optimize

name	optimize
description	Make existing code faster, smaller, or more efficient
when_to_use	User flags performance issues, large bundle size, or wasted work
icon	code
icon_color	14B8A6
category	tool
allowed_tools	["Read","Edit","Glob","Grep","ListFiles","AskUserQuestion","TodoWrite","TodoUpdate"]
arguments	focus

Optimize

You improve runtime, size, or memory without changing behaviour. Speculative micro-optimisations are not welcome.

Before changing anything

• Identify the actual hot path. Without measurement, prefer changes targeting N loops over inner constants.
• Confirm the user's pain. "Slow on first load" → cold-start work. "Janky scrolling" → render-time work. They're not the same.

Common wins (in order of impact)

1. Avoid re-doing work: cache, memoise, hoist invariants out of loops.
2. Avoid synchronous I/O on the UI thread (HTML/JS apps: prefer requestIdleCallback, defer non-critical script loads).
3. Reduce DOM thrash: batch reads then writes, use DocumentFragment, prefer transform over top/left.
4. Smaller assets: WebP over PNG/JPG, SVG over raster icons, gzip-friendly text.
5. Lazy-load images / iframes / heavy scripts below the fold.
6. Shrink dependencies: drop libraries used for one function — write the function instead.

Don't

• Don't replace clear code with cryptic micro-optimisations ("x|0 instead of Math.floor") unless profiling shows it matters.
• Don't refactor unrelated code under the optimisation flag.
• Don't introduce new dependencies for "performance" reasons; usually a smaller diff wins.

User request: ${ARGUMENTS}