[mcollina]

The ClosedPromiseHook records that pipeTo() and tee() install as the [[closedPromise]] of their reader and writer (#66424) enqueue the watcher from whoever settles the record. As a result, the source-closed, source-errored and dest-errored steps of pipeTo() run in the async context of the code that closed or errored the stream: the destination's close()/abort() and the source's cancel() observe the wrong AsyncLocalStorage store. This is the same class of bug as #66906.

const ts = new TransformStream();
const ws = new WritableStream({ close() { console.log(als.getStore()); } });
als.run('piper', () => ts.readable.pipeTo(ws));
const w = ts.writable.getWriter();
await als.run('closer', () => w.close()); // logs 'closer', v24/v26.5 log 'piper'

This captures the async context frame when the hook is installed and registers the reaction in it, as the spec's promise reaction would.

It also adds test-whatwg-webstreams-async-context.js, which records the context each underlying source, sink and transformer callback observes across 29 readable, writable, transform, pipe and tee scenarios, so scheduling shortcuts that drop the context get caught. The expectations were taken from v24.18.0 (with and without --no-async-context-frame) and v26.5.1, which agree on all of them. Only the context of each callback is compared, not how callbacks of different streams interleave. The test also fails on the parent of 60e6c84 (the #66906 fix).

Refs: #66906
Refs: #66424

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.65%. Comparing base (29bd740) to head (e15df5f).
⚠️ Report is 223 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #67052      +/-   ##
==========================================
+ Coverage   90.47%   90.65%   +0.18%     
==========================================
  Files         791      797       +6     
  Lines      277245   278279    +1034     
  Branches    53310    53519     +209     
==========================================
+ Hits       250834   252283    +1449     
+ Misses      16811    16371     -440     
- Partials     9600     9625      +25     

Files with missing lines	Coverage Δ
lib/internal/webstreams/readablestream.js	98.36% <100.00%> (+0.25%)	⬆️

... and 140 files with indirect coverage changes

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CI: https://ci.nodejs.org/job/node-test-pull-request/78687/

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Landed in d56c163