Fix split terminal tab focus target (#6375)

Co-authored-by: Orca <help@stably.ai>

src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.focus.test.ts

@@ -133,6 +133,7 @@ function resetStore(): void {
     reconcileWorktreeTabModel: vi.fn(() => ({ renderableTabCount: 0 })),
     settings: { activeRuntimeEnvironmentId: null },
     tabsByWorktree: { 'wt-1': [terminalTab] },
+    terminalLayoutsByTabId: {},
     unifiedTabsByWorktree: { 'wt-1': [unifiedTab] },
     activateTab: mocks.activateTab,
     closeBrowserTab: mocks.closeBrowserTab,
@@ -186,7 +187,35 @@ describe('useTabGroupWorkspaceModel terminal activation focus', () => {
     expect(mocks.activateTab).toHaveBeenCalledWith('unified-terminal-1')
     expect(mocks.setActiveTab).toHaveBeenCalledWith('terminal-1')
     expect(mocks.setActiveTabType).toHaveBeenCalledWith('terminal')
-    expect(mocks.focusTerminalTabSurface).toHaveBeenCalledWith('terminal-1')
+    expect(mocks.focusTerminalTabSurface).toHaveBeenCalledWith('terminal-1', null)
+  })
+
+  it('returns keyboard focus to the active split pane leaf when a terminal tab is activated', async () => {
+    storeBox.state = {
+      ...storeBox.state,
+      terminalLayoutsByTabId: {
+        'terminal-1': {
+          activeLeafId: 'right-leaf',
+          ptyIdsByLeafId: {
+            'left-leaf': 'pty-left',
+            'right-leaf': 'pty-right'
+          },
+          root: {
+            type: 'split',
+            direction: 'horizontal',
+            first: { type: 'leaf', leafId: 'left-leaf' },
+            second: { type: 'leaf', leafId: 'right-leaf' }
+          },
+          expandedLeafId: null
+        }
+      }
+    }
+    const { useTabGroupWorkspaceModel } = await import('./useTabGroupWorkspaceModel')
+    const model = useTabGroupWorkspaceModel({ groupId: 'group-1', worktreeId: 'wt-1' })
+
+    model.commands.activateTerminal('terminal-1')
+
+    expect(mocks.focusTerminalTabSurface).toHaveBeenCalledWith('terminal-1', 'right-leaf')
   })
 
   it('toggles pane expansion from the split-group tab bar collapse button', async () => {

src/renderer/src/components/tab-group/useTabGroupWorkspaceModel.ts

@@ -44,6 +44,9 @@ const EMPTY_GROUPS: readonly TabGroup[] = []
 const EMPTY_UNIFIED_TABS: readonly Tab[] = []
 const EMPTY_BROWSER_TABS: readonly BrowserTabState[] = []
 const EMPTY_TERMINAL_TABS: readonly TerminalTab[] = []
+const EMPTY_TERMINAL_LAYOUTS_BY_TAB_ID: NonNullable<
+  ReturnType<typeof useAppStore.getState>['terminalLayoutsByTabId']
+> = {}
 
 type TerminalTabItem = TerminalTab & { unifiedTabId: string }
 
@@ -67,6 +70,7 @@ export function useTabGroupWorkspaceModel({
       openFiles: state.openFiles,
       browserTabs: state.browserTabsByWorktree[worktreeId] ?? EMPTY_BROWSER_TABS,
       expandedPaneByTabId: state.expandedPaneByTabId,
+      terminalLayoutsByTabId: state.terminalLayoutsByTabId ?? EMPTY_TERMINAL_LAYOUTS_BY_TAB_ID,
       generatedTabTitlesEnabled: state.settings?.tabAutoGenerateTitle === true,
       mobileEmulatorEnabled: state.settings?.mobileEmulatorEnabled !== false
     }))
@@ -376,11 +380,21 @@ export function useTabGroupWorkspaceModel({
       }
       setActiveTab(terminalId)
       setActiveTabType('terminal')
-      // Why: clicking the tab button gives the browser focus to the tab strip
-      // after pointerdown; explicitly return it to xterm on the next frames.
-      focusTerminalTabSurface(terminalId)
+      const activeLeafId = worktreeState.terminalLayoutsByTabId[terminalId]?.activeLeafId ?? null
+      // Why: split terminal tab activation must restore xterm focus to the
+      // store-active leaf so keyboard input cannot drift to a sibling pane.
+      focusTerminalTabSurface(terminalId, activeLeafId)
     },
-    [activateTab, focusGroup, groupId, groupTabs, setActiveTab, setActiveTabType, worktreeId]
+    [
+      activateTab,
+      focusGroup,
+      groupId,
+      groupTabs,
+      setActiveTab,
+      setActiveTabType,
+      worktreeState.terminalLayoutsByTabId,
+      worktreeId
+    ]
   )
 
   const toggleTerminalPaneExpand = useCallback(