fix(client): ignore unknown SSE fields instead of erroring the stream#1051
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imankhadiv wants to merge 2 commits into
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fix(client): ignore unknown SSE fields instead of erroring the stream#1051imankhadiv wants to merge 2 commits into
imankhadiv wants to merge 2 commits into
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The SSE line parser rejected any line it did not recognize (e.g. the standard `retry:` field), throwing McpTransportException and tearing down an otherwise valid stream. Per the SSE spec, unknown fields must be ignored. Log such lines at debug and continue. Refs modelcontextprotocol#1047
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Summary
The client SSE line parser in
ResponseSubscriberserrored the whole stream on any line it didn't recognize — e.g. the standardretry:field — throwing:Per the SSE spec, a client must ignore fields it does not recognize rather than treat them as an invalid response. This change makes the parser log unrecognized lines at
debugand continue.This addresses the "ignore unknown fields" ask in #1047. As discussed there, resumability /
retry:reconnection timing is intentionally not implemented (it is being removed in the 2026-07-28 spec).Changes
ResponseSubscribers.SseLineSubscriber: the fall-throughelsenow ignores unrecognized SSE lines instead of emittingMcpTransportException. Removed the now-unused import.Testing
ResponseSubscribersTests(2 tests): aretry:line no longer errors the stream and the event still parses; an arbitrary unknown field is ignored../mvnw test -pl mcp-core→ green.Notes
sse-retryscenario stays listed inconformance-tests/conformance-baseline.yml: this fix removes the crash, but the scenario's retry-timing check is a resumability behavior that is intentionally out of scope.Refs #1047