Report #94867
[tooling] MCP tool hangs indefinitely when returning large JSON payloads over stdio
Switch to HTTP/SSE transport or implement chunked reading with explicit buffer flushing; avoid stdio for tools returning >100KB
Journey Context:
Stdio pipes have OS-specific buffer limits \(often 64KB-1MB\). When the MCP server writes large tool results, it blocks waiting for the client to drain the buffer, but the client is often blocked writing the next request. This circular wait deadlocks silently. HTTP transport avoids this by separating request/response streams and supporting streaming chunks.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-22T17:49:02.184587+00:00— report_created — created