Changed something

main.go

@@ -460,8 +460,9 @@ func run(name string, args []string) int {
 	}()
 
 	// Put stdin in raw mode if it is a terminal.
+	var oldState *term.State
 	if term.IsTerminal(int(os.Stdin.Fd())) {
-		oldState, err := term.MakeRaw(int(os.Stdin.Fd()))
+		oldState, err = term.MakeRaw(int(os.Stdin.Fd()))
 		if err != nil {
 			log.Printf("make raw: %v", err)
 			return 1
@@ -469,19 +470,111 @@ func run(name string, args []string) int {
 		defer term.Restore(int(os.Stdin.Fd()), oldState)
 	}
 
-	go io.Copy(ptmx, os.Stdin)
+	childPid := c.Process.Pid
+	termState := oldState // updated on each MakeRaw; only touched by suspend goroutine
+
+	var suspendMu sync.Mutex // ensures only one suspend/resume cycle runs at a time
+
+	// Copy stdin → PTY, intercepting Ctrl+Z (0x1A) for job control.
+	go func() {
+		buf := make([]byte, 4096)
+		for {
+			n, err := os.Stdin.Read(buf)
+			if n > 0 {
+				i := 0
+				for j := 0; j < n; j++ {
+					if buf[j] == 0x1A { // Ctrl+Z
+						if j > i {
+							ptmx.Write(buf[i:j])
+						}
+						// Run the full suspend/resume cycle in one goroutine so
+						// there is no cross-goroutine state to synchronize.
+						go func() {
+							if !suspendMu.TryLock() {
+								return // already suspending
+							}
+							defer suspendMu.Unlock()
+
+							// Stop the child immediately without forwarding 0x1A.
+							// Forwarding 0x1A causes copilot to write partial teardown
+							// sequences that glitch the display before we can stop it.
+							// We send to both the direct PID and the process group so
+							// that subprocesses are also stopped regardless of whether
+							// pty.Start created a new process group.
+							// SIGSTOP is synchronous — the child is stopped before
+							// Kill() returns, so no sleep is needed.
+							syscall.Kill(childPid, syscall.SIGSTOP)
+							syscall.Kill(-childPid, syscall.SIGSTOP)
+
+							// Exit alternate screen and show cursor in case copilot had
+							// them active, so the shell prompt appears on a clean screen.
+							os.Stdout.Write([]byte("\x1b[?1049l\x1b[?25h\r\n"))
+							// Hand the terminal back to the shell.
+							if termState != nil {
+								term.Restore(int(os.Stdin.Fd()), termState)
+							}
+							// Stop ourselves; the shell takes over.
+							syscall.Kill(os.Getpid(), syscall.SIGSTOP)
+
+							// ── Execution resumes here after "fg" ──────────
+							// Re-apply raw mode.
+							if termState != nil {
+								if s, err := term.MakeRaw(int(os.Stdin.Fd())); err == nil {
+									termState = s
+								}
+							}
+							// Continue the child (direct PID + process group).
+							syscall.Kill(childPid, syscall.SIGCONT)
+							syscall.Kill(-childPid, syscall.SIGCONT)
+							// Sync terminal size and ask copilot to redraw its UI.
+							pty.InheritSize(os.Stdin, ptmx)
+							syscall.Kill(childPid, syscall.SIGWINCH)
+						}()
+						i = j + 1
+					}
+				}
+				if i < n {
+					ptmx.Write(buf[i:n])
+				}
+			}
+			if err != nil {
+				return
+			}
+		}
+	}()
+
+	// exitCodeCh receives the child's exit code when it terminates.
+	exitCodeCh := make(chan int, 1)
+
+	// waitChild monitors the child for exit/signal; stop events are handled by
+	// the suspend goroutine above so we just loop past them here.
+	go func() {
+		for {
+			var ws syscall.WaitStatus
+			_, err := syscall.Wait4(childPid, &ws, syscall.WUNTRACED, nil)
+			if err != nil {
+				if err == syscall.EINTR {
+					continue
+				}
+				exitCodeCh <- 1
+				return
+			}
+
+			if ws.Exited() {
+				exitCodeCh <- ws.ExitStatus()
+				return
+			}
+			if ws.Signaled() {
+				exitCodeCh <- 128 + int(ws.Signal())
+				return
+			}
+			// ws.Stopped() — suspend goroutine handles this; loop for next event.
+		}
+	}()
 
 	if err := filterLoop(os.Stdout, ptmx, engine.ring); err != nil {
 		log.Printf("filter: %v", err)
 	}
 
-	if err := c.Wait(); err != nil {
-		var exitErr *exec.ExitError
-		if errors.As(err, &exitErr) {
-			return exitErr.ExitCode()
-		}
-		log.Printf("wait: %v", err)
-		return 1
-	}
-	return 0
+	return <-exitCodeCh
 }