diff --git a/README.md b/README.md
index cba3458..60ef547 100644
--- a/README.md
+++ b/README.md
@@ -118,10 +118,11 @@ place (it opens the list, and `+` is hidden): the E-1608's 8 analog inputs and c
 otherwise. The signal badges sit in a scroller, so the bar's minimum width, and with it the window's,
 never depends on how many signals there are. The badge order is kept **for the session only**; it is not
 written to the session file. The right-hand end carries two words-only badges: **Trigger** (`off`, `armed`, `capturing`, `triggered`
-or `disarmed`) and **Source** (the kind's name only -- the link state is the status bar's; a read-out, not a button,
-for a source with no controls of its own, and for a file). A badge opens the **slide-over**: a 360 px
+or `disarmed`) and **Source** (the kind's name only -- the link state is the status bar's). **Source is shown only when the source
+has panels of its own** (the E-1608's); for UDPS, Flat UDP and a file there is nothing for it to open, so it is hidden
+(the bar keeps its height; the kind's name is in the status bar). A badge opens the **slide-over**: a 360 px
 panel laid over the plot's right edge, opaque, with its own title, a *Close* button and one scroller per
-page. The Trigger badge opens the trigger form; the Source badge opens the source kind's own panels
+page. The Trigger badge opens the trigger form; the Source badge (when shown) opens the source kind's own panels
 (the E-1608's *Analog out* and *Digital I/O*, behind a segmented switch at the top of the panel). It
 closes with a second click on its badge, with `Esc`, with *Close*, or with a click on the plot; it never
 resizes the plot. The right-hand **dock** (the existing sidebar, 320 px) holds what is left of the old
diff --git a/docs/claude/architecture.md b/docs/claude/architecture.md
index 7446c30..9487074 100644
--- a/docs/claude/architecture.md
+++ b/docs/claude/architecture.md
@@ -113,7 +113,9 @@ touching the data path.
   **Source** badges). `sync_signal_badges()` rebuilds the signal badges (from `rebuild_signal_panels()`);
   their order is `App::badge_order`, in memory only. A badge is a flat button whose `page` is the slide-over page it
   toggles; the Source badge's page is the first `source-*` page, and a kind with none (UDPS, Flat UDP, a
-  file) leaves it a read-out with `can_target` off.
+  file) leaves it **hidden** (the user asked for hide here, not the usual disable): `sync_badge_bar()` sets its visibility,
+  pick and focus from `slideover.source_pages` being non-empty every tick, so anything that indexes the badge
+  (the tour's `badges` step targets the whole bar, `[badges]`) must tolerate it being absent.
 - **The dock** is the `AdwOverlaySplitView` sidebar (`side_box` > `dock_scroller` > `dock_page`): the
   cursors and the measurements only, in one scroller (the signal list is the `signals` page). It holds no tab switcher and no
   revealer, and it does not hold a source kind's panels (those are slide-over pages).
diff --git a/docs/claude/invariants-plot-and-layout.md b/docs/claude/invariants-plot-and-layout.md
index 1b962d5..89c4ac3 100644
--- a/docs/claude/invariants-plot-and-layout.md
+++ b/docs/claude/invariants-plot-and-layout.md
@@ -117,7 +117,7 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   (`height-request`) between `plot_overlay` and the status line, so the plot above it never moves when a
   badge's text changes (`bar_h` = `bar_h_after` in `[badges]`). This is "layout must not depend on
   content" for the new row: the Trigger badge's state is a word from a short fixed set and the Source badge
-  is a kind's display name only (no connection state: that is the status bar's), so what changes with the stream is the row's *width* (the bar has room to
+  (shown only when the kind has source pages; hidden otherwise) is a kind's display name only (no connection state: that is the status bar's), so what changes with the stream is the row's *width* (the bar has room to
   spare on the right) and never its height. The badge labels are not ellipsized: a name long enough to
   need it would be a defect of the kind's `display_name()`. Rows that appear by trigger condition appear
   inside the slide-over's scroller, never in the bar.
@@ -127,8 +127,8 @@ Part of [CLAUDE.md](../../CLAUDE.md). These are rules that cost a defect to lear
   (the E-1608: eight inputs and the counter) would push the window's minimum width past a laptop screen.
   Past `kMaxSignalBadges` (6) the row is replaced by one "N signals" badge, which also stands for the `+`.
   The bar's height stays 36 px in every one of these states (`bar_h_fixed` in `[sigbadges]`), and
-  `bar_min_w` reads the same with one signal, nine signals and the overflow (244 on the E-1608, 251 on UDPS:
-  the Source badge of each kind reads differently). A change that makes it grow with the signal count has
+  `bar_min_w` reads the same with one signal, nine signals and the overflow (244 on the E-1608, 124 on UDPS:
+  the Source badge is on screen for the E-1608 and hidden for UDPS, and its text differs by kind). A change that makes it grow with the signal count has
   taken the scroller out of the measurement.
 - **The dock's width is fixed too** (`side_column` `width-request` 300, the split view's 320 px floor
   and cap), and it holds one scroller with the cursors and the measurements. A
diff --git a/docs/claude/probe-readings.md b/docs/claude/probe-readings.md
index 717ee86..96e35cd 100644
--- a/docs/claude/probe-readings.md
+++ b/docs/claude/probe-readings.md
@@ -2663,14 +2663,14 @@ signals list while the title and the badge marker still name `trigger`; `-1` whe
 ## `[sigbadges]`
 
 ```
-[sigbadges] enabled=4 badges=4 overflow=0 overflow_text=- plus_visible=1 dot_plotted=4 bar_h=36 bar_h_fixed=1 bar_min_w=251 opens=1 plus_opens=1
+[sigbadges] enabled=4 badges=4 overflow=0 overflow_text=- plus_visible=1 dot_plotted=4 bar_h=36 bar_h_fixed=1 bar_min_w=124 opens=1 plus_opens=1
 ```
 
 `UDPSCOPE_PROBE_SIGNAL_BADGES_MS` reads the signal badges. `badges` must equal `enabled` (the enabled, listed signals) while `enabled` is at most 6
 (`kMaxSignalBadges`); beyond that `badges=0 overflow=1 overflow_text=<N> signals plus_visible=0` (the "N signals" badge replaces the badges and the "+"). `dot_plotted` is the number of
 badges whose signal is on a plot (its dot is then the trace colour, not the unplotted grey). `bar_h` is the bar's allocated height and `bar_h_fixed=1` that neither it nor its natural
 height moved while one signal was switched off and on again (`rebuild_signal_panels()` each time), and that the badge count followed; `0` is a bar whose height depends on its content.
-`bar_min_w` is only a record: the scroller must keep it the same however many signals there are (it reads 251 with the UDPS mock's 4 and with the overflow forced on, and 244 against the E-1608 mock with one signal and with nine -- the overflow, `enabled=9 badges=0 overflow=1 overflow_text=9 signals plus_visible=0 bar_h=36 bar_h_fixed=1`; a value that grows with the signal count is a scroller that has stopped constraining the bar). `opens=1`: clicking the
+`bar_min_w` is only a record: the scroller must keep it the same however many signals there are (it reads 124 with the UDPS mock's 3 (the Source badge being hidden there) and with the overflow forced on, and 244 against the E-1608 mock with one signal and with nine -- the overflow, `enabled=9 badges=0 overflow=1 overflow_text=9 signals plus_visible=0 bar_h=36 bar_h_fixed=1`; a value that grows with the signal count is a scroller that has stopped constraining the bar). `opens=1`: clicking the
 first signal badge opens `signal:<name>` with the badge marked open and a second click closes it (`-1` when overflowed, there being no signal badges); `plus_opens=1` the same for the "+"
 (the overflow badge when overflowed) and the `signals` page.
 
@@ -2691,7 +2691,7 @@ gesture's threshold, the slide-over closing under it and the pointer-driven drop
 
 ```
 [badges] table_bad=0 trigger_state=off bar_h=36 bar_h_after=36 fixed=1 open_marked=1 page_open=1 closed_unmarked=1
-[badges] source name=UDPStreamer state=connected pages=0 switch_visible=0 can_target=0 second_page=- second_ok=-1 open_marked=-1 closed_unmarked=1 panel_min_w=0
+[badges] source name=UDPStreamer pages=0 visible=0 switch_visible=0 can_target=0 second_page=- second_ok=-1 open_marked=-1 closed_unmarked=1 panel_min_w=0
 ```
 
 `UDPSCOPE_PROBE_BADGES_MS` reads the badge bar under the plot. **Line 1** is the Trigger badge: `table_bad=0` (the rows of the 16-input
@@ -2700,12 +2700,13 @@ the same, and at least 36 px, before and after the `trigger` page was opened and
 moves), `open_marked=1` / `page_open=1` / `closed_unmarked=1` (the `udpscope-badge-open` class follows the slide-over's page, both ways; `0` on
 any is a badge that does not say its panel is open, or one that stays marked after it closed).
 
-**Line 2** is the Source badge, and every field has a value it must read:
+**Line 2** is the Source badge, which is **hidden when the source has no pages** (UDPS, Flat UDP, a file), and every field has a value it must read:
 
 - `name=` the source kind's name, as the badge shows it. The badge carries no link state (the status bar says it); there is no `state=` field.
 - `pages=` the number of slide-over pages the source kind contributes (`source-<id>`): `0` for UDPS, `2` for the E-1608 (`source-ao`, `source-dio`).
-  `can_target=0` with `pages=0` is the UDPS badge being a read-out rather than a button; `can_target=1` with `pages>0` is the button being live.
+  `can_target=0` with `pages=0` is the UDPS badge being untargetable, which goes with it being hidden; `can_target=1` with `pages>0` is the button being live.
   `can_target=1` with `pages=0` is a dead button that opens nothing.
+- `visible=` the badge being on screen: **`0` with `pages=0`** (hidden, by design: nothing to open), `1` with `pages>0`. `visible=1` with `pages=0` is a dead pill that was supposed to be hidden; `visible=0` with pages is a source panel nothing can open.
 - `switch_visible=` the segmented switch being on screen after the first source page was opened: `1` with two or more pages, `0` with one or none.
   A switch shown for a single page is a control that cannot change anything; hidden with two, the second panel is unreachable.
 - `second_page=` / `second_ok=` what `slideover_page()` read after the switch selected the second page, and whether it is that page. **`second_ok=1` with
diff --git a/docs/claude/verification.md b/docs/claude/verification.md
index 25f5d9f..8a07d37 100644
--- a/docs/claude/verification.md
+++ b/docs/claude/verification.md
@@ -473,12 +473,13 @@ precedent, not an exception.
   **The source kind's panels are slide-over pages too** (`source-<id>`: the E-1608's `source-ao` and
   `source-dio`, Flat UDP's, the probe kind's), so the same rule holds for them. The probe appends a second
   `[badges]` line for the Source badge: `[badges] source name=<kind> pages=<n>
-  switch_visible=<0|1> can_target=<0|1> second_page=<id|-> second_ok=<0|1> open_marked=<0|1|-1>
+  visible=<0|1> switch_visible=<0|1> can_target=<0|1> second_page=<id|-> second_ok=<0|1> open_marked=<0|1|-1>
   closed_unmarked=1`. `pages` is the number of source pages, `switch_visible` is the segmented switch
   being on screen after the first source page was opened (`1` for the E-1608's two pages, `0` for one page
   or none), `second_page` is what `slideover_page()` read after the switch selected the second page
-  (`second_ok=1` when it is that page), `can_target=0` with `pages=0` is the UDPS badge being a read-out and
-  `open_marked=-1` is that no-page case (there is nothing to open).
+  (`second_ok=1` when it is that page), `visible=0` with `pages=0` is the UDPS badge being **hidden** (a kind with no source page
+  has nothing for it to open; `can_target=0` goes with it) and `open_marked=-1` is that no-page case (there is
+  nothing to open); `visible=1` with `pages>0`.
 - `UDPSCOPE_PROBE_SOURCE_KINDS=2000` with `UDPSCOPE_EXIT_AFTER_MS=5000`, run as `--source probe --source-opt rate=500`
   -- the source-plugin path end to end. The variable's presence also registers the test-only `probe` kind (a
   synthetic sine with one panel), so it is the only way a run sees that kind; its value is the delay in ms.
diff --git a/src/ui_app.hpp b/src/ui_app.hpp
index a9322ee..2f2603e 100644
--- a/src/ui_app.hpp
+++ b/src/ui_app.hpp
@@ -160,7 +160,7 @@ struct BadgeBar {
   GtkWidget* signals_slot = nullptr;  ///< left; empty in step 1, step 2 fills it
   GtkWidget* system_slot = nullptr;   ///< right: Trigger, Source
   Badge trigger;
-  Badge source;                       ///< opens the first source page; a read-out when the source has none
+  Badge source;                       ///< opens the first source page; hidden when the source has none
   GtkWidget* signals_row = nullptr;   ///< the box inside the scroller: signal badges, then the "+"
   /// One per shown enabled signal; empty when overflowed. `unique_ptr`: each button's "clicked" handler holds
   /// a pointer to its `Badge`, which must not move when the vector does.
diff --git a/src/ui_badges.cpp b/src/ui_badges.cpp
index 485a84b..19ad510 100644
--- a/src/ui_badges.cpp
+++ b/src/ui_badges.cpp
@@ -173,13 +173,16 @@ void build_badge_bar(App& app) {
   bb.signals_slot = app.badge_signals;
   bb.system_slot = app.badge_system;
   make_badge(app, bb.trigger, bb.system_slot, "Trigger", "trigger");
-  // The first source page is where the badge goes; a source with none (UDPS) has nothing to open, so its
-  // badge is a read-out: not a target, not focusable, but still on screen.
+  // The first source page is where the badge goes; a source with none (UDPS, Flat UDP, a file) has nothing to
+  // open, so its badge is hidden (`sync_badge_bar` keeps it in step with the slide-over's source pages) and, for
+  // as long as it is, neither a target nor focusable. Hidden, not insensitive: a dead "Source" pill that does
+  // nothing was only noise. The bar's height is fixed, so the row loses width and never height.
   const std::string first = app.source_panels.empty() ? std::string() : app.source_panels.front().name;
   make_badge(app, bb.source, bb.system_slot, "Source", first);
   if (first.empty()) {
     gtk_widget_set_can_target(bb.source.button, FALSE);
     gtk_widget_set_focusable(bb.source.button, FALSE);
+    gtk_widget_set_visible(bb.source.button, FALSE);
   }
   // The link state is the status bar's to say; the badge names the source and opens its pages. The empty
   // state label is hidden, as the "+" badge's is, rather than leaving a gap in the pill.
@@ -278,6 +281,14 @@ void sync_badge_bar(App& app) {
     set_open(sb->button, slideover_page(app) == sb->page);
   }
   if (bb.source.button == nullptr) return;
+  // Shown only while there is a source page to open. The slide-over's page list is the truth, so a page that is
+  // registered later brings the badge back, and its focus and pick with it.
+  const bool has_source_pages = !app.slideover.source_pages.empty();
+  if ((gtk_widget_get_visible(bb.source.button) != FALSE) != has_source_pages) {
+    gtk_widget_set_visible(bb.source.button, has_source_pages);
+    gtk_widget_set_can_target(bb.source.button, has_source_pages);
+    gtk_widget_set_focusable(bb.source.button, has_source_pages);
+  }
   // The source's name; the link state is the status bar's. A file has no kind worth naming.
   const bool file_mode = app.replaying || !app.model->config().open_waveform.empty();
   std::string name = "Source";
@@ -322,7 +333,8 @@ gboolean badges_probe(gpointer user) {
                bad, gtk_label_get_text(GTK_LABEL(a->badges.trigger.state)), h_closed, h_after,
                h_closed == h_after && h_closed >= 36 ? 1 : 0, marked_open ? 1 : 0, page_open ? 1 : 0,
                marked_closed ? 1 : 0);
-  // The Source badge: its read-out, and the segmented switch of a source with several panels.
+  // The Source badge: shown only with a source page (`visible=`; hidden, the page-dependent fields read -1 or 0),
+  // and the segmented switch of a source with several panels.
   const std::string first = a->badges.source.page;
   bool switch_visible = false;
   int second_ok = -1;  // -1: there is no second page to select (one source page, or none)
@@ -348,11 +360,11 @@ gboolean badges_probe(gpointer user) {
   }
   slideover_close(*a);
   std::fprintf(stderr,
-               "[badges] source name=%s pages=%zu switch_visible=%d can_target=%d second_page=%s "
+               "[badges] source name=%s pages=%zu visible=%d switch_visible=%d can_target=%d second_page=%s "
                "second_ok=%d open_marked=%d closed_unmarked=%d panel_min_w=%d\n",
                gtk_label_get_text(GTK_LABEL(a->badges.source.name)),
                a->slideover.source_pages.size(),
-               switch_visible ? 1 : 0, gtk_widget_get_can_target(a->badges.source.button) ? 1 : 0,
+               gtk_widget_get_visible(a->badges.source.button) ? 1 : 0, switch_visible ? 1 : 0, gtk_widget_get_can_target(a->badges.source.button) ? 1 : 0,
                second_page.empty() ? "-" : second_page.c_str(), second_ok,
                first.empty() ? -1 : marked ? 1 : 0,
                gtk_widget_has_css_class(a->badges.source.button, "udpscope-badge-open") ? 0 : 1, widest);
diff --git a/src/ui_tour.cpp b/src/ui_tour.cpp
index d698849..d77a640 100644
--- a/src/ui_tour.cpp
+++ b/src/ui_tour.cpp
@@ -446,9 +446,9 @@ constexpr TourStep kTourSteps[] = {
      &App::area_overlay},
     {"badges", nullptr, "The badges",
      "Setup is reached by the thing it configures. A badge per signal opens that signal's colour, "
-     "calibration and plot; the + opens the full list; Trigger and Source open their own forms. Drag a "
-     "signal badge onto a plot to draw it there, or onto another badge to reorder. Click again, press "
-     "Esc or click the plot to close the panel.",
+     "calibration and plot; the + opens the full list; Trigger opens its form, and so does Source when "
+     "the source has controls of its own. Drag a signal badge onto a plot to draw it there, or onto "
+     "another badge to reorder. Click again, press Esc or click the plot to close the panel.",
      &App::badge_bar},
     {"trigger", "trigger", "The trigger",
      "Describe an event -- a signal, a condition, a level and the window around it -- and arm it: "