HttpTransport looked for an event boundary with strpos($buffer, "\n\n") and
split event lines on "\n". Servers that terminate SSE lines with CRLF therefore
never produced a recognised event: the response accumulated in the buffer, no
message was ever dispatched, and connect() failed with "Initialization failed:
Request timed out".
This affects every MCP server built on the Python SDK. FastMCP's
streamable_http_app() returns sse_starlette's EventSourceResponse without a sep
argument, and its DEFAULT_SEPARATOR is "\r\n". The bug is invisible from within
this repository because the PHP server implementation emits LF, so client and
server agree in the test suite while disagreeing with most servers in the wild.
The SSE specification requires a parser to accept CRLF, LF or CR, so the
previous behaviour was non-compliant rather than merely unlucky.
Event extraction now accepts all three terminators, choosing whichever appears
first so a buffer split mid-sequence is handled correctly, and line splitting
uses the same set. A stream that ends without a trailing blank line now
dispatches its final event instead of discarding it.
Adds the first tests for src/Client/Transport/, covering LF, CRLF and CR
framing, an id field, a comment preamble, and a missing trailing blank line.
Without the fix four of the six fail with the timeout above.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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