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remend is a pre-processor for streaming Markdown text. As an LLM streams tokens, it produces a string that may end mid-way through a formatting construct — an unclosed **, a partial link [text](, or a dangling $ — which would cause the downstream Markdown parser to misinterpret the entire document. remend scans the text and applies a prioritised chain of fixup handlers before the string reaches the parser. Streamdown applies remend automatically in mode="streaming" when parseIncompleteMarkdown={true} (the default). The remend prop on <Streamdown> forwards RemendOptions directly.

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Installation

npm install remend

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Usage

import remend from "remend";

const fixed = remend(incompleteMarkdown, options);

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Standalone example

import remend from "remend";

// Closes the open bold marker
remend("Hello **world");          // → "Hello **world**"

// Removes an incomplete link (placeholder URL)
remend("Click [here](htt");       // → "Click [here](streamdown:incomplete-link)"

// Escapes a single tilde between word chars to prevent false strikethrough
remend("pH~7 is neutral");        // → "pH\~7 is neutral"

// Strips a trailing incomplete HTML tag
remend("Visit <a hre");           // → "Visit"

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Default export: remend()

function remend(text: string, options?: RemendOptions): string
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text
string
required
The raw streaming Markdown text to process.
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options
RemendOptions
Optional configuration. When omitted, all built-in handlers except inlineKatex are enabled with their default behaviour.
Returns the processed string. If text is empty or not a string, it is returned unchanged.

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RemendOptions

All options default to true (enabled) unless stated otherwise. Set an option to false to disable that specific handler.
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bold
boolean
Complete incomplete bold markers. **text → **text**. Default: true.
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boldItalic
boolean
Complete incomplete bold-italic markers. ***text → ***text***. Default: true.
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italic
boolean
Complete incomplete italic markers for *, _, and __ variants. Default: true.
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inlineCode
boolean
Complete an unclosed inline code span. `code → `code`. Default: true.
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strikethrough
boolean
Complete incomplete strikethrough markers. ~~text → ~~text~~. Default: true.
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links
boolean
Fix incomplete link syntax. [text](url → [text](streamdown:incomplete-link). Default: true.
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images
boolean
Fix incomplete image syntax. Enables the links handler when set to true. Default: true.
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linkMode
string
Controls how incomplete links are handled. "protocol" (default) replaces the partial URL with streamdown:incomplete-link. "text-only" removes the link markup entirely, leaving only the display text.
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katex
boolean
Complete an incomplete block KaTeX expression. $$equation → $$equation$$. Default: true.
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inlineKatex
boolean
Complete an incomplete inline KaTeX expression. $equation → $equation$. Default: false — a single $ is ambiguous with currency and this handler is opt-in.
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singleTilde
boolean
Escape a single ~ between word characters to prevent false strikethrough. 20~25 → 20\~25. Default: true.
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setextHeadings
boolean
Prevent incomplete setext headings (e.g. a line ending with --- that the parser would interpret as an <h2>) from being misrenderd during streaming. Default: true.
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comparisonOperators
boolean
Escape > as a comparison operator inside list items (e.g. - > 25 → - \> 25) to prevent the > from being interpreted as a blockquote. Default: true.
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htmlTags
boolean
Strip incomplete HTML tags at the end of streaming text (e.g. text <custom → text). Default: true.
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handlers
RemendHandler[]
Additional custom handlers to include in the pipeline. Custom handlers run after all enabled built-in handlers unless you set a lower priority.

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RemendHandler

The interface for a custom handler added via options.handlers. 
const myHandler: RemendHandler = {
  name: "remove-draft-watermark",
  handle: (text) => text.replace(/\[DRAFT\]/g, ""),
  priority: 50,
};

remend(text, { handlers: [myHandler] });
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name
string
required
A unique identifier for this handler. Used for debugging and deduplication.
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handle
(text: string) => string
required
The transformation function. Receives the current text (after all higher-priority handlers have run) and returns the modified text.
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priority
number
Execution order relative to other handlers. Lower values run first. Built-in handler priorities range from 0 to 100. Custom handlers default to 100 when this field is omitted.Built-in priorities for reference:
HandlerPriority
singleTilde0
comparisonOperators5
htmlTags10
setextHeadings15
links20
boldItalic30
bold35
italic (double underscore)40
italic (single asterisk)41
italic (single underscore)42
inlineCode50
strikethrough60
katex70
inlineKatex75
default (custom)100

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Named exports

The following utility functions are exported for use in custom handlers or other preprocessing logic.

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isWithinCodeBlock()

function isWithinCodeBlock(text: string, position: number): boolean
Returns true if position falls between a pair of triple-backtick fences in text. Useful for skipping transformations that should not affect code block contents.

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isWithinMathBlock()

function isWithinMathBlock(text: string, position: number): boolean
Returns true if position is inside an inline $...$ or block $$...$$ math expression. Handles escaped dollar signs (\$) and the precedence of block math over inline math.

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isWithinLinkOrImageUrl()

function isWithinLinkOrImageUrl(text: string, position: number): boolean
Returns true if position is inside the URL portion (...) of a Markdown link or image — i.e. between ]( and ). Useful for preventing transformations inside URLs.

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isWordChar()

function isWordChar(char: string): boolean
Returns true if char is a word character: ASCII letters (a-z, A-Z), digits (0-9), underscore (_), or any Unicode letter-or-number character outside ASCII. Uses an ASCII fast path before falling back to a Unicode regex.

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