diff --git a/custom_components/localthings/diagnostics.py b/custom_components/localthings/diagnostics.py
index b22896b..c95a5e7 100644
--- a/custom_components/localthings/diagnostics.py
+++ b/custom_components/localthings/diagnostics.py
@@ -31,9 +31,13 @@ async def async_get_config_entry_diagnostics(
     # detector when called inline here. Offload it to the executor.
     stl_version = await hass.async_add_executor_job(pkg_version, "smartthings-local")
 
-    # /oic/p and /oic/d sit outside the /device/0 batch captured below, so
-    # they'd otherwise never reach an issue report. /oic/d's `rt` is OCF's
-    # standard device-type declaration -- see registry/identity.py.
+    # /oic/p, /oic/d, and /oic/res sit outside the /device/0 batch captured
+    # below, so they'd otherwise never reach an issue report. /oic/d's `rt`
+    # is OCF's standard device-type declaration; /oic/res is OCF's
+    # discovery endpoint, listing every href/Collection the connection
+    # hosts -- relevant to the "Composite Device" model (issue #177) where
+    # a single physical unit exposes more than one logical Device. See
+    # registry/identity.py.
     identity = coordinator._identity
     return {
         "device_type": coordinator.device_type_name or "unknown",
diff --git a/custom_components/localthings/registry/identity.py b/custom_components/localthings/registry/identity.py
index c5445d1..81d6d5a 100644
--- a/custom_components/localthings/registry/identity.py
+++ b/custom_components/localthings/registry/identity.py
@@ -1,4 +1,4 @@
-"""Read device identity from standard OCF resources (/oic/p, /oic/d)."""
+"""Read device identity from standard OCF resources (/oic/p, /oic/d, /oic/res)."""
 from __future__ import annotations
 
 from dataclasses import dataclass, field
@@ -28,6 +28,20 @@ def _get(sess, path) -> dict:
     return {}
 
 
+def _get_links(sess, path) -> list:
+    """Like _get, but for /oic/res: a baseline-Interface RETRIEVE on it
+    returns a CBOR array of Link objects (href/rt/if/di/...), not a single
+    Property map."""
+    try:
+        code, pl = sess.get(path, timeout=10.0)
+        if code == 0x45 and pl:
+            body = cbor2.loads(pl)
+            return body if isinstance(body, list) else []
+    except Exception:
+        pass
+    return []
+
+
 def _device_types(d: dict) -> tuple[str, ...]:
     """/oic/d's `rt` -- the device's own OCF device-type declaration.
 
@@ -52,6 +66,16 @@ def _device_types(d: dict) -> tuple[str, ...]:
 def read_identity(sess, serial: Optional[str]) -> DeviceIdentity:
     p = _get(sess, ['oic', 'p'])
     d = _get(sess, ['oic', 'd'])
+    # /oic/res is OCF's baseline resource-discovery endpoint: a unicast
+    # RETRIEVE on it returns every Resource/Collection href this endpoint
+    # hosts, not just the one /device/0 seed path the coordinator polls.
+    # Relevant for the OCF "Composite Device" model (issue #177: a single
+    # physical unit -- one IP, one /oic/p -- exposing more than one logical
+    # Device, each as its own Collection resource, same rt shape as our own
+    # /device/0). Nothing consumes this yet; captured so a report from a
+    # multi-unit device shows us whether its firmware actually implements
+    # that model before any code assumes it does.
+    res = _get_links(sess, ['oic', 'res'])
     return DeviceIdentity(
         manufacturer=p.get('mnmn') or 'Samsung',
         model=p.get('mnmo') or '',
@@ -61,5 +85,5 @@ def read_identity(sess, serial: Optional[str]) -> DeviceIdentity:
         # Kept whole rather than field-by-field: these resources are outside
         # the /device/0 dump diagnostics already captures, and we don't yet
         # know which of their fields will turn out to identify a device type.
-        raw={'/oic/p': p, '/oic/d': d},
+        raw={'/oic/p': p, '/oic/d': d, '/oic/res': res},
     )
diff --git a/tests/localthings/test_diagnostics.py b/tests/localthings/test_diagnostics.py
index 446b539..f27c739 100644
--- a/tests/localthings/test_diagnostics.py
+++ b/tests/localthings/test_diagnostics.py
@@ -80,6 +80,48 @@ async def test_diagnostics_include_ocf_identity(
     assert identity['resources']['/oic/d']['rt'] == ['oic.wk.d', 'oic.d.refrigerator']
 
 
+async def test_diagnostics_include_oic_res_links(
+    hass: HomeAssistant, mock_entry, mock_coordinator_session
+) -> None:
+    """/oic/res -- OCF's resource-discovery endpoint -- rides along in
+    identity.raw the same way /oic/p and /oic/d do. Its response is a list
+    of Link objects (one per href/Collection the endpoint hosts), not a
+    single Property map, so redaction has to walk into the list too."""
+    from custom_components.localthings.registry.identity import DeviceIdentity
+
+    await hass.config_entries.async_setup(mock_entry.entry_id)
+    await hass.async_block_till_done()
+
+    coordinator = hass.data[DOMAIN][mock_entry.entry_id]
+    coordinator._identity = DeviceIdentity(
+        manufacturer='Samsung Electronics',
+        model='RF9000B',
+        name='Family Hub',
+        serial=None,
+        device_types=('oic.wk.d', 'oic.d.refrigerator'),
+        raw={
+            '/oic/p': {'mnmn': 'Samsung Electronics'},
+            '/oic/d': {'rt': ['oic.wk.d', 'oic.d.refrigerator']},
+            '/oic/res': [
+                {'di': 'aaaa-1111', 'href': '/device/0',
+                 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+                {'di': 'bbbb-2222', 'href': '/device/1',
+                 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+            ],
+        },
+    )
+
+    diag = await async_get_config_entry_diagnostics(hass, mock_entry)
+
+    links = diag['identity']['resources']['/oic/res']
+    assert len(links) == 2
+    assert links[0]['di'] == REDACTED
+    assert links[0]['href'] == '/device/0'
+    assert links[1]['di'] == REDACTED
+    assert links[1]['href'] == '/device/1'
+    assert links[1]['rt'] == ['x.com.samsung.devcol', 'oic.wk.col']
+
+
 async def test_diagnostics_identity_none_when_unavailable(
     hass: HomeAssistant, mock_entry, mock_coordinator_session
 ) -> None:
diff --git a/tests/test_identity.py b/tests/test_identity.py
index d9fa4dd..de922fc 100644
--- a/tests/test_identity.py
+++ b/tests/test_identity.py
@@ -32,7 +32,7 @@ def test_read_identity_tolerates_missing_resources():
     assert ident.model == ''
     assert ident.serial is None
     assert ident.device_types == ()
-    assert ident.raw == {'/oic/p': {}, '/oic/d': {}}
+    assert ident.raw == {'/oic/p': {}, '/oic/d': {}, '/oic/res': []}
 
 
 def test_read_identity_captures_oic_d_device_types():
@@ -69,3 +69,33 @@ def test_read_identity_keeps_raw_payloads_for_diagnostics():
     ident = read_identity(sess, serial=None)
     assert ident.raw['/oic/p']['mnmo'] == 'RF9000B'
     assert ident.raw['/oic/d']['di'] == 'abc-123'
+
+
+def test_read_identity_captures_oic_res_links():
+    """/oic/res is OCF's discovery endpoint: a baseline RETRIEVE returns an
+    array of Link objects, one per Resource/Collection the endpoint hosts --
+    including, per the OCF 'Composite Device' model, a second logical
+    Device's Collection on a multi-unit system (issue #177). Nothing routes
+    on this yet; captured so a report from such a device shows us whether
+    its firmware actually exposes more than the one /device/0 seed href."""
+    sess = FakeSession({
+        ('oic', 'res'): [
+            {'di': 'aaaa', 'href': '/device/0', 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+            {'di': 'bbbb', 'href': '/device/1', 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+        ],
+    })
+    ident = read_identity(sess, serial=None)
+    assert ident.raw['/oic/res'] == [
+        {'di': 'aaaa', 'href': '/device/0', 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+        {'di': 'bbbb', 'href': '/device/1', 'rt': ['x.com.samsung.devcol', 'oic.wk.col']},
+    ]
+
+
+def test_read_identity_tolerates_malformed_oic_res():
+    """A single Property map instead of an array (or anything else
+    non-list-shaped) must not explode -- same defensive posture as
+    _device_types' handling of a malformed /oic/d rt."""
+    ident = read_identity(
+        FakeSession({('oic', 'res'): {'not': 'a list'}}), serial=None
+    )
+    assert ident.raw['/oic/res'] == []