[Bug] MCP client hangs indefinitely when sending large tool arguments
Status Closed — not planned
Reported on v2.1.119
Maintainer reply None cached
Activity 3 comments · opened Apr 26, 2026 · closed May 28, 2026
Bug Description
The Claude Code MCP client hangs indefinitely when sending large tool arguments (~27KB) to an MCP server. Small payloads (e.g. 11 bytes) work instantly. Large responses from the server also work fine — the issue is specifically in outbound request serialization/dispatch. Reproducible with a local MCP server using streamable HTTP transport and stateless_http=True. The HTTP request never reaches the server (confirmed via server logs). Waited 2+ minutes with no timeout or error.
Environment Info
- Platform: darwin
- Terminal: Apple_Terminal
- Version: 2.1.119
- Feedback ID: e3caa228-b389-4a44-8364-6b4120c46dad
Note: I didn't include the errors because they were unrelated to the actual issue I'm seeing.
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