diff --git a/services/assistant-ui/src/features/workspaces/__tests__/SessionTabs.test.ts b/services/assistant-ui/src/features/workspaces/__tests__/SessionTabs.test.ts
index 5bc639ae..9c77fbaf 100644
--- a/services/assistant-ui/src/features/workspaces/__tests__/SessionTabs.test.ts
+++ b/services/assistant-ui/src/features/workspaces/__tests__/SessionTabs.test.ts
@@ -89,4 +89,14 @@ describe('sessionTabs', () => {
     expect(wrapper.emitted('select')).toEqual([[session.id]])
     expect(wrapper.emitted('stop')).toEqual([[session.id]])
   })
+
+  it('keeps horizontal session tabs scrollable with stable tab widths', () => {
+    const sessions = Array.from({ length: 12 }, (_, i) => fakeSession({ id: `session-${String(i).padStart(2, '0')}` }))
+    const wrapper = mount(SessionTabs, {
+      props: { sessions, activeId: sessions[0]?.id ?? null },
+    })
+
+    expect(wrapper.get('[data-testid="session-tabs-list"]').classes()).toContain('overflow-x-auto')
+    expect(wrapper.findAll('li').every((li) => li.classes().includes('shrink-0'))).toBe(true)
+  })
 })
diff --git a/services/assistant-ui/src/features/workspaces/__tests__/WorkspaceView.test.ts b/services/assistant-ui/src/features/workspaces/__tests__/WorkspaceView.test.ts
index de23195d..c84cbf8f 100644
--- a/services/assistant-ui/src/features/workspaces/__tests__/WorkspaceView.test.ts
+++ b/services/assistant-ui/src/features/workspaces/__tests__/WorkspaceView.test.ts
@@ -262,24 +262,68 @@ describe('workspaceView terminal persistence', () => {
     expect(sendInput.mock.calls[0]?.[2]).not.toContain('large document')
   })
 
-  it('keeps workspace controls in the sidebar', async () => {
+  it('places agent controls and sessions in the top chrome while keeping tools in the sidebar', async () => {
     getWorkspace.mockResolvedValue(detail([fakeSession({ id: 'sess-a', gatewayAgentId: 'abc12345' })]))
 
     const wrapper = await mountView()
+    const header = wrapper.get('[data-testid="workspace-view-header"]')
+    const sessionStrip = wrapper.get('[data-testid="workspace-session-strip"]')
     const sidebar = wrapper.get('[data-testid="workspace-sidebar"]')
 
-    expect(wrapper.get('[data-testid="workspace-view-header"]').find('[data-testid="stage-input-open"]').exists()).toBe(
-      false,
-    )
-    expect(sidebar.find('[data-testid="workspace-agent-panel"]').exists()).toBe(true)
-    expect(sidebar.find('[data-testid="workspace-new-agent"]').exists()).toBe(true)
+    expect(header.find('[data-testid="workspace-agent-panel"]').exists()).toBe(true)
+    expect(header.find('[data-testid="workspace-new-agent"]').exists()).toBe(true)
+    expect(header.find('[data-testid="stage-input-open"]').exists()).toBe(false)
+    expect(sessionStrip.find('[data-testid="session-tabs"]').exists()).toBe(true)
+    expect(sessionStrip.find('[data-testid="session-tab-sess-a"]').exists()).toBe(true)
+    expect(sidebar.find('[data-testid="workspace-agent-panel"]').exists()).toBe(false)
+    expect(sidebar.find('[data-testid="session-tabs"]').exists()).toBe(false)
     expect(sidebar.find('[data-testid="workspace-tools-panel"]').exists()).toBe(true)
     expect(sidebar.find('[data-testid="stage-input-open"]').exists()).toBe(true)
-    expect(sidebar.find('[data-testid="workspace-sessions-panel"]').exists()).toBe(true)
-    expect(sidebar.find('[data-testid="session-tabs"]').exists()).toBe(true)
     expect(sidebar.find('[data-testid="workspace-repositories-panel"]').exists()).toBe(true)
   })
 
+  for (const status of ['STOPPED', 'FAILED'] as const) {
+    it(`hides ${status.toLowerCase()} sessions from the top tab strip`, async () => {
+      getWorkspace.mockResolvedValue(detail([fakeSession({ id: 'sess-a' }), fakeSession({ id: 'sess-b', status })]))
+
+      const wrapper = await mountView()
+      const sessionStrip = wrapper.get('[data-testid="workspace-session-strip"]')
+
+      expect(sessionStrip.find('[data-testid="session-tab-sess-a"]').exists()).toBe(true)
+      expect(sessionStrip.find('[data-testid="session-tab-sess-b"]').exists()).toBe(false)
+      expect(wrapper.findAll('[data-testid="session-terminal"]').length).toBe(1)
+    })
+  }
+
+  it('shows an empty live-session surface and disables staged input when every session is closed', async () => {
+    getWorkspace.mockResolvedValue(detail([fakeSession({ id: 'sess-a', status: 'STOPPED' })]))
+
+    const wrapper = await mountView()
+
+    expect(wrapper.get('[data-testid="workspace-session-strip"]').text()).toContain('No sessions yet.')
+    expect(wrapper.text()).toContain('Start an agent from the top bar.')
+    expect(wrapper.get('[data-testid="stage-input-open"]').attributes('disabled')).toBeDefined()
+  })
+
+  it('folds the right sidebar with the triple-bar control', async () => {
+    getWorkspace.mockResolvedValue(detail([fakeSession({ id: 'sess-a' })]))
+
+    const wrapper = await mountView()
+    const toggle = wrapper.get('[data-testid="workspace-sidebar-toggle"]')
+    const sidebar = wrapper.get('[data-testid="workspace-sidebar"]')
+
+    expect(toggle.attributes('aria-expanded')).toBe('true')
+    expect(toggle.attributes('aria-controls')).toBe('workspace-sidebar')
+    expect(sidebar.classes()).toContain('translate-x-0')
+
+    await toggle.trigger('click')
+
+    expect(toggle.attributes('aria-expanded')).toBe('false')
+    expect(sidebar.classes()).toContain('translate-x-full')
+    expect(sidebar.attributes('aria-hidden')).toBe('true')
+    expect(sidebar.attributes('inert')).toBeDefined()
+  })
+
   it('renders attached repositories, marks the primary, and shows split guidance', async () => {
     const primary = fakeWorkspaceRepository({ id: 'repo-primary', name: 'primary', isPrimary: true })
     const destination = fakeWorkspaceRepository({
@@ -379,6 +423,22 @@ describe('workspaceView terminal persistence', () => {
     expect(wrapper.find('[data-testid="workspace-repository-repo-extra"]').exists()).toBe(true)
   })
 
+  it('opens the repository picker from split guidance when a destination repository is needed', async () => {
+    const primary = fakeWorkspaceRepository({ id: 'repo-primary', name: 'primary', isPrimary: true })
+    getWorkspace.mockResolvedValue(detail([fakeSession({ id: 'sess-a' })], { repositories: [primary] }))
+    listRepositories.mockResolvedValue([
+      fakeRepository({ id: 'repo-primary', name: 'primary' }),
+      fakeRepository({ id: 'repo-extra', name: 'extra', repoUrl: 'git@github.com:owner/extra.git' }),
+    ])
+    const wrapper = await mountView()
+
+    await wrapper.find('[data-testid="split-attach-destination"]').trigger('click')
+    await flush()
+
+    expect(listRepositories).toHaveBeenCalledOnce()
+    expect(document.querySelector('[data-testid="repository-picker-radio-repo-extra"]')).not.toBeNull()
+  })
+
   it('removes non-primary repositories and reports detach failures', async () => {
     const primary = fakeWorkspaceRepository({ id: 'repo-primary', name: 'primary', isPrimary: true })
     const destination = fakeWorkspaceRepository({
diff --git a/services/assistant-ui/src/features/workspaces/components/AgentKindPicker.vue b/services/assistant-ui/src/features/workspaces/components/AgentKindPicker.vue
index cae90e57..1d9b50f7 100644
--- a/services/assistant-ui/src/features/workspaces/components/AgentKindPicker.vue
+++ b/services/assistant-ui/src/features/workspaces/components/AgentKindPicker.vue
@@ -16,7 +16,7 @@ const options: { value: AgentKind; label: string; description: string }[] = [
 <template>
   <div
     class="grid gap-2"
-    :class="props.compact ? 'grid-cols-1' : 'grid-cols-1 sm:grid-cols-3'"
+    :class="props.compact ? 'grid-cols-3' : 'grid-cols-1 sm:grid-cols-3'"
     data-testid="agent-kind-picker"
     aria-label="Agent kind"
   >
@@ -24,9 +24,9 @@ const options: { value: AgentKind; label: string; description: string }[] = [
       v-for="opt in options"
       :key="opt.value"
       type="button"
-      class="rounded-md border text-left transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-accent-light)] focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)]"
+      class="rounded-md border transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-accent-light)] focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)]"
       :class="[
-        props.compact ? 'p-2.5' : 'p-3',
+        props.compact ? 'px-3 py-2 text-center' : 'p-3 text-left',
         props.modelValue === opt.value
           ? 'border-[var(--color-accent-light)] bg-[var(--color-surface-elevated)] text-[var(--color-text-primary)]'
           : 'border-[var(--color-surface-border)] bg-[var(--color-surface)] text-[var(--color-text-primary)] hover:border-[var(--color-accent-light)]',
@@ -35,8 +35,8 @@ const options: { value: AgentKind; label: string; description: string }[] = [
       :aria-label="opt.label"
       @click="emit('update:modelValue', opt.value)"
     >
-      <div class="font-semibold">{{ opt.label }}</div>
-      <div class="text-xs text-[var(--color-text-muted)] mt-1">{{ opt.description }}</div>
+      <div class="text-sm font-semibold leading-5">{{ opt.label }}</div>
+      <div v-if="!props.compact" class="text-xs text-[var(--color-text-muted)] mt-1">{{ opt.description }}</div>
     </button>
   </div>
 </template>
diff --git a/services/assistant-ui/src/features/workspaces/components/SessionTabs.vue b/services/assistant-ui/src/features/workspaces/components/SessionTabs.vue
index 3941e4a4..8d326c69 100644
--- a/services/assistant-ui/src/features/workspaces/components/SessionTabs.vue
+++ b/services/assistant-ui/src/features/workspaces/components/SessionTabs.vue
@@ -81,23 +81,28 @@ function sessionShellClasses(s: AgentSession): string[] {
 
   return [
     base,
-    'flex border-b-2 px-3 py-2',
+    'flex rounded-t-md border-b-2 px-3 py-2.5',
     active
-      ? 'border-[var(--color-accent-light)] text-[var(--color-text-primary)]'
-      : 'border-transparent text-[var(--color-text-muted)] hover:text-[var(--color-text-primary)]',
+      ? 'border-[var(--color-accent-light)] bg-[var(--color-surface-elevated)] text-[var(--color-text-primary)]'
+      : 'border-transparent text-[var(--color-text-muted)] hover:bg-[var(--color-surface-card)] hover:text-[var(--color-text-primary)]',
   ]
 }
 </script>
 
 <template>
-  <nav
-    :class="isVertical ? 'space-y-2' : 'border-b border-[var(--color-surface-border)] px-2'"
-    data-testid="session-tabs"
-    aria-label="Agent sessions"
-  >
+  <nav :class="isVertical ? 'space-y-2' : 'min-w-0'" data-testid="session-tabs" aria-label="Agent sessions">
     <p v-if="props.sessions.length === 0" class="text-sm italic text-[var(--color-text-muted)]">No sessions yet.</p>
-    <ul v-else :class="isVertical ? 'space-y-2' : 'flex gap-1 overflow-x-auto'">
-      <li v-for="s in props.sessions" :key="s.id" class="flex min-w-0 items-stretch gap-1">
+    <ul
+      v-else
+      :class="isVertical ? 'space-y-2' : 'flex gap-1 overflow-x-auto overflow-y-hidden px-1 pt-1'"
+      data-testid="session-tabs-list"
+    >
+      <li
+        v-for="s in props.sessions"
+        :key="s.id"
+        class="flex min-w-0 items-stretch gap-1"
+        :class="isVertical ? '' : 'w-[15rem] shrink-0'"
+      >
         <div v-if="editingId === s.id" :class="sessionShellClasses(s)">
           <span class="shrink-0 rounded px-2 py-0.5 text-xs font-semibold" :class="kindBadge[s.kind]">
             {{ s.kind }}
@@ -146,7 +151,7 @@ function sessionShellClasses(s: AgentSession): string[] {
           v-if="s.status === 'RUNNING'"
           type="button"
           class="shrink-0 rounded-md border border-transparent px-2 text-sm text-red-400 transition-colors hover:border-red-500/40 hover:bg-red-500/10 hover:text-red-300 focus:outline-none focus-visible:ring-2 focus-visible:ring-red-400 focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)]"
-          :class="isVertical ? 'self-stretch' : 'py-2'"
+          :class="isVertical ? 'self-stretch' : 'my-1 py-1'"
           :aria-label="`Stop session ${tabLabel(s)}`"
           :data-testid="`session-tab-stop-${s.id}`"
           @click="emit('stop', s.id)"
diff --git a/services/assistant-ui/src/features/workspaces/views/WorkspaceView.vue b/services/assistant-ui/src/features/workspaces/views/WorkspaceView.vue
index 35f9688b..593441ca 100644
--- a/services/assistant-ui/src/features/workspaces/views/WorkspaceView.vue
+++ b/services/assistant-ui/src/features/workspaces/views/WorkspaceView.vue
@@ -28,6 +28,7 @@ const isSendingSplitCommand = ref(false)
 const isAttachingRepository = ref(false)
 const detachingRepositoryId = ref<string | null>(null)
 const repositoryActionError = ref<string | null>(null)
+const isSidebarCollapsed = ref(false)
 
 // Only sessions with a live PTY get a mounted terminal. A session
 // dropping out of this set (STOPPED/FAILED) unmounts its
@@ -135,9 +136,10 @@ async function onDetachRepository(repositoryId: string, repositoryName: string):
        main overflowed by the nav height, so the page scrolled on top
        of the terminal's own scroll. Sizing to the remaining space keeps
        a single scroll region (the xterm viewport). -->
-  <div class="flex flex-col h-[calc(100vh-3.5rem)] overflow-hidden">
+  <div class="relative flex h-[calc(100vh-3.5rem)] flex-col overflow-hidden bg-[var(--color-surface-dark)]">
     <header
-      class="flex items-center border-b border-[var(--color-surface-border)] px-6 py-3"
+      class="z-10 flex shrink-0 flex-col gap-3 border-b border-[var(--color-surface-border)] bg-[var(--color-surface-dark)] px-4 py-3 transition-[padding] sm:px-6 xl:flex-row xl:items-center xl:justify-between"
+      :class="isSidebarCollapsed ? 'lg:pr-16' : 'lg:pr-[25rem]'"
       data-testid="workspace-view-header"
     >
       <div class="min-w-0">
@@ -155,10 +157,42 @@ async function onDetachRepository(repositoryId: string, repositoryName: string):
           {{ store.activeWorkspace.repoUrl }}
         </p>
       </div>
+      <div
+        class="flex min-w-0 flex-col gap-2 sm:flex-row sm:items-center sm:justify-end"
+        data-testid="workspace-agent-panel"
+      >
+        <AgentKindPicker v-model="pickerKind" compact class="w-full min-w-0 sm:w-[24rem]" />
+        <button
+          type="button"
+          class="inline-flex min-h-10 w-full items-center justify-center whitespace-nowrap rounded-md border border-transparent bg-[var(--color-accent)] px-4 py-2 text-sm font-medium text-white shadow-sm transition-colors hover:bg-[var(--color-accent-light)] focus:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-accent-light)] focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)] disabled:cursor-not-allowed disabled:opacity-60 sm:w-auto"
+          :disabled="store.startingSession"
+          data-testid="workspace-new-agent"
+          aria-label="Start a new agent session"
+          @click="onSpawn"
+        >
+          {{ spawnButtonLabel }}
+        </button>
+      </div>
     </header>
 
-    <main class="flex min-h-0 flex-1 flex-col overflow-hidden lg:flex-row">
-      <section class="flex min-h-0 min-w-0 flex-1 flex-col overflow-hidden p-4">
+    <div
+      class="z-10 shrink-0 border-b border-[var(--color-surface-border)] bg-[var(--color-surface-dark)] px-3 transition-[padding] sm:px-5"
+      :class="isSidebarCollapsed ? 'lg:pr-16' : 'lg:pr-[24rem]'"
+      data-testid="workspace-session-strip"
+    >
+      <SessionTabs
+        :sessions="liveSessions"
+        :active-id="store.activeSessionId"
+        @select="store.selectSession"
+        @stop="onStopSession"
+      />
+    </div>
+
+    <main class="flex min-h-0 flex-1 overflow-hidden">
+      <section
+        class="flex min-h-0 min-w-0 flex-1 flex-col overflow-hidden p-4 transition-[padding]"
+        :class="isSidebarCollapsed ? 'lg:pr-16' : 'lg:pr-[24.5rem]'"
+      >
         <!-- One terminal per live session, all kept mounted; v-show (not
              v-if/:key) so switching tabs preserves each xterm buffer and
              its WebSocket. A session leaving the live set (stopped/failed)
@@ -174,41 +208,39 @@ async function onDetachRepository(repositoryId: string, repositoryName: string):
           v-if="liveSessions.length === 0"
           class="flex flex-1 items-center justify-center rounded-md border border-dashed border-[var(--color-surface-border)] text-center text-sm italic text-[var(--color-text-muted)]"
         >
-          Start an agent from the sidebar.
+          Start an agent from the top bar.
         </div>
       </section>
+    </main>
 
-      <aside
-        v-if="store.activeWorkspace"
-        class="flex min-h-0 w-full shrink-0 flex-col gap-4 overflow-y-auto border-t border-[var(--color-surface-border)] bg-[var(--color-surface-card)] p-4 lg:w-[23rem] lg:border-l lg:border-t-0"
-        data-testid="workspace-sidebar"
-        aria-label="Workspace controls"
-      >
-        <section
-          class="rounded-md border border-[var(--color-surface-border)] bg-[var(--color-surface-card)] p-4"
-          data-testid="workspace-agent-panel"
-        >
-          <div class="mb-3 flex items-center justify-between gap-3">
-            <h2 class="text-sm font-semibold">Agents</h2>
-            <span
-              class="rounded border border-[var(--color-surface-border)] px-2 py-0.5 text-xs text-[var(--color-text-muted)]"
-            >
-              {{ liveSessions.length }} live
-            </span>
-          </div>
-          <AgentKindPicker v-model="pickerKind" compact />
-          <button
-            type="button"
-            class="mt-3 inline-flex min-h-11 w-full items-center justify-center rounded-md border border-transparent bg-[var(--color-accent)] px-4 py-2 text-sm font-medium text-white shadow-sm transition-colors hover:bg-[var(--color-accent-light)] focus:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-accent-light)] focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)] disabled:cursor-not-allowed disabled:opacity-60"
-            :disabled="store.startingSession"
-            data-testid="workspace-new-agent"
-            aria-label="Start a new agent session"
-            @click="onSpawn"
-          >
-            {{ spawnButtonLabel }}
-          </button>
-        </section>
+    <button
+      v-if="store.activeWorkspace"
+      type="button"
+      class="absolute right-3 top-3 z-30 inline-flex h-10 w-10 items-center justify-center rounded-md border border-[var(--color-surface-border)] bg-[var(--color-surface-elevated)] text-[var(--color-text-primary)] shadow-sm transition-colors hover:bg-[var(--color-surface-border)] focus:outline-none focus-visible:ring-2 focus-visible:ring-[var(--color-accent-light)] focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--color-surface-dark)]"
+      :aria-expanded="!isSidebarCollapsed"
+      :aria-label="isSidebarCollapsed ? 'Open workspace sidebar' : 'Close workspace sidebar'"
+      aria-controls="workspace-sidebar"
+      data-testid="workspace-sidebar-toggle"
+      @click="isSidebarCollapsed = !isSidebarCollapsed"
+    >
+      <span class="flex h-5 w-5 flex-col justify-center gap-1" aria-hidden="true">
+        <span class="block h-0.5 rounded bg-current" />
+        <span class="block h-0.5 rounded bg-current" />
+        <span class="block h-0.5 rounded bg-current" />
+      </span>
+    </button>
 
+    <aside
+      v-if="store.activeWorkspace"
+      id="workspace-sidebar"
+      class="absolute bottom-0 right-0 top-0 z-20 flex w-[min(24rem,calc(100vw-1rem))] min-h-0 flex-col overflow-hidden border-l border-[var(--color-surface-border)] bg-[var(--color-surface-card)] shadow-2xl transition-transform duration-200 ease-out"
+      :class="isSidebarCollapsed ? 'translate-x-full' : 'translate-x-0'"
+      :aria-hidden="isSidebarCollapsed ? 'true' : undefined"
+      :inert="isSidebarCollapsed"
+      data-testid="workspace-sidebar"
+      aria-label="Workspace controls"
+    >
+      <div class="flex min-h-0 flex-1 flex-col gap-4 overflow-y-auto p-4 pt-16">
         <section
           class="rounded-md border border-[var(--color-surface-border)] bg-[var(--color-surface-card)] p-4"
           data-testid="workspace-tools-panel"
@@ -229,23 +261,6 @@ async function onDetachRepository(repositoryId: string, repositoryName: string):
           </button>
         </section>
 
-        <section
-          class="rounded-md border border-[var(--color-surface-border)] bg-[var(--color-surface-card)] p-4"
-          data-testid="workspace-sessions-panel"
-        >
-          <div class="mb-3 flex items-center justify-between gap-3">
-            <h2 class="text-sm font-semibold">Sessions</h2>
-            <span class="text-xs text-[var(--color-text-muted)]">{{ store.sessions.length }}</span>
-          </div>
-          <SessionTabs
-            :sessions="store.sessions"
-            :active-id="store.activeSessionId"
-            orientation="vertical"
-            @select="store.selectSession"
-            @stop="onStopSession"
-          />
-        </section>
-
         <WorkspaceRepositoriesPanel
           :repositories="store.activeWorkspace.repositories ?? []"
           :attach-pending="isAttachingRepository"
@@ -262,8 +277,8 @@ async function onDetachRepository(repositoryId: string, repositoryName: string):
           @add-destination="showRepositoryPicker = true"
           @send-command="onSendSplitCommand"
         />
-      </aside>
-    </main>
+      </div>
+    </aside>
 
     <Modal :open="showRepositoryPicker" title="Attach repository" @close="showRepositoryPicker = false">
       <WorkspaceRepositoryPicker