1 files changed, 189 insertions, 7 deletions
diff --git a/cmd/internal/hexai-action/main.go b/cmd/internal/hexai-action/main.go
index 8bcc3cd..b8ba524 100644
--- a/cmd/internal/hexai-action/main.go
+++ b/cmd/internal/hexai-action/main.go
@@ -6,24 +6,62 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
+	"time"
 
 	"codeberg.org/snonux/hexai/internal/hexaiaction"
+	"codeberg.org/snonux/hexai/internal/tmux"
+	"golang.org/x/term"
 )
 
 func main() {
 	infile := flag.String("infile", "", "Read input from this file instead of stdin")
 	outfile := flag.String("outfile", "", "Write output to this file instead of stdout")
+	// Tmux/UI flags
+	forceTmux := flag.Bool("tmux", false, "Force running the UI in a tmux split-pane (auto if not set)")
+	noTmux := flag.Bool("no-tmux", false, "Disable tmux mode even if available")
+	uiChild := flag.Bool("ui-child", false, "INTERNAL: run interactive UI and write to -outfile atomically")
+	tmuxTarget := flag.String("tmux-target", "", "tmux split target (advanced)")
+	tmuxSplit := flag.String("tmux-split", "v", "tmux split orientation: v or h")
+	tmuxPercent := flag.Int("tmux-percent", 33, "tmux split size percentage (1-100)")
 	flag.Parse()
 
-	in, out, closeIn, closeOut, err := openIO(*infile, *outfile)
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
+	// Child mode: run TUI and write atomically to -outfile
+	if *uiChild {
+		if err := runChild(*infile, *outfile); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		return
+	}
+
+	// Parent mode: decide inline vs tmux
+	if shouldRunInTmux(*forceTmux, *noTmux) {
+		if err := runInTmuxParent(*tmuxTarget, *tmuxSplit, *tmuxPercent); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		return
 	}
-	defer closeIn()
-	defer closeOut()
 
-	if err := hexaiaction.Run(context.Background(), in, out, os.Stderr); err != nil {
+	// Inline path: only if we have a TTY for UI; otherwise echo input
+	if isTTY(os.Stdout.Fd()) && isTTY(os.Stdin.Fd()) {
+		in, out, closeIn, closeOut, err := openIO(*infile, *outfile)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		defer closeIn()
+		defer closeOut()
+        if err := hexaiactionRun(context.Background(), in, out, os.Stderr); err != nil {
+            fmt.Fprintln(os.Stderr, err)
+            os.Exit(1)
+        }
+        return
+    }
+
+	// Fallback: no TTY and tmux not available; echo input to output
+	if err := echoThrough(*infile, *outfile); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
@@ -54,3 +92,147 @@ func openIO(infile, outfile string) (io.Reader, io.Writer, func(), func(), error
 	}
 	return in, out, closeIn, closeOut, nil
 }
+
+// runChild runs the interactive flow and writes the final output atomically to outfile.
+var hexaiactionRun = hexaiaction.Run
+
+func runChild(infile, outfile string) error {
+	if outfile == "" {
+		// No atomic handoff needed; just run normally to stdout
+		in, out, closeIn, closeOut, err := openIO(infile, "")
+		if err != nil {
+			return err
+		}
+		defer closeIn()
+		defer closeOut()
+        return hexaiactionRun(context.Background(), in, out, os.Stderr)
+	}
+	tmp := outfile + ".tmp"
+	in, out, closeIn, closeOut, err := openIO(infile, tmp)
+	if err != nil {
+		return err
+	}
+	defer closeIn()
+    if err := hexaiactionRun(context.Background(), in, out, os.Stderr); err != nil {
+        // On error, try to echo input to tmp to avoid blocking
+        closeOut()
+        if copyErr := echoThrough(infile, tmp); copyErr != nil {
+            return fmt.Errorf("hexai-action child: %v; echo failed: %v", err, copyErr)
+        }
+	} else {
+		closeOut()
+	}
+	return os.Rename(tmp, outfile)
+}
+
+var isTTYFn = isTTY
+var tmuxAvailableFn = tmux.Available
+var splitRunFn = tmux.SplitRun
+var osExecutableFn = os.Executable
+
+func shouldRunInTmux(forceTmux, noTmux bool) bool {
+	if noTmux {
+		return false
+	}
+	if forceTmux {
+		return true
+	}
+	// Auto: prefer tmux when stdio are not TTYs (Helix :pipe scenario)
+    if !(isTTYFn(os.Stdin.Fd()) && isTTYFn(os.Stdout.Fd())) && tmuxAvailableFn() {
+        return true
+    }
+	return false
+}
+
+func isTTY(fd uintptr) bool { return term.IsTerminal(int(fd)) }
+
+func runInTmuxParent(target, split string, percent int) error {
+	// Prepare temp files
+	dir, err := os.MkdirTemp("", "hexai-action-")
+	if err != nil {
+		return err
+	}
+	defer func() { _ = os.RemoveAll(dir) }()
+	inPath := filepath.Join(dir, "input.txt")
+	outPath := filepath.Join(dir, "reply.txt")
+	// Read stdin and persist to inPath
+	if err := persistStdin(inPath); err != nil {
+		return err
+	}
+	// Build child argv
+	exe, err := osExecutableFn()
+	if err != nil {
+		return err
+	}
+	argv := []string{exe, "-ui-child", "-infile", inPath, "-outfile", outPath}
+	// Spawn tmux split
+	opts := tmux.SplitOpts{Target: target, Vertical: split != "h", Percent: percent}
+	if err := splitRunFn(opts, argv); err != nil {
+		return err
+	}
+	// Wait for outfile to appear
+	if err := waitForFile(outPath, 60*time.Second); err != nil {
+		return err
+	}
+	// Print to stdout
+	return catFileToStdout(outPath)
+}
+
+func persistStdin(path string) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	if _, err := io.Copy(f, os.Stdin); err != nil {
+		return err
+	}
+	return f.Sync()
+}
+
+func waitForFile(path string, timeout time.Duration) error {
+	deadline := time.Now().Add(timeout)
+	for {
+		if _, err := os.Stat(path); err == nil {
+			return nil
+		}
+		if time.Now().After(deadline) {
+			return fmt.Errorf("hexai-action: timeout waiting for reply file")
+		}
+		time.Sleep(200 * time.Millisecond)
+	}
+}
+
+func catFileToStdout(path string) error {
+	f, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	_, err = io.Copy(os.Stdout, f)
+	return err
+}
+
+func echoThrough(infile, outfile string) error {
+	// Read from infile or stdin and write to outfile or stdout
+	var in io.Reader = os.Stdin
+	var out io.Writer = os.Stdout
+	if infile != "" {
+		f, err := os.Open(infile)
+		if err != nil {
+			return err
+		}
+		defer func() { _ = f.Close() }()
+		in = f
+	}
+	if outfile != "" {
+		f, err := os.Create(outfile)
+		if err != nil {
+			return err
+		}
+		defer func() { _ = f.Close() }()
+		out = f
+	}
+	_, err := io.Copy(out, in)
+	return err
+}