diff --git a/package.json b/package.json
index a21336c..40a1222 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "animatr",
   "private": true,
-  "version": "0.10.1",
+  "version": "0.10.2",
   "type": "module",
   "scripts": {
     "dev": "vite",
diff --git a/src/components/AssetSidebar.vue b/src/components/AssetSidebar.vue
index b2f44e5..1b1301f 100644
--- a/src/components/AssetSidebar.vue
+++ b/src/components/AssetSidebar.vue
@@ -1,6 +1,8 @@
 <script setup lang="ts">
 import { computed, ref, watchEffect } from 'vue'
 import {
+  PhCaretDown,
+  PhCaretRight,
   PhCircle,
   PhCursorClick,
   PhFilmStrip,
@@ -33,6 +35,39 @@ const uploadError = ref<string | null>(null)
 
 const { enabled: showThumbs } = useAssetThumbsPref()
 
+/** Per-section collapsed state, persisted so the user's layout
+ *  survives reloads. Each key is false (expanded) by default —
+ *  that's the desired first-run behaviour per product brief. */
+type AssetSection = 'images' | 'clips' | 'buttons' | 'audio'
+const ASSET_SECTION_KEY = 'animatr:assetSectionsCollapsed'
+
+function readSectionState(): Record<AssetSection, boolean> {
+  try {
+    const raw = localStorage.getItem(ASSET_SECTION_KEY)
+    if (!raw) return { images: false, clips: false, buttons: false, audio: false }
+    const parsed = JSON.parse(raw) as Partial<Record<AssetSection, boolean>>
+    return {
+      images: !!parsed.images,
+      clips: !!parsed.clips,
+      buttons: !!parsed.buttons,
+      audio: !!parsed.audio,
+    }
+  } catch {
+    return { images: false, clips: false, buttons: false, audio: false }
+  }
+}
+
+const collapsedSections = ref<Record<AssetSection, boolean>>(readSectionState())
+
+function toggleSection(key: AssetSection) {
+  collapsedSections.value[key] = !collapsedSections.value[key]
+  try {
+    localStorage.setItem(ASSET_SECTION_KEY, JSON.stringify(collapsedSections.value))
+  } catch {
+    /* noop */
+  }
+}
+
 function addSampleRect() {
   const asset = store.addAsset({
     kind: 'rect',
@@ -389,7 +424,24 @@ function onAssetDragStart(e: DragEvent, asset: Extract<Asset, { kind: 'image' }>
     @dragleave="onPanelDragLeave"
     @drop="onPanelDrop"
   >
-    <h3>Assets</h3>
+    <div class="assets-header">
+      <h3>Assets</h3>
+      <label
+        class="thumbs-switch"
+        v-tooltip="showThumbs ? t('sidebar.thumbnailsHide') : t('sidebar.thumbnailsShow')"
+      >
+        <span class="thumbs-switch-label">{{ t('sidebar.thumbsToggle') }}</span>
+        <input
+          type="checkbox"
+          class="thumbs-switch-input"
+          :checked="showThumbs"
+          @change="showThumbs = ($event.target as HTMLInputElement).checked"
+        />
+        <span class="thumbs-switch-track">
+          <span class="thumbs-switch-knob"></span>
+        </span>
+      </label>
+    </div>
 
     <button class="upload-btn" @click="triggerUpload">
       <PhUploadSimple :size="16" />
@@ -432,18 +484,15 @@ function onAssetDragStart(e: DragEvent, asset: Extract<Asset, { kind: 'image' }>
     />
     <p v-if="uploadError" class="error">{{ uploadError }}</p>
 
-    <div class="lib-header">
-      <h4>{{ t('sidebar.library') }}</h4>
-      <button
-        class="thumb-toggle"
-        v-tooltip="showThumbs ? t('sidebar.thumbnailsHide') : t('sidebar.thumbnailsShow')"
-        @click="showThumbs = !showThumbs"
-      >
-        <PhImageSquare v-if="showThumbs" :size="13" />
-        <PhListBullets v-else :size="13" />
+    <!-- Images -->
+    <div class="section-head-row" :class="{ collapsed: collapsedSections.images }">
+      <button class="section-head" @click="toggleSection('images')">
+        <component :is="collapsedSections.images ? PhCaretRight : PhCaretDown" :size="11" class="section-caret" />
+        <span class="section-title">{{ t('sidebar.images') }}</span>
       </button>
+      <span class="section-count">{{ imageAssets.length }}</span>
     </div>
-    <ul class="assets" :class="{ compact: !showThumbs }">
+    <ul v-show="!collapsedSections.images" class="assets" :class="{ compact: !showThumbs }">
       <li
         v-for="asset in imageAssets"
         :key="asset.id"
@@ -473,13 +522,18 @@ function onAssetDragStart(e: DragEvent, asset: Extract<Asset, { kind: 'image' }>
       <li v-if="!imageAssets.length" class="empty">{{ t('sidebar.noImages') }}</li>
     </ul>
 
-    <div class="lib-header clips-header">
-      <h4>{{ t('sidebar.clips') }}</h4>
-      <button class="thumb-toggle" v-tooltip="t('sidebar.createClipTooltip')" @click="addClip">
+    <!-- Clips -->
+    <div class="section-head-row" :class="{ collapsed: collapsedSections.clips }">
+      <button class="section-head" @click="toggleSection('clips')">
+        <component :is="collapsedSections.clips ? PhCaretRight : PhCaretDown" :size="11" class="section-caret" />
+        <span class="section-title">{{ t('sidebar.clips') }}</span>
+      </button>
+      <button class="section-action" v-tooltip="t('sidebar.createClipTooltip')" @click.stop="addClip">
         <PhPlus :size="12" weight="bold" />
       </button>
+      <span class="section-count">{{ clips.length }}</span>
     </div>
-    <ul class="clips">
+    <ul v-show="!collapsedSections.clips" class="clips">
       <li
         v-for="clip in clips"
         :key="clip.id"
@@ -514,13 +568,18 @@ function onAssetDragStart(e: DragEvent, asset: Extract<Asset, { kind: 'image' }>
       <li v-if="!clips.length" class="empty">{{ t('sidebar.noClips') }}</li>
     </ul>
 
-    <div class="lib-header clips-header">
-      <h4>{{ t('sidebar.buttons') }}</h4>
-      <button class="thumb-toggle" v-tooltip="t('sidebar.createButtonTooltip')" @click="addButton">
+    <!-- Buttons -->
+    <div class="section-head-row" :class="{ collapsed: collapsedSections.buttons }">
+      <button class="section-head" @click="toggleSection('buttons')">
+        <component :is="collapsedSections.buttons ? PhCaretRight : PhCaretDown" :size="11" class="section-caret" />
+        <span class="section-title">{{ t('sidebar.buttons') }}</span>
+      </button>
+      <button class="section-action" v-tooltip="t('sidebar.createButtonTooltip')" @click.stop="addButton">
         <PhPlus :size="12" weight="bold" />
       </button>
+      <span class="section-count">{{ buttonAssets.length }}</span>
     </div>
-    <ul class="clips" :class="{ compact: !showThumbs }">
+    <ul v-show="!collapsedSections.buttons" class="clips" :class="{ compact: !showThumbs }">
       <li
         v-for="ba in buttonAssets"
         :key="ba.id"
@@ -569,10 +628,15 @@ function onAssetDragStart(e: DragEvent, asset: Extract<Asset, { kind: 'image' }>
       <li v-if="!buttonAssets.length" class="empty">{{ t('sidebar.noButtons') }}</li>
     </ul>
 
-    <div class="lib-header clips-header">
-      <h4>{{ t('sidebar.audio') }}</h4>
+    <!-- Audio -->
+    <div class="section-head-row" :class="{ collapsed: collapsedSections.audio }">
+      <button class="section-head" @click="toggleSection('audio')">
+        <component :is="collapsedSections.audio ? PhCaretRight : PhCaretDown" :size="11" class="section-caret" />
+        <span class="section-title">{{ t('sidebar.audio') }}</span>
+      </button>
+      <span class="section-count">{{ audioAssets.length }}</span>
     </div>
-    <ul class="clips">
+    <ul v-show="!collapsedSections.audio" class="clips">
       <li
         v-for="asset in audioAssets"
         :key="asset.id"
@@ -682,27 +746,159 @@ h4 {
   border-radius: var(--radius-sm);
 }
 
-.lib-header {
+.assets-header {
   display: flex;
   align-items: center;
   justify-content: space-between;
-  margin-top: 6px;
+  gap: 10px;
 }
 
-.thumb-toggle {
+/* Compact slide switch labelled "Thumbs" — native checkbox stays hidden
+ * for a11y (keyboard + screen readers), the visible track + knob is
+ * driven purely by the `:checked` state. */
+.thumbs-switch {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  cursor: pointer;
+  user-select: none;
+  font-size: 11px;
+  color: var(--text-dim);
+}
+
+.thumbs-switch-label {
+  font-weight: 500;
+  letter-spacing: 0.01em;
+}
+
+.thumbs-switch-input {
+  /* Keep focus behaviour via the native input; the visual sits next to it. */
+  position: absolute;
+  opacity: 0;
+  width: 0;
+  height: 0;
+  pointer-events: none;
+}
+
+.thumbs-switch-track {
+  position: relative;
+  width: 26px;
+  height: 14px;
+  border-radius: 999px;
+  background: var(--border);
+  transition: background 140ms var(--ease);
+  flex-shrink: 0;
+}
+
+.thumbs-switch-knob {
+  position: absolute;
+  top: 1.5px;
+  left: 1.5px;
+  width: 11px;
+  height: 11px;
+  border-radius: 50%;
+  background: var(--panel);
+  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.35);
+  transition: left 140ms var(--ease), background 140ms var(--ease);
+}
+
+.thumbs-switch-input:checked + .thumbs-switch-track {
+  background: var(--accent);
+}
+
+.thumbs-switch-input:checked + .thumbs-switch-track .thumbs-switch-knob {
+  left: 13.5px;
+  background: #fff;
+}
+
+.thumbs-switch-input:focus-visible + .thumbs-switch-track {
+  outline: 2px solid var(--accent);
+  outline-offset: 1px;
+}
+
+.thumbs-switch:hover .thumbs-switch-track {
+  filter: brightness(1.08);
+}
+
+/* Section rows: unified layout — [caret + title][action?][count]. The
+ * count always sits at the far right so the right column is visually
+ * stable regardless of whether a row has a create-action (+) beside it. */
+.section-head-row {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  margin-top: 4px;
+  border-bottom: 1px solid var(--border);
+}
+
+.section-head-row.collapsed {
+  border-bottom-color: transparent;
+}
+
+.section-head {
+  flex: 1;
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  padding: 6px 4px;
+  background: transparent;
+  border: none;
+  color: var(--text);
+  font-size: 11px;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.04em;
+  cursor: pointer;
+  text-align: left;
+}
+
+.section-head:hover {
+  background: color-mix(in srgb, var(--panel-alt) 60%, transparent);
+}
+
+.section-caret {
+  color: var(--text-dim);
+  flex-shrink: 0;
+}
+
+.section-title {
+  flex: 1;
+}
+
+.section-action {
   width: 22px;
   height: 22px;
   padding: 0;
+  display: inline-flex;
+  align-items: center;
   justify-content: center;
   background: transparent;
-  border: 1px solid var(--border);
+  border: none;
   color: var(--text-dim);
-  border-radius: var(--radius-sm);
+  border-radius: 50%;
+  cursor: pointer;
+  flex-shrink: 0;
+  transition: background 140ms var(--ease), color 140ms var(--ease);
 }
 
-.thumb-toggle:hover:not(:disabled) {
-  background: var(--panel-alt);
-  color: var(--text);
+.section-action:hover {
+  background: var(--accent);
+  color: #fff;
+}
+
+.section-count {
+  font-variant-numeric: tabular-nums;
+  font-weight: 500;
+  font-size: 10px;
+  text-transform: none;
+  letter-spacing: 0;
+  color: var(--text-dim);
+  padding: 1px 6px;
+  border-radius: 999px;
+  background: var(--border);
+  flex-shrink: 0;
+  min-width: 20px;
+  text-align: center;
 }
 
 .assets {
@@ -799,16 +995,21 @@ h4 {
   width: 22px;
   height: 22px;
   padding: 0;
+  display: inline-flex;
+  align-items: center;
   justify-content: center;
   background: transparent;
-  border: 1px solid var(--border);
+  border: none;
   color: var(--text-dim);
+  border-radius: 50%;
   flex-shrink: 0;
+  cursor: pointer;
+  transition: background 140ms var(--ease), color 140ms var(--ease);
 }
 
 .add-layer:hover:not(:disabled) {
-  color: var(--accent);
-  border-color: var(--accent);
+  background: var(--accent);
+  color: #fff;
 }
 
 .empty {
@@ -818,9 +1019,6 @@ h4 {
   justify-content: center;
 }
 
-.clips-header {
-  margin-top: 14px;
-}
 
 .clips {
   list-style: none;
diff --git a/src/components/Timeline.vue b/src/components/Timeline.vue
index c6c0f6a..a448ed9 100644
--- a/src/components/Timeline.vue
+++ b/src/components/Timeline.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch } from 'vue'
+import { computed, nextTick, onBeforeUnmount, onMounted, ref, watch, type ComponentPublicInstance } from 'vue'
 import {
   PhArrowsSplit,
   PhCaretDown,
@@ -33,6 +33,7 @@ import { useSceneStore } from '@/stores/scene'
 import { useClipartStore } from '@/stores/clipart'
 import { importAudioFile } from '@/lib/fileLoader'
 import { audioDragSource, clearAudioDragSource } from '@/composables/useAudioDragSource'
+import { drawWaveform, getWaveformSlot, slicePeaksForClip } from '@/composables/useAudioWaveform'
 import { sampleLayer } from '@/lib/interpolate'
 import { snapToCandidates } from '@/lib/timelineSnap'
 import { confirmDialog, promptDialog } from '@/components/ui'
@@ -1760,6 +1761,42 @@ function audioClipTooltip(clip: AudioClip): string {
   return `${asset.name} · ${audibleDurationOf(clip).toFixed(2)}s`
 }
 
+/** Resolved peaks for a clip's asset — undefined while the decoder
+ *  is still working (first render shows an empty block; waveform
+ *  fades in once computation finishes). */
+function clipPeaks(clip: AudioClip): Float32Array | undefined {
+  const asset = audioAssetById.value.get(clip.audioAssetId)
+  if (!asset || !asset.src) return undefined
+  const slot = getWaveformSlot(asset.id, asset.src)
+  if (!slot || slot.state !== 'ready') return undefined
+  return slicePeaksForClip(slot.peaks, asset.duration, clip.trimStart ?? 0, clip.trimEnd ?? 0)
+}
+
+/** Canvas ref-callback: redraw on every Vue update so the bars track
+ *  the clip's current width (resizes on zoom + trim changes). Cheap
+ *  because peaks are cached and the draw itself is a few hundred
+ *  fillRects. */
+function renderWaveformCanvas(clip: AudioClip) {
+  return (raw: Element | ComponentPublicInstance | null) => {
+    if (!raw || !(raw instanceof HTMLCanvasElement)) return
+    const el = raw
+    const peaks = clipPeaks(clip)
+    if (!peaks) return
+    const parent = el.parentElement
+    if (!parent) return
+    const pr = window.devicePixelRatio || 1
+    const cssW = Math.max(1, parent.clientWidth - 2)
+    const cssH = Math.max(1, parent.clientHeight - 4)
+    const pxW = Math.max(1, Math.round(cssW * pr))
+    const pxH = Math.max(1, Math.round(cssH * pr))
+    if (el.width !== pxW) el.width = pxW
+    if (el.height !== pxH) el.height = pxH
+    el.style.width = cssW + 'px'
+    el.style.height = cssH + 'px'
+    drawWaveform(el, peaks, { pixelRatio: pr })
+  }
+}
+
 /** Would a hypothetical audible block spanning [start, start+length] on
  *  `trackId` collide with an existing clip? Clips on the same track
  *  must not overlap — the user has to pick a second track for parallel
@@ -3211,6 +3248,11 @@ onBeforeUnmount(() => {
                   @pointercancel="onAudioClipPointerUp"
                   @contextmenu="onAudioClipContextMenu($event, clip)"
                 >
+                  <canvas
+                    v-if="clipPeaks(clip)"
+                    class="audio-clip-wave"
+                    :ref="renderWaveformCanvas(clip)"
+                  />
                   <span class="audio-clip-label">
                     {{ audioAssetById.get(clip.audioAssetId)?.name ?? '—' }}
                   </span>
@@ -3824,6 +3866,29 @@ onBeforeUnmount(() => {
 
 .snap-btn.add-kf-btn {
   margin-left: auto;
+  /* Softer-than-the-other-toolbar-buttons treatment: no border, round
+   * hit-area, accent-filled on hover — matches the sidebar's section
+   * `+` buttons so the two "create new thing" affordances read the
+   * same visually. */
+  border: none;
+  border-radius: 50%;
+  background: transparent;
+}
+
+.snap-btn.add-kf-btn:hover:not(:disabled) {
+  background: var(--accent);
+  color: #fff;
+  border-color: transparent;
+}
+
+.snap-btn.add-kf-btn.active {
+  background: var(--accent);
+  color: #fff;
+  border-color: transparent;
+}
+
+.snap-btn.add-kf-btn:disabled {
+  background: transparent;
 }
 
 .mode-toggle {
@@ -3835,7 +3900,15 @@ onBeforeUnmount(() => {
 }
 
 .mode-btn {
-  padding: 3px 8px;
+  /* Match the height of the sibling .snap-btn icons so the timeline
+   * toolbar sits on one visual baseline — the wrapper .mode-toggle's
+   * 1px border is already accounted for by `box-sizing: border-box`
+   * higher up, so the inner 20px hit area stays flush with neighbours. */
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  height: 20px;
+  padding: 0 8px;
   min-width: 22px;
   background: transparent;
   border: none;
@@ -4729,6 +4802,15 @@ onBeforeUnmount(() => {
   user-select: none;
 }
 
+.audio-clip-wave {
+  position: absolute;
+  left: 1px;
+  right: 1px;
+  top: 2px;
+  pointer-events: none;
+  opacity: 0.85;
+}
+
 .audio-clip-block:active,
 .audio-clip-block.moving {
   cursor: grabbing;
@@ -4758,12 +4840,16 @@ onBeforeUnmount(() => {
 }
 
 .audio-clip-label {
+  position: relative;
   font-size: 10px;
   color: var(--text);
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
   pointer-events: none;
+  /* Tiny shadow keeps the text legible over the waveform fill. */
+  text-shadow: 0 0 2px rgba(0, 0, 0, 0.4);
+  z-index: 1;
 }
 
 .clip-block {
diff --git a/src/composables/useAudioWaveform.ts b/src/composables/useAudioWaveform.ts
new file mode 100644
index 0000000..bf63758
--- /dev/null
+++ b/src/composables/useAudioWaveform.ts
@@ -0,0 +1,127 @@
+import { ref } from 'vue'
+
+/**
+ * Peak data for an audio asset — a downsampled array of [0, 1]
+ * amplitudes, one per bucket. Consumers stretch it across the visible
+ * clip block's width. 256 buckets is plenty for the timeline scale;
+ * bumping it only costs memory (peaks never redraw per-frame).
+ */
+const PEAK_BUCKETS = 256
+
+type PeakSlot =
+  | { state: 'pending' }
+  | { state: 'ready'; peaks: Float32Array }
+  | { state: 'error' }
+
+/** Module-scope reactive cache keyed by audio-asset id. Shared across
+ *  every AudioClipBlock — two clips of the same asset render the same
+ *  waveform without recomputing. */
+const cache = ref<Map<string, PeakSlot>>(new Map())
+
+/** Return the peak slot for an asset, kicking off a lazy decode if
+ *  nothing is cached yet. Callers render nothing while `pending`, the
+ *  actual bars once `ready`. */
+export function getWaveformSlot(assetId: string, src: string): PeakSlot | undefined {
+  const existing = cache.value.get(assetId)
+  if (existing) return existing
+  // Mark pending so concurrent callers don't each trigger a decode.
+  cache.value.set(assetId, { state: 'pending' })
+  void decodePeaks(src)
+    .then((peaks) => {
+      // Use a fresh Map to trigger Vue reactivity — mutating the Map's
+      // entry in-place doesn't notify dependent templates.
+      const next = new Map(cache.value)
+      next.set(assetId, { state: 'ready', peaks })
+      cache.value = next
+    })
+    .catch(() => {
+      const next = new Map(cache.value)
+      next.set(assetId, { state: 'error' })
+      cache.value = next
+    })
+  return cache.value.get(assetId)
+}
+
+async function decodePeaks(src: string): Promise<Float32Array> {
+  const response = await fetch(src)
+  const arrayBuffer = await response.arrayBuffer()
+  // prefixed fallback for older Safari; modern Chrome/Firefox expose
+  // AudioContext directly.
+  const Ctx =
+    window.AudioContext ??
+    (window as unknown as { webkitAudioContext?: typeof AudioContext }).webkitAudioContext
+  if (!Ctx) throw new Error('Web Audio API unavailable')
+  const ctx = new Ctx()
+  try {
+    const buffer = await ctx.decodeAudioData(arrayBuffer.slice(0))
+    const channel = buffer.getChannelData(0)
+    const peaks = new Float32Array(PEAK_BUCKETS)
+    const bucketSize = Math.max(1, Math.floor(channel.length / PEAK_BUCKETS))
+    for (let i = 0; i < PEAK_BUCKETS; i++) {
+      let maxAbs = 0
+      const start = i * bucketSize
+      const end = Math.min(start + bucketSize, channel.length)
+      for (let j = start; j < end; j++) {
+        const v = Math.abs(channel[j])
+        if (v > maxAbs) maxAbs = v
+      }
+      peaks[i] = maxAbs
+    }
+    return peaks
+  } finally {
+    void ctx.close()
+  }
+}
+
+/** Clear all cached waveforms. Wired to dispose helpers for tests and
+ *  to scene-load / project-load hooks where the old cache would point
+ *  at orphaned asset ids. */
+export function clearWaveformCache(): void {
+  cache.value = new Map()
+}
+
+/** Slice the peaks array to the portion visible after the clip's
+ *  trimStart / trimEnd. Returns a subarray view so we don't copy;
+ *  drawers iterate but never mutate. */
+export function slicePeaksForClip(
+  peaks: Float32Array,
+  assetDuration: number,
+  trimStart: number,
+  trimEnd: number,
+): Float32Array {
+  if (assetDuration <= 0) return peaks
+  const startFraction = Math.max(0, trimStart) / assetDuration
+  const endFraction = Math.max(startFraction, 1 - Math.max(0, trimEnd) / assetDuration)
+  const startIdx = Math.floor(peaks.length * startFraction)
+  const endIdx = Math.ceil(peaks.length * endFraction)
+  if (endIdx <= startIdx) return peaks.subarray(0, 1)
+  return peaks.subarray(startIdx, endIdx)
+}
+
+/** Render a waveform into a canvas. Draws centred bars (top/bottom
+ *  mirror) with the accent-tinted fill used everywhere else for audio.
+ *  Caller controls DPR scaling — pass `pixelRatio` to redraw sharp on
+ *  high-DPI displays. */
+export function drawWaveform(
+  canvas: HTMLCanvasElement,
+  peaks: Float32Array,
+  opts: { color?: string; pixelRatio?: number } = {},
+): void {
+  const ctx = canvas.getContext('2d')
+  if (!ctx) return
+  const pr = opts.pixelRatio ?? 1
+  const w = canvas.width
+  const h = canvas.height
+  ctx.clearRect(0, 0, w, h)
+  ctx.fillStyle = opts.color ?? 'rgba(14, 165, 233, 0.55)'
+  if (peaks.length === 0) return
+  const midY = h / 2
+  const barW = Math.max(1, Math.round(pr))
+  const colStride = barW + Math.max(0, Math.round(pr * 0.5))
+  for (let x = 0; x < w; x += colStride) {
+    const peakIdx = Math.floor((x / w) * peaks.length)
+    const peak = peaks[peakIdx] ?? 0
+    const barH = Math.max(barW, peak * h)
+    ctx.fillRect(x, midY - barH / 2, barW, barH)
+  }
+}
diff --git a/src/devtools/tests.ts b/src/devtools/tests.ts
index b282084..d93f414 100644
--- a/src/devtools/tests.ts
+++ b/src/devtools/tests.ts
@@ -47,6 +47,12 @@ import Timeline from '@/components/Timeline.vue'
 import AssetSidebar from '@/components/AssetSidebar.vue'
 import FullscreenPreview from '@/components/FullscreenPreview.vue'
 import { createAudioRuntime } from '@/composables/useAudioRuntime'
+import {
+  clearWaveformCache,
+  drawWaveform,
+  getWaveformSlot,
+  slicePeaksForClip,
+} from '@/composables/useAudioWaveform'
 import { vTooltip } from '@/directives/tooltip'
 import { expect, suite, test } from './testRunner'
 
@@ -4646,6 +4652,87 @@ export function registerAllTests(): void {
       handle.unmount()
     })
 
+    test('sections are expanded by default and collapse on header click', async () => {
+      try {
+        localStorage.removeItem('animatr:assetSectionsCollapsed')
+      } catch {
+        /* ignore */
+      }
+      const s = makeFreshStore()
+      s.addAudioAsset({ name: 'a', src: 'data:audio/mp3;x', duration: 1 })
+      const handle = mountComponent(AssetSidebar, {})
+      await nextTick()
+      // All four sections present in the header order.
+      const titles = Array.from(handle.host.querySelectorAll('.section-head-row .section-title'))
+        .map((el) => el.textContent?.trim())
+      expect(titles).toEqual(['Images', 'Clips', 'Buttons', 'Audio'])
+      // Default: audio list is visible.
+      const audioList = handle.host.querySelector('.audio-asset')
+      expect(audioList).toBeTruthy()
+      // Click the Audio section header → list hidden.
+      const audioHead = Array.from(handle.host.querySelectorAll('.section-head-row .section-head'))
+        .find((el) => el.querySelector('.section-title')?.textContent?.trim() === 'Audio') as HTMLButtonElement
+      expect(audioHead).toBeTruthy()
+      audioHead.click()
+      await nextTick()
+      const audioRowAfter = handle.host.querySelector('.audio-asset') as HTMLElement | null
+      expect(audioRowAfter).toBeTruthy()
+      expect(audioRowAfter!.offsetParent).toBeNull()
+      audioHead.click()
+      await nextTick()
+      expect((handle.host.querySelector('.audio-asset') as HTMLElement).offsetParent !== null).toBe(true)
+      handle.unmount()
+    })
+
+    test('section count badge is the last element in every section row (right-aligned)', async () => {
+      // Both actionless rows (Images / Audio) and action-bearing rows
+      // (Clips / Buttons) must end with their count badge so the right
+      // column stays visually aligned across the whole sidebar.
+      try {
+        localStorage.removeItem('animatr:assetSectionsCollapsed')
+      } catch {
+        /* ignore */
+      }
+      makeFreshStore()
+      const handle = mountComponent(AssetSidebar, {})
+      await nextTick()
+      const rows = handle.host.querySelectorAll('.section-head-row')
+      expect(rows.length).toBe(4)
+      for (const row of Array.from(rows)) {
+        const last = row.lastElementChild as HTMLElement
+        expect(last.classList.contains('section-count')).toBe(true)
+      }
+      handle.unmount()
+    })
+
+    test('Library label is gone; "Thumbs" slide switch sits in the Assets header', async () => {
+      makeFreshStore()
+      const handle = mountComponent(AssetSidebar, {})
+      await nextTick()
+      // Nothing in the sidebar still says "Library".
+      expect(handle.host.textContent?.includes('Library')).toBe(false)
+      // The slide switch lives in `.assets-header` next to the <h3> —
+      // pin that structure so the layout doesn't drift back.
+      const header = handle.host.querySelector('.assets-header')
+      expect(header).toBeTruthy()
+      const h3 = header!.querySelector('h3')
+      expect(h3?.textContent?.trim()).toBe('Assets')
+      const label = header!.querySelector('.thumbs-switch .thumbs-switch-label')
+      expect(label?.textContent?.trim()).toBe('Thumbs')
+      // And the underlying checkbox input toggles showThumbs.
+      const input = header!.querySelector('.thumbs-switch-input') as HTMLInputElement
+      expect(input).toBeTruthy()
+      const initial = input.checked
+      input.checked = !initial
+      input.dispatchEvent(new Event('change', { bubbles: true }))
+      await nextTick()
+      // Re-read from a fresh query — the binding updates the checkbox
+      // via its `:checked` attribute on re-render.
+      const input2 = handle.host.querySelector('.thumbs-switch-input') as HTMLInputElement
+      expect(input2.checked).toBe(!initial)
+      handle.unmount()
+    })
+
     test('dragstart on an audio row sets the audio-asset DnD payload', async () => {
       const s = makeFreshStore()
       const asset = s.addAudioAsset({ name: 'beep', src: 'data:audio/mp3;x', duration: 1 })
@@ -6009,6 +6096,54 @@ export function registerAllTests(): void {
       expect(created[0].paused).toBe(true)
     })
 
+    test('getWaveformSlot returns pending the first time, caches subsequent calls', () => {
+      clearWaveformCache()
+      // Un-decodable src — the promise rejects, but the immediate
+      // synchronous return is what we're testing here.
+      const slot1 = getWaveformSlot('asset-x', 'not-a-real-url')
+      expect(slot1?.state).toBe('pending')
+      // Second call while still pending returns the same pending slot
+      // (no new decode kicked off).
+      const slot2 = getWaveformSlot('asset-x', 'not-a-real-url')
+      expect(slot2).toBe(slot1)
+      clearWaveformCache()
+    })
+
+    test('slicePeaksForClip returns only the audible range when trimmed', () => {
+      const full = new Float32Array([0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8])
+      // Asset is 8s long; trimStart=2 → drop first 25%; trimEnd=2 →
+      // drop last 25%. Expect roughly the middle half of the peaks.
+      const slice = slicePeaksForClip(full, 8, 2, 2)
+      expect(slice.length < full.length).toBe(true)
+      // Every value in the slice must be within the middle portion.
+      for (let i = 0; i < slice.length; i++) {
+        expect(slice[i] >= 0.3 - 1e-6 && slice[i] <= 0.6 + 1e-6).toBe(true)
+      }
+    })
+
+    test('slicePeaksForClip with no trim returns the whole array', () => {
+      const full = new Float32Array([0.1, 0.2, 0.3])
+      const slice = slicePeaksForClip(full, 3, 0, 0)
+      expect(slice.length).toBe(full.length)
+    })
+
+    test('drawWaveform paints something onto the canvas (no throw on empty)', () => {
+      const canvas = document.createElement('canvas')
+      canvas.width = 50
+      canvas.height = 20
+      // Non-empty peaks — expect SOME non-zero pixels after drawing.
+      drawWaveform(canvas, new Float32Array([0.5, 0.8, 0.3]), { pixelRatio: 1 })
+      const ctx = canvas.getContext('2d')!
+      const data = ctx.getImageData(0, 0, canvas.width, canvas.height).data
+      let nonZero = 0
+      for (let i = 0; i < data.length; i += 4) {
+        if (data[i + 3] > 0) nonZero++
+      }
+      expect(nonZero > 0).toBe(true)
+      // And a zero-length peaks array must not throw.
+      drawWaveform(canvas, new Float32Array(0))
+    })
+
     test('useAudioRuntime composable wires/unwires cleanly inside a component lifecycle', async () => {
       // The Vue wrapper is a thin shell over createAudioRuntime — mount
       // it via a harness component and expect no throw at mount /
diff --git a/src/i18n/messages.ts b/src/i18n/messages.ts
index 79c20c1..2d7d884 100644
--- a/src/i18n/messages.ts
+++ b/src/i18n/messages.ts
@@ -63,8 +63,10 @@ export const en = {
   sidebar: {
     addFile: 'Add image or audio',
     library: 'Library',
+    images: 'Images',
     thumbnailsHide: 'Hide thumbnails',
     thumbnailsShow: 'Show thumbnails',
+    thumbsToggle: 'Thumbs',
     imageLabel: 'Image',
     addLayerTooltip: 'Insert as layer (or drag to stage)',
     noImages: 'No images imported',