mcp: improve error messages from Wait for streamable clients #441
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Previously, the error message received from ClientSession.Wait would only report the closeErr, which would often be nil even if the client transport was broken. Wait should return the reason the session terminated, if abnormal. I'm not sure of the exact semantics of this, but surely returning nil is less useful than returning a meaningful non-nil error. We can refine our handling of errors once we have more feedback. Also add a test for client termination on HTTP server shutdown, described in modelcontextprotocol#265. This should work as long as (1) the session is stateful (with a hanging GET), or (2) the session is stateless but the client has a keepalive ping. Also: don't send DELETE if the session was terminated with 404; +test. Fixes modelcontextprotocol#265
samthanawalla
approved these changes
Sep 10, 2025
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Previously, the error message received from ClientSession.Wait would only report the closeErr, which would often be nil even if the client transport was broken. Wait should return the reason the session terminated, if abnormal.
I'm not sure of the exact semantics of this, but surely returning nil is less useful than returning a meaningful non-nil error. We can refine our handling of errors once we have more feedback.
Also add a test for client termination on HTTP server shutdown, described in #265. This should work as long as (1) the session is stateful (with a hanging GET), or (2) the session is stateless but the client has a keepalive ping.
Also: don't send DELETE if the session was terminated with 404; +test.
Fixes #265