Bun

Bun is the only runtime + package manager.

MUST

Use only bun. Why: one toolchain, no manager drift.
bun fix passes before done. Why: lint/format gate.
Update deps via bun clean && bun i. Why: refreshes "latest" cleanly.
All deps "latest"; WHEN a pin is unavoidable, pin major only ("eslint": "9"). Why: no legacy lock-in.
Every direct dep shows an upstream release within ~6 months; replace an abandoned or archived dep, never keep it. Why: stale-but-stable rots — force the migration early.
A newly required CLI or dep lands in package.json (or the documented setup script) the same turn it is first used. Why: never re-litigate the install next session.
import { X } from 'bun' ($, file, write, Glob, spawn, …) in bun-runtime apps (CLI, standalone server). Why: explicit + tree-shakeable; Bun is a registered biome global so either form lints clean.
Use the Bun global (Bun.S3Client, Bun.s3, …) in Next/Turbopack apps. Why: import { X } from 'bun' is unresolvable in next build's Node page-data-collection workers; the global needs no module resolution, so it survives the build and resolves under the bun runtime.
Run bun i immediately after renaming a workspace name:. Why: dependents resolve old name via stale node_modules/<scope>/ symlink.
Read an opaque eslint ResolveMessage {} as a stale workspace symlink → reinstall first. Why: it masks every other violation; not a lint-internals bug.
Scripts silent on success, verbose on failure. Why: agent context budget.