diff --git a/custom_components/houseplan/trails.py b/custom_components/houseplan/trails.py
index 699933d..ea07250 100755
--- a/custom_components/houseplan/trails.py
+++ b/custom_components/houseplan/trails.py
@@ -9,6 +9,7 @@ want to see where the cleanup has already been).
 """
 from __future__ import annotations
 
+import asyncio
 import time
 from typing import Any
 
@@ -28,6 +29,28 @@ FIRE_THROTTLE_S = 2.0     # event-bus updates for live cards
 MOVING_STATES = {"cleaning", "returning", "on"}
 
 
+def resolve_map_id(src_attrs: Any, vac_attrs: Any) -> str:
+    """Map-id normalisation contract, shared with the frontend.
+
+    Mirrors src/vacuum.ts vacMapIdFromAttrs (source attrs, `??`-chain) plus the
+    card's _vacMapId fallback to the vacuum entity's selected_map. The FIRST
+    value that is not None wins — truthiness is wrong here: a zero-based
+    `map_index: 0` is a valid first map and an empty string is still an id.
+    The old `or`-chain dropped the zero, so the server stored trails under a
+    key the renderer never looked up (HP-1540-02).
+    """
+    for v in (
+        src_attrs.get("map_name"),
+        src_attrs.get("current_map"),
+        src_attrs.get("map_index"),
+        src_attrs.get("selected_map"),
+        vac_attrs.get("selected_map"),
+    ):
+        if v is not None:
+            return str(v)
+    return "default"
+
+
 class TrailBook:
     """Pure run bookkeeping: {marker: {current: run, previous: run}}.
 
@@ -76,44 +99,69 @@ class TrailRecorder:
         self.rt = rt
         self.store = Store(hass, 1, f"{DOMAIN}.trails")
         self.book = TrailBook()
-        self.pairs: dict[str, tuple[str, str]] = {}  # source → (marker, vacuum)
+        # HP-1540-03: one source may feed SEVERAL markers — the same robot
+        # placed on two floors is the documented multi-floor case, and a plain
+        # source → (marker, vacuum) dict silently kept only the last one
+        self.pairs: dict[str, list[tuple[str, str]]] = {}  # source → [(marker, vacuum), …]
         self._unsub_track = None
         self._unsub_save = None
         self._last_fire = 0.0
+        # HP-1540-05: config/set fires refresh as a detached task; two of them
+        # interleaving across the awaited load both subscribed and the loser's
+        # unsub handle was overwritten — a leak until HA restart
+        self._refresh_lock = asyncio.Lock()
+        self._closed = False
 
     async def async_setup(self) -> None:
         self.book = TrailBook(await self.store.async_load() or {})
         await self.async_refresh()
 
     async def async_refresh(self) -> None:
-        """(Re)subscribe after any config change — markers may come and go."""
-        if self._unsub_track:
-            self._unsub_track()
-            self._unsub_track = None
-        stored = await self.rt.config_store.async_load() or {}
-        cfg = stored.get("config") or {}
-        self.pairs = {}
-        for m in cfg.get("markers") or []:
-            v = m.get("vacuum") or {}
-            src = v.get("source")
-            if not src or v.get("live") is False:
-                continue
-            vac = self._vacuum_entity(m)
-            if vac:
-                self.pairs[src] = (str(m.get("id")), vac)
-        ents = set(self.pairs) | {vac for _, vac in self.pairs.values()}
-        _LOGGER.info("Trail recorder: tracking %s", sorted(ents))
-        if ents:
-            self._unsub_track = async_track_state_change_event(
-                self.hass, sorted(ents), self._on_state
-            )
-        # A run already in progress (HA restarted mid-cleanup, or the user just
-        # finished calibrating) must start recording NOW, not at the next
-        # state change — otherwise the first seconds of the path are lost.
-        for src in self.pairs:
-            self._sample(src, time.time())
+        """(Re)subscribe after any config change — markers may come and go.
+
+        Serialised (HP-1540-05): the lock makes unsubscribe-then-resubscribe
+        atomic across the awaited config load, so overlapping refresh tasks can
+        no longer both subscribe and strand one callback forever. The _closed
+        check covers teardown() racing a refresh that is parked on its await.
+        """
+        async with self._refresh_lock:
+            stored = await self.rt.config_store.async_load() or {}
+            if self._closed:
+                return
+            cfg = stored.get("config") or {}
+            pairs: dict[str, list[tuple[str, str]]] = {}
+            for m in cfg.get("markers") or []:
+                v = m.get("vacuum") or {}
+                src = v.get("source")
+                if not src or v.get("live") is False:
+                    continue
+                vac = self._vacuum_entity(m)
+                if vac:
+                    # HP-1540-03: append, never overwrite — every floor's
+                    # marker records its own copy of the run
+                    pairs.setdefault(src, []).append((str(m.get("id")), vac))
+            self.pairs = pairs
+            if self._unsub_track:
+                self._unsub_track()
+                self._unsub_track = None
+            # deduplicated: two markers of one robot share source AND vacuum
+            ents = set(self.pairs) | {vac for ps in self.pairs.values() for _, vac in ps}
+            _LOGGER.info("Trail recorder: tracking %s", sorted(ents))
+            if ents:
+                self._unsub_track = async_track_state_change_event(
+                    self.hass, sorted(ents), self._on_state
+                )
+            # A run already in progress (HA restarted mid-cleanup, or the user
+            # just finished calibrating) must start recording NOW, not at the
+            # next state change — otherwise the first seconds of the path are
+            # lost.
+            for src in self.pairs:
+                self._sample(src, time.time())
 
     def teardown(self) -> None:
+        # HP-1540-05: flag FIRST — a refresh parked on its awaited load must
+        # not re-subscribe after this cleanup has already run
+        self._closed = True
         if self._unsub_track:
             self._unsub_track()
             self._unsub_track = None
@@ -133,51 +181,49 @@ class TrailRecorder:
         return None
 
     def _sample(self, src: str, now: float) -> bool:
-        """Record one point (or end the run) for a single source entity."""
-        pair = self.pairs.get(src)
-        if not pair:
-            return False
-        marker, vac = pair
-        st_vac = self.hass.states.get(vac)
-        # "no state yet" is NOT "stopped": during HA boot the vacuum reads
-        # unavailable and ending the run here would split one cleanup into
-        # current+previous on every restart (observed live: 21 points became
-        # previous, the same run restarted at 5)
-        if not st_vac or st_vac.state in ("unavailable", "unknown"):
-            return False
-        if st_vac.state not in MOVING_STATES:
-            return self.book.end_run(marker, now)
-        st_src = self.hass.states.get(src)
-        attrs = st_src.attributes if st_src else {}
-        raw = attrs.get("vacuum_position") or attrs.get("robot_position")
-        # Server-side these attributes are often OBJECTS (Tasshack keeps a
-        # Point dataclass in memory — it only becomes a dict when serialised
-        # to the frontend). Caught live on the owner's X50: the recorder saw
-        # every state change and rejected every single one.
-        if isinstance(raw, dict):
-            px, py = raw.get("x"), raw.get("y")
-        else:
-            px, py = getattr(raw, "x", None), getattr(raw, "y", None)
-        try:
-            x, y = float(px), float(py)  # type: ignore[arg-type]
-        except (TypeError, ValueError):
-            return False
-        map_id = str(
-            attrs.get("map_name")
-            or attrs.get("current_map")
-            or attrs.get("map_index")
-            or st_vac.attributes.get("selected_map")
-            or "default"
-        )
-        return self.book.on_point(marker, map_id, x, y, now)
+        """Record one point (or end the run) for EVERY marker fed by src.
+
+        HP-1540-03: the same source serves one marker per floor — all of them
+        must receive the point, not just whichever survived the dict.
+        """
+        changed = False
+        for marker, vac in self.pairs.get(src) or ():
+            st_vac = self.hass.states.get(vac)
+            # "no state yet" is NOT "stopped": during HA boot the vacuum reads
+            # unavailable and ending the run here would split one cleanup into
+            # current+previous on every restart (observed live: 21 points
+            # became previous, the same run restarted at 5)
+            if not st_vac or st_vac.state in ("unavailable", "unknown"):
+                continue
+            if st_vac.state not in MOVING_STATES:
+                changed |= self.book.end_run(marker, now)
+                continue
+            st_src = self.hass.states.get(src)
+            attrs = st_src.attributes if st_src else {}
+            raw = attrs.get("vacuum_position") or attrs.get("robot_position")
+            # Server-side these attributes are often OBJECTS (Tasshack keeps a
+            # Point dataclass in memory — it only becomes a dict when
+            # serialised to the frontend). Caught live on the owner's X50: the
+            # recorder saw every state change and rejected every single one.
+            if isinstance(raw, dict):
+                px, py = raw.get("x"), raw.get("y")
+            else:
+                px, py = getattr(raw, "x", None), getattr(raw, "y", None)
+            try:
+                x, y = float(px), float(py)  # type: ignore[arg-type]
+            except (TypeError, ValueError):
+                continue
+            map_id = resolve_map_id(attrs, st_vac.attributes)
+            changed |= self.book.on_point(marker, map_id, x, y, now)
+        return changed
 
     @callback
     def _on_state(self, event: Any) -> None:
         eid = event.data.get("entity_id")
         now = time.time()
         changed = False
-        for src, (_marker, vac) in self.pairs.items():
-            if eid in (src, vac):
+        for src, pair_list in self.pairs.items():
+            if eid == src or any(eid == vac for _, vac in pair_list):
                 changed |= self._sample(src, now)
         if changed:
             self._schedule_save()
diff --git a/tests_backend/test_trail_recorder.py b/tests_backend/test_trail_recorder.py
index 1edc421..2e9446c 100644
--- a/tests_backend/test_trail_recorder.py
+++ b/tests_backend/test_trail_recorder.py
@@ -85,7 +85,7 @@ def _rec():
     }
     hass = Hass(states)
     rec = trails.TrailRecorder(hass, None)
-    rec.pairs = {"camera.map": ("m1", "vacuum.x50")}
+    rec.pairs = {"camera.map": [("m1", "vacuum.x50")]}
     return rec, hass, states
 
 
@@ -152,3 +152,151 @@ def test_unavailable_vacuum_is_no_verdict():
     del states["vacuum.x50"]
     assert not rec._sample("camera.map", 3.0)
     assert rec.book.data["m1"]["current"]["ended"] is None
+
+
+# ---------------- v1.54.0 audit regressions ----------------
+
+
+def test_map_index_zero_matches_frontend_contract():
+    # HP-1540-02: `map_index: 0` is a VALID first map. The old or-chain
+    # dropped it and fell through to selected_map — the server stored the
+    # run under a key the renderer never looked up.
+    rec, _hass, states = _rec()
+    states["camera.map"] = S("idle", {"vacuum_position": {"x": 10, "y": 20}, "map_index": 0})
+    assert rec._sample("camera.map", 1.0)
+    assert rec.book.data["m1"]["current"]["map_id"] == "0"
+
+
+def test_map_id_contract_first_not_none_wins():
+    # HP-1540-02: the shared contract — first NOT-None value, stringified
+    cases = [
+        ({"map_index": 0}, {"selected_map": "Floor"}, "0"),
+        ({"map_index": "0"}, {}, "0"),
+        ({"map_name": ""}, {"selected_map": "Floor"}, ""),
+        ({"map_name": "A", "map_index": 0}, {}, "A"),
+        ({"current_map": 2}, {}, "2"),
+        ({"selected_map": "Src"}, {"selected_map": "Vac"}, "Src"),
+        ({}, {"selected_map": "Vac"}, "Vac"),
+        ({}, {}, "default"),
+    ]
+    for src_attrs, vac_attrs, want in cases:
+        assert trails.resolve_map_id(src_attrs, vac_attrs) == want, (src_attrs, vac_attrs)
+
+
+def test_one_source_two_floor_markers_both_record():
+    # HP-1540-03: the multi-floor case — the same robot placed on two floors.
+    # Both markers must receive the server-side run, on every map.
+    states = {
+        "vacuum.x50": S("cleaning", {}),
+        "camera.map": S("idle", {"vacuum_position": {"x": 100, "y": 200}, "map_index": 0}),
+    }
+    hass = Hass(states)
+    rec = trails.TrailRecorder(hass, None)
+    rec.pairs = {"camera.map": [("m_floor1", "vacuum.x50"), ("m_floor2", "vacuum.x50")]}
+    rec._on_state(E("camera.map"))
+    # the robot moves to the second map: BOTH books rotate to the new run
+    states["camera.map"] = S("idle", {"vacuum_position": {"x": 300, "y": 400}, "map_index": 1})
+    rec._on_state(E("camera.map"))
+    for marker in ("m_floor1", "m_floor2"):
+        book = rec.book.data[marker]
+        assert book["previous"]["map_id"] == "0", marker
+        assert book["previous"]["points"] == [[100.0, 200.0]], marker
+        assert book["current"]["map_id"] == "1", marker
+        assert book["current"]["points"] == [[300.0, 400.0]], marker
+
+
+def test_refresh_builds_pair_lists_and_dedups_subscription():
+    # HP-1540-03: two markers over one source/vacuum → one entity set, both pairs
+    import asyncio
+
+    tracked = []
+
+    def track(hass, ents, cb):
+        tracked.append(list(ents))
+        return lambda: None
+
+    old_track = trails.async_track_state_change_event
+    trails.async_track_state_change_event = track
+    try:
+        cfgm = [
+            {"id": "m_f1", "binding": "entity:vacuum.x50", "vacuum": {"source": "camera.map"}},
+            {"id": "m_f2", "binding": "entity:vacuum.x50", "vacuum": {"source": "camera.map"}},
+        ]
+
+        class CS:
+            async def async_load(self):
+                return {"config": {"markers": cfgm}}
+
+        class RT:
+            config_store = CS()
+
+        hass = Hass({
+            "vacuum.x50": S("docked", {}),
+            "camera.map": S("idle", {}),
+        })
+        rec = trails.TrailRecorder(hass, RT())
+        asyncio.run(rec.async_refresh())
+        assert rec.pairs == {"camera.map": [("m_f1", "vacuum.x50"), ("m_f2", "vacuum.x50")]}
+        assert tracked == [["camera.map", "vacuum.x50"]]
+    finally:
+        trails.async_track_state_change_event = old_track
+
+
+def test_overlapping_refreshes_leave_one_subscription_teardown_zero():
+    # HP-1540-05: two config/set refreshes racing across the awaited load used
+    # to BOTH subscribe; teardown removed only the last handle and the other
+    # callback leaked until HA restart.
+    import asyncio
+
+    active = []
+    seq = {"n": 0}
+
+    def track(hass, ents, cb):
+        seq["n"] += 1
+        hid = seq["n"]
+        active.append(hid)
+        return lambda: active.remove(hid)
+
+    old_track = trails.async_track_state_change_event
+    trails.async_track_state_change_event = track
+    try:
+        gate = asyncio.Event()
+
+        class CS:
+            async def async_load(self):
+                await gate.wait()
+                return {"config": {"markers": [
+                    {"id": "m1", "binding": "entity:vacuum.x50", "vacuum": {"source": "camera.map"}},
+                ]}}
+
+        class RT:
+            config_store = CS()
+
+        hass = Hass({
+            "vacuum.x50": S("docked", {}),
+            "camera.map": S("idle", {}),
+        })
+
+        async def scenario():
+            rec = trails.TrailRecorder(hass, RT())
+            t1 = asyncio.ensure_future(rec.async_refresh())
+            t2 = asyncio.ensure_future(rec.async_refresh())
+            for _ in range(3):  # both tasks are launched; one parks on the gate
+                await asyncio.sleep(0)
+            gate.set()
+            await t1
+            await t2
+            assert len(active) == 1, f"exactly one live subscription, got {active}"
+            # teardown during an in-flight refresh must also end with zero
+            gate.clear()
+            t3 = asyncio.ensure_future(rec.async_refresh())
+            for _ in range(3):
+                await asyncio.sleep(0)
+            rec.teardown()
+            gate.set()
+            await t3
+            assert active == [], f"teardown must leave zero subscriptions, got {active}"
+
+        asyncio.run(scenario())
+    finally:
+        trails.async_track_state_change_event = old_track