TypeScript & Node: What's New
TypeScript and Node ship fast — TypeScript roughly quarterly, Node every six
months — and a coding model's training data lags both. This skill is a
terse, source-verified recency index: what actually shipped, what version it
landed in, and whether it's stable or still preview. It is not a tutorial
and not a house style guide — if the project you're working in has its
own coding-standards skill (canonical types, architecture, lint/tsconfig
rules), that skill is authoritative for doctrine; this one only answers "does
X exist yet, and can I use it here."
Facts here were verified against official sources (devblogs.microsoft.com/typescript,
nodejs.org/api, github.com/microsoft/TypeScript, github.com/microsoft/typescript-go,
github.com/nodejs/node) as of 2026-06-30, including empirical checks
against real installed typescript@6.0.3 and several Node binaries — not
from memory. Items marked NEEDS RE-VERIFICATION had no definitive
official source at write time; confirm before relying on them. Treat
references/tsgo-native-compiler.md as the most likely to be stale by the
time you read it — that project ships weekly.
Read the relevant reference before suggesting (or rejecting) an idiom. The
closing table in each reference file has an "Is it usable here?" column —
check the calling project's actual tsconfig.json/lib/Node version before
assuming a feature applies; "landed in TS 5.x" does not always mean "usable
under your lib/target" (see the lib-bucket gotchas in
typescript-language.md).
At a glance — stale pattern → current idiom
Every swap documented in references/*.md is listed here too, not just a
curated subset — the table in this file is the part most likely to actually
get read, since a reference file only gets opened if something already
prompted a model to go looking for it. If you only ever see this file, you
should still get most of the value; open the references for the full
explanation, code example, version sourcing, and gotchas behind any row.
TypeScript
| Instead of... |
Use... |
Lands / why |
const x: T = {...} (widens, loses literal type) |
{...} satisfies T |
TS 4.9 — keeps the literal type, still checks shape |
Caller writes as const at every call site |
<const T> type parameter |
TS 5.0 — literal type inferred without the caller doing anything |
--experimentalDecorators + reflect-metadata |
Standard @decorator syntax — but avoid entirely if your runtime executes .ts natively |
TS 5.0 syntax; Node's native type-stripper hard-rejects decorator syntax as a parser error |
try { ... } finally { cleanup() } |
using x = ... / await using x = ... |
TS 5.2 syntax (needs esnext.disposable added to lib) + Node 24+ runtime |
assert { type: "json" } |
with { type: "json" } |
TS 5.3; assert deprecation widened to dynamic import() in 6.0 |
| Splitting a function into overloads to stop a default-value arg from polluting inference |
NoInfer<T> |
TS 5.4 |
Hand-rolled (x): x is Foo => ... predicate |
Plain x => x.kind === "foo" |
TS 5.5 infers simple boolean-narrowing predicates automatically |
| Whole-program declaration emit only |
--isolatedDeclarations for per-file/parallel .d.ts emit |
TS 5.5 (no longer "experimental"; official wording stops short of "stable") |
Array.from(iter).filter(...) just to filter a generator |
.filter()/.take()/.drop() directly on the iterator |
TS 5.6 (needs ES2025/ESNext lib — not in ES2024) |
Manual set algebra (new Set([...a].filter(x => b.has(x)))) |
setA.union(setB) / .intersection() / etc. |
TS 5.5 (needs ES2025 lib) |
if (!map.has(k)) map.set(k, computeDefault()) |
map.getOrInsertComputed(k, fn) |
TS 6.0 (needs esnext lib) |
Real enum Foo { A, B } |
const Foo = {A:"a",B:"b"} as const + derived union type |
Blocked by --erasableSyntaxOnly (TS 5.8) and by Node's type-stripper outright |
Passing a Buffer where ArrayBuffer is expected implicitly |
Access .buffer explicitly |
TS 5.9 — real breaking change, not just a new capability |
Avoiding .ts extensions in source, or hand-writing .js |
Write .ts extensions; --rewriteRelativeImportExtensions rewrites them at emit |
TS 5.7 (only relevant if you add a tsc-emit build step) |
| Shipping dual CJS+ESM builds purely for require/import interop |
--module preserve (5.4) and require(esm) support under nodenext (5.8) |
TS 5.4 / 5.8 |
Eager await import() purely to delay a dependency's cost |
import defer * as ns from "..." |
TS 5.9 — namespace-only, needs runtime support, early-adopter territory |
tsc alone for typecheck |
Consider tsgo / typescript@rc |
~10x faster; RC as of 2026-06-18 — verify GA hasn't already shipped before adopting in CI |
Node.js
| Instead of... |
Use... |
Lands / why |
ts-node / tsx to run TypeScript |
node file.ts directly |
Native type stripping, Stable since Node 24.12/25.2 |
Hoping --experimental-transform-types covers enums/decorators/namespaces |
There is no native path anymore — use a real build step |
Flag removed entirely in Node 26.0.0 |
Bare specifier for a newer builtin (require('test')) |
node:test, node:sqlite, etc. |
node:-prefix is mandatory for anything added since ~Node 18, no bare alias exists |
dotenv package |
node --env-file=.env / --env-file-if-exists |
Built-in, Stable since Node 24.10/22.21 |
nodemon |
node --watch |
Built-in, Stable since Node 22.0/20.13 |
node-fetch / axios for simple calls |
global fetch |
Stable since Node 21.0 |
lodash.cloneDeep / JSON.parse(JSON.stringify(x)) |
structuredClone(x) |
Stable since Node 17.0 |
Manual setTimeout(() => ctrl.abort()) wiring |
AbortSignal.timeout(ms) / AbortSignal.any([…]) |
Built-in since Node 17.3 / 20.3 |
try { ... } finally { cleanup() } (runtime side) |
using/DisposableStack/Symbol.dispose |
Node 24.0+ (V8 13.6) — pairs with the TS-side syntax above |
Dynamic-import()-only workarounds for sync ESM-from-CJS |
require() of a synchronous ESM module |
Stable since Node 25.4 |
glob / fast-glob for simple patterns |
fs.promises.glob() |
Built-in, Stable since Node 24.0/22.17 |
minimist / yargs / commander for simple flag parsing |
util.parseArgs() |
Stable since Node 20.0 |
chalk / kleur / picocolors for simple terminal styling |
util.styleText() |
Stable since Node 23.5/22.13 |
npm run <script> / pnpm run <script> for fast single-script iteration |
node --run <script> |
Stable since Node 24.10/22.21 (not a replacement for workspace-aware orchestration) |
ws package for outbound-client-only use |
global WebSocket |
Stable since Node 22.4 (still need ws for a server) |
better-sqlite3 when you don't want a native-addon build step |
node:sqlite — Release Candidate, not Stable yet |
RC since Node 25.7 |
Also worth knowing (status facts, not swaps)
erasableSyntaxOnly (TS 5.8) is what makes the enum/decorator/parameter-property rows above compile errors instead of silent runtime breakage — pair it with verbatimModuleSyntax on any project executing .ts natively.- The
lib-bucket gotcha is general, not just for the rows above: several "landed" TS 5.5/5.6/6.0 features (iterator helpers, Set methods, using/Disposable, Map/WeakMap upsert) live in ES2025/ESNext-bucket lib files, not ES2024 — a project targeting lib: ["ES2024"] doesn't get them for free. Always check.
- TypeScript 6.0 is a version-realignment/bridge release (default-flips + deprecation wave), not a language-feature release — don't expect new syntax from it specifically.
- The permission model (
--permission) graduated to Stable at Node 23.5/22.13 — it was Experimental through Node 22 in most training data.
node:test is Stable (since Node 20.0) but situational — don't suggest migrating off an existing test runner (vitest/Jest) just because it exists.Temporal is conditionally absent on Node 26 depending on whether the binary was built with a Rust toolchain available — runtime-check typeof Temporal !== "undefined" rather than assuming target/version implies it.- Single Executable Applications (
node:sea) is still not stable (Active Development) even in Node 26 — don't assume a newer Node version implies it graduated.
References
references/typescript-language.md — TS 4.9 → 6.0.3 language and type-system
features: satisfies, decorators (and why they're likely unusable wherever
Node executes .ts natively), using/await using, const type
parameters, NoInfer, inferred type predicates, isolatedDeclarations,
erasableSyntaxOnly, iterator helpers, Set/Map builtins, the
Buffer/ArrayBuffer breaking change, and what TypeScript 6.0 actually is.references/tsgo-native-compiler.md — current status of the Go-native
TypeScript compiler (tsgo / TypeScript 7): install paths, parity with
classic tsc, performance, known monorepo gotchas, and the TS6→TS7
relationship. The single fastest-moving topic in this skill.references/node-runtime.md — Node 20 → 26 runtime/platform features:
native TS execution and its v26 removal of the transform-types escape
hatch, the node: protocol, built-in .env/watch/glob, fetch/
AbortSignal/structuredClone, the permission model, require(esm), and
explicit don't-overclaim notes on node:sqlite and Temporal.
1---2name: ts-whats-new3description: Index of TypeScript and Node.js features that postdate most coding-model training data — TS 4.9 through 6.0.3 (satisfies, using/await using, decorators, isolatedDeclarations, the tsgo/TypeScript 7 native compiler) and Node 20 through 26 (native TS execution, built-in .env/watch/test-runner, fetch/AbortSignal/structuredClone, the permission model). Load whenever writing, editing, or reviewing TypeScript or Node.js code — especially before reaching for ts-node, tsx, CommonJS require, dotenv, node-fetch, hand-rolled AbortSignal timeouts, enum, or try/finally cleanup. Also load when asked what's new in TypeScript/Node, whether a feature is stable yet, or whether tsgo/TypeScript 7 is ready to adopt.4---56# TypeScript & Node: What's New78TypeScript and Node ship fast — TypeScript roughly quarterly, Node every six9months — and a coding model's training data lags both. This skill is a10terse, source-verified recency index: what actually shipped, what version it11landed in, and whether it's stable or still preview. It is **not** a tutorial12and **not** a house style guide — if the project you're working in has its13own coding-standards skill (canonical types, architecture, lint/tsconfig14rules), that skill is authoritative for doctrine; this one only answers "does15X exist yet, and can I use it here."1617Facts here were verified against official sources (devblogs.microsoft.com/typescript,18nodejs.org/api, github.com/microsoft/TypeScript, github.com/microsoft/typescript-go,19github.com/nodejs/node) as of **2026-06-30**, including empirical checks20against real installed `typescript@6.0.3` and several Node binaries — not21from memory. Items marked **NEEDS RE-VERIFICATION** had no definitive22official source at write time; confirm before relying on them. Treat23`references/tsgo-native-compiler.md` as the most likely to be stale by the24time you read it — that project ships weekly.2526Read the relevant reference before suggesting (or rejecting) an idiom. The27closing table in each reference file has an "Is it usable here?" column —28check the calling project's actual `tsconfig.json`/`lib`/Node version before29assuming a feature applies; "landed in TS 5.x" does not always mean "usable30under your `lib`/`target`" (see the lib-bucket gotchas in31`typescript-language.md`).3233## At a glance — stale pattern → current idiom3435Every swap documented in `references/*.md` is listed here too, not just a36curated subset — the table in this file is the part most likely to actually37get read, since a reference file only gets opened if something already38prompted a model to go looking for it. If you only ever see this file, you39should still get most of the value; open the references for the full40explanation, code example, version sourcing, and gotchas behind any row.4142### TypeScript4344| Instead of... | Use... | Lands / why |45|---|---|---|46| `const x: T = {...}` (widens, loses literal type) | `{...} satisfies T` | TS 4.9 — keeps the literal type, still checks shape |47| Caller writes `as const` at every call site | `<const T>` type parameter | TS 5.0 — literal type inferred without the caller doing anything |48| `--experimentalDecorators` + `reflect-metadata` | Standard `@decorator` syntax — **but avoid entirely if your runtime executes `.ts` natively** | TS 5.0 syntax; Node's native type-stripper hard-rejects decorator syntax as a parser error |49| `try { ... } finally { cleanup() }` | `using x = ...` / `await using x = ...` | TS 5.2 syntax (needs `esnext.disposable` added to `lib`) + Node 24+ runtime |50| `assert { type: "json" }` | `with { type: "json" }` | TS 5.3; `assert` deprecation widened to dynamic `import()` in 6.0 |51| Splitting a function into overloads to stop a default-value arg from polluting inference | `NoInfer<T>` | TS 5.4 |52| Hand-rolled `(x): x is Foo => ...` predicate | Plain `x => x.kind === "foo"` | TS 5.5 infers simple boolean-narrowing predicates automatically |53| Whole-program declaration emit only | `--isolatedDeclarations` for per-file/parallel `.d.ts` emit | TS 5.5 (no longer "experimental"; official wording stops short of "stable") |54| `Array.from(iter).filter(...)` just to filter a generator | `.filter()`/`.take()`/`.drop()` directly on the iterator | TS 5.6 (needs `ES2025`/`ESNext` lib — not in `ES2024`) |55| Manual set algebra (`new Set([...a].filter(x => b.has(x)))`) | `setA.union(setB)` / `.intersection()` / etc. | TS 5.5 (needs `ES2025` lib) |56| `if (!map.has(k)) map.set(k, computeDefault())` | `map.getOrInsertComputed(k, fn)` | TS 6.0 (needs `esnext` lib) |57| Real `enum Foo { A, B }` | `const Foo = {A:"a",B:"b"} as const` + derived union type | Blocked by `--erasableSyntaxOnly` (TS 5.8) and by Node's type-stripper outright |58| Passing a `Buffer` where `ArrayBuffer` is expected implicitly | Access `.buffer` explicitly | TS 5.9 — real breaking change, not just a new capability |59| Avoiding `.ts` extensions in source, or hand-writing `.js` | Write `.ts` extensions; `--rewriteRelativeImportExtensions` rewrites them at emit | TS 5.7 (only relevant if you add a `tsc`-emit build step) |60| Shipping dual CJS+ESM builds purely for require/import interop | `--module preserve` (5.4) and `require(esm)` support under `nodenext` (5.8) | TS 5.4 / 5.8 |61| Eager `await import()` purely to delay a dependency's cost | `import defer * as ns from "..."` | TS 5.9 — namespace-only, needs runtime support, early-adopter territory |62| `tsc` alone for typecheck | Consider `tsgo` / `typescript@rc` | ~10x faster; RC as of 2026-06-18 — verify GA hasn't already shipped before adopting in CI |6364### Node.js6566| Instead of... | Use... | Lands / why |67|---|---|---|68| `ts-node` / `tsx` to run TypeScript | `node file.ts` directly | Native type stripping, Stable since Node 24.12/25.2 |69| Hoping `--experimental-transform-types` covers enums/decorators/namespaces | There is no native path anymore — use a real build step | Flag removed entirely in Node 26.0.0 |70| Bare specifier for a newer builtin (`require('test')`) | `node:test`, `node:sqlite`, etc. | `node:`-prefix is mandatory for anything added since ~Node 18, no bare alias exists |71| `dotenv` package | `node --env-file=.env` / `--env-file-if-exists` | Built-in, Stable since Node 24.10/22.21 |72| `nodemon` | `node --watch` | Built-in, Stable since Node 22.0/20.13 |73| `node-fetch` / axios for simple calls | global `fetch` | Stable since Node 21.0 |74| `lodash.cloneDeep` / `JSON.parse(JSON.stringify(x))` | `structuredClone(x)` | Stable since Node 17.0 |75| Manual `setTimeout(() => ctrl.abort())` wiring | `AbortSignal.timeout(ms)` / `AbortSignal.any([…])` | Built-in since Node 17.3 / 20.3 |76| `try { ... } finally { cleanup() }` (runtime side) | `using`/`DisposableStack`/`Symbol.dispose` | Node 24.0+ (V8 13.6) — pairs with the TS-side syntax above |77| Dynamic-`import()`-only workarounds for sync ESM-from-CJS | `require()` of a synchronous ESM module | Stable since Node 25.4 |78| `glob` / `fast-glob` for simple patterns | `fs.promises.glob()` | Built-in, Stable since Node 24.0/22.17 |79| `minimist` / `yargs` / `commander` for simple flag parsing | `util.parseArgs()` | Stable since Node 20.0 |80| `chalk` / `kleur` / `picocolors` for simple terminal styling | `util.styleText()` | Stable since Node 23.5/22.13 |81| `npm run <script>` / `pnpm run <script>` for fast single-script iteration | `node --run <script>` | Stable since Node 24.10/22.21 (not a replacement for workspace-aware orchestration) |82| `ws` package for outbound-client-only use | global `WebSocket` | Stable since Node 22.4 (still need `ws` for a server) |83| `better-sqlite3` when you don't want a native-addon build step | `node:sqlite` — **Release Candidate, not Stable yet** | RC since Node 25.7 |8485### Also worth knowing (status facts, not swaps)8687- **`erasableSyntaxOnly` (TS 5.8)** is what makes the `enum`/decorator/parameter-property rows above compile errors instead of silent runtime breakage — pair it with `verbatimModuleSyntax` on any project executing `.ts` natively.88- **The `lib`-bucket gotcha is general**, not just for the rows above: several "landed" TS 5.5/5.6/6.0 features (iterator helpers, Set methods, `using`/`Disposable`, Map/WeakMap upsert) live in `ES2025`/`ESNext`-bucket lib files, not `ES2024` — a project targeting `lib: ["ES2024"]` doesn't get them for free. Always check.89- **TypeScript 6.0** is a version-realignment/bridge release (default-flips + deprecation wave), not a language-feature release — don't expect new syntax from it specifically.90- **The permission model (`--permission`)** graduated to Stable at Node 23.5/22.13 — it was Experimental through Node 22 in most training data.91- **`node:test`** is Stable (since Node 20.0) but situational — don't suggest migrating off an existing test runner (vitest/Jest) just because it exists.92- **`Temporal`** is conditionally absent on Node 26 depending on whether the binary was built with a Rust toolchain available — runtime-check `typeof Temporal !== "undefined"` rather than assuming target/version implies it.93- **Single Executable Applications (`node:sea`)** is still not stable (Active Development) even in Node 26 — don't assume a newer Node version implies it graduated.9495## References9697- `references/typescript-language.md` — TS 4.9 → 6.0.3 language and type-system98 features: `satisfies`, decorators (and why they're likely unusable wherever99 Node executes `.ts` natively), `using`/`await using`, `const` type100 parameters, `NoInfer`, inferred type predicates, `isolatedDeclarations`,101 `erasableSyntaxOnly`, iterator helpers, Set/Map builtins, the102 `Buffer`/`ArrayBuffer` breaking change, and what TypeScript 6.0 actually is.103- `references/tsgo-native-compiler.md` — current status of the Go-native104 TypeScript compiler (tsgo / TypeScript 7): install paths, parity with105 classic `tsc`, performance, known monorepo gotchas, and the TS6→TS7106 relationship. The single fastest-moving topic in this skill.107- `references/node-runtime.md` — Node 20 → 26 runtime/platform features:108 native TS execution and its v26 removal of the transform-types escape109 hatch, the `node:` protocol, built-in `.env`/watch/glob, `fetch`/110 `AbortSignal`/`structuredClone`, the permission model, `require(esm)`, and111 explicit don't-overclaim notes on `node:sqlite` and `Temporal`.
jlreyes