# avril's Streams build

`polyfill.js` remains the unmodified upstream distribution. avril uses
`polyfill.avril.js`, generated from web-streams-polyfill 4.3.0 at commit
`12b4fedec6c01503a137d837204ca0b85992461e` with `avril.patch` applied.

The patch replaces promise rejection-suppression reactions with avril's private
`markPromiseHandled` binding. Internal observation retains its first reaction
and marks the resulting promise handled instead of attaching a second reaction.
A frozen fulfilled promise is reused by internal default algorithms, tee pulls,
and initial pipe bookkeeping. Public results, callback assimilation, and pending
backpressure promises still use separate promises. The cached promise does not
shadow `constructor`: that would invalidate V8's global promise-species
protector and slow unrelated promise operations.

Regenerate with Node.js 22+ and npm on PATH:

```sh
node exts/webstreams/src/vendor/build.mjs
```

The build fetches the pinned upstream commit, installs its locked dependencies
without lifecycle scripts, applies the readable source patch, and runs
upstream's ES2015 polyfill bundler. The license banner is copied from the
original vendored distribution rather than using the build date.