feat(v0.5.3): ResolveSessionMode env var resolver

internal/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -148,6 +149,25 @@ func defaultSeedDir(leaf string) string {
 	return filepath.Join(home, ".config", "ctask", leaf)
 }
 
+// ResolveSessionMode returns "direct" or "persistent" based on CTASK_SESSION_MODE.
+// Default (unset/empty) is "direct". Any other value falls back to "direct"
+// after printing a stderr warning. Used by entry commands (new, resume, last,
+// open) to dispatch between the standard session.Run path and the tmux-backed
+// persistent path.
+func ResolveSessionMode() string {
+	v := os.Getenv("CTASK_SESSION_MODE")
+	switch v {
+	case "", "direct":
+		return "direct"
+	case "persistent":
+		return "persistent"
+	default:
+		fmt.Fprintf(os.Stderr,
+			"[ctask] warning: CTASK_SESSION_MODE=%q is not recognized; using direct mode\n", v)
+		return "direct"
+	}
+}
+
 // expandPath expands a leading ~/ and resolves to an absolute path when possible.
 func expandPath(p string) string {
 	if strings.HasPrefix(p, "~/") || p == "~" {

internal/config/config_test.go

@@ -1,9 +1,11 @@
 package config
 
 import (
+	"io"
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 )
 
@@ -191,3 +193,61 @@ func TestEnvVarsLaunchDirEmpty(t *testing.T) {
 		t.Errorf("CTASK_LAUNCH_DIR: got %q, want empty", got)
 	}
 }
+
+func TestResolveSessionModeDefault(t *testing.T) {
+	os.Unsetenv("CTASK_SESSION_MODE")
+	if got := ResolveSessionMode(); got != "direct" {
+		t.Errorf("default: got %q, want %q", got, "direct")
+	}
+}
+
+func TestResolveSessionModeEmpty(t *testing.T) {
+	os.Setenv("CTASK_SESSION_MODE", "")
+	defer os.Unsetenv("CTASK_SESSION_MODE")
+	if got := ResolveSessionMode(); got != "direct" {
+		t.Errorf("empty: got %q, want %q", got, "direct")
+	}
+}
+
+func TestResolveSessionModeDirect(t *testing.T) {
+	os.Setenv("CTASK_SESSION_MODE", "direct")
+	defer os.Unsetenv("CTASK_SESSION_MODE")
+	if got := ResolveSessionMode(); got != "direct" {
+		t.Errorf("direct: got %q, want %q", got, "direct")
+	}
+}
+
+func TestResolveSessionModePersistent(t *testing.T) {
+	os.Setenv("CTASK_SESSION_MODE", "persistent")
+	defer os.Unsetenv("CTASK_SESSION_MODE")
+	if got := ResolveSessionMode(); got != "persistent" {
+		t.Errorf("persistent: got %q, want %q", got, "persistent")
+	}
+}
+
+func TestResolveSessionModeUnknownFallsBackWithWarning(t *testing.T) {
+	os.Setenv("CTASK_SESSION_MODE", "garbage")
+	defer os.Unsetenv("CTASK_SESSION_MODE")
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	origStderr := os.Stderr
+	os.Stderr = w
+	defer func() { os.Stderr = origStderr }()
+
+	got := ResolveSessionMode()
+	w.Close()
+	out, _ := io.ReadAll(r)
+
+	if got != "direct" {
+		t.Errorf("unknown: got %q, want %q (fallback)", got, "direct")
+	}
+	if !strings.Contains(string(out), "garbage") {
+		t.Errorf("warning should echo bad value: %q", out)
+	}
+	if !strings.Contains(string(out), "not recognized") {
+		t.Errorf("warning should say 'not recognized': %q", out)
+	}
+}