fix: Ensure stdio server exits when stdin reaches EOF (fixes #2231)#2234
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goingforstudying-ctrl wants to merge 4 commits intomodelcontextprotocol:mainfrom
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fix: Ensure stdio server exits when stdin reaches EOF (fixes #2231)#2234goingforstudying-ctrl wants to merge 4 commits intomodelcontextprotocol:mainfrom
goingforstudying-ctrl wants to merge 4 commits intomodelcontextprotocol:mainfrom
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added 4 commits
March 6, 2026 14:37
When the parent process dies or stdin is closed, the stdio server now properly detects EOF and shuts down gracefully instead of becoming an orphan process. Changes: - Explicitly close read_stream_writer on EOF to signal shutdown - Add test coverage for EOF handling and parent death simulation Fixes modelcontextprotocol#2231
Pass mock stdin (empty BytesIO) and stdout to stdio_server() to avoid UnsupportedOperation when reading real stdin in CI.
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Problem
When an MCP server using
transport="stdio"has its parent process die (e.g. client crashes, is killed, or exits), the server process becomes an orphan and continues running instead of shutting down gracefully.Root Cause
The stdin reader loop ends when EOF is reached, but there was no explicit signal to the rest of the server that shutdown should occur.
Solution
read_stream_writeron EOF to signal shutdownChanges
src/mcp/server/stdio.py: Close read stream on EOFtests/test_stdio_eof.py: New test file with EOF testsTesting
test_stdio_server_exits_on_eof()- verifies server exits on stdin EOFtest_stdio_server_parent_death_simulation()- simulates parent process deathFixes #2231