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ax ssh <task> with no command silently does nothing instead of opening an interactive shell #374
Description
`ax ssh ` (no trailing `-- command`) is documented as opening an interactive shell (README, CLI help text), but it doesn't work: it runs immediately and returns to the prompt with no output and no error.
Root cause: `runSSH` in `cmd/ax/main.go` defaults to running `/bin/sh` when no command is given, but `guest.Client.Exec` (`internal/guest/client.go`) never wires up stdin. `ExecOptions` only has `Stdout`/`Stderr`. The shell gets EOF on stdin immediately and exits, same as running `echo | sh` locally.
Repro: apply a task with `spec.debug: true`, wait for it to reach `Running`, run `ax ssh `. Nothing happens.
A real interactive shell needs stdin forwarding end to end: `ExecOptions.Stdin`, the `StartProcessRequest`/streaming RPCs in the guest protocol, and ideally PTY allocation so things like `vim` or job control work. One-off commands (`ax ssh -- ls`) work fine since they don't need stdin.
Activity
Update Agent Substrate import path (google#374)
feat(cli): forward stdin and Ctrl-C in ax ssh (#413)
anzal1 commentedon Oct 16, 2026
@mayawang thanks for the pointer in #413. I'd like to build PTY support for
ax sshand want your take before starting.The guest protocol in agent-substrate/env has no tty or resize today, so this is two PRs:
ttyoption onStartProcessRequest(with rows and cols) and aResizeProcessRPC. The guest allocates the pty and puts the merged output on stdout. Additive, so old clients keep working.ax ssh <task>on a terminal gets a pty, with-t/-Toverrides like ssh.Since Ctrl-C becomes a byte in raw mode, the double Ctrl-C escape would become ssh's
~..Is this approach OK, and are you fine with the proto change in env? Happy to keep it compatible with #492 if ssh becomes exec.
mayawang commentedon Oct 16, 2026
Thanks @anzal1, the two-step plan makes sense. Two things first: #492 renames
ax sshtoax execand addsax cp, so the AX half should build on that. And the guest protocol lives in agent-substrate/env, so it's worth opening an issue there with the tty and resize proposal before the PR.anzal1 commentedon Oct 28, 2026
@mayawang sorry for the silence since your Oct 16 reply. An update on your two points:
Env issue: opened agent-substrate/env#104 with the tty + resize proposal on Oct 17, and tomergee implemented it the next day in agent-substrate/env#107, which is in review now.
Building on #492: agreed. I'll do the ax side on ax exec rather than ax ssh, so I'm holding until the #492 rename and env#107 land. Then I'll send raw mode, the initial size, resize on SIGWINCH and the ~. escape.