fix: disable CRLF translation in stdio_server on Windows#2470
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Christian-Sidak wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix: disable CRLF translation in stdio_server on Windows#2470Christian-Sidak wants to merge 1 commit intomodelcontextprotocol:mainfrom
Christian-Sidak wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Add newline="" to both TextIOWrapper calls in stdio_server() to prevent platform-dependent LF→CRLF translation on Windows, ensuring LF-only line endings in the NDJSON wire format on all platforms. Fixes modelcontextprotocol#2433
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Closing -- duplicate of #2440 which already fixes this. |
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Summary
On Windows,
TextIOWrapperwith the defaultnewline=Nonetranslates\n→\r\non write. This means every JSON-RPC message emitted bystdio_server()gets\r\nline endings, violating the NDJSON wire format.The fix is to pass
newline=""to bothTextIOWrappercalls instdio_server(), which disables the platform-dependent line-ending translation while keeping the stream in text mode.Changes
src/mcp/server/stdio.py: addnewline=""to bothTextIOWrapperconstructors (stdin and stdout)tests/server/test_stdio.py: addtest_stdio_server_uses_lf_newlinesto assert the output contains only LF, not CRLFFixes #2433