LaTeX

Render math while it streams with remark-math and rehype-katex, hold incomplete formulas with latexGuard, and clean model output with preprocessLaTeX.

Until its closing $$ arrives, a streaming formula is either raw TeX or a KaTeX error. Streamdown renders math through the plugins you add, holds incomplete formulas with latexGuard, and normalizes the delimiters models actually emit with preprocessLaTeX.

Setup

Math rendering comes from your plugins. Add remark-math and rehype-katex, load KaTeX's CSS, and enable latexGuard.

TSX

import { preprocessLaTeX, Streamdown } from "@lobehub/streamdown";
import rehypeKatex from "rehype-katex";
import remarkMath from "remark-math";
import "katex/dist/katex.min.css";

<Streamdown
  content={content}
  latexGuard
  preprocess={preprocessLaTeX}
  rehypePlugins={[rehypeKatex]}
  remarkPlugins={[remarkMath]}
/>;

Toggle the guard and the preprocessor

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latexGuard

With latexGuard, Streamdown holds the previous frame while the trailing formula is still incomplete, so a half-streamed $$… block never flashes raw source or a KaTeX parse error. It uses isLastFormulaRenderable(text), which finds the trailing formula still waiting for its closing delimiter (skipping code spans and fences) and checks whether KaTeX can already render it.

preprocessLaTeX

Models emit math in shapes remark-math does not parse. Pass preprocessLaTeX as preprocess to normalize the text before rendering. By default it:

escapes currency dollars such as $20 or $1,000
converts \[…\] to $$…$$ and $…$ to $…$
escapes mhchem commands, pipes inside formulas (so tables do not split), and underscores inside \text{}

Code blocks are protected throughout. Optional steps are enabled through the second argument:

Option	Default	Effect
`escapeCurrency`	`true`	Escape currency dollar signs
`convertBrackets`	`true`	Convert bracket delimiters to dollar delimiters
`escapeMhchem`	`true`	Escape mhchem commands
`escapePipes`	`true`	Escape `\|` inside formulas
`escapeUnderscores`	`true`	Escape underscores in `\text{}`
`fixErrors`	`false`	Balance unmatched braces and `\left` / `\right`
`normalizeSpacing`	`false`	Normalize whitespace in formulas
`handleCJK`	`false`	Handle CJK characters next to formulas
`addCJKSpaces`	`false`	Add spaces between CJK text and formulas (with `handleCJK`)
`validate`	`false`	Validate every formula
`throwOnValidationError`	`false`	Throw when validation fails (with `validate`)

preprocessLaTeXMinimal and preprocessLaTeXStrict are exported as well, together with the individual steps: escapeCurrencyDollars, convertLatexDelimiters, escapeMhchemCommands, escapeLatexPipes, escapeTextUnderscores, fixCommonLaTeXErrors, normalizeLatexSpacing, handleCJKWithLatex and validateLatexExpressions.