[dashboard] Fix binary download with packages using secrets after Path migration (#11313)

tests/dashboard/test_settings.py

@@ -2,11 +2,13 @@
 
 from __future__ import annotations
 
+from argparse import Namespace
 from pathlib import Path
 import tempfile
 
 import pytest
 
+from esphome.core import CORE
 from esphome.dashboard.settings import DashboardSettings
 
 
@@ -159,3 +161,63 @@ def test_rel_path_with_numeric_args(dashboard_settings: DashboardSettings) -> No
     result = dashboard_settings.rel_path("123", "456.789")
     expected = dashboard_settings.config_dir / "123" / "456.789"
     assert result == expected
+
+
+def test_config_path_parent_resolves_to_config_dir(tmp_path: Path) -> None:
+    """Test that CORE.config_path.parent resolves to config_dir after parse_args.
+
+    This is a regression test for issue #11280 where binary download failed
+    when using packages with secrets after the Path migration in 2025.10.0.
+
+    The issue was that after switching from os.path to Path:
+    - Before: os.path.dirname("/config/.") → "/config"
+    - After: Path("/config/.").parent → Path("/") (normalized first!)
+
+    The fix uses a sentinel file so .parent returns the correct directory:
+    - Fixed: Path("/config/___DASHBOARD_SENTINEL___.yaml").parent → Path("/config")
+    """
+    # Create test directory structure with secrets and packages
+    config_dir = tmp_path / "config"
+    config_dir.mkdir()
+
+    # Create secrets.yaml with obviously fake test values
+    secrets_file = config_dir / "secrets.yaml"
+    secrets_file.write_text(
+        "wifi_ssid: TEST-DUMMY-SSID\n"
+        "wifi_password: not-a-real-password-just-for-testing\n"
+    )
+
+    # Create package file that uses secrets
+    package_file = config_dir / "common.yaml"
+    package_file.write_text(
+        "wifi:\n  ssid: !secret wifi_ssid\n  password: !secret wifi_password\n"
+    )
+
+    # Create main device config that includes the package
+    device_config = config_dir / "test-device.yaml"
+    device_config.write_text(
+        "esphome:\n  name: test-device\n\npackages:\n  common: !include common.yaml\n"
+    )
+
+    # Set up dashboard settings with our test config directory
+    settings = DashboardSettings()
+    args = Namespace(
+        configuration=str(config_dir),
+        password=None,
+        username=None,
+        ha_addon=False,
+        verbose=False,
+    )
+    settings.parse_args(args)
+
+    # Verify that CORE.config_path.parent correctly points to the config directory
+    # This is critical for secret resolution in yaml_util.py which does:
+    #   main_config_dir = CORE.config_path.parent
+    #   main_secret_yml = main_config_dir / "secrets.yaml"
+    assert CORE.config_path.parent == config_dir.resolve()
+    assert (CORE.config_path.parent / "secrets.yaml").exists()
+    assert (CORE.config_path.parent / "common.yaml").exists()
+
+    # Verify that CORE.config_path itself uses the sentinel file
+    assert CORE.config_path.name == "___DASHBOARD_SENTINEL___.yaml"
+    assert not CORE.config_path.exists()  # Sentinel file doesn't actually exist