fix: add /dev/tty fallback for MinTTY/Git Bash TTY detection

cmd/root.go

@@ -14,10 +14,36 @@ import (
 	"github.com/supermodeltools/cli/internal/shards"
 )
 
+// termIsTerminal wraps term.IsTerminal so tests can stub the syscall check
+// independently of the /dev/tty fallback.
+var termIsTerminal = func() bool {
+	return term.IsTerminal(int(syscall.Stdin)) //nolint:unconvert // syscall.Stdin is uintptr on Windows
+}
+
+// openDevTty opens /dev/tty (the process's controlling terminal). It is a
+// package-level var so tests can replace it with a mock. On Windows,
+// os.Open("/dev/tty") will fail, which is expected — Windows Console API
+// (used by term.IsTerminal above) handles Windows Terminal/PowerShell.
+var openDevTty = func() (*os.File, error) {
+	return os.Open("/dev/tty")
+}
+
 // stdinIsTerminal reports whether stdin is connected to an interactive
 // terminal. Pulled into a var so tests can stub it.
+//
+// MinTTY (Windows Git Bash) reports a non-terminal stdin fd even though the
+// user is at an interactive prompt, so we fall back to opening /dev/tty — the
+// POSIX controlling-terminal device. If it opens, stdin is interactive.
+// See issue #154.
 var stdinIsTerminal = func() bool {
-	return term.IsTerminal(int(syscall.Stdin)) //nolint:unconvert // syscall.Stdin is uintptr on Windows
+	if termIsTerminal() {
+		return true
+	}
+	if f, err := openDevTty(); err == nil {
+		f.Close()
+		return true
+	}
+	return false
 }
 
 // rootAction enumerates the three branches the bare `supermodel` command

cmd/root_test.go

@@ -1,6 +1,43 @@
 package cmd
 
-import "testing"
+import (
+	"os"
+	"testing"
+)
+
+// TestStdinIsTerminalUsesDevTtyFallback verifies that stdinIsTerminal falls
+// back to opening /dev/tty when term.IsTerminal returns false (e.g. in CI or
+// MinTTY/Git Bash on Windows). The fix is tracked in issue #154.
+func TestStdinIsTerminalUsesDevTtyFallback(t *testing.T) {
+	// Force termIsTerminal to return false so the test is deterministic
+	// regardless of whether the test process itself has an interactive stdin.
+	origTermIsTerminal := termIsTerminal
+	t.Cleanup(func() { termIsTerminal = origTermIsTerminal })
+	termIsTerminal = func() bool { return false }
+
+	// Save and restore the real openDevTty hook.
+	orig := openDevTty
+	t.Cleanup(func() { openDevTty = orig })
+
+	called := false
+	openDevTty = func() (*os.File, error) {
+		called = true
+		// Return a real, harmless file so the caller can call f.Close().
+		return os.Open(os.DevNull)
+	}
+
+	// With termIsTerminal stubbed to false, stdinIsTerminal must call
+	// openDevTty as a fallback and return true because our mock succeeds.
+	got := stdinIsTerminal()
+
+	if !called {
+		t.Error("stdinIsTerminal did not call openDevTty — /dev/tty fallback is missing (fix #154)")
+	}
+	// If openDevTty was called and succeeded, the result must be true.
+	if called && !got {
+		t.Error("openDevTty returned a file but stdinIsTerminal returned false — fix #154")
+	}
+}
 
 func TestPickRootAction(t *testing.T) {
 	cases := []struct {