How do you diagnose slow rendering in an Angular application?

If Angular repeatedly checks a large subtree, I inspect unstable inputs, template calls, timers, event listeners, and whether OnPush or zoneless notifications would reduce unnecessary work. If one component is expensive, I move heavy derivation out of the template, cache only pure work, reduce DOM size, or virtualize a genuinely large list. I also inspect layout thrashing and third-party widgets because an Angular flame chart does not explain every browser cost. One synthetic benchmark is backed by a representative device and dataset.