay-template-part.spec.js:93:4

two users concurrently move list items (RTC WebSocket) in /test/e2e/specs/editor/collaboration/collaboration-stress.spec.ts, passed after 1 failed attempt.

TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for locator('role=toolbar[name="Block tools"i]').locator('role=button[name="Move up"i]')
    - locator resolved to <button id=":rq:" type="button" tabindex="-1" aria-label="Move up" data-toolbar-item="true" aria-describedby="block-editor-block-mover-button__description-0" class="components-button block-editor-block-mover-button is-up-button is-next-40px-default-size has-icon">…</button>
  - attempting click action
    - waiting for element to be visible, enabled and stable
    - element is visible, enabled and stable
    - scrolling into view if needed
    - done scrolling
  - element was detached from the DOM, retrying

    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/collaboration/collaboration-stress.spec.ts:634:7
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/collaboration/collaboration-stress.spec.ts:613:3

[ramonjd]

Nice, neat fix. Tests well! When I click on the block with the hover state selected the state UI still shows in the inspector.

Everyone gets a video!!

Before

Kapture.2026-08-07.at.09.33.27.mp4

After

Kapture.2026-08-07.at.09.33.42.mp4

[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: talldan <talldanwp@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: i-am-chitti <iamchitti@git.wordpress.org>
Co-authored-by: jordesign <jordesign@git.wordpress.org>

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

[github-actions]

I just cherry-picked this PR to the wp/7.1 branch to get it included in the next release: e597aa3