Bundle size is one of the highest-impact performance levers in frontend, and most guides stop at `React.lazy`. We want the real-world version.
## What it should cover
- How to measure first: bundle analyzers, what numbers actually matter
- Route-based vs component-based splitting, when each is worth it
- Common traps: barrel files, accidentally bundling large libs, duplicate dependencies
- A before/after example with real numbers (even from a side project!)
## Where it goes
`performance/reducing-bundle-size-with-code-splitting.md`
## Bonus
If you've done this on a production app, include the actual impact (load time, bundle KB). Measurements > theory.
