Manage output streams carefully

Always consider the destination and lifecycle of output streams to prevent protocol interference, data loss, and unexpected behavior. Choose stdout for application output and stderr for debugging/logging. Avoid accidentally closing streams and be mindful of output pollution in protocol-sensitive contexts.

Key practices:

• Use stderr for debug/log output to avoid interfering with application protocols
• When piping streams, use { end: false } option to prevent closing the target stream
• In protocol-sensitive contexts (like JSON-RPC), redirect console output to stderr to prevent stdout pollution
• Prefer process.stderr.write over console.warn in tests to avoid mock interference
• Use console.error.bind(console) instead of custom implementations to preserve formatting

Example:

// Good: Prevent stdout closure when piping
fileStream.pipe(process.stdout, { end: false })

// Good: Redirect console in protocol contexts  
if (process.argv.includes('mcp')) {
  console.log = console.error.bind(console)
}

// Good: Use stderr for debug output
console.warn(`${namespace} ${format}`, ...rest)