Render LaTeX equations with KaTeX in Content

[3mdistal]

Summary

• render canonical inline and block LaTeX with KaTeX in editable documents and read-only/public readers
• render equations in standalone HTML and PDF-ready exports while preserving canonical source in Markdown
• keep malformed equations visible and repairable, with KaTeX trust disabled and accessible MathML output
• document the syntax for agents and add a Content changelog entry
• cover rendering, security, editing, copy/paste, export, and NFM round-trips

Why

Content already parses inline $...$ and block $$ delimiters into structured NFM atoms, but those atoms were displayed as plain labels. This completes the presentation and export layers without changing the canonical source format or adding a second math grammar.

Validation

• 225 focused Vitest tests passed across math rendering, exports, NFM, editor interactions, and the public route
• production Content build passed and bundles KaTeX for client and server rendering
• frozen lockfile install and diff checks passed
• independent real-Chrome QA passed inline, display, malformed-source fallback, terminal-caret editing with refresh persistence, accessibility exposure, and narrow-viewport math overflow
• repository-wide typecheck still reports 152 pre-existing errors; none reference changed files

Notes

The local-file page actions menu does not expose HTML/PDF export, so export output is covered by focused integration tests rather than manual download QA.

[github-actions]

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[builder-io-integration]

Builder reviewed your changes and found 3 potential issues 🟡

Review Details

Incremental Code Review Summary

The latest commit fixes both previously open findings: escaped delimiter parity is now handled, and indented display equations are retained inside list items. I resolved those two stale review threads before this review. The broader approach remains sound: KaTeX is shared across editor and export paths, SSR markup is emitted during render, and malformed expressions remain visible rather than being discarded.

New Findings

• 🟡 MEDIUM — Same-type nested bullet lists are still flattened because the collector treats any indented matching marker as a sibling.
• 🟡 MEDIUM — Inline code spans ending in a backslash no longer close correctly because code-fence detection applies Markdown escape parity inside code content.
• 🟡 MEDIUM — A malformed inline math opener can skip a backslash-adjacent closing delimiter and then consume a later code span, corrupting the remainder of the paragraph.

The change remains standard risk, centered on shared export parsing and user-facing document structure. The dev server is healthy. Full browser verification was attempted, but executor sessions still lacked browser navigation/DOM/screenshot tools; static/unit checks covered the main rendering paths but could not validate these live export edge cases.

🧪 Browser testing: Could not verify — browser automation tools were unavailable in the executor environment; all planned cases were environment-blocked.