diff --git a/README.md b/README.md
index 7071683..b25653d 100644
--- a/README.md
+++ b/README.md
@@ -2393,8 +2393,9 @@ now — they are listed so they are not mistaken for anything else:
   signal list — in one scrolling column; with four of them open in a 320 px sidebar every
   section was short of room, and finding one meant scrolling past the others. The built
   sidebar is a **Measure** tab (the cursors readout and the measurements) and a **Signals**
-  tab (the trigger and the channels), **each a pill with its own glyph and no text** — the ruler
-  for Measure, a channel list for Signals — with the words kept as each pill's tooltip and
+  tab (the trigger and the channels), **each a pill with its own glyph and no text** — the
+  cursors and the ruler for Measure, the trigger and the channel list for Signals — with the words
+  kept as each pill's tooltip and
   accessible name. The design spec had the switcher showing *titles* and neither page an
   `icon-name`; `narrow` alone does not do it (libadwaita still draws a label beside the icon,
   measured), so the pages carry an empty title and the pills are named in code. With the math
diff --git a/docs/claude/invariants-gtk-and-chrome.md b/docs/claude/invariants-gtk-and-chrome.md
index 52df618..02b8c07 100644
--- a/docs/claude/invariants-gtk-and-chrome.md
+++ b/docs/claude/invariants-gtk-and-chrome.md
@@ -55,14 +55,21 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   binary.** No icon theme has a glyph for an oscilloscope trigger, a pair of cursors or a
   measurement ruler, and the stock names those buttons used to carry said something else
   entirely: a *record dot* for the trigger and three different **magnifiers** for cursors,
-  measurements and math. `src/icons/scalable/actions/udpscope-{trigger,cursors,measure,events,resize-rows,signals}-symbolic.svg`
-  are the six action icons. `udpscope-math-symbolic` left with the toolbar toggle that was its last
+  measurements and math. `src/icons/scalable/actions/udpscope-{trigger,cursors,measure,events,resize-rows,tab-measure,tab-signals}-symbolic.svg`
+  are the seven action icons. `udpscope-math-symbolic` left with the toolbar toggle that was its last
   user; `udpscope-measure-symbolic` **stayed**, because the Preferences window's Plot page carries it --
   an icon with a live user is not an orphan, whatever the toggle that introduced it did -- and it is
-  *also* the Measure tab's icon. `udpscope-signals-symbolic` was drawn for the Signals tab: three rows of
-  a colour chip and a name, which is what that tab mostly is, and deliberately *not* a second copy of the
-  trigger glyph (one shape with two meanings in one window is worse than a new one). Its bars are all one
-  length because unequal ones read as a bar chart, and a chart is not a list. Beside them in
+  the Preferences window's icon, not the tab's.
+
+  The two **tabs** got glyphs of their own, and each is a *pair* rather than one of the icons above:
+  `udpscope-tab-measure-symbolic` is the cursors and the ruler they read against, and
+  `udpscope-tab-signals-symbolic` is the trigger's edge above the channel list it acts on. They are not
+  reuses because a glyph the toolbar already carries means two things the moment a tab shows it too. Both
+  are 16px composites with four features each, which is about the limit of this size: the Signals list is
+  two rows and not three, so the edge and the list get half the cell each, and the bars in it are all one
+  length because unequal ones read as a bar chart, and a chart is not a list. Their ink fractions (32% and
+  36%) sit inside the range the icons above set, which is the check that a composite has not turned into a
+  blot. Beside them in
   `src/icons/scalable/apps/` are the two
   **application** icons, `org.udpscope.app.svg` (128px colour artwork) and
   `org.udpscope.app-symbolic.svg` (16px). The `apps` context is where an icon theme keeps an
@@ -71,7 +78,7 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   into `$XDG_DATA_HOME/icons/hicolor/scalable/apps` and `.../symbolic/apps` — those installed
   copies are what makes `Icon=org.udpscope.app` in the desktop entry resolve (a desktop shell
   cannot read a GResource compiled into the binary).
-  All eight are bundled by `src/icons/udpscope.gresource.xml` (CMake runs
+  All nine are bundled by `src/icons/udpscope.gresource.xml` (CMake runs
   `glib-compile-resources`) and reached through **one**
   `gtk_icon_theme_add_resource_path()` in `run_ui()`, right after `adw_init()` — not at the top
   of `build_toolbar()`, where it used to be: there are two consumers now (the window's own icon,
diff --git a/docs/claude/probe-readings.md b/docs/claude/probe-readings.md
index d1f8278..cb4d269 100644
--- a/docs/claude/probe-readings.md
+++ b/docs/claude/probe-readings.md
@@ -364,7 +364,7 @@ Two lines of the self-check output are assertions in disguise:
   other half — both pills carry a tooltip and an accessible name set by `name_side_tabs()`, so an
   icon-only pill is not an anonymous button — and `pills=0` means nothing is mapped, which makes the
   rest of the line meaningless rather than a pass. `policy=narrow` is read rather than assumed.
-- `page icons: measure=udpscope-measure-symbolic(ok) signals=udpscope-signals-symbolic(ok)` (in the exit
+- `page icons: measure=udpscope-tab-measure-symbolic(ok) signals=udpscope-tab-signals-symbolic(ok)` (in the exit
   dump, beside `toolbar icons:`) — each tab's own glyph and `gtk_icon_theme_has_icon()`'s verdict, read
   on the first tick for the same reason the toolbar's are. **Both must read `(ok)`**: the page titles are
   empty on purpose, so an icon that does not resolve leaves a *blank* pill, and a blank pill looks
diff --git a/docs/claude/verification.md b/docs/claude/verification.md
index ac90b72..5cf2aa4 100644
--- a/docs/claude/verification.md
+++ b/docs/claude/verification.md
@@ -16,9 +16,9 @@ xvfb-run -a env UDPSCOPE_EXIT_AFTER_MS=8000 UDPSCOPE_ENABLE_ALL_MS=1000 \
 Two baselines every run is read against. A clean build emits **four** warnings and no more: two
 `-Wmissing-field-initializers` on `MathNode::source` and `-Woverlength-strings` on **both**
 generated GResource `.c` files — the help pages' (**514660** bytes) and the icons', whose blob is
-**9842** against C99's 4095-byte string-literal limit with the six action icons and the two app icons
+**11309** against C99's 4095-byte string-literal limit with the seven action icons and the two app icons
 that remain (a note about a generated file, which GCC itself supports) -- re-measured when
-the tab work changed the set (that icon left, `udpscope-signals-symbolic` arrived, and this file's
+the tab work changed the set (that icon left, the two tab glyphs arrived, and this file's
 help page was rewritten), which did not move the count; re-measure by touching each `*.gresource.xml`
 under `src/` and rebuilding. The fifth warning that used to appear here was an unused
 `output_built` in `math_probe()`; it was **deleted** as dead code — redundant with the
diff --git a/src/icons/scalable/actions/udpscope-signals-symbolic.svg b/src/icons/scalable/actions/udpscope-signals-symbolic.svg
deleted file mode 100644
index 134ab8c..0000000
--- a/src/icons/scalable/actions/udpscope-signals-symbolic.svg
+++ /dev/null
@@ -1,19 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!-- SPDX-License-Identifier: MIT -->
-<!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
-<!-- The Signals tab's own glyph: the channel list, drawn as a list. Three rows of a
-     colour chip and a name, the shape the signal panel's own rows have — which is
-     what the tab mostly *is*, and which is why it is not the trigger icon: the
-     toolbar's trigger button already carries that one, and one glyph with two
-     meanings in one window is worse than a new glyph. The bars are all one length
-     on purpose: unequal ones read as a bar chart, and a chart is not a list. Every
-     coordinate is a whole pixel of the 16px cell, every subpath is a filled `path`
-     wound the same way, and the 2px bars match the house stroke weight. -->
-<svg height="16px" width="16px" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg">
-  <path fill="#2e3436" d="M1 1 H4 V4 H1 Z
-                          M6 2 H14 V4 H6 Z
-                          M1 6 H4 V9 H1 Z
-                          M6 7 H14 V9 H6 Z
-                          M1 11 H4 V14 H1 Z
-                          M6 12 H14 V14 H6 Z"/>
-</svg>
diff --git a/src/icons/scalable/actions/udpscope-tab-measure-symbolic.svg b/src/icons/scalable/actions/udpscope-tab-measure-symbolic.svg
new file mode 100644
index 0000000..4a3a303
--- /dev/null
+++ b/src/icons/scalable/actions/udpscope-tab-measure-symbolic.svg
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- SPDX-License-Identifier: MIT -->
+<!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
+<!-- The Measure tab: the cursors and the ruler they read against, in one glyph. Two markers, each a
+     cap over a dashed shaft, stand across a ruler: the ruler is two bars with three hanging ticks.
+     The ruler's ends are open on purpose. A closed frame puts four more pixels of ink at the left
+     and right edges, which at this size is what turns a ruler into a rectangle. The shafts stop at
+     the bars rather than crossing them, the way a marker on a plot sits over the scale. Whole
+     pixels, filled `path`s wound the same way, and an ink fraction of 36%, in line with the ruler
+     and the cursors it is made of. -->
+<svg height="16px" width="16px" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg">
+  <path fill="#2e3436" d="M3 1 H7 V3 H3 Z
+                          M9 1 H13 V3 H9 Z
+                          M4 3 H6 V6 H4 Z
+                          M10 3 H12 V6 H10 Z
+                          M4 14 H6 V16 H4 Z
+                          M10 14 H12 V16 H10 Z
+                          M2 6 H14 V8 H2 Z
+                          M2 12 H14 V14 H2 Z
+                          M4 8 H5 V11 H4 Z
+                          M8 8 H9 V10 H8 Z
+                          M12 8 H13 V11 H12 Z"/>
+</svg>
diff --git a/src/icons/scalable/actions/udpscope-tab-signals-symbolic.svg b/src/icons/scalable/actions/udpscope-tab-signals-symbolic.svg
new file mode 100644
index 0000000..ffdcca9
--- /dev/null
+++ b/src/icons/scalable/actions/udpscope-tab-signals-symbolic.svg
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- SPDX-License-Identifier: MIT -->
+<!-- SPDX-FileCopyrightText: 2026 Martino Ferrari -->
+<!-- The Signals tab: the trigger *and* the channel list it acts on, in one glyph. A rising edge
+     crossing a dashed level is the trigger as the toolbar already draws it; below it, two rows of a
+     colour chip and a name are the channel list, which is what the page mostly is. Two rows and not
+     three, so the edge and the list each get half the cell: at 16px a third row costs the edge its
+     clearance and the whole thing turns into a grid. Whole pixels, filled `path`s wound the same
+     way, and the 2px bars match the house stroke weight. -->
+<svg height="16px" width="16px" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg">
+  <path fill="#2e3436" d="M6 1 H8 V6 H6 Z
+                          M6 1 H15 V3 H6 Z
+                          M0 5 H2 V7 H0 Z
+                          M3 5 H5 V7 H3 Z
+                          M12 5 H14 V7 H12 Z
+                          M1 9 H4 V12 H1 Z
+                          M6 10 H14 V12 H6 Z
+                          M1 13 H4 V15 H1 Z
+                          M6 13 H14 V15 H6 Z"/>
+</svg>
diff --git a/src/icons/udpscope.gresource.xml b/src/icons/udpscope.gresource.xml
index a9900b1..1370c9f 100644
--- a/src/icons/udpscope.gresource.xml
+++ b/src/icons/udpscope.gresource.xml
@@ -20,7 +20,8 @@
     <file preprocess="xml-stripblanks">scalable/actions/udpscope-trigger-symbolic.svg</file>
     <file preprocess="xml-stripblanks">scalable/actions/udpscope-cursors-symbolic.svg</file>
     <file preprocess="xml-stripblanks">scalable/actions/udpscope-measure-symbolic.svg</file>
-    <file preprocess="xml-stripblanks">scalable/actions/udpscope-signals-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-tab-measure-symbolic.svg</file>
+    <file preprocess="xml-stripblanks">scalable/actions/udpscope-tab-signals-symbolic.svg</file>
     <file preprocess="xml-stripblanks">scalable/actions/udpscope-events-symbolic.svg</file>
     <file preprocess="xml-stripblanks">scalable/actions/udpscope-resize-rows-symbolic.svg</file>
     <file preprocess="xml-stripblanks">scalable/apps/org.udpscope.app.svg</file>
diff --git a/src/ui/main-window.ui b/src/ui/main-window.ui
index 3c366fa..628ba55 100644
--- a/src/ui/main-window.ui
+++ b/src/ui/main-window.ui
@@ -60,10 +60,12 @@
                `select_side_tab()` and the session file, and the words are re-attached to the pills in
                code — tooltip and accessible name — by `name_side_tabs()` on the first tick, so an
                icon-only pill is still a named thing rather than an anonymous button.
-               Each page's icon is its own glyph: `udpscope-measure-symbolic` is the ruler the
-               measurements used as a toggle, and `udpscope-signals-symbolic` is the channel list,
-               drawn for this tab rather than reusing the toolbar's trigger icon — one glyph
-               meaning two things in one window is worse than a new one. -->
+               Each page's icon is a glyph of its own, and each one is a *pair*: the Measure tab is
+               `udpscope-tab-measure-symbolic` (the cursors and the ruler they read against), and the
+               Signals tab is `udpscope-tab-signals-symbolic` (the trigger's edge and the channel list
+               below it). They are drawn for the tabs rather than reusing the icons the toolbar and the
+               Preferences window already carry: a glyph the toolbar uses for one thing means two things
+               the moment a tab shows it too. -->
           <object class="GtkBox" id="side_column">
             <property name="orientation">vertical</property>
             <property name="width-request">300</property>
@@ -84,8 +86,9 @@
                   <object class="AdwViewStackPage">
                     <property name="name">measure</property>
                     <property name="title"></property>
-                    <!-- The ruler: what the pane measures the waveform with. -->
-                    <property name="icon-name">udpscope-measure-symbolic</property>
+                    <!-- The cursors and the ruler: what the pane brackets, and what it
+                         reads the bracketed window with. -->
+                    <property name="icon-name">udpscope-tab-measure-symbolic</property>
                     <property name="child">
                       <object class="GtkScrolledWindow">
                         <property name="hscrollbar-policy">never</property>
@@ -103,8 +106,8 @@
                   <object class="AdwViewStackPage">
                     <property name="name">signals</property>
                     <property name="title"></property>
-                    <!-- The channel list this page mostly is. -->
-                    <property name="icon-name">udpscope-signals-symbolic</property>
+                    <!-- The trigger and the channel list it acts on. -->
+                    <property name="icon-name">udpscope-tab-signals-symbolic</property>
                     <property name="child">
                       <object class="GtkScrolledWindow">
                         <property name="hscrollbar-policy">never</property>