nodejs

One thread runs every callback in a Node process, so anything that holds it holds the whole program. Three biases decide most calls:

• The engines.node floor decides what may be written, not the node binary on the machine.
• Read an API's stability index before depending on it. Node ships an API for years before committing to it, and an experimental one can be deleted without a deprecation cycle.
• Check the standard library before adding a dependency. It absorbed fetch, a test runner, a file watcher, glob, SQLite, .env parsing, a script runner, and TypeScript execution.

Node Version

engines.node in package.json is the floor a project claims. Read it before writing code and never reach for an API above it. Nothing enforces it at run time — Node never reads the field, and npm checks it only under engine-strict=true — so the floor holds by discipline and by CI running the oldest major it names.

The installed binary is not the floor. node --version reports what one machine has, not what the project supports.

Support windows, which decide whether a floor is defensible:

• 20 — end of life 2026-04-30. A floor of >=20 claims a runtime that receives no fixes at all.
• 22 — maintenance from 2025-10-21, end of life 2027-04-30. Security and critical fixes only; no new capability.
• 24 — Active LTS from 2025-10-28, maintenance from 2026-10-20, end of life 2028-04-30.
• 26 — released 2026-05-05, Active LTS from 2026-10-28, end of life 2029-04-30.

Floor version per feature — the APIs and behavior changes that decide what may be written.

• 20.19.0 — require(esm) unflagged on the 20 line; syntax detection on by default
• 22.0.0 — node --run; fs.glob; WebSocket global; watch mode Stable; assert { type: 'json' } removed
• 22.12.0 — require(esm) unflagged on the 22 line; JSON modules Stable
• 22.13.0 — Permission Model Stable and --permission accepted; node:sqlite unflagged
• 22.15.0 — module.registerHooks()
• 22.16.0 — import.meta.dirname and import.meta.filename Stable; --experimental-config-file
• 22.18.0 — type stripping on by default; import.meta.main
• 22.21.0 — --env-file Stable; NODE_USE_ENV_PROXY
• 24.0.0 — --experimental-permission renamed --permission; AsyncLocalStorage on AsyncContextFrame; URLPattern global; test runner awaits subtests; url.parse() runtime-deprecated (DEP0169); args with { shell: true } runtime-deprecated (DEP0190)
• 24.12.0 — type stripping Stable
• 24.20.0 — --permission-audit
• 26.0.0 — Temporal global; module.register() runtime-deprecated (DEP0205); --experimental-transform-types removed; node:_stream_* removed. It also inherits what 25 added and neither 22 nor 24 received: --allow-net, and with it network confinement under --permission
• 26.3.0 — permission.drop()

No odd major is a defensible floor. Node 21, 23, and 25 are end of life — 25 since 2026-06-01 — so a feature that arrived on one is reachable only from the LTS major above it.

Read [${CLAUDE_SKILL_DIR}/references/versions/node-NN.md] — one file per LTS major: node-20.md, node-22.md, node-24.md, node-26.md — when writing against a feature near the floor, and whenever raising the floor. Each carries what its major added, the stability each addition holds, the behavior it changed, and the traps it introduced.