Prevent active terminal focus on dead panes and ignore stale PTY events

- Redirect active keyboard focus to a live, PTY-backed sibling pane
  if the focused pane dies, fails to spawn, or is hydrated without a
  live connection.
- Ignore stale data, replay messages, and subscription rejection errors
  from older PTY sessions after a transport has reconnected.
- Avoid persisting stale PTY bindings and dead pane focus inside
  terminal shutdown layout snapshots.

src/renderer/src/components/terminal-pane/pty-connection.test.ts

@@ -349,19 +349,29 @@ function createPane(paneId: number) {
   }
 }
 
-function createManager(paneCount = 1) {
+function createManager(paneCount = 1, initialActivePaneId: number | null = null) {
+  let activePaneId = initialActivePaneId
+  const panes = Array.from({ length: paneCount }, (_, index) => ({
+    id: index + 1,
+    leafId: leafIdForPane(index + 1)
+  }))
   return {
     setPaneGpuRendering: vi.fn(),
     markPaneHasComplexScriptOutput: vi.fn(),
     rebuildPaneWebgl: vi.fn(),
-    getPanes: vi.fn(() =>
-      Array.from({ length: paneCount }, (_, index) => ({
-        id: index + 1,
-        leafId: leafIdForPane(index + 1)
-      }))
-    ),
+    getPanes: vi.fn(() => panes),
     closePane: vi.fn(),
-    getActivePane: vi.fn<() => { id: number } | null>(() => null)
+    getActivePane: vi.fn<() => { id: number; leafId?: string } | null>(() =>
+      activePaneId === null
+        ? null
+        : (panes.find((candidate) => candidate.id === activePaneId) ?? null)
+    ),
+    getNumericIdForLeaf: vi.fn((leafId: string) => {
+      return panes.find((candidate) => candidate.leafId === leafId)?.id ?? null
+    }),
+    setActivePane: vi.fn((paneId: number) => {
+      activePaneId = paneId
+    })
   }
 }
 
@@ -851,10 +861,30 @@ describe('connectPanePty', () => {
     const { connectPanePty } = await import('./pty-connection')
     const transport = createMockTransport('pty-pane-2')
     transportFactoryQueue.push(transport)
-    const manager = createManager(2)
+    const manager = createManager(2, 2)
     const deps = createDeps({
       restoredLeafId: LEAF_2,
-      paneTransportsRef: { current: new Map([[1, createMockTransport('pty-pane-1')]]) }
+      paneTransportsRef: { current: new Map([[1, createMockTransport('pty-pane-1')]]) },
+      clearExitedPanePtyLayoutBinding: vi.fn(() => {
+        mockStoreState = {
+          ...mockStoreState,
+          terminalLayoutsByTabId: {
+            ...mockStoreState.terminalLayoutsByTabId,
+            'tab-1': {
+              root: {
+                type: 'split',
+                direction: 'horizontal',
+                first: { type: 'leaf', leafId: LEAF_1 },
+                second: { type: 'leaf', leafId: LEAF_2 },
+                ratio: 0.5
+              },
+              activeLeafId: LEAF_1,
+              expandedLeafId: null,
+              ptyIdsByLeafId: { [LEAF_1]: 'pty-pane-1' }
+            }
+          }
+        }
+      })
     })
 
     connectPanePty(createPane(2) as never, manager as never, deps as never)
@@ -867,6 +897,7 @@ describe('connectPanePty', () => {
     expect(deps.clearTabPtyId).toHaveBeenCalledWith('tab-1', 'pty-pane-2')
     expect(deps.onPtyExitRef.current).not.toHaveBeenCalled()
     expect(manager.closePane).not.toHaveBeenCalled()
+    expect(manager.setActivePane).toHaveBeenCalledWith(1, { focus: true })
   })
 
   it('closes a split pane when an established PTY exits after output', async () => {

src/renderer/src/components/terminal-pane/pty-connection.ts

@@ -1293,6 +1293,35 @@ export function connectPanePty(
     }
   })
 
+  const focusSurvivingPtyPaneAfterKeptExit = (): void => {
+    if (manager.getActivePane()?.id !== pane.id) {
+      return
+    }
+    const hasPtyBinding = (paneId: number): boolean =>
+      Boolean(deps.paneTransportsRef.current.get(paneId)?.getPtyId())
+    const repairedActiveLeafId =
+      useAppStore.getState().terminalLayoutsByTabId[deps.tabId]?.activeLeafId ?? null
+    const repairedActivePaneId = repairedActiveLeafId
+      ? manager.getNumericIdForLeaf(repairedActiveLeafId)
+      : null
+    const targetPaneId =
+      repairedActivePaneId !== null &&
+      repairedActivePaneId !== pane.id &&
+      hasPtyBinding(repairedActivePaneId)
+        ? repairedActivePaneId
+        : (manager
+            .getPanes()
+            .find((candidate) => candidate.id !== pane.id && hasPtyBinding(candidate.id))?.id ??
+          null)
+    if (targetPaneId !== null) {
+      // Why: when a newborn split PTY dies before output/input, the pane stays
+      // mounted for diagnostics; move live focus to the sibling that still owns a PTY.
+      manager.setActivePane(targetPaneId, {
+        focus: deps.isActiveRef.current && deps.isVisibleRef.current
+      })
+    }
+  }
+
   const onExit = (ptyId: string): void => {
     const currentPaneTransport = deps.paneTransportsRef.current.get(pane.id)
     if (currentPaneTransport && currentPaneTransport !== transport) {
@@ -1346,6 +1375,7 @@ export function connectPanePty(
     ) {
       // Why: a freshly split pane can lose its newborn PTY during setup; keep
       // the split visible so the failed session does not immediately collapse.
+      focusSurvivingPtyPaneAfterKeptExit()
       return
     }
     manager.closePane(pane.id)

src/renderer/src/components/terminal-pane/remote-runtime-pty-transport.test.ts

@@ -343,9 +343,7 @@ describe('createRemoteRuntimePtyTransport', () => {
   })
 
   it('ignores stale attach subscription rejection after reattaching a newer remote terminal', async () => {
-    let rejectOldSubscription: (error: Error) => void = () => {
-      throw new Error('old subscription reject was not captured')
-    }
+    let rejectOldSubscription: ((error: Error) => void) | null = null
     const newStream = {
       streamId: 2,
       sendInput: vi.fn(() => true),
@@ -389,7 +387,7 @@ describe('createRemoteRuntimePtyTransport', () => {
     })
     await vi.waitFor(() => expect(subscribeTerminal).toHaveBeenCalledTimes(2))
 
-    rejectOldSubscription(new Error('terminal_handle_stale'))
+    rejectOldSubscription?.(new Error('terminal_handle_stale'))
     await Promise.resolve()
     await Promise.resolve()
 

src/renderer/src/components/terminal-pane/terminal-shutdown-layout-capture.test.ts

@@ -366,4 +366,47 @@ describe('captureTerminalShutdownLayout', () => {
     expect(layout.activeLeafId).toBe(LEAF_ID_2)
     expect(layout.ptyIdsByLeafId).toEqual({ [LEAF_ID_2]: 'pty-2' })
   })
+
+  it('does not preserve a stale prior PTY binding for active shutdown focus', async () => {
+    const { captureTerminalShutdownLayout } = await import('./terminal-shutdown-layout-capture')
+    const paneWithoutPty = {
+      id: 1,
+      leafId: LEAF_ID,
+      stablePaneId: LEAF_ID,
+      terminal: { options: { scrollback: 1_000 } },
+      serializeAddon: {
+        serialize: vi.fn(() => '')
+      }
+    }
+    const paneWithPty = {
+      id: 2,
+      leafId: LEAF_ID_2,
+      stablePaneId: LEAF_ID_2,
+      terminal: { options: { scrollback: 1_000 } },
+      serializeAddon: {
+        serialize: vi.fn(() => '')
+      }
+    }
+    const manager = {
+      getPanes: vi.fn(() => [paneWithoutPty, paneWithPty]),
+      getActivePane: vi.fn(() => paneWithoutPty)
+    }
+
+    const layout = captureTerminalShutdownLayout({
+      manager: manager as never,
+      container: mockRootForSplit(),
+      expandedPaneId: null,
+      paneTransports: new Map([[2, { getPtyId: vi.fn(() => 'pty-2') }]]),
+      paneTitlesByPaneId: {},
+      existingLayout: {
+        root: null,
+        activeLeafId: LEAF_ID,
+        expandedLeafId: null,
+        ptyIdsByLeafId: { [LEAF_ID]: 'stale-pty', [LEAF_ID_2]: 'pty-2' }
+      }
+    })
+
+    expect(layout.activeLeafId).toBe(LEAF_ID_2)
+    expect(layout.ptyIdsByLeafId).toEqual({ [LEAF_ID_2]: 'pty-2' })
+  })
 })

src/renderer/src/components/terminal-pane/terminal-shutdown-layout-capture.ts

@@ -133,7 +133,8 @@ export function captureTerminalShutdownLayout({
   })
   const ptyIdsByLeafId = { ...preservedPtyIdsByLeafId, ...livePtyIdsByLeafId }
   // Why: shutdown snapshots can otherwise persist focus on a mounted pane whose
-  // transport was already cleared during PTY exit/reconnect cleanup.
+  // transport was already cleared during PTY exit/reconnect cleanup. Unlike
+  // scrollback, PTY bindings only preserve prior ids during a live attach gap.
   layout.activeLeafId = resolveTerminalLayoutActiveLeafId({
     root: layout.root,
     activeLeafId: layout.activeLeafId,

src/renderer/src/store/slices/terminals-hydration.test.ts

@@ -139,6 +139,58 @@ describe('hydrateWorkspaceSession', () => {
     })
   })
 
+  it('moves restored active focus from a dead split leaf to a pty-backed sibling', () => {
+    const store = createTestStore()
+    const worktreeId = 'repo1::/wt-1'
+    const liveLeftLeafId = '9ee09218-72a5-4e1c-b075-729e937d4e29'
+    const liveRightLeafId = 'f5fc66b1-ec43-404b-b7b0-a06f0db34940'
+    const deadActiveLeafId = 'fbf63fd9-34d6-4387-9109-562f7c02bc4c'
+    seedStore(store, {
+      worktreesByRepo: {
+        repo1: [makeWorktree({ id: worktreeId, repoId: 'repo1', path: '/wt-1' })]
+      }
+    })
+
+    const session: WorkspaceSessionState = {
+      activeRepoId: 'repo1',
+      activeWorktreeId: worktreeId,
+      activeTabId: 'tab-1',
+      tabsByWorktree: {
+        [worktreeId]: [makeTab({ id: 'tab-1', worktreeId, ptyId: 'old-pty' })]
+      },
+      terminalLayoutsByTabId: {
+        'tab-1': {
+          root: {
+            type: 'split',
+            direction: 'horizontal',
+            first: { type: 'leaf', leafId: liveLeftLeafId },
+            second: {
+              type: 'split',
+              direction: 'vertical',
+              first: { type: 'leaf', leafId: liveRightLeafId },
+              second: { type: 'leaf', leafId: deadActiveLeafId }
+            }
+          },
+          activeLeafId: deadActiveLeafId,
+          expandedLeafId: null,
+          ptyIdsByLeafId: {
+            [liveLeftLeafId]: 'daemon-session-left',
+            [liveRightLeafId]: 'daemon-session-right'
+          },
+          buffersByLeafId: {
+            [deadActiveLeafId]: 'retained scrollback'
+          }
+        }
+      }
+    }
+
+    store.getState().hydrateWorkspaceSession(session)
+
+    // Why: restart can preserve scrollback for an exited pane while live siblings
+    // reattach. Keyboard focus must land on a PTY-backed pane, not the dead leaf.
+    expect(store.getState().terminalLayoutsByTabId['tab-1']?.activeLeafId).toBe(liveLeftLeafId)
+  })
+
   it('hydrates floating terminal tabs even though they are not repo worktrees', () => {
     const store = createTestStore()
     const session: WorkspaceSessionState = {

src/renderer/src/store/slices/terminals.ts

@@ -44,7 +44,10 @@ import {
   restorePtyDataHandlersAfterFailedShutdown,
   unregisterPtyDataHandlers
 } from '@/components/terminal-pane/pty-transport'
-import { normalizeTerminalLayoutSnapshot } from '@/components/terminal-pane/terminal-layout-leaf-ids'
+import {
+  normalizeTerminalLayoutSnapshot,
+  resolvePtyBoundActiveLeafId
+} from '@/components/terminal-pane/terminal-layout-leaf-ids'
 import { shutdownBufferCaptures } from '@/components/terminal-pane/shutdown-buffer-captures'
 import { callRuntimeRpc } from '@/runtime/runtime-rpc-client'
 import { parseRemoteRuntimePtyId } from '@/runtime/runtime-terminal-stream'
@@ -2780,7 +2783,15 @@ export const createTerminalSlice: StateCreator<AppState, [], [], TerminalSlice>
               const tab = Object.values(tabsByWorktree)
                 .flat()
                 .find((entry) => entry.id === tabId)
-              return [tabId, tab ? sanitizeTerminalLayoutPaneTitles(normalized, tab) : normalized]
+              const sanitized = tab ? sanitizeTerminalLayoutPaneTitles(normalized, tab) : normalized
+              const activeLeafId = sanitized.root
+                ? resolvePtyBoundActiveLeafId({
+                    root: sanitized.root,
+                    activeLeafId: sanitized.activeLeafId,
+                    ptyIdsByLeafId: sanitized.ptyIdsByLeafId
+                  })
+                : sanitized.activeLeafId
+              return [tabId, { ...sanitized, activeLeafId }]
             })
         )
       }