fix: handle EPIPE errors in StdioServerTransport to prevent process crash#1568
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stakeswky wants to merge 2 commits intomodelcontextprotocol:mainfrom
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fix: handle EPIPE errors in StdioServerTransport to prevent process crash#1568stakeswky wants to merge 2 commits intomodelcontextprotocol:mainfrom
stakeswky wants to merge 2 commits intomodelcontextprotocol:mainfrom
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added 2 commits
February 22, 2026 16:12
Per MCP spec, calling a nonexistent tool should return a JSON-RPC Error (code -32602), not a JSON-RPC Result with isError: true. Previously, only UrlElicitationRequired errors were re-thrown; all other ProtocolErrors (including tool/disabled checks) were swallowed and wrapped in a CallToolResult. Now all ProtocolErrors propagate as JSON-RPC errors, which is the correct behavior per the specification. Fixes modelcontextprotocol#1510
Add error handling for stdout write failures to prevent uncaught EPIPE exceptions when clients disconnect unexpectedly. Changes: - Add stdout error listener in start() to catch EPIPE and other errors - Trigger graceful close when stdout errors occur - Handle write errors in send() by rejecting the promise - Clean up stdout error listener in close() This prevents the Node.js process from crashing when a client disconnects while the server is writing to stdout. Fixes modelcontextprotocol#1564
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Summary
Fix uncaught EPIPE exceptions in
StdioServerTransportthat crash the Node.js process when clients disconnect unexpectedly.Problem
When a client disconnects while the server is writing to stdout, the
stdout.write()call throws an EPIPE error. Since there's no error handler, this becomes an uncaught exception that crashes the entire Node.js process.Root Cause
send()method callsthis._stdout.write()without any error handlingstart()method doesn't register an error listener on_stdoutFix
start(): Catches EPIPE and other stdout errors, triggers graceful closesend(): Wrap write operations with error handling, reject the promise on failureclose(): Remove stdout error listener to prevent leaksBehavior
onerrorcallback with the errorclose()to clean up resourcessend()promises instead of crashingThis allows servers to handle client disconnections gracefully without process crashes.
Fixes #1564