diff --git a/bec_widgets/widgets/plots/waveform/curve.py b/bec_widgets/widgets/plots/waveform/curve.py
index f5bd030c..6644b074 100644
--- a/bec_widgets/widgets/plots/waveform/curve.py
+++ b/bec_widgets/widgets/plots/waveform/curve.py
@@ -106,6 +106,8 @@ class Curve(BECConnector, pg.PlotDataItem):
         self.dap_params = None
         self.dap_summary = None
         self.slice_index = None
+        self._data_version = 0
+        self._last_dap_request_fingerprint: tuple | None = None
         if kwargs:
             self.set(**kwargs)
         # Activate setClipToView, to boost performance for large datasets per default
@@ -195,6 +197,17 @@ class Curve(BECConnector, pg.PlotDataItem):
         self.config.signal.dap_oversample = value
         self.parent_item.request_dap()  # do immediate request for dap update
 
+    @property
+    def data_version(self) -> int:
+        """Monotonic counter bumped on every ``setData`` call."""
+        return self._data_version
+
+    def setData(self, *args, **kwargs):
+        """Wrap ``PlotDataItem.setData`` to track how often the data changes."""
+        # getattr guards against setData being reached before __init__ sets the field.
+        self._data_version = getattr(self, "_data_version", 0) + 1
+        super().setData(*args, **kwargs)
+
     def set_data(self, x: list | np.ndarray, y: list | np.ndarray):
         """
         Set the data of the curve.
diff --git a/bec_widgets/widgets/plots/waveform/waveform.py b/bec_widgets/widgets/plots/waveform/waveform.py
index afc4398b..123c5295 100644
--- a/bec_widgets/widgets/plots/waveform/waveform.py
+++ b/bec_widgets/widgets/plots/waveform/waveform.py
@@ -1582,6 +1582,9 @@ class Waveform(PlotBase):
         if current_scan_id is None:
             return
 
+        if self.curves and not any(curve.config.source == "device" for curve in self.curves):
+            return
+
         if current_scan_id != self.scan_id:
             self.reset()
             self.new_scan.emit()
@@ -1974,6 +1977,7 @@ class Waveform(PlotBase):
     def request_dap(self, _=None):
         """Request new fit for data"""
 
+        published = False
         for dap_curve in self._dap_curves:
             parent_label = getattr(dap_curve.config, "parent_label", None)
             if not parent_label:
@@ -1999,6 +2003,15 @@ class Waveform(PlotBase):
                 x_max = None
 
             dap_parameters = getattr(dap_curve.config.signal, "dap_parameters", None)
+
+            if parent_curve.config.source != "device":
+                fingerprint = self._dap_request_fingerprint(
+                    dap_curve, parent_curve, model_name, dap_parameters
+                )
+                if fingerprint == dap_curve._last_dap_request_fingerprint:
+                    continue
+                dap_curve._last_dap_request_fingerprint = fingerprint
+
             dap_kwargs = {
                 "data_x": x_data,
                 "data_y": y_data,
@@ -2027,6 +2040,42 @@ class Waveform(PlotBase):
                 metadata={"RID": f"{self.scan_id}-{self.gui_id}"},
             )
             self.client.connector.set_and_publish(MessageEndpoints.dap_request(), msg)
+            published = True
+
+        if not published:
+            self.unblock_dap_proxy.emit()
+
+    def _dap_request_fingerprint(
+        self,
+        dap_curve: Curve,
+        parent_curve: Curve,
+        model_name: str | list[str],
+        dap_parameters: dict | list | None,
+    ) -> tuple:
+        """
+        Fingerprint of everything that determines the outcome of a DAP request for a
+        curve with a static (custom/history) parent. Two identical fingerprints mean
+        the request can be skipped. scan_id is included because it keys the request
+        RID and the response subscription, so a new scan re-issues the fit once under
+        the current subscription.
+
+        Args:
+            dap_curve(Curve): The DAP curve the request would be issued for.
+            parent_curve(Curve): The static source curve providing the fit data.
+            model_name(str | list[str]): The DAP model name(s).
+            dap_parameters(dict | list | None): Optional lmfit parameter overrides.
+
+        Returns:
+            tuple: The fingerprint.
+        """
+        return (
+            self.scan_id,
+            str(model_name),
+            dap_curve.dap_oversample,
+            dap_parameters,
+            parent_curve.data_version,
+            self.roi_region,
+        )
 
     @staticmethod
     def _normalize_dap_parameters(
diff --git a/tests/unit_tests/test_waveform.py b/tests/unit_tests/test_waveform.py
index 35aedeb4..bf50a022 100644
--- a/tests/unit_tests/test_waveform.py
+++ b/tests/unit_tests/test_waveform.py
@@ -480,6 +480,151 @@ def test_on_scan_status(qtbot, mocked_client, monkeypatch, mode, calls):
     assert async_spy.call_count == calls[1], "async_signal_update should be called exactly once"
 
 
+def test_on_scan_status_ignored_without_device_curves(qtbot, mocked_client_with_dap, monkeypatch):
+    """
+    A widget with only custom/dap curves (no live scan to follow) must not have its
+    scan_id -- and therefore its DAP request/response subscription -- reassigned by
+    unrelated scan_status messages. Otherwise an in-flight DAP request can have its
+    response dropped because the widget resubscribed to a different scan_id before
+    the response arrived.
+    """
+    wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+    x = np.linspace(-1, 1, 50)
+    y = np.sin(x)
+    wf.plot(x=x, y=y, label="custom-curve", dap="GaussianModel")
+
+    dummy_scan = create_dummy_scan_item()
+    dummy_scan.metadata["bec"]["scan_id"] = "unrelated-scan-1"
+    monkeypatch.setattr(wf.queue.scan_storage, "find_scan_by_ID", lambda scan_id: dummy_scan)
+
+    setup_dap_spy = MagicMock(wraps=wf.setup_dap_for_scan)
+    monkeypatch.setattr(wf, "setup_dap_for_scan", setup_dap_spy)
+
+    scan_id_before = wf.scan_id
+    calls_before = setup_dap_spy.call_count
+
+    wf.on_scan_status({"scan_id": "unrelated-scan-1"}, {})
+    wf.on_scan_status({"scan_id": "unrelated-scan-2"}, {})
+
+    assert wf.scan_id == scan_id_before
+    assert setup_dap_spy.call_count == calls_before
+
+
+def test_request_dap_skips_unchanged_static_parent(qtbot, mocked_client_with_dap, monkeypatch):
+    """
+    DAP curves whose parent is a static custom curve must not be resubmitted by
+    scan-driven request_dap calls when the fit inputs are unchanged. Changing the
+    custom data (or the oversample) triggers exactly one new request.
+    """
+    wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+    curve = wf.plot(x=[0, 1, 2], y=[1, 2, 3], label="custom-static", dap="GaussianModel")
+    dap_curve = wf.get_curve(f"{curve.name()}-GaussianModel")
+    assert dap_curve is not None
+
+    published = []
+    monkeypatch.setattr(
+        wf.client.connector,
+        "set_and_publish",
+        lambda topic, msg, *args, **kwargs: published.append(msg),
+    )
+
+    # The creation-time request already stored a fingerprint; identical inputs are skipped
+    wf.request_dap()
+    wf.request_dap()
+    assert len(published) == 0
+
+    # New custom data -> one new request, further identical calls skipped again
+    curve.set_data([0, 1, 2], [3, 2, 1])
+    wf.request_dap()
+    wf.request_dap()
+    assert len(published) == 1
+
+    # Oversample change requests immediately via the setter and updates the fingerprint
+    dap_curve.dap_oversample = 4
+    assert len(published) == 2
+    wf.request_dap()
+    assert len(published) == 2
+
+
+def test_request_dap_resubmits_on_roi_change_for_static_parent(
+    qtbot, mocked_client_with_dap, monkeypatch
+):
+    """
+    Changing the linear region selector changes the cropped fit inputs, so a DAP
+    curve with a static custom parent must be resubmitted even though the parent
+    data itself did not change.
+    """
+    wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+    x = np.linspace(0, 10, 50)
+    wf.plot(x=x, y=np.sin(x), label="custom-roi", dap="GaussianModel")
+
+    published = []
+    monkeypatch.setattr(
+        wf.client.connector,
+        "set_and_publish",
+        lambda topic, msg, *args, **kwargs: published.append(msg),
+    )
+
+    wf.request_dap()
+    assert len(published) == 0
+
+    wf.roi_region = (2.0, 8.0)
+    wf.request_dap()
+    assert len(published) == 1
+    assert len(published[0].content["config"]["kwargs"]["data_x"]) < len(x)
+
+    # Same region again -> no resubmission
+    wf.request_dap()
+    assert len(published) == 1
+
+    # Removing the region restores the full data set -> one resubmission
+    wf.roi_region = None
+    wf.request_dap()
+    assert len(published) == 2
+
+
+def test_request_dap_releases_proxy_when_nothing_published(
+    qtbot, mocked_client_with_dap, monkeypatch
+):
+    """
+    When request_dap skips every DAP curve (static parents, unchanged inputs), no
+    dap_response will arrive to unblock proxy_dap_request. The proxy must be
+    released immediately, otherwise the next trigger (e.g. an ROI change) would be
+    delayed by the proxy timeout.
+    """
+    wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+    wf.plot(x=[0, 1, 2], y=[1, 2, 3], label="custom-blocked", dap="GaussianModel")
+
+    monkeypatch.setattr(
+        wf.client.connector, "set_and_publish", lambda topic, msg, *args, **kwargs: None
+    )
+
+    wf.request_dap_update.emit()
+    assert wf.proxy_dap_request.blocked is True
+    # The proxy timeout is 10 s; the no-publish call must release it much earlier
+    qtbot.waitUntil(lambda: wf.proxy_dap_request.blocked is False, timeout=3000)
+
+
+def test_request_dap_always_resubmits_device_parent(qtbot, mocked_client_with_dap, monkeypatch):
+    """
+    DAP curves attached to device curves keep the resubmit-on-every-update behavior,
+    since their parent data changes as the scan progresses.
+    """
+    wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+    wf.plot(arg1="bpm4i", label="bpm4i-bpm4i", dap="GaussianModel")
+
+    published = []
+    monkeypatch.setattr(
+        wf.client.connector,
+        "set_and_publish",
+        lambda topic, msg, *args, **kwargs: published.append(msg),
+    )
+
+    wf.request_dap()
+    wf.request_dap()
+    assert len(published) == 2
+
+
 def test_add_dap_curve(qtbot, mocked_client_with_dap, monkeypatch):
     """
     Test add_dap_curve creates a new DAP curve from an existing device curve
@@ -792,6 +937,15 @@ def test_normalize_dap_parameters_composite_dict():
 
 def test_request_dap_includes_normalized_parameters(qtbot, mocked_client_with_dap, monkeypatch):
     wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+
+    captured = {}
+
+    def capture(topic, msg, *args, **kwargs):  # noqa: ARG001
+        captured["topic"] = topic
+        captured["msg"] = msg
+
+    monkeypatch.setattr(wf.client.connector, "set_and_publish", capture)
+
     curve = wf.plot(
         x=[0, 1, 2],
         y=[1, 2, 3],
@@ -801,17 +955,9 @@ def test_request_dap_includes_normalized_parameters(qtbot, mocked_client_with_da
     )
     dap_curve = wf.get_curve(f"{curve.name()}-GaussianModel")
     assert dap_curve is not None
+    # The oversample setter issues a fresh DAP request with the new value
     dap_curve.dap_oversample = 3
 
-    captured = {}
-
-    def capture(topic, msg, *args, **kwargs):  # noqa: ARG001
-        captured["topic"] = topic
-        captured["msg"] = msg
-
-    monkeypatch.setattr(wf.client.connector, "set_and_publish", capture)
-    wf.request_dap()
-
     msg = captured["msg"]
     dap_kwargs = msg.content["config"]["kwargs"]
     assert dap_kwargs["oversample"] == 3
@@ -822,6 +968,15 @@ def test_request_dap_includes_normalized_parameters(qtbot, mocked_client_with_da
 
 def test_request_dap_includes_composite_parameters_list(qtbot, mocked_client_with_dap, monkeypatch):
     wf = create_widget(qtbot, Waveform, client=mocked_client_with_dap)
+
+    captured = {}
+
+    def capture(topic, msg, *args, **kwargs):  # noqa: ARG001
+        captured["topic"] = topic
+        captured["msg"] = msg
+
+    monkeypatch.setattr(wf.client.connector, "set_and_publish", capture)
+
     curve = wf.plot(
         x=[0, 1, 2],
         y=[1, 2, 3],
@@ -832,15 +987,6 @@ def test_request_dap_includes_composite_parameters_list(qtbot, mocked_client_wit
     dap_curve = wf.get_curve(f"{curve.name()}-GaussianModel+GaussianModel")
     assert dap_curve is not None
 
-    captured = {}
-
-    def capture(topic, msg, *args, **kwargs):  # noqa: ARG001
-        captured["topic"] = topic
-        captured["msg"] = msg
-
-    monkeypatch.setattr(wf.client.connector, "set_and_publish", capture)
-    wf.request_dap()
-
     msg = captured["msg"]
     dap_kwargs = msg.content["config"]["kwargs"]
     assert dap_kwargs["parameters"] == [