chenhg5/cc-connect · error

iflowSession: start pty: %w

Error message

iflowSession: start pty: %w

What it means

Wraps a failed pty.Start in iflowSession.Send: the interactive iflow turn must run under a pseudo-terminal, and the OS refused to allocate one or exec the process. The turnActive flag is reset so the session is not stuck; causes include missing /dev/ptmx, fd limits, or a dead binary.

Source

Thrown at agent/iflow/session.go:201

	} else if s.sentOnce.Load() {
		args = append(args, "-c")
	}

	args = append(args, "-i", prompt)
	slog.Debug("iflowSession: launching interactive turn", "resume", sid != "", "args", core.RedactArgs(args))

	cmd := exec.CommandContext(turnCtx, s.cmd, args...)
	cmd.Dir = s.workDir
	env := os.Environ()
	if len(s.extraEnv) > 0 {
		env = core.MergeEnv(env, s.extraEnv)
	}
	cmd.Env = env

	ptmx, err := pty.Start(cmd)
	if err != nil {
		s.turnActive.Store(false)
		return fmt.Errorf("iflowSession: start pty: %w", err)
	}

	s.sentOnce.Store(true)
	s.wg.Add(1)
	go s.readLoop(turn, cmd, ptmx)
	return nil
}

func (s *iflowSession) readLoop(turn *iflowTurn, cmd *exec.Cmd, ptmx *os.File) {
	defer s.wg.Done()
	defer s.turnActive.Store(false)
	defer turn.cancel()
	defer ptmx.Close()

	var termBuf bytes.Buffer
	drainDone := make(chan struct{})
	go func() {
		_, _ = io.Copy(&termBuf, ptmx)

View on GitHub (pinned to 4000b2338a)

Solutions

1. Verify the iflow CLI is still present and executable: `which iflow && iflow --version`
2. Check file-descriptor/process limits (ulimit -n) if PTY allocation fails
3. Ensure the container/runtime exposes /dev/pts (run with a tty-capable setup)
4. Recreate the agent/session so exec.LookPath re-resolves the binary

Example fix

// before
cmd := exec.Command("iflow", args...) // stale binary path
// after
bin, err := exec.LookPath("iflow")
if err != nil { return fmt.Errorf("iflow CLI missing: %w", err) }
cmd := exec.Command(bin, args...)

bin, err := exec.LookPath("iflow")
if err != nil || unix.Access(bin, unix.X_OK) != nil {
    return fmt.Errorf("iflow binary missing or not executable")
}

if err := session.Send(ctx, msg, nil); err != nil {
    if strings.Contains(err.Error(), "start pty") {
        log.Printf("pty start failed, check fd limits and /dev/pts: %v", err)
        return recreateSessionAndRetry()
    }
}

When it happens

Trigger: Calling Send() when pty.Start fails — the iflow binary vanished from PATH after New(), the resolved command path is not executable, argument list is invalid, or PTY allocation failed (resource limits, non-tty-capable environment).

Common situations: CLI uninstalled/upgraded between agent construction and session use; sandbox/container without /dev/ptmx; too many open files; binary lacks execute permission after a partial update.

Related errors

• antigravitySession: stdout pipe: %w
• antigravitySession: start: %w
• codex app-server stdin pipe: %w
• codex app-server stdout pipe: %w
• codex app-server stderr pipe: %w

AI-assisted analysis of chenhg5/cc-connect@4000b2338a (2026-09-06). Data as JSON: /api/errors/bb3550be0f480154. Report an issue: GitHub.