A shell that cannot start fails Tty and pty/ctl exec with why, before either answers

A shell whose exec failed (a script's missing interpreter) was reported
started: Tty and pty/ctl exec succeeded, then the pane died. The child now
reports a failed chdir or exec through a close-on-exec pipe the parent
reads before acknowledging the shell; the host's spawn fails with the
reason (`shell not found`, ENOENT), which fails the waiting write. A Tty
whose first shell never ran leaves no pane; a terminal restarted by
pty/ctl exec keeps its pane.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index 26c9246a..35b44871 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -5023,6 +5023,7 @@ pub const Pardes = struct {
         if (id < MAX_PANES) if (p.panes[id]) |pane| {
             ctlfs.pty.shellGone(p, pane, true); // a respawn replaced whatever ran
             pane.shell_failed = false;
+            pane.had_shell = true;
             pane.fs.unmarked = !prompt_marks;
             // The tag's Tty word names the shell the host ran, and a click
             // on it (`Tty+fish`) opens another of the same.
@@ -5266,6 +5267,11 @@ pub const Pardes = struct {
         if (pane.command != null and !pane.command_done) {
             pane.command_pty = false;
             exec.commandDone(p, id, 127);
+        } else if (pane.command == null and !pane.had_shell) {
+            // A Tty whose shell never ran: no dead pane left behind; the
+            // write that asked for it has failed with why. A terminal whose
+            // shell was started again (pty/ctl exec) keeps its pane.
+            p.unplaced.set(id);
         }
     }