Fonts: Keep font names through CSS validation, storage, and output

[matiasbenedetto]

Core changes some font names when it treats CSS values as plain text. For example, O'Reilly Sans produces an invalid unquoted @font-face descriptor. This PR preserves the decoded name through font validation, storage, resolution, and CSS output.

Trac ticket: https://core.trac.wordpress.org/ticket/63568

-@font-face{font-family:O'Reilly Sans; ... }
+@font-face{font-family:"O'Reilly Sans"; ... }

The fix also preserves commas inside quoted names, significant spaces, CSS escapes, and punctuation. It keeps a named family such as "serif" distinct from the generic keyword serif.

Implementation. WP_Font_Utils gets a private CSS font-family parser and serializer. The class adds only two public methods, and both return plain values:

• is_valid_css_font_family() returns true if the value is valid CSS. It requires the complete value to be a list of names and generic families, or one CSS-wide keyword.
• get_font_face_family() returns the first family of the value as a quoted CSS string for an @font-face descriptor. It returns an empty string if the value names no font.

The private parser has two modes:

• The strict mode requires valid CSS and consumes the complete value. It returns typed entries for named families, generic families, and reserved keywords.
• The plain name mode reads each entry of the list as CSS. If an entry is not valid CSS, it reads the raw text up to the next comma as one plain name, as earlier WordPress versions did. This accepts O'Reilly Sans, O"Reilly Sans, Bodoni*, and Font (Display). A plain name can hold any text except control characters, and the serializer makes it inert. The parser ignores an empty entry, such as the entry after a trailing comma.

The private serializer keeps explicit quotes around each named family. An unquoted name stays unquoted if it uses one identifier of letters and hyphens. Each other name gets quotes. The serializer escapes quotes, backslashes, control characters, <, >, &, ;, and ,. It keeps the family order and the difference between names and generic keywords.

The array of parsed entries is not public, so it is not an API contract.

The parser uses no recursion. It accepts only kai, fangsong, khmer-mul, and nastaliq as generic() arguments. It validates the decoded argument before it emits CSS, so an escaped argument cannot introduce a second declaration.

These parts of core use the shared parser:

• WP_Font_Utils::sanitize_font_family() and WP_Font_Utils::get_font_face_slug().
• WP_Font_Face and WP_Font_Face_Resolver.
• The fontFamily schema of WP_Font_Collection.
• Both font REST controllers. A value with control characters returns a 400 error. The font faces controller also rejects the empty quoted name "". The controllers accept the name 0, which the empty check read as a false value.
• safecss_filter_attr().

An invalid face value produces a _doing_it_wrong() notice and no face output.

KSES. safecss_filter_attr() still splits declarations at each semicolon. If the CSS font family grammar accepts a font-family value, the function skips the character checks that reject punctuation, such as a parenthesis or a backslash escape. Other values still use the current checks, and the safecss_filter_attr_allow_css filter remains in the path. The serializer writes a semicolon in a name as \3b , so the split at each semicolon keeps the name.

An earlier revision of this PR used a quote-aware declaration splitter. I removed it, because it read a quote inside an unquoted url() as the start of a string. A declaration after it, such as behavior: url(x.htc), then got past the allowlist.

Compatibility.

Input	sanitize_font_family() output
Manrope	Manrope
"Manrope"	"Manrope"
"-webkit-body"	"-webkit-body"
-webkit-body	-webkit-body
-apple-system, BlinkMacSystemFont, sans-serif	-apple-system, BlinkMacSystemFont, sans-serif
Open Sans, sans-serif	"Open Sans", sans-serif
O'Reilly Sans	"O'Reilly Sans"
"ACME, Sans", sans-serif	"ACME\2c Sans", sans-serif
"serif", serif	"serif", serif
Bodoni*	"Bodoni*"
"A"; color:red	"\"A\"\3b color:red" (one inert name)
A + U+0001 + B	empty string

• The serializer keeps explicit quotes around a named family. Thus "-webkit-body" selects a named font instead of a browser keyword. An unquoted name stays unquoted if it uses one identifier of letters and hyphens. Each other name gets quotes. The same rule preserves the difference between "-apple-system" and -apple-system.
• The @font-face descriptor always uses quotes. Thus font-family:Manrope in the face output becomes font-family:"Manrope". The preset value stays Manrope.
• The preset can contain "ACME\2c Sans", sans-serif, while its face descriptor contains only "ACME\2c Sans". The decoded name stays ACME, Sans.
• The serializer escapes a comma, because some clients split a font family list at each comma and do not read quoted strings. For example, the Gutenberg Font Library preview function formatFontFamily() read "ACME, Sans" as the two names ACME and Sans, so the preview used a fallback font. The Gutenberg client function createCssString() already escapes a comma in the same way.
• The serializer escapes <, >, and & so names survive HTML output and KSES post filters. Backslashes use hexadecimal escapes because wp_kses_no_null() can remove a literal backslash before zeros. Short hexadecimal escapes retain their terminator spaces.
• get_font_face_slug() compares decoded names, so equivalent CSS escapes identify the same face. It keeps the WordPress 6.5 rule that removes quotation marks and apostrophes from a name. For example, O'Reilly Sans gives oreilly sans;normal;400;100%;U+0-10FFFF. A record from an earlier version can still have a different slug.
• In the slug, the characters %, \, ;, ,, &, <, and > in a name become percent sequences. They cannot change the slug fields or the post_title. Ordinary names such as Open Sans retain their previous slug. If the parser rejects a value, the slug uses the WordPress 6.5 text normalization.
• The duplicate check compares saved settings with the current slug rules, including when a title matches. Thus a title collision between the old and new slug formats does not reject a different font name. If the title check finds no matching settings, the controller reads face records in batches of 100. This adds database reads and catches duplicates across families and after the first batch.
• This PR performs no bulk data migration.

Client dependency and limits. The upload client in core sends the raw name from the font file as fontFamily, for example Bodoni*. Core reads each entry as CSS first. If the entry is not valid CSS, core stores the raw text as one name. Thus most raw names work with the current client.

Some raw names are also valid CSS with a different meaning, and the server cannot tell them apart. CSS reads a comma as a list, /* */ as a comment, a backslash as an escape, serif or inherit as a keyword, and joins spaces between identifiers. These names need an upload client that sends a quoted CSS string, such as Gutenberg PR #76782. Core accepts valid CSS without the special escape scheme of that PR.

Display-name storage remains outside this fix. The family controller still applies sanitize_text_field() to the display name in post_title. A display name with markup can therefore lose that text, independently of the CSS identity.

Font name test guide

This list is the reference for all tests of font names in this PR. Each case has a number. The same number is in the file name of its test font. The PHPUnit test Tests_Fonts_FontFamilyDataPath::test_raw_name_gives_the_documented_result sends each raw name of the list through the REST API and checks the expected result, with the case number as the name of the data set. Cases 84 and 85 hold invalid UTF-8, which a JSON request cannot carry.

Test fonts. Download trac-63568-edge-case-fonts.zip. It holds one font for each case (case-NN-….woff2) and a control font (case-00-control.woff2, name Edge Control Sans). Each font is a copy of DM Sans Regular (SIL OFL 1.1) with a different family name in its name table. All the fonts have the same glyphs. Case 84 has no font, because a font name table cannot hold invalid UTF-8.

Steps for one case.

1. Activate Twenty Twenty-Five.
2. Delete all custom fonts in Appearance > Fonts. Many cases share a slug, for example O'Reilly Sans and O"Reilly Sans.
3. Upload the font of the case in Appearance > Fonts > Upload. The upload activates the font.
4. Open the home page.
5. Run document.fonts.load('16px "<name>"') in the console, with the name as a CSS string. The result must hold one loaded face.
6. Compare a text in the font with the same text in the control font. The widths must be the same.
7. Check the stored fontFamily in GET /wp/v2/font-families. It must decode to one name with the exact text of the case, so that the preset uses the font.

Expected results.

• Works: the upload succeeds, the face loads with the exact name, and the preset names the font.
• Works (trimmed name): the same, but core and both upload clients remove a space at the start or the end of the name. The display name, the preset, and the face all use the trimmed name, so the preset selects the face. A PHPUnit test checks this.
• Rejected: the REST API returns 400, or the editor sends no request.
• Limit (…): the result is wrong with the upload client in core, for a reason that the server cannot fix:
  • comma, comment, escape, keyword, spaces: CSS reads the raw name in a different way. An upload client that sends a quoted CSS string, such as Gutenberg PR #76782, fixes these cases.
  • Cases 54 and 55 in browsers: Chromium 149, Chrome 153, and Firefox 151 do not use emoji and fangsong as generic keywords yet. So the text renders in the uploaded font, but the stored value is still a generic keyword, and the case fails step 7. A browser that uses these keywords shows a fallback font.
  • slug: the editor makes the slug with kebabCase(), which removes all non-Latin letters. The empty slug gives a 400 error. This needs a client fix.

Earlier browser results. I ran each case with Playwright in Chromium, through the Fonts page, as in the steps above. The core upload client is the Gutenberg build that trunk pins (5715a61), built locally. The last column used the Gutenberg plugin from PR #76782 (86cf7bad0d) with this PR at 4d54df7d10, which is before the commit that accepts raw names and the name 0. I ran all the cases again with this PR at 88508e2613 and the same Gutenberg plugin. Each case passed or failed as the last column shows. Case 44 (0) works at that revision because of that commit.

The table records results from earlier revisions. I did not repeat the complete upload test at 1a7bae7460. A comparison of all 85 raw-name cases found no change in sanitizer output between be5d8ec126 and 1a7bae7460. The selected PHPUnit groups also pass at 1a7bae7460. These checks support the documented PHP behavior; they do not verify the complete upload flow at the current revision.

Case	Name	Group	Expected	trunk	This PR	This PR + #76782
1	O'Reilly Sans	quotes	Works	✘ no face	✔	✔
2	O"Reilly Sans	quotes	Works	✘ no face	✔	✔
3	O'Reilly "Sans"	quotes	Works	✘ no face	✔	✔
4	Suisse BP Int'l	quotes	Works	✘ no face	✔	✔
5	‘Curly’ “Quotes”	quotes	Works	✔	✔	✔
6	'Leading apostrophe	quotes	Works	✘ face Leading apostrop…	✔	✔
7	Trailing quote"	quotes	Works	✘ face Trailing quote	✔	✔
8	ACME, Sans	punctuation	Limit (comma)	✘ face ACME	✘ face ACME	✔
9	A;B	punctuation	Works	✘ face A	✔	✔
10	A{B}	punctuation	Works	✘ no face	✔	✔
11	A=B	punctuation	Works	✘ no face	✔	✔
12	What?	punctuation	Works	✘ no face	✔	✔
13	A:B	punctuation	Works	✘ no face	✔	✔
14	Font (Display)	punctuation	Works	✔	✔	✔
15	Font [Beta]	punctuation	Works	✔	✔	✔
16	Font !important	punctuation	Works	✔	✔	✔
17	Dr. Font	punctuation	Works	✔	✔	✔
18	Font #1	punctuation	Works	✔	✔	✔
19	Font @Home	punctuation	Works	✔	✔	✔
20	Font/Slash	punctuation	Works	✘ no face	✔	✔
21	A/*c*/B	punctuation	Limit (comment)	✘ face A B	✘ face A B	✔
22	Bodoni*	punctuation	Works	✘ no face	✔	✔
23	Jost*	punctuation	Works	✘ no face	✔	✔
24	Rounded M+ 1c	punctuation	Works	✔	✔	✔
25	C++ Mono	punctuation	Works	✔	✔	✔
26	50% Gray	punctuation	Works	✔	✔	✔
27	Font 50%AB	punctuation	Works	✘ face Font 50	✔	✔
28	Font%2c Sans	punctuation	Works	✘ face Font Sans	✔	✔
29	Font, Sans	punctuation	Limit (comma)	✘ face Font	✘ face Font	✔
30	A\B	punctuation	Limit (escape)	✘ face A[U+000B]	✘ face A[U+000B]	✔
31	Trailing\	punctuation	Works	✘ no face	✔	✔
32	\0030	punctuation	Limit (escape)	✘ face 0	✘ face 0	✔
33	Tom & Jerry	html	Works	✔	✔	✔
34	Tom & Jerry	html	Works	✔	✔	✔
35	A<B>	html	Works	✘ face A	✔	✔
36	Test </style> Sans	html	Works	✘ face Test Sans	✔	✔
37	</style><script>alert(1)</script>	html	Works	✘ no face	✔	✔
38	<!-- x -->	html	Works	✘ no face	✔	✔
39	url(javascript:alert(1))	html	Works	✘ no face	✔	✔
40	expression(alert(1))	html	Works	✘ no face	✔	✔
41	A"; color: red; x:"	html	Works	✘ no face	✔	✔
42	A} body { color: red	html	Works	✔	✔	✔
43	12345	numbers	Works	✘ no face	✔	✔
44	0	numbers	Works	✘ 400 (empty name)	✔	✔
45	-1 Font	numbers	Works	✔	✔	✔
46	1942 report	numbers	Works	✔	✔	✔
47	Press Start 2P	numbers	Works	✔	✔	✔
48	--custom	numbers	Works	✔	✔	✔
49	-apple-system	numbers	Works	✔	✔	✔
50	serif	keywords	Limit (keyword)	✘ preset is generic serif	✘ preset is generic serif	✔
51	Serif	keywords	Limit (keyword)	✘ preset is generic serif	✘ preset is generic serif	✔
52	sans-serif	keywords	Limit (keyword)	✘ preset is generic sans-serif	✘ preset is generic sans-serif	✔
53	system-ui	keywords	Limit (keyword)	✘ preset is generic system-ui	✘ preset is generic system-ui	✔
54	emoji	keywords	Limit (keyword)	✘ preset is generic emoji	✘ preset is generic emoji	✔
55	fangsong	keywords	Limit (keyword)	✘ preset is generic fangsong	✘ preset is generic fangsong	✔
56	inherit	keywords	Limit (keyword)	✘ preset is keyword inherit	✘ preset is keyword inherit	✔
57	INHERIT	keywords	Limit (keyword)	✘ preset is keyword inherit	✘ preset is keyword inherit	✔
58	initial	keywords	Limit (keyword)	✘ preset is keyword initial	✘ preset is keyword initial	✔
59	unset	keywords	Limit (keyword)	✘ preset is keyword unset	✘ preset is keyword unset	✔
60	revert-layer	keywords	Limit (keyword)	✘ preset is keyword revert-layer	✘ preset is keyword revert-layer	✔
61	default	keywords	Limit (keyword)	✘ preset is keyword default	✘ preset is keyword default	✔
62	generic(kai)	keywords	Limit (keyword)	✘ preset is generic generic(kai)	✘ preset is generic generic(kai)	✔
63	A B	whitespace	Limit (spaces)	✘ face A B	✘ face A B	✔
64	Leading space	whitespace	Works (trimmed name)	✔ ¹	✔ ¹	✔ ¹
65	Trailing space	whitespace	Works (trimmed name)	✔ ¹	✔ ¹	✔ ¹
66	A[U+0009]B	whitespace	Limit (spaces)	✘ face A B	✘ face A B	✔
67	A[U+000A]B	whitespace	Limit (spaces)	✘ face A B	✘ face A B	✔
68	A[U+00A0]B	whitespace	Works	✔	✔	✔
69	A[U+3000]B	whitespace	Works	✔	✔	✔
70	A[U+200B]B	whitespace	Works	✔	✔	✔
71	日本語 😀	unicode	Limit (slug)	✘ 400 (empty slug)	✘ 400 (empty slug)	✘ 400 (empty slug)
72	微软雅黑	unicode	Limit (slug)	✘ 400 (empty slug)	✘ 400 (empty slug)	✘ 400 (empty slug)
73	ＭＳ ゴシック	unicode	Limit (slug)	✘ 400 (empty slug)	✘ 400 (empty slug)	✘ 400 (empty slug)
74	Ñandú	unicode	Works	✔	✔	✔
75	Café	unicode	Works	✔	✔	✔
76	Café	unicode	Works	✔	✔	✔
77	وزیرمتن	unicode	Limit (slug)	✘ 400 (empty slug)	✘ 400 (empty slug)	✘ 400 (empty slug)
78	A[U+202E]B	unicode	Works	✔	✔	✔
79	Dev 👩[U+200D]💻	unicode	Works	✔	✔	✔
80	AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA…	boundary	Works	✔	✔	✔
81	A\A\A\A\A\A\A\A\A\A\A\A\A\A\A\A\A\…	boundary	Works	✘ no face	✔	✔
82	A[U+0000]B	boundary	Works	✘ face AB	✔	✔
83	A[U+0001]B	boundary	Rejected (400)	✘ no face	✘ 400 (invalid value)	✔
84	A\xFFB	boundary	Rejected: no font file can hold invalid UTF-8.	—	—	—
85	A[U+D800]B	boundary	Rejected (400)	✘ 400 (invalid JSON)	✘ 400 (invalid JSON)	✘ 400 (invalid JSON)
86	(empty)	boundary	Rejected (no name)	✘ 400 (empty name)	✘ 400 (empty name)	✘ not sent
87		boundary	Rejected (no name)	✘ 400 (empty slug)	✘ 400 (empty slug)	✘ not sent

Control and invisible characters appear as [U+XXXX]. "No face" means that the browser has no face with the name, because the @font-face rule is invalid or missing. In the earlier browser tests, all 57 cases that must work passed with this PR. The 4 cases that must be rejected returned 400. The tested trunk revision passed 29 of the 57.

¹ The face loaded with the trimmed name, and the preset used the same name. The test measured the text width only with the untrimmed name, so these two cases have no width result. In the last column, case 83 works because that client escapes the control character.

CSS input values (53 cases)

These values come from a theme, a collection, or a REST client that sends CSS. Strict is the strict mode of the private parser, which KSES uses through is_valid_css_font_family(). Input is the plain name mode, which the REST API, theme input, and font faces use. Each entry shows its type and its decoded value.

Group	CSS	Strict	Input
matrix	Inter	name Inter	name Inter
matrix	Open Sans	name Open Sans	name Open Sans
matrix	"O'Reilly Sans"	name O'Reilly Sans	name O'Reilly Sans
matrix	O'Reilly Sans	Rejected	name O'Reilly Sans
matrix	'O"Reilly Sans'	name O"Reilly Sans	name O"Reilly Sans
matrix	"O'Reilly \"Sans\""	name O'Reilly "Sans"	name O'Reilly "Sans"
matrix	"ACME, Sans", sans-serif	name ACME, Sans; generic sans-serif	name ACME, Sans; generic sans-serif
matrix	ACME\,Sans, serif	name ACME,Sans; generic serif	name ACME,Sans; generic serif
matrix	"Tom & Jerry"	name Tom & Jerry	name Tom & Jerry
matrix	"Tom \26 Jerry"	name Tom & Jerry	name Tom & Jerry
matrix	"Tom \000026 Jerry"	name Tom &Jerry	name Tom &Jerry
matrix	"Tom \000026 Jerry"	name Tom & Jerry	name Tom & Jerry
matrix	"Font 50%AB"	name Font 50%AB	name Font 50%AB
matrix	"A B"	name A B	name A B
matrix	A B	name A B	name A B
matrix	"12345"	name 12345	name 12345
matrix	"-1 Font"	name -1 Font	name -1 Font
matrix	"What?"	name What?	name What?
matrix	"A;B"	name A;B	name A;B
matrix	"A{B}"	name A{B}	name A{B}
matrix	"A=B"	name A=B	name A=B
matrix	"A\\B"	name A\B	name A\B
matrix	"O\22 Reilly Sans"	name O"Reilly Sans	name O"Reilly Sans
matrix	"serif", serif	name serif; generic serif	name serif; generic serif
matrix	"inherit", sans-serif	name inherit; generic sans-serif	name inherit; generic sans-serif
matrix	Inter, generic(kai)	name Inter; generic generic(kai)	name Inter; generic generic(kai)
matrix	"日本語 😀"	name 日本語 😀	name 日本語 😀
matrix	"A<B>"	name A<B>	name A<B>
matrix	Inter/* comment */, serif	name Inter; generic serif	name Inter; generic serif
boundary	"Inter"	name Inter	name Inter
boundary	""	name	name
boundary	"0"	name 0	name 0
boundary	"A\[U+000A]B"	name AB	name AB
boundary	"\41 B"	name AB	name AB
boundary	"\41B"	name Л	name Л
boundary	"\0"	name [U+FFFD]	name [U+FFFD]
boundary	"\110000"	name [U+FFFD]	name [U+FFFD]
boundary	"\D800"	name [U+FFFD]	name [U+FFFD]
boundary	"A\"	Rejected	name "A\"
boundary	Inter,	Rejected	name Inter
boundary	-apple-system, BlinkMacSystemFont, sans-serif	name -apple-system; name BlinkMacSystemFont; generic sans-serif	name -apple-system; name BlinkMacSystemFont; generic sans-serif
negative	"Inter	Rejected	name "Inter
negative	Inter /* open	Rejected	name Inter /* open
negative	"Inter" Bold	Rejected	name "Inter" Bold
negative	"A"; color:red	Rejected	name "A"; color:red
negative	"A"} body{color:red	Rejected	name "A"} body{color:red
negative	url(javascript:alert(1))	Rejected	name url(javascript:alert(1))
negative	expression(alert(1))	Rejected	name expression(alert(1))
negative	generic(\6b ai\29 ;color:red)	Rejected	name generic(\6b ai\29 ;color:red)
negative	generic(foo)	Rejected	name generic(foo)
negative	inherit, serif	Rejected	name inherit; generic serif
negative	Inter, , serif	Rejected	name Inter; generic serif
negative	"</style><script>alert(1)</script>"	name </style><script>alert(1)</script>	name </style><script>alert(1)</script>

Current automated results. These local results cover commit 1a7bae7460 on PHP 8.3.31. The PHPUnit groups use a separate table prefix in the test database. A temporary test container maps example.com to a public address because the local DNS resolver did not resolve it. This permits the URL checks in tests that mock HTTP requests.

Command or check	Result
phpunit --group fonts,kses,restapi-global-styles	Passed: 1,333 tests, 4,285 assertions.
phpunit -c tests/phpunit/multisite.xml --group fonts,kses,restapi-global-styles	Passed: 1,334 tests, 4,288 assertions.
PHPCS on the 5 files in commit 1a7bae7460	Passed: no errors or warnings.
PHP compatibility checks (PHPCompatibilityWP, PHP 7.4 and later) on the 2 source files in that commit	Passed.
Chromium test with a custom face named -webkit-body	Passed: the quoted preset loads the custom face. The unquoted preset loads no custom face.
Comparison of the 85 raw-name cases	No change in sanitizer output between be5d8ec126 and 1a7bae7460.

The regression tests cover old face records, equivalent CSS escapes, duplicates across families, and records after the first batch of 100. They also permit different weights and distinct names whose old and new titles collide. The quote tests preserve named browser keywords and keep unquoted browser keywords.

GitHub checks at 1a7bae7460. Code style, PHP compatibility, and PHP static analysis passed. The PHPUnit workflow reports failures in 18 PHP 8.5 jobs. The PHP 8.5 / MySQL 8.4 job reports 231 errors from deprecated ReflectionMethod::setAccessible() calls in the font tests. I did not inspect the other failure logs. Thus the local results do not establish a pass for the complete GitHub matrix.

Earlier automated results. The following results cover be5d8ec126, except composer phpstan, which covers 526821468d. These are historical results. I did not rerun the full PHPUnit suites locally at 1a7bae7460.

Command or check	Result at the earlier revision
composer phpstan	16 errors, none in a file that this PR changes.
PHPCS on the 19 PHP files that this PR changes	Passed: no errors or warnings.
PHP compatibility checks (phpcompat.xml.dist) on the changed source files	Passed.
phpunit (full suite)	Passed: 26,182 tests, 4,562,389 assertions; no failures or errors; 86 PHPUnit deprecation warnings and 44 skipped tests.
phpunit -c tests/phpunit/multisite.xml (full suite)	Passed: 27,026 tests, 4,564,560 assertions; no failures or errors; 86 PHPUnit deprecation warnings and 46 skipped tests.

Browser evidence and limits. The guide above records earlier browser results for 86 font files through the upload flow of the Fonts page. Those results do not cover 1a7bae7460. I ran the earlier complete test in Chromium 149, Chrome 153, and Firefox 151. In all three browsers, each case gave the result in the table. In Firefox, case 67 (A[U+000A]B) gives no REST request with the upload client in core, and the editor shows no notice. Chromium and Chrome send the request, and the font gets a wrong name. Both results fail, as the table shows. I did not test WebKit, including the -apple-system behavior in Safari. The test checks that the stored value decodes to the exact name, that a face loads, and that its metrics match the control font. It does not compare the rendered glyphs in a screenshot.

A comment on this PR has videos of the complete test in the three browsers. An earlier comment has videos of the upload flow at 6913a32d02.

Use of AI Tools

AI assistance: Yes

Tool(s): Claude Code and Codex

Model(s): Claude Opus 5, Claude Opus 5.5, and Claude Fable 5.1; GPT-6.

Used for: The implementation, code review, code reduction, regression tests, test execution, and PR description.

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[matiasbenedetto]

Testing evidence: 86 edge-case fonts in Chromium, Chrome, and Firefox

These videos test all the fonts from trac-63568-edge-case-fonts.zip with the steps of the font name test guide in the description. For each case, the video does these steps:

1. A script deletes all fonts.
2. The video uploads the case font in Appearance → Fonts → Upload.
3. A script sets the font as the body text font in Global Styles.
4. The video opens the home page and runs four checks:
   • The stored fontFamily decodes to one font name with the exact text of the case (step 7).
   • document.fonts.load() finds a loaded face with that name (step 5).
   • Text in that name has the same width as text in the control font (step 6).
   • The body text on the page has the same width as the control font.

Case 1 plays at normal speed. Cases 2–87 play at 5× speed, with a scoreboard. Each video ends with a summary table that compares each case with the guide.

Setup: wordpress-develop Docker environment, Twenty Twenty-Five, Playwright 1.61.1. The core upload client is the Gutenberg build that trunk pins (5715a61).

Setup	Chromium 149	Chrome 153	Firefox 151
trunk at 57c4558589	29 of 57	29 of 57	29 of 57
This PR at 88508e2613	57 of 57	57 of 57	57 of 57
This PR + #76782 at 86cf7bad0dc	57 of 57	57 of 57	57 of 57

The table shows how many of the 57 cases that must work pass. In all nine runs, each of the 86 cases gives the result that the guide shows.

trunk at 57c4558589

Chromium 149

edge-1-trunk-chromium.mp4

Chrome 153 and Firefox 151

Chrome 153

edge-1-trunk-chrome.mp4

Firefox 151

edge-1-trunk-firefox.mp4

This PR at 88508e2613

Chromium 149

edge-2-core-pr-chromium.mp4

Chrome 153 and Firefox 151

Chrome 153

edge-2-core-pr-chrome.mp4

Firefox 151

edge-2-core-pr-firefox.mp4

This PR + Gutenberg PR #76782 at 86cf7bad0dc

Chromium 149

edge-3-core-and-gutenberg-prs-chromium.mp4

Chrome 153 and Firefox 151

Chrome 153

edge-3-core-and-gutenberg-prs-chrome.mp4

Firefox 151

edge-3-core-and-gutenberg-prs-firefox.mp4

Notes

• Case 67 (A[U+000A]B) in Firefox: with the core upload client, the editor sends no REST request and shows no notice. Chromium and Chrome upload the font, but with a wrong name. Both results fail, as the guide shows. With #76782, the case works in all three browsers.
• Cases 54 and 55: all three browsers render the text in the uploaded font, because they do not use emoji and fangsong as generic keywords yet. With the core upload client, these cases fail step 7.
• The script writes the body font directly to the global styles post, as an admin save does. It does not use the Styles UI.
• I did not test WebKit or Safari.