Agent Guide: arcgis-performance

Quick-reference for performance work (SDK 5.1). Read before tuning a slow or leaky app.

Quick Decision Tree

1. WebGL contexts lost / memory grows? → view.destroy() on unmount (view.map = null first to keep the map).
2. Jank on pan/zoom? → watch view.stationary; minScale/maxScale; featureReduction; layer.visible.
3. Big bundle? → per-module imports and only the components you render; import() helps little (24 KB measured).

Setup Checklist

• Every view is destroyed on unmount.
• A shared map is detached (view.map = null) before destroy().
• Every watch/on handle is removed.
• No per-frame work: watch settled state.
• Detail layers have a scale range.

Anti-patterns (one-liner reminders)

• ❌ container.innerHTML = "" as teardown (views stay alive).
• ❌ view.destroy() and then reusing its map (destroyed with it).
• ❌ watch(() => view.center, ...) for heavy work (92 fires per goTo).
• ❌ import ... from "@arcgis/core" or "@arcgis/core/layers" (do not resolve).

Files in This Skill

• SKILL.md / SKILL.es.md — full guides
• references/api-detail.md — lifecycle, watches, draw controls, bundle numbers
• references/examples.md — teardown, settled watches, scale ranges
• references/pitfalls.md — extended troubleshooting
• scripts/snippet-cleanup.ts, snippet-lazy-import.ts