fix: native WebSocket over H2 server after undici import#4990
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fix: native WebSocket over H2 server after undici import#4990
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Importing undici v8 overwrites the legacy global dispatcher
(Symbol.for('undici.globalDispatcher.1')) used by Node.js's bundled
undici. The new Agent defaults to allowH2: true, causing ALPN to
negotiate h2. Undici v8's fetch has a fallback
(dispatchWithProtocolPreference) that retries with HTTP/1.1 when
Extended CONNECT is unavailable, but the bundled undici does not.
Fix Dispatcher1Wrapper.dispatch() to force allowH2: false for upgrade
requests, since legacy consumers cannot handle the H2 WebSocket
fallback.
Fixes: #4989
Signed-off-by: Matteo Collina <hello@matteocollina.com>
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@cristianmadularu please test this |
Is it released? If not, how could I reference it from my packages.json? |
KhafraDev
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Apr 7, 2026
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Test is failing and it'll only work on node version that bundle undici v7.
Legacy (v1) consumers (like Node.js's bundled undici on Node 22) do not support HTTP/2. Force allowH2: false in Dispatcher1Wrapper so that the v1 global dispatcher always uses HTTP/1.1. Also add NODE_TLS_REJECT_UNAUTHORIZED for the regression test since native WebSocket uses the bundled dispatcher without rejectUnauthorized override. Signed-off-by: Matteo Collina <hello@matteocollina.com>
![github-advanced-security[bot]](https://avatars.githubusercontent.com/in/57789?s=60&v=4){kind=small}
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #4990 +/- ##
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- Coverage 92.94% 92.87% -0.07%
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Files 110 110
Lines 35773 35794 +21
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- Hits 33249 33244 -5
- Misses 2524 2550 +26 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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@KhafraDev ptal |
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Importing undici v8 overwrites the legacy global dispatcher
(Symbol.for('undici.globalDispatcher.1')) used by Node.js's bundled
undici. The new Agent defaults to allowH2: true, causing ALPN to
negotiate h2. Undici v8's fetch has a fallback
(dispatchWithProtocolPreference) that retries with HTTP/1.1 when
Extended CONNECT is unavailable, but the bundled undici does not.
Fix Dispatcher1Wrapper.dispatch() to force allowH2: false for legacy consumers that cannot handle the H2 WebSocket fallback.
Fixes: #4989