diff --git a/.gitignore b/.gitignore
index 40bf80082..c2fe5c403 100644
--- a/.gitignore
+++ b/.gitignore
@@ -100,3 +100,6 @@ ENV/
 # mypy
 /.mypy_cache/*
 /.dmypy.json
+
+# Mac
+.DS_Store
\ No newline at end of file
diff --git a/supervisor/api/__init__.py b/supervisor/api/__init__.py
index 085eaa9b9..c9c9dc40b 100644
--- a/supervisor/api/__init__.py
+++ b/supervisor/api/__init__.py
@@ -198,6 +198,7 @@ class RestAPI(CoreSysAttributes):
                 web.post("/host/reload", api_host.reload),
                 web.post("/host/options", api_host.options),
                 web.get("/host/services", api_host.services),
+                web.get("/host/disks/default/usage", api_host.disk_usage),
             ]
         )
 
diff --git a/supervisor/api/const.py b/supervisor/api/const.py
index 6eb65df70..21578a5a8 100644
--- a/supervisor/api/const.py
+++ b/supervisor/api/const.py
@@ -49,6 +49,7 @@ ATTR_LLMNR_HOSTNAME = "llmnr_hostname"
 ATTR_LOCAL_ONLY = "local_only"
 ATTR_LOCATION_ATTRIBUTES = "location_attributes"
 ATTR_LOCATIONS = "locations"
+ATTR_MAX_DEPTH = "max_depth"
 ATTR_MDNS = "mdns"
 ATTR_MODEL = "model"
 ATTR_MOUNTS = "mounts"
diff --git a/supervisor/api/host.py b/supervisor/api/host.py
index 129b1da7a..fa2e6078f 100644
--- a/supervisor/api/host.py
+++ b/supervisor/api/host.py
@@ -51,6 +51,7 @@ from .const import (
     ATTR_FORCE,
     ATTR_IDENTIFIERS,
     ATTR_LLMNR_HOSTNAME,
+    ATTR_MAX_DEPTH,
     ATTR_STARTUP_TIME,
     ATTR_USE_NTP,
     ATTR_VIRTUALIZATION,
@@ -289,3 +290,49 @@ class APIHost(CoreSysAttributes):
     ) -> web.StreamResponse:
         """Return systemd-journald logs. Wrapped as standard API handler."""
         return await self.advanced_logs_handler(request, identifier, follow)
+
+    @api_process
+    async def disk_usage(self, request: web.Request) -> dict:
+        """Return a breakdown of storage usage for the system."""
+
+        max_depth = request.query.get(ATTR_MAX_DEPTH, 1)
+        try:
+            max_depth = int(max_depth)
+        except ValueError:
+            max_depth = 1
+
+        disk = self.sys_hardware.disk
+
+        total, used, _ = await self.sys_run_in_executor(
+            disk.disk_usage, self.sys_config.path_supervisor
+        )
+
+        known_paths = await self.sys_run_in_executor(
+            disk.get_dir_sizes,
+            {
+                "addons_data": self.sys_config.path_addons_data,
+                "addons_config": self.sys_config.path_addon_configs,
+                "media": self.sys_config.path_media,
+                "share": self.sys_config.path_share,
+                "backup": self.sys_config.path_backup,
+                "ssl": self.sys_config.path_ssl,
+                "homeassistant": self.sys_config.path_homeassistant,
+            },
+            max_depth,
+        )
+        return {
+            # this can be the disk/partition ID in the future
+            "id": "root",
+            "label": "Root",
+            "total_bytes": total,
+            "used_bytes": used,
+            "children": [
+                {
+                    "id": "system",
+                    "label": "System",
+                    "used_bytes": used
+                    - sum(path["used_bytes"] for path in known_paths),
+                },
+                *known_paths,
+            ],
+        }
diff --git a/supervisor/hardware/disk.py b/supervisor/hardware/disk.py
index bbe3d31b7..351768223 100644
--- a/supervisor/hardware/disk.py
+++ b/supervisor/hardware/disk.py
@@ -1,8 +1,12 @@
 """Read disk hardware info from system."""
 
+import errno
 import logging
 from pathlib import Path
 import shutil
+from typing import Any
+
+from supervisor.resolution.const import UnhealthyReason
 
 from ..coresys import CoreSys, CoreSysAttributes
 from ..exceptions import DBusError, DBusObjectError, HardwareNotFound
@@ -54,7 +58,7 @@ class HwDisk(CoreSysAttributes):
 
         Must be run in executor.
         """
-        total, _, _ = shutil.disk_usage(path)
+        total, _, _ = self.disk_usage(path)
         return round(total / (1024.0**3), 1)
 
     def get_disk_used_space(self, path: str | Path) -> float:
@@ -62,7 +66,7 @@ class HwDisk(CoreSysAttributes):
 
         Must be run in executor.
         """
-        _, used, _ = shutil.disk_usage(path)
+        _, used, _ = self.disk_usage(path)
         return round(used / (1024.0**3), 1)
 
     def get_disk_free_space(self, path: str | Path) -> float:
@@ -70,9 +74,84 @@ class HwDisk(CoreSysAttributes):
 
         Must be run in executor.
         """
-        _, _, free = shutil.disk_usage(path)
+        _, _, free = self.disk_usage(path)
         return round(free / (1024.0**3), 1)
 
+    def disk_usage(self, path: str | Path) -> tuple[int, int, int]:
+        """Return (total, used, free) in bytes for path.
+
+        Must be run in executor.
+        """
+        return shutil.disk_usage(path)
+
+    def get_dir_structure_sizes(self, path: Path, max_depth: int = 1) -> dict[str, Any]:
+        """Return a recursive dict of subdirectories and their sizes, only if size > 0.
+
+        Excludes external mounts and symlinks to avoid counting files on other filesystems
+        or following symlinks that could lead to infinite loops or incorrect sizes.
+        """
+
+        size = 0
+        if not path.exists():
+            return {"used_bytes": size}
+
+        children: list[dict[str, Any]] = []
+        root_device = path.stat().st_dev
+
+        for child in path.iterdir():
+            if not child.is_dir():
+                size += child.stat(follow_symlinks=False).st_size
+                continue
+
+            # Skip symlinks to avoid infinite loops
+            if child.is_symlink():
+                continue
+
+            try:
+                # Skip if not on same device (external mount)
+                if child.stat().st_dev != root_device:
+                    continue
+            except OSError as err:
+                if err.errno == errno.EBADMSG:
+                    self.sys_resolution.add_unhealthy_reason(
+                        UnhealthyReason.OSERROR_BAD_MESSAGE
+                    )
+                    break
+                continue
+
+            child_result = self.get_dir_structure_sizes(child, max_depth - 1)
+            if child_result["used_bytes"] > 0:
+                size += child_result["used_bytes"]
+                if max_depth > 1:
+                    children.append(
+                        {
+                            "id": child.name,
+                            "label": child.name,
+                            **child_result,
+                        }
+                    )
+
+        if children:
+            return {"used_bytes": size, "children": children}
+
+        return {"used_bytes": size}
+
+    def get_dir_sizes(
+        self, request: dict[str, Path], max_depth: int = 1
+    ) -> list[dict[str, Any]]:
+        """Accept a dictionary of `name: Path` and return a dictionary with `name: <size>`.
+
+        Must be run in executor.
+        """
+        return [
+            {
+                "id": name,
+                "label": name,
+                **self.get_dir_structure_sizes(path, max_depth),
+            }
+            for name, path in request.items()
+        ]
+
     def _get_mountinfo(self, path: str) -> list[str] | None:
         mountinfo = _MOUNTINFO.read_text(encoding="utf-8")
         for line in mountinfo.splitlines():
diff --git a/tests/api/test_host.py b/tests/api/test_host.py
index 444491a8b..385eac54a 100644
--- a/tests/api/test_host.py
+++ b/tests/api/test_host.py
@@ -381,6 +381,433 @@ async def test_advanced_logs_errors(coresys: CoreSys, api_client: TestClient):
     )
 
 
+async def test_disk_usage_api(api_client: TestClient, coresys: CoreSys):
+    """Test disk usage API endpoint."""
+    # Mock the disk usage methods
+    with (
+        patch.object(coresys.hardware.disk, "disk_usage") as mock_disk_usage,
+        patch.object(coresys.hardware.disk, "get_dir_sizes") as mock_dir_sizes,
+    ):
+        # Mock the main disk usage call
+        mock_disk_usage.return_value = (
+            1000000000,
+            500000000,
+            500000000,
+        )  # 1GB total, 500MB used, 500MB free
+
+        # Mock the directory structure sizes for each path
+        mock_dir_sizes.return_value = [
+            {
+                "id": "addons_data",
+                "label": "Addons Data",
+                "used_bytes": 100000000,
+                "children": [
+                    {"id": "addon1", "label": "addon1", "used_bytes": 50000000}
+                ],
+            },
+            {
+                "id": "addons_config",
+                "label": "Addons Config",
+                "used_bytes": 200000000,
+                "children": [
+                    {"id": "media1", "label": "media1", "used_bytes": 100000000}
+                ],
+            },
+            {
+                "id": "media",
+                "label": "Media",
+                "used_bytes": 50000000,
+                "children": [
+                    {"id": "share1", "label": "share1", "used_bytes": 25000000}
+                ],
+            },
+            {
+                "id": "share",
+                "label": "Share",
+                "used_bytes": 300000000,
+                "children": [
+                    {"id": "backup1", "label": "backup1", "used_bytes": 150000000}
+                ],
+            },
+            {
+                "id": "backup",
+                "label": "Backup",
+                "used_bytes": 10000000,
+                "children": [{"id": "ssl1", "label": "ssl1", "used_bytes": 5000000}],
+            },
+            {
+                "id": "ssl",
+                "label": "SSL",
+                "used_bytes": 40000000,
+                "children": [
+                    {
+                        "id": "homeassistant1",
+                        "label": "homeassistant1",
+                        "used_bytes": 20000000,
+                    }
+                ],
+            },
+            {
+                "id": "homeassistant",
+                "label": "Home Assistant",
+                "used_bytes": 40000000,
+                "children": [
+                    {
+                        "id": "homeassistant1",
+                        "label": "homeassistant1",
+                        "used_bytes": 20000000,
+                    }
+                ],
+            },
+        ]
+
+        # Test default max_depth=1
+        resp = await api_client.get("/host/disks/default/usage")
+        assert resp.status == 200
+        result = await resp.json()
+
+        assert result["data"]["id"] == "root"
+        assert result["data"]["label"] == "Root"
+        assert result["data"]["total_bytes"] == 1000000000
+        assert result["data"]["used_bytes"] == 500000000
+        assert "children" in result["data"]
+        children = result["data"]["children"]
+
+        # First child should be system
+        assert children[0]["id"] == "system"
+        assert children[0]["label"] == "System"
+
+        # Verify all expected directories are present in the remaining children
+        assert children[1]["id"] == "addons_data"
+        assert children[2]["id"] == "addons_config"
+        assert children[3]["id"] == "media"
+        assert children[4]["id"] == "share"
+        assert children[5]["id"] == "backup"
+        assert children[6]["id"] == "ssl"
+        assert children[7]["id"] == "homeassistant"
+
+        # Verify the sizes are correct
+        assert children[1]["used_bytes"] == 100000000
+        assert children[2]["used_bytes"] == 200000000
+        assert children[3]["used_bytes"] == 50000000
+        assert children[4]["used_bytes"] == 300000000
+        assert children[5]["used_bytes"] == 10000000
+        assert children[6]["used_bytes"] == 40000000
+        assert children[7]["used_bytes"] == 40000000
+
+        # Verify system space calculation (total used - sum of known paths)
+        total_known_space = (
+            100000000
+            + 200000000
+            + 50000000
+            + 300000000
+            + 10000000
+            + 40000000
+            + 40000000
+        )
+        expected_system_space = 500000000 - total_known_space
+        assert children[0]["used_bytes"] == expected_system_space
+
+        # Verify disk_usage was called with supervisor path
+        mock_disk_usage.assert_called_once_with(coresys.config.path_supervisor)
+
+        # Verify get_dir_sizes was called once with all paths
+        assert mock_dir_sizes.call_count == 1
+        call_args = mock_dir_sizes.call_args
+        assert call_args[0][1] == 1  # max_depth parameter
+        paths_dict = call_args[0][0]  # paths dictionary
+        assert paths_dict["addons_data"] == coresys.config.path_addons_data
+        assert paths_dict["addons_config"] == coresys.config.path_addon_configs
+        assert paths_dict["media"] == coresys.config.path_media
+        assert paths_dict["share"] == coresys.config.path_share
+        assert paths_dict["backup"] == coresys.config.path_backup
+        assert paths_dict["ssl"] == coresys.config.path_ssl
+        assert paths_dict["homeassistant"] == coresys.config.path_homeassistant
+
+
+async def test_disk_usage_api_with_custom_depth(
+    api_client: TestClient, coresys: CoreSys
+):
+    """Test disk usage API endpoint with custom max_depth parameter."""
+    with (
+        patch.object(coresys.hardware.disk, "disk_usage") as mock_disk_usage,
+        patch.object(coresys.hardware.disk, "get_dir_sizes") as mock_dir_sizes,
+    ):
+        mock_disk_usage.return_value = (1000000000, 500000000, 500000000)
+
+        # Mock deeper directory structure
+        mock_dir_sizes.return_value = [
+            {
+                "id": "addons_data",
+                "label": "Addons Data",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "addons_config",
+                "label": "Addons Config",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "media",
+                "label": "Media",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "share",
+                "label": "Share",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "backup",
+                "label": "Backup",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "ssl",
+                "label": "SSL",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+            {
+                "id": "homeassistant",
+                "label": "Home Assistant",
+                "used_bytes": 100000000,
+                "children": [
+                    {
+                        "id": "addon1",
+                        "label": "addon1",
+                        "used_bytes": 50000000,
+                        "children": [
+                            {
+                                "id": "subdir1",
+                                "label": "subdir1",
+                                "used_bytes": 25000000,
+                            },
+                        ],
+                    },
+                ],
+            },
+        ]
+
+        # Test with custom max_depth=2
+        resp = await api_client.get("/host/disks/default/usage?max_depth=2")
+        assert resp.status == 200
+        result = await resp.json()
+        assert result["data"]["used_bytes"] == 500000000
+        assert result["data"]["children"]
+
+        # Verify max_depth=2 was passed to get_dir_sizes
+        assert mock_dir_sizes.call_count == 1
+        call_args = mock_dir_sizes.call_args
+        assert call_args[0][1] == 2  # max_depth parameter
+
+
+async def test_disk_usage_api_invalid_depth(api_client: TestClient, coresys: CoreSys):
+    """Test disk usage API endpoint with invalid max_depth parameter."""
+    with (
+        patch.object(coresys.hardware.disk, "disk_usage") as mock_disk_usage,
+        patch.object(coresys.hardware.disk, "get_dir_sizes") as mock_dir_sizes,
+    ):
+        mock_disk_usage.return_value = (1000000000, 500000000, 500000000)
+        mock_dir_sizes.return_value = [
+            {
+                "id": "addons_data",
+                "label": "Addons Data",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "addons_config",
+                "label": "Addons Config",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "media",
+                "label": "Media",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "share",
+                "label": "Share",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "backup",
+                "label": "Backup",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "ssl",
+                "label": "SSL",
+                "used_bytes": 100000000,
+            },
+            {
+                "id": "homeassistant",
+                "label": "Home Assistant",
+                "used_bytes": 100000000,
+            },
+        ]
+
+        # Test with invalid max_depth (non-integer)
+        resp = await api_client.get("/host/disks/default/usage?max_depth=invalid")
+        assert resp.status == 200
+        result = await resp.json()
+        assert result["data"]["used_bytes"] == 500000000
+        assert result["data"]["children"]
+
+        # Should default to max_depth=1 when invalid value is provided
+        assert mock_dir_sizes.call_count == 1
+        call_args = mock_dir_sizes.call_args
+        assert call_args[0][1] == 1  # Should default to 1
+
+
+async def test_disk_usage_api_empty_directories(
+    api_client: TestClient, coresys: CoreSys
+):
+    """Test disk usage API endpoint with empty directories."""
+    with (
+        patch.object(coresys.hardware.disk, "disk_usage") as mock_disk_usage,
+        patch.object(coresys.hardware.disk, "get_dir_sizes") as mock_dir_sizes,
+    ):
+        mock_disk_usage.return_value = (1000000000, 500000000, 500000000)
+
+        # Mock empty directory structures (no children)
+        mock_dir_sizes.return_value = [
+            {
+                "id": "addons_data",
+                "label": "Addons Data",
+                "used_bytes": 0,
+            },
+            {
+                "id": "addons_config",
+                "label": "Addons Config",
+                "used_bytes": 0,
+            },
+            {
+                "id": "media",
+                "label": "Media",
+                "used_bytes": 0,
+            },
+            {
+                "id": "share",
+                "label": "Share",
+                "used_bytes": 0,
+            },
+            {
+                "id": "backup",
+                "label": "Backup",
+                "used_bytes": 0,
+            },
+            {
+                "id": "ssl",
+                "label": "SSL",
+                "used_bytes": 0,
+            },
+            {
+                "id": "homeassistant",
+                "label": "Home Assistant",
+                "used_bytes": 0,
+            },
+        ]
+
+        resp = await api_client.get("/host/disks/default/usage")
+        assert resp.status == 200
+        result = await resp.json()
+
+        assert result["data"]["used_bytes"] == 500000000
+        children = result["data"]["children"]
+
+        # First child should be system with all the space
+        assert children[0]["id"] == "system"
+        assert children[0]["used_bytes"] == 500000000
+
+        # All other directories should have size 0
+        for i in range(1, len(children)):
+            assert children[i]["used_bytes"] == 0
+
+
 @pytest.mark.parametrize("action", ["reboot", "shutdown"])
 async def test_migration_blocks_shutdown(
     api_client: TestClient,
diff --git a/tests/hardware/test_disk.py b/tests/hardware/test_disk.py
index d4e253bce..5ed0d9f25 100644
--- a/tests/hardware/test_disk.py
+++ b/tests/hardware/test_disk.py
@@ -1,6 +1,8 @@
 """Test hardware utils."""
 
 # pylint: disable=protected-access
+import errno
+import os
 from pathlib import Path
 from unittest.mock import patch
 
@@ -9,6 +11,7 @@ import pytest
 
 from supervisor.coresys import CoreSys
 from supervisor.hardware.data import Device
+from supervisor.resolution.const import UnhealthyReason
 
 from tests.common import mock_dbus_services
 from tests.dbus_service_mocks.base import DBusServiceMock
@@ -150,6 +153,141 @@ def test_get_mount_source(coresys):
     assert mount_source == "proc"
 
 
+def test_get_dir_structure_sizes(coresys, tmp_path):
+    """Test directory structure size calculation."""
+    # Create a test directory structure
+    test_dir = tmp_path / "test_dir"
+    test_dir.mkdir()
+
+    # Create some files
+    (test_dir / "file1.txt").write_text("content1")
+    (test_dir / "file2.txt").write_text("content2" * 100)  # Larger file
+
+    # Create subdirectories
+    subdir1 = test_dir / "subdir1"
+    subdir1.mkdir()
+    (subdir1 / "file3.txt").write_text("content3")
+
+    subdir2 = test_dir / "subdir2"
+    subdir2.mkdir()
+    (subdir2 / "file4.txt").write_text("content4")
+
+    # Create nested subdirectory
+    nested_dir = subdir1 / "nested"
+    nested_dir.mkdir()
+    (nested_dir / "file5.txt").write_text("content5")
+
+    # Create a symlink (should be skipped)
+    (test_dir / "symlink.txt").symlink_to(test_dir / "file1.txt")
+
+    # Test with max_depth=1 (default)
+    result = coresys.hardware.disk.get_dir_structure_sizes(test_dir, max_depth=1)
+
+    # Verify the structure
+    assert result["used_bytes"] > 0
+    assert "children" not in result
+
+    result = coresys.hardware.disk.get_dir_structure_sizes(test_dir, max_depth=2)
+
+    # Verify the structure
+    assert result["used_bytes"] > 0
+    assert "children" in result
+    children = result["children"]
+
+    # Should have subdir1 and subdir2, but not nested (due to max_depth=1)
+    child_names = [child["id"] for child in children]
+    assert "subdir1" in child_names
+    assert "subdir2" in child_names
+    assert "nested" not in child_names
+
+    # Verify sizes are calculated correctly
+    subdir1 = next(child for child in children if child["id"] == "subdir1")
+    subdir2 = next(child for child in children if child["id"] == "subdir2")
+    assert subdir1["used_bytes"] > 0
+    assert subdir2["used_bytes"] > 0
+    assert "children" not in subdir1  # No children due to max_depth=1
+    assert "children" not in subdir2
+
+    # Test with max_depth=2
+    result = coresys.hardware.disk.get_dir_structure_sizes(test_dir, max_depth=3)
+
+    # Should now include nested directory
+    child_names = [child["id"] for child in result["children"]]
+    assert "subdir1" in child_names
+    assert "subdir2" in child_names
+
+    subdir1 = next(child for child in result["children"] if child["id"] == "subdir1")
+    nested_children = [child["id"] for child in subdir1["children"]]
+    assert "nested" in nested_children
+    nested = next(child for child in subdir1["children"] if child["id"] == "nested")
+    assert nested["used_bytes"] > 0
+
+    # Test with max_depth=0 (should only count files in root, no children)
+    result = coresys.hardware.disk.get_dir_structure_sizes(test_dir, max_depth=0)
+    assert result["used_bytes"] > 0
+    assert "children" not in result  # No children due to max_depth=0
+
+
+def test_get_dir_structure_sizes_empty_dir(coresys, tmp_path):
+    """Test directory structure size calculation with empty directory."""
+    empty_dir = tmp_path / "empty_dir"
+    empty_dir.mkdir()
+
+    result = coresys.hardware.disk.get_dir_structure_sizes(empty_dir)
+
+    assert result["used_bytes"] == 0
+    assert "children" not in result
+
+
+def test_get_dir_structure_sizes_nonexistent_dir(coresys, tmp_path):
+    """Test directory structure size calculation with nonexistent directory."""
+    nonexistent_dir = tmp_path / "nonexistent"
+
+    result = coresys.hardware.disk.get_dir_structure_sizes(nonexistent_dir)
+
+    assert result["used_bytes"] == 0
+    assert "children" not in result
+
+
+def test_get_dir_structure_sizes_only_files(coresys, tmp_path):
+    """Test directory structure size calculation with only files (no subdirectories)."""
+    files_dir = tmp_path / "files_dir"
+    files_dir.mkdir()
+
+    # Create some files
+    (files_dir / "file1.txt").write_text("content1")
+    (files_dir / "file2.txt").write_text("content2" * 50)
+
+    result = coresys.hardware.disk.get_dir_structure_sizes(files_dir)
+
+    assert result["used_bytes"] > 0
+    assert "children" not in result  # No children since no subdirectories
+
+
+def test_get_dir_structure_sizes_zero_size_children(coresys, tmp_path):
+    """Test directory structure size calculation with zero-size children."""
+    test_dir = tmp_path / "zero_size_test"
+    test_dir.mkdir()
+
+    # Create a file in root
+    (test_dir / "file1.txt").write_text("content1")
+
+    # Create an empty subdirectory
+    empty_subdir = test_dir / "empty_subdir"
+    empty_subdir.mkdir()
+
+    # Create a subdirectory with content
+    content_subdir = test_dir / "content_subdir"
+    content_subdir.mkdir()
+    (content_subdir / "file2.txt").write_text("content2")
+
+    result = coresys.hardware.disk.get_dir_structure_sizes(test_dir)
+
+    # Should include content_subdir but not empty_subdir (since size > 0)
+    assert result["used_bytes"] > 0
+    assert "children" not in result
+
+
 def test_try_get_emmc_life_time(coresys, tmp_path):
     """Test eMMC life time helper."""
     fake_life_time = tmp_path / "fake-mmcblk0-lifetime"
@@ -163,6 +301,53 @@ def test_try_get_emmc_life_time(coresys, tmp_path):
     assert value == 10.0
 
 
+def test_get_dir_structure_sizes_ebadmsg_error(coresys, tmp_path):
+    """Test directory structure size calculation with EBADMSG error."""
+    # Create a test directory structure
+    test_dir = tmp_path / "test_dir"
+    test_dir.mkdir()
+
+    # Create some files
+    (test_dir / "file1.txt").write_text("content1")
+
+    # Create a subdirectory
+    subdir = test_dir / "subdir"
+    subdir.mkdir()
+    (subdir / "file2.txt").write_text("content2")
+
+    # Mock is_dir, is_symlink, and stat methods to handle the EBADMSG error correctly
+
+    def mock_is_dir(self):
+        # Use the real is_dir for all paths
+        return os.path.isdir(self)
+
+    def mock_is_symlink(self):
+        # Use the real is_symlink for all paths
+        return os.path.islink(self)
+
+    def mock_stat_ebadmsg(self, follow_symlinks=True):
+        if self == subdir:
+            raise OSError(errno.EBADMSG, "Bad message")
+        # For other paths, use the real os.stat
+        return os.stat(self, follow_symlinks=follow_symlinks)
+
+    with (
+        patch.object(Path, "is_dir", mock_is_dir),
+        patch.object(Path, "is_symlink", mock_is_symlink),
+        patch.object(Path, "stat", mock_stat_ebadmsg),
+    ):
+        result = coresys.hardware.disk.get_dir_structure_sizes(test_dir)
+
+    # The EBADMSG error should cause the loop to break, so we get 0 used space
+    # because the error happens before processing the file in the root directory
+    assert result["used_bytes"] == 0
+    assert "children" not in result
+
+    # Verify that the unhealthy reason was added
+    assert coresys.resolution.unhealthy
+    assert UnhealthyReason.OSERROR_BAD_MESSAGE in coresys.resolution.unhealthy
+
+
 async def test_try_get_nvme_life_time(
     coresys: CoreSys, nvme_data_disk: NVMeControllerService
 ):