---
description: Prefer Record<K, V> for small static literals; use Set/Map for anything dynamic
condition:
  # Every literal, comment, type argument and Map value is read as an unrolled loop (`a*(?:b a*)*`):
  # each delta of a streamed line rescans the unfinished line, so a long value must cost one pass.
  # The array must be the whole argument: the token after it is the constructor's `)`, a trailing `,`
  # or an `as`/`satisfies` clause, never a call such as `.map(…)`. Only that token is read, not the type.
  - "\\bnew\\s+Set\\s*(?:<[^<>;()=]*(?:(?:=>?|<[^<>;]*>|\\([^()]*\\))[^<>;()=]*)*>)?\\s*\\((?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\[(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60$\\\\]*(?:(?:\\\\[\\s\\S]|\\$(?!\\{))[^\\x60$\\\\]*)*\\x60)(?:(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60$\\\\]*(?:(?:\\\\[\\s\\S]|\\$(?!\\{))[^\\x60$\\\\]*)*\\x60))*(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,?(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\](?=(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:[),]|(?:as|satisfies)(?![\\w$])))"
  # A Map whose line runs past 1000 characters is not a small table, so the condition stops there.
  - "\\bnew\\s+Map(?![^\\n]{1000})\\s*(?:<[^<>;()=]*(?:(?:=>?|<[^<>;]*>|\\([^()]*\\))[^<>;()=]*)*>)?\\s*\\((?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\[(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\[(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60$\\\\]*(?:(?:\\\\[\\s\\S]|\\$(?!\\{))[^\\x60$\\\\]*)*\\x60)(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,[^\\[\\]\"'\\x60]*(?:(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60\\\\]*(?:\\\\[\\s\\S][^\\x60\\\\]*)*\\x60|\\[[^\\[\\]]*\\])[^\\[\\]\"'\\x60]*)*\\](?:(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*as\\s+const(?![\\w$]))?(?:(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\[(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60$\\\\]*(?:(?:\\\\[\\s\\S]|\\$(?!\\{))[^\\x60$\\\\]*)*\\x60)(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,[^\\[\\]\"'\\x60]*(?:(?:\"[^\"\\\\\\n]*(?:\\\\.[^\"\\\\\\n]*)*\"|'[^'\\\\\\n]*(?:\\\\.[^'\\\\\\n]*)*'|\\x60[^\\x60\\\\]*(?:\\\\[\\s\\S][^\\x60\\\\]*)*\\x60|\\[[^\\[\\]]*\\])[^\\[\\]\"'\\x60]*)*\\](?:(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*as\\s+const(?![\\w$]))?)*(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*,?(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*\\](?=(?:\\s|//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/)*(?:[),]|(?:as|satisfies)(?![\\w$])))"
scope: "tool:edit(**/*.{ts,tsx}), tool:write(**/*.{ts,tsx})"
interruptMode: never
---

Small, static string-keyed lookup tables: `Record<K, V>` / `Record<K, true>`.

`Set` / `Map`: dynamic/non-string keys; runtime insertion/deletion; `.size`, `.clear()`, stable insertion order, or iterator APIs.

```typescript
// Static literal → Record
const LABEL_BY_KIND: Record<string, string> = {
	text: "Text",
	json: "JSON",
	binary: "Binary",
};

// Dynamic membership → Set
const seen = new Set<string>();
for (const item of items) {
	if (seen.has(item.id)) continue;
	seen.add(item.id);
}
```