ng build hangs after a successful build on @angular/build 21.2.14–21.2.18 (regression from #33267)

[hskiba]

Command

build

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

21.2.13

Description

ng build (no --watch) finishes successfully. It prints the build summary and "Output location," then the process never exits. A lingering esbuild --service=<version> --ping child stays alive next to the still-running ng build parent, and both have to be killed by hand.

This looks like a regression from #33267 (merged in 21.2.14), which switched one-shot builds from a plain esbuild.build() call to esbuild.context() + .rebuild(), the persistent-IPC path normally reserved for watch mode. That PR fixed a real leak (#33201), but seems to have opened a scheduling/teardown race for one-shot builds instead.

This was already filed as #33480 and closed for lack of a reproducible case. I put together a minimal repro from scratch to close that gap.

Minimal Reproduction

Repo: https://github.com/hskiba/ng-build-hang-repro

git clone https://github.com/hskiba/ng-build-hang-repro
cd ng-build-hang-repro
npm install
npx ng build

The build finishes, then hangs. ps aux | grep esbuild in another terminal shows the stuck service process.

Three commits show exactly what triggers it:

1. initial commit: untouched ng new output, builds and exits fine
2. Add minimal trigger...: adds one file with two trivial @Component classes, each with nothing but an inline styles: block. It's never imported or routed anywhere, only picked up via tsconfig.app.json's include: ["src/**/*.ts"]. Adding it alone causes the hang.
3. Document root cause...: full writeup

What I found bisecting it: the count of components with inline styles: blocks is what matters. Two hangs it, one doesn't. CSS content is irrelevant, a bare :host { display: block; } triggers it just as reliably as anything more elaborate. Host bindings, signals, file size, and third-party dependencies are all beside the point. Pinning to 21.2.13 with the identical source file builds and exits cleanly.

Exception or Error

none (never exits)

Your Environment

Angular CLI       : 21.2.18
Angular           : 21.2.17
Node.js           : 24.18.0
Package Manager   : npm 11.16.0
Operating System  : darwin arm64

@angular/build            21.2.18
@angular/cli              21.2.18
@angular/common           21.2.17
@angular/compiler          21.2.17
@angular/compiler-cli      21.2.17
@angular/core              21.2.17
@angular/forms             21.2.17
@angular/platform-browser  21.2.17
@angular/router            21.2.17
rxjs                       7.8.2
typescript                 5.9.3
vitest                     4.1.9

Anything else relevant?

Reproduced on macOS (arm64) and was happening in our container builds for both arm64 and amd64.