A launch with inherited open stdin hangs silently with zero output

[jasoncarreira]

Summary

If the process that launches prime-agent leaves stdin open as a pipe that never reaches EOF, the launch hangs
and writes zero bytes to stdout, stderr and the log. There is no message, so it is indistinguishable from a
crash or a hung daemon. Redirecting < /dev/null fixes it completely.

Environment. prime-agent 0.7.2, daemon protocol 7 (protocol-7-schema-16-1bcb9e7f1a49), build 83a0f9f-dirty, Node 24.11.1, macOS 15 (darwin 25.5.0).

Reproduction

# hangs: stdin is an open pipe with no EOF
sleep 300 | prime-agent -p "Reply with exactly: PONG"
#   -> killed at timeout, exit 124, 0 bytes of output

# works
prime-agent -p "Reply with exactly: PONG" < /dev/null
#   -> exit 0, prints: PONG   (5 bytes)

Both were run back to back on the same machine and daemon.

Expected

Either do not block on stdin when a prompt was supplied with -p, or emit something after a short wait — even
waiting for piped input on stdin would be enough to make this self-diagnosing.

Why it matters to us

Supervisors, CI steps and process managers routinely hand a child an inherited pipe. Because the symptom is
total silence, it is easy to misattribute: we spent an afternoon blaming flags and then daemon health before
finding that closing stdin fixed it. It also masks unrelated failures that produce the same silence.