diff --git a/scripts/cmux-next/layers-baseline.tsv b/scripts/cmux-next/layers-baseline.tsv
index 362b15a0cd32..77308d25c45c 100644
--- a/scripts/cmux-next/layers-baseline.tsv
+++ b/scripts/cmux-next/layers-baseline.tsv
@@ -4,7 +4,7 @@ webviews/src/agent-session/acpmux/changes/treeMotionDom.ts	z	1
 webviews/src/agent-session/acpmux/composerAttachments.css	z	1
 webviews/src/agent-session/acpmux/handoff/styles.css	z	1
 webviews/src/agent-session/acpmux/prototype/prototype.css	z	5
-webviews/src/agent-session/acpmux/styles.css	z	5
+webviews/src/agent-session/acpmux/styles.css	z	3
 webviews/src/agent-session/acpmux/threadMinimap/threadMinimap.css	z	1
 webviews/src/gallery/fixtures/VisualMediaBoard.css	backdrop	1
 webviews/src/gallery/frame/liveErrors.ts	z	1
diff --git a/scripts/cmux-next/type-scale-baseline.tsv b/scripts/cmux-next/type-scale-baseline.tsv
index 627f486e7b3b..418be65f1bd6 100644
--- a/scripts/cmux-next/type-scale-baseline.tsv
+++ b/scripts/cmux-next/type-scale-baseline.tsv
@@ -13,8 +13,8 @@ webviews/src/agent-session/acpmux/keys.css	size	1
 webviews/src/agent-session/acpmux/markdownField.css	size	4
 webviews/src/agent-session/acpmux/mockFixture.ts	size	2
 webviews/src/agent-session/acpmux/newtab/screen.css	size	15
-webviews/src/agent-session/acpmux/prototype/prototype.css	size	18
-webviews/src/agent-session/acpmux/styles.css	size	58
+webviews/src/agent-session/acpmux/prototype/prototype.css	size	17
+webviews/src/agent-session/acpmux/styles.css	size	53
 webviews/src/agent-session/acpmux/subagents/subagents.css	size	2
 webviews/src/agent-session/acpmux/threadMinimap/threadMinimap.css	size	1
 webviews/src/gallery/env.ts	size	1
diff --git a/webviews/src/agent-session/acpmux/SessionSidebar.gallery.tsx b/webviews/src/agent-session/acpmux/SessionSidebar.gallery.tsx
deleted file mode 100644
index 5f79eab22801..000000000000
--- a/webviews/src/agent-session/acpmux/SessionSidebar.gallery.tsx
+++ /dev/null
@@ -1,352 +0,0 @@
-// l10n-allow-file: gallery fixtures (sample sessions), not shipped UI.
-// The sidebar's list, rail and session actions are rendered by the real SessionSidebar component;
-// callbacks are no-ops because this gallery lane measures the interaction surface, not the host.
-import type { ComponentProps } from "react";
-import { componentEntry } from "../../gallery/format";
-import { minutesAgo } from "../../gallery/clock";
-import { session } from "../../gallery/fixtures/acpmux";
-import type { PlayContext } from "../../gallery/play";
-import type { SessionSidebar } from "./SessionSidebar";
-
-type Props = ComponentProps<typeof SessionSidebar>;
-
-const sessions: Props["sessions"] = [
-  session({
-    sessionId: "sidebar-first",
-    title: "Fix the checkout page",
-    updatedAt: minutesAgo(1),
-    status: "running",
-    indicator: "working",
-    preview: "The checkout still needs a final pass on the payment form.",
-    cwd: "/Users/you/src/cmux",
-    branch: "feat/checkout",
-  }),
-  session({
-    sessionId: "sidebar-second",
-    title: "Port the sidebar",
-    updatedAt: minutesAgo(2),
-    unread: true,
-    indicator: "done",
-    cwd: "/Users/you/src/cmux",
-    branch: "feat/sidebar-polish",
-  }),
-  session({
-    sessionId: "sidebar-third",
-    title: "Profile transcript scrolling",
-    updatedAt: minutesAgo(3),
-    cwd: "/Users/you/src/cmux",
-    status: "idle",
-  }),
-  session({
-    sessionId: "sidebar-cloud",
-    title: "Review the cloud build",
-    updatedAt: minutesAgo(4),
-    cwd: "/workspace/cmux",
-    host: "Build runner",
-    hostKind: "cloud",
-    peer: "Build runner",
-    branch: "ci/nightly",
-  }),
-];
-
-/** An agent whose sub-session waits for the person to trust a folder (hub/trust_wait.rs). */
-const trustWaiting: Props["sessions"] = [
-  session({
-    sessionId: "sidebar-trust",
-    title: "Split the importer into parts",
-    updatedAt: minutesAgo(1),
-    status: "waiting",
-    indicator: "input",
-    trustPending: "/Users/you/src/vendor-sdk",
-    cwd: "/Users/you/src/cmux",
-    branch: "feat/importer",
-  }),
-  ...sessions.slice(0, 2),
-];
-
-const sessionsWithoutPreview = sessions.map((entry) => ({ ...entry, preview: undefined }));
-
-const active = session({
-  sessionId: "sidebar-active",
-  title: "Fix the active bug",
-  updatedAt: minutesAgo(1),
-  status: "running",
-  indicator: "working",
-});
-const settled = session({
-  sessionId: "sidebar-settled",
-  title: "Review the settled draft",
-  updatedAt: minutesAgo(2),
-  status: "closed",
-});
-
-const baseProps: Props = {
-  sessions,
-  selectedId: "sidebar-first",
-  onSelect: () => undefined,
-  onNewChat: () => undefined,
-  account: { name: "Leo", detail: "Personal" },
-  groupProjects: true,
-  preview: true,
-  openIds: new Set(["sidebar-second"]),
-};
-
-const waitForActiveRow = (ctx: PlayContext, id: string) =>
-  ctx.waitFor(() => ctx.document.activeElement?.getAttribute("data-session-id") === id);
-
-// The field's label is "Search chats" since #19895 (the lists say chats).
-const SEARCH = 'input[aria-label="Search chats"]';
-
-const search = async (ctx: PlayContext) => {
-  await ctx.type("sidebar", { selector: SEARCH });
-  // "sidebar" matches one chat, by its title and branch; its project's header stays.
-  await ctx.waitFor(() => {
-    const rows = ctx.document.querySelectorAll(".acpmux-session-row");
-    return rows.length === 1 && rows[0]?.getAttribute("data-session-id") === "sidebar-second";
-  });
-};
-
-// A search removes rows, so the matches and the Settled section below them move up inside the
-// scroll region (about 0.004); the sidebar frame and the rail, the anchors, stay put.
-const searchChecks = {
-  layoutShiftMax: {
-    value: 0.01,
-    reason: "Filtering moves the remaining rows up inside the scroll region; the sidebar frame and rail do not move.",
-  },
-};
-
-const searchThenClear = async (ctx: PlayContext) => {
-  await search(ctx);
-  await ctx.press("Escape");
-  await ctx.waitFor(() => ctx.document.querySelector<HTMLInputElement>(SEARCH)?.value === "");
-};
-
-const rowKeyboard = async (ctx: PlayContext) => {
-  await ctx.focus({ selector: ".acpmux-session-row" });
-  await ctx.press("ArrowDown");
-  await waitForActiveRow(ctx, "sidebar-second");
-  await ctx.press("End");
-  await waitForActiveRow(ctx, "sidebar-cloud");
-  await ctx.press("Home");
-  await waitForActiveRow(ctx, "sidebar-first");
-};
-
-const railKeyboard = async (ctx: PlayContext) => {
-  await ctx.focus({ role: "button", name: /Sessions/ });
-  await ctx.press("ArrowDown");
-  await ctx.waitFor(() => ctx.document.activeElement?.getAttribute("aria-label") === "History");
-  await ctx.press("End");
-  await ctx.waitFor(() => ctx.document.activeElement?.getAttribute("aria-label") === "Closed sessions");
-  await ctx.press("Home");
-  await ctx.waitFor(() => ctx.document.activeElement?.getAttribute("aria-label") === "Sessions");
-};
-
-const switchViews = async (ctx: PlayContext) => {
-  await ctx.click({ role: "button", name: "History" });
-  await ctx.waitFor(() => ctx.document.querySelector('[aria-label="History"] .acpmux-sidebar-title'));
-  await ctx.click({ role: "button", name: "Pull requests" });
-  await ctx.waitFor(() => ctx.document.querySelector('[aria-label="Pull requests"] .acpmux-sidebar-empty'));
-  await ctx.click({ role: "button", name: "Closed sessions" });
-  await ctx.waitFor(() => ctx.document.querySelector('[aria-label="Closed sessions"] .acpmux-sidebar-title'));
-};
-
-/**
- * The sidebar's rail is also the workspace-switch affordance in the native shell. Keep one
- * canonical rapid round-trip for visual review: the play runner records each transition's frame
- * timing, settle latency, anchor geometry and layout shift. This deliberately uses the existing
- * play/manifest contract instead of introducing a second animation recorder.
- */
-const animationAudit = async (ctx: PlayContext) => {
-  const sidebar = ctx.find({ selector: ".acpmux-sidebar" });
-  const before = sidebar.getBoundingClientRect();
-  const transitions: Array<[string, string]> = [
-    ["History", 'section[aria-label="History"] .acpmux-sidebar-title'],
-    ["Pull requests", 'section[aria-label="Pull requests"] .acpmux-sidebar-empty'],
-    ["Closed sessions", 'section[aria-label="Closed sessions"] .acpmux-sidebar-title'],
-    ["Sessions", ".acpmux-sidebar-active"],
-  ];
-  for (const [label, section] of transitions) {
-    await ctx.click({ role: "button", name: label });
-    await ctx.waitFor(() => ctx.document.querySelector(section) !== null);
-    const after = sidebar.getBoundingClientRect();
-    const moved = Math.max(
-      Math.abs(before.left - after.left),
-      Math.abs(before.top - after.top),
-      Math.abs(before.width - after.width),
-      Math.abs(before.height - after.height),
-    );
-    if (moved > 0.5) throw new Error(`${label} moved the sidebar frame by ${moved.toFixed(1)}px`);
-  }
-};
-
-const contextActions = async (ctx: PlayContext) => {
-  const openMenu = (sessionId: string) => {
-    const row = ctx.find({ selector: `[data-session-id="${sessionId}"]` });
-    const box = row.getBoundingClientRect();
-    const view = ctx.document.defaultView!;
-    row.dispatchEvent(
-      new view.MouseEvent("contextmenu", {
-        bubbles: true,
-        cancelable: true,
-        clientX: box.left + 24,
-        clientY: box.top + 12,
-      }),
-    );
-  };
-
-  openMenu("sidebar-active");
-  await ctx.waitFor(() => ctx.document.querySelector('[role="menu"] [role="menuitem"]'));
-  await ctx.click({ role: "menuitem", name: "Settle" });
-  await ctx.waitFor(() => !ctx.document.querySelector('[role="menu"]'));
-
-  openMenu("sidebar-settled");
-  await ctx.waitFor(() => ctx.document.querySelector('[role="menu"] [role="menuitem"]'));
-  await ctx.click({ role: "menuitem", name: "Continue" });
-  await ctx.waitFor(() => !ctx.document.querySelector('[role="menu"]'));
-};
-
-const hoverPreview = async (ctx: PlayContext) => {
-  await ctx.hover({ selector: '[data-session-id="sidebar-first"]' });
-  await ctx.waitFor(() => ctx.document.querySelector(".acpmux-session-preview"));
-};
-
-const focusPreview = async (ctx: PlayContext) => {
-  await ctx.focus({ selector: '[data-session-id="sidebar-first"]' });
-  await ctx.waitFor(() => ctx.document.querySelector(".acpmux-session-preview"));
-};
-
-const entry = componentEntry<Props>({
-  id: "agent-pane.session-sidebar",
-  title: "Session sidebar",
-  area: "Agent pane",
-  pane: true,
-  height: 620,
-  widths: { narrow: 300, normal: 380, wide: 520 },
-  anchors: [{ selector: ".acpmux-sidebar" }, { selector: ".acpmux-sidebar-rail" }],
-  checks: {
-    anchorMovePx: {
-      value: 0,
-      reason: "Sidebar searches, menus and rail navigation must leave the sidebar frame and rail geometry stable.",
-    },
-    layoutShiftMax: {
-      value: 0,
-      reason: "Filtering and switching sidebar views replace rows inside the scroll region without moving the shell.",
-    },
-    longFrameFailMs: {
-      value: 33,
-      reason: "Sidebar filtering, menus and keyboard navigation should stay responsive on the gallery host.",
-    },
-    settleMaxMs: {
-      value: 250,
-      reason:
-        "Search, rail and context-menu actions are direct local interactions with a quarter-second response budget.",
-    },
-  },
-  covers: ["agent-session/acpmux/SessionSidebar.tsx#SessionSidebar"],
-  styles: () => import("./styles.css"),
-  load: () =>
-    import("./SessionSidebar").then(({ SessionSidebar: Sidebar }) => {
-      // The pane's shell is a flex row the window's height, so the sidebar fills it and a filtered
-      // list never moves the rail; the stage itself is a block that would size it to its rows.
-      const GallerySessionSidebar = (props: Props) => (
-        <div className="acpmux-shell" style={{ height: "100%" }}>
-          <Sidebar {...props} />
-        </div>
-      );
-      return GallerySessionSidebar;
-    }),
-  variants: {
-    baseline: {
-      note: "Grouped projects, an open tab, local and cloud placement, status marks, and the account footer.",
-      props: baseProps,
-    },
-    "trust-pending": {
-      note: "An agent's sub-session waits for a folder's trust: its row says Needs trust, in the amber of the question card, instead of Needs your input.",
-      props: { ...baseProps, sessions: trustWaiting, selectedId: "sidebar-first", groupProjects: false },
-    },
-    "search-filtered": {
-      note: "Search narrows rows by title, branch, project or host while preserving project context.",
-      props: { ...baseProps, groupProjects: false },
-      play: search,
-      checks: searchChecks,
-    },
-    "search-clears": {
-      note: "Escape clears the sidebar query before it can dismiss the surrounding surface.",
-      props: { ...baseProps, groupProjects: false },
-      play: searchThenClear,
-      checks: searchChecks,
-    },
-    "row-keyboard": {
-      note: "ArrowDown, End and Home move through visible session rows without leaving the list.",
-      props: { ...baseProps, groupProjects: false },
-      play: rowKeyboard,
-    },
-    "rail-keyboard": {
-      note: "The rail skips disabled controls and follows ArrowDown, End and Home through its views.",
-      props: baseProps,
-      play: railKeyboard,
-    },
-    "view-switching": {
-      note: "History, Pull requests and Closed sessions each replace the list in the same pane.",
-      props: baseProps,
-      play: switchViews,
-    },
-    "view-switching-animation-audit": {
-      note: "Rapidly round-trip the sidebar rail through History, Pull requests, Closed sessions and Sessions. The shared play report is the animation receipt: frame timing, settle latency, layout shift and sidebar geometry are checked together.",
-      props: baseProps,
-      checks: {
-        layoutShiftMax: {
-          value: 0,
-          reason: "Workspace/sidebar view switches replace the scroll content without moving the sidebar frame.",
-        },
-        longFrameFailMs: {
-          value: 33,
-          reason: "Rail view switches should not introduce a long animation frame over two display frames.",
-        },
-        settleMaxMs: {
-          value: 250,
-          reason: "Each local rail transition should settle within a quarter second for rapid workspace review.",
-        },
-      },
-      play: animationAudit,
-    },
-    "context-actions": {
-      note: "Right-click an active row to Settle and a settled row to Continue; each menu returns focus cleanly.",
-      props: {
-        ...baseProps,
-        sessions: [active],
-        settledSessions: [settled],
-        groupProjects: false,
-        onSettle: () => undefined,
-        onContinue: () => undefined,
-      },
-      play: contextActions,
-    },
-    "hover-preview": {
-      note: "A deliberate hover opens the latest reply with status and placement metadata in a floating card.",
-      props: { ...baseProps, groupProjects: false },
-      play: hoverPreview,
-    },
-    "hover-preview-quiet": {
-      note: "Debug layout sidebarPreviewVariant=quiet: a narrower, flatter latest-reply card keeps metadata readable with less elevation.",
-      props: { ...baseProps, groupProjects: false, previewVariant: "quiet" },
-      play: hoverPreview,
-    },
-    "hover-preview-outline": {
-      note: "Debug layout sidebarPreviewVariant=outline: a lightly tinted rim keeps the latest-reply card distinct without a drop shadow.",
-      props: { ...baseProps, groupProjects: false, previewVariant: "outline" },
-      play: hoverPreview,
-    },
-    "focus-preview": {
-      note: "Keyboard focus opens the same preview without changing the sidebar row geometry.",
-      props: { ...baseProps, groupProjects: false },
-      play: focusPreview,
-    },
-    "no-preview": {
-      note: "Rows without a latest reply remain compact and do not mount a preview card.",
-      props: { ...baseProps, sessions: sessionsWithoutPreview, groupProjects: false },
-    },
-  },
-});
-
-export default entry;
diff --git a/webviews/src/agent-session/acpmux/SessionSidebar.tsx b/webviews/src/agent-session/acpmux/SessionSidebar.tsx
deleted file mode 100644
index 8b8f3ccccb9a..000000000000
--- a/webviews/src/agent-session/acpmux/SessionSidebar.tsx
+++ /dev/null
@@ -1,704 +0,0 @@
-import React, { createContext, memo, useContext, useEffect, useId, useMemo, useRef, useState } from "react";
-import {
-  filterSessions,
-  groupMark,
-  activityTime,
-  sessionMark,
-  sessionPlace,
-  sortByRecency,
-  shortAge,
-  sidebarSections,
-  visibleSessions,
-  type AcpmuxSessionEntry,
-  type SessionMark,
-} from "./sessionList";
-import { type StringKey, useT } from "./i18n";
-
-import { Icon } from "./icons/Icon";
-import { rowIconSize } from "./icons/iconSize";
-import { ContextMenu, type ContextMenuItem } from "../../ui/ContextMenu";
-import { listRowKeyboardProps } from "../../ui/listRowKeyboard";
-import { pressToOpen } from "../../ui/pressToOpen";
-import { AnchoredCard } from "../../ui/Tooltip";
-import { HOVER_INTENT, HoverGroup, useHoverIntent } from "../../ui/hoverIntent";
-import { useSidebarPreviewVariant, type SidebarPreviewVariant } from "./sidebarPreview";
-
-const MARK_LABELS = {
-  input: "sidebar.markInput",
-  running: "sidebar.markRunning",
-  error: "sidebar.markError",
-  unread: "sidebar.markUnread",
-} as const satisfies Record<Exclude<SessionMark, undefined>, StringKey>;
-/** Sidebar rows set 13px text, so their icons draw at the registry's row size for it. */
-const ROW_ICON = rowIconSize(13);
-/** The rail's icon-only buttons keep the 18px glyphs' footprint: a 15px row crop inks about 14px. */
-const RAIL_ICON = 15;
-const MARK_GLYPHS: Record<Exclude<SessionMark, undefined>, React.ReactNode> = {
-  input: <Icon name="status.needsinput" size={ROW_ICON} row />,
-  running: <Icon name="status.running" size={ROW_ICON} row />,
-  error: <Icon name="status.disconnected" size={ROW_ICON} row />,
-  unread: null,
-};
-/** Where a session runs is secondary to its title, so its glyph takes the caption size (11px text). */
-const PLACE_ICON = rowIconSize(11);
-const PLACE_GLYPHS = {
-  cloud: <Icon name="cloud" size={PLACE_ICON} row />,
-  worktree: <Icon name="git.worktree" size={PLACE_ICON} row />,
-  branch: <Icon name="git.branch" size={PLACE_ICON} row />,
-};
-const PLACE_LABELS = {
-  cloud: "sidebar.runsOn",
-  worktree: "sidebar.worktree",
-  branch: "sidebar.branch",
-} as const satisfies Record<string, StringKey>;
-
-/** Sidebar previews are one warm hover-card group, so moving between rows does not replay the dwell. */
-const sessionPreviewGroup = new HoverGroup(HOVER_INTENT.cardGrace);
-
-/** What the rail switches the list to. */
-export type SidebarView = "sessions" | "history" | "pulls" | "closed";
-export type SidebarAccount = { name: string; detail?: string };
-
-const VIEW_TITLES = {
-  history: "sidebar.history",
-  pulls: "sidebar.pulls",
-  closed: "sidebar.closed",
-} as const satisfies Record<Exclude<SidebarView, "sessions">, StringKey>;
-
-/** Sessions already open in a tab, when the list is a history layer beside them. */
-const OpenSessions = createContext<ReadonlySet<string> | undefined>(undefined);
-
-/** The pane's sidebar: an icon rail, the list it switches, and the account at the bottom. */
-export function SessionSidebar({
-  sessions,
-  settledSessions = [],
-  selectedId,
-  openIds,
-  onSelect,
-  onNewChat,
-  account,
-  preview = false,
-  previewVariant,
-  groupProjects = false,
-  onContinue,
-  onSettle,
-  onShowMoreSettled,
-}: {
-  sessions: AcpmuxSessionEntry[];
-  /** Read-only history from the `_acpmux/chat_settled` seam. */
-  settledSessions?: AcpmuxSessionEntry[];
-  selectedId?: string;
-  /** Sessions already open in a tab; their rows say so, and opening one jumps to it. */
-  openIds?: ReadonlySet<string>;
-  onSelect: (sessionId: string) => void;
-  onNewChat?: () => void;
-  account?: SidebarAccount;
-  /** Preview features are on (`labs.previewFeatures`): show Pull requests and session hover cards. */
-  preview?: boolean;
-  /** DEV/NIGHTLY visual trial; defaults to the shared `card` treatment. */
-  previewVariant?: SidebarPreviewVariant;
-  /** Preserves project grouping as an option while keeping the default compact and ungrouped. */
-  groupProjects?: boolean;
-  onContinue?: (sessionIds: string[]) => void;
-  onSettle?: (sessionIds: string[]) => void;
-  onShowMoreSettled?: () => void;
-}) {
-  const t = useT();
-  const activePreviewVariant = useSidebarPreviewVariant(previewVariant);
-  const [picked, setView] = useState<SidebarView>("sessions");
-  // Pull requests turned off while shown falls back to the session list, and stays there.
-  const view = picked === "pulls" && !preview ? "sessions" : picked;
-  useEffect(() => {
-    if (!preview) setView((current) => (current === "pulls" ? "sessions" : current));
-  }, [preview]);
-  // Kept here so expanded projects and a search survive a trip to another rail view.
-  const [expanded, setExpanded] = useState<Set<string>>(new Set());
-  const [query, setQuery] = useState("");
-  const needsInput = useMemo(
-    () => sessions.some((session) => sessionMark(session, session.sessionId === selectedId) === "input"),
-    [sessions, selectedId],
-  );
-  return (
-    <OpenSessions.Provider value={openIds}>
-      <nav className="acpmux-sidebar" id="acpmux-sidebar" data-list-keyboard aria-label={t("sidebar.label")}>
-        <div className="acpmux-sidebar-rail" data-list-keyboard>
-          <RailButton label={t("picker.newChat")} title={t("picker.newChat")} onClick={onNewChat} icon="home" />
-
-          <RailButton
-            label={t("sidebar.sessions")}
-            current={view === "sessions"}
-            dot={needsInput}
-            onClick={() => setView("sessions")}
-            icon="agent.chat.list"
-          />
-          <RailButton
-            label={t("sidebar.history")}
-            current={view === "history"}
-            onClick={() => setView("history")}
-            icon="history"
-          />
-          {preview && (
-            <RailButton
-              label={t("sidebar.pulls")}
-              current={view === "pulls"}
-              onClick={() => setView("pulls")}
-              icon="git.pullrequest"
-            />
-          )}
-          <RailButton
-            label={t("sidebar.closed")}
-            title={t("sidebar.closedTitle")}
-            current={view === "closed"}
-            onClick={() => setView("closed")}
-            icon="action.more"
-          />
-        </div>
-        <div className="acpmux-sidebar-body">
-          <div className="acpmux-sidebar-scroll">
-            {view === "sessions" ? (
-              <SessionsView
-                sessions={sessions}
-                selectedId={selectedId}
-                onSelect={onSelect}
-                onNewChat={onNewChat}
-                query={query}
-                onQuery={setQuery}
-                expanded={expanded}
-                onExpand={(key) => setExpanded((current) => new Set(current).add(key))}
-                settledSessions={settledSessions}
-                groupProjects={groupProjects}
-                preview={preview}
-                previewVariant={activePreviewVariant}
-                onContinue={onContinue}
-                onSettle={onSettle}
-                onShowMoreSettled={onShowMoreSettled}
-              />
-            ) : (
-              <FlatView
-                view={view}
-                sessions={sessions}
-                selectedId={selectedId}
-                onSelect={onSelect}
-                preview={preview}
-                previewVariant={activePreviewVariant}
-              />
-            )}
-          </div>
-          {account && (
-            <div className="acpmux-account">
-              <span className="acpmux-avatar" aria-hidden="true">
-                {account.name.slice(0, 1).toUpperCase()}
-              </span>
-              <span className="acpmux-account-name">{account.name}</span>
-              {account.detail && <span className="acpmux-account-detail">{account.detail}</span>}
-            </div>
-          )}
-        </div>
-      </nav>
-    </OpenSessions.Provider>
-  );
-}
-
-function RailButton({
-  label,
-  title,
-  icon,
-  current,
-  dot,
-  onClick,
-}: {
-  label: string;
-  title?: string;
-  /** The registry name of the button's glyph. */
-  icon: string;
-  current?: boolean;
-  dot?: boolean;
-  onClick?: () => void;
-}) {
-  const t = useT();
-  const keyboard = listRowKeyboardProps(".acpmux-rail-button:not(:disabled)", (row) => row.click());
-  return (
-    <button
-      {...keyboard}
-      type="button"
-      className="acpmux-rail-button"
-      aria-label={dot ? t("sidebar.needsInput", { label }) : label}
-      title={title ?? label}
-      aria-current={current ? "page" : undefined}
-      disabled={!onClick}
-      onClick={onClick}
-    >
-      <Icon name={icon} size={RAIL_ICON} row selected={current} />
-      {dot && <span className="acpmux-rail-dot" aria-hidden="true" />}
-    </button>
-  );
-}
-
-/** Pinned sessions, then every other acpmux session grouped by folder, newest first. */
-function SessionsView({
-  sessions,
-  settledSessions,
-  selectedId,
-  onSelect,
-  onNewChat,
-  query,
-  onQuery,
-  expanded,
-  onExpand,
-  groupProjects,
-  preview,
-  previewVariant,
-  onContinue,
-  onSettle,
-  onShowMoreSettled,
-}: {
-  sessions: AcpmuxSessionEntry[];
-  settledSessions: AcpmuxSessionEntry[];
-  selectedId?: string;
-  onSelect: (sessionId: string) => void;
-  onNewChat?: () => void;
-  query: string;
-  onQuery: (query: string) => void;
-  expanded: Set<string>;
-  onExpand: (groupKey: string) => void;
-  groupProjects: boolean;
-  preview: boolean;
-  previewVariant: SidebarPreviewVariant;
-  onContinue?: (sessionIds: string[]) => void;
-  onSettle?: (sessionIds: string[]) => void;
-  onShowMoreSettled?: () => void;
-}) {
-  const t = useT();
-  const newChat = onNewChat && (
-    <button type="button" className="acpmux-sidebar-action" onClick={onNewChat}>
-      <Icon name="agent.chat.new" size={ROW_ICON} row />
-      <span>{t("sidebar.newChat")}</span>
-    </button>
-  );
-  const searching = query.trim() !== "";
-  const { pinned, groups, active } = useMemo(
-    () => sidebarSections(sessions, query, groupProjects),
-    [sessions, query, groupProjects],
-  );
-  const settled = useMemo(() => sortByRecency(filterSessions(settledSessions, query)), [settledSessions, query]);
-  // Grouped by project, the shown chats are in `groups` and `active` is empty.
-  const noMatches = pinned.length === 0 && active.length === 0 && groups.length === 0 && settled.length === 0;
-  if (sessions.length === 0 && settledSessions.length === 0)
-    return (
-      <>
-        {newChat}
-        <div className="acpmux-sidebar-empty">{t("sidebar.noSessions")}</div>
-      </>
-    );
-  // Escape clears a query first; with the field empty it reaches the overlay, which closes.
-  const onSearchKey = (event: React.KeyboardEvent<HTMLInputElement>) => {
-    if (event.key !== "Escape") return;
-    // During IME composition Escape cancels the composition, and closes nothing.
-    // WebKit can end the composition before this keydown, which then reports only keyCode 229.
-    const composing = event.nativeEvent.isComposing || event.nativeEvent.keyCode === 229;
-    if (!composing && !query) return;
-    event.stopPropagation();
-    if (!composing) onQuery("");
-  };
-  return (
-    <>
-      {newChat}
-      <search className="acpmux-sidebar-search">
-        <label>
-          <Icon name="search" size={ROW_ICON} row />
-          <input
-            type="search"
-            aria-label={t("sidebar.search")}
-            placeholder={t("sidebar.searchPlaceholder")}
-            spellCheck={false}
-            value={query}
-            onChange={(event) => onQuery(event.target.value)}
-            onKeyDown={onSearchKey}
-          />
-        </label>
-      </search>
-      {/* Always present, so a screen reader announces the text when it appears. */}
-      <output className="acpmux-sidebar-empty">{noMatches ? t("sidebar.noMatches") : ""}</output>
-      {pinned.length > 0 && (
-        <section className="acpmux-sidebar-pinned" aria-label={t("sidebar.pinned")}>
-          <div className="acpmux-sidebar-section" aria-hidden="true">
-            {t("sidebar.pinned")}
-          </div>
-          <ul>
-            {pinned.map((session) => (
-              <SessionRow
-                key={session.sessionId}
-                session={session}
-                preview={preview}
-                previewVariant={previewVariant}
-                selected={session.sessionId === selectedId}
-                onSelect={onSelect}
-                section="active"
-                onSettle={onSettle}
-              />
-            ))}
-          </ul>
-        </section>
-      )}
-      {active.length > 0 && !groupProjects && (
-        <section className="acpmux-sidebar-active" aria-label={t("sidebar.active")}>
-          <div className="acpmux-sidebar-section" aria-hidden="true">
-            {t("sidebar.active")}
-          </div>
-          <ul>
-            {active.map((session) => (
-              <SessionRow
-                key={session.sessionId}
-                session={session}
-                preview={preview}
-                previewVariant={previewVariant}
-                selected={session.sessionId === selectedId}
-                onSelect={onSelect}
-                section="active"
-                onSettle={onSettle}
-                flat
-              />
-            ))}
-          </ul>
-        </section>
-      )}
-      {groups.length > 0 && groupProjects && (
-        <section className="acpmux-sidebar-projects" aria-label={t("sidebar.projects")}>
-          <div className="acpmux-sidebar-section" aria-hidden="true">
-            {t("sidebar.projects")}
-          </div>
-          {groups.map((group) => {
-            // A search shows every match, so it never hides rows behind "Show more".
-            const { rows, hidden } = visibleSessions(group, searching || expanded.has(group.key), selectedId);
-            const mark = groupMark(group, selectedId);
-            return (
-              <section className="acpmux-sidebar-group" key={group.key}>
-                <div className="acpmux-sidebar-project">
-                  <Icon name="folder" size={ROW_ICON} row />
-                  <span>{group.label}</span>
-                  {group.host && <small className="acpmux-sidebar-host">{group.host}</small>}
-                  {mark && (
-                    <span className={`acpmux-session-mark acpmux-session-mark-${mark}`} title={t(MARK_LABELS[mark])}>
-                      {MARK_GLYPHS[mark]}
-                      <span className="acpmux-hidden-label">{t(MARK_LABELS[mark])}</span>
-                    </span>
-                  )}
-                </div>
-                <ul>
-                  {rows.map((session) => (
-                    <SessionRow
-                      key={session.sessionId}
-                      session={session}
-                      preview={preview}
-                      previewVariant={previewVariant}
-                      selected={session.sessionId === selectedId}
-                      groupHost={group.host}
-                      onSelect={onSelect}
-                      section="active"
-                      onSettle={onSettle}
-                    />
-                  ))}
-                </ul>
-                {hidden > 0 && (
-                  <button
-                    type="button"
-                    className="acpmux-sidebar-more"
-                    onClick={() => onExpand(group.key)}
-                    aria-label={t("sidebar.showMoreHidden", { n: hidden })}
-                  >
-                    {t("sidebar.showMore")}
-                  </button>
-                )}
-              </section>
-            );
-          })}
-        </section>
-      )}
-      {/* With nothing matching, the line above says so once; an empty Settled would repeat it. */}
-      {!noMatches && (
-        <section className="acpmux-sidebar-settled" aria-label={t("sidebar.settled")}>
-          <div className="acpmux-sidebar-section" aria-hidden="true">
-            {t("sidebar.settled")}
-          </div>
-          {settled.length === 0 ? (
-            <div className="acpmux-sidebar-empty">
-              {settledSessions.length > 0 && query.trim() ? t("sidebar.noMatches") : t("sidebar.noSettled")}
-            </div>
-          ) : (
-            <ul>
-              {settled.map((session) => (
-                <SessionRow
-                  key={session.sessionId}
-                  session={session}
-                  preview={preview}
-                  previewVariant={previewVariant}
-                  selected={session.sessionId === selectedId}
-                  onSelect={onSelect}
-                  section="settled"
-                  onContinue={onContinue}
-                  flat
-                />
-              ))}
-            </ul>
-          )}
-          {onShowMoreSettled && settled.length > 0 && (
-            <button type="button" className="acpmux-sidebar-more" onClick={onShowMoreSettled}>
-              {t("sidebar.showMore")}
-            </button>
-          )}
-        </section>
-      )}
-    </>
-  );
-}
-
-/** History, pull requests and closed sessions: one list, newest first. */
-function FlatView({
-  view,
-  sessions,
-  selectedId,
-  onSelect,
-  preview,
-  previewVariant,
-}: {
-  view: Exclude<SidebarView, "sessions">;
-  sessions: AcpmuxSessionEntry[];
-  selectedId?: string;
-  onSelect: (sessionId: string) => void;
-  preview: boolean;
-  previewVariant: SidebarPreviewVariant;
-}) {
-  const t = useT();
-  // Pull requests appear once the session summary reports them; until then the view says so.
-  const rows = useMemo(
-    () =>
-      view === "pulls"
-        ? []
-        : sessions
-            .filter((session) => view === "history" || session.status === "closed")
-            .sort((left, right) => (activityTime(right) ?? 0) - (activityTime(left) ?? 0)),
-    [sessions, view],
-  );
-  const now = Date.now();
-  return (
-    <section aria-label={t(VIEW_TITLES[view])}>
-      <h2 className="acpmux-sidebar-title">{t(VIEW_TITLES[view])}</h2>
-      {rows.length === 0 ? (
-        <div className="acpmux-sidebar-empty">{view === "pulls" ? t("sidebar.noPulls") : t("sidebar.nothing")}</div>
-      ) : (
-        <ul>
-          {rows.map((session) => (
-            <SessionRow
-              key={session.sessionId}
-              session={session}
-              preview={preview}
-              previewVariant={previewVariant}
-              selected={session.sessionId === selectedId}
-              onSelect={onSelect}
-              flat
-              trailing={shortAge(activityTime(session), now, t)}
-            />
-          ))}
-        </ul>
-      )}
-    </section>
-  );
-}
-
-const SessionRow = memo(function SessionRow({
-  session,
-  preview,
-  previewVariant,
-  selected,
-  groupHost,
-  onSelect,
-  flat,
-  trailing,
-  section,
-  onContinue,
-  onSettle,
-}: {
-  session: AcpmuxSessionEntry;
-  preview: boolean;
-  previewVariant: SidebarPreviewVariant;
-  selected: boolean;
-  groupHost?: string;
-  onSelect: (sessionId: string) => void;
-  flat?: boolean;
-  trailing?: string;
-  section?: "active" | "settled";
-  onContinue?: (sessionIds: string[]) => void;
-  onSettle?: (sessionIds: string[]) => void;
-}) {
-  const t = useT();
-  const open = useContext(OpenSessions)?.has(session.sessionId);
-  const mark = sessionMark(session, selected);
-  const title = session.displayTitle || session.sessionId.slice(0, 8);
-  const place = sessionPlace(session, groupHost);
-  const previewText = preview ? session.preview?.trim() : undefined;
-  const previewId = useId();
-  const previewIntent = useHoverIntent<HTMLElement>({ delay: HOVER_INTENT.cardDwell, group: sessionPreviewGroup });
-  const { dismiss: dismissPreview } = previewIntent;
-  const previewLeaveTimer = useRef<ReturnType<typeof setTimeout> | undefined>(undefined);
-  const [placedPreview, setPlacedPreview] = useState<HTMLElement | null>(null);
-  useEffect(() => {
-    if (previewIntent.shown) setPlacedPreview(previewIntent.shown);
-  }, [previewIntent.shown]);
-  useEffect(() => {
-    if (!previewText) {
-      clearTimeout(previewLeaveTimer.current);
-      previewLeaveTimer.current = undefined;
-      dismissPreview();
-    }
-  }, [dismissPreview, previewText]);
-  useEffect(() => () => clearTimeout(previewLeaveTimer.current), []);
-  const cancelPreviewLeave = () => {
-    clearTimeout(previewLeaveTimer.current);
-    previewLeaveTimer.current = undefined;
-  };
-  const hoverPreview = (anchor: HTMLElement, delay?: number) => {
-    cancelPreviewLeave();
-    previewIntent.hover(anchor, delay);
-  };
-  const leavePreviewRow = () => {
-    cancelPreviewLeave();
-    if (!previewIntent.shown) {
-      previewIntent.hover(null);
-      return;
-    }
-    previewLeaveTimer.current = setTimeout(() => {
-      previewLeaveTimer.current = undefined;
-      previewIntent.hover(null);
-    }, HOVER_INTENT.cardGrace);
-  };
-  const leavePreviewCard = () => {
-    cancelPreviewLeave();
-    previewIntent.hover(null);
-  };
-  const dismissPreviewNow = () => {
-    cancelPreviewLeave();
-    dismissPreview();
-  };
-  const keyboard = listRowKeyboardProps(".acpmux-session-row", (row) => {
-    const sessionId = row.dataset.sessionId;
-    if (sessionId) onSelect(sessionId);
-  });
-  const placeLabel =
-    place &&
-    `${t(PLACE_LABELS[place.kind])} ${place.label}${place.branch ? `, ${t(PLACE_LABELS.branch)} ${place.branch}` : ""}`;
-  // A chat whose sub-session waits for a folder's trust says so, not just "Needs your input".
-  const markKey: StringKey | undefined =
-    mark && (mark === "input" && session.trustPending ? "sidebar.markTrust" : MARK_LABELS[mark]);
-  const previewStatus = markKey ? t(markKey) : undefined;
-  const menuItems: ContextMenuItem[] = [];
-  if (section === "settled" && onContinue) {
-    menuItems.push({
-      id: "continue",
-      label: t("sidebar.continue"),
-      onSelect: () => onContinue([session.sessionId]),
-    });
-  }
-  if (section === "active" && onSettle) {
-    menuItems.push({
-      id: "settle",
-      label: t("sidebar.settle"),
-      onSelect: () => onSettle([session.sessionId]),
-    });
-  }
-  const row = (
-    <button
-      {...keyboard}
-      type="button"
-      data-session-id={session.sessionId}
-      data-focus-ring="row"
-      className={`acpmux-session-row${flat ? " is-flat" : ""}${selected ? " is-selected" : ""}${open ? " is-open" : ""}${session.status === "closed" ? " is-closed" : ""}`}
-      aria-current={selected ? "true" : undefined}
-      aria-describedby={previewText && previewIntent.shown ? previewId : undefined}
-      aria-label={
-        mark || place || trailing || open
-          ? [title, open && t("sidebar.alreadyOpen"), trailing, placeLabel, markKey && t(markKey)]
-              .filter(Boolean)
-              .join(", ")
-          : undefined
-      }
-      onPointerEnter={(event) => previewText && hoverPreview(event.currentTarget)}
-      onPointerLeave={leavePreviewRow}
-      onPointerDown={dismissPreviewNow}
-      // Opens on the press, as the native sidebar rows do; Enter and Space still click.
-      {...pressToOpen(() => onSelect(session.sessionId))}
-      onFocus={(event) => previewText && hoverPreview(event.currentTarget, 0)}
-      onBlur={leavePreviewCard}
-      // ui-allow: Escape dismisses this row's anchored preview; arrow/Home/End navigation stays in the shared helper.
-      onKeyDown={(event) => {
-        keyboard.onKeyDown?.(event);
-        if (event.key === "Escape") dismissPreviewNow();
-      }}
-    >
-      <span className="acpmux-session-row-title">{title}</span>
-      {trailing && (
-        <span className="acpmux-session-trailing" aria-hidden="true">
-          {trailing}
-        </span>
-      )}
-      {place && (
-        <span className={`acpmux-session-place acpmux-session-place-${place.kind}`} aria-hidden="true">
-          {PLACE_GLYPHS[place.kind]}
-        </span>
-      )}
-      {mark === "input" ? (
-        // A chat waiting on the person says so in amber, like the question card's pill.
-        <span className="acpmux-session-mark acpmux-session-mark-input acpmux-session-mark-labeled" aria-hidden="true">
-          {MARK_GLYPHS.input}
-          {t(markKey ?? MARK_LABELS.input)}
-        </span>
-      ) : mark ? (
-        <span
-          className={`acpmux-session-mark acpmux-session-mark-${mark}`}
-          aria-hidden="true"
-          title={t(markKey ?? MARK_LABELS[mark])}
-        >
-          {MARK_GLYPHS[mark]}
-        </span>
-      ) : (
-        // Keeps place glyphs in one column.
-        place && <span className="acpmux-session-mark" aria-hidden="true" />
-      )}
-    </button>
-  );
-  return (
-    <li>
-      {menuItems.length > 0 ? <ContextMenu items={menuItems}>{row}</ContextMenu> : row}
-      {previewText && placedPreview && (
-        <AnchoredCard
-          id={previewId}
-          anchor={placedPreview}
-          open={previewIntent.shown !== null}
-          side="inline-end"
-          className={`acpmux-session-preview acpmux-session-preview-${previewVariant}`}
-          instant={previewIntent.instant}
-          onPointerEnter={cancelPreviewLeave}
-          onPointerLeave={leavePreviewCard}
-        >
-          <div className="acpmux-session-preview-title">{title}</div>
-          <div className="acpmux-session-preview-copy">{previewText}</div>
-          {(previewStatus || placeLabel) && (
-            <div className="acpmux-session-preview-meta">
-              {previewStatus && (
-                <span className={`acpmux-session-preview-status acpmux-session-mark-${mark}`}>
-                  {mark && MARK_GLYPHS[mark]}
-                  {previewStatus}
-                </span>
-              )}
-              {placeLabel && (
-                <span className="acpmux-session-preview-place">
-                  {place && PLACE_GLYPHS[place.kind]}
-                  {placeLabel}
-                </span>
-              )}
-            </div>
-          )}
-        </AnchoredCard>
-      )}
-    </li>
-  );
-});
diff --git a/webviews/src/agent-session/acpmux/prototype/WorkspaceShell.tsx b/webviews/src/agent-session/acpmux/prototype/WorkspaceShell.tsx
index 123fb5d16e37..9d755b961441 100644
--- a/webviews/src/agent-session/acpmux/prototype/WorkspaceShell.tsx
+++ b/webviews/src/agent-session/acpmux/prototype/WorkspaceShell.tsx
@@ -1,5 +1,5 @@
 // Sidebar prototype (#16688), dev server only: prototype.html. One stack of open workspaces is the
-// main sidebar; agent history (the pane's project-grouped session list) is a layer opened from the
+// main sidebar; agent history (a plain list of the fixture's sessions) is a layer opened from the
 // rail, and opening a row there jumps to the tab already showing it instead of opening a copy.
 // Dots at the bottom switch spaces, and links from a terminal open in the mini window
 // until Cmd-O promotes them into the workspace. Rows are minimal unless `sidebar.rowDetail` (the
@@ -7,8 +7,7 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { AcpmuxApp } from "../App";
 import { mockSessions, sessionSummary } from "../mockFixture";
-import { SessionSidebar } from "../SessionSidebar";
-import { sessionEntry, sessionMark, type AcpmuxSessionEntry } from "../sessionList";
+import { sessionEntry, sessionMark, sessionTitle, type AcpmuxSessionEntry } from "../sessionList";
 import { Icon } from "../icons/Icon";
 import { rowIconSize } from "../icons/iconSize";
 import {
@@ -341,12 +340,24 @@ export function WorkspaceShell() {
                 <CloseIcon />
               </button>
             </header>
-            <SessionSidebar
-              sessions={history}
-              selectedId={activeTab.sessionId}
-              openIds={openIds}
-              onSelect={openSession}
-            />
+            <ul className="proto-history-list">
+              {history.map((session) => {
+                const open = openIds.has(session.sessionId);
+                return (
+                  <li key={session.sessionId}>
+                    <button
+                      type="button"
+                      className={`proto-history-row${open ? " is-open" : ""}`}
+                      aria-current={session.sessionId === activeTab.sessionId ? "true" : undefined}
+                      onClick={() => openSession(session.sessionId)}
+                    >
+                      <span>{sessionTitle(session)}</span>
+                      {open && <small>Open</small>}
+                    </button>
+                  </li>
+                );
+              })}
+            </ul>
           </aside>
         </>
       )}
diff --git a/webviews/src/agent-session/acpmux/prototype/prototype.css b/webviews/src/agent-session/acpmux/prototype/prototype.css
index 9f1d4be9cc88..3fbf4ecb7a66 100644
--- a/webviews/src/agent-session/acpmux/prototype/prototype.css
+++ b/webviews/src/agent-session/acpmux/prototype/prototype.css
@@ -421,31 +421,53 @@ body {
 .proto-history header button:hover {
   background: color-mix(in srgb, var(--agent-text) 6%, transparent);
 }
-.proto-history .acpmux-sidebar {
-  display: flex;
-  position: static;
+.proto-history-list {
   flex: 1;
   min-height: 0;
-  width: auto;
+  margin: 0;
+  padding: 4px 8px 16px;
+  list-style: none;
+  overflow-y: auto;
+}
+.proto-history-row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  width: 100%;
+  height: 30px;
+  padding: 0 8px;
   border: 0;
+  border-radius: 7px;
   background: none;
-  box-shadow: none;
+  color: var(--agent-soft, var(--agent-muted));
+  font: inherit;
+  font-size: var(--text-body);
+  text-align: start;
 }
-.proto-history .acpmux-sidebar-scroll {
-  padding: 4px 8px 16px;
+.proto-history-row > span {
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.proto-history-row:hover {
+  background: color-mix(in srgb, var(--agent-text) 6%, transparent);
+}
+.proto-history-row[aria-current] {
+  background: color-mix(in srgb, var(--agent-text) 10%, transparent);
 }
 /* Rows already open in a tab read at full strength and say so; the rest are history. */
-.proto-history .acpmux-session-row:not(.is-open) {
-  color: var(--agent-soft, var(--agent-muted));
+.proto-history-row.is-open {
+  color: var(--agent-text);
 }
-.proto-history .acpmux-session-row.is-open::after {
-  content: "Open";
+.proto-history-row > small {
   flex: none;
   padding: 0 5px;
   border: var(--cmux-hairline, 0.5px) solid var(--agent-border);
   border-radius: 4px;
   color: var(--agent-muted);
-  font-size: 11px;
+  font-size: var(--text-caption);
   line-height: 16px;
 }
 
@@ -540,12 +562,6 @@ body {
 .proto-agent[hidden] {
   display: none;
 }
-/* The pane's own session list is the history layer now. */
-.proto-agent .acpmux-sidebar,
-.proto-agent .acpmux-sidebar-toggle,
-.proto-agent .acpmux-sidebar-scrim {
-  display: none !important;
-}
 .proto-terminal {
   height: 100%;
   margin: 0;
@@ -794,12 +810,6 @@ body {
     backdrop-filter: none;
   }
 }
-/* The history layer is the session list alone: the pane's own rail and New chat stay in the pane. */
-.proto-history .acpmux-sidebar-rail,
-.proto-history .acpmux-sidebar-action,
-.proto-history .acpmux-account {
-  display: none;
-}
 
 /* Classic cmux (?style=terminal): the chrome takes the terminal's font and agent sessions are one
    kind among others, drawn as quietly as terminals and browsers. Translucency is the backdrop
diff --git a/webviews/src/agent-session/acpmux/sessionList.ts b/webviews/src/agent-session/acpmux/sessionList.ts
index b4a5d4d08acf..ff6c0eb3daca 100644
--- a/webviews/src/agent-session/acpmux/sessionList.ts
+++ b/webviews/src/agent-session/acpmux/sessionList.ts
@@ -89,14 +89,6 @@ export const text = (value: unknown) => (typeof value === "string" && value ? va
 /** "local" or "cloud", else undefined. */
 export const hostKind = (value: unknown) => (value === "local" || value === "cloud" ? value : undefined);
 
-export type SessionGroup = {
-  key: string;
-  label: string;
-  cwd?: string;
-  host?: string;
-  sessions: AcpmuxSessionEntry[];
-};
-
 /** The tag that pins a session to the top of the list. */
 export const PINNED_TAG = "pinned";
 /** The tag the chat menu's Archive sets. */
@@ -146,9 +138,6 @@ const INDICATORS: readonly string[] = ["input", "working", "failed", "lost", "do
 /** What a row draws at its right edge, most urgent first. */
 export type SessionMark = "input" | "running" | "error" | "unread" | undefined;
 
-/** A long group shows this many rows and a "Show more" (the TUI's GROUP_ROWS). */
-export const GROUP_ROWS = 6;
-
 /** Cuts acpmux's session summary down to the fields the pane uses. */
 export function sessionEntry(session: Record<string, any> & { sessionId: string }): AcpmuxSessionEntry {
   const pending = Number(session.pendingPermissions ?? 0);
@@ -345,71 +334,10 @@ function byRecency(sessions: AcpmuxSessionEntry[]): AcpmuxSessionEntry[] {
   return [...sessions].sort((left, right) => (activityTime(right) ?? 0) - (activityTime(left) ?? 0));
 }
 
-/** A stable newest-first view for ungrouped sidebar sections. */
-export function sortByRecency(sessions: AcpmuxSessionEntry[]): AcpmuxSessionEntry[] {
-  return byRecency(sessions);
-}
-
-// Session entries are immutable snapshots. Reuse the assembled, case-folded search text while a
-// user types so each sidebar keystroke does not rebuild every title/path/branch string. A weak map
-// releases entries when the session snapshot is replaced.
-const sessionSearchTextCache = new WeakMap<AcpmuxSessionEntry, string>();
-
-function sessionSearchText(session: AcpmuxSessionEntry): string {
-  const cached = sessionSearchTextCache.get(session);
-  if (cached !== undefined) return cached;
-  const text = [
-    session.displayTitle,
-    session.title,
-    session.name,
-    session.cwd && projectLabel(session.cwd),
-    session.branch,
-    session.worktree && projectLabel(session.worktree),
-    cloudHost(session),
-  ]
-    .filter(Boolean)
-    .join("\n")
-    .toLowerCase();
-  sessionSearchTextCache.set(session, text);
-  return text;
-}
-
-/** Sessions under one header per folder (a cloud-only folder per machine). Groups follow their most recent session; sessions stay newest first. */
-export function groupByProject(
-  sessions: AcpmuxSessionEntry[],
-  // Every session, pinned ones too, so pinning a local session doesn't regroup its cloud siblings.
-  all: AcpmuxSessionEntry[] = sessions,
-): SessionGroup[] {
-  const folder = (session: AcpmuxSessionEntry) => (session.cwd ?? "").replace(/\/+$/, "");
-  // A cloud session joins the local project at the same path; otherwise its folder is only
-  // known on its machine, so `/workspace` on two machines stays two projects.
-  const local = new Set(all.filter((session) => !cloudHost(session)).map(folder));
-  const groups = new Map<string, SessionGroup>();
-  for (const session of byRecency(sessions)) {
-    const cwd = folder(session);
-    const host = cloudHost(session);
-    const key = host && !local.has(cwd) ? `${host}:${cwd}` : cwd;
-    let group = groups.get(key);
-    if (!group) {
-      group = { key, label: projectLabel(cwd), cwd: cwd || undefined, sessions: [] };
-      groups.set(key, group);
-    }
-    group.sessions.push(session);
-  }
-  for (const group of groups.values()) group.host = sharedCloudHost(group.sessions);
-  return [...groups.values()];
-}
-
 /** The remote machine a session runs on. A host not marked local counts as remote; this Mac is never named. */
 export const cloudHost = (session: AcpmuxSessionEntry) =>
   session.hostKind === "local" ? undefined : (session.peer ?? session.host);
 
-/** The one cloud machine every session in a group runs on, else undefined. */
-function sharedCloudHost(sessions: AcpmuxSessionEntry[]) {
-  const host = cloudHost(sessions[0]!);
-  return host && sessions.every((session) => cloudHost(session) === host) ? host : undefined;
-}
-
 /** Where a row says it runs, beyond its project: a cloud machine, then a worktree, then a branch. */
 export type SessionPlace =
   | {
@@ -427,55 +355,6 @@ export function sessionPlace(session: AcpmuxSessionEntry, groupHost?: string): S
   return undefined;
 }
 
-/** Sessions whose title, name, folder, branch, worktree or cloud machine contains every word of the query, ignoring case. */
-export function filterSessions(sessions: AcpmuxSessionEntry[], query: string): AcpmuxSessionEntry[] {
-  const terms = query.toLowerCase().split(/\s+/).filter(Boolean);
-  if (terms.length === 0) return sessions;
-  return sessions.filter((session) => terms.every((term) => sessionSearchText(session).includes(term)));
-}
-
-/** The list's two sections: pinned sessions, newest first, then every other session grouped by project. A query narrows both. Archived sessions and side chats are in neither. */
-export function sidebarSections(
-  all: AcpmuxSessionEntry[],
-  query = "",
-  groupProjects = true,
-): {
-  pinned: AcpmuxSessionEntry[];
-  groups: SessionGroup[];
-  active: AcpmuxSessionEntry[];
-} {
-  const sessions = withoutChildren(all.filter(listed));
-  const pinned = byRecency(
-    filterSessions(
-      sessions.filter((session) => session.pinned),
-      query,
-    ),
-  );
-  const groups = groupProjects
-    ? groupByProject(
-        sessions.filter((session) => !session.pinned),
-        sessions,
-      )
-    : [];
-  const active = groupProjects
-    ? []
-    : byRecency(
-        filterSessions(
-          sessions.filter((session) => !session.pinned),
-          query,
-        ),
-      );
-  if (!query.trim()) return { pinned, groups, active };
-  // Projects and their headers come from every session, so a search only hides rows.
-  return {
-    pinned,
-    active,
-    groups: groups
-      .map((group) => ({ ...group, sessions: filterSessions(group.sessions, query) }))
-      .filter((group) => group.sessions.length > 0),
-  };
-}
-
 /** The row's mark, from acpmux's `indicator`: a done chat is marked only until the user opens it. */
 export function sessionMark(session: AcpmuxSessionEntry, selected: boolean): SessionMark {
   switch (session.indicator) {
@@ -493,31 +372,6 @@ export function sessionMark(session: AcpmuxSessionEntry, selected: boolean): Ses
   }
 }
 
-/** The rows a group shows: all of a short group, else its first GROUP_ROWS unless expanded or holding the selection. */
-export function visibleSessions(
-  group: SessionGroup,
-  expanded: boolean,
-  selectedId?: string,
-): { rows: AcpmuxSessionEntry[]; hidden: number } {
-  const open =
-    expanded ||
-    group.sessions.length <= GROUP_ROWS + 1 ||
-    group.sessions.slice(GROUP_ROWS).some((session) => session.sessionId === selectedId);
-  if (open) return { rows: group.sessions, hidden: 0 };
-  return { rows: group.sessions.slice(0, GROUP_ROWS), hidden: group.sessions.length - GROUP_ROWS };
-}
-
-/** A project header's mark: the most urgent of its sessions' needs-input and lost marks. */
-export function groupMark(group: SessionGroup, selectedId?: string): "input" | "error" | undefined {
-  let mark: "input" | "error" | undefined;
-  for (const session of group.sessions) {
-    const own = sessionMark(session, session.sessionId === selectedId);
-    if (own === "input") return "input";
-    if (own === "error") mark = "error";
-  }
-  return mark;
-}
-
 /** A compact age for the history list: `now`, `5m`, `3h`, `2d`, `6w`. */
 export function shortAge(updatedAt: number | undefined, now: number, t: Translate = translate): string {
   if (updatedAt === undefined) return "";
diff --git a/webviews/src/agent-session/acpmux/styles.css b/webviews/src/agent-session/acpmux/styles.css
index 6d478f18aa27..1e801ac331d8 100644
--- a/webviews/src/agent-session/acpmux/styles.css
+++ b/webviews/src/agent-session/acpmux/styles.css
@@ -2,7 +2,7 @@
 .acpmux-stage{position:relative;flex:1;display:flex;flex-direction:column;min-height:0}.acpmux-reviewing>.acpmux-header,.acpmux-reviewing>.acpmux-scroll{visibility:hidden}
 
 .acpmux-diff-add{color:var(--acpmux-add)}.acpmux-diff-del{color:var(--acpmux-del)}.acpmux-diff-main{flex:1;display:flex;min-height:0}.acpmux-diff-body{flex:1;min-width:0;overflow-y:auto;overflow-x:hidden}.acpmux-diff-file{border-bottom:1px solid var(--agent-border)}.acpmux-fh-spacer{flex:1}
-.acpmux-diff-empty-edit{padding:8px 16px;color:var(--agent-muted);font-size:12px}.acpmux-main{position:relative;flex:1;min-width:0;display:flex;flex-direction:column}.acpmux-header>div{display:flex;align-items:center;min-width:0}.acpmux-sidebar-toggle{position:relative;flex:none;width:28px;height:28px;margin-right:6px;border:0;border-radius:7px;background:none;cursor:default}.acpmux-sidebar-toggle:hover{background:var(--agent-control-hover)}.acpmux-sidebar-toggle:focus-visible{outline:2px solid color-mix(in srgb,var(--agent-text) 40%,transparent);outline-offset:0}.acpmux-sidebar-toggle::before{content:"";position:absolute;left:6px;top:7px;width:13px;height:11px;border:1.5px solid var(--agent-soft);border-radius:3px}.acpmux-sidebar-toggle::after{content:"";position:absolute;left:11px;top:8px;width:1.5px;height:11.5px;background:var(--agent-soft)}.acpmux-sidebar{flex:none;display:flex;width:292px;box-sizing:border-box;overflow:hidden;border-right:0.5px solid var(--agent-border);background:var(--agent-page-bg);font-size:13px;letter-spacing:0.04px}.acpmux-shell[data-sidebar=closed] .acpmux-sidebar{display:none}@media not all and (min-width:640px){.acpmux-shell[data-sidebar=auto] .acpmux-sidebar{display:none}.acpmux-shell[data-sidebar=open] .acpmux-sidebar{position:absolute;z-index:2;inset:0 auto 0 0;width:min(332px,90%);background:color-mix(in srgb,var(--acpmux-base) var(--surface-text-min,92%),transparent);-webkit-backdrop-filter:var(--surface-blur);backdrop-filter:var(--surface-blur);box-shadow:var(--elevation-2)}.acpmux-shell[data-sidebar=open] .acpmux-sidebar-scrim{display:block;position:absolute;z-index:1;inset:0;border:0;padding:0;background:var(--cmux-scrim, rgb(0 0 0 / 12%));cursor:default}}.acpmux-sidebar-scrim{display:none}.acpmux-sidebar-group+.acpmux-sidebar-group{margin-top:10px}.acpmux-sidebar-project{display:flex;align-items:center;gap:8px;height:30px;margin-bottom:1px;padding:0 8px 0 9px;color:var(--agent-text);white-space:nowrap}.acpmux-sidebar ul{margin:0;padding:0;list-style:none}.acpmux-session-row{display:flex;align-items:center;gap:8px;width:100%;height:30px;margin-bottom:1px;padding:0 8px 0 33px;border:0;border-radius:8px;background:none;color:var(--agent-text);font:inherit;letter-spacing:inherit;text-align:left;cursor:pointer}.acpmux-session-row:hover,.acpmux-sidebar-more:hover{background:color-mix(in srgb,var(--agent-text) 5%,transparent)}.acpmux-session-row.is-selected{background:color-mix(in srgb,var(--agent-accent,var(--agent-text)) 9%,transparent)}.acpmux-sidebar-more:focus-visible{outline:2px solid var(--agent-accent);outline-offset:-2px}.acpmux-session-row.is-closed{color:var(--agent-muted)}.acpmux-session-row-title{flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.acpmux-session-place{flex:none;display:inline-flex;color:var(--agent-muted);opacity:.75}.acpmux-session-place-branch{opacity:.5}.acpmux-session-row:hover .acpmux-session-place,.acpmux-session-row.is-selected .acpmux-session-place{opacity:1}.acpmux-session-mark{flex:none;display:inline-flex;align-items:center;justify-content:center;width:16px;height:16px;color:var(--agent-muted)}.acpmux-session-mark-input{color:var(--agent-warning,var(--agent-accent))}.acpmux-session-mark-labeled{width:auto;gap:4px;font-size:var(--text-detail);font-weight:var(--weight-emphasis);white-space:nowrap}.acpmux-session-mark-unread::before{content:"";width:7px;height:7px;border-radius:50%;background:var(--agent-accent)}.acpmux-session-mark-running{color:var(--agent-accent)}.acpmux-sidebar-more{display:block;width:100%;height:30px;margin-bottom:1px;padding:0 8px 0 33px;border:0;border-radius:8px;background:none;color:var(--agent-muted);font:inherit;letter-spacing:inherit;text-align:left;cursor:pointer}.acpmux-sidebar-section{height:30px;padding-left:8px;line-height:30px;color:var(--agent-muted);font-weight:500}.acpmux-sidebar-pinned .acpmux-session-row{padding-left:9px}.acpmux-sidebar-pinned+.acpmux-sidebar-projects{margin-top:12px}.acpmux-sidebar-host{flex:none;max-width:45%;overflow:hidden;text-overflow:ellipsis;color:var(--agent-muted);font-size:12px}.acpmux-sidebar-search{display:flex;align-items:center;gap:8px;height:30px;margin:0 0 10px;padding:0 8px 0 9px;border-radius:8px;background:color-mix(in srgb,var(--agent-text) 5%,transparent);color:var(--agent-muted)}.acpmux-sidebar-search:focus-within{box-shadow:inset 0 0 0 1px color-mix(in srgb,var(--agent-accent) 55%,transparent)}.acpmux-sidebar-search>label{display:contents}.acpmux-sidebar-search svg{flex:none}.acpmux-sidebar-search input{flex:1;min-width:0;height:100%;padding:0;border:0;outline:none;background:none;color:var(--agent-text);font:inherit;letter-spacing:inherit;-webkit-appearance:none;appearance:none}.acpmux-sidebar-search input::placeholder{color:var(--agent-muted)}.acpmux-sidebar-search input::-webkit-search-cancel-button{-webkit-appearance:none;appearance:none}.acpmux-sidebar-empty:empty{padding:0}.acpmux-sidebar-empty{padding:6px 9px;color:var(--agent-muted)}
+.acpmux-diff-empty-edit{padding:8px 16px;color:var(--agent-muted);font-size:12px}.acpmux-main{position:relative;flex:1;min-width:0;display:flex;flex-direction:column}.acpmux-header>div{display:flex;align-items:center;min-width:0}.acpmux-session-mark{flex:none;display:inline-flex;align-items:center;justify-content:center;width:16px;height:16px;color:var(--agent-muted)}.acpmux-session-mark-input{color:var(--agent-warning,var(--agent-accent))}.acpmux-session-mark-unread::before{content:"";width:7px;height:7px;border-radius:50%;background:var(--agent-accent)}.acpmux-session-mark-running{color:var(--agent-accent)}
 /* Composer (Composer.tsx, ComposerPickers.tsx), with metrics and font from the
    reference prototype (src/shell Composer): the prompt over a bar with +,
    the mode and model chips, and a round Send. Every color derives from the theme bridge: each surface is the page
@@ -250,8 +250,7 @@
 .acpmux-queue-paused>span{grid-column:1/3}
 .acpmux-queue-resume{grid-column:3;justify-self:end;height:22px;padding:0 8px;border:0;border-radius:6px;background:none;color:var(--agent-text);font:inherit;cursor:default}
 .acpmux-queue-resume:hover{background:var(--agent-control-hover)}
-.acpmux-queue-resume:focus-visible{outline:1.5px solid var(--agent-text);outline-offset:-1px}
-.acpmux-sidebar-project>svg{flex:none;color:var(--agent-muted)}.acpmux-sidebar-project>span:not(.acpmux-session-mark){flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis}.acpmux-sidebar-rail{flex:0 0 48px;display:flex;flex-direction:column;align-items:center;gap:4px;padding:10px 0;box-sizing:border-box}.acpmux-rail-button{position:relative;display:grid;place-items:center;width:34px;height:34px;padding:0;border:0;border-radius:9px;background:none;color:var(--agent-muted);cursor:default}.acpmux-rail-button:hover:not(:disabled){background:color-mix(in srgb,var(--agent-text) 6%,transparent);color:var(--agent-text)}.acpmux-rail-button[aria-current=page]{background:color-mix(in srgb,var(--agent-text) 9%,transparent);color:var(--agent-text)}.acpmux-rail-button:focus-visible,.acpmux-sidebar-action:focus-visible{outline:2px solid color-mix(in srgb,var(--agent-text) 40%,transparent);outline-offset:-2px}.acpmux-rail-button:disabled{opacity:.4}.acpmux-rail-dot{position:absolute;top:6px;right:6px;width:6px;height:6px;border-radius:50%;background:var(--agent-warning,var(--agent-accent))}.acpmux-sidebar-body{flex:1;min-width:0;display:flex;flex-direction:column}.acpmux-sidebar-scroll{flex:1;min-height:0;overflow:auto;padding:10px 8px 16px 0}.acpmux-sidebar-action{display:flex;align-items:center;gap:8px;width:100%;height:30px;margin-bottom:6px;padding:0 9px;border:0;border-radius:8px;background:none;color:var(--agent-text);font:inherit;letter-spacing:inherit;cursor:default}.acpmux-sidebar-action svg{flex:none;color:var(--agent-soft)}.acpmux-sidebar-action:hover{background:color-mix(in srgb,var(--agent-text) 5%,transparent)}.acpmux-sidebar-title{display:flex;align-items:center;height:30px;margin:0 0 6px;padding:0 9px;font-size:13px;font-weight:600}.acpmux-session-row.is-flat{padding-left:9px}.acpmux-session-trailing{flex:none;color:var(--agent-muted);font-size:12px;font-variant-numeric:tabular-nums}.acpmux-account{flex:none;display:flex;align-items:center;gap:8px;height:48px;padding:0 17px 0 9px}.acpmux-avatar{flex:none;display:grid;place-items:center;width:24px;height:24px;border-radius:50%;background:color-mix(in srgb,var(--agent-text) 14%,transparent);color:var(--agent-text);font-size:12px;font-weight:600}.acpmux-account-name{min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-weight:500}.acpmux-account-detail{flex:none;color:var(--agent-muted)}.acpmux-account-detail::before{content:"· "}.acpmux-hidden-label{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap}
+.acpmux-queue-resume:focus-visible{outline:1.5px solid var(--agent-text);outline-offset:-1px}.acpmux-hidden-label{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%);white-space:nowrap}
 /* New chat (EmptyState.tsx): a centered hero, small and muted, in place of the empty transcript. */
 .acpmux-empty{flex:1;min-height:0;overflow:hidden;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:14px;padding:0 24px 6%;box-sizing:border-box;text-align:center;font-family:system-ui,-apple-system,"Helvetica Neue",sans-serif;-webkit-font-smoothing:antialiased}
 .acpmux-empty-glyph{color:var(--acpmux-composer-placeholder)}
@@ -275,7 +274,6 @@
 /* Search files: a quick-open palette, centered over the transcript's upper part (main column). */
 /* Quick open drops from the top as it opens; the narrow pane's sidebar drawer slides in from the left, its own width (ui-enter, ui/popupSurface.css). */
 .acpmux-file-search{--ui-enter-y:-8px;animation:ui-enter var(--ui-enter-duration) var(--ui-enter-ease) both}
-@media not all and (min-width:640px){.acpmux-shell[data-sidebar=open] .acpmux-sidebar{--ui-enter-x:-100%;animation:ui-enter var(--ui-enter-duration) var(--ui-enter-ease) both}}
 .acpmux-file-search{position:absolute;z-index:20;top:max(48px,18%);left:50%;right:auto;margin:0;border:0;width:min(600px,calc(100vw - 32px));transform:translateX(-50%);padding:6px;box-sizing:border-box;border-radius:14px;background:var(--surface-popup);box-shadow:inset 0 0 0 var(--cmux-hairline, .5px) var(--acpmux-composer-edge),var(--elevation-2);color:var(--agent-text);font-size:14px}
 .acpmux-file-search input{display:block;width:100%;height:34px;padding:0 10px;box-sizing:border-box;border:0;background:none;color:var(--agent-text);font:inherit;outline:none}
 .acpmux-file-search input::placeholder{color:var(--acpmux-composer-dim)}
@@ -775,18 +773,6 @@ fieldset.acpmux-question[hidden]{display:none}
 
 /* Session row previews float in the shared popup layer, so the 30px row and its gutters never
    change when a last-message card appears. */
-.acpmux-session-preview{display:grid;gap:6px;min-width:220px;max-width:300px;padding:10px 12px;color:var(--ui-popup-fg,var(--agent-text));}
-.ui-card.acpmux-session-preview{pointer-events:auto;}
-.acpmux-session-preview-title{min-width:0;overflow:hidden;color:var(--agent-text);font-size:var(--text-body);line-height:var(--text-body--line-height);font-weight:var(--weight-emphasis);text-overflow:ellipsis;white-space:nowrap;}
-.acpmux-session-preview-copy{max-width:34ch;color:var(--agent-soft);font-size:var(--text-detail);line-height:var(--text-detail--line-height);overflow-wrap:anywhere;}
-.acpmux-session-preview-meta{display:flex;flex-wrap:wrap;gap:8px;color:var(--agent-muted);font-size:var(--text-caption);line-height:var(--text-caption--line-height);}
-.acpmux-session-preview-status,.acpmux-session-preview-place{display:inline-flex;align-items:center;gap:4px;min-width:0;}
-.acpmux-session-preview-status.acpmux-session-mark-input{color:var(--agent-warning,var(--agent-accent));}
-.acpmux-session-preview-status.acpmux-session-mark-running{color:var(--agent-accent);}
-.ui-card.acpmux-session-preview-quiet{min-width:204px;max-width:270px;gap:4px;padding:8px 10px;border:0.5px solid color-mix(in srgb,currentColor 14%,transparent);background:color-mix(in srgb,var(--surface-popup) 88%,var(--agent-page-bg));box-shadow:none;}
-.acpmux-session-preview-quiet .acpmux-session-preview-title{font-size:var(--text-control);line-height:var(--text-control--line-height);}
-.acpmux-session-preview-quiet .acpmux-session-preview-copy{max-width:30ch;}
-.ui-card.acpmux-session-preview-outline{min-width:220px;max-width:300px;padding:10px 12px;border:0.5px solid color-mix(in srgb,var(--agent-accent) 34%,transparent);background:color-mix(in srgb,var(--agent-page-bg) 92%,var(--agent-text) 8%);box-shadow:none;}
 
 /* The host's all-zero motion policy is stronger than the browser preference: it is the explicit
    `ui.animationSpeed: off` setting. Stop every pane animation, including loops owned by a child
diff --git a/webviews/src/agent-session/acpmux/summary/cardState.ts b/webviews/src/agent-session/acpmux/summary/cardState.ts
index 1d8c48992f7c..ff3317cdeed1 100644
--- a/webviews/src/agent-session/acpmux/summary/cardState.ts
+++ b/webviews/src/agent-session/acpmux/summary/cardState.ts
@@ -75,9 +75,8 @@ export function useSummaryColumn(shell: HTMLElement | null, blocked: boolean): b
       return;
     }
     const measure = () => {
-      const sidebar = shell.querySelector<HTMLElement>(":scope>.acpmux-sidebar");
       const rail = shell.querySelector<HTMLElement>(":scope>.acpmux-chat-inspector");
-      const reserved = (sidebar?.offsetWidth ?? 0) + (rail?.offsetWidth ?? 0);
+      const reserved = rail?.offsetWidth ?? 0;
       const available = shell.clientWidth - reserved;
       // The summary takes 300px from the same flex row as the transcript. At a width where that
       // would erase the active mode's extra measure, keep it as a popover. The preceding mode's
diff --git a/webviews/test/chat-rows-open-on-press.test.tsx b/webviews/test/chat-rows-open-on-press.test.tsx
index 6653c1fb673f..f44b9f6e832e 100644
--- a/webviews/test/chat-rows-open-on-press.test.tsx
+++ b/webviews/test/chat-rows-open-on-press.test.tsx
@@ -89,34 +89,6 @@ const keyboardClick = (element: Element) =>
 
 const settle = () => act(async () => new Promise((resolve) => setTimeout(resolve, 0)));
 
-test("a chat row in the agent pane's sidebar opens on the press, once", async () => {
-  const { createRoot } = await import("react-dom/client");
-  const { SessionSidebar } = await import("../src/agent-session/acpmux/SessionSidebar");
-  const opened: string[] = [];
-  const session = {
-    sessionId: "session-1",
-    title: "Fix the checkout",
-    harness: "codex",
-    cwd: "/Users/you/src/cmux",
-    status: "running",
-    indicator: "working" as const,
-    host: "This Mac",
-    hostKind: "local" as const,
-    updatedAt: 1,
-  };
-  root = createRoot(host);
-  await act(async () =>
-    root!.render(<SessionSidebar sessions={[session]} onSelect={(id: string) => opened.push(id)} />),
-  );
-  const row = host.querySelector(".acpmux-session-row")!;
-  await press(row);
-  expect(opened).toEqual(["session-1"]);
-  await release(row);
-  expect(opened).toEqual(["session-1"]);
-  await keyboardClick(row);
-  expect(opened).toEqual(["session-1", "session-1"]);
-});
-
 const chats = [
   { key: "a", harness: "claude", title: "Retry uploads", cwd: "/Users/me/src/uploader", updatedAt: 9 },
   { key: "b", harness: "claude", title: "Fix the sidebar", cwd: "/Users/me/src/cmux", updatedAt: 8 },
diff --git a/webviews/test/chats-sidebar-empty.test.tsx b/webviews/test/chats-sidebar-empty.test.tsx
deleted file mode 100644
index d75578b1153a..000000000000
--- a/webviews/test/chats-sidebar-empty.test.tsx
+++ /dev/null
@@ -1,122 +0,0 @@
-// POLISH sweep: the chats sidebar's empty states say "chats", like every other chats list, and a
-// search that matches nothing says so once, not again under Settled.
-import { afterAll, beforeAll, expect, test } from "bun:test";
-import { JSDOM } from "jsdom";
-import { act } from "react";
-import type { Root } from "react-dom/client";
-import type { AcpmuxSessionEntry } from "../src/agent-session/acpmux/sessionList";
-
-const scope = globalThis as Record<string, unknown>;
-const keys = ["window", "document", "navigator", "HTMLElement", "IS_REACT_ACT_ENVIRONMENT"] as const;
-const saved = keys.map((key) => [key, key in scope, scope[key]] as const);
-let root: Root | undefined;
-let host: HTMLElement;
-
-beforeAll(() => {
-  const { window } = new JSDOM("<!doctype html><div id=root></div>");
-  Object.assign(window, {
-    ResizeObserver: class {
-      observe() {}
-      unobserve() {}
-      disconnect() {}
-    },
-  });
-  Object.assign(scope, {
-    window,
-    document: window.document,
-    navigator: window.navigator,
-    HTMLElement: window.HTMLElement,
-    IS_REACT_ACT_ENVIRONMENT: true,
-  });
-  host = window.document.getElementById("root")!;
-});
-
-afterAll(() => {
-  act(() => root?.unmount());
-  for (const [key, had, value] of saved) {
-    if (had) scope[key] = value;
-    else delete scope[key];
-  }
-});
-
-const chat = (sessionId: string, title: string): AcpmuxSessionEntry => ({
-  sessionId,
-  displayTitle: title,
-  title,
-  harness: "claude",
-  cwd: "/tmp/cmux",
-  updatedAt: 1,
-});
-
-async function sidebar(
-  sessions: ReturnType<typeof chat>[],
-  settledSessions: ReturnType<typeof chat>[],
-  groupProjects = false,
-) {
-  const { createRoot } = await import("react-dom/client");
-  const { SessionSidebar } = await import("../src/agent-session/acpmux/SessionSidebar");
-  act(() => root?.unmount());
-  root = createRoot(host);
-  await act(async () =>
-    root!.render(
-      <SessionSidebar
-        sessions={sessions}
-        settledSessions={settledSessions}
-        groupProjects={groupProjects}
-        onSelect={() => {}}
-      />,
-    ),
-  );
-}
-
-async function search(text: string) {
-  const field = host.querySelector<HTMLInputElement>('input[type="search"]')!;
-  const setter = Object.getOwnPropertyDescriptor(Object.getPrototypeOf(field), "value")!.set!;
-  await act(async () => {
-    setter.call(field, text);
-    field.dispatchEvent(new window.Event("input", { bubbles: true }));
-  });
-}
-
-test("a search that matches nothing says so once", async () => {
-  await sidebar([chat("a", "Fix the build")], [chat("b", "Polish the home screen")]);
-  await search("zzz");
-  const said = host.textContent!.split("No matching chats").length - 1;
-  expect(said).toBe(1);
-  expect(host.textContent).not.toContain("sessions");
-  expect(host.querySelector('input[type="search"]')!.getAttribute("aria-label")).toBe("Search chats");
-});
-
-// Grouped by project, the chats live in groups, not the flat Active list; they count as matches.
-test("chats grouped by project are not called no matches", async () => {
-  await sidebar([chat("a", "Fix the build"), chat("c", "Ship the docs")], [], true);
-  expect(host.textContent).toContain("Fix the build");
-  expect(host.textContent).not.toContain("No matching chats");
-  expect(host.querySelector(".acpmux-sidebar-settled")).not.toBeNull();
-  await search("docs");
-  expect(host.textContent).toContain("Ship the docs");
-  expect(host.textContent).not.toContain("No matching chats");
-  await search("zzz");
-  expect(host.textContent!.split("No matching chats").length - 1).toBe(1);
-});
-
-test("an empty sidebar says there are no chats yet", async () => {
-  await sidebar([], []);
-  expect(host.textContent).toContain("No chats yet");
-});
-
-test("the default sidebar hides archived, side, and folded child chats", async () => {
-  await sidebar(
-    [
-      chat("parent", "Parent chat"),
-      { ...chat("child", "Folded child"), spawnedBy: "parent" },
-      { ...chat("archived", "Archived chat"), archived: true },
-      { ...chat("side", "Side question"), side: true },
-    ],
-    [],
-  );
-  expect(host.textContent).toContain("Parent chat");
-  expect(host.textContent).not.toContain("Folded child");
-  expect(host.textContent).not.toContain("Archived chat");
-  expect(host.textContent).not.toContain("Side question");
-});
diff --git a/webviews/test/gallery-agent-pane-entries.test.ts b/webviews/test/gallery-agent-pane-entries.test.ts
index 409f9c66cab3..4d22ed7a5846 100644
--- a/webviews/test/gallery-agent-pane-entries.test.ts
+++ b/webviews/test/gallery-agent-pane-entries.test.ts
@@ -37,8 +37,6 @@ await requireBrowserLane("gallery-agent-pane-entries.test.ts", async () => {
     (await count(page, ".acpmux-composer")) > 0 && (await count(page, "[data-harness-notice]")) === 0;
 
   const CASES: Case[] = [
-    { entry: "session-sidebar", variant: "search-filtered", play: "steps" },
-    { entry: "session-sidebar", variant: "search-clears", play: "steps" },
     { entry: "start-folder", variant: "home-question", play: "steps" },
     { entry: "start-folder", variant: "root-refused", play: "steps" },
     { entry: "permission-panel", variant: "allowance", play: "error" },
diff --git a/webviews/test/row-focus.test.ts b/webviews/test/row-focus.test.ts
index feb1acf3012f..1f86b6b1e2e8 100644
--- a/webviews/test/row-focus.test.ts
+++ b/webviews/test/row-focus.test.ts
@@ -95,20 +95,6 @@ await requireBrowserLane("row-focus.test.ts", async () => {
           return `${computed.backgroundColor} ${computed.backgroundImage} ${computed.outlineStyle}`;
         });
 
-      test("a selected session row still changes when it takes keyboard focus, with no ring", async () => {
-        const page = await browser.newPage();
-        await page.setContent(`<!doctype html><html style="${HOST}"><head><style>${paneCss}</style></head><body>
-<div class="acpmux-shell"><button class="acpmux-session-row is-selected" data-focus-ring="row" id="session">Fix the build</button></div>
-</body></html>`);
-        const resting = await look(page, "#session");
-        await page.keyboard.press("Tab");
-        expect(await page.evaluate(() => document.activeElement?.id)).toBe("session");
-        const focused = await look(page, "#session");
-        expect(focused).not.toBe(resting);
-        expect(focused.endsWith(" none")).toBe(true);
-        await page.close();
-      });
-
       test("a checked question row still shows the keyboard highlight", async () => {
         const page = await browser.newPage();
         const row = (id: string, highlighted: boolean) =>
diff --git a/webviews/test/selected-row-accent.test.ts b/webviews/test/selected-row-accent.test.ts
index f8f3b6a25ad6..73d11a07795a 100644
--- a/webviews/test/selected-row-accent.test.ts
+++ b/webviews/test/selected-row-accent.test.ts
@@ -1,4 +1,4 @@
-// Selected rows in the agent pane (New Tab's rows and chats list, the omnibar, the session list and
+// Selected rows in the agent pane (New Tab's rows and chats list, the omnibar and
 // checked question rows) tint with the theme accent when `appearance.accent` sets one. With the
 // default neutral accent the host sends the text color as `--agent-accent`, so the tint is the
 // same as before. The row text stays the text color either way.
@@ -39,7 +39,6 @@ await requireBrowserLane("selected-row-accent.test.ts", async () => {
     ["New Tab row", `<div class="nt-row is-selected">Fix the build</div>`],
     ["New Tab chats row", `<div class="nt-all-row" data-selected>Fix the build</div>`],
     ["omnibar row", `<div class="acpmux-omni-row is-selected">Fix the build</div>`],
-    ["session row", `<div class="acpmux-session-row is-selected">Fix the build</div>`],
     [
       "checked question mark",
       `<div class="acpmux-question-row" aria-checked="true"><span class="acpmux-question-mark" data-multi data-chosen></span></div>`,
diff --git a/webviews/test/session-list-grouping.test.ts b/webviews/test/session-list-grouping.test.ts
deleted file mode 100644
index 2501248c1fab..000000000000
--- a/webviews/test/session-list-grouping.test.ts
+++ /dev/null
@@ -1,33 +0,0 @@
-import { expect, test } from "bun:test";
-import { sidebarSections } from "../src/agent-session/acpmux/sessionList";
-
-const session = (id: string, cwd: string) => ({
-  sessionId: id,
-  displayTitle: id,
-  cwd,
-  updatedAt: 1,
-});
-
-test("ungrouped sidebar sections skip project grouping", () => {
-  const sessions = [session("a", "/tmp/one"), session("b", "/tmp/two")];
-  expect(sidebarSections(sessions, "", false)).toMatchObject({ pinned: [], groups: [], active: sessions });
-  expect(sidebarSections(sessions, "", true).groups).toHaveLength(2);
-});
-
-test("ungrouped sidebar sections keep archived, side, and folded chats out", () => {
-  const parent = session("parent", "/tmp/one");
-  const child = { ...session("child", "/tmp/one"), spawnedBy: "parent" };
-  const archived = { ...session("archived", "/tmp/one"), archived: true };
-  const side = { ...session("side", "/tmp/one"), side: true };
-  expect(sidebarSections([parent, child, archived, side], "", false).active.map((entry) => entry.sessionId)).toEqual([
-    "parent",
-  ]);
-});
-
-test("session search refreshes when an immutable snapshot is replaced", () => {
-  const first = session("one", "/tmp/one");
-  expect(sidebarSections([first], "one", false).active).toHaveLength(1);
-  const replacement = { ...first, displayTitle: "two", cwd: "/tmp/two" };
-  expect(sidebarSections([replacement], "one", false).active).toHaveLength(0);
-  expect(sidebarSections([replacement], "two", false).active).toHaveLength(1);
-});
diff --git a/webviews/test/session-sidebar-preview.test.tsx b/webviews/test/session-sidebar-preview.test.tsx
deleted file mode 100644
index 170aa510ad24..000000000000
--- a/webviews/test/session-sidebar-preview.test.tsx
+++ /dev/null
@@ -1,255 +0,0 @@
-// Session rows keep their 30px geometry while a latest-reply preview floats in the shared popup
-// layer. The same card is available to pointer hover and keyboard focus, and missing previews stay
-// absent.
-import { afterAll, afterEach, beforeAll, expect, test } from "bun:test";
-import { JSDOM } from "jsdom";
-import { act } from "react";
-import type { Root } from "react-dom/client";
-import { HOVER_INTENT } from "../src/ui/hoverIntent";
-import {
-  configureNativeSidebarPreviewVariant,
-  configureSidebarPreviewVariant,
-  type SidebarPreviewVariant,
-} from "../src/agent-session/acpmux/sidebarPreview";
-
-const scope = globalThis as Record<string, unknown>;
-const saved: (readonly [string, boolean, unknown])[] = [];
-let dom: JSDOM;
-let root: Root | undefined;
-let host: HTMLElement;
-
-beforeAll(() => {
-  dom = new JSDOM("<!doctype html><div id=root></div>", { url: "http://localhost/", pretendToBeVisual: true });
-  const { window } = dom;
-  Object.assign(window, {
-    ResizeObserver: class {
-      observe() {}
-      unobserve() {}
-      disconnect() {}
-    },
-  });
-  const replacements: Record<string, unknown> = {
-    window,
-    document: window.document,
-    navigator: window.navigator,
-    HTMLElement: window.HTMLElement,
-    Element: window.Element,
-    Node: window.Node,
-    MutationObserver: window.MutationObserver,
-    ResizeObserver: window.ResizeObserver,
-    getComputedStyle: window.getComputedStyle.bind(window),
-    requestAnimationFrame: window.requestAnimationFrame.bind(window),
-    cancelAnimationFrame: window.cancelAnimationFrame.bind(window),
-    IS_REACT_ACT_ENVIRONMENT: true,
-  };
-  for (const key of Object.getOwnPropertyNames(window))
-    if (
-      /^(HTML|SVG|CSS|Shadow|Document|Mutation|KeyboardEvent|PointerEvent|MouseEvent|FocusEvent)/.test(key) &&
-      !(key in scope)
-    )
-      replacements[key] = (window as unknown as Record<string, unknown>)[key];
-  saved.push(...Object.keys(replacements).map((key) => [key, key in scope, scope[key]] as const));
-  Object.assign(scope, replacements);
-  host = window.document.getElementById("root")!;
-});
-
-afterEach(() => {
-  act(() => root?.unmount());
-  root = undefined;
-});
-
-afterAll(() => {
-  dom.window.close();
-  for (const [key, had, value] of saved) {
-    if (had) scope[key] = value;
-    else delete scope[key];
-  }
-});
-
-const chat = (sessionId: string, preview?: string) => ({
-  sessionId,
-  title: "Fix the checkout",
-  harness: "codex",
-  cwd: "/Users/you/src/cmux",
-  branch: "feat/checkout",
-  status: "running",
-  indicator: "working" as const,
-  host: "This Mac",
-  hostKind: "local" as const,
-  preview,
-  updatedAt: 1,
-});
-
-async function sidebar(
-  preview?: string,
-  enabled = true,
-  count = 1,
-  onSelect = (_id: string) => {},
-  previewVariant?: SidebarPreviewVariant,
-) {
-  const { createRoot } = await import("react-dom/client");
-  const { SessionSidebar } = await import("../src/agent-session/acpmux/SessionSidebar");
-  root ??= createRoot(host);
-  const sessions = Array.from({ length: count }, (_, index) => chat(`session-${index}`, preview));
-  await act(async () =>
-    root!.render(
-      <SessionSidebar sessions={sessions} preview={enabled} previewVariant={previewVariant} onSelect={onSelect} />,
-    ),
-  );
-  return host.querySelector<HTMLElement>(".acpmux-session-row")!;
-}
-
-const wait = (ms: number) => act(async () => void (await new Promise((resolve) => setTimeout(resolve, ms))));
-
-test("session preview appears after hover and includes status and placement", async () => {
-  const row = await sidebar("The payment form needs a final pass.");
-  await act(async () => {
-    row.dispatchEvent(new window.MouseEvent("pointerover", { bubbles: true }));
-  });
-  await wait(1_050);
-  const card = document.querySelector<HTMLElement>(".acpmux-session-preview");
-  expect(card?.textContent).toContain("The payment form needs a final pass.");
-  expect(card?.textContent).toContain("Working");
-  expect(card?.textContent).toContain("Branch feat/checkout");
-  await act(async () => {
-    row.dispatchEvent(new window.MouseEvent("pointerout", { bubbles: true, relatedTarget: document.body }));
-  });
-  await wait(HOVER_INTENT.cardGrace + 50);
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-});
-
-test("session preview appears immediately on focus and stays absent without preview text", async () => {
-  const row = await sidebar("A focused latest reply.");
-  await act(async () => row.focus());
-  expect(document.querySelector<HTMLElement>(".acpmux-session-preview")?.textContent).toContain(
-    "A focused latest reply.",
-  );
-  const descriptionId = row.getAttribute("aria-describedby");
-  expect(descriptionId !== null).toBe(true);
-  expect(document.getElementById(descriptionId!)?.textContent).toContain("A focused latest reply.");
-
-  await sidebar("An updated latest reply.");
-  expect(row.getAttribute("aria-describedby")).toBe(descriptionId);
-  expect(document.getElementById(descriptionId!)?.textContent).toContain("An updated latest reply.");
-
-  await sidebar();
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-  expect(row.getAttribute("aria-describedby")).toBeNull();
-});
-
-test("the preview remains readable while the pointer crosses from its row into the card", async () => {
-  const row = await sidebar("A reply that remains readable inside its hover card.");
-  await act(async () => row.dispatchEvent(new window.MouseEvent("pointerover", { bubbles: true })));
-  await wait(HOVER_INTENT.cardDwell + 50);
-  const card = document.querySelector<HTMLElement>(".acpmux-session-preview")!;
-  expect(card !== null).toBe(true);
-
-  await act(async () => row.dispatchEvent(new window.MouseEvent("pointerout", { bubbles: true, relatedTarget: card })));
-  expect(document.querySelector(".acpmux-session-preview") !== null).toBe(true);
-  await act(async () =>
-    card.dispatchEvent(new window.MouseEvent("pointerover", { bubbles: true, relatedTarget: row })),
-  );
-  await wait(HOVER_INTENT.cardGrace + 50);
-  expect(document.querySelector(".acpmux-session-preview")?.textContent).toContain(
-    "A reply that remains readable inside its hover card.",
-  );
-  await act(async () =>
-    card.dispatchEvent(new window.MouseEvent("pointerout", { bubbles: true, relatedTarget: document.body })),
-  );
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-});
-
-test("turning preview features off removes the focused card and prevents hover cards", async () => {
-  const row = await sidebar("A reply behind the preview setting.");
-  await act(async () => row.focus());
-  expect(document.querySelector(".acpmux-session-preview")?.textContent).toContain(
-    "A reply behind the preview setting.",
-  );
-
-  const disabledRow = await sidebar("A reply behind the preview setting.", false);
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-  expect(disabledRow.getAttribute("aria-describedby")).toBeNull();
-  await act(async () => {
-    disabledRow.blur();
-    disabledRow.dispatchEvent(new window.MouseEvent("pointerover", { bubbles: true }));
-  });
-  await wait(1_050);
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-  await act(async () => disabledRow.focus());
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-});
-
-test("Escape dismisses the focused preview", async () => {
-  const row = await sidebar("A reply that can be dismissed.");
-  await act(async () => row.focus());
-  expect(document.querySelector(".acpmux-session-preview") !== null).toBe(true);
-  await act(async () => row.dispatchEvent(new window.KeyboardEvent("keydown", { key: "Escape", bubbles: true })));
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-  expect(row.getAttribute("aria-describedby")).toBeNull();
-});
-
-test("sidebar preview visual variants stay opt-in and preserve the shared card semantics", async () => {
-  const quietRow = await sidebar("A quieter preview treatment.", true, 1, undefined, "quiet");
-  await act(async () => quietRow.focus());
-  const quiet = document.querySelector<HTMLElement>(".acpmux-session-preview");
-  expect(quiet?.classList.contains("acpmux-session-preview-quiet")).toBe(true);
-  expect(quiet?.textContent).toContain("A quieter preview treatment.");
-
-  const outlineRow = await sidebar("An outlined preview treatment.", true, 1, undefined, "outline");
-  await act(async () => outlineRow.focus());
-  const outline = document.querySelector<HTMLElement>(".acpmux-session-preview");
-  expect(outline?.classList.contains("acpmux-session-preview-outline")).toBe(true);
-  expect(outline?.classList.contains("acpmux-session-preview-quiet")).toBe(false);
-
-  const defaultRow = await sidebar("The default card treatment.");
-  await act(async () => defaultRow.focus());
-  const card = document.querySelector<HTMLElement>(".acpmux-session-preview");
-  expect(card?.classList.contains("acpmux-session-preview-card")).toBe(true);
-});
-
-test("the sidebar preview Debug layout choice selects the default treatment without bypassing the preview gate", async () => {
-  await act(async () => configureSidebarPreviewVariant("quiet"));
-  const quietRow = await sidebar("A layout-selected quiet preview.");
-  await act(async () => quietRow.focus());
-  expect(document.querySelector(".acpmux-session-preview-quiet") !== null).toBe(true);
-
-  await act(async () => configureSidebarPreviewVariant("outline"));
-  const outlineRow = await sidebar("A layout-selected outline preview.");
-  await act(async () => outlineRow.focus());
-  expect(document.querySelector(".acpmux-session-preview-outline") !== null).toBe(true);
-
-  await act(async () => configureSidebarPreviewVariant("card"));
-  const disabledRow = await sidebar("Preview stays gated.", false);
-  await act(async () => disabledRow.focus());
-  expect(document.querySelector(".acpmux-session-preview") === null).toBe(true);
-});
-
-test("removing the Debug layout choice restores the native sidebar preview baseline", async () => {
-  await act(async () => configureNativeSidebarPreviewVariant("quiet"));
-  await act(async () => configureSidebarPreviewVariant("outline"));
-  await act(async () => configureSidebarPreviewVariant(undefined));
-
-  const row = await sidebar("The native quiet baseline is restored.");
-  await act(async () => row.focus());
-  expect(document.querySelector(".acpmux-session-preview-quiet") !== null).toBe(true);
-
-  await act(async () => configureNativeSidebarPreviewVariant("card"));
-  await act(async () => configureSidebarPreviewVariant(undefined));
-});
-
-test("session rows retain ArrowDown, End and Home navigation", async () => {
-  const selected: string[] = [];
-  const row = await sidebar(undefined, true, 3, (id) => selected.push(id));
-  await act(async () => row.focus());
-  for (const [key, expected] of [
-    ["ArrowDown", "session-1"],
-    ["End", "session-2"],
-    ["Home", "session-0"],
-  ]) {
-    await act(async () =>
-      document.activeElement?.dispatchEvent(new window.KeyboardEvent("keydown", { key, bubbles: true })),
-    );
-    expect(document.activeElement?.getAttribute("data-session-id")).toBe(expected);
-  }
-  expect(selected).toEqual(["session-1", "session-2", "session-0"]);
-});
diff --git a/webviews/test/sidebar-rail-css.test.tsx b/webviews/test/sidebar-rail-css.test.tsx
deleted file mode 100644
index 18c5049e763d..000000000000
--- a/webviews/test/sidebar-rail-css.test.tsx
+++ /dev/null
@@ -1,31 +0,0 @@
-// The sidebar's icon rail and the chat's session rail are two components; the pane loads both
-// sheets, so the session rail's 240-340px column (summary.css) must not land on the 48px icon rail.
-import { expect, test } from "bun:test";
-import { readFileSync } from "node:fs";
-import { Window } from "happy-dom";
-import { renderToStaticMarkup } from "react-dom/server";
-import { SessionSidebar } from "../src/agent-session/acpmux/SessionSidebar";
-
-const sheet = (path: string) => readFileSync(new URL(path, import.meta.url), "utf8");
-
-test("the sidebar's icon rail keeps its own layout with the session rail's sheet loaded", () => {
-  const markup = renderToStaticMarkup(<SessionSidebar sessions={[]} onSelect={() => {}} />);
-  const window = new Window({ width: 900, height: 600 });
-  const { document } = window;
-  for (const css of [
-    sheet("../src/agent-session/acpmux/styles.css"),
-    sheet("../src/agent-session/acpmux/summary/summary.css"),
-  ]) {
-    const style = document.createElement("style");
-    style.textContent = css;
-    document.head.append(style);
-  }
-  document.body.innerHTML = markup;
-  const rail = document.querySelector("nav.acpmux-sidebar > div")!;
-  expect(rail.querySelector("button")).not.toBeNull();
-  const computed = window.getComputedStyle(rail);
-  // happy-dom drops the session rail's clamp() basis, so check the plain values both rules set.
-  expect([computed.alignItems, computed.paddingLeft]).toEqual(["center", "0px"]);
-  expect(computed.overflowY).not.toBe("auto");
-  void window.happyDOM.close();
-});
diff --git a/webviews/test/subtle-elevation.test.ts b/webviews/test/subtle-elevation.test.ts
index ff8beaf6bbfe..da2b611728d7 100644
--- a/webviews/test/subtle-elevation.test.ts
+++ b/webviews/test/subtle-elevation.test.ts
@@ -243,7 +243,6 @@ describe("one subtle elevation scale", () => {
     ["agent-session/acpmux/styles.css", ".acpmux-newtab-kind.is-selected", "--elevation-1"],
     ["agent-session/acpmux/styles.css", ".acpmux-menu", "--elevation-2"],
     ["agent-session/acpmux/styles.css", ".acpmux-file-search", "--elevation-2"],
-    ["agent-session/acpmux/styles.css", ".acpmux-shell[data-sidebar=open] .acpmux-sidebar", "--elevation-2"],
     // Every find bar (Find in Chat, Find in Diff) is the shared find pill.
     ["ui/findPill.css", ".find-pill", "--elevation-2"],
     ["agent-session/acpmux/conversation/conversation.css", ".acpmux-jump-latest", "--elevation-2"],
diff --git a/webviews/test/ui-rules.pending.json b/webviews/test/ui-rules.pending.json
index 5be3218072e6..5a8cd50a1532 100644
--- a/webviews/test/ui-rules.pending.json
+++ b/webviews/test/ui-rules.pending.json
@@ -24,7 +24,6 @@
   "agent-session/acpmux/PermissionCard.tsx": 1,
   "agent-session/acpmux/ProjectChooser.tsx": 5,
   "agent-session/acpmux/prototype/WorkspaceShell.tsx": 5,
-  "agent-session/acpmux/SessionSidebar.tsx": 1,
   "agent-session/acpmux/summary/usePopover.ts": 1,
   "App.tsx": 1,
   "BranchBasePicker.tsx": 6,