fix(mdxish): inline Anchor/Glossary with expression attrs render as plain text

[eaglethrost]

🎫 Resolve CX-3591

🎯 What does this PR do?

There was a reported bug where <Anchor> tags were breaking not rendering as links. The root cause of the reported Anchor was it contained complex expression in an attribute: href={'https://' + user.docsUrl + '/reference/sign-up-api'}, which the raw anchor HTML can't render.

The fix is to now let the mdx tokenizer to now claim inline PascalCase components in text mode (Anchor & Glossary) and pass it on the relatively newly created MDX inline HTML transformer path (processor/transform/mdxish/components/inline-html.ts), which parses them into mdxJsxTextElement so they render correctly.

🧪 QA tips

• Inline Anchor with a concatenation-expression href renders as a link (the original repro):

  <Anchor target="_blank" href={'https://' + 'www.google.com' + '/reference/sign-up-api'}>Content</Anchor>.

• Inline Glossary with a template-literal expression attr renders:

  <Glossary term={`a${b}c`}>word</Glossary>

• Plain inline Anchor (no expression attrs) still renders via the existing CommonMark path:

  <Anchor href="https://example.com">Link</Anchor>

📸 Screenshot or Loom

Old mdxish editor vs fixed mdxish vs legacy editor (correct baseline):

Screen.Recording.2026-06-25.at.4.28.51.pm.mov

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 2aab521 and b650fca.

📒 Files selected for processing (4)

• __tests__/lib/mdxish/mdxish.test.ts
• __tests__/transformers/mdx-inline-html.test.ts
• lib/micromark/mdx-component/syntax.ts
• processor/transform/mdxish/components/inline-html.ts

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• readmeio/ai (manual)
• readmeio/gitto (manual)
• readmeio/markdown (manual)
• readmeio/readme (manual)

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Walkthrough

The MDX tokenizer (lib/micromark/mdx-component/syntax.ts) is updated to allow a specific allowlist of PascalCase components (INLINE_COMPONENT_TAGS, containing Anchor and Glossary) to be tokenized in text/inline mode. Previously, all PascalCase tags were immediately rejected in text mode. Now, tagNameFirst defers rejection, tagNameRest computes a claimable predicate using INLINE_COMPONENT_TAGS for text mode and TOKENIZER_MDX_COMPONENT_EXCLUDED_TAGS for flow mode, and afterOpenTagName extends the brace-attribute requirement (requiresBraceAttr) to text-mode PascalCase components. The inline-HTML transformer (processor/transform/mdxish/components/inline-html.ts) correspondingly replaces GENERIC_MDX_COMPONENT_EXCLUDED_TAGS with INLINE_COMPONENT_TAGS and updates promoteInlineHtml to promote only allowlisted PascalCase tags. Tests are added at both the transformer and integration levels.

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[eaglethrost]

Merging because it was previously approved and it was just a merge conflict dismissing it.

[rafegoldberg]

This PR was released!

🚀 Changes included in v14.10.3