fix(web): preserve subagent navigation and fork grouping

packages/client/ui-conversation/src/client/skeleton/ConversationSession.tsx

@@ -17,6 +17,7 @@ function deriveAncestry(list: SessionListState, id: SessionId): readonly Session
     const summary: SessionSummary | undefined = list.byId[cursor]
     if (summary === undefined || chain.includes(summary)) break
     chain.unshift(summary)
+    if (summary.origin !== 'subagent') break
     cursor = summary.parentId
   }
   return chain
@@ -24,7 +25,7 @@ function deriveAncestry(list: SessionListState, id: SessionId): readonly Session
 
 export function ConversationSession({
   sessionId, useSession, useSessions, useInput, inputActions, useStore, actions,
-  renderSlot, views, bindDraftMirror, open, wrapActiveBody, t
+  renderSlot, views, bindDraftMirror, open, wrapActiveBody, t,
 }: ConversationSessionProps) {
   useSyncExternalStore(views.subscribe, views.version)
   const tabs = views.list()

packages/client/ui-conversation/tests/skeleton.spec.tsx

@@ -87,6 +87,8 @@ function mount(
     summaryBlank?: boolean
     /** Drop the session's summary row entirely (a session the list has not caught up with). */
     omitSummaryRow?: boolean
+    /** Classify the selected child as a subagent instead of an ordinary fork. */
+    summaryOrigin?: 'subagent'
   } = {},
 ) {
   const root = sid('root')
@@ -94,6 +96,7 @@ function mount(
   const childRow = {
     id: SID, displayTitle: 'Child', parentId: root, cwd: '/projects/one',
     running: false, waitingApproval: false, blank: options.summaryBlank ?? false, updatedAt: 2,
+    ...(options.summaryOrigin === undefined ? {} : { origin: options.summaryOrigin }),
   }
   const listed = options.omitSummaryRow !== true
   const sessions = createSnapshotStore<SessionListState>({
@@ -203,7 +206,7 @@ function mount(
   }
   const view = render(<ConversationRoot {...props} />)
   return {
-    view, chat, sink, retargetWorkspace, session, slotCalls,
+    view, chat, sink, retargetWorkspace, session, slotCalls, open,
     pickerOwner: () => pickerOwner,
     rerender: () => { view.rerender(<ConversationRoot {...props} />) },
   }
@@ -218,10 +221,18 @@ describe('ConversationRoot resident composer', () => {
     expect(b.chat.store.getSnapshot().draft).toBe('ordinary revised')
     fireEvent.keyDown(box, { key: 'Enter' })
     expect(b.sink).toHaveBeenCalledWith('ordinary revised')
-    expect(b.view.getByRole('heading', { name: 'Child', level: 1 })).toBeTruthy()
+    expect((b.view.getByRole('button', { name: 'Child' }) as HTMLButtonElement).disabled).toBe(true)
     expect(b.view.queryByText('Root')).toBeNull()
   })
 
+  it('shows hierarchy only for subagents and opens their ordinary owner', () => {
+    const b = mount(conversationSnapshot(), undefined, undefined, { summaryOrigin: 'subagent' })
+    const root = b.view.getByRole('button', { name: 'Root' })
+    expect((b.view.getByRole('button', { name: 'Child' }) as HTMLButtonElement).disabled).toBe(true)
+    fireEvent.click(root)
+    expect(b.open).toHaveBeenCalledWith(sid('root'))
+  })
+
   it('active phase: fixed header outside the scrollport; sticky composer seat inside it', () => {
     const b = mount(conversationSnapshot())
     const host = b.view.container.querySelector('[data-conversation-scroll]')