Kill stops a command's shell before its jobs, so the line never runs on to its next command in between

signalTty signalled the running job's group first, then scanned all of
/proc for the session's & jobs, then the shell. A job dead of the signal
lets a job-control shell run the line's next command, and once pids wrap
below the host's older processes the scan takes long enough for it to:
"sleep 0.4; touch killed" killed at 150ms touched the file. The host_io
test caught it every run after the pids wrapped (pid_max 4194304, new pids
near 17000, 229 older processes above them to scan). The shell's group now
goes first, then the session's groups, then the foreground one.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/host_io.zig b/src/host_io.zig
index 9e3fbf79..eb6d1d5d 100644
--- a/src/host_io.zig
+++ b/src/host_io.zig
@@ -1917,6 +1917,9 @@ fn reapShell(pid: libc.pid_t, grace_ms: u32) void {
 /// the rest of the line would run on after the job it was on. A stop (TERM
 /// or KILL) of a command reaches its `&` jobs too, each in a group of its
 /// own in the shell's session: Kill leaves nothing the line started.
+/// The shell goes first: a job that died before it would let it run the
+/// line's next command in the gap, and the gap is a scan of all of /proc
+/// (signalSession), long once pids have wrapped below the old processes'.
 pub fn signalTty(shell_pid: libc.pid_t, master_fd: c_int, which: pardes.PtySignal, command: bool) void {
     const sig = switch (which) {
         .int => libc.SIG.INT,
@@ -1926,9 +1929,9 @@ pub fn signalTty(shell_pid: libc.pid_t, master_fd: c_int, which: pardes.PtySigna
         .kill => libc.SIG.KILL,
     };
     const fg = tcgetpgrp(master_fd);
+    if (command and shell_pid > 0 and fg != shell_pid) _ = libc.kill(-shell_pid, sig);
     if (command and shell_pid > 0 and (which == .term or which == .kill)) signalSession(shell_pid, sig);
     if (fg > 0) _ = libc.kill(-fg, sig);
-    if (command and shell_pid > 0 and fg != shell_pid) _ = libc.kill(-shell_pid, sig);
     if (fg <= 0 and !command and shell_pid > 0) _ = libc.kill(shell_pid, sig);
 }