stream: expose ReadableStreamTee

[mcollina]

Refs: nodejs/undici#5358

Expose ReadableStreamTee() so Fetch body clone can use cloneForBranch2.

[nodejs-github-bot]

Review requested:

• @nodejs/streams

[MattiasBuelens]

I don't know if we should be exposing this as a top-level function. At the very least, we should mark ReadableStreamTee() as experimental and guide users towards readableStream.tee() for "common" use cases.

Ideally, we land on a solution in the Streams standard itself. The current proposal is to add an options bag to tee(), so you could write readableStream.tee({ clone: true }). Tracking issue: whatwg/streams#1156.

[KhafraDev]

Ideally, we land on a solution in the Streams standard itself. The current proposal is to add an options bag to tee(), so you could write readableStream.tee({ clone: true }). Tracking issue: whatwg/streams#1156.

This would be great, but it doesn't look like browsers have any interest in implementing it, considering the issue is nearly 5 years old.

[mcollina]

@KhafraDev @MattiasBuelens should we expose this verbatim or change the name to webStreams.tee(stream, opts)

[KhafraDev]

ReadableStreamTee might be a little verbose. Honestly the only reason I didn't try implementing this myself was because I don't particularly like the verbose name, but didn't have any better ideas

[nodejs-github-bot]

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----------------------------------- PR info ------------------------------------
Title      stream: expose ReadableStreamTee (#64195)
Author     Matteo Collina <matteo.collina@gmail.com> (@mcollina)
Branch     mcollina:expose-readable-stream-tee -> nodejs:main
Labels     stream, semver-minor, commit-queue-squash
Commits    2
 - stream: expose ReadableStreamTee
 - doc: mark ReadableStreamTee as experimental
Committers 1
 - Matteo Collina <hello@matteocollina.com>
PR-URL: https://github.com/nodejs/node/pull/64195
Refs: https://github.com/nodejs/undici/issues/5358
Reviewed-By: Matthew Aitken <maitken033380023@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/64195
Refs: https://github.com/nodejs/undici/issues/5358
Reviewed-By: Matthew Aitken <maitken033380023@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Mon, 29 Jun 2026 09:01:30 GMT
   ✔  Approvals: 2
   ✔  - Matthew Aitken (@KhafraDev): https://github.com/nodejs/node/pull/64195#pullrequestreview-4594006348
   ✔  - James M Snell (@jasnell) (TSC): https://github.com/nodejs/node/pull/64195#pullrequestreview-4629919230
   ✔  Last GitHub CI successful
   ✘  No Jenkins CI runs detected
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https://github.com/nodejs/node/actions/runs/28718869468

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74551/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74553/

[nodejs-github-bot]

Landed in 4d27d80