feat(ui-workspace): flatten session fork rows

2026-07-30 20:29:29 +08:00
parent 7d27c92851
commit 2f8f47e500
13 changed files with 110 additions and 348 deletions
--- a/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.i18n.yaml
+++ b/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.i18n.yaml
@@ -1,6 +1,6 @@
 # Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
-#   pnpm run verify-translation-pairing --write
-2026-07-25-session-list-browsing-and-manual-order.md: 586995bf459aeaee88672863977f7acf2a7061a3
-2026-07-25-session-list-browsing-and-manual-order.zh.md: 432d5167a57d30bc04a0b4faf213e4341f07bd2f
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.md
+2026-07-25-session-list-browsing-and-manual-order.md: 831aa53e532a75392690c330837482bb0f9c32b1
+2026-07-25-session-list-browsing-and-manual-order.zh.md: 9ad074d59c13585aa4fca46ae4d40e2deb15cde6
--- a/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.md
+++ b/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.md
@@ -12,14 +12,14 @@ Two existing mechanisms stood in the way. First, the host durably promoted the a

 ## Decision

-### Flat view and viewing state
+### Flat rows and viewing state

-The group-by menu offers two modes, WorkSpace / In one list. Flat mode renders every session (fork children included) as a top-level row, strictly newest-first by `updatedAt`, with no parent/child adjacency; the Intent placeholder renders as the first row. The mode choice persists in the browser (`dsh.workspace.view`) across reloads.
+The group-by menu offers two modes, WorkSpace / In one list. WorkSpace mode renders peer session rows within each group in the manual order from `WorkspaceView.sessionIds`; In one list combines every session and sorts them strictly newest-first by `updatedAt`. Neither mode projects `parentId` into a list hierarchy; fork lineage remains session data only. [Web session fork actions](2026-07-27-web-session-fork-actions.md) define the complete fork behavior. The mode choice persists in the browser (`dsh.workspace.view`) across reloads.

 ### Row interactions

 - Session rows show a detail card after a 500ms hover dwell (full title / relative time / status line; the status line has only running/idle until the wire grows a status field). The card and the row menu are mutually exclusive: no card while a menu is open or a drag is in flight.
- Session-row … menu: Rename / Fork session / Delete session, visual-only this iteration; workspace-header … menu: Rename (wired) / Delete workspace (visual-only). Menus close when the pointer leaves them.
+- Session-row … menu: Rename / Fork session / Delete session; Rename and Fork are wired, while Delete remains visual-only. The workspace-header … menu's Rename / Delete workspace actions are both wired. Menus close when the pointer leaves them.
 - Supporting primitives: `Menu` gains label entries, danger rows, and `closeOnPointerLeave`; a new `HoverCard` (portaled placement, open delay, disabled guard).

 ### workspace.rename
@@ -30,7 +30,7 @@ The group-by menu offers two modes, WorkSpace / In one list. Flat mode renders e

 The `session/event` → `touchSession` activity-pinning chain is deleted wholesale; the workspace account order is now manually owned — new sessions prepend at attach, and explicit reordering goes through `workspace.insertSessionBefore({ workspaceId, sessionId, beforeSessionId? })` (DOM insertBefore semantics: with an anchor it inserts before it, omitted appends to the end). The entity throws a typed `WorkspaceMoveInvalidError` only for unaccounted session/anchor ids; the handler maps exactly that to the business code `workspace-move-invalid`, while storage failures stay internal.

-The UI is HTML5 drag on root rows inside a group (workspace grouping only, outside search; fork children ride with their parent and are not draggable). Order authority stays entirely host-side: drop only sends the RPC, the client performs zero local reordering, and the view refreshes from the response upsert and the changed frame; a failed move changes nothing. The client's upsert rejects snapshots older (`updatedAt`) than the installed projection so a late unary response cannot roll back a newer frame.
+The UI is HTML5 drag on session rows inside a group (workspace grouping only, outside search; fork children and their source sessions are ordered independently). Order authority stays entirely host-side: drop only sends the RPC, the client performs zero local reordering, and the view refreshes from the response upsert and the changed frame; a failed move changes nothing. The client's upsert rejects snapshots older (`updatedAt`) than the installed projection so a late unary response cannot roll back a newer frame.

 ### Shell/region split

@@ -46,15 +46,15 @@ ui-sidebar shrinks to the column-geometry shell: brand row, fold state machine,

 **Keep the rename dialog in ui-sidebar (smallest change)** — that is the problem itself: workspace-domain dialogs scattered in a borrowed slot, with each addition (the Delete confirmation is coming) repeating the cross-package wiring. Review first considered moving only the rename modal; the ruling was to give the whole browsing region to ui-workspace and leave the shell geometry-only.

-**Keep parent/child adjacency in flat mode** — contradicts strict recency (a child newer than its parent's sibling cannot slot adjacently), and the flat view's purpose is dropping the hierarchy; flattening fully and disabling drag in flat mode (no persistence carrier) is more consistent.
+**Nest sessions by fork lineage in WorkSpace mode** — nesting makes the current child visible only while its ancestors are expanded and limits in-group manual ordering to root nodes; `parentId` is lineage data, not a list-navigation structure. Flattening all sessions into peer rows lets each row be opened, searched, and ordered independently; In one list still disables drag because it has no workspace persistence carrier.

 ## Consequences

 - Manual order is the sole authority over the workspace account: an order the user arranges is never scrambled by activity; the cost is losing float-to-top-on-activity, whose signal now rides the row status dot and time label. The `WorkspaceView.sessionIds` wire contract is reworded to the manual-order semantics.
 - The two-fact shell/region contract funnels every future workspace-domain feature (Delete confirmation, cross-group moves, Ungrouped adoption) into the single ui-workspace package; ui-sidebar no longer evolves with session-list features.
 - Flat mode supports neither reordering nor a create-in-workspace entry point (switching back to grouped view is required) — an accepted scope reduction.
- Wiring the three session-menu items and workspace Delete, and growing the wire status enum, remain future iterations.
+- Wiring session Delete and growing the wire status enum remain future iterations.

 ## Testing

-Package-level suites cover the derivations (deriveGroups/deriveFlat), row components, both apply registrations and passthroughs, host entity move semantics, and the rename/insertSessionBefore RPC implementations with their fixture stubs; the `apps/web` keyless snapshots regress the assembled application; delivery acceptance additionally runs a 12-item playwright (chromium headless) checklist (grouped default, flat switch and persistence, hover-card appearance and suppression, both menus, the full rename chain, drag persistence) and drives the real host over the wire for rename success / duplicate rejection / `workspace-move-invalid`.
+Package-level suites cover the derivations (deriveGroups/deriveFlat), peer session rows, both apply registrations and passthroughs, host entity move semantics, and the rename/insertSessionBefore RPC implementations with their fixture stubs; the `apps/web` keyless snapshots regress the assembled application and pin that a fork does not introduce session expansion controls.
--- a/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.zh.md
+++ b/.agents/notes/implemented/feature/2026-07-25-session-list-browsing-and-manual-order.zh.md
@@ -12,14 +12,14 @@ Status: implemented

 ## Decision

-### 平铺视图与浏览态
+### 平铺行与浏览态

-group-by 菜单提供 WorkSpace / In one list 两种模式。平铺模式把所有 session(含 fork 子)一律作为顶层行,严格按 `updatedAt` 新→旧排序,不保持父子相邻;Intent 占位行渲染在列表首行。模式选择持久化在浏览器(`dsh.workspace.view`),刷新保持。
+group-by 菜单提供 WorkSpace / In one list 两种模式。WorkSpace 模式按 `WorkspaceView.sessionIds` 的手动序在各组内展示同级 session 行；In one list 把所有 session 合并后严格按 `updatedAt` 新→旧排序。两种模式都不把 `parentId` 投影成列表层级，fork 谱系只保留为 session 数据；完整 fork 行为由 [Web session fork 操作](2026-07-27-web-session-fork-actions.md)定义。模式选择持久化在浏览器(`dsh.workspace.view`),刷新保持。

 ### 行交互

 - session 行悬停 500ms 出详情卡(全名/相对时间/状态行;状态本期只有 running/idle 两态,枚举扩展待 wire 增补 status 字段)。卡片与行菜单互斥:菜单开启或拖拽进行中不出卡。
- session 行 … 菜单:Rename / Fork session / Delete session,本期纯视觉;workspace 组头 … 菜单:Rename(已接线)/ Delete workspace(纯视觉)。菜单鼠标移出即关。
+- session 行 … 菜单:Rename / Fork session / Delete session，其中 Rename 与 Fork 已接线，Delete 仍为纯视觉；workspace 组头 … 菜单的 Rename / Delete workspace 均已接线。菜单鼠标移出即关。
 - 支撑件:`Menu` 新增 label 条目、danger 行、`closeOnPointerLeave`;新增 `HoverCard`(portal 定位、开启延时、disabled 守卫)。

 ### workspace.rename
@@ -30,7 +30,7 @@ group-by 菜单提供 WorkSpace / In one list 两种模式。平铺模式把所

 `session/event` → `touchSession` 活动置顶链整体删除;workspace 账本序改为纯手动拥有——新 session attach 时前插,显式重排走 `workspace.insertSessionBefore({ workspaceId, sessionId, beforeSessionId? })`(DOM insertBefore 语义:锚给了插锚前,缺省 append 到末尾)。实体只对不在账的 session/锚抛类型化的 `WorkspaceMoveInvalidError`,handler 仅把它映射为业务码 `workspace-move-invalid`,存储故障保持 internal。

-UI 为组内 root 行的 HTML5 拖拽(仅 workspace 分组、非搜索态;fork 子随父不单独拖)。顺序权威完全在 host:drop 只发 RPC,client 零本地重排,视图靠响应体 upsert 与 changed 帧刷新;失败即无事发生。client 的 upsert 拒绝比已装载投影更旧(`updatedAt`)的快照,防迟到的一元响应回滚更新的帧。
+UI 为组内 session 行的 HTML5 拖拽(仅 workspace 分组、非搜索态；fork 子与源会话一样独立排序)。顺序权威完全在 host:drop 只发 RPC,client 零本地重排,视图靠响应体 upsert 与 changed 帧刷新;失败即无事发生。client 的 upsert 拒绝比已装载投影更旧(`updatedAt`)的快照,防迟到的一元响应回滚更新的帧。

 ### 壳/区域切分

@@ -46,15 +46,15 @@ ui-sidebar 缩为列几何壳:品牌行、折叠状态机、New Session、Settin

 **rename 对话框留在 ui-sidebar(最小改动)** —— 正是问题本身:workspace 域的对话框散落在借来的坑里,每加一个(Delete 确认框将至)都重演跨包接线。评审中先议了「只挪 rename Modal」的中间态,最终裁定整个浏览区域归 ui-workspace,壳只留几何。

-**平铺模式保持父子相邻成组** —— 与「严格按时间」矛盾(子新于兄则插不进相邻位),且平铺本意就是取消层级;拉平并禁用平铺下的拖拽(无持久化载体)更一致。
+**WorkSpace 模式按 fork 谱系嵌套 session** —— 嵌套会让当前子会话依赖祖先展开态才能可见，也让组内手动序只能移动根节点；`parentId` 是 lineage 数据，不是列表导航结构。所有 session 拍平成同级行后，每行都可独立打开、搜索与排序；In one list 仍因没有 workspace 持久化载体而禁用拖拽。

 ## Consequences

 - 手动序是唯一的 workspace 账本序权威:用户排好的顺序不再被活动打乱;代价是「最近活跃浮到最上」的行为消失,活跃感知转由行内状态点与时间标签承担。`WorkspaceView.sessionIds` 的 wire 契约随之改为手动序措辞。
 - 壳/区域两事实契约把 workspace 域的后续功能(Delete 确认、跨组移动、Ungrouped 收编)全部收进 ui-workspace 单包;ui-sidebar 不再随 session 列表功能演进。
 - 平铺模式不支持排序与分组入口(建到指定 workspace 需切回分组视图),是拍板接受的范围收窄。
- session 菜单三项与 workspace Delete 的功能接线、状态枚举扩 wire,留待后续迭代。
+- session Delete 的功能接线与状态枚举扩 wire,留待后续迭代。

 ## Testing

-包级用例覆盖派生(deriveGroups/deriveFlat)、行组件、两处 apply 注册与透传、host 实体移位语义、rename/insertSessionBefore 的 RPC 实现与 fixture 桩;`apps/web` keyless snapshot 回归覆盖装配后的应用;交付验收另以 playwright(chromium headless)过 12 项清单(分组默认、平铺切换与持久化、hover 卡出现与抑制、双菜单、rename 全链、拖拽落盘),并对真 host 直打 wire 验证 rename 成功/重名拒绝/`workspace-move-invalid` 三径。
+包级用例覆盖派生(deriveGroups/deriveFlat)、同级 session 行、两处 apply 注册与透传、host 实体移位语义、rename/insertSessionBefore 的 RPC 实现与 fixture 桩；`apps/web` keyless snapshot 回归覆盖装配后的应用，并钉住 fork 后没有 session 展开控件。
--- a/packages/client/ui-workspace/README.i18n.yaml
+++ b/packages/client/ui-workspace/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/client/ui-workspace/README.md
-README.md: f0dbd3de4ac5b7934b4077b2986f5def5be329c8
-README.zh.md: b9f068c6d1709f0a01d22c3fb1cdc391764d666b
+README.md: 2a4e544250756db50b19bc101c19ac79505a3d6c
+README.zh.md: 7ae2b0e196a98d1375e9073146bb8119ea8cbe90
--- a/packages/client/ui-workspace/README.md
+++ b/packages/client/ui-workspace/README.md
@@ -6,7 +6,7 @@ Shared Workspace picker plugin. `WorkspaceBrowser` is registered into the sideba

 The picker lists real Host Workspace entities through the global `useWorkspaces` hook. Selecting a Workspace invokes the slot owner's `onPick` callback to retarget the frontend Session object. Each registration declares a **directory-flow child hole** (`single` kind: `conversation.hero.workspace.directoryFlow` / `sidebar.workspaces.directoryFlow`) that the composed picker package's client half fills with its picking interaction — the [`-native`](../../host/directory-picker-native/README.md) backend's renderless OS-chooser driver today, an in-app browsing dialog under a `-browse` composition. The flat **Open local folder...** action renders only while the surface's hole is occupied (occupancy read per menu render; an empty hole means the composition has no picking affordance — the seam's documented no-flow default). This package owns the trigger and the adoption: the occupant reports one picked path per open through the hole's owner conversation (`open`/`busy`/`onPicked`/`onCancel`/`onError`), and the owner adopts it through the object layer, selecting the committed Workspace only after its list projection has refreshed; cancellation is silent, and errors land in the retryable folder dialog whose **Choose again** reopens the flow. **Create a new workspace** retains the name dialog and disables names already present in that list, while the Host remains authoritative for concurrent or non-UI callers. The runtime Session and Workspace services own materialization. The Workspace row's Delete action opens a confirmation that states the retention boundary, blocks duplicate submission, and keeps failures open; success removes the group while its Sessions remain under Ungrouped. The Session row's Rename action opens the same browser-owned dialog pattern prefilled with the row's display title: no client-side conflict rule exists (the host normalizes and may reject with `title-invalid`, rendered in the dialog alert), and confirming an unchanged title is deliberately allowed — it pins the current automatic title against regeneration.

-The Session row's Fork action forks at the source's last completed turn and opens the child; the lineage-aware tree nests it beneath the source. A failure leaves the current selection unchanged.
+The Session row's Fork action forks at the source's last completed turn and opens the child; the source and child always appear as peer rows within a workspace group, with lineage retained only as session data. A failure leaves the current selection unchanged.

 Both target slots are declared by other plugins, so `apply` registers through declaration-aware deferral and re-registers after a declaring slot is restored.

--- a/packages/client/ui-workspace/README.zh.md
+++ b/packages/client/ui-workspace/README.zh.md
@@ -6,7 +6,7 @@

 该选择器通过全局 `useWorkspaces` hook 列出真实的 Host Workspace 实体。选择 Workspace 会调用 slot owner 的 `onPick` 回调，重新定位前端 Session 对象。每个注册各自声明一个**目录流子洞**（`single` kind：`conversation.hero.workspace.directoryFlow`／`sidebar.workspaces.directoryFlow`），由组合的选择器包 client half 填入其选取交互——今天是 [`-native`](../../host/directory-picker-native/README.md) 后端的无渲染 OS 选择器驱动，`-browse` 组合下则是应用内浏览对话框。平铺显示的 **打开本地文件夹…** 操作仅在本表层的洞被占用时渲染（每次菜单渲染读取占用状态；洞为空意味着该组合没有选目录能力——seam 文档化的无流程默认行为）。本包持有触发与接纳：占用者经洞的 owner 会话（`open`/`busy`/`onPicked`/`onCancel`/`onError`）每次打开上报一个所选路径，owner 通过对象层接纳它，并等待 Workspace 列表投影刷新后才选中已提交的 Workspace；取消操作不会显示提示，错误落入可重试的文件夹对话框，其 **重新选择** 会重新打开流程。**创建新工作区** 操作保留名称对话框，并禁用列表中已有的名称，而 Host 对并发或非 UI 调用方仍具有最终决定权。运行时 Session 与 Workspace 服务负责物化。Workspace 行内的 Delete 操作会打开确认框，说明保留边界、阻止重复提交，并在失败时保持打开；成功后，该分组会被移除，其 Session 则留在 Ungrouped 下。Session 行内的 Rename 操作打开同款浏览器持有的对话框，并以该行的显示标题预填：客户端不设名称冲突规则（host 负责规范化，可能以 `title-invalid` 拒绝，错误渲染在对话框告警区）；确认未修改的标题是有意允许的——这正是把当前自动标题钉住、不再被重新生成覆盖的手势。

-Session 行内的 Fork 操作在源会话最后一个已完成轮次处 fork 并打开子会话；感知谱系的树会将子会话嵌套在源会话下。失败不会改变当前选中项。
+Session 行内的 Fork 操作在源会话最后一个已完成轮次处 fork 并打开子会话；源会话与子会话在 workspace 组内始终作为同级行展示，谱系只保留为 session 数据。失败不会改变当前选中项。

 两个目标 slot 都由其他插件声明，因此 `apply` 通过声明感知的延迟机制完成注册，并在声明该 slot 的插件恢复后重新注册。

--- a/packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx
+++ b/packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx
@@ -104,7 +104,6 @@ function SessionTree({
  const list = useSessions(s => s)
  const current = list.current
  const [expandedProjects, setExpandedProjects] = useState<string[]>([])
-  const [expandedSessions, setExpandedSessions] = useState<string[]>([])
  // Transient drag viewing state (never store-bound; order truth stays Host-side).
  const [drag, setDrag] = useState<DragState | null>(null)
  const currentGroup = current === undefined
@@ -115,27 +114,9 @@ function SessionTree({
    if (current === undefined || currentGroup === undefined) return
    setExpandedProjects(l => (l.includes(currentGroup) ? l : [...l, currentGroup]))
  }, [current, currentGroup])
-  // The selected session must be visible: unfold its ancestor chain (fork
-  // lands the child under a possibly folded parent row).
-  const currentAncestors = useMemo(() => {
-    const chain: string[] = []
-    let cursor = current === undefined ? undefined : list.byId[current]?.parentId
-    while (cursor !== undefined && !chain.includes(cursor)) {
-      chain.push(cursor)
-      cursor = list.byId[cursor]?.parentId
-    }
-    return chain
-  }, [current, list])
-  useEffect(() => {
-    if (currentAncestors.length === 0) return
-    setExpandedSessions((l) => {
-      const missing = currentAncestors.filter(id => !l.includes(id))
-      return missing.length === 0 ? l : [...l, ...missing]
-    })
-  }, [currentAncestors])
  const groups = useMemo(
-    () => deriveGroups(list, workspaces, { expandedProjects, expandedSessions, query }),
-    [list, workspaces, expandedProjects, expandedSessions, query],
+    () => deriveGroups(list, workspaces, { expandedProjects, query }),
+    [list, workspaces, expandedProjects, query],
  )
  const now = Date.now()

@@ -146,7 +127,7 @@ function SessionTree({
          <div className={css.empty}>{query === '' ? 'No sessions yet' : 'No matches'}</div>
        )}
        {groups.map(group => (
-          // Group section: header row + expanded session subtree. The
+          // Group section: header row + expanded top-level session rows. The
          // inter-group breathing room (former flat-list batch separator)
          // is the section's own margin (WorkspaceBrowser.module.css).
          <div key={group.key} className={css.groupSection}>
@@ -170,7 +151,7 @@ function SessionTree({
                }}
            />
            {group.sessions.map((node, index) => {
-              // Draggable: real-workspace group roots outside search. The drag
+              // Draggable: real-workspace session rows outside search. The drag
              // never leaves its group — rows of other groups show no markers
              // and reject drops (visual movement confined to this section).
              const draggable = group.workspaceId !== undefined && query === ''
@@ -188,15 +169,15 @@ function SessionTree({
                drop: (half: 'before' | 'after') => {
                  /* v8 ignore next -- narrowing guard: Rows gates drop on `active`, which is false while the drag state is null. */
                  if (drag === null) return
-                  const roots = group.sessions
+                  const sessions = group.sessions
                  // Anchor = the row the insert line points at ('after' means
                  // the next root; end-of-list omits the anchor → append).
-                  const anchor = half === 'before' ? node.id : roots[index + 1]?.id
+                  const anchor = half === 'before' ? node.id : sessions[index + 1]?.id
                  setDrag(null)
                  if (anchor === drag.sessionId) return
                  // No-op when the drop lands back on the source position.
-                  const sourceIndex = roots.findIndex(r => r.id === drag.sessionId)
-                  const anchorIndex = anchor === undefined ? roots.length : roots.findIndex(r => r.id === anchor)
+                  const sourceIndex = sessions.findIndex(r => r.id === drag.sessionId)
+                  const anchorIndex = anchor === undefined ? sessions.length : sessions.findIndex(r => r.id === anchor)
                  if (sourceIndex !== -1 && (anchorIndex === sourceIndex || anchorIndex === sourceIndex + 1)) return
                  insertSessionBefore(drag.workspaceId, drag.sessionId, anchor).catch((reason: unknown) => {
                    console.warn('session reorder rejected:', reason)
@@ -208,13 +189,11 @@ function SessionTree({
                <SessionNodeItem
                  key={node.id}
                  node={node}
-                  depth={0}
                  currentId={current}
                  now={now}
                  onOpen={open}
                  onRename={onSessionRename}
                  onFork={forkSession}
-                  onToggle={(id) => { setExpandedSessions(l => toggled(l, id)) }}
                  drag={dragProps}
                />
              )
@@ -242,15 +221,11 @@ function FlatList({ useSessions, open, forkSession, onSessionRename, query }: Pi
          <SessionNodeItem
            key={node.id}
            node={node}
-            depth={0}
            currentId={list.current}
            now={now}
            onOpen={open}
            onRename={onSessionRename}
            onFork={forkSession}
-            /* v8 ignore next -- required-prop filler: flat rows render no twist, so it never fires. */
-            onToggle={() => {}}
-            flat
          />
        ))}
      </div>
--- a/packages/client/ui-workspace/src/client/rows/Rows.module.css
+++ b/packages/client/ui-workspace/src/client/rows/Rows.module.css
@@ -39,9 +39,7 @@
  height: 20px;
 }

-/* Session cell (figma): pad 8, adjacent 16px twist + status slots, then a 4px
-   gap to the title — the slots butt together, so the row gap is zeroed and
-   the title carries its own margins. */
+/* Session cell (figma): pad 8, a 16px status slot, then a 4px title gap. */
 .sessionRow {
  height: 34px;
  gap: 0;
@@ -168,7 +166,7 @@
  background: var(--dsw-alias-interactive-bg-hover);
 }

-/* Drag reorder insert line (workspace-group roots): 2px accent above or
+/* Drag reorder insert line (workspace-group session rows): 2px accent above or
   below the hovered row, drawn with box-shadow so no layout shift. */
 .sessionRow.dropBefore {
  box-shadow: 0 -2px 0 0 var(--dsw-alias-state-business-primary);
@@ -233,33 +231,9 @@
  color: var(--dsw-alias-label-primary);
 }

-/* Session expand twist occupies the leading 16px slot; keep a spacer when absent
-   so titles align across sibling rows. Duplicates the .iconButton reset instead
-   of `composes:` — the tsdown CSS-modules pipeline drops composes mappings, which
-   left the raw UA button box showing. */
-.twist {
-  flex: none;
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  width: 16px;
-  height: 20px;
-  border: none;
-  border-radius: 4px;
-  padding: 0;
-  background: transparent;
-  cursor: pointer;
-}
-
-.twist:hover {
-  color: var(--dsw-alias-label-primary);
-}
-
-/* Chevrons and tree twists ride the caption grey (#ADB2B8); the folder glyph
-   stays one step darker (tertiary, #81858C) per the cell spec. Declared last
-   to win over the composed .iconButton color. */
-.chevron,
-.twist {
+/* Chevrons ride the caption grey (#ADB2B8); the folder glyph stays one step
+   darker (tertiary, #81858C) per the cell spec. */
+.chevron {
  color: var(--dsw-alias-label-caption);
 }

--- a/packages/client/ui-workspace/src/client/rows/Rows.tsx
+++ b/packages/client/ui-workspace/src/client/rows/Rows.tsx
@@ -16,9 +16,6 @@ import type { GroupNode, SessionNode } from '../tree.ts'
 import { formatRelativeTime } from '../tree.ts'
 import css from './Rows.module.css'

-/** Indent step per tree level: one 16px slot (figma session cell). */
-const INDENT_STEP = 16
-
 const SESSION_MENU_ITEMS = [
  { id: 'rename', label: 'Rename', icon: <IconEditOutline16 /> },
  { id: 'fork', label: 'Fork session', icon: <IconBranchOutline16 /> },
@@ -135,16 +132,12 @@ export function ProjectRowItem({ group, onToggle, onCreate, actions }: {
 }

 /**
- * One session subtree: the node's own 34px row (indent by depth, expand
- * twist when it has children, running dot, relative time) plus its visible
- * children, recursively — the component tree mirrors the derived tree.
+ * One top-level 34px session row with running dot and relative time.
 * @param props.node - derived session node.
- * @param props.depth - 0 = directly under the group header.
 * @param props.currentId - selected session id (row highlight).
 * @param props.now - epoch ms for relative-time formatting.
 * @param props.onOpen - open a session by id.
- * @param props.onToggle - unfold/fold a subtree by id.
- * @returns the node's row followed by its children.
+ * @returns the session row.
 */
 /** Hover-card body: full title, relative time, and the status line (running/idle until wire status lands). */
 function SessionHoverContent({ node, now }: { node: SessionNode; now: number }) {
@@ -161,7 +154,7 @@ function SessionHoverContent({ node, now }: { node: SessionNode; now: number })
 }

 /**
- * Root-row drag wiring supplied by the group owner (workspace groups only).
+ * Session-row drag wiring supplied by the group owner (workspace groups only).
 * `drop` reports the half of the row the pointer released on: 'before'
 * inserts above this row, 'after' below it (the owner resolves the anchor).
 */
@@ -184,9 +177,8 @@ function rowHalf(e: { clientY: number; currentTarget: HTMLElement }): 'before' |
  return e.clientY < rect.top + rect.height / 2 ? 'before' : 'after'
 }

-export function SessionNodeItem({ node, depth, currentId, now, onOpen, onRename, onFork, onToggle, drag, flat = false }: {
+export function SessionNodeItem({ node, currentId, now, onOpen, onRename, onFork, drag }: {
  node: SessionNode
-  depth: number
  currentId: string | undefined
  now: number
  onOpen: (id: SessionNode['id']) => void
@@ -194,18 +186,13 @@ export function SessionNodeItem({ node, depth, currentId, now, onOpen, onRename,
  onRename: (id: SessionNode['id'], currentTitle: string) => void
  /** Fork a session at its last completed turn (row menu action). */
  onFork: (id: SessionNode['id']) => void
-  onToggle: (id: SessionNode['id']) => void
-  /** Present only on draggable rows (workspace-group roots outside search). */
+  /** Present only on draggable rows (workspace-group sessions outside search). */
  drag?: RowDragProps | undefined
-  /** Flat-list variant: no twist slot (figma flat cell) — titles align on the status slot. */
-  flat?: boolean
 }) {
  const row = node
  const selected = node.id === currentId
  const [menuOpen, setMenuOpen] = useState(false)
-  // Rail (figma session cell: pad 8, twist slot 16, status slot 16, gap 4 to
-  // the title): both slots are always reserved so titles align whether or not
-  // the twist/dot is lit. Extra depth rides the left padding.
+  // Figma session cell: pad 8, status slot 16, then a 4px title gap.
  const ownRow = (
    <div
      className={clsx(
@@ -214,8 +201,6 @@ export function SessionNodeItem({ node, depth, currentId, now, onOpen, onRename,
      )}
      role="treeitem"
      aria-selected={selected}
-      {...(row.hasChildren ? { 'aria-expanded': row.expanded } : {})}
-      style={{ paddingLeft: 8 + depth * INDENT_STEP }}
      onClick={() => { onOpen(node.id) }}
      draggable={drag !== undefined}
      onDragStart={drag === undefined
@@ -241,18 +226,6 @@ export function SessionNodeItem({ node, depth, currentId, now, onOpen, onRename,
          drag.drop(rowHalf(e))
        }}
    >
-      {row.hasChildren && !flat
-        ? (
-          <button
-            type="button"
-            className={css.twist}
-            aria-label={row.expanded ? 'Collapse' : 'Expand'}
-            onClick={(e) => { e.stopPropagation(); onToggle(node.id) }}
-          >
-            <IconTriangleRightFill14 className={clsx(css.arrow, row.expanded && css.arrowOpen)} />
-          </button>
-        )
-        : null}
      <span className={css.slot}>{row.running && <StateDot state="ongoing" />}</span>
      <span className={css.title}>{row.title}</span>
      <span className={css.time}>{formatRelativeTime(row.updatedAt, now)}</span>
@@ -283,25 +256,10 @@ export function SessionNodeItem({ node, depth, currentId, now, onOpen, onRename,
    </div>
  )
  return (
-    <>
-      <HoverCard
-        anchor={ownRow}
-        content={<SessionHoverContent node={node} now={now} />}
-        disabled={menuOpen || drag?.active === true}
-      />
-      {node.children.map(child => (
-        <SessionNodeItem
-          key={child.id}
-          node={child}
-          depth={depth + 1}
-          currentId={currentId}
-          now={now}
-          onOpen={onOpen}
-          onRename={onRename}
-          onFork={onFork}
-          onToggle={onToggle}
-        />
-      ))}
-    </>
+    <HoverCard
+      anchor={ownRow}
+      content={<SessionHoverContent node={node} now={now} />}
+      disabled={menuOpen || drag?.active === true}
+    />
  )
 }
--- a/packages/client/ui-workspace/src/client/tree.ts
+++ b/packages/client/ui-workspace/src/client/tree.ts
@@ -11,20 +11,15 @@ export const UNGROUPED_KEY = ''
 /** Display label for the ungrouped bucket row. */
 export const UNGROUPED_LABEL = 'Ungrouped'

-/** One session node of a group's visible tree (34px row; children render indented one step). */
+/** One top-level session row in a group or the flat list. */
 export interface SessionNode {
  id: SessionId
  title: string
-  /** Visible children, already expansion/search-filtered (empty when folded). */
-  children: readonly SessionNode[]
-  /** The session HAS children in the data (the twist renders even while folded). */
-  hasChildren: boolean
-  expanded: boolean
  running: boolean
  updatedAt: number
 }

-/** One workspace group section: header row facts + the visible session tree. */
+/** One workspace group section: header row facts + visible top-level session rows. */
 export interface GroupNode {
  /** Group key: the workspace id or {@link UNGROUPED_KEY}. */
  key: string
@@ -39,14 +34,13 @@ export interface GroupNode {
  expanded: boolean
  /** The group contains the selected session (active folder tint; supplied here so the renderer never scans). */
  containsCurrent: boolean
-  /** Visible roots (empty while the group is folded). */
+  /** Visible session rows (empty while the group is folded). */
  sessions: readonly SessionNode[]
 }

-/** Viewing state consumed by the derivation — the component's local useState arrays, taken as-is. */
+/** Viewing state consumed by the derivation. */
 export interface TreeView {
  expandedProjects: readonly string[]
-  expandedSessions: readonly string[]
  query: string
 }

@@ -56,9 +50,7 @@ interface Group {
  cwd: string | undefined
  createdAt: number | undefined
  label: string
-  summaries: Map<SessionId, SessionSummary>
-  roots: SessionId[]
-  children: Map<SessionId, SessionId[]>
+  sessions: SessionSummary[]
 }

 /**
@@ -89,7 +81,7 @@ function sessionTitle(session: SessionSummary): string {
  return session.blank ? 'New Session' : session.displayTitle
 }

-/** Build one group's parent/child tree from an ordered member list. */
+/** Build one group without projecting session lineage into presentation. */
 function buildGroup(
  key: string,
  workspaceId: WorkspaceId | undefined,
@@ -99,54 +91,11 @@ function buildGroup(
  members: readonly SessionSummary[],
  order: 'account' | 'recency',
 ): Group {
-  const summaries = new Map(members.map(m => [m.id, m]))
-  const children = new Map<SessionId, SessionId[]>()
-  const roots: SessionSummary[] = []
-  for (const m of members) {
-    // A session is a tree child only when its parent lives in the same
-    // group; cross-group or unknown parents degrade to group roots.
-    if (m.parentId !== undefined && m.parentId !== m.id && summaries.has(m.parentId)) {
-      const kids = children.get(m.parentId)
-      if (kids === undefined) children.set(m.parentId, [m.id])
-      else kids.push(m.id)
-    } else {
-      roots.push(m)
-    }
-  }
-  // Workspace order is the member iteration order (workspace.sessionIds), so
-  // attached groups keep insertion order; Ungrouped sorts by recency.
-  if (order === 'recency') {
-    roots.sort(byRecency)
-    for (const kids of children.values()) {
-      kids.sort((a, b) => {
-        const sa = summaries.get(a)
-        const sb = summaries.get(b)
-        /* v8 ignore next -- unreachable: kid ids are inserted alongside their summaries. */
-        if (sa === undefined || sb === undefined) return 0
-        return byRecency(sa, sb)
-      })
-    }
-  }
-  const rootIds = roots.map(r => r.id)
-  // parentId cycles (host bug) leave members unreachable from any root;
-  // surface them as extra roots — the flatten walk's visited set stops
-  // loops. Each node sits in at most one kids list and roots have no
-  // in-group parent, so the scan pushes every reachable node exactly once.
-  const reachable = new Set<SessionId>(rootIds)
-  const stack = [...rootIds]
-  while (stack.length > 0) {
-    const top = stack.pop()
-    /* v8 ignore next -- unreachable: the loop condition guarantees a non-empty stack. */
-    if (top === undefined) break
-    for (const kid of children.get(top) ?? []) {
-      reachable.add(kid)
-      stack.push(kid)
-    }
-  }
-  for (const m of members) {
-    if (!reachable.has(m.id)) rootIds.push(m.id)
-  }
-  return { key, workspaceId, cwd, createdAt, label, summaries, roots: rootIds, children }
+  const sessions = [...members]
+  // Workspace order is workspace.sessionIds; only Ungrouped lacks an account
+  // order and therefore falls back to recency.
+  if (order === 'recency') sessions.sort(byRecency)
+  return { key, workspaceId, cwd, createdAt, label, sessions }
 }

 /**
@@ -181,72 +130,24 @@ function groupByWorkspace(list: SessionListState, workspaces: readonly Workspace
  return groups
 }

-function sessionNode(s: SessionSummary, children: readonly SessionNode[], hasChildren: boolean, expanded: boolean): SessionNode {
+function sessionNode(s: SessionSummary): SessionNode {
  return {
    id: s.id,
    title: sessionTitle(s),
-    children,
-    hasChildren,
-    expanded,
    running: s.running,
    updatedAt: s.updatedAt,
  }
 }

-function buildVisible(g: Group, expandedSessions: ReadonlySet<string>): SessionNode[] {
-  const visited = new Set<SessionId>()
-  const walk = (id: SessionId): SessionNode | null => {
-    if (visited.has(id)) return null
-    visited.add(id)
-    const s = g.summaries.get(id)
-    /* v8 ignore next -- unreachable: walked ids come from the grouped summaries. */
-    if (s === undefined) return null
-    const kids = g.children.get(id) ?? []
-    const expanded = expandedSessions.has(id)
-    const children = expanded ? kids.map(walk).filter((n): n is SessionNode => n !== null) : []
-    return sessionNode(s, children, kids.length > 0, expanded)
-  }
-  return g.roots.map(walk).filter((n): n is SessionNode => n !== null)
-}
-
-/** Matched sessions plus their ancestor chains (forced visible under search). */
-function searchVisible(g: Group, q: string): Set<SessionId> {
-  const visible = new Set<SessionId>()
-  for (const m of g.summaries.values()) {
-    if (!sessionTitle(m).toLowerCase().includes(q)) continue
-    let cur: SessionSummary | undefined = m
-    while (cur !== undefined && !visible.has(cur.id)) {
-      visible.add(cur.id)
-      cur = cur.parentId !== undefined && cur.parentId !== cur.id ? g.summaries.get(cur.parentId) : undefined
-    }
-  }
-  return visible
-}
-
-function buildSearch(g: Group, visible: ReadonlySet<SessionId>): SessionNode[] {
-  const visited = new Set<SessionId>()
-  const walk = (id: SessionId): SessionNode | null => {
-    if (visited.has(id) || !visible.has(id)) return null
-    visited.add(id)
-    const s = g.summaries.get(id)
-    /* v8 ignore next -- unreachable: walked ids come from the grouped summaries. */
-    if (s === undefined) return null
-    const kids = (g.children.get(id) ?? []).filter(kid => visible.has(kid))
-    const children = kids.map(walk).filter((n): n is SessionNode => n !== null)
-    return sessionNode(s, children, kids.length > 0, kids.length > 0)
-  }
-  return g.roots.map(walk).filter((n): n is SessionNode => n !== null)
-}
-
 /**
- * Derive the nested workspace browser group structure.
+ * Derive the workspace browser groups with every session as a top-level row.
 *
 * Normal mode: every group shows; sessions populate under expanded groups,
- * descending only into expanded sessions. Search mode (non-blank query,
+ * preserving Host account order. Search mode (non-blank query,
 * case-insensitive display-title substring): expansion state is ignored —
- * matched sessions and their ancestor chains are forced visible, groups
- * without a display-title or label hit are dropped, and a label-only hit
- * keeps the bare group header. Blank sessions are excluded everywhere.
+ * matching sessions are forced visible, groups without a display-title or
+ * label hit are dropped, and a label-only hit
+ * keeps the bare group header. Non-current blank sessions are excluded.
 * @param list - sessions list snapshot (`current` feeds containsCurrent).
 * @param workspaces - real workspaces in stable Host order.
 * @param view - local expansion arrays and search query.
@@ -259,7 +160,6 @@ export function deriveGroups(
 ): GroupNode[] {
  const q = view.query.trim().toLowerCase()
  const expandedProjects = new Set(view.expandedProjects)
-  const expandedSessions = new Set(view.expandedSessions)
  const currentGroup = list.current === undefined
    ? undefined
    : (workspaces.find(w => w.sessionIds.includes(list.current as SessionId))?.workspaceId as string | undefined)
@@ -274,24 +174,24 @@ export function deriveGroups(
        cwd: g.cwd,
        createdAt: g.createdAt,
        label: g.label,
-        sessionCount: g.summaries.size,
+        sessionCount: g.sessions.length,
        expanded,
        containsCurrent: g.key === currentGroup,
-        sessions: expanded ? buildVisible(g, expandedSessions) : [],
+        sessions: expanded ? g.sessions.map(sessionNode) : [],
      })
    } else {
-      const visible = searchVisible(g, q)
-      if (visible.size === 0 && !g.label.toLowerCase().includes(q)) continue
+      const matches = g.sessions.filter(session => sessionTitle(session).toLowerCase().includes(q))
+      if (matches.length === 0 && !g.label.toLowerCase().includes(q)) continue
      groups.push({
        key: g.key,
        workspaceId: g.workspaceId,
        cwd: g.cwd,
        createdAt: g.createdAt,
        label: g.label,
-        sessionCount: g.summaries.size,
-        expanded: visible.size > 0,
+        sessionCount: g.sessions.length,
+        expanded: matches.length > 0,
        containsCurrent: g.key === currentGroup,
-        sessions: buildSearch(g, visible),
+        sessions: matches.map(sessionNode),
      })
    }
  }
@@ -301,9 +201,8 @@ export function deriveGroups(
 /**
 * Derive the flat session list ("In one list" mode): every session — fork
 * children included — as a top-level row, strictly newest-first. No grouping,
- * no parent/child adjacency; rows reuse SessionNode with children always
- * empty so the renderer stays branch-free. Search mode filters by
- * case-insensitive display-title substring.
+ * no parent/child adjacency. Search mode filters by case-insensitive
+ * display-title substring.
 * @param list - sessions list snapshot.
 * @param view - the search query (expansion state does not apply).
 * @returns flat rows in render order.
@@ -318,7 +217,7 @@ export function deriveFlat(list: SessionListState, view: Pick<TreeView, 'query'>
    rows.push(s)
  }
  rows.sort(byRecency)
-  return rows.map(s => sessionNode(s, [], false, false))
+  return rows.map(sessionNode)
 }

 /**
--- a/packages/client/ui-workspace/tests/rows.spec.tsx
+++ b/packages/client/ui-workspace/tests/rows.spec.tsx
@@ -56,46 +56,22 @@ describe('workspace browser rows', () => {
    expect(onToggle).toHaveBeenCalledOnce()
  })

-  it('renders and operates selected, running, recursive Session nodes', () => {
-    const child: SessionNode = {
-      id: sid('child'), title: 'Child', children: [], hasChildren: false,
-      expanded: false, running: false, updatedAt: 0,
-    }
-    const parent: SessionNode = {
-      id: sid('parent'), title: 'Parent', children: [child], hasChildren: true,
-      expanded: true, running: true, updatedAt: 0,
+  it('renders and opens a selected running Session row', () => {
+    const node: SessionNode = {
+      id: sid('session'), title: 'Session', running: true, updatedAt: 0,
    }
    const onOpen = vi.fn()
-    const onToggle = vi.fn()
-    const view = render(
-      <SessionNodeItem node={parent} depth={0} currentId={parent.id} now={0} onOpen={onOpen}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={onToggle} />,
+    render(
+      <SessionNodeItem node={node} currentId={node.id} now={0} onOpen={onOpen}
+        onRename={vi.fn()} onFork={vi.fn()} />,
    )

-    const parentRow = screen.getByText('Parent').closest('[role="treeitem"]')!
-    const childRow = screen.getByText('Child').closest('[role="treeitem"]')!
-    expect(parentRow.getAttribute('aria-selected')).toBe('true')
-    expect(parentRow.getAttribute('aria-expanded')).toBe('true')
-    expect(childRow.getAttribute('aria-selected')).toBe('false')
-    expect(childRow.hasAttribute('aria-expanded')).toBe(false)
-
-    fireEvent.click(screen.getByRole('button', { name: 'Collapse' }))
-    expect(onToggle).toHaveBeenCalledWith(parent.id)
-    expect(onOpen).not.toHaveBeenCalled()
-    fireEvent.click(parentRow)
-    fireEvent.click(childRow)
-    expect(onOpen.mock.calls).toEqual([[parent.id], [child.id]])
-
-    view.rerender(
-      <SessionNodeItem
-        node={{ ...parent, children: [], expanded: false, running: false }}
-        depth={1} currentId={undefined} now={0} onOpen={onOpen}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={onToggle}
-      />,
-    )
-    expect(screen.getByRole('button', { name: 'Expand' })).toBeTruthy()
-    expect(screen.getByRole('treeitem').getAttribute('aria-selected')).toBe('false')
-    expect(screen.getByRole('treeitem').style.paddingLeft).toBe('24px')
+    const row = screen.getByRole('treeitem')
+    expect(row.getAttribute('aria-selected')).toBe('true')
+    expect(row.hasAttribute('aria-expanded')).toBe(false)
+    expect(screen.queryByRole('button', { name: /Expand|Collapse/ })).toBeNull()
+    fireEvent.click(row)
+    expect(onOpen).toHaveBeenCalledWith(node.id)
  })

  it('workspace row menu opens on the ellipsis, renames, and shows the danger delete row', () => {
@@ -161,11 +137,10 @@ describe('workspace browser rows', () => {
    const onRename = vi.fn()
    const onFork = vi.fn()
    const node: SessionNode = {
-      id: sid('s1'), title: 'One', children: [], hasChildren: false,
-      expanded: false, running: false, updatedAt: 0,
+      id: sid('s1'), title: 'One', running: false, updatedAt: 0,
    }
-    render(<SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={onOpen}
-      onRename={onRename} onFork={onFork} onToggle={vi.fn()} />)
+    render(<SessionNodeItem node={node} currentId={undefined} now={0} onOpen={onOpen}
+      onRename={onRename} onFork={onFork} />)
    fireEvent.click(screen.getByRole('button', { name: 'Session actions for One' }))
    expect(onOpen).not.toHaveBeenCalled()
    expect(screen.getByRole('menuitem', { name: 'Delete session' }).className).toMatch(/danger/)
@@ -187,25 +162,14 @@ describe('workspace browser rows', () => {
    expect(screen.queryByRole('menu')).toBeNull()
  })

-  it('flat variant renders no twist even for a parent and ignores toggling', () => {
-    const node: SessionNode = {
-      id: sid('p'), title: 'Parent', children: [], hasChildren: true,
-      expanded: false, running: false, updatedAt: 0,
-    }
-    render(<SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={vi.fn()}
-      onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} flat />)
-    expect(screen.queryByRole('button', { name: 'Expand' })).toBeNull()
-  })
-
  it('shows the hover card after the dwell and suppresses it while the row menu is open', () => {
    vi.useFakeTimers()
    try {
      const node: SessionNode = {
-        id: sid('s1'), title: 'Hovered', children: [], hasChildren: false,
-        expanded: false, running: true, updatedAt: 0,
+        id: sid('s1'), title: 'Hovered', running: true, updatedAt: 0,
      }
-      render(<SessionNodeItem node={node} depth={0} currentId={undefined} now={60_000} onOpen={vi.fn()}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} />)
+      render(<SessionNodeItem node={node} currentId={undefined} now={60_000} onOpen={vi.fn()}
+        onRename={vi.fn()} onFork={vi.fn()} />)
      const wrapper = screen.getByRole('treeitem').parentElement as HTMLElement
      fireEvent.pointerEnter(wrapper)
      act(() => { vi.advanceTimersByTime(500) })
@@ -228,11 +192,10 @@ describe('workspace browser rows', () => {
    vi.useFakeTimers()
    try {
      const node: SessionNode = {
-        id: sid('s1'), title: 'Quiet', children: [], hasChildren: false,
-        expanded: false, running: false, updatedAt: 0,
+        id: sid('s1'), title: 'Quiet', running: false, updatedAt: 0,
      }
-      render(<SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={vi.fn()}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} />)
+      render(<SessionNodeItem node={node} currentId={undefined} now={0} onOpen={vi.fn()}
+        onRename={vi.fn()} onFork={vi.fn()} />)
      fireEvent.pointerEnter(screen.getByRole('treeitem').parentElement as HTMLElement)
      act(() => { vi.advanceTimersByTime(500) })
      expect(screen.getByText('Idle')).toBeTruthy()
@@ -244,13 +207,12 @@ describe('workspace browser rows', () => {

  it('draggable row wires start/end and gates hover/drop on an active same-group drag', () => {
    const node: SessionNode = {
-      id: sid('s1'), title: 'Drag me', children: [], hasChildren: false,
-      expanded: false, running: false, updatedAt: 0,
+      id: sid('s1'), title: 'Drag me', running: false, updatedAt: 0,
    }
    const inactive = dragProps()
    const { rerender } = render(
-      <SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={vi.fn()}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} drag={inactive} />,
+      <SessionNodeItem node={node} currentId={undefined} now={0} onOpen={vi.fn()}
+        onRename={vi.fn()} onFork={vi.fn()} drag={inactive} />,
    )
    const row = screen.getByRole('treeitem')
    stubRect(row)
@@ -267,8 +229,8 @@ describe('workspace browser rows', () => {

    const active = dragProps({ active: true, marker: 'before' })
    rerender(
-      <SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={vi.fn()}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} drag={active} />,
+      <SessionNodeItem node={node} currentId={undefined} now={0} onOpen={vi.fn()}
+        onRename={vi.fn()} onFork={vi.fn()} drag={active} />,
    )
    stubRect(screen.getByRole('treeitem'))
    // Top half hovers/drops 'before'; bottom half 'after' (row mid = 117).
@@ -281,8 +243,8 @@ describe('workspace browser rows', () => {

    const after = dragProps({ active: true, marker: 'after' })
    rerender(
-      <SessionNodeItem node={node} depth={0} currentId={undefined} now={0} onOpen={vi.fn()}
-        onRename={vi.fn()} onFork={vi.fn()} onToggle={vi.fn()} drag={after} />,
+      <SessionNodeItem node={node} currentId={undefined} now={0} onOpen={vi.fn()}
+        onRename={vi.fn()} onFork={vi.fn()} drag={after} />,
    )
    expect(screen.getByRole('treeitem').className).toMatch(/dropAfter/)
  })
--- a/packages/client/ui-workspace/tests/tree.spec.ts
+++ b/packages/client/ui-workspace/tests/tree.spec.ts
@@ -21,7 +21,7 @@ const workspace = (id: string, sessionIds: string[]): WorkspaceView => ({
  sessionIds: sessionIds.map(sid), createdAt: '2026-01-01T00:00:00.000Z', updatedAt: '2026-01-01T00:00:00.000Z',
 })
 const view = (expandedProjects: readonly string[] = [], query = '') => ({
-  expandedProjects, expandedSessions: [] as string[], query,
+  expandedProjects, query,
 })

 describe('deriveGroups', () => {
@@ -74,7 +74,7 @@ describe('deriveGroups', () => {
    expect(groups[0]!.sessionCount).toBe(1)
  })

-  it('builds, sorts, expands, and cycle-guards an ungrouped session tree', () => {
+  it('ignores fork lineage and sorts every ungrouped session as a top-level row', () => {
    const parent = summary('parent', 1)
    const oldChild = { ...summary('old-child', 10), parentId: parent.id }
    const newChild = { ...summary('new-child', 20), parentId: parent.id }
@@ -87,15 +87,13 @@ describe('deriveGroups', () => {
    const groups = deriveGroups(
      list(parent, oldChild, newChild, tieB, tieA, self, orphan, cycleA, cycleB),
      [],
-      { expandedProjects: [UNGROUPED_KEY], expandedSessions: [parent.id, cycleA.id, cycleB.id], query: '' },
+      { expandedProjects: [UNGROUPED_KEY], query: '' },
    )

    expect(groups).toHaveLength(1)
    expect(groups[0]!.sessions.map(node => node.id)).toEqual([
-      sid('orphan'), sid('self'), parent.id, sid('cycle-a'),
-    ])
-    expect(groups[0]!.sessions[2]!.children.map(node => node.id)).toEqual([
      newChild.id, tieA.id, tieB.id, oldChild.id,
+      cycleB.id, cycleA.id, orphan.id, self.id, parent.id,
    ])

    // Equal timestamps use ids as a deterministic tiebreak in either input order.
@@ -113,7 +111,7 @@ describe('deriveGroups', () => {
    expect(groups[0]!.sessions.map(node => node.id)).toEqual([sid('present')])
  })

-  it('searches descendants with ancestors and handles cycles, self parents, and label-only hits', () => {
+  it('searches rows independently of lineage and keeps label-only hits', () => {
    const root = { ...summary('root', 1), displayTitle: 'Ancestor' }
    const match = { ...summary('match', 2), displayTitle: 'Needle child', parentId: root.id }
    const sibling = { ...summary('sibling', 3), displayTitle: 'Other child', parentId: root.id }
@@ -124,8 +122,8 @@ describe('deriveGroups', () => {
    const sessions = list(root, match, sibling, self, orphan, cycleA, cycleB)
    const groups = deriveGroups(sessions, [workspace('project', sessions.ids)], view([], 'needle'))

-    expect(groups[0]!.sessions.flatMap(node => [node.id, ...node.children.map(child => child.id)])).toEqual([
-      root.id, match.id, self.id, orphan.id, cycleA.id, cycleB.id,
+    expect(groups[0]!.sessions.map(node => node.id)).toEqual([
+      match.id, self.id, orphan.id, cycleA.id, cycleB.id,
    ])

    const labelOnly = deriveGroups(
@@ -157,8 +155,6 @@ describe('deriveFlat', () => {
    const tieA = summary('tie-a', 20)
    const rows = deriveFlat(list(parent, child, tieB, tieA), { query: '' })
    expect(rows.map(row => row.id)).toEqual([sid('child'), sid('tie-a'), sid('tie-b'), sid('parent')])
-    // Rows are branch-free: no children, no expansion.
-    expect(rows.every(row => row.children.length === 0 && !row.hasChildren && !row.expanded)).toBe(true)
  })

  it('search filters by case-insensitive display-title substring', () => {
--- a/packages/client/ui-workspace/tests/workspace-browser.spec.tsx
+++ b/packages/client/ui-workspace/tests/workspace-browser.spec.tsx
@@ -125,7 +125,7 @@ describe('WorkspaceBrowser', () => {
    expect(screen.queryByText('alpha-s')).toBeNull()
  })

-  it('unfolds a session subtree through the row twist', () => {
+  it('renders a fork child as a top-level row without a session twist', () => {
    const parent = summary('parent-s', 2)
    const child = { ...summary('child-s', 1), parentId: parent.id }
    mount({
@@ -133,11 +133,9 @@ describe('WorkspaceBrowser', () => {
      useWorkspaces: hook(workspaceState([workspace('alpha', ['parent-s', 'child-s'])])),
    })
    fireEvent.click(screen.getByText('alpha'))
-    expect(screen.queryByText('child-s')).toBeNull()
-    fireEvent.click(screen.getByRole('button', { name: 'Expand' }))
    expect(screen.getByText('child-s')).toBeTruthy()
-    fireEvent.click(screen.getByRole('button', { name: 'Collapse' }))
-    expect(screen.queryByText('child-s')).toBeNull()
+    expect(screen.queryByRole('button', { name: /Expand|Collapse/ })).toBeNull()
+    expect(screen.getByText('child-s').closest('[role="treeitem"]')?.getAttribute('draggable')).toBe('true')
  })

  it('auto-expands the selected session group and starts a session from the group ＋', () => {