[v1.x] fix(stdio): strip a leading UTF-8 byte order mark before parsing a message - #2796
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[v1.x] fix(stdio): strip a leading UTF-8 byte order mark before parsing a message#2796errmakov wants to merge 1 commit into
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…ssage When a peer prefixed a message with a UTF-8 BOM (as some Windows tools and shell redirections do), JSON.parse rejected the line: the transport reported a SyntaxError on onerror, the message was lost, and the pending request waited for its timeout. Strip a leading U+FEFF from each line before parsing, which RFC 8259 §8.1 allows. A U+FEFF inside the message is left alone. Backport of the same fix on main. Refs modelcontextprotocol#2775 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01P8hmy9JVNHqYDYEX5KBYye
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Backport of #2790 to
v1.x. Part of #2775 (the byte order mark case).On
v1.x, when a stdio peer prefixes a message with a UTF-8 BOM,ReadBuffer.readMessage()throws aSyntaxError. The transport reports it ononerror, the message is lost, and the pending request waits for its timeout. Against@modelcontextprotocol/sdk@1.30.0with a 2 s timeout, the call fails withMCP error -32001: Request timed out.Same change as on
main: strip a leading U+FEFF from each line before parsing (RFC 8259 §8.1), and leave a U+FEFF inside a message alone.Tests cover a BOM-prefixed message, a BOM split across chunks with a CRLF line ending, a U+FEFF inside a string, and a spawned server writing a BOM through
StdioClientTransport.npm run lint,npm run build,npm run typecheckand the stdio tests pass. In the fullnpm testrun, the only failure wasprocessCleanup.test.tstiming out under load; it passes on its own.Opened as a draft only because GitHub lets this account keep one non-draft PR here; the branch is complete and ready to merge after #2790.
AI disclosure: this PR was written with the help of Claude Code.