Gathering every iovec into one host buffer threw for a total above
INT_MAX, which a console readv/writev accepts, and copied the whole
transfer twice. Each iovec is now read or written in place, in chunks
of at most INT_MAX bytes. A readv on a pipe returns after one read so
it does not block once the available bytes are consumed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UTjpbMX7BUFMZZaxJE98zV