fix: create Codex account config directories

backend/internal/codex/client.go

@@ -41,6 +41,9 @@ func (c *Client) Start(ctx context.Context) error {
 	if c.connected {
 		return nil
 	}
+	if e := ensureConfigDir(c.configDir); e != nil {
+		return e
+	}
 	cmd := exec.CommandContext(ctx, "codex", "app-server")
 	cmd.Env = append(os.Environ(), "CODEX_HOME="+c.configDir)
 	out, e := cmd.StdoutPipe()
@@ -60,6 +63,13 @@ func (c *Client) Start(ctx context.Context) error {
 	go func() { _ = cmd.Wait(); c.failAll(cmd) }()
 	return nil
 }
+
+func ensureConfigDir(dir string) error {
+	if e := os.MkdirAll(dir, 0700); e != nil {
+		return fmt.Errorf("create CODEX_HOME %q: %w", dir, e)
+	}
+	return nil
+}
 func (c *Client) Initialize(ctx context.Context) error {
 	var out any
 	if e := c.Call(ctx, "initialize", map[string]any{"clientInfo": map[string]any{"name": "codex-helper", "title": "Codex Helper", "version": "0.1.0"}, "capabilities": map[string]any{}}, &out); e != nil {

backend/internal/codex/client_test.go

@@ -0,0 +1,41 @@
+package codex
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestEnsureConfigDirCreatesNestedDirectory(t *testing.T) {
+	dir := filepath.Join(t.TempDir(), "accounts", "2", "codex")
+	if err := ensureConfigDir(dir); err != nil {
+		t.Fatal(err)
+	}
+	info, err := os.Stat(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !info.IsDir() {
+		t.Fatalf("%s is not a directory", dir)
+	}
+	if got := info.Mode().Perm(); got != 0700 {
+		t.Fatalf("permissions = %o; want 700", got)
+	}
+}
+
+func TestEnsureConfigDirReportsCreationFailure(t *testing.T) {
+	parent := t.TempDir()
+	file := filepath.Join(parent, "not-a-directory")
+	if err := os.WriteFile(file, []byte("x"), 0600); err != nil {
+		t.Fatal(err)
+	}
+	dir := filepath.Join(file, "codex")
+	err := ensureConfigDir(dir)
+	if err == nil {
+		t.Fatal("expected directory creation to fail")
+	}
+	if !strings.Contains(err.Error(), "create CODEX_HOME") || !strings.Contains(err.Error(), dir) {
+		t.Fatalf("error = %q; want CODEX_HOME path context", err)
+	}
+}