fix(config): put the old value back when a setter is rejected

Config.Save() validates the whole config, so a setter that assigned
before validating did not merely fail its own call: the rejected value
stayed in memory and failed every later save, of every unrelated
setting, silently and for the rest of the session. Nothing reached
disk, so a restart cleared it — which is what made the fault invisible
and unreportable.

The defect is precisely "assignment precedes a validation that can
reject that argument", and that predicate enumerates seven setters
rather than the whole file. Each snapshots the field and restores it on
the error path.

The remaining setters were read rather than assumed and are unchanged:
shortcuts.Config.Validate returns nil unconditionally, the bools and
SetFavoritesPlaylistID pass through no validation that inspects them,
Config.Validate does not validate Downloads at all, and SetViewVisible
refuses an unknown, non-hideable or launch-page view before assigning.
SetLibraryDirectory was already correct and is the precedent the new
comment points at: it validates a candidate before assigning, so there
is nothing to undo.

The rationale sits above the setter section rather than on Save(),
which is bound — a doc comment there renders into frontend/bindings
for an audience with no use for it.

Closes #231

CLAUDE.md

@@ -662,6 +662,28 @@ rather than renaming them.
   one of the shell's rows, which is what the skip link is absolutely
   positioned to avoid.
 - `config` — TOML-based settings. Settings page uses HTMX + templ for server-rendered HTML fragments.
+
+  **A setter that can reject its argument puts the old value back**, and
+  that is a correctness rule rather than hygiene (#231). `Save()`
+  validates the *whole* config, so a value left behind by a failed write
+  does not merely fail its own call: it fails every later save, of every
+  unrelated setting — theme, launch page, shortcuts, libraries — for the
+  rest of the session. Nothing reaches disk, so a restart clears it,
+  which is exactly what makes the fault invisible and unreportable. One
+  rejected track-list column list was enough to stop the app saving
+  anything at all.
+
+  Two shapes are safe and a third is the trap. A setter that assigns and
+  *then* validates snapshots the field first and restores it on the
+  error path — seven do. `SetLibraryDirectory` is the better shape where
+  the value can be built on its own: it validates a candidate *before*
+  assigning, so there is nothing to undo. And a setter whose argument no
+  validation inspects needs neither — the bools, the favourites playlist
+  id and the shortcut bindings, plus `SetViewVisible`, which refuses an
+  unknown, non-hideable or launch-page view up front so
+  `GeneralConfig.Validate` never sees one it would fail on. Which set a
+  new setter joins is decided by whether its own `Validate` can reject
+  it, not by preference.
 - `playlist` / `smartplaylist` — Playlist CRUD and rule-based smart playlists.
 - `mediacontrols` — OS media controls behind one `Handler`: MPRIS over
   D-Bus on desktop Linux, a MediaSession on Android, a no-op stub
@@ -1486,6 +1508,28 @@ live**: a scrim over a menu item is that item's text surface, and the
 14px spends its weight below the last legible label, measured at 9.9:1
 on the light ramp, whose `bgElevated` is `#e9ecef`.
 
+**And the phone has two sheets, so that rule is one file both read**
+(#210). `bottom-nav`'s "More" is capped at the same 85vh and overflows
+for the same reason — measured at 424x439 with eight destinations,
+`scrollHeight` 412 against `clientHeight` 373, and eleven items at 48px
+would be 528, since #25 makes the count the user's. So the two layers
+live in `styles/sheet-scroll.css.ts` and each host says only what is
+local to it: the colour, handed over as `--yj-sheet-surface` on the same
+box, because the nav sheet paints the sidebar's `--yj-bg-surface` and
+the context sheet the menus' `--yj-bg-elevated` — a shared rule that
+hard-coded either would draw that seam across the other one.
+
+The half that is not the fade is what makes it visible: **nothing inside
+the sheet may repaint the surface**, because these are background layers
+on the scroller and an opaque child covers them. `menu-surface` already
+had it from the other side (`.context-menu-panel[data-sheet]` is
+`background-color: transparent`); `app-sidebar`'s host paints
+`--yj-bg-surface`, which in the shell is its own background and in the
+sheet is a second copy of the sheet's, so `bottom-nav` turns it off.
+Measured at 424x439 with the fade adopted and that rule missing: a flat
+52,58,64 to the bottom edge with 39px still below, which is the defect
+unchanged and every assertion about `background-attachment` passing.
+
 **The playlist submenu is a sheet too, and it had to be.** It is a
 `placement="right-start"` flyout, and making the menu full-width moved
 its anchor — measured at x −182 to 0, entirely off-screen, so "Add to
@@ -1848,6 +1892,21 @@ is not it.** A `placeholder` is an accname fallback, so an
 Explore's search box — the audit's own `a11y.26` — as clean. A sweep
 for *empty* names cannot see a *weak* one.
 
+**`title` is the same trap one rung lower, and it defeats the obvious
+spec as well as the obvious sweep.** `queue-panel`'s Clear queue and
+Add queue to playlist were named by `title` alone, so
+`getByRole('button', { name: 'Clear queue' })` matched them **before**
+the fix as well as after — a `getByRole` assertion, which is what
+catches every other nameless control in this app, would have been
+green on the broken build. `title` is the *last* fallback in the
+accname order, so content put inside the button later silently
+outranks it, and it is the one name a phone cannot show, having no
+hover. The property is therefore asserted as *the name is not the
+tooltip*: `queue-overlay.spec.ts` removes the `title` attributes and
+asks again, which is 1 and 1 with `aria-label` and was measured at 0
+and 0 without it. The `title`s stay, because on a desktop they are
+also the tooltip for an icon-only control and that is a different job.
+
 **The shell scrolls sideways and not down.** `body` is
 `overflow-x: auto; overflow-y: hidden`, and both halves are measured.
 Vertically there is nothing to fix: the middle grid row is `1fr` and

backend/config/config.go

@@ -303,6 +303,24 @@ func (c *Config) GetLibraryDirectory() string {
 	return string(c.Library.DirectoryPath)
 }
 
+// A rejected setter puts the old value back, and that is not tidiness
+// (#231).  Save validates the *whole* config, so a value left behind by
+// a failed write does not merely fail its own call: it fails every
+// later save, of every unrelated setting, silently and for the rest of
+// the session.  Nothing reaches disk, so a restart clears it -- which
+// is exactly what makes the fault hard to see and impossible to report.
+//
+// The setters below that assign and then validate therefore snapshot
+// the field first and restore it on the error path.  SetLibraryDirectory
+// is the other safe shape and the better one where the value can be
+// built on its own: it validates a candidate *before* assigning
+// anything, so there is nothing to undo.
+//
+// Not every setter needs either.  A bool, an int64 and the shortcut
+// bindings pass through no validation that can reject them, and
+// SetViewVisible refuses an unknown, non-hideable or launch-page view
+// up front, so GeneralConfig.Validate never sees one it would fail on.
+
 // SetLibraryDirectory validates and saves a new library directory,
 // then emits the LibraryConfigChanged event so listeners (e.g. the
 // Library scanner) can react.
@@ -360,11 +378,14 @@ func (c *Config) SetScanConcurrency(mode string) error {
 		c.Library.ApplyDefaults()
 	}
 
+	previous := c.Library.ScanConcurrency
 	c.Library.ScanConcurrency = library.ScanConcurrency(
 		mode,
 	)
 
 	if err := c.Library.Validate(); err != nil {
+		c.Library.ScanConcurrency = previous
+
 		return fmt.Errorf(
 			"invalid scan concurrency mode: %w", err,
 		)
@@ -455,9 +476,12 @@ func (c *Config) SetThemeAccentColor(
 		c.Theme.ApplyDefaults()
 	}
 
+	previous := c.Theme.AccentColor
 	c.Theme.AccentColor = color
 
 	if err := c.Theme.Validate(); err != nil {
+		c.Theme.AccentColor = previous
+
 		return fmt.Errorf(
 			"invalid theme accent color: %w", err,
 		)
@@ -488,9 +512,12 @@ func (c *Config) SetThemeBackgroundShade(
 		c.Theme.ApplyDefaults()
 	}
 
+	previous := c.Theme.BackgroundShade
 	c.Theme.BackgroundShade = theme.BackgroundShade(shade)
 
 	if err := c.Theme.Validate(); err != nil {
+		c.Theme.BackgroundShade = previous
+
 		return fmt.Errorf(
 			"invalid theme background shade: %w", err,
 		)
@@ -544,9 +571,12 @@ func (c *Config) SetDefaultPage(page string) error {
 		c.General.ApplyDefaults()
 	}
 
+	previous := c.General.DefaultPage
 	c.General.DefaultPage = View(page)
 
 	if err := c.General.Validate(); err != nil {
+		c.General.DefaultPage = previous
+
 		return fmt.Errorf(
 			"invalid default page: %w", err,
 		)
@@ -591,9 +621,12 @@ func (c *Config) SetQueueFallback(mode string) error {
 		c.General.ApplyDefaults()
 	}
 
+	previous := c.General.QueueFallback
 	c.General.QueueFallback = QueueFallback(mode)
 
 	if err := c.General.Validate(); err != nil {
+		c.General.QueueFallback = previous
+
 		return fmt.Errorf(
 			"invalid queue fallback: %w", err,
 		)
@@ -801,9 +834,12 @@ func (c *Config) SetTrackListColumns(
 		c.TrackList = &tracklist.Config{}
 	}
 
+	previous := c.TrackList.Columns
 	c.TrackList.Columns = columns
 
 	if err := c.TrackList.Validate(); err != nil {
+		c.TrackList.Columns = previous
+
 		return fmt.Errorf(
 			"invalid track-list columns: %w", err,
 		)
@@ -901,9 +937,12 @@ func (c *Config) SetFavoritesIconStyle(
 		c.Favorites.ApplyDefaults()
 	}
 
+	previous := c.Favorites.IconStyle
 	c.Favorites.IconStyle = favorites.IconStyle(style)
 
 	if err := c.Favorites.Validate(); err != nil {
+		c.Favorites.IconStyle = previous
+
 		return fmt.Errorf(
 			"invalid favorites icon style: %w", err,
 		)

backend/config/setter_rollback_test.go

@@ -0,0 +1,262 @@
+package config
+
+import (
+	"log/slog"
+	"path/filepath"
+	"testing"
+
+	"yellowjacket/backend/library"
+	"yellowjacket/backend/tracklist"
+)
+
+// newSavableConfig builds a loaded, valid config in a temp directory,
+// so Save() writes rather than refusing with errSaveBeforeLoad.
+//
+// The library directory is real and set, because Config.Validate only
+// validates the Library section when DirectoryPath is non-empty -- an
+// empty one would hide a poisoned ScanConcurrency from the whole-config
+// save that is the symptom under test.
+func newSavableConfig(t *testing.T) *Config {
+	t.Helper()
+
+	c := &Config{
+		logger:   slog.Default(),
+		filePath: filepath.Join(t.TempDir(), "config.toml"),
+		Library: &library.Config{
+			DirectoryPath: library.Directory(t.TempDir()),
+		},
+	}
+
+	c.applyDefaults()
+
+	if err := c.Load(); err != nil {
+		t.Fatalf("Load() error: %v", err)
+	}
+
+	if err := c.Save(); err != nil {
+		t.Fatalf("Save() on a fresh config error: %v", err)
+	}
+
+	return c
+}
+
+// TestSetterRejectionDoesNotPoisonTheConfig is the whole of #231.
+//
+// Every setter here assigns to the in-memory config and then validates.
+// When the validation rejects the argument, the rejected value has to go
+// back -- not because the caller sees it (it gets an error either way),
+// but because Config.Save() validates the *whole* config.  A value left
+// behind by a failed setter therefore fails every later save, of every
+// unrelated setting, silently and for the rest of the session.
+//
+// So each case asserts three things in order: the setter reports the
+// error, the getter still reports the old value, and an unrelated save
+// still works.  The third is the one the user feels.
+func TestSetterRejectionDoesNotPoisonTheConfig(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name string
+		// reject calls the setter with an argument its own Validate
+		// refuses.
+		reject func(*Config) error
+		// read reports the value the setter writes, so the rollback is
+		// asserted on the config rather than only on the save.
+		read func(*Config) string
+	}{
+		{
+			name: "scan concurrency",
+			reject: func(c *Config) error {
+				return c.SetScanConcurrency("telepathy")
+			},
+			read: (*Config).GetScanConcurrency,
+		},
+		{
+			name: "theme accent colour",
+			reject: func(c *Config) error {
+				return c.SetThemeAccentColor("not-a-hex")
+			},
+			read: (*Config).GetThemeAccentColor,
+		},
+		{
+			name: "theme background shade",
+			reject: func(c *Config) error {
+				return c.SetThemeBackgroundShade("chartreuse")
+			},
+			read: (*Config).GetThemeBackgroundShade,
+		},
+		{
+			name: "default page",
+			reject: func(c *Config) error {
+				return c.SetDefaultPage("nowhere")
+			},
+			read: (*Config).GetDefaultPage,
+		},
+		{
+			name: "queue fallback",
+			reject: func(c *Config) error {
+				return c.SetQueueFallback("improvise")
+			},
+			read: (*Config).GetQueueFallback,
+		},
+		{
+			name: "favorites icon style",
+			reject: func(c *Config) error {
+				return c.SetFavoritesIconStyle("asterisk")
+			},
+			read: (*Config).GetFavoritesIconStyle,
+		},
+		{
+			name: "track-list columns",
+			reject: func(c *Config) error {
+				// titleArtist is a drawing definition, not a
+				// configurable column (#197), so it is exactly what
+				// the frontend used to be able to send.
+				return c.SetTrackListColumns([]tracklist.Column{
+					{ID: "titleArtist"},
+				})
+			},
+			read: func(c *Config) string {
+				return columnIDs(c.GetTrackListColumns())
+			},
+		},
+		{
+			name: "track-list columns, duplicated",
+			reject: func(c *Config) error {
+				// The route #197 closed was one invalid id; a
+				// duplicate is the one still reachable from a client
+				// that assembles the list itself.
+				return c.SetTrackListColumns([]tracklist.Column{
+					{ID: tracklist.ColTrackName},
+					{ID: tracklist.ColTrackName},
+				})
+			},
+			read: func(c *Config) string {
+				return columnIDs(c.GetTrackListColumns())
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			c := newSavableConfig(t)
+			before := tc.read(c)
+
+			if err := tc.reject(c); err == nil {
+				t.Fatal("setter accepted an invalid value, want an error")
+			}
+
+			if after := tc.read(c); after != before {
+				t.Errorf(
+					"value after a rejected write = %q, want the previous %q",
+					after, before,
+				)
+			}
+
+			// The symptom: an unrelated setting can no longer be saved.
+			if err := c.SetPopupVolume(true); err != nil {
+				t.Errorf("an unrelated setter failed after a rejected write: %v", err)
+			}
+
+			if err := c.Save(); err != nil {
+				t.Errorf("Save() failed after a rejected write: %v", err)
+			}
+		})
+	}
+}
+
+// TestRejectedSetterLeavesNothingOnDisk pairs with the sweep above: the
+// rollback must not be undone by what the file already holds, so a
+// config reloaded from disk after a rejected write agrees with memory.
+func TestRejectedSetterLeavesNothingOnDisk(t *testing.T) {
+	t.Parallel()
+
+	c := newSavableConfig(t)
+
+	if err := c.SetThemeAccentColor("#123456"); err != nil {
+		t.Fatalf("SetThemeAccentColor() error: %v", err)
+	}
+
+	if err := c.SetThemeAccentColor("not-a-hex"); err == nil {
+		t.Fatal("SetThemeAccentColor accepted a non-colour, want an error")
+	}
+
+	reloaded := &Config{logger: slog.Default(), filePath: c.filePath}
+	reloaded.applyDefaults()
+
+	if err := reloaded.Load(); err != nil {
+		t.Fatalf("Load() error: %v", err)
+	}
+
+	if got := reloaded.GetThemeAccentColor(); got != "#123456" {
+		t.Errorf("accent colour on disk = %q, want %q", got, "#123456")
+	}
+
+	if c.GetThemeAccentColor() != reloaded.GetThemeAccentColor() {
+		t.Errorf(
+			"in-memory accent %q disagrees with disk %q after a rejected write",
+			c.GetThemeAccentColor(), reloaded.GetThemeAccentColor(),
+		)
+	}
+}
+
+// TestSetLibraryDirectoryValidatesBeforeAssigning pins the precedent the
+// seven rolled-back setters follow: this one has always built and
+// validated a candidate before assigning, so a bad path never reaches
+// the config at all.
+func TestSetLibraryDirectoryValidatesBeforeAssigning(t *testing.T) {
+	t.Parallel()
+
+	c := newSavableConfig(t)
+	before := c.GetLibraryDirectory()
+
+	if err := c.SetLibraryDirectory(filepath.Join(t.TempDir(), "no-such-dir")); err == nil {
+		t.Fatal("SetLibraryDirectory accepted a missing directory, want an error")
+	}
+
+	if after := c.GetLibraryDirectory(); after != before {
+		t.Errorf("library directory = %q, want the previous %q", after, before)
+	}
+
+	if err := c.Save(); err != nil {
+		t.Errorf("Save() failed after a rejected library directory: %v", err)
+	}
+}
+
+// TestSetViewVisibleRefusesBeforeAssigning covers the other setter left
+// out of the rollback pass: it guards its own argument up front, so
+// GeneralConfig.Validate never sees a view it would reject.
+func TestSetViewVisibleRefusesBeforeAssigning(t *testing.T) {
+	t.Parallel()
+
+	c := newSavableConfig(t)
+
+	if err := c.SetViewVisible("no-such-view", false); err == nil {
+		t.Fatal("SetViewVisible accepted an unknown view, want an error")
+	}
+
+	if err := c.SetViewVisible(c.GetDefaultPage(), false); err == nil {
+		t.Fatal("SetViewVisible hid the launch page, want an error")
+	}
+
+	if err := c.Save(); err != nil {
+		t.Errorf("Save() failed after a refused view visibility change: %v", err)
+	}
+}
+
+// columnIDs renders a column list for comparison in the table above.
+func columnIDs(cols []tracklist.Column) string {
+	ids := make([]byte, 0, len(cols)*8)
+
+	for i, col := range cols {
+		if i > 0 {
+			ids = append(ids, ',')
+		}
+
+		ids = append(ids, col.ID...)
+	}
+
+	return string(ids)
+}

backend/riff/riff.go

@@ -63,12 +63,15 @@ func Parse(r io.Reader) ([]Chunk, error) {
 			return nil, err
 		}
 
-		data := make([]byte, size)
-		if _, err := io.ReadFull(r, data); err != nil {
+		// Copied rather than allocated up front, as ID3Chunk does: the
+		// size is four bytes off the file, so a truncated one is free to
+		// declare a chunk larger than the whole of itself.
+		var data bytes.Buffer
+		if _, err := io.CopyN(&data, r, int64(size)); err != nil {
 			return nil, fmt.Errorf("read chunk data for %q: %w", id, err)
 		}
 
-		chunks = append(chunks, Chunk{ID: id, Data: data})
+		chunks = append(chunks, Chunk{ID: id, Data: data.Bytes()})
 
 		// Odd-length chunks have a padding byte.  Lenient: if the
 		// read fails (e.g. EOF), just break rather than error.

backend/riff/riff_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
+	"runtime"
 	"testing"
 
 	"yellowjacket/backend/riff"
@@ -209,3 +210,45 @@ func TestParse_ReadsEveryChunkInOrder(t *testing.T) {
 		t.Errorf("odd chunk data: got %q, want %q", chunks[1].Data, "INFOodd")
 	}
 }
+
+// A chunk size is four bytes read off the file, so a truncated or
+// malformed WAV is free to declare a chunk larger than the whole of
+// itself.  Parse must grow with what arrives rather than with what was
+// claimed.
+//
+// This measures the allocation instead of the error because the error
+// is the same either way: a build sizing its buffer from the header
+// reports the truncation correctly, having asked the allocator for a
+// gigabyte on the way.  Deliberately not parallel — TotalAlloc is
+// process-wide, and a test paused beside another one is measuring it
+// too.
+func TestParse_DoesNotAllocateWhatAChunkClaims(t *testing.T) {
+	// Large enough that a header-sized buffer is unmistakable, in a
+	// container of a few dozen bytes.
+	const declared = 1 << 30
+
+	var raw bytes.Buffer
+
+	raw.WriteString("RIFF")
+	_ = binary.Write(&raw, binary.LittleEndian, uint32(declared+12))
+	raw.WriteString("WAVE")
+	raw.WriteString("data")
+	_ = binary.Write(&raw, binary.LittleEndian, uint32(declared))
+	raw.WriteString("and then the file ends")
+
+	var before, after runtime.MemStats
+
+	runtime.GC()
+	runtime.ReadMemStats(&before)
+
+	if _, err := riff.Parse(bytes.NewReader(raw.Bytes())); err == nil {
+		t.Fatal("Parse: got nil error for a chunk larger than the file holding it")
+	}
+
+	runtime.ReadMemStats(&after)
+
+	if grew := after.TotalAlloc - before.TotalAlloc; grew > 1<<20 {
+		t.Errorf("Parse allocated %d bytes reading a %d-byte file whose chunk header claimed %d",
+			grew, raw.Len(), declared)
+	}
+}

e2e/specs/queue-overlay.spec.ts

@@ -157,6 +157,62 @@ test.describe('an overlaid queue says it is over the content', () => {
   });
 });
 
+/**
+ * #170 — the other two buttons in that same row.
+ *
+ * Clear queue and Add queue to playlist predate the close button and
+ * were named by a `title` attribute and nothing else. Unlike the
+ * sliders in `control-names.spec.ts`, that is not a *missing* name:
+ * `title` is the last fallback in the accname order, so
+ * `getByRole('button', { name: 'Clear queue' })` matched them before
+ * this fix as well as after it — measured, 1 and 1. A sweep for empty
+ * names cannot see a weak one, which is `a11y.26`'s complaint and the
+ * reason this file could have grown a green test that proved nothing.
+ *
+ * So the name is asserted twice, and the second assertion is the one
+ * that fails on the broken build. Taking the tooltip away and asking
+ * again is the property in words: **the name is not the tooltip**. It
+ * is what makes the button survive content being put inside it later,
+ * and it is the only one of the two a phone has — there is no hover on
+ * the surface #55 turned into a full screen. Measured on `main` before
+ * the fix: 0 and 0.
+ *
+ * Both buttons are disabled here, because the queue starts empty and
+ * naming is not enablement. A disabled button is still in the
+ * accessibility tree, which is exactly where the complaint was.
+ */
+test.describe('the queue header says what its actions do', () => {
+  const ACTIONS = ['Clear queue', 'Add queue to playlist'];
+
+  test('names both of the older actions', async ({ app }) => {
+    await openQueue(app);
+
+    for (const name of ACTIONS) {
+      await expect(
+        app.getByRole('button', { name, exact: true }),
+      ).toHaveCount(1);
+    }
+  });
+
+  test('and the names do not come from the tooltip', async ({ app }) => {
+    await openQueue(app);
+
+    await app.locator('#queue-panel').evaluate((el) => {
+      for (const button of el.shadowRoot!.querySelectorAll(
+        '.header-action-button',
+      )) {
+        button.removeAttribute('title');
+      }
+    });
+
+    for (const name of ACTIONS) {
+      await expect(
+        app.getByRole('button', { name, exact: true }),
+      ).toHaveCount(1);
+    }
+  });
+});
+
 /**
  * The inline panel is the mode that already worked, and the one every
  * other queue spec is written against. It keeps its resize handle and

e2e/specs/queue-selection.spec.ts

@@ -103,12 +103,17 @@ async function queueSixAndOpen(app: Page): Promise<void> {
      *
      * `explore-link` routes a track name to its *album's* page, so a
      * track with no album renders a name that navigates nowhere — and
-     * the fixture library deliberately contains two (`01 Tone A`,
-     * `02 Tone B`). Which tracks arrive first is `audio_files.id`
-     * order, i.e. the order the **scan** inserted them, which depends
-     * on concurrency and directory traversal: locally the first eight
-     * all had albums and the spec passed twice over, and CI rebuilds
-     * its seed with a real scan and got a different eight.
+     * the fixture library deliberately contains two,
+     * `unsorted/no-tags-at-all.mp3` and `unsorted/title-only.mp3`.
+     * (It contained four until #104: the two WAVs under `Field
+     * Recordings/Test Tones` had been tagged on disk all along and
+     * scan in with their album now, so they are ordinary tracks and
+     * not examples of this.) Which tracks arrive first is
+     * `audio_files.id` order, i.e. the order the **scan** inserted
+     * them, which depends on concurrency and directory traversal:
+     * locally the first eight all had albums and the spec passed twice
+     * over, and CI rebuilds its seed with a real scan and got a
+     * different eight.
      *
      * Asking for what the test needs is the fix. It is not a
      * narrowing: every assertion here wants an ordinary track, and

frontend/src/components/bottom-nav/bottom-nav.ts

@@ -4,6 +4,7 @@ import '@awesome.me/webawesome/dist/components/icon/icon.js';
 import '@awesome.me/webawesome/dist/components/drawer/drawer.js';
 import type WaDrawer from '@awesome.me/webawesome/dist/components/drawer/drawer.js';
 import { designTokens } from '../../styles/tokens.css';
+import { sheetScrollFade } from '../../styles/sheet-scroll.css';
 import '../sidebar/app-sidebar.js';
 import { nameDialog } from '@utils/name-dialog';
 import { ICON_PLAYLIST } from '@utils/icon-language';
@@ -167,6 +168,15 @@ export class BottomNav extends LitElement {
             overflow: hidden;
         }
 
+        /* And this list does not fit (#210): measured at 424x439 with
+           the seed's eight destinations, the body is scrollHeight 412
+           against clientHeight 373, and eleven items at 48px would be
+           528 -- the count is the user's since #25. So the sheet says
+           where the fold is, with styles/sheet-scroll.css's two layers
+           rather than a second answer to the question #207 settled for
+           the context sheet. The colour is the local half: the sidebar
+           paints --yj-bg-surface, so the cover does too, or the fade
+           draws the menus' grey across the bottom of this one. */
         wa-drawer::part(body) {
             padding: 0;
             /* A scroll that reaches the end of this list must not
@@ -177,6 +187,23 @@ export class BottomNav extends LitElement {
                on a gesture-navigation phone -- the same allowance the
                bar itself makes above. */
             padding-bottom: env(safe-area-inset-bottom, 0);
+            --yj-sheet-surface: var(--yj-bg-surface, #212529);
+            ${sheetScrollFade}
+        }
+
+        /* And the sheet paints that surface once. The sidebar's host
+           paints the same grey -- which in the shell is the sidebar's
+           own background and here is a second, opaque copy of the
+           sheet's, drawn *over* the body's layers. So the fade was
+           painted and then covered: measured at 424x439 before this
+           rule, the last 32px read a flat 52,58,64 with 39px still
+           below. menu-surface meets the same requirement from the
+           other side, where .context-menu-panel[data-sheet] is
+           background-color: transparent; nothing changes visually
+           here, because the colour underneath is the one being
+           removed. */
+        app-sidebar {
+            background-color: transparent;
         }
 
         /* A sheet is dragged at with a thumb, so it says where its top

frontend/src/components/menu-surface/menu-surface.ts

@@ -65,6 +65,7 @@ import '@awesome.me/webawesome/dist/components/popup/popup.js';
 import '@awesome.me/webawesome/dist/components/dialog/dialog.js';
 import type WaPopup from '@awesome.me/webawesome/dist/components/popup/popup.js';
 
+import { sheetScrollFade } from '../../styles/sheet-scroll.css';
 import { PHONE_QUERY } from '@utils/breakpoints';
 import { nameDialogsIn } from '@utils/name-dialog';
 
@@ -164,46 +165,17 @@ export class MenuSurface extends LitElement {
            and worse when the cut lands on a row boundary, where the
            sheet ends in a clean edge that reads as the end of the list.
 
-           Two layers, and the *order* is what asks the question: a
-           shadow pinned to the bottom of the box (attachment scroll),
-           and over it a cover of the sheet's own colour painted at the
-           end of the *content* (attachment local), which therefore
-           scrolls up over the shadow and hides it exactly when there is
-           nothing more to see. So the affordance is absent on a menu
-           that fits, present the moment one does not, and gone again at
-           the end of the list -- with no scroll listener, no
-           measurement, and nothing reaching into wa-dialog's shadow
-           root for the scroller. background-attachment is Chrome 4;
-           the reference device is Chrome 113.
-
-           **The curve is steep because the rows under it stay live.**
-           A scrim over a menu item is that item's text surface, and
-           this app's rule is that text clears 4.5:1 on every surface it
-           can sit on -- which the light ramp, whose bgElevated is
-           #e9ecef, is what makes non-theoretical. A row is 48px with
-           its label centred, so 32px of scrim that is already down to
-           a quarter strength at 14px reaches y-centre at about 0.06 and
-           spends its weight on the strip below the last legible label.
-           Measured on the dark ramp at x=300, flat 52,58,64 throughout
-           before: 50,56,62 at y=330, 33,37,40 at y=350 and 22,24,27 at
-           the bottom edge, and flat again at the end of the list. The
-           light ramp puts 9.9:1 on the last label. */
+           The two layers that say it live in styles/sheet-scroll.css
+           (#210), because the phone has a second sheet -- bottom-nav's
+           "More" -- which overflows for the same reason and must not
+           arrive at its own answer for what a fold looks like. What is
+           local to this sheet is the colour the cover is painted in:
+           the menus' elevated grey, handed over as --yj-sheet-surface
+           on the same box. */
         wa-dialog::part(body) {
             padding: 0;
-            overflow-y: auto;
-            background:
-                linear-gradient(
-                        var(--yj-bg-elevated, #343a40),
-                        var(--yj-bg-elevated, #343a40)
-                    )
-                    bottom / 100% 32px no-repeat local,
-                linear-gradient(
-                        to top,
-                        rgba(0, 0, 0, 0.6) 0%,
-                        rgba(0, 0, 0, 0.25) 45%,
-                        rgba(0, 0, 0, 0) 100%
-                    )
-                    bottom / 100% 32px no-repeat scroll;
+            --yj-sheet-surface: var(--yj-bg-elevated, #343a40);
+            ${sheetScrollFade}
         }
 
         /* A sheet is dragged at with a thumb, so it says where its top

frontend/src/components/queue-panel/queue-panel.ts

@@ -2201,11 +2201,25 @@ export class QueuePanel
                             `
                             : nothing}
                     </div>
+                    <!-- **Every action here is named by aria-label**, like
+                         the close button #24 added beside them (#170). A
+                         title alone *is* a name, which is why a sweep for
+                         empty names reports these clean and why an
+                         assertion by role and name is green either way --
+                         but it is the weakest one: title is the last
+                         fallback in the accname order, so any content put
+                         inside the button later silently outranks it, and
+                         a phone has no hover to show it as a tooltip.
+
+                         The titles stay. On a desktop they are the tooltip
+                         for an icon-only control, which is a different job
+                         from naming it, and aria-label does not do it. -->
                     <div class="header-actions">
                         <button
                             class="header-action-button"
                             @click=${() => void this.handleClearQueue()}
                             ?disabled=${tracks.length === 0}
+                            aria-label="Clear queue"
                             title="Clear queue"
                         >
                             <wa-icon
@@ -2216,6 +2230,7 @@ export class QueuePanel
                             class="header-action-button add-to-playlist-button"
                             @click=${this.handleAddToPlaylist}
                             ?disabled=${tracks.length === 0}
+                            aria-label="Add queue to playlist"
                             title="Add queue to playlist"
                         >
                             <wa-icon

frontend/src/styles/sheet-scroll.css.ts

@@ -0,0 +1,68 @@
+import { css } from 'lit';
+
+/**
+ * A bottom sheet whose body scrolls says so, in one rule both sheets
+ * read.
+ *
+ * The app has two sheets — `menu-surface`'s context menu (#60) and
+ * `bottom-nav`'s "More" navigation (#71) — and both are capped at 85vh,
+ * because a surface covering the whole screen is a page rather than a
+ * sheet. So both overflow, and both used to overflow *silently*: the
+ * menu at 424x439 with eight items ending at y=470 (#207), the nav
+ * sheet at the same viewport with `scrollHeight` 412 against
+ * `clientHeight` 373 (#210). Where the cut lands on a row boundary the
+ * sheet ends in a clean edge that reads as the end of the list.
+ *
+ * The mechanism is #207's and is unchanged by being shared: two
+ * background layers on the scrolling box, whose *attachments* are the
+ * conditionality. A cover of the sheet's own colour is painted at the
+ * end of the *content* (`local`) over a shadow pinned to the box
+ * (`scroll`), so the cover scrolls up over the shadow exactly when
+ * there is nothing more to see. The fade is therefore absent on a sheet
+ * that fits, present the moment one does not, and gone again at the end
+ * of the list — with no scroll listener, no measurement and nothing
+ * reaching into another component's shadow root for the scroller.
+ * `background-attachment` is Chrome 4; the reference device is
+ * Chrome 113.
+ *
+ * Three things about it are load-bearing.
+ *
+ * **The cover takes the sheet's own colour, from a custom property.**
+ * The two sheets are different greys — the nav sheet paints
+ * `--yj-bg-surface`, because it holds the sidebar and two greys in one
+ * sheet is a seam across the middle of it, while the context sheet
+ * paints the menus' `--yj-bg-elevated`. A shared rule that hard-coded
+ * either would put that seam back on the other one, so the host sets
+ * `--yj-sheet-surface` on the same box and this reads it.
+ *
+ * **The curve is steep because the rows under it stay live.** A scrim
+ * over a menu item is that item's text surface, and this app's rule is
+ * that text clears 4.5:1 on every surface it can sit on — which the
+ * light ramp, whose `bgElevated` is `#e9ecef`, makes non-theoretical. A
+ * row is 48px with its label centred, so 32px of scrim already down to
+ * a quarter strength at 14px spends its weight on the strip below the
+ * last legible label: measured at 9.9:1 on that label on the light ramp,
+ * against 5.0:1 for a linear 48px draft at 0.8. The dark-ramp pixel
+ * table is in `.planning/NOTES.md` (2026-08-23).
+ *
+ * **The box is declared a scroller here too.** `overflow-y: auto` is
+ * part of the same statement rather than left to each host: a fade over
+ * a box that is not the scroller is a fade that never moves, and the
+ * component tier asserts the pair together for that reason.
+ */
+export const sheetScrollFade = css`
+    overflow-y: auto;
+    background:
+        linear-gradient(
+                var(--yj-sheet-surface, #343a40),
+                var(--yj-sheet-surface, #343a40)
+            )
+            bottom / 100% 32px no-repeat local,
+        linear-gradient(
+                to top,
+                rgba(0, 0, 0, 0.6) 0%,
+                rgba(0, 0, 0, 0.25) 45%,
+                rgba(0, 0, 0, 0) 100%
+            )
+            bottom / 100% 32px no-repeat scroll;
+`;

frontend/test/components/bottom-nav.test.ts

@@ -243,6 +243,62 @@ describe('bottom-nav', () => {
     expect(getComputedStyle(body).overscrollBehaviorY).toBe('contain');
   });
 
+  it('says where the fold is, in the sheet\'s own colour', async () => {
+    const el = await fixture<Nav>('bottom-nav');
+    const drawer = shadow<HTMLElement & { open: boolean }>(el, 'wa-drawer');
+
+    if (!drawer) throw new Error('no drawer');
+
+    const shown = once(drawer, 'wa-after-show');
+
+    shadow<HTMLButtonElement>(el, '[data-testid="tab-more"]')?.click();
+    await shown;
+
+    const body = drawer.shadowRoot?.querySelector('[part~="body"]');
+
+    if (!body) throw new Error('no body part to scroll');
+
+    const style = getComputedStyle(body);
+
+    // #210. This list does not fit the phone — measured at 424x439,
+    // `scrollHeight` 412 against `clientHeight` 373 with the seed's
+    // eight destinations — and said nothing about it, which where the
+    // cut lands on a row boundary reads as the end of the list.
+    //
+    // The mechanism is #207's and is asserted the same way: the pair of
+    // attachments *is* the feature. A cover of the sheet's own colour
+    // painted at the end of the content (`local`) over a shadow pinned
+    // to the box (`scroll`), so the fade is absent on a sheet that
+    // fits, present the moment one does not, and gone again at the end.
+    expect(
+      style.backgroundAttachment,
+      'the cover must be local and the shadow must not',
+    ).toBe('local, scroll');
+    expect(style.backgroundPosition).toBe('50% 100%, 50% 100%');
+    expect(style.backgroundSize).toBe('100% 32px, 100% 32px');
+
+    // And the colour is the local half of a shared rule: this sheet
+    // paints the sidebar's `--yj-bg-surface` (#212529) rather than the
+    // menus' elevated grey, or the fade draws the *other* sheet's
+    // colour across the bottom of this one — which is the seam a
+    // shared fragment would otherwise reintroduce.
+    expect(style.backgroundImage).toMatch(
+      /^linear-gradient\(rgb\(33, 37, 41\), rgb\(33, 37, 41\)\)/,
+    );
+
+    // And nothing paints over it. The sidebar's host carries the same
+    // grey, which inside the sheet is a second opaque copy of the
+    // surface drawn on top of these layers -- measured at 424x439 with
+    // the rule removed, the last 32px read a flat 52,58,64 with 39px
+    // still below, so the fade was painted and covered. That is
+    // `.context-menu-panel[data-sheet]`'s transparency, one sheet over.
+    const sidebar = shadow<HTMLElement>(el, 'app-sidebar');
+
+    if (!sidebar) throw new Error('no sidebar');
+
+    expect(getComputedStyle(sidebar).backgroundColor).toBe('rgba(0, 0, 0, 0)');
+  });
+
   it('gives the sheet the whole width, which the sidebar does not take', async () => {
     const el = await fixture<Nav>('bottom-nav');
 

frontend/test/components/menu-surface.test.ts

@@ -254,6 +254,15 @@ describe('menu-surface', () => {
       // Both sit at the bottom, or the cover hides nothing.
       expect(style.backgroundPosition).toBe('50% 100%, 50% 100%');
       expect(style.backgroundSize).toBe('100% 32px, 100% 32px');
+
+      // The layers are shared with `bottom-nav`'s sheet since #210, and
+      // the colour is what each host still says for itself: this one
+      // paints the menus' `--yj-bg-elevated` (#343a40). A shared rule
+      // that hard-coded one grey would draw a seam across the other
+      // sheet, which is why the fragment reads a custom property.
+      expect(style.backgroundImage).toMatch(
+        /^linear-gradient\(rgb\(52, 58, 64\), rgb\(52, 58, 64\)\)/,
+      );
     });
 
     /**