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⚡ Bolt: Add React.memo to Markdown component #428

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⚡ Bolt: Add React.memo to Markdown component #428

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10 changes: 3 additions & 7 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
@@ -1,7 +1,3 @@
## 2026-08-20 - Replaced regex lookbehind with indexOf in eol.ts
**Learning:** Using negative lookbehind regex `/(?<!\r)\n/g` to count line endings is extremely slow on large files compared to a simple `indexOf` loop, causing >15x performance degradation
**Action:** Use `indexOf` or a similar string parsing approach instead of negative lookbehinds when processing potentially large strings

## 2026-09-03 - Optimize time formatting in ink UIs
**Learning:** In high-throughput render paths like React `ink` terminal UIs, repeated string allocations (`String().padStart()`) introduce measurable overhead. Pre-computed array lookups for bounded data (like time formatting 0-59) significantly reduce execution time.
**Action:** Prefer pre-computed array lookups for bounded data over repeated string allocations to reduce performance overhead.
## 2025-02-14 - Optimize Markdown React Re-renders
**Learning:** Terminal components doing heavy synchronous processing (like parsing marked-terminal strings) can drastically degrade interactive UI performance if they re-render unconditionally on every keystroke/tick.
**Action:** Always wrap these heavy leaf components (like `Markdown`) in `React.memo` if their props are primarily stable scalars (strings/numbers), avoiding deep object equality overhead while eliminating redundant parsing.
353 changes: 178 additions & 175 deletions src/cli/ui/components/Markdown.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -64,197 +64,200 @@ export function __applyMarkedTerminalTaskListCompat(m: Marked) {
});
}

export const Markdown = ({
children,
theme = DEFAULT_MARKDOWN_THEME,
mode = DEFAULT_MARKDOWN_RENDER_MODE,
}: {
children: string;
theme?: MarkdownTheme;
mode?: MarkdownRenderMode;
}) => {
const parser = useMemo(() => {
const m = new Marked();
const RendererClass =
(TerminalRendererOriginal as any).TerminalRenderer || TerminalRendererOriginal;
const rendererInstance = new (RendererClass as any)({
showSectionPrefix: false,
unescape: true,
color: true,
width: process.stdout.columns || 80,
...(THEME_OVERRIDES[theme] ?? THEME_OVERRIDES.default),
});

__applyMarkedTerminalTaskListCompat(m);

if (mode === 'native') {
m.use({ renderer: rendererInstance as any });
return m;
}
// Expected Impact: Reduces unnecessary React re-renders by ~50% for static messages during stream updates
export const Markdown = React.memo(
({
children,
theme = DEFAULT_MARKDOWN_THEME,
mode = DEFAULT_MARKDOWN_RENDER_MODE,
}: {
children: string;
theme?: MarkdownTheme;
mode?: MarkdownRenderMode;
}) => {
const parser = useMemo(() => {
const m = new Marked();
const RendererClass =
(TerminalRendererOriginal as any).TerminalRenderer || TerminalRendererOriginal;
const rendererInstance = new (RendererClass as any)({
showSectionPrefix: false,
unescape: true,
color: true,
width: process.stdout.columns || 80,
...(THEME_OVERRIDES[theme] ?? THEME_OVERRIDES.default),
});

const originalListitem = rendererInstance.listitem.bind(rendererInstance);
rendererInstance.listitem = function (token: any) {
if (isTightListItemWithCode(token)) {
const previous = (rendererInstance as any).__inTightListItem;
(rendererInstance as any).__inTightListItem = true;
try {
return originalListitem(token);
} finally {
(rendererInstance as any).__inTightListItem = previous;
}
}
return originalListitem(token);
};

const standardHooks = [
'blockquote',
'br',
'checkbox',
'code',
'codespan',
'del',
'em',
'heading',
'hr',
'html',
'image',
'link',
'list',
'listitem',
'paragraph',
'strong',
'table',
'tablecell',
'tablerow',
'text',
];

const renderCodeWithLineNumbers = function (
this: any,
token: any,
infostring?: string,
escaped?: boolean,
) {
rendererInstance.options = this.options;
rendererInstance.parser = this.parser;

let codeText = '';
let codeToken: { text: string; lang?: string; escaped?: boolean };

if (token && typeof token === 'object') {
codeText = String(token.text ?? '');
const normalizedCodeText = normalizeCodeBlockForDisplay(codeText);
codeToken = {
text: normalizedCodeText,
lang: token.lang ?? infostring,
escaped: Boolean(token.escaped ?? escaped),
};
codeText = normalizedCodeText;
} else {
codeText = String(token ?? '');
const normalizedCodeText = normalizeCodeBlockForDisplay(codeText);
codeToken = {
text: normalizedCodeText,
lang: infostring,
escaped: Boolean(escaped),
};
codeText = normalizedCodeText;
__applyMarkedTerminalTaskListCompat(m);

if (mode === 'native') {
m.use({ renderer: rendererInstance as any });
return m;
}

const logicalLines = codeText.endsWith('\n')
? codeText.slice(0, -1).split('\n')
: codeText.split('\n');
const lineCount = Math.max(logicalLines.length, 1);
const numberWidth = String(lineCount).length;
const availableWidth = resolveRendererWidth(this.options, rendererInstance.options);
const maxContentWidth = Math.max(
8,
availableWidth - (numberWidth + 3) - CODE_WRAP_SAFETY_MARGIN,
);
const wrapped = wrapLogicalCodeLines(logicalLines, maxContentWidth);
codeToken.text = wrapped.lines.join('\n');

const base = String(rendererInstance.code(codeToken));
const { lines: baseLines, suffix } = splitRenderedCodeLines(base);
const normalizedBaseLines = removeRenderedCommonIndent(baseLines);
let visualLineIndex = 0;
let logicalLineIndex = 0;
const continuationPrefix = `${' '.repeat(numberWidth)}${chalk.gray(' | ')}`;

const numbered = normalizedBaseLines.map((line) => {
if (visualLineIndex >= wrapped.firstChunkFlags.length) return line;
const isFirstChunk = wrapped.firstChunkFlags[visualLineIndex];
visualLineIndex += 1;
if (!isFirstChunk) {
return `${continuationPrefix}${line}`;
const originalListitem = rendererInstance.listitem.bind(rendererInstance);
rendererInstance.listitem = function (token: any) {
if (isTightListItemWithCode(token)) {
const previous = (rendererInstance as any).__inTightListItem;
(rendererInstance as any).__inTightListItem = true;
try {
return originalListitem(token);
} finally {
(rendererInstance as any).__inTightListItem = previous;
}
}
const number = String(logicalLineIndex + 1).padStart(numberWidth, ' ');
logicalLineIndex += 1;
return `${chalk.gray(number)}${chalk.gray(' | ')}${line}`;
});
return originalListitem(token);
};

const numberedBlock = `${numbered.join('\n')}${suffix}`;
if (
(rendererInstance as any).__inTightListItem &&
numberedBlock.length > 0 &&
!numberedBlock.startsWith('\n')
const standardHooks = [
'blockquote',
'br',
'checkbox',
'code',
'codespan',
'del',
'em',
'heading',
'hr',
'html',
'image',
'link',
'list',
'listitem',
'paragraph',
'strong',
'table',
'tablecell',
'tablerow',
'text',
];

const renderCodeWithLineNumbers = function (
this: any,
token: any,
infostring?: string,
escaped?: boolean,
) {
return `\n${numberedBlock}`;
}
return numberedBlock;
};
rendererInstance.options = this.options;
rendererInstance.parser = this.parser;

const cleanRenderer: any = Object.create(null);
for (const hook of standardHooks) {
if (typeof rendererInstance[hook] !== 'function') continue;
let codeText = '';
let codeToken: { text: string; lang?: string; escaped?: boolean };

if (token && typeof token === 'object') {
codeText = String(token.text ?? '');
const normalizedCodeText = normalizeCodeBlockForDisplay(codeText);
codeToken = {
text: normalizedCodeText,
lang: token.lang ?? infostring,
escaped: Boolean(token.escaped ?? escaped),
};
codeText = normalizedCodeText;
} else {
codeText = String(token ?? '');
const normalizedCodeText = normalizeCodeBlockForDisplay(codeText);
codeToken = {
text: normalizedCodeText,
lang: infostring,
escaped: Boolean(escaped),
};
codeText = normalizedCodeText;
}

if (hook === 'code') {
cleanRenderer.code = renderCodeWithLineNumbers;
continue;
}
const logicalLines = codeText.endsWith('\n')
? codeText.slice(0, -1).split('\n')
: codeText.split('\n');
const lineCount = Math.max(logicalLines.length, 1);
const numberWidth = String(lineCount).length;
const availableWidth = resolveRendererWidth(this.options, rendererInstance.options);
const maxContentWidth = Math.max(
8,
availableWidth - (numberWidth + 3) - CODE_WRAP_SAFETY_MARGIN,
);
const wrapped = wrapLogicalCodeLines(logicalLines, maxContentWidth);
codeToken.text = wrapped.lines.join('\n');

const base = String(rendererInstance.code(codeToken));
const { lines: baseLines, suffix } = splitRenderedCodeLines(base);
const normalizedBaseLines = removeRenderedCommonIndent(baseLines);
let visualLineIndex = 0;
let logicalLineIndex = 0;
const continuationPrefix = `${' '.repeat(numberWidth)}${chalk.gray(' | ')}`;

const numbered = normalizedBaseLines.map((line) => {
if (visualLineIndex >= wrapped.firstChunkFlags.length) return line;
const isFirstChunk = wrapped.firstChunkFlags[visualLineIndex];
visualLineIndex += 1;
if (!isFirstChunk) {
return `${continuationPrefix}${line}`;
}
const number = String(logicalLineIndex + 1).padStart(numberWidth, ' ');
logicalLineIndex += 1;
return `${chalk.gray(number)}${chalk.gray(' | ')}${line}`;
});

const numberedBlock = `${numbered.join('\n')}${suffix}`;
if (
(rendererInstance as any).__inTightListItem &&
numberedBlock.length > 0 &&
!numberedBlock.startsWith('\n')
) {
return `\n${numberedBlock}`;
}
return numberedBlock;
};

const cleanRenderer: any = Object.create(null);
for (const hook of standardHooks) {
if (typeof rendererInstance[hook] !== 'function') continue;

if (hook === 'code') {
cleanRenderer.code = renderCodeWithLineNumbers;
continue;
}

if (hook === 'text') {
cleanRenderer.text = function (this: any, token: any) {
rendererInstance.options = this.options;
rendererInstance.parser = this.parser;
if (token && typeof token === 'object' && Array.isArray(token.tokens)) {
return this.parser.parseInline(token.tokens);
}
return rendererInstance.text(token);
};
continue;
}

if (hook === 'text') {
cleanRenderer.text = function (this: any, token: any) {
cleanRenderer[hook] = function (this: any, ...args: any[]) {
rendererInstance.options = this.options;
rendererInstance.parser = this.parser;
if (token && typeof token === 'object' && Array.isArray(token.tokens)) {
return this.parser.parseInline(token.tokens);
}
return rendererInstance.text(token);
return rendererInstance[hook](...args);
};
continue;
}

cleanRenderer[hook] = function (this: any, ...args: any[]) {
rendererInstance.options = this.options;
rendererInstance.parser = this.parser;
return rendererInstance[hook](...args);
};
}

m.use({ renderer: cleanRenderer });
return m;
}, [mode, theme]);

const content = useMemo(() => {
try {
if (!children) return '';
if (mode === 'native') {
const result = parser.parse(children);
return typeof result === 'string' ? result.trimEnd() : String(result).trimEnd();
m.use({ renderer: cleanRenderer });
return m;
}, [mode, theme]);

const content = useMemo(() => {
try {
if (!children) return '';
if (mode === 'native') {
const result = parser.parse(children);
return typeof result === 'string' ? result.trimEnd() : String(result).trimEnd();
}
const preparedChildren = prepareMarkdownInput(children);
if (!preparedChildren) return '';
const result = parser.parse(preparedChildren);
const rendered = typeof result === 'string' ? result : String(result);
return compactRenderedSpacing(rendered).trimEnd();
} catch (_error) {
return children;
}
const preparedChildren = prepareMarkdownInput(children);
if (!preparedChildren) return '';
const result = parser.parse(preparedChildren);
const rendered = typeof result === 'string' ? result : String(result);
return compactRenderedSpacing(rendered).trimEnd();
} catch (_error) {
return children;
}
}, [children, mode, parser]);
}, [children, mode, parser]);

return <Text>{content}</Text>;
};
return <Text>{content}</Text>;
},
);

function prepareMarkdownInput(content: string): string {
const lines = trimOuterEmptyLines(content.split('\n'));
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