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Editor: PHP backports for Client Side Media#10868

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adamsilverstein wants to merge 49 commits intoWordPress:trunkfrom
adamsilverstein:backport-preload-changes-for-csm-70
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Editor: PHP backports for Client Side Media#10868
adamsilverstein wants to merge 49 commits intoWordPress:trunkfrom
adamsilverstein:backport-preload-changes-for-csm-70

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@adamsilverstein adamsilverstein commented Feb 4, 2026 •
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This PR contains the PHP backports for the client-side media processing feature, enabling the editor to perform client-side image resizing, thumbnail generation, and format conversion using WebAssembly.

Preloaded Settings

The following site settings are now preloaded in both the post editor and site editor:

  • image_sizes - Available image size configurations
  • image_size_threshold - Big image size threshold (default 2560px)
  • image_output_formats - Output format mappings for image conversion
  • jpeg_interlaced - Whether to use progressive/interlaced JPEG encoding
  • png_interlaced - Whether to use interlaced PNG encoding
  • gif_interlaced - Whether to use interlaced GIF encoding

REST API: Index Endpoint

Added media processing settings to the REST API index (/wp-json/wp/v2/):

  • image_sizes - All registered image sizes with dimensions and crop settings
  • image_size_threshold - Big image size threshold
  • image_output_formats - Format conversion mappings

REST API: Attachments Endpoint

New Fields

  • filename - Original attachment file name
  • filesize - File size in bytes
  • exif_orientation - EXIF orientation value (1-8) for client-side rotation handling

New Parameters

  • generate_sub_sizes - When false, disables server-side sub-size generation and EXIF rotation
  • convert_format - When false, disables automatic image format conversion

New Sideload Endpoint

Added /wp/v2/media/{id}/sideload endpoint for uploading sub-sized images to an existing attachment. Used by client-side media processing to upload generated image sizes without creating new attachments. Supports both images and PDFs.

PDF Improvements

Improved missing_image_sizes field handling for PDFs, which use the fallback_intermediate_image_sizes filter instead of wp_get_missing_image_subsizes().

Cross-Origin Isolation

Added COOP (Cross-Origin-Opener-Policy) and COEP (Cross-Origin-Embedder-Policy) headers in the block editor to enable SharedArrayBuffer for WebAssembly-based processing. Includes:

  • Output buffer to automatically add crossorigin="anonymous" attributes to external resources
  • Media templates updated with crossorigin attributes for audio, img, and video tags

WASM Support

Added AddType directive for WebAssembly files to .htaccess rules, enabling serving .wasm files for client-side media processing libraries like wasm-vips.

Tests

Updated REST API tests for the new attachment fields and sideload endpoint.

Gutenberg PRs:

Gutenberg tracking issue: WordPress/gutenberg#75062

Trac ticket: https://core.trac.wordpress.org/ticket/62243

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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@adamsilverstein adamsilverstein mentioned this pull request Feb 4, 2026
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@adamsilverstein adamsilverstein changed the title Editor: Add REST API preloaded paths for client-side media processing Editor: PHP back posrts for client-side media Feb 5, 2026
@adamsilverstein adamsilverstein changed the title Editor: PHP back posrts for client-side media Editor: PHP backports for client-side media Feb 5, 2026
@adamsilverstein adamsilverstein changed the title Editor: PHP backports for client-side media Editor: PHP backports for Client Side Media Feb 5, 2026
@adamsilverstein adamsilverstein self-assigned this Feb 5, 2026
westonruter
westonruter reviewed Feb 8, 2026
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Sorry for what may be an unsolicited early review, as the PR is still a draft.

westonruter
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adamsilverstein commented Feb 12, 2026

Sorry for what may be an unsolicited early review, as the PR is still a draft.

No worries, happy to have your feedback. Indeed I started working on this pr before the Gutenberg work had merged to get ahead and be more prepared - so it may change a bit, but probably not much at this point.

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@adamsilverstein adamsilverstein mentioned this pull request Feb 16, 2026
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@adamsilverstein adamsilverstein marked this pull request as ready for review February 19, 2026 07:33
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Core Committers: Use this line as a base for the props when committing in SVN:

Props adamsilverstein, westonruter, mamaduka, mukesh27, swissspidy, andrewserong.

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Mamaduka reviewed Feb 19, 2026
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src/wp-includes/rest-api/class-wp-rest-server.php Outdated
Comment on lines +1371 to +1372
// Add media processing settings for users who can upload files.
if ( current_user_can( 'upload_files' ) ) {
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Not a blocker (can be changed post-beta), but maybe the attachments controller is a better place for these settings.

We had a similar discussion for template-related settings during WP 6.8 - https://core.trac.wordpress.org/ticket/62574#comment:29

cc @peterwilsoncc

westonruter
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@andrewserong andrewserong mentioned this pull request Feb 20, 2026
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andrewserong commented Feb 20, 2026

Just a quick comment: it looks like this accidentally removes the ca-bundle.crt file, so I assume needs a rebase?

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adamsilverstein commented Feb 20, 2026

Just a quick comment: it looks like this accidentally removes the ca-bundle.crt file, so I assume needs a rebase?

oh, i thought i had added that file. will fix. Also figured out why this isn't working, fix incoming.

@adamsilverstein
add preload patchs for client side media
7cab03d
@adamsilverstein
REST API: Add media processing settings to index endpoint
bf24f67
@adamsilverstein
REST API: Add filename and filesize fields to attachments
f20f2f9 
Add filename and filesize REST fields to the attachments endpoint
for client-side media processing. The filename returns the original
attachment file name, and filesize returns the file size in bytes.
swissspidy
swissspidy reviewed Feb 20, 2026
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adamsilverstein and others added 6 commits February 20, 2026 16:11
@adamsilverstein
Refactor cross-origin check to be data-driven
7ac186e 
Rename $tags to $cross_origin_tag_attributes and restructure
it as a mapping of tag name to attributes with boolean values
indicating whether each is a srcset. This replaces the
hardcoded IMG srcset special case with a generic loop,
making it easier to extend (e.g. for imagesrcset on LINK).
@adamsilverstein
Add imagesrcset and poster to cross-origin checks
c6c68dd 
LINK elements can have imagesrcset for preloading responsive
images, and VIDEO elements can have a poster image URL. Both
need cross-origin handling.
@adamsilverstein
Remove wp_filter_mod_rewrite_rules_for_wasm
894a9ff 
WASM files are now inlined as base64 data URLs at build
time, so the .htaccess AddType rule is no longer needed.
@adamsilverstein @claude
Add crossorigin check and docs to wp_override_media_templates
6b6d9e2 
Skip setting crossorigin when already present, and document why
the simpler approach (vs wp_add_crossorigin_attributes) is needed
for Underscore.js template placeholders.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@adamsilverstein @claude
Remove unused params from filter_wp_unique_filename
dd58977 
The $ext, $unique_filename_callback, and $alt_filenames parameters
were not used in the method body. The closure still receives all 6
filter args positionally but now only passes the 4 that are needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@adamsilverstein
Merge branch 'trunk' into backport-preload-changes-for-csm-70
9203e5d
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adamsilverstein commented Feb 20, 2026

@westonruter I believe I have addressed all outstanding feedback (except the output mapping one I will work on in a follow up). Can you give it another spin?

@adamsilverstein
Move crossorigin processing into wp_print_media_templates
1d4e8cd 
Instead of using a separate wp_override_media_templates function
that removes and re-adds the admin_footer action with an anonymous
closure, add the crossorigin attribute processing directly within
wp_print_media_templates itself. This simplifies the approach and
eliminates the indirection of action hook manipulation.
@adamsilverstein
Fix PHPCS array declaration spacing errors
5a62665
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mukeshpanchal27 commented Feb 20, 2026

@adamsilverstein have you checked why unit tests are failed?

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adamsilverstein commented Feb 20, 2026

@adamsilverstein have you checked why unit tests are failed?

looking now...

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adamsilverstein commented Feb 20, 2026

@adamsilverstein have you checked why unit tests are failed?

looks like I just needed to update the wp-api fixtures which i did in 57c4f00 (by running the test_build_wp_api_client_fixtures test locally)

@adamsilverstein @claude
Fix wp-api-generated.js fixture to match CI environment
d56772b 
The previous fixture regeneration included spurious meta fields
(footnotes, _wp_note_status) and changed authentication format,
causing both QUnit and PHPUnit CI failures. Reset to trunk's fixture
and re-apply only the legitimate CSM changes (sideload endpoint,
generate_sub_sizes, convert_format, image_sizes, filename, filesize).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 61703
GitHub commit: 0544d56

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.

@github-actions github-actions bot closed this Feb 20, 2026
adamsilverstein added a commit to WordPress/gutenberg that referenced this pull request Feb 20, 2026
@adamsilverstein @claude
REST API: Make filter_wp_unique_filename() static to match core
2577a22 
After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This was referenced Feb 20, 2026
Merged
Open
adamsilverstein added a commit to WordPress/gutenberg that referenced this pull request Feb 20, 2026
@adamsilverstein @claude
REST API: Make filter_wp_unique_filename() static to match core, plus…
03a4bf9 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
peterwilsoncc pushed a commit to peterwilsoncc/gutenberg-build that referenced this pull request Feb 22, 2026
@adamsilverstein
REST API: Make filter_wp_unique_filename() static to match core, plus…
a2881af 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Source: WordPress/gutenberg@03a4bf9
scruffian pushed a commit to WordPress/gutenberg that referenced this pull request Feb 23, 2026
@adamsilverstein @claude @scruffian
REST API: Make filter_wp_unique_filename() static to match core, plus…
9df4bac 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
ockham pushed a commit to WordPress/gutenberg that referenced this pull request Feb 24, 2026
@adamsilverstein @claude @ockham
REST API: Make filter_wp_unique_filename() static to match core, plus…
f6e37c0 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
peterwilsoncc pushed a commit to peterwilsoncc/gutenberg-build that referenced this pull request Feb 24, 2026
@adamsilverstein
REST API: Make filter_wp_unique_filename() static to match core, plus…
ba239cd 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Source: WordPress/gutenberg@f6e37c0
gutenbergplugin pushed a commit to WordPress/gutenberg that referenced this pull request Feb 25, 2026
@adamsilverstein @claude @gutenbergplugin
REST API: Make filter_wp_unique_filename() static to match core, plus…
21b607c 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
peterwilsoncc pushed a commit to peterwilsoncc/gutenberg-build that referenced this pull request Feb 25, 2026
@adamsilverstein
REST API: Make filter_wp_unique_filename() static to match core, plus…
3ca528b 
… avoid duplicate routes (#75782)

* REST API: Make `filter_wp_unique_filename()` static to match core

After WordPress/wordpress-develop#10868 (r61703), the core
`WP_REST_Attachments_Controller::filter_wp_unique_filename()` method
was changed to `private static`. This causes a fatal error in the
Gutenberg subclass which declares it as non-static.

Aligns the Gutenberg method signature with core by making it static
and simplifying the parameters to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Avoid duplicate sideload route registration when core already has it

Since core trunk now registers the sideload route in
`WP_REST_Attachments_Controller::register_routes()`, only register
it in the Gutenberg subclass when the parent class doesn't already
have the `sideload_item` method. Updates the test accordingly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Source: WordPress/gutenberg@21b607c
@adamsilverstein adamsilverstein mentioned this pull request Mar 5, 2026
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