diff --git a/src/App.svelte b/src/App.svelte
index 939cfd188..4bc07f02d 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -21,6 +21,7 @@
   import { hide, toggle } from "@app/lib/modal";
   import * as router from "@app/lib/router";
   import { isLoadedRepoRoute } from "@app/lib/router/definitions";
+  import { toggleSidebar } from "@app/lib/sidebar.svelte";
   import {
     setUnlistenNodeEvents,
     unlistenNodeEvents,
@@ -151,9 +152,13 @@
 
 <style>
   .layout {
-    display: grid;
-    grid-template-columns: auto 1fr;
-    grid-template-rows: 100%;
+    display: flex;
+    height: 100%;
+    overflow: hidden;
+  }
+  .content-pane {
+    flex: 1 1 0;
+    min-width: 0;
     height: 100%;
     overflow: hidden;
   }
@@ -180,6 +185,9 @@
     } else if (auxiliarKey && e.key === ",") {
       e.preventDefault();
       toggle({ component: SettingsView, props: {} });
+    } else if (auxiliarKey && e.key.toLowerCase() === "b") {
+      e.preventDefault();
+      toggleSidebar();
     }
   }} />
 <FullscreenModalPortal />
@@ -213,26 +221,28 @@
     <AppSidebar
       sidebarData={$activeRouteStore.params.sidebarData}
       {activeRepo} />
-    {#if $activeRouteStore.resource === "inbox"}
-      <InboxView {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "guide"}
-      <GuideView {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.home"}
-      <RepoHome {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.commits"}
-      <RepoCommits {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.commit"}
-      <RepoCommit {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.issue"}
-      <Issue {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.issues"}
-      <Issues {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.patch"}
-      <Patch {...$activeRouteStore.params} />
-    {:else if $activeRouteStore.resource === "repo.patches"}
-      <Patches {...$activeRouteStore.params} />
-    {:else}
-      {unreachable($activeRouteStore)}
-    {/if}
+    <div class="content-pane">
+      {#if $activeRouteStore.resource === "inbox"}
+        <InboxView {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "guide"}
+        <GuideView {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.home"}
+        <RepoHome {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.commits"}
+        <RepoCommits {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.commit"}
+        <RepoCommit {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.issue"}
+        <Issue {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.issues"}
+        <Issues {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.patch"}
+        <Patch {...$activeRouteStore.params} />
+      {:else if $activeRouteStore.resource === "repo.patches"}
+        <Patches {...$activeRouteStore.params} />
+      {:else}
+        {unreachable($activeRouteStore)}
+      {/if}
+    </div>
   </div>
 {/if}
diff --git a/src/components/AppSidebar.svelte b/src/components/AppSidebar.svelte
index 6fbd94519..d9dc57d30 100644
--- a/src/components/AppSidebar.svelte
+++ b/src/components/AppSidebar.svelte
@@ -2,10 +2,14 @@
   import type { RepoInfo } from "@bindings/repo/RepoInfo";
 
   import { getCurrentWindow } from "@tauri-apps/api/window";
-  import { onMount } from "svelte";
+  import { onDestroy, onMount, tick } from "svelte";
+  import { backOut } from "svelte/easing";
+  import { fade, scale } from "svelte/transition";
   import { boolean } from "zod";
 
   import { checkRadicleCLI } from "@app/lib/checkRadicleCLI.svelte";
+  import type { FlipSnapshot } from "@app/lib/flip";
+  import { captureFlip, playFlip } from "@app/lib/flip";
   import { hints } from "@app/lib/hints";
   import { dynamicInterval } from "@app/lib/interval";
   import { invoke } from "@app/lib/invoke";
@@ -13,6 +17,20 @@
   import { notificationCount } from "@app/lib/notificationCount.svelte";
   import * as router from "@app/lib/router";
   import type { SidebarData } from "@app/lib/router/definitions";
+  import {
+    commitSidebarWidth,
+    discardSidebarWidthPreview,
+    MIN_SIDEBAR_WIDTH,
+    previewSidebarWidth,
+    RAIL_WIDTH_REM,
+    renderedSidebarWidth,
+    rootFontSize,
+    setSidebarWidth,
+    sidebarCollapsed as collapsed,
+    sidebarResizing,
+    sidebarWidth,
+    toggleSidebar,
+  } from "@app/lib/sidebar.svelte";
   import { updateChecker } from "@app/lib/updateChecker.svelte";
   import useLocalStorage from "@app/lib/useLocalStorage.svelte";
   import { isMac } from "@app/lib/utils";
@@ -32,6 +50,209 @@
 
   const { sidebarData, activeRepo = undefined }: Props = $props();
 
+  const toggleShortcut = isMac() ? "⌘B" : "Ctrl+B";
+  const dragStripHeight = isMac() ? "2.75rem" : "1.75rem";
+
+  const mini = $derived(collapsed.value);
+
+  // The window controls move between a row in the drag strip when expanded and
+  // a column on the rail when collapsed. FLIP carries both the move and the
+  // height their row gives up, which lays out to `auto` and so can't be a CSS
+  // transition.
+  let controlsEl = $state<HTMLElement | undefined>();
+  let controlsFirst: FlipSnapshot | undefined;
+  const CONTROLS_FLIP = { animateHeight: true };
+
+  $effect.pre(() => {
+    // Measure before the DOM reflows for the new state.
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    collapsed.value;
+
+    controlsFirst = captureFlip(controlsEl, CONTROLS_FLIP);
+  });
+
+  $effect(() => {
+    // ...and play once it has.
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    collapsed.value;
+
+    playFlip(controlsEl, controlsFirst, CONTROLS_FLIP);
+  });
+
+  // How far below the minimum width the drag has to go before it collapses,
+  // rather than the edge just sticking at the minimum.
+  const COLLAPSE_DRAG_SLACK_REM = 2;
+
+  // While collapsed, the rail follows the drag at a fraction of its distance so
+  // it feels attached to the pointer, instead of sitting still until the
+  // threshold and then jumping open.
+  const RAIL_STRETCH_FACTOR = 0.35;
+  let railStretch = $state(0);
+
+  // Crossing the threshold is a jump between two widths rather than tracking
+  // the pointer, so the transition is switched back on to carry it. Matches the
+  // width transition on .slot.
+  const SNAP_DURATION_MS = 200;
+  let snapping = $state(false);
+  let snapTimeout: ReturnType<typeof setTimeout> | undefined;
+
+  // Below this a press is a click, not a drag.
+  const DRAG_SLOP_PX = 3;
+
+  function snapWidth() {
+    snapping = true;
+    if (snapTimeout !== undefined) clearTimeout(snapTimeout);
+    snapTimeout = setTimeout(() => (snapping = false), SNAP_DURATION_MS);
+  }
+
+  // Held so unmounting mid-drag doesn't leave listeners and the body class
+  // behind.
+  let endDrag: (() => void) | undefined;
+
+  // Two small drags in quick succession shouldn't also count as a double-press.
+  let lastPressResized = false;
+
+  let slotEl = $state<HTMLElement | undefined>();
+
+  // The width at which nothing truncates and no slack is left over. The style is
+  // restored before this returns, so `max-content` is measured but never
+  // painted.
+  function measureFitWidth(slot: HTMLElement): number {
+    const { maxWidth, transition, width } = slot.style;
+    // Where the sidebar visually is -- mid-animation if it is still opening.
+    // The fit animates from here.
+    const current = slot.getBoundingClientRect().width;
+
+    slot.style.transition = "none";
+    // Lifted to measure the true content width; the result is clamped anyway.
+    slot.style.maxWidth = "none";
+    slot.style.width = "max-content";
+    const fit = slot.getBoundingClientRect().width;
+
+    slot.style.maxWidth = maxWidth;
+    slot.style.width = `${current}px`;
+    // Flushed while the transition is off, so the animation starts from where
+    // the sidebar was and not from `max-content`.
+    void slot.offsetWidth;
+    slot.style.transition = transition;
+    // Back to Svelte's binding, which the caller is about to update; both land
+    // before the next frame, so this animates once.
+    slot.style.width = width;
+
+    return fit;
+  }
+
+  async function fitSidebarToContent() {
+    if (collapsed.value) {
+      collapsed.value = false;
+      // The rail renders different markup; nothing to fit until it is gone.
+      await tick();
+    }
+    if (!slotEl) return;
+    // Rounded up: the measurement is fractional, and landing a hair short would
+    // leave an ellipsis on the row we just fitted to.
+    setSidebarWidth(Math.ceil(measureFitWidth(slotEl)) / rootFontSize());
+  }
+
+  // A second press in quick succession fits the sidebar. Detected here rather
+  // than with `dblclick`, because the pointerdown below is cancelled to stop a
+  // Tauri window drag, which suppresses the mouse events `dblclick` comes from.
+  const DOUBLE_PRESS_MS = 500;
+  const DOUBLE_PRESS_SLOP_PX = 6;
+  let lastPressAt = 0;
+  let lastPressX = 0;
+
+  function isDoublePress(e: PointerEvent): boolean {
+    const paired =
+      // A press that ended in a resize isn't half of a pair.
+      !lastPressResized &&
+      e.timeStamp - lastPressAt < DOUBLE_PRESS_MS &&
+      Math.abs(e.clientX - lastPressX) <= DOUBLE_PRESS_SLOP_PX;
+    // Cleared so a third press starts a new pair instead of fitting again.
+    lastPressAt = paired ? 0 : e.timeStamp;
+    lastPressX = e.clientX;
+    return paired;
+  }
+
+  function onEdgePointerDown(e: PointerEvent) {
+    // Primary button only; a right-click here would otherwise start a drag.
+    if (e.button !== 0) return;
+    e.preventDefault();
+
+    if (isDoublePress(e)) {
+      void fitSidebarToContent();
+      return;
+    }
+
+    const edge = e.currentTarget as HTMLElement;
+    // Capture so the drag survives the pointer leaving the window: a pointerup
+    // out there never arrives, and the resize would never end.
+    edge.setPointerCapture(e.pointerId);
+
+    sidebarResizing.value = true;
+    document.body.classList.add("resizing-sidebar");
+
+    const startX = e.clientX;
+    // From the rail's own width when collapsed, so reopening starts where the
+    // edge visually sits rather than at the stored expanded width.
+    const startWidth = collapsed.value ? RAIL_WIDTH_REM : sidebarWidth.value;
+    const pxPerRem = rootFontSize();
+    let dragged = false;
+
+    const onMove = (ev: PointerEvent) => {
+      if (!dragged) {
+        if (Math.abs(ev.clientX - startX) <= DRAG_SLOP_PX) return;
+        dragged = true;
+      }
+      const width = startWidth + (ev.clientX - startX) / pxPerRem;
+      // One boundary serves both directions: below it the sidebar is collapsed,
+      // above it expanded, so a single drag can cross either way.
+      const collapse = width < MIN_SIDEBAR_WIDTH - COLLAPSE_DRAG_SLACK_REM;
+      if (collapsed.value !== collapse) {
+        collapsed.value = collapse;
+        snapWidth();
+      }
+      if (collapse) {
+        railStretch = Math.max(
+          0,
+          (width - RAIL_WIDTH_REM) * RAIL_STRETCH_FACTOR,
+        );
+        // Anything previewed before the threshold was crossed is on the way to
+        // collapsing, not a width to remember.
+        discardSidebarWidthPreview();
+      } else {
+        railStretch = 0;
+        // Off storage; persisted once when the drag ends.
+        previewSidebarWidth(width);
+      }
+    };
+
+    const finish = () => {
+      endDrag = undefined;
+      edge.removeEventListener("pointermove", onMove);
+      edge.removeEventListener("pointerup", finish);
+      edge.removeEventListener("pointercancel", finish);
+      if (edge.hasPointerCapture(e.pointerId)) {
+        edge.releasePointerCapture(e.pointerId);
+      }
+      sidebarResizing.value = false;
+      railStretch = 0;
+      document.body.classList.remove("resizing-sidebar");
+      commitSidebarWidth();
+      lastPressResized = dragged;
+    };
+
+    endDrag = finish;
+    edge.addEventListener("pointermove", onMove);
+    edge.addEventListener("pointerup", finish);
+    edge.addEventListener("pointercancel", finish);
+  }
+
+  onDestroy(() => {
+    endDrag?.();
+    if (snapTimeout !== undefined) clearTimeout(snapTimeout);
+  });
+
   const firstLaunchStorage = useLocalStorage(
     "appFirstLaunch",
     boolean(),
@@ -96,23 +317,109 @@
 </script>
 
 <style>
-  .sidebar {
-    display: flex;
-    flex-direction: column;
+  .slot {
+    position: relative;
     height: 100%;
     min-height: 0;
-    width: 16.5rem;
-    border-right: 1px solid var(--color-border-subtle);
+    flex-shrink: 0;
+    transition: width 0.2s ease;
+    /* Backstop for MAX_VIEWPORT_FRACTION, for when the window is resized after
+       the width was set. */
+    max-width: 40vw;
   }
-  .top {
-    padding: 0 0.5rem;
-    height: 1.75rem;
+  .slot.resizing {
+    transition: none;
+  }
+
+  .sidebar {
+    /* Containing block for the window controls and the resize edge. Isolated so
+       both layer against the sidebar, not against portalled popovers. */
+    position: relative;
+    isolation: isolate;
+    width: 100%;
+    height: 100%;
     display: flex;
-    align-items: center;
-    justify-content: flex-end;
-    gap: 0.25rem;
+    flex-direction: column;
+    min-height: 0;
+    border-right: 1px solid var(--color-border-subtle);
+    background-color: var(--color-surface-base);
+    transition: background-color 0.2s ease;
+  }
+  .sidebar.mini {
+    background-color: var(--color-surface-canvas);
+  }
+  /* Carries the square-up below. */
+  .sidebar :global(.button) {
+    transition: width 0.2s ease;
+  }
+  /* The collapse contract: `.label` anywhere in the sidebar is text that gives
+     up its space on the rail. Opted into by class alone, so a child that wants
+     its text to survive the collapse must not use it. Non-interactive, so the
+     part overflowing the collapsed square is not a phantom hover target. */
+  .sidebar :global(.label) {
+    white-space: nowrap;
+    pointer-events: none;
+    transition: opacity 0.2s ease;
+  }
+  /* A label still fading at full width would push its icon off the rail's
+     centre line, so it gives up the space too. */
+  .sidebar.mini :global(.label) {
+    opacity: 0;
+    width: 0;
+    min-width: 0;
+    overflow: hidden;
+  }
+
+  .drag-strip {
     flex-shrink: 0;
   }
+  .controls {
+    display: flex;
+    align-items: flex-start;
+    gap: 0.25rem;
+    padding: 0 0.5rem 0.25rem;
+    flex-shrink: 0;
+    /* Height comes from the content -- zero when expanded, the button column
+       when collapsed -- and is animated by the FLIP in the script, since a CSS
+       transition can't reach `auto`. Top-aligned in both states so the toggle
+       stays put while the rest reflow. */
+  }
+  .window-controls {
+    display: flex;
+    gap: 0.25rem;
+  }
+  /* Expanded, the controls lift into the drag strip beside the traffic lights.
+     They stay in the row's DOM so the same elements survive the toggle and can
+     glide into the rail's column. */
+  .sidebar:not(.mini) .window-controls {
+    position: absolute;
+    top: 0;
+    right: 0.5rem;
+    /* Centred on the traffic lights, not on the strip, which is taller and
+       would sit these too low. Their centre is ~16px down, matched here by a
+       2rem box; macOS draws them, so it can't be read from the page. */
+    height: 2rem;
+    align-items: center;
+  }
+  /* Nothing left in flow once they lift, so dropping the padding collapses the
+     row to nothing and gives the space back to the nav. */
+  .sidebar:not(.mini) .controls {
+    padding: 0;
+  }
+  .sidebar.mini .controls,
+  .sidebar.mini .window-controls {
+    flex-direction: column;
+    gap: 0.125rem;
+    align-items: center;
+  }
+
+  .body {
+    flex: 1;
+    min-height: 0;
+    display: flex;
+    flex-direction: column;
+  }
+
   .nav {
     flex: 1;
     overflow: visible;
@@ -128,6 +435,37 @@
     flex-direction: column;
     gap: 0.25rem;
   }
+  /* The rail is one centred column. */
+  .sidebar.mini .nav {
+    align-items: center;
+  }
+  /* The rail carries navigation only. */
+  .sidebar.mini .bottom {
+    display: none;
+  }
+  /* One 2rem square per item, so the hover/selected highlight is a uniform
+     square rather than a full-width bar. */
+  .sidebar.mini :global(.nav-item),
+  .sidebar.mini :global(.button),
+  .sidebar.mini :global(.filter-button) {
+    width: 2rem;
+    min-width: 2rem;
+    height: 2rem;
+    box-sizing: border-box;
+    border-radius: var(--border-radius-sm);
+    /* Otherwise held open by the zero-width label. */
+    gap: 0;
+  }
+  /* Nav items are left out: their 0.5rem padding either side of a 1rem icon
+     already centres it in the 2rem square. */
+  .sidebar.mini :global(.button),
+  .sidebar.mini :global(.filter-button) {
+    justify-content: center;
+  }
+  /* `margin-left: auto` on a centred square drags the icon off centre. */
+  .sidebar.mini :global(.update-badge) {
+    display: none;
+  }
   .nav-item {
     display: flex;
     align-items: center;
@@ -139,6 +477,8 @@
     cursor: pointer;
     width: 100%;
     text-decoration: none;
+    white-space: nowrap;
+    transition: width 0.2s ease;
   }
   .nav-item:hover {
     background-color: var(--color-surface-subtle);
@@ -151,6 +491,7 @@
   }
   .icon {
     color: var(--color-text-tertiary);
+    flex-shrink: 0;
   }
   .update-badge {
     margin-left: auto;
@@ -201,116 +542,183 @@
     display: flex;
     gap: 0.25rem;
   }
+
+  /* Inside the sidebar rather than straddling the border, which put an
+     invisible grab target over the edge of the content pane. Drag resizes and a
+     double-press fits; collapsing is the toggle button's job. */
+  .edge {
+    position: absolute;
+    top: 0;
+    right: 0;
+    width: 6px;
+    height: 100%;
+    /* Above its siblings; the isolated stacking context keeps it below
+       popovers and modals. */
+    z-index: 1;
+    cursor: col-resize;
+  }
+  /* The pointer leaves the edge as soon as the drag starts. */
+  :global(body.resizing-sidebar),
+  :global(body.resizing-sidebar *) {
+    cursor: col-resize !important;
+  }
 </style>
 
-<div class="sidebar">
-  <div
-    class="top"
-    style:height={isMac() ? "2.75rem" : "1.75rem"}
-    data-tauri-drag-region>
-    <Button
-      variant="naked"
-      onclick={() => window.history.back()}
-      stylePadding="0 4px">
-      <span class="icon"><Icon name="arrow-left" /></span>
-    </Button>
-    <Button
-      variant="naked"
-      onclick={() => window.history.forward()}
-      stylePadding="0 4px">
-      <span class="icon"><Icon name="arrow-right" /></span>
-    </Button>
-    <Button
-      variant="naked"
-      title="Reload"
-      onclick={() => window.location.reload()}
-      stylePadding="0 4px">
-      <span class="icon"><Icon name="refresh" /></span>
-    </Button>
-  </div>
+<div
+  bind:this={slotEl}
+  class="slot"
+  class:resizing={sidebarResizing.value && !snapping}
+  style:width={collapsed.value
+    ? `${RAIL_WIDTH_REM + railStretch}rem`
+    : `${renderedSidebarWidth.value}rem`}>
+  <div class="sidebar" class:mini role="navigation">
+    <div
+      class="drag-strip"
+      style:height={dragStripHeight}
+      data-tauri-drag-region>
+    </div>
 
-  <div class="nav">
-    <IdentityButton config={sidebarData.config} />
+    <div class="controls" bind:this={controlsEl}>
+      <span class="window-controls">
+        <Button
+          variant="naked"
+          title="{collapsed.value
+            ? 'Expand'
+            : 'Collapse'} sidebar ({toggleShortcut})"
+          keyShortcuts={isMac() ? "Meta+b" : "Control+b"}
+          onclick={toggleSidebar}
+          stylePadding="0 4px">
+          <span class="icon"><Icon name="sidebar-left" /></span>
+        </Button>
+        <Button
+          variant="naked"
+          onclick={() => window.history.back()}
+          stylePadding="0 4px">
+          <span class="icon"><Icon name="arrow-left" /></span>
+        </Button>
+        <Button
+          variant="naked"
+          onclick={() => window.history.forward()}
+          stylePadding="0 4px">
+          <span class="icon"><Icon name="arrow-right" /></span>
+        </Button>
+        <Button
+          variant="naked"
+          title="Reload"
+          onclick={() => window.location.reload()}
+          stylePadding="0 4px">
+          <span class="icon"><Icon name="refresh" /></span>
+        </Button>
+      </span>
+    </div>
 
-    <a
-      class="nav-item"
-      class:active={isInbox()}
-      href={router.routeToPath({ resource: "inbox" })}>
-      <span class="icon"><Icon name="inbox" /></span>
-      Inbox
-      {#if notificationCount.value > 0}
-        <span class="global-counter-badge">{notificationCount.value}</span>
-      {/if}
-    </a>
+    <div class="body">
+      <div class="nav">
+        {#if !mini}
+          <IdentityButton config={sidebarData.config} />
+        {/if}
 
-    <SidebarRepoList
-      initialRepos={sidebarData.repos}
-      initialSeededNotReplicated={sidebarData.seededNotReplicated}
-      config={sidebarData.config}
-      {activeRepo} />
-  </div>
+        <a
+          class="nav-item"
+          class:active={isInbox()}
+          title="Inbox"
+          href={router.routeToPath({ resource: "inbox" })}>
+          <span class="icon"><Icon name="inbox" /></span>
+          <span class="label">Inbox</span>
+          {#if !mini && notificationCount.value > 0}
+            <span
+              class="global-counter-badge"
+              in:scale={{ duration: 200, easing: backOut, start: 0 }}
+              out:fade={{ duration: 200 }}>
+              {notificationCount.value}
+            </span>
+          {/if}
+        </a>
 
-  <div class="bottom">
-    {#if !hints.isDismissed("guide")}
-      {#if confirmingGuideDismiss}
-        <div class="guide-confirm txt-body-s-regular">
-          <div>
-            Hide the Guide? You can bring it back from Hidden hints in Settings.
-          </div>
-          <div class="guide-confirm-actions">
-            <Button
-              variant="ghost"
-              styleHeight="1.75rem"
-              styleWidth="100%"
-              onclick={() => {
-                hints.dismiss("guide");
-                confirmingGuideDismiss = false;
-              }}>
-              Hide
-            </Button>
-            <Button
-              variant="outline"
-              styleHeight="1.75rem"
-              styleWidth="100%"
-              onclick={() => (confirmingGuideDismiss = false)}>
-              Cancel
-            </Button>
-          </div>
-        </div>
-      {:else}
-        <div class="guide-item">
-          <Button
-            variant="naked"
-            styleWidth="100%"
-            styleJustifyContent="flex-start"
-            active={isGuide()}
-            onclick={() => router.push({ resource: "guide" })}>
-            <span class="icon"><Icon name="guide" /></span>
-            Guide
-          </Button>
-          <button
-            type="button"
-            class="guide-dismiss"
-            title="Hide Guide"
-            aria-label="Hide Guide"
-            onclick={() => (confirmingGuideDismiss = true)}>
-            <Icon name="close" />
-          </button>
-        </div>
-      {/if}
-    {/if}
-    <Button
-      variant="naked"
-      styleWidth="100%"
-      styleJustifyContent="flex-start"
-      active={isSettings()}
-      onclick={() => show({ component: SettingsView, props: {} })}>
-      <span class="icon"><Icon name="settings" /></span>
-      Settings
-      {#if updateChecker.newVersion}
-        <span class="update-badge">New Update</span>
-      {/if}
-    </Button>
-    <NodeStatusButton />
+        <SidebarRepoList
+          initialRepos={sidebarData.repos}
+          initialSeededNotReplicated={sidebarData.seededNotReplicated}
+          config={sidebarData.config}
+          {activeRepo} />
+      </div>
+
+      <div class="bottom">
+        {#if !hints.isDismissed("guide")}
+          {#if confirmingGuideDismiss && !mini}
+            <div class="guide-confirm txt-body-s-regular">
+              <div>
+                Hide the Guide? You can bring it back from Hidden hints in
+                Settings.
+              </div>
+              <div class="guide-confirm-actions">
+                <Button
+                  variant="ghost"
+                  styleHeight="1.75rem"
+                  styleWidth="100%"
+                  onclick={() => {
+                    hints.dismiss("guide");
+                    confirmingGuideDismiss = false;
+                  }}>
+                  Hide
+                </Button>
+                <Button
+                  variant="outline"
+                  styleHeight="1.75rem"
+                  styleWidth="100%"
+                  onclick={() => (confirmingGuideDismiss = false)}>
+                  Cancel
+                </Button>
+              </div>
+            </div>
+          {:else}
+            <div class="guide-item">
+              <Button
+                variant="naked"
+                title="Guide"
+                styleWidth={mini ? "2rem" : "100%"}
+                styleJustifyContent="flex-start"
+                active={isGuide()}
+                onclick={() => router.push({ resource: "guide" })}>
+                <span class="icon"><Icon name="guide" /></span>
+                <span class="label">Guide</span>
+              </Button>
+              {#if !mini}
+                <button
+                  type="button"
+                  class="guide-dismiss"
+                  title="Hide Guide"
+                  aria-label="Hide Guide"
+                  onclick={() => (confirmingGuideDismiss = true)}>
+                  <Icon name="close" />
+                </button>
+              {/if}
+            </div>
+          {/if}
+        {/if}
+        <Button
+          variant="naked"
+          title="Settings"
+          styleWidth={mini ? "2rem" : "100%"}
+          styleJustifyContent="flex-start"
+          active={isSettings()}
+          onclick={() => show({ component: SettingsView, props: {} })}>
+          <span class="icon"><Icon name="settings" /></span>
+          <span class="label">Settings</span>
+          {#if updateChecker.newVersion}
+            <span class="update-badge">New Update</span>
+          {/if}
+        </Button>
+        <NodeStatusButton />
+      </div>
+    </div>
+
+    <div
+      class="edge"
+      title="Drag to resize, double-click to fit"
+      onpointerdown={onEdgePointerDown}
+      role="separator"
+      aria-orientation="vertical"
+      tabindex="-1">
+    </div>
   </div>
 </div>
diff --git a/src/components/IdentityButton.svelte b/src/components/IdentityButton.svelte
index 7746aa283..88387fd72 100644
--- a/src/components/IdentityButton.svelte
+++ b/src/components/IdentityButton.svelte
@@ -33,10 +33,15 @@
 
 <Popover placement="bottom-start" bind:expanded={popoverExpanded}>
   {#snippet toggle(onclick)}
-    <Button variant="naked" active={popoverExpanded} {onclick}>
+    <Button
+      variant="naked"
+      styleWidth="100%"
+      styleJustifyContent="flex-start"
+      active={popoverExpanded}
+      {onclick}>
       <UserAvatar nodeId={config.publicKey} styleWidth="1rem" />
-      {config.alias}
-      <span style:color="var(--color-text-tertiary)">
+      <span class="label">{config.alias}</span>
+      <span class="label" style:color="var(--color-text-tertiary)">
         <Icon name={popoverExpanded ? "chevron-up" : "chevron-down"} />
       </span>
     </Button>
diff --git a/src/components/SidebarRepoList.svelte b/src/components/SidebarRepoList.svelte
index 8642aedb5..135d35da2 100644
--- a/src/components/SidebarRepoList.svelte
+++ b/src/components/SidebarRepoList.svelte
@@ -43,10 +43,12 @@
 
   import { onMount } from "svelte";
   import { flip } from "svelte/animate";
-  import { cubicOut } from "svelte/easing";
-  import { crossfade } from "svelte/transition";
+  import { backOut, cubicOut } from "svelte/easing";
+  import { crossfade, fade, scale, slide } from "svelte/transition";
 
   import { nodeRunning } from "@app/lib/events";
+  import type { FlipSnapshot } from "@app/lib/flip";
+  import { captureFlip, playFlip } from "@app/lib/flip";
   import { dynamicInterval, resetDynamicInterval } from "@app/lib/interval";
   import {
     cachedListReposSummary,
@@ -56,6 +58,7 @@
   } from "@app/lib/invoke";
   import { show } from "@app/lib/modal";
   import * as router from "@app/lib/router";
+  import { sidebarCollapsed } from "@app/lib/sidebar.svelte";
   import {
     explorerHost,
     explorerUrl,
@@ -116,6 +119,15 @@
     }
   });
 
+  // Collapsing discards the filter, so re-expanding comes back to a plain
+  // header rather than a stale query.
+  $effect(() => {
+    if (sidebarCollapsed.value) {
+      filterOpen = false;
+      filterQuery = "";
+    }
+  });
+
   $effect(() => {
     if (seededNotReplicated.length > 0) {
       dynamicInterval("seededNotReplicated", reloadRepos, 5_000);
@@ -158,6 +170,29 @@
     repos.filter(r => !pinnedRepoIds.value.includes(r.rid)).length,
   );
 
+  // FLIP the "All Repos" header's icon and buttons, plus its own height, as it
+  // reflows on collapse. Measured relative to the header, so its downward shift
+  // (the controls growing above it) is left to the shared layout transition.
+  let allReposHeaderEl = $state<HTMLElement | undefined>();
+  let headerFirst: FlipSnapshot | undefined;
+  const HEADER_FLIP = { selector: "[data-flip]", animateHeight: true };
+
+  $effect.pre(() => {
+    // Measure before the DOM reflows for the new state.
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    sidebarCollapsed.value;
+
+    headerFirst = captureFlip(allReposHeaderEl, HEADER_FLIP);
+  });
+
+  $effect(() => {
+    // ...and play once it has.
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    sidebarCollapsed.value;
+
+    playFlip(allReposHeaderEl, headerFirst, HEADER_FLIP);
+  });
+
   const ANIMATION_DURATION_MS = 220;
   let animatingPinnedList = $state(false);
   let animationTimeout: ReturnType<typeof setTimeout> | undefined;
@@ -337,6 +372,7 @@
     justify-content: space-between;
     cursor: pointer;
     user-select: none;
+    overflow: hidden;
   }
   .section-header-label {
     display: flex;
@@ -350,6 +386,10 @@
     align-items: center;
     gap: 0.25rem;
   }
+  /* No room on the rail; the repo rows below stand on their own there. */
+  .section-header.mini {
+    display: none;
+  }
 
   .filter-button {
     display: flex;
@@ -394,6 +434,19 @@
     text-decoration: none;
     user-select: none;
     -webkit-user-select: none;
+    transition: width 0.2s ease;
+  }
+  .nav-item .txt-overflow {
+    min-width: 0;
+  }
+  /* No room on the rail, and reordering is off there, so rows stay plain
+     links. */
+  :global(.sidebar.mini) .row-actions {
+    display: none;
+  }
+  /* Centred on the rail. */
+  :global(.sidebar.mini) .repos-list {
+    align-items: center;
   }
   .nav-item :global(img),
   .nav-item :global(svg) {
@@ -409,8 +462,20 @@
   .nav-item .global-counter-badge {
     margin-left: auto;
   }
+  /* Rows unroll from behind the repo they belong to -- the `slide` transition
+     clips them while the height animates -- rather than appearing in place. */
+  .sub-items {
+    display: flex;
+    flex-direction: column;
+    gap: 0.25rem;
+    padding-top: 0.25rem;
+  }
   .sub-item {
     padding-left: 2rem;
+    transition: padding-left 0.2s ease;
+  }
+  .sub-item.mini {
+    padding-left: 0.5rem;
   }
 
   .pending-item {
@@ -436,12 +501,19 @@
     background-color: var(--color-surface-mid);
   }
 
+  /* Out of flow: hidden, they still reserved a button's width on every row.
+     They sit over the end of the name instead, on the row's own fill. */
   .nav-item .row-actions {
     visibility: hidden;
-    margin-left: auto;
+    position: absolute;
+    top: 0;
+    bottom: 0;
+    right: 0.5rem;
     display: flex;
     align-items: center;
     gap: 0.125rem;
+    padding-left: 0.25rem;
+    background-color: var(--color-surface-subtle);
     color: var(--color-text-tertiary);
   }
   .nav-item:hover .row-actions,
@@ -473,11 +545,13 @@
     cursor: grab;
   }
 
+  /* No gap: the sub-items carry their own top padding, so it animates open with
+     them. A gap here would appear and vanish with the mount, jumping either
+     side of the transition. */
   .repo-row-group {
     position: relative;
     display: flex;
     flex-direction: column;
-    gap: 0.25rem;
   }
   .repo-row-group.drop-before::before,
   .repo-row-group.drop-after::after {
@@ -524,6 +598,31 @@
   .icon {
     color: var(--color-text-tertiary);
   }
+  .repo-icon {
+    position: relative;
+    display: inline-flex;
+  }
+  /* Hover swaps the repo icon for arrows showing what a click will do. Keyed
+     off the label so the buttons beside it don't trigger it. */
+  .icon-stack {
+    display: grid;
+  }
+  .icon-default,
+  .icon-hover {
+    grid-area: 1 / 1;
+    transition: opacity 150ms ease;
+  }
+  .icon-hover {
+    opacity: 0;
+  }
+  .section-header-label:hover .icon-default,
+  .section-header:focus-visible .icon-default {
+    opacity: 0;
+  }
+  .section-header-label:hover .icon-hover,
+  .section-header:focus-visible .icon-hover {
+    opacity: 1;
+  }
 
   .menu-item {
     display: flex;
@@ -558,7 +657,7 @@
   }
 </style>
 
-{#if seededNotReplicated.length > 0}
+{#if seededNotReplicated.length > 0 && !sidebarCollapsed.value}
   <div
     class="section-header"
     onclick={() => (fetchingExpanded.value = !fetchingExpanded.value)}
@@ -622,7 +721,9 @@
 </div>
 
 <div
+  bind:this={allReposHeaderEl}
   class="section-header"
+  class:mini={sidebarCollapsed.value}
   onclick={() => {
     if (!filterOpen) {
       reposExpanded.value = !reposExpanded.value;
@@ -671,7 +772,31 @@
     </span>
   {:else}
     <span class="section-header-label">
-      <span onclick={e => e.stopPropagation()} role="none">
+      <span class="icon repo-icon" data-flip>
+        <span class="icon-stack">
+          <span class="icon-default"><Icon name="repository" /></span>
+          <span class="icon-hover">
+            <Icon
+              name={reposExpanded.value
+                ? "collapse-vertical"
+                : "expand-vertical"} />
+          </span>
+        </span>
+      </span>
+      <span class="label">All Repos</span>
+      {#if !sidebarCollapsed.value && unpinnedReposCount > 1}
+        <span
+          class="global-counter-badge"
+          in:scale={{ duration: 200, easing: backOut, start: 0 }}
+          out:fade={{ duration: 200 }}>
+          {unpinnedReposCount}
+        </span>
+      {/if}
+    </span>
+  {/if}
+  <span class="section-header-actions">
+    {#if !filterOpen}
+      <span data-flip onclick={e => e.stopPropagation()} role="none">
         <button
           class="filter-button"
           title="Filter repos"
@@ -680,20 +805,15 @@
             filterOpen = true;
             reposExpanded.value = true;
           }}>
-          <span class="icon"><Icon name="filter" /></span>
+          <span class="icon"><Icon name="search" /></span>
         </button>
       </span>
-      All Repos
-      {#if unpinnedReposCount > 1}
-        <span class="global-counter-badge">{unpinnedReposCount}</span>
-      {/if}
-      <span class="icon">
-        <Icon name={reposExpanded.value ? "chevron-down" : "chevron-up"} />
-      </span>
-    </span>
-  {/if}
-  <span class="section-header-actions">
-    <span onclick={e => e.stopPropagation()} role="none">
+    {/if}
+    <span
+      class="add-repo-action"
+      data-flip
+      onclick={e => e.stopPropagation()}
+      role="none">
       <AddRepoButton reload={reloadRepos} {repos} {seededNotReplicated} />
     </span>
   </span>
@@ -707,12 +827,14 @@
     class:context-active={contextMenu?.repo.rid === repo.rid}
     class:dragging={pinned && drag.draggingRid === repo.rid}
     draggable="false"
-    onmousedown={pinned ? e => drag.onMouseDown(e, repo.rid) : undefined}
-    onclick={pinned ? drag.onClick : undefined}
+    onmousedown={pinned && !sidebarCollapsed.value
+      ? e => drag.onMouseDown(e, repo.rid)
+      : undefined}
+    onclick={pinned && !sidebarCollapsed.value ? drag.onClick : undefined}
     oncontextmenu={e => openContextMenu(e, repo)}
     href={router.routeToPath({ resource: "repo.home", rid: repo.rid })}>
     <RepoAvatar name={repo.name} rid={repo.rid} styleWidth="1rem" />
-    <span class="txt-overflow">{repo.name}</span>
+    <span class="txt-overflow label">{repo.name}</span>
     <span
       class="row-actions"
       role="none"
@@ -735,28 +857,32 @@
   </a>
   {#if activeRid() === repo.rid}
     {@const activeProject = activeRepo?.payloads["xyz.radicle.project"]}
-    {@render subItem(
-      router.routeToPath({
-        resource: "repo.issues",
-        rid: repo.rid,
-        status: "open",
-      }),
-      "issue",
-      "Issues",
-      isIssues(repo.rid),
-      activeProject?.meta.issues.open || undefined,
-    )}
-    {@render subItem(
-      router.routeToPath({
-        resource: "repo.patches",
-        rid: repo.rid,
-        status: "open",
-      }),
-      "patch",
-      "Patches",
-      isPatches(repo.rid),
-      activeProject?.meta.patches.open || undefined,
-    )}
+    <div
+      class="sub-items"
+      transition:slide={{ duration: ANIMATION_DURATION_MS }}>
+      {@render subItem(
+        router.routeToPath({
+          resource: "repo.issues",
+          rid: repo.rid,
+          status: "open",
+        }),
+        "issue",
+        "Issues",
+        isIssues(repo.rid),
+        activeProject?.meta.issues.open || undefined,
+      )}
+      {@render subItem(
+        router.routeToPath({
+          resource: "repo.patches",
+          rid: repo.rid,
+          status: "open",
+        }),
+        "patch",
+        "Patches",
+        isPatches(repo.rid),
+        activeProject?.meta.patches.open || undefined,
+      )}
+    </div>
   {/if}
 {/snippet}
 
@@ -767,16 +893,25 @@
   active: boolean,
   count: number | undefined,
 )}
-  <a class="nav-item sub-item" class:active {href}>
+  <a
+    class="nav-item sub-item"
+    class:active
+    class:mini={sidebarCollapsed.value}
+    {href}>
     <span class="icon"><Icon name={icon} /></span>
-    {label}
-    {#if count !== undefined}
-      <span class="global-counter-badge">{count}</span>
+    <span class="label">{label}</span>
+    {#if !sidebarCollapsed.value && count !== undefined}
+      <span
+        class="global-counter-badge"
+        in:scale={{ duration: 200, easing: backOut, start: 0 }}
+        out:fade={{ duration: 200 }}>
+        {count}
+      </span>
     {/if}
   </a>
 {/snippet}
 
-{#if reposExpanded.value}
+{#if reposExpanded.value && !sidebarCollapsed.value}
   <ScrollArea
     style="flex: 1; min-height: 0; mask-image: linear-gradient(to bottom, transparent 0, black 0.5rem, black calc(100% - 0.5rem), transparent 100%);">
     <div class="repos-list">
diff --git a/src/lib/flip.ts b/src/lib/flip.ts
new file mode 100644
index 000000000..a893f07bd
--- /dev/null
+++ b/src/lib/flip.ts
@@ -0,0 +1,86 @@
+// FLIP: animate elements from where they were to where a layout change just put
+// them. Capture from `$effect.pre` and play from `$effect`, both reading the
+// state that drives the change so they land on the same flush.
+//
+// Positions are relative to the container, so only the reflow inside it is
+// animated; the container's own shift is left to whatever already carries it.
+
+export interface FlipOptions {
+  // Which descendants to animate. Defaults to the container's direct children.
+  selector?: string;
+  // Animate the container's height too. Needed when it lays out to `auto` in
+  // one state, which a CSS transition can't carry.
+  animateHeight?: boolean;
+  durationMs?: number;
+}
+
+export interface FlipSnapshot {
+  offsets: WeakMap<Element, { x: number; y: number }>;
+  height: number;
+}
+
+const DEFAULT_DURATION_MS = 200;
+
+// Sub-pixel differences are rounding, not movement.
+const EPSILON_PX = 0.5;
+
+function targets(container: Element, selector: string | undefined): Element[] {
+  return Array.from(
+    selector ? container.querySelectorAll(selector) : container.children,
+  );
+}
+
+export function captureFlip(
+  container: Element | undefined,
+  options: FlipOptions = {},
+): FlipSnapshot | undefined {
+  // First run, before the bind has landed. Returning nothing stops `playFlip`
+  // animating in from a zero-sized phantom.
+  if (!container) return undefined;
+
+  const base = container.getBoundingClientRect();
+  const offsets = new WeakMap<Element, { x: number; y: number }>();
+  for (const child of targets(container, options.selector)) {
+    const rect = child.getBoundingClientRect();
+    offsets.set(child, { x: rect.left - base.left, y: rect.top - base.top });
+  }
+
+  return { offsets, height: base.height };
+}
+
+export function playFlip(
+  container: Element | undefined,
+  first: FlipSnapshot | undefined,
+  options: FlipOptions = {},
+): void {
+  if (!container || !first) return;
+
+  const duration = options.durationMs ?? DEFAULT_DURATION_MS;
+  const base = container.getBoundingClientRect();
+
+  if (
+    options.animateHeight &&
+    Math.abs(base.height - first.height) > EPSILON_PX
+  ) {
+    container.animate(
+      [{ height: `${first.height}px` }, { height: `${base.height}px` }],
+      { duration, easing: "ease" },
+    );
+  }
+
+  for (const child of targets(container, options.selector)) {
+    const from = first.offsets.get(child);
+    if (!from) continue;
+    const rect = child.getBoundingClientRect();
+    const dx = from.x - (rect.left - base.left);
+    const dy = from.y - (rect.top - base.top);
+    if (Math.abs(dx) < EPSILON_PX && Math.abs(dy) < EPSILON_PX) continue;
+    child.animate(
+      [
+        { transform: `translate(${dx}px, ${dy}px)` },
+        { transform: "translate(0px, 0px)" },
+      ],
+      { duration, easing: "ease" },
+    );
+  }
+}
diff --git a/src/lib/sidebar.svelte.ts b/src/lib/sidebar.svelte.ts
new file mode 100644
index 000000000..fc239c259
--- /dev/null
+++ b/src/lib/sidebar.svelte.ts
@@ -0,0 +1,96 @@
+import { boolean, number } from "zod";
+
+import useLocalStorage from "@app/lib/useLocalStorage.svelte";
+
+export const MIN_SIDEBAR_WIDTH = 12;
+export const MAX_SIDEBAR_WIDTH = 30;
+export const DEFAULT_SIDEBAR_WIDTH = 16.5;
+
+// Wide enough to clear macOS's traffic lights (~70px in), which would otherwise
+// spill onto the content pane. Not platform-gated, to keep one rail geometry.
+export const RAIL_WIDTH_REM = 5;
+
+// The widths above are rem and the user can scale the root font size, so cap
+// the share of the window the sidebar may take. Mirrored by `max-width` on the
+// slot, which also covers the window being resized afterwards.
+const MAX_VIEWPORT_FRACTION = 0.4;
+
+export function rootFontSize(): number {
+  return parseFloat(getComputedStyle(document.documentElement).fontSize) || 16;
+}
+
+export function clampSidebarWidth(rem: number): number {
+  if (!Number.isFinite(rem)) return DEFAULT_SIDEBAR_WIDTH;
+  const viewportMax =
+    (window.innerWidth * MAX_VIEWPORT_FRACTION) / rootFontSize();
+  // Never below the minimum, even in a window too narrow to honour the share.
+  const max = Math.max(
+    MIN_SIDEBAR_WIDTH,
+    Math.min(MAX_SIDEBAR_WIDTH, viewportMax),
+  );
+  return Math.min(max, Math.max(MIN_SIDEBAR_WIDTH, rem));
+}
+
+export const sidebarCollapsed = useLocalStorage(
+  "sidebarCollapsed",
+  boolean(),
+  false,
+  !window.localStorage,
+);
+
+export const sidebarWidth = useLocalStorage(
+  "sidebarWidth",
+  number(),
+  DEFAULT_SIDEBAR_WIDTH,
+  !window.localStorage,
+);
+
+// Writes are clamped; a value stored by a build with different bounds is not.
+// Only written back when out of range, to keep startup off localStorage.
+const restoredWidth = clampSidebarWidth(sidebarWidth.value);
+if (sidebarWidth.value !== restoredWidth) {
+  sidebarWidth.value = restoredWidth;
+}
+
+// True while dragging the resize edge; suppresses the width transition so the
+// sidebar tracks the pointer 1:1.
+export const sidebarResizing = $state({ value: false });
+
+// Held out of `sidebarWidth`, which writes to localStorage on every set.
+const draft = $state<{ width: number | undefined }>({ width: undefined });
+
+// The live drag value while resizing, the stored one otherwise.
+export const renderedSidebarWidth = {
+  get value() {
+    return draft.width ?? sidebarWidth.value;
+  },
+};
+
+export function previewSidebarWidth(rem: number) {
+  draft.width = clampSidebarWidth(rem);
+}
+
+// Drops the drag's width without storing it, for a drag that ends up collapsing
+// instead: the widths it passed through on the way down are not a width the
+// user chose, so the stored one is left alone to reopen at.
+export function discardSidebarWidthPreview() {
+  draft.width = undefined;
+}
+
+// A one-shot width change, for callers that aren't tracking a pointer.
+export function setSidebarWidth(rem: number) {
+  draft.width = undefined;
+  sidebarWidth.value = clampSidebarWidth(rem);
+}
+
+// The single storage write for a whole drag.
+export function commitSidebarWidth() {
+  if (draft.width !== undefined) {
+    sidebarWidth.value = draft.width;
+    draft.width = undefined;
+  }
+}
+
+export function toggleSidebar() {
+  sidebarCollapsed.value = !sidebarCollapsed.value;
+}