Subprocess Output Capture And Streaming

Code Runner MCP Server

Unique: Implements dual-stream capture pattern that separates stdout and stderr into distinct buffers, allowing MCP clients to distinguish between normal output and error messages — critical for Claude to understand whether code execution succeeded and what went wrong.

vs others: More reliable than simple shell redirection because it captures streams at the Node.js API level, preventing output loss from buffering issues and providing structured access to exit codes without shell parsing.