fix(pty): don't stop relay on bare POLLHUP/POLLERR without POLLIN#54
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handle_pty_poll_events previously triggered proxy_master_to_client on any combination of POLLIN|POLLHUP|POLLERR|POLLNVAL. When POLLHUP or POLLERR fired without POLLIN (e.g. transiently during Node.js TTY reinitialisation at Claude Code startup), read() returned EIO, which proxy_master_to_client mapped to Closed, tearing down the relay while the child was still alive. For interactive TUIs the startup-timeout safety net is disabled, so nothing recovered the relay — causing an indefinite hang. Fix: only relay data (and stop on Closed/EOF) when POLLIN is set. Bare POLLHUP/POLLERR/POLLNVAL without POLLIN are now ignored; the waitpid path in the caller detects child exit instead.
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Problem
handle_pty_poll_eventstriggeredproxy_master_to_clienton any ofPOLLIN|POLLHUP|POLLERR|POLLNVAL. WhenPOLLHUPorPOLLERRfired withoutPOLLIN— which happens transiently during interactive TUI startup (e.g. Node.js reinitialising its TTY at Claude Code launch) —read()returnedEIO.proxy_master_to_client_oncemaps any read error toMasterProxyOutcome::Closed, causing the relay loop to stop while the child process was still alive. The startup-timeout safety net is disabled for interactive TUIs, so nothing recovered the relay → indefinite hang.Reported in: DataDog/shadowfax#421
Fix
Only relay data (and stop on
Closed/EOF) whenPOLLINis set. BarePOLLHUP/POLLERR/POLLNVALwithoutPOLLINare now ignored inhandle_pty_poll_events; thewaitpidpath in the caller detects child exit instead of relying on PTY master HUP.