fix(streamable-http): prevent SSE reconnect loops with shadow channels#660

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its-mash wants to merge 9 commits intomodelcontextprotocol:mainfrom

mcpmux:fix/sse-channel-replacement-conflict

Commits on Feb 19, 2026

fix(streamable-http): return 409 Conflict when standalone SSE stream already active
its-mash
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fix(streamable-http): handle resume with completed request-wise channel
its-mash
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fix: allow SSE channel replacement instead of 409 Conflict
its-mash
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fix: skip cache replay when replacing active SSE stream
its-mash
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fix: use shadow channels to prevent SSE reconnect loops
its-mash
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test: comprehensive shadow channel tests (15 cases)
its-mash
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fix: use correct HTTP status codes for session errors per MCP spec
its-mash
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fix: address review feedback — remove dead Conflict variant, restore sync on resume, rename test
its-mash
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fix: use minimal buffer for shadow streams and cap at 32
its-mash
committed