diff --git a/ocf/__init__.py b/ocf/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/samsung_appliance/keepalive.py b/ocf/keepalive.py
similarity index 98%
rename from samsung_appliance/keepalive.py
rename to ocf/keepalive.py
index 11fe464..9543770 100644
--- a/samsung_appliance/keepalive.py
+++ b/ocf/keepalive.py
@@ -20,7 +20,7 @@ from __future__ import annotations
 import threading
 from typing import Callable, Optional
 
-from .coap_dtls import DtlsCoapSession
+from protocol.dtls_session import DtlsCoapSession
 
 
 class KeepaliveTask:
diff --git a/samsung_appliance/observe_refresh.py b/ocf/observe_refresh.py
similarity index 97%
rename from samsung_appliance/observe_refresh.py
rename to ocf/observe_refresh.py
index bb8c24d..15a9ca0 100644
--- a/samsung_appliance/observe_refresh.py
+++ b/ocf/observe_refresh.py
@@ -17,7 +17,7 @@ from __future__ import annotations
 import threading
 from typing import Optional
 
-from .coap_dtls import DtlsCoapSession
+from protocol.dtls_session import DtlsCoapSession
 
 
 class ObserveRefreshTask:
diff --git a/samsung_appliance/poll_scheduler.py b/ocf/poll_scheduler.py
similarity index 98%
rename from samsung_appliance/poll_scheduler.py
rename to ocf/poll_scheduler.py
index ff8e6ba..0ba2773 100644
--- a/samsung_appliance/poll_scheduler.py
+++ b/ocf/poll_scheduler.py
@@ -36,7 +36,7 @@ from typing import Callable, Optional, TYPE_CHECKING
 
 import cbor2
 
-from .coap_dtls import DtlsCoapSession, fmt_code
+from protocol.dtls_session import DtlsCoapSession, fmt_code
 
 if TYPE_CHECKING:
     from .state_cache import StateCache
@@ -61,7 +61,6 @@ class PollScheduler:
                  session: DtlsCoapSession,
                  cache: 'StateCache',
                  tiers: list[PollTier],
-                 sweep_index_fn: Callable[[object], dict[str, dict]],
                  is_active_fn: Optional[Callable[[dict[str, dict]], bool]] = None,
                  logger=None,
                  timeout_s: float = 8.0,
@@ -69,7 +68,6 @@ class PollScheduler:
         self.session = session
         self.cache = cache
         self.tiers = tiers
-        self.sweep_index = sweep_index_fn
         self.is_active_fn = is_active_fn
         self.log = logger
         self.timeout_s = timeout_s
@@ -301,7 +299,7 @@ class PollScheduler:
             self._poll_error_count += 1
             if self.log: self.log.warning("sweep cbor: %s", e)
             return
-        indexed = self.sweep_index(tree)
+        indexed = self.cache.index_device_tree(tree)
         for href, rep in indexed.items():
             with self._defer_lock:
                 if self._defer_until.get(href, 0) > time.monotonic():
diff --git a/samsung_appliance/state_cache.py b/ocf/state_cache.py
similarity index 77%
rename from samsung_appliance/state_cache.py
rename to ocf/state_cache.py
index 852c34f..a8e7ee0 100644
--- a/samsung_appliance/state_cache.py
+++ b/ocf/state_cache.py
@@ -58,6 +58,23 @@ class StateCache:
             merged.update(body)
         return self.apply_rep(href, merged, source='optimistic')
 
+    @staticmethod
+    def index_device_tree(device0_body) -> dict[str, dict]:
+        """Turn a /device/0 CBOR list-of-{href, rep} sweep response into
+        a dict keyed by href. Entry [0] is the device-level rep itself
+        and isn't useful here, so it's skipped.
+
+        Replaces the old standalone sensors.index_links — folded in
+        here because every current and future caller immediately feeds
+        the result into apply_rep on this same cache."""
+        out: dict[str, dict] = {}
+        if not isinstance(device0_body, list):
+            return out
+        for entry in device0_body[1:]:
+            if isinstance(entry, dict) and 'href' in entry:
+                out[entry['href']] = entry.get('rep') or {}
+        return out
+
     def get(self, href: str) -> Optional[dict]:
         with self._lock:
             return self.links.get(href)
diff --git a/samsung_appliance/bridge.py b/samsung_appliance/bridge.py
index 43dec1a..e7e332c 100644
--- a/samsung_appliance/bridge.py
+++ b/samsung_appliance/bridge.py
@@ -24,14 +24,13 @@ import time
 import cbor2
 
 from .appliances.base import ApplianceDescriptor, bridge_diagnostic_discovery
-from .coap_dtls import DtlsCoapSession, fmt_code
 from .config import ApplianceConfig, SharedConfig
-from .keepalive import KeepaliveTask
 from .logger import bridge_logger
-from .observe_refresh import ObserveRefreshTask
-from .poll_scheduler import PollScheduler
-from .sensors import index_links
-from .state_cache import StateCache
+from protocol.dtls_session import DtlsCoapSession, fmt_code
+from ocf.keepalive import KeepaliveTask
+from ocf.observe_refresh import ObserveRefreshTask
+from ocf.poll_scheduler import PollScheduler
+from ocf.state_cache import StateCache
 
 
 DEBUG_BRIDGE = os.environ.get('DEBUG_BRIDGE') == '1'
@@ -295,7 +294,6 @@ class PushBridge:
         scheduler = PollScheduler(
             sess, self.cache,
             tiers=self.descriptor.poll_tiers,
-            sweep_index_fn=index_links,
             is_active_fn=self.descriptor.is_active,
             logger=self.log,
         )
@@ -357,7 +355,7 @@ class PushBridge:
         # During the seed we want the cache populated without triggering
         # a publish per resource — gate the on_change callback off until
         # the publish gate opens just below.
-        for href, rep in index_links(body).items():
+        for href, rep in StateCache.index_device_tree(body).items():
             if href not in self.cache.links:
                 self.cache.apply_rep(href, rep, source='seed')
         self.last_seed_ts = time.time()
diff --git a/samsung_appliance/sensors.py b/samsung_appliance/sensors.py
deleted file mode 100644
index 5344492..0000000
--- a/samsung_appliance/sensors.py
+++ /dev/null
@@ -1,19 +0,0 @@
-"""Shared sensor helpers.
-
-Appliance-specific flattening lives in samsung_appliance/appliances/*.py;
-this module only carries utilities that every descriptor uses (currently
-the /device/0 link-dict indexer).
-"""
-
-
-def index_links(device0_body):
-    """Turn the /device/0 CBOR list-of-{href, rep} into a dict keyed
-    by href. The first list entry is the device-level rep itself and
-    isn't useful here, so skip it."""
-    out = {}
-    if not isinstance(device0_body, list):
-        return out
-    for entry in device0_body[1:]:
-        if isinstance(entry, dict) and 'href' in entry:
-            out[entry['href']] = entry.get('rep') or {}
-    return out
diff --git a/tests/test_state_cache.py b/tests/test_state_cache.py
new file mode 100644
index 0000000..a505176
--- /dev/null
+++ b/tests/test_state_cache.py
@@ -0,0 +1,40 @@
+# tests/test_state_cache.py
+from ocf.state_cache import StateCache
+
+
+class _FakeDescriptor:
+    on_observation = None
+
+
+def test_index_device_tree_skips_device_level_entry_at_index_zero():
+    tree = [
+        {'href': '/device/0', 'rep': {'n': 'Dryer'}},   # device-level, skipped
+        {'href': '/mode/vs/0', 'rep': {'x': 1}},
+        {'href': '/power/vs/0', 'rep': {'y': 2}},
+    ]
+    indexed = StateCache.index_device_tree(tree)
+    assert indexed == {'/mode/vs/0': {'x': 1}, '/power/vs/0': {'y': 2}}
+    assert '/device/0' not in indexed
+
+
+def test_index_device_tree_stub_entry_becomes_empty_dict():
+    tree = [
+        {'href': '/device/0', 'rep': {}},
+        {'href': '/oven/vs/0'},   # no 'rep' key at all — a stub resource
+    ]
+    indexed = StateCache.index_device_tree(tree)
+    assert indexed == {'/oven/vs/0': {}}
+
+
+def test_index_device_tree_non_list_input_returns_empty():
+    assert StateCache.index_device_tree({'not': 'a list'}) == {}
+    assert StateCache.index_device_tree(None) == {}
+
+
+def test_apply_rep_reports_change_and_updates_cache():
+    cache = StateCache(_FakeDescriptor())
+    changed = cache.apply_rep('/mode/vs/0', {'x': 1}, source='poll')
+    assert changed is True
+    assert cache.get('/mode/vs/0') == {'x': 1}
+    unchanged = cache.apply_rep('/mode/vs/0', {'x': 1}, source='poll')
+    assert unchanged is False