fix(jetsocat): detect broken pipe and stop MCP proxy gracefully #1544
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When the MCP server connection breaks (process died, pipe closed), the proxy now detects this and stops forwarding requests instead of continuing to fail on each subsequent request.
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Pull Request Overview
This PR adds robust handling for broken pipe scenarios in the MCP proxy, ensuring graceful shutdown when the underlying MCP server connection fails. The proxy now distinguishes between fatal connection errors (broken pipe, connection reset, unexpected EOF) and recoverable errors, returning a FatalError for the former case that includes an optional error response to send to the client before terminating.
Key changes:
- Modified
forward_requestto returnResult<Option<Message>, FatalError>instead ofOption<Message> - Added
is_fatal_io_errorhelper to classify I/O errors as fatal or recoverable - Updated error handling in
jetsocatto detect fatal errors, send error responses, and exit gracefully
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| crates/mcp-proxy/src/lib.rs | Core logic changes: new FatalError type, modified forward_request signature to return Result, fatal error classification via is_fatal_io_error, and updated error handling for Process and NamedPipe transports |
| jetsocat/src/mcp.rs | Updated to handle new Result return type from forward_request, sends error response on fatal errors and exits gracefully |
| testsuite/tests/mcp_proxy.rs | Updated test assertions to unwrap the new outer Result layer from forward_request |
| testsuite/tests/cli/jetsocat.rs | Added integration test mcp_proxy_terminated_on_broken_pipe to verify graceful shutdown behavior when MCP server connection breaks |
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awakecoding
approved these changes
Oct 29, 2025
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When the MCP server connection breaks (process died, pipe closed), the proxy now detects this and stops forwarding requests instead of continuing to fail on each subsequent request.