Unify Signals/Channels around auto-naming, plot-by-channel, and shared vars

Devices: auto-name from OS-reported port description (Device Manager /
udev string) instead of a generic label; default Serial #Channels 1;
consistent simulate-mode checkbox across backends; inline device rename.

Channels: calibration/filters move out of Signals into a Channel
"Operation" (adds Scale/Offset alongside the existing math kinds);
single-physical-source Channels get an embedded Filters block; new
Channels auto-name/auto-ID from their source and reject duplicate
names/IDs on apply; "Create Channel" button on each Signal row; renamed
"Sources" -> "Signals" in the Channels UI; Signals' READ/WRITE dir badge
(was silently-broken IN/OUT) now reflects the real writable flag.

Plot: default layout is one pane per Channel (not per device, not raw
Signals) titled by channel name; "+ Add Channel" is a checkbox dialog
instead of an inline dropdown; traces get up/down reorder; live unit
changes (e.g. a Mark-10 gauge switching lb/kgF/N/ozF) propagate to an
open pane's axis label without clobbering a manually-typed one.

Control Panel: hardware assignment now picks from the same writable-
Signals list instead of a separate device/channel combo with a
hardcoded Arduino pin list; stale visual indicator when a control's
target device/channel disconnects or disappears; documented the `vars`
bridge (Control Panel On Action Script <-> Channel scripts) in both
directions' help text and script templates.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 237 insertions, 68 deletions

diff --git a/ui/windows/channels_window.py b/ui/windows/channels_window.py
index 38d477b..2388b83 100644
--- a/ui/windows/channels_window.py
+++ b/ui/windows/channels_window.py
@@ -215,7 +215,8 @@ class ChannelPipelineBlock(QFrame):
     removed = pyqtSignal(object)
 
     def __init__(self, dev_id: str, ch_id: str, ch_name: str, unit: str,
-                 processor: SignalProcessor):
+                 processor: SignalProcessor, show_calibration: bool = True,
+                 show_header: bool = True):
         super().__init__()
         self.dev_id    = dev_id
         self.ch_id     = ch_id
@@ -224,6 +225,8 @@ class ChannelPipelineBlock(QFrame):
         self._cal_rows:    List[FilterRow] = []
         self._cur_pipeline: Optional[ChannelPipeline] = None
         self._expanded = False
+        self._show_calibration = show_calibration
+        self._show_header      = show_header
         self.setObjectName("plotBlock")
         self._build(ch_name, unit)
         self._load()
@@ -233,26 +236,28 @@ class ChannelPipelineBlock(QFrame):
         self._unit = unit
         outer = QVBoxLayout(self); outer.setContentsMargins(0, 0, 0, 0); outer.setSpacing(0)
 
-        # Header
-        hdr = QWidget(); hdr.setObjectName("plotBlockHeader"); hdr.setFixedHeight(32)
-        hl  = QHBoxLayout(hdr); hl.setContentsMargins(8, 0, 6, 0)
-        title = f"{ch_name}  ({self.dev_id}/{self.ch_id})"
-        if unit:
-            title += f"  [{unit}]"
-        self._title_lbl = QLabel(title); self._title_lbl.setObjectName("traceSource")
-        hl.addWidget(self._title_lbl, 1)
-
-        rm_btn = QToolButton(); rm_btn.setText("✕")
-        rm_btn.setObjectName("traceRemoveBtn"); rm_btn.setFixedSize(22, 22)
-        rm_btn.clicked.connect(lambda: self.removed.emit(self))
-        hl.addWidget(rm_btn)
-
-        self._toggle_btn = QToolButton(); self._toggle_btn.setText("▶")
-        self._toggle_btn.setObjectName("traceRemoveBtn"); self._toggle_btn.setFixedSize(22, 22)
-        self._toggle_btn.clicked.connect(self._toggle)
-        hl.addWidget(self._toggle_btn)
-        outer.addWidget(hdr)
-        hdr.mousePressEvent = lambda e: self._toggle()
+        # Header (omitted when embedded in another block, e.g. DerivedBlock's
+        # Filters section — the parent already provides a header/toggle)
+        if self._show_header:
+            hdr = QWidget(); hdr.setObjectName("plotBlockHeader"); hdr.setFixedHeight(32)
+            hl  = QHBoxLayout(hdr); hl.setContentsMargins(8, 0, 6, 0)
+            title = f"{ch_name}  ({self.dev_id}/{self.ch_id})"
+            if unit:
+                title += f"  [{unit}]"
+            self._title_lbl = QLabel(title); self._title_lbl.setObjectName("traceSource")
+            hl.addWidget(self._title_lbl, 1)
+
+            rm_btn = QToolButton(); rm_btn.setText("✕")
+            rm_btn.setObjectName("traceRemoveBtn"); rm_btn.setFixedSize(22, 22)
+            rm_btn.clicked.connect(lambda: self.removed.emit(self))
+            hl.addWidget(rm_btn)
+
+            self._toggle_btn = QToolButton(); self._toggle_btn.setText("▶")
+            self._toggle_btn.setObjectName("traceRemoveBtn"); self._toggle_btn.setFixedSize(22, 22)
+            self._toggle_btn.clicked.connect(self._toggle)
+            hl.addWidget(self._toggle_btn)
+            outer.addWidget(hdr)
+            hdr.mousePressEvent = lambda e: self._toggle()
 
         # Body
         self._body = QWidget(); self._body.setObjectName("plotBlockSettings")
@@ -281,21 +286,25 @@ class ChannelPipelineBlock(QFrame):
         div.setObjectName("devWindowDivider")
         bl.addWidget(div)
 
-        # ── Calibration section ───────────────────────────────────────────────
-        cal_lbl = QLabel("Calibration"); cal_lbl.setObjectName("pwmLabel")
-        bl.addWidget(cal_lbl)
-
+        # ── Calibration section — hidden when embedded (calibration is now
+        #    configured as a Channel "Scale/Offset" Operation instead), but the
+        #    widgets still exist so a legacy scale_offset filter already saved
+        #    on this pipeline (from an older profile) is preserved by _push()
+        #    rather than silently dropped the next time a filter is edited.
         self._cal_area = QWidget()
         self._cal_lay  = QVBoxLayout(self._cal_area)
         self._cal_lay.setContentsMargins(0, 0, 0, 0); self._cal_lay.setSpacing(3)
-        bl.addWidget(self._cal_area)
-
-        cal_add_bar = QHBoxLayout()
-        cal_add_btn = QPushButton("＋ Add Calibration"); cal_add_btn.setObjectName("addTraceBtn")
-        cal_add_btn.clicked.connect(self._add_calibrate)
-        cal_add_bar.addWidget(cal_add_btn)
-        cal_add_bar.addStretch()
-        bl.addLayout(cal_add_bar)
+        if self._show_calibration:
+            cal_lbl = QLabel("Calibration"); cal_lbl.setObjectName("pwmLabel")
+            bl.addWidget(cal_lbl)
+            bl.addWidget(self._cal_area)
+
+            cal_add_bar = QHBoxLayout()
+            cal_add_btn = QPushButton("＋ Add Calibration"); cal_add_btn.setObjectName("addTraceBtn")
+            cal_add_btn.clicked.connect(self._add_calibrate)
+            cal_add_bar.addWidget(cal_add_btn)
+            cal_add_bar.addStretch()
+            bl.addLayout(cal_add_bar)
 
         ap_row = QHBoxLayout(); ap_row.addStretch()
         ap_btn = QPushButton("✓  Apply"); ap_btn.setObjectName("applyButton")
@@ -304,9 +313,12 @@ class ChannelPipelineBlock(QFrame):
         bl.addLayout(ap_row)
 
         outer.addWidget(self._body)
-        self._body.setVisible(False)
+        self._body.setVisible(self._show_header is False)
+        self._expanded = not self._show_header
 
     def _refresh_title(self):
+        if not self._show_header:
+            return
         title = f"{self._ch_name}  ({self.dev_id}/{self.ch_id})"
         if self._unit:
             title += f"  [{self._unit}]"
@@ -447,7 +459,7 @@ class PipelineTab(QWidget):
         vb_lay.addWidget(vb_lbl)
         self._src_cb = _channel_combo(self.registry, self.processor, include_derived=True)
         self._src_cb.setObjectName("channelPickerCb")
-        self._src_cb.insertItem(0, "Source: none (empty channel)", userData=None)
+        self._src_cb.insertItem(0, "Signal: none (empty channel)", userData=None)
         self._src_cb.setCurrentIndex(0)
         vb_lay.addWidget(self._src_cb, 1)
         add_virt = QPushButton("＋ Add Channel"); add_virt.setObjectName("addTraceBtn")
@@ -521,6 +533,7 @@ class PipelineTab(QWidget):
             block = self._blocks.get(key)
             if block:
                 self._on_remove_block(block)
+        self._refresh_src_cb()
 
     def on_device_reconfigured(self, dev_id: str):
         dev = self.registry.get_instance(dev_id)
@@ -534,9 +547,10 @@ class PipelineTab(QWidget):
             block = self._blocks.get(key)
             if block:
                 self._on_remove_block(block)
+        self._refresh_src_cb()
 
     def on_device_added(self):
-        pass
+        self._refresh_src_cb()
 
     def on_channel_name_changed(self, dev_id: str, ch_id: str, ch_name: str):
         key = (dev_id, ch_id)
@@ -548,12 +562,42 @@ class PipelineTab(QWidget):
                 ch = dev.get_channel(ch_id)
                 if ch and ch.enabled:
                     self._add_block(dev_id, ch_id, ch_name, ch.unit)
+        self._refresh_src_cb()
 
     def on_channel_unit_changed(self, dev_id: str, ch_id: str, unit: str):
         key = (dev_id, ch_id)
         if key in self._blocks:
             self._blocks[key].update_unit(unit)
 
+    def _refresh_src_cb(self):
+        """Rebuild the 'Source: …' picker at the top of the Channels pane —
+        it's a persistent combo (not a dialog), so it must be kept in sync
+        whenever devices/channels are added, removed, or renamed, not just
+        built once at construction time."""
+        current = self._src_cb.currentData()
+        self._src_cb.blockSignals(True)
+        self._src_cb.clear()
+        self._src_cb.insertItem(0, "Signal: none (empty channel)", userData=None)
+        for dev in self.registry.all_instances():
+            for ch in dev.info.channels:
+                if not ch.enabled:
+                    continue
+                label = f"{ch.name}  ({dev.info.device_id}/{ch.channel_id})"
+                self._src_cb.addItem(label, userData=(dev.info.device_id, ch.channel_id))
+        for dc in self.processor.get_derived():
+            label = f"[derived] {dc.channel_id}  ({dc.name})"
+            self._src_cb.addItem(label, userData=("derived", dc.channel_id))
+        if current:
+            for i in range(self._src_cb.count()):
+                if self._src_cb.itemData(i) == current:
+                    self._src_cb.setCurrentIndex(i)
+                    break
+            else:
+                self._src_cb.setCurrentIndex(0)
+        else:
+            self._src_cb.setCurrentIndex(0)
+        self._src_cb.blockSignals(False)
+
     def _on_add_channel(self):
         dlg = ChannelPickerDialog(self.registry, self._shown, self)
         if dlg.exec() != QDialog.DialogCode.Accepted:
@@ -579,14 +623,21 @@ class PipelineTab(QWidget):
     def _add_virtual(self):
         color = _DERIVED_COLORS[self._color_idx % len(_DERIVED_COLORS)]
         self._color_idx += 1
-        n  = len(self._derived_blocks) + 1
-        dc = DerivedChannel(channel_id=f"CH_{n}", name=f"Channel {n}",
+        existing_names = {d.name for d in self.processor.get_derived()}
+        existing_ids   = {d.channel_id for d in self.processor.get_derived()}
+        # Pre-seed the source picked in the bar above, if any — otherwise the
+        # channel is created empty and signals can be added manually.
+        src = self._src_cb.currentData()
+        if src:
+            src_name = _channel_display_name(self.registry, self.processor, src[0], src[1])
+        else:
+            src_name = f"Channel {len(self._derived_blocks) + 1}"
+        name = _dedupe_name(src_name, existing_names)
+        channel_id = _slug_id(name, existing_ids)
+        dc = DerivedChannel(channel_id=channel_id, name=name,
                             kind="expression", color=color)
         blk = self._make_derived_block(dc)
         self._virt_inner.insertWidget(self._virt_inner.count() - 1, blk)
-        # Pre-seed the source picked in the bar above, if any — otherwise the
-        # channel is created empty and sources can be added manually.
-        src = self._src_cb.currentData()
         if src:
             blk._add_src(src)
 
@@ -615,45 +666,85 @@ class PipelineTab(QWidget):
             self._virt_inner.insertWidget(self._virt_inner.count() - 1, blk)
 
         self._color_idx = len(self._derived_blocks)
+        self._refresh_src_cb()
 
 
 # ══════════════════════════════════════════════════════════════════════════════
 #  Derived editor for one DerivedChannel
 # ══════════════════════════════════════════════════════════════════════════════
 
-_BUILTIN   = ["none", "derivative", "second_derivative", "power", "rms", "difference", "sum"]
+_BUILTIN   = ["none", "scale_offset", "derivative", "second_derivative", "power", "rms", "difference", "sum"]
 _SCRIPT    = ["expression", "function", "custom_script"]
 _ALL_KINDS = _BUILTIN + _SCRIPT
 
 _KIND_DISPLAY = {k: k.replace("_", " ").title() for k in _ALL_KINDS}
 _KIND_DISPLAY["none"] = "None"
+_KIND_DISPLAY["scale_offset"] = "Scale/Offset (Calibration)"
 
 _KIND_HELP = {
-    "none":              "Pass source through unchanged",
-    "derivative":        "Backward difference dy/dt from 1 source",
-    "second_derivative": "Second derivative d²y/dt² from 1 source",
-    "power":        "V × I  from 2 sources (voltage, current)",
-    "rms":          "Rolling RMS from 1 source  (set window below)",
-    "difference":   "source[0] − source[1]  from 2 sources",
-    "sum":          "Σ all source values",
+    "none":              "Pass signal through unchanged",
+    "scale_offset":      "Linear calibration from 1 signal: result = value × scale + offset",
+    "derivative":        "Backward difference dy/dt from 1 signal",
+    "second_derivative": "Second derivative d²y/dt² from 1 signal",
+    "power":        "V × I  from 2 signals (voltage, current)",
+    "rms":          "Rolling RMS from 1 signal  (set window below)",
+    "difference":   "signal[0] − signal[1]  from 2 signals",
+    "sum":          "Σ all signal values",
     "expression":   (
         "Single-line Python expression.\n"
         "Available: x[0]…  or use signal names directly (e.g. A0, encoder_0)\n"
         "          t = elapsed time (s),  math,  vars,  state\n"
-        "Example:  A0 * 3.14159 / 180"
+        "Example:  A0 * 3.14159 / 180\n"
+        "Tip: vars is shared with Control Panel 'On Action Script' — a button\n"
+        "     can set vars['specimen_length'] = value; read it here as\n"
+        "     vars.get('specimen_length', 1.0)."
     ),
     "function":     (
         "Multi-line function body — auto-wrapped as def compute(x, t):\n"
         "Available globals: x, signal names, t, math, vars, state\n"
-        "Example:\n    offset = vars.get('zero', 0)\n    return x[0] - offset"
+        "Example:\n    offset = vars.get('zero', 0)\n    return x[0] - offset\n"
+        "Tip: vars is shared with Control Panel 'On Action Script' — a 'Zero'\n"
+        "     button can set vars['zero'] = value while this reads it back."
     ),
     "custom_script": (
         "Multi-line Python block.  Assign computed value to result.\n"
-        "Available: x, signal names, t, math, vars, state"
+        "Available: x, signal names, t, math, vars, state\n"
+        "Tip: vars is shared with Control Panel 'On Action Script' — a button\n"
+        "     can set vars['key'] = value; read it here as vars.get('key', default)."
     ),
 }
 
 
+def _slug_id(name: str, existing: Set[str]) -> str:
+    """Short-hand channel_id derived from a display name, deduplicated against
+    existing derived channel IDs so a new Channel never silently overwrites
+    (goes stale on top of) an existing one."""
+    words = re.findall(r"[A-Za-z0-9]+", name)
+    if not words:
+        base = "CH"
+    elif len(words) == 1:
+        base = words[0][:4].upper()
+    else:
+        base = "".join(w[0] for w in words[:4]).upper()
+    slug = base
+    i = 2
+    while slug in existing:
+        slug = f"{base}_{i}"
+        i += 1
+    return slug
+
+
+def _dedupe_name(name: str, existing: Set[str]) -> str:
+    """Two channels must never share a display name — append ' (2)', ' (3)'...
+    until unique."""
+    if name not in existing:
+        return name
+    i = 2
+    while f"{name} ({i})" in existing:
+        i += 1
+    return f"{name} ({i})"
+
+
 def _sub_xrefs(code: str, names: list) -> str:
     """Replace x[0], x[1], ... with named source vars where index is in range."""
     def repl(m):
@@ -712,6 +803,22 @@ class DerivedBlock(QFrame):
         meta.addWidget(self._unit); meta.addStretch()
         bl.addLayout(meta)
 
+        # Sources — include derived channels as valid sources
+        src_grp = QGroupBox("Signals"); src_grp.setObjectName("cfgGlobalBar")
+        src_lay = QVBoxLayout(src_grp); src_lay.setContentsMargins(6, 4, 6, 4); src_lay.setSpacing(3)
+        self._src_cont = QWidget(); self._src_vlay = QVBoxLayout(self._src_cont)
+        self._src_vlay.setContentsMargins(0, 0, 0, 0); self._src_vlay.setSpacing(3)
+        _is_deriv = self.dc.kind in ("derivative", "second_derivative")
+        if _is_deriv:
+            self._add_src(self.dc.sources[0] if self.dc.sources else None)
+        else:
+            for _s in self.dc.sources:
+                self._add_src(_s)
+        self._add_src_btn = QPushButton("＋ Add Signal"); self._add_src_btn.setObjectName("addTraceBtn")
+        self._add_src_btn.clicked.connect(lambda: self._add_src())
+        src_lay.addWidget(self._src_cont); src_lay.addWidget(self._add_src_btn)
+        bl.addWidget(src_grp)
+
         # Kind combo + help
         k_row = QHBoxLayout(); k_row.addWidget(QLabel("Operation:"))
         self._kind_cb = QComboBox(); self._kind_cb.setObjectName("channelPickerCb")
@@ -736,21 +843,30 @@ class DerivedBlock(QFrame):
         self._win_widget = QWidget(); self._win_widget.setLayout(self._win_row)
         bl.addWidget(self._win_widget)
 
-        # Sources — include derived channels as valid sources
-        src_grp = QGroupBox("Sources"); src_grp.setObjectName("cfgGlobalBar")
-        src_lay = QVBoxLayout(src_grp); src_lay.setContentsMargins(6, 4, 6, 4); src_lay.setSpacing(3)
-        self._src_cont = QWidget(); self._src_vlay = QVBoxLayout(self._src_cont)
-        self._src_vlay.setContentsMargins(0, 0, 0, 0); self._src_vlay.setSpacing(3)
-        _is_deriv = self.dc.kind in ("derivative", "second_derivative")
-        if _is_deriv:
-            self._add_src(self.dc.sources[0] if self.dc.sources else None)
-        else:
-            for _s in self.dc.sources:
-                self._add_src(_s)
-        self._add_src_btn = QPushButton("＋ Add Source"); self._add_src_btn.setObjectName("addTraceBtn")
-        self._add_src_btn.clicked.connect(lambda: self._add_src())
-        src_lay.addWidget(self._src_cont); src_lay.addWidget(self._add_src_btn)
-        bl.addWidget(src_grp)
+        # Scale/Offset params
+        self._so_row = QHBoxLayout()
+        self._so_row.addWidget(QLabel("Scale:"))
+        self._scale_sp = QDoubleSpinBox(); self._scale_sp.setRange(-1e6, 1e6); self._scale_sp.setDecimals(6)
+        self._scale_sp.setValue(self.dc.params.get("scale", 1.0))
+        self._scale_sp.setObjectName("traceWidthSpin"); self._scale_sp.setFixedWidth(90)
+        self._scale_sp.valueChanged.connect(lambda v: self.dc.params.update({"scale": v}))
+        self._so_row.addWidget(self._scale_sp)
+        self._so_row.addWidget(QLabel("Offset:"))
+        self._offset_sp = QDoubleSpinBox(); self._offset_sp.setRange(-1e9, 1e9); self._offset_sp.setDecimals(6)
+        self._offset_sp.setValue(self.dc.params.get("offset", 0.0))
+        self._offset_sp.setObjectName("traceWidthSpin"); self._offset_sp.setFixedWidth(90)
+        self._offset_sp.valueChanged.connect(lambda v: self.dc.params.update({"offset": v}))
+        self._so_row.addWidget(self._offset_sp); self._so_row.addStretch()
+        self._so_widget = QWidget(); self._so_widget.setLayout(self._so_row)
+        bl.addWidget(self._so_widget)
+
+        # Filters — only for a single-physical-source passthrough channel
+        # (kind="none"); the embedded block is (re)built by _refresh_filters()
+        self._filters_grp = QGroupBox("Filters"); self._filters_grp.setObjectName("cfgGlobalBar")
+        self._filters_lay = QVBoxLayout(self._filters_grp)
+        self._filters_lay.setContentsMargins(6, 4, 6, 4)
+        self._filters_block: Optional[ChannelPipelineBlock] = None
+        bl.addWidget(self._filters_grp)
 
         # W.r.t. — only for derivative/second_derivative
         self._wrt_grp = QGroupBox("With Respect To"); self._wrt_grp.setObjectName("cfgGlobalBar")
@@ -876,8 +992,10 @@ class DerivedBlock(QFrame):
             if wrt_src and wrt_src not in sources:
                 sources.append(wrt_src)
 
+        self._refresh_filters()
+
         if not sources:
-            self._vars_lbl.setText("No sources — add sources above to use named variables")
+            self._vars_lbl.setText("No signals — add signals above to use named variables")
             return
 
         display_names = [_channel_display_name(self.registry, self.processor, d, c)
@@ -903,6 +1021,36 @@ class DerivedBlock(QFrame):
                     self._code.setTextCursor(c)
                     self._code.blockSignals(False)
 
+    def _refresh_filters(self):
+        """(Re)build the embedded single-source Filters block when eligible:
+        kind is a plain passthrough ("none") with exactly one physical source."""
+        if not hasattr(self, "_filters_grp"):
+            return  # called during initial Sources construction, too early
+        sources = [cb.currentData() for cb in self._src_combos if cb.currentData()]
+        eligible = (self.dc.kind == "none" and len(sources) == 1
+                    and sources[0][0] != "derived")
+        if not eligible:
+            self._filters_grp.setVisible(False)
+            if self._filters_block is not None:
+                self._filters_lay.removeWidget(self._filters_block)
+                self._filters_block.deleteLater()
+                self._filters_block = None
+            return
+        dev_id, ch_id = sources[0]
+        if (self._filters_block is not None
+                and (self._filters_block.dev_id, self._filters_block.ch_id) != (dev_id, ch_id)):
+            self._filters_lay.removeWidget(self._filters_block)
+            self._filters_block.deleteLater()
+            self._filters_block = None
+        if self._filters_block is None:
+            ch_name = _channel_display_name(self.registry, self.processor, dev_id, ch_id)
+            self._filters_block = ChannelPipelineBlock(
+                dev_id, ch_id, ch_name, "", self.processor,
+                show_calibration=False, show_header=False,
+            )
+            self._filters_lay.addWidget(self._filters_block)
+        self._filters_grp.setVisible(True)
+
     def _on_kind(self, idx: int):
         from ui.code_templates import BUILTIN_TEMPLATES, SCRIPT_TEMPLATES
         k = _ALL_KINDS[idx]
@@ -958,12 +1106,33 @@ class DerivedBlock(QFrame):
         self._code.setReadOnly(is_builtin)
         self._edit_as_script_btn.setVisible(is_builtin)
         self._win_widget.setVisible(self.dc.kind == "rms")
+        self._so_widget.setVisible(self.dc.kind == "scale_offset")
+        self._refresh_filters()
         self._wrt_grp.setVisible(is_deriv)
         self._add_src_btn.setVisible(not is_deriv)
         if is_deriv:
             self._wrt_x_row.setVisible(self._wrt_cb.currentIndex() == 1)
 
     def _apply(self):
+        name = self.dc.name.strip()
+        channel_id = self.dc.channel_id.strip()
+        if not name:
+            self._st.setText("⚠ Name cannot be empty")
+            self._st.setStyleSheet("color:#ef4444;")
+            return
+        if not channel_id:
+            self._st.setText("⚠ ID cannot be empty")
+            self._st.setStyleSheet("color:#ef4444;")
+            return
+        others = [d for d in self.processor.get_derived() if d is not self.dc]
+        if any(d.name == name for d in others):
+            self._st.setText(f"⚠ Name '{name}' is already used by another channel")
+            self._st.setStyleSheet("color:#ef4444;")
+            return
+        if any(d.channel_id == channel_id for d in others):
+            self._st.setText(f"⚠ ID '{channel_id}' is already used by another channel")
+            self._st.setStyleSheet("color:#ef4444;")
+            return
         sources = [cb.currentData() for cb in self._src_combos if cb.currentData()]
         if self.dc.kind in ("derivative", "second_derivative"):
             wrt = "channel" if self._wrt_cb.currentIndex() == 1 else "time"