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feat!: enable h2 by default#4823

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metcoder95 wants to merge 21 commits intonextfrom
enable_h2
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feat!: enable h2 by default#4823
metcoder95 wants to merge 21 commits intonextfrom
enable_h2

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@metcoder95 metcoder95 commented Feb 12, 2026 •
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This enables HTTP/2 support by default in Undici.

Rationale

Currently, users must explicitly opt-in to H2 support via allowH2: true. This change adjusts Undici's defaults to align with current web standards and improve out-of-the-box performance.

Changes

This PR changes the default value of the allowH2 option from false to true in the connection builder (lib/core/connect.js). When connecting to HTTPS servers, Undici will now use HTTP/2 if the server advertises it through ALPN negotiation, falling back to HTTP/1.1 if not supported.

Features

  • HTTP/2 is now enabled by default for connections to servers that support it via ALPN negotiation
  • Users can still explicitly disable H2 by setting allowH2: false in client options

Bug Fixes

N/A

Breaking Changes and Deprecations

Breaking Change: The default value of allowH2 changes from false to true.

Impact:

  • Applications relying on HTTP/1.1-only behavior by default will now use HTTP/2 when connecting to H2-capable servers
  • Users who need HTTP/1.1-only connections must now explicitly set allowH2: false in their client configuration
  • The protocol upgrade is transparent and should not affect most applications, but may change connection behavior and performance characteristics

Status

domenic and others added 21 commits January 31, 2026 09:25
@domenic
feat: expose statusText in request() ResponseData (#4784)
352c691
@mcollina
test: reduce retry-after invalid date timing flake (#4788)
5a5920d
@KhafraDev
extractBody fixes (#4791)
9948d6f
@mcollina
fix: MockAgent delayed response with AbortSignal (#4693) (#4772)
f1d50a2 
When a MockAgent had a delayed response and the request was aborted via
AbortSignal, the delayed response callback would still fire and attempt to
call handler methods after onError had been called. This violated state
invariants expected by handlers like DecoratorHandler (used by decompress
interceptor).

The fix:
- Tracks abort state in mockDispatch
- Clears pending setTimeout timer when abort is called
- Checks abort flag in handleReply before invoking handler callbacks
- Properly calls handler.onConnect to register abort callback

Fixes #4693
@vbfox
fix: onParserTimeout potentially accessing undefined (#4758)
e65fa39 
In cases where onParserTimeout is called with a weak reference that has
already been collected it was throwing an error like:

    Cannot destructure property 'socket' of 'parser.deref(...)' as it is
    undefined

- Fixes #4755
@github-actions
Bumped v7.20.0 (#4792)
6cc668d 
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
@dependabot
build(deps): bump actions/setup-node from 6.0.0 to 6.2.0 (#4796)
072c17a 
Bumps [actions/setup-node](https://github.com/actions/setup-node) from 6.0.0 to 6.2.0.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@2028fbc...6044e13)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: 6.2.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@mcollina
test: restore global dispatcher after fetch tests (#4790)
dae4d91
@piotr-cz
Add close method to WebSocketStream interface (#4802)
ff6bc5a
@KhafraDev @mcollina
fix: error stream instead of canceling (#4804)
fc8bb75 
* fix: error stream instead of canceling

Co-authored-by: Matteo Collina <hello@matteocollina.com>

* fixup

---------

Co-authored-by: Matteo Collina <hello@matteocollina.com>
@mcollina
Fix clientTtl cleanup race (#4807)
9cc025b
@metcoder95
feat(#4230): Implement pingInterval for dispatching PING frames (#4296)
283f2aa
@mcollina
fix: handle undefined __filename in bundled environments (#4812)
92e38fc
@tsctx
fix: set finalizer only for fetch responses (#4803)
47f9b96
@github-actions
Bumped v7.21.0 (#4813)
393c0da 
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
@styfle
docs: fix syntax highlighting in WebSocket.md (#4814)
b3326b5 
Updated code block syntax highlighting from 'mjs' to 'js' so that syntax highlighting works.
@jackhax
fix: use OR operator in includesCredentials per WHATWG URL Standard (#…
a821c56 
…4816)
@SuperOleg39
feat(dispatcher/env-http-proxy-agent): strip leading dot and asterisk (…
4658cdf 
…#4676)
@mcollina
fix: route websocket upgrades through new handler API (#4787)
2453caf
@dependabot
build(deps-dev): bump esbuild from 0.25.12 to 0.27.3 (#4821)
0ce57ba 
Bumps [esbuild](https://github.com/evanw/esbuild) from 0.25.12 to 0.27.3.
- [Release notes](https://github.com/evanw/esbuild/releases)
- [Changelog](https://github.com/evanw/esbuild/blob/main/CHANGELOG.md)
- [Commits](evanw/esbuild@v0.25.12...v0.27.3)

---
updated-dependencies:
- dependency-name: esbuild
  dependency-version: 0.27.3
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
@metcoder95
feat!: enable h2 by default
09862a2
@metcoder95 metcoder95 requested review from mcollina and ronag February 12, 2026 10:00
ronag
ronag previously approved these changes Feb 12, 2026
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codecov-commenter commented Feb 12, 2026

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.16%. Comparing base (2453caf) to head (09862a2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files 
@@            Coverage Diff             @@
##             main    #4823      +/-   ##
==========================================
- Coverage   93.17%   93.16%   -0.02%     
==========================================
  Files         109      109              
  Lines       34187    34187              
==========================================
- Hits        31855    31849       -6     
- Misses       2332     2338       +6

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

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  • ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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@mcollina mcollina changed the base branch from main to next February 12, 2026 22:11
@mcollina mcollina dismissed ronag’s stale review February 12, 2026 22:11

The base branch was changed.

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mcollina commented Feb 12, 2026

ahum, didn't work as expected.

@metcoder95
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metcoder95 commented Feb 12, 2026

I think it needs a rebase, let me give it a shot

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metcoder95 commented Feb 13, 2026

Closed in favor of #4828

@metcoder95 metcoder95 closed this Feb 13, 2026
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