# expressots: what changed from 3 to 4

- Product: expressots (https://whatsnew.fyi/product/expressots)
- Vendor: expressots
- Range: changelog entries numbered after 3.0.0 up to and including v4.2.1, stable releases only
- Entries below: 5 releases (newest first)
- Resolved: 3 is 3.0.0 and 4 is v4.2.1, the newest stable release of each major we track
- Carrying security changes: 0 · CVEs mentioned: 0 · Mentioning breaking changes: 1 · Removing or deprecating something: 1
- Page: https://whatsnew.fyi/product/expressots/compare/3...4

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

## What changed (19 changes, grouped by kind)

### Added

#### v4.2.0 (2026-08-03)

- Add scaffold command for Cloudflare Workers micro targets
- Add pack:local --link option to wire a test app to a local build

#### v4.0.0 (2026-07-17)

- Subpath exports for @expressots/core/testing, /di, /render, and /path-resolver
- validationRegistry singleton for validation with optional peer dependencies for zod, yup, and class-validator
- llms.txt file shipped in the package for agent support

### Changed

#### v4.2.1 (2026-08-04)

- Reduce Worker bundle size by 62%

#### v4.1.0 (2026-07-27)

- Migrate to monorepo structure

#### v4.0.0 (2026-07-17)

- Bootstrap API now uses bootstrap(App) with AppExpress; AppFactory is now internal
- Strict TypeScript with strictNullChecks and noImplicitAny enabled across the codebase
- Reduced package size by ~0.8 MB unpacked with single shared declaration tree and sideEffects declared for safe tree-shaking
- Node.js >= 20.19.0 is now required

### Fixed

#### v4.2.1 (2026-08-04)

- Fix createTestApp under Jest

#### v4.2.0 (2026-08-03)

- Fix response fidelity and working lifecycle hooks on serverless targets
- Fix request fidelity on Workers and test Worker scaffolds on workerd

### Removed

#### v4.0.0 (2026-07-17)

- Deprecated root AppFactory export
- Removed v3 InMemoryDataProvider and InMemoryDataTable
- Removed LazyServiceIdentifer typo alias
- Removed Logger#formatMessage method
- Removed AppContainer#viewContainerBindings

_One release carries no categorized changes yet: v4.1.1._

## Release notes

### v4.2.1 — ExpressoTS 4.2.1

- Date: 2026-08-04
- Version: v4.2.1
- Original notes: https://github.com/expressots/expressots/releases/tag/v4.2.1
- Permalink: https://whatsnew.fyi/product/expressots/releases/v4.2.1

- **changed** — Reduce Worker bundle size by 62%
- **fixed** — Fix createTestApp under Jest

##### What's Changed
* perf: cut the Worker bundle 62% + fix createTestApp under Jest by @rsaz in https://github.com/expressots/expressots/pull/961


**Full Changelog**: https://github.com/expressots/expressots/compare/v4.2.0...v4.2.1

### v4.2.0 — ExpressoTS 4.2.0

- Date: 2026-08-03
- Version: v4.2.0
- Original notes: https://github.com/expressots/expressots/releases/tag/v4.2.0
- Permalink: https://whatsnew.fyi/product/expressots/releases/v4.2.0

- **added** — Add scaffold command for Cloudflare Workers micro targets
- **fixed** — Fix response fidelity and working lifecycle hooks on serverless targets
- **fixed** — Fix request fidelity on Workers and test Worker scaffolds on workerd
- **added** — Add pack:local --link option to wire a test app to a local build

##### What's Changed
* feat(cli): scaffold Cloudflare Workers micro targets by @xgame92 in https://github.com/expressots/expressots/pull/946
* fix(adapter): response fidelity and working lifecycle hooks on serverless targets by @rsaz in https://github.com/expressots/expressots/pull/957
* fix(adapter): request fidelity on Workers; test Worker scaffolds on workerd by @rsaz in https://github.com/expressots/expressots/pull/958
* chore(tooling): add pack:local --link to wire a test app to a local build by @rsaz in https://github.com/expressots/expressots/pull/960

##### New Contributors
* @xgame92 made their first contribution in https://github.com/expressots/expressots/pull/946

**Full Changelog**: https://github.com/expressots/expressots/compare/v4.1.1...v4.2.0

### v4.1.1 — ExpressoTS 4.1.1

- Date: 2026-07-27
- Version: v4.1.1
- Original notes: https://github.com/expressots/expressots/releases/tag/v4.1.1
- Permalink: https://whatsnew.fyi/product/expressots/releases/v4.1.1

**Full Changelog**: https://github.com/expressots/expressots/compare/v4.1.0...v4.1.1

### v4.1.0 — ExpressoTS 4.1.0

- Date: 2026-07-27
- Version: v4.1.0
- Original notes: https://github.com/expressots/expressots/releases/tag/v4.1.0
- Permalink: https://whatsnew.fyi/product/expressots/releases/v4.1.0

- **changed** — Migrate to monorepo structure

##### What's Changed
* Monorepo migration (v4.1.0 structure) by @rsaz in https://github.com/expressots/expressots/pull/913
* chore(deps): bump the minor-and-patch group with 5 updates by @dependabot[bot] in https://github.com/expressots/expressots/pull/935


**Full Changelog**: https://github.com/expressots/expressots/compare/v4.0.0...v4.1.0

### v4.0.0 — ExpressoTS 4.0.0

- Date: 2026-07-17
- Version: v4.0.0
- Original notes: https://github.com/expressots/expressots/releases/tag/v4.0.0
- Permalink: https://whatsnew.fyi/product/expressots/releases/v4.0.0

- **changed** — Bootstrap API now uses bootstrap(App) with AppExpress; AppFactory is now internal
- **added** — Subpath exports for @expressots/core/testing, /di, /render, and /path-resolver
- **changed** — Strict TypeScript with strictNullChecks and noImplicitAny enabled across the codebase
- **changed** — Reduced package size by ~0.8 MB unpacked with single shared declaration tree and sideEffects declared for safe tree-shaking
- **added** — validationRegistry singleton for validation with optional peer dependencies for zod, yup, and class-validator
- **added** — llms.txt file shipped in the package for agent support
- **removed** — Deprecated root AppFactory export
- **removed** — Removed v3 InMemoryDataProvider and InMemoryDataTable
- **removed** — Removed LazyServiceIdentifer typo alias
- **removed** — Removed Logger#formatMessage method
- **removed** — Removed AppContainer#viewContainerBindings
- **changed** — Node.js >= 20.19.0 is now required

ExpressoTS 4.0.0 — stable release of the v4 line.

##### Highlights

- **Bootstrap-first API**: `bootstrap(App)` with `AppExpress`; `AppFactory` is now internal
- **Subpath exports**: `@expressots/core/testing`, `/di`, `/render`, `/path-resolver`
- **Strict TypeScript**: `strictNullChecks` + `noImplicitAny` enabled across the codebase
- **Leaner install**: single shared declaration tree (~0.8 MB smaller unpacked, 879 files), `sideEffects` declared for safe tree-shaking
- **Validation**: `validationRegistry` singleton; optional peers for `zod`, `yup`, `class-validator`
- **Agent-ready**: `llms.txt` ships in the package
- **TypeScript 7-clean configs** with a `ts7-compat` CI gate (toolchain remains TS 5.x)

##### Breaking changes

- Removed deprecated APIs: root `AppFactory` export, v3 `InMemoryDataProvider`/`InMemoryDataTable`, `LazyServiceIdentifer` typo alias, `Logger#formatMessage`, `AppContainer#viewContainerBindings`
- Node.js >= 20.19.0 required

Full details in [CHANGELOG.md](https://github.com/expressots/expressots/blob/main/CHANGELOG.md).