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fix(client): preserve pre-set transport handlers across the version-negotiation probe window (#2455)

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Felix Weinberger 2026-07-07 15:09:41 +01:00 • committed by GitHub
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'@modelcontextprotocol/client': patch
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Version negotiation no longer discards transport handlers the caller set before `connect()`. The probe window now saves any pre-set `onmessage`/`onerror`/`onclose`, forwards error and close events to them while the probe is in flight, and restores them when the window closes — so `Protocol.connect()` chains them exactly as it does on a plain connect. Previously, connecting with `versionNegotiation` silently cleared pre-set handlers (e.g. an `onerror` used to detect session-expiry auth failures), leaving them permanently detached for the life of the connection.