From b72a32bbc6f19223da7993a38db6f7c28ff6aaf5 Mon Sep 17 00:00:00 2001
From: Harry Bayliss <harry@hjb.dev>
Date: Wed, 27 May 2026 13:19:35 +0100
Subject: [PATCH] Fix PTY workdir and process group teardown

---
 internal/app/child.go    |  2 +-
 internal/pty/pty.go      |  9 ++++-
 internal/pty/pty_test.go | 84 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+), 2 deletions(-)
 create mode 100644 internal/pty/pty_test.go

diff --git a/internal/app/child.go b/internal/app/child.go
index 91f96f4..300c965 100644
--- a/internal/app/child.go
+++ b/internal/app/child.go
@@ -228,7 +228,7 @@ func (c *Child) startPTY(cols, rows uint16) (uint64, error) {
 	}
 	starting := StatusStarting
 	c.status.Store(&starting)
-	p, err := pkgpty.Start(c.Argv, c.Env, cols, rows)
+	p, err := pkgpty.Start(c.Argv, c.Env, c.WorkDir, cols, rows)
 	if err != nil {
 		em.Close()
 		errored := StatusErrored
diff --git a/internal/pty/pty.go b/internal/pty/pty.go
index 4f8beca..925a6b0 100644
--- a/internal/pty/pty.go
+++ b/internal/pty/pty.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"syscall"
 
 	cpty "github.com/creack/pty"
 )
@@ -19,11 +20,13 @@ type PTY struct {
 // Start spawns argv with stdin/stdout/stderr attached to a new PTY sized
 // (cols, rows). The returned PTY exposes the master fd for the parent to
 // read from and write to.
-func Start(argv []string, env []string, cols, rows uint16) (*PTY, error) {
+func Start(argv []string, env []string, workDir string, cols, rows uint16) (*PTY, error) {
 	if len(argv) == 0 {
 		return nil, fmt.Errorf("pty: empty argv")
 	}
 	cmd := exec.Command(argv[0], argv[1:]...)
+	cmd.Dir = workDir
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true, Setctty: true}
 	if env != nil {
 		cmd.Env = ensureTerm(env)
 	} else {
@@ -88,6 +91,10 @@ func (p *PTY) Close() error {
 		p.master = nil
 	}
 	if p.cmd != nil && p.cmd.Process != nil {
+		pid := p.cmd.Process.Pid
+		if pid > 0 {
+			_ = syscall.Kill(-pid, syscall.SIGKILL)
+		}
 		_ = p.cmd.Process.Kill()
 	}
 	return firstErr
diff --git a/internal/pty/pty_test.go b/internal/pty/pty_test.go
new file mode 100644
index 0000000..1aa9d94
--- /dev/null
+++ b/internal/pty/pty_test.go
@@ -0,0 +1,84 @@
+package pty
+
+import (
+	"bytes"
+	"errors"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestStartUsesWorkDir(t *testing.T) {
+	dir := t.TempDir()
+	p, err := Start([]string{"sh", "-c", "pwd"}, nil, dir, 80, 24)
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+	defer p.Close()
+
+	var out bytes.Buffer
+	buf := make([]byte, 256)
+	deadline := time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		n, err := p.Read(buf)
+		if n > 0 {
+			out.Write(buf[:n])
+			if strings.Contains(out.String(), dir) {
+				break
+			}
+		}
+		if err != nil {
+			break
+		}
+	}
+	_ = p.Wait()
+
+	if got := strings.TrimSpace(out.String()); got != dir {
+		t.Fatalf("pwd output = %q, want %q", got, dir)
+	}
+}
+
+func TestCloseKillsProcessGroup(t *testing.T) {
+	dir := t.TempDir()
+	pidFile := filepath.Join(dir, "sleep.pid")
+	env := append(os.Environ(), "PIDFILE="+pidFile)
+	p, err := Start([]string{"sh", "-c", "sleep 30 & echo $! > \"$PIDFILE\"; wait"}, env, "", 80, 24)
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+	deadline := time.Now().Add(5 * time.Second)
+	var childPID int
+	for time.Now().Before(deadline) {
+		b, err := os.ReadFile(pidFile)
+		if err == nil {
+			childPID, _ = strconv.Atoi(strings.TrimSpace(string(b)))
+			if childPID > 0 {
+				break
+			}
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	if childPID <= 0 {
+		_ = p.Close()
+		t.Fatalf("background child pid was not written")
+	}
+
+	if err := p.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+	_ = p.Wait()
+
+	deadline = time.Now().Add(5 * time.Second)
+	for time.Now().Before(deadline) {
+		err := syscall.Kill(childPID, 0)
+		if errors.Is(err, syscall.ESRCH) {
+			return
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatalf("background child pid %d still exists after PTY.Close", childPID)
+}