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fix: stop MCP dispatch after response transport failures - #63
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alexshapalov merged 1 commit intoSep 22, 2026
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The serving loop ignored buffered response write failures and continued dispatching diagnostic tools after losing its output transport. Propagate flush errors immediately, including the final response at EOF. Regression coverage exercises buffered and large responses, short writes, dispatch counts, and EOF error precedence. The protocol and JSON schema are unchanged. Closes pgrundev#60
This was referenced Sep 22, 2026
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What and why
Closes #60.
Server.Serveignored buffered response write errors, so a broken output pipe could leave it dispatching further diagnostic tools and ultimately returning success at input EOF. Return the flush error immediately instead. The response format and normal serving behavior are unchanged.The regression uses the real read/dispatch/write loop and proves that only the first of two tool calls runs after output failure. It covers small and larger-than-buffer responses, short writes, and a final request without a trailing newline.
Verification
Verified commit:
c1325b1de0b0f90f72426788ac927f8c5a450581.a1e6561e366455756c45a16a46647f882b3b6a1c: the new regression tests fail because the error is ignored and the second handler is called.go test -race ./internal/mcp -run 'TestServe_' -count=20: passed.bash scripts/gate.sh: passed on the committed HEAD, including build, vet, pinned golangci-lint, unit tests and all six release target builds.go test -race ./...: passed.gofmt -lon changed Go files andgit diff --check: clean.Risk and rollback
The change is limited to an already-failed output transport. Callers now receive the original write error rather than false success. Successful writes and notification handling are unchanged. Reverting this commit restores the prior behavior; no migrations or dependency changes are involved.
Checklist
scripts/gate.shpasses on the committed HEAD.model.Context, JSON, or the store.