When an algorithm derives a decision key (dedupe) or signal (parsed config) that can suppress/merge data, make that derivation collision- and normalization-safe, and define precedence explicitly. **Dedupe keys (avoid collision-based suppression):** - Don’t rely on short/non-unique hashes (e.g., 32-bit) when a collision would silently drop valid items. - Prefer a collision-resistant digest of the actual bytes (e.g., SHA-256), or use a two-phase approach: quick hash + byte-by-byte comparison as a tie-breaker. ```ts import { createHash } from 'node:crypto' export function imageDedupeKey(blob: Blob, data: Uint8Array): string { // Collision-resistant key: hash actual bytes (optionally include size) const digest = createHash('sha256').update(data).digest('hex') return `${blob.size}|${digest}` } ``` **Parsed/merged config (normalize + deterministic precedence):** - Normalize inputs (commonly casing) before evaluating “inherited vs system” or “user vs system.” - Define precedence rules in one place (e.g., “if any inherited proxy spelling is set, skip all system injection”), and cover mixed-case regression tests. ```ts function hasAnyInheritedProxy(env: Record, family: 'http'|'https') { const keys = [ `${family}_proxy`, `${family.toUpperCase()}_PROXY` ] return keys.some(k => (env[k] ?? '').length > 0) } ``` **Why:** these patterns prevent subtle, hard-to-debug behavior like “silent suppression” from hash collisions and inconsistent merging from incomplete normalization/precedence handling.