fix(server): duplicate stdio fds to prevent closing real stdio - #2866
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superShen0916 wants to merge 1 commit into
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fix(server): duplicate stdio fds to prevent closing real stdio#2866superShen0916 wants to merge 1 commit into
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When using transport="stdio", the async wrappers around sys.stdin/sys.stdout would close the underlying file descriptors on server exit, causing subsequent operations like print() to fail with ValueError. Use os.dup() to duplicate the file descriptors before wrapping, so closing the async wrappers does not affect the original stdio streams. Fall back to the original behavior when the stream lacks a real fd (e.g. BytesIO in tests). Fixes modelcontextprotocol#1933 Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Thanks for the PR. Tracking this in #2040 instead. I'm closing this out as part of a backlog cleanup around the v2 release. Feel free to reopen if this is still relevant. |
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Summary
Fixes #1933. When using transport="stdio", the async wrappers around sys.stdin/sys.stdout would close the underlying file descriptors on server exit, causing subsequent operations like print() to fail with ValueError: I/O operation on closed file.
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