diff --git a/tests/test_meshcore_integration.py b/tests/test_meshcore_integration.py
new file mode 100644
index 0000000..fad7d6b
--- /dev/null
+++ b/tests/test_meshcore_integration.py
@@ -0,0 +1,174 @@
+"""Integration tests: mock meshcore library at its boundary, test full flow."""
+
+from datetime import datetime, timezone
+from unittest.mock import patch
+
+
+class TestMessageRoundTrip:
+    """Connect → receive event → appears in message store and SSE queue."""
+
+    def test_message_stored_on_receipt(self):
+        from utils.meshcore import MeshcoreClient, MeshcoreMessage
+
+        client = MeshcoreClient()
+
+        msg = MeshcoreMessage(
+            id="t1",
+            sender_id="A",
+            recipient_id="BROADCAST",
+            text="test",
+            timestamp=datetime.now(timezone.utc),
+            hop_count=1,
+            snr=-10.0,
+            is_direct=False,
+        )
+        client.on_message(msg)
+
+        msgs = client.get_messages()
+        assert len(msgs) == 1
+        assert msgs[0]["text"] == "test"
+
+    def test_message_pushed_to_queue(self):
+        from utils.meshcore import MeshcoreClient, MeshcoreMessage
+
+        client = MeshcoreClient()
+
+        msg = MeshcoreMessage(
+            id="t2",
+            sender_id="B",
+            recipient_id="BROADCAST",
+            text="queued",
+            timestamp=datetime.now(timezone.utc),
+            hop_count=0,
+            snr=None,
+            is_direct=True,
+        )
+        client.on_message(msg)
+
+        event = client.get_queue().get_nowait()
+        assert event["type"] == "message"
+        assert event["data"]["text"] == "queued"
+
+    def test_message_history_capped_at_500(self):
+        from utils.meshcore import MeshcoreClient, MeshcoreMessage
+
+        client = MeshcoreClient()
+
+        for i in range(510):
+            client.on_message(
+                MeshcoreMessage(
+                    id=str(i),
+                    sender_id="X",
+                    recipient_id="BROADCAST",
+                    text=f"msg{i}",
+                    timestamp=datetime.now(timezone.utc),
+                    hop_count=0,
+                    snr=None,
+                    is_direct=False,
+                )
+            )
+
+        assert len(client.get_messages()) == 500
+
+
+class TestNodeAndRepeater:
+    def test_repeater_appears_in_repeaters_only(self):
+        from utils.meshcore import MeshcoreClient, MeshcoreNode
+
+        client = MeshcoreClient()
+
+        client.on_node(
+            MeshcoreNode(
+                node_id="R1",
+                name="Roof",
+                is_repeater=True,
+                lat=51.5,
+                lon=-0.1,
+                battery_pct=100,
+                last_seen=datetime.now(timezone.utc),
+                snr=-3.0,
+                hops_away=1,
+            )
+        )
+        client.on_node(
+            MeshcoreNode(
+                node_id="C1",
+                name="Client",
+                is_repeater=False,
+                lat=51.6,
+                lon=-0.2,
+                battery_pct=72,
+                last_seen=datetime.now(timezone.utc),
+                snr=-8.0,
+                hops_away=2,
+            )
+        )
+
+        assert len(client.get_repeaters()) == 1
+        assert client.get_repeaters()[0]["node_id"] == "R1"
+        assert len(client.get_nodes()) == 2
+
+
+class TestTracerouteRoundTrip:
+    def test_traceroute_pushed_to_queue(self):
+        from utils.meshcore import MeshcoreClient, MeshcoreTraceroute
+
+        client = MeshcoreClient()
+
+        tr = MeshcoreTraceroute(
+            origin_id="A",
+            destination_id="B",
+            hops=["A", "R1", "B"],
+            snr_per_hop=[-5.0, -8.0],
+            timestamp=datetime.now(timezone.utc),
+        )
+        client.on_traceroute(tr)
+
+        q = client.get_queue()
+        event = q.get_nowait()
+        assert event["type"] == "traceroute"
+        assert event["data"]["hops"] == ["A", "R1", "B"]
+
+
+class TestBLEDockerBlock:
+    def test_ble_blocked_in_docker(self, tmp_path, monkeypatch):
+        monkeypatch.setenv("INTERCEPT_DOCKER", "1")
+        from utils.meshcore import BLEConfig, MeshcoreClient
+
+        client = MeshcoreClient()
+
+        with patch("utils.meshcore_client.AsyncWorker") as MockWorker:
+            client.connect(BLEConfig())
+            MockWorker.assert_not_called()
+
+        q = client.get_queue()
+        # connect() pushes 'connecting' first, then the error — drain to the error event
+        events = []
+        while not q.empty():
+            events.append(q.get_nowait())
+        error_events = [e for e in events if e.get("data", {}).get("state") == "error"]
+        assert error_events, f"Expected an error event, got: {events}"
+        assert "Docker" in error_events[0]["data"]["message"]
+
+
+class TestConnectionStateTransitions:
+    def test_on_connected_pushes_status_event(self):
+        from utils.meshcore import ConnectionState, MeshcoreClient
+
+        client = MeshcoreClient()
+        client.on_connected(transport="serial", device="/dev/ttyUSB0")
+
+        assert client.get_state() == ConnectionState.CONNECTED
+        event = client.get_queue().get_nowait()
+        assert event["type"] == "status"
+        assert event["data"]["state"] == "connected"
+
+    def test_on_error_pushes_status_event(self):
+        from utils.meshcore import ConnectionState, MeshcoreClient
+
+        client = MeshcoreClient()
+        client.on_error("timeout")
+
+        assert client.get_state() == ConnectionState.ERROR
+        event = client.get_queue().get_nowait()
+        assert event["data"]["state"] == "error"