diff --git a/src/main/persistence/loading-store/session-host-partitions.ts b/src/main/persistence/loading-store/session-host-partitions.ts
index a446ae30576..e102b8c679f 100644
--- a/src/main/persistence/loading-store/session-host-partitions.ts
+++ b/src/main/persistence/loading-store/session-host-partitions.ts
@@ -194,8 +194,11 @@ export function setHostWorkspaceSession(
   hostId: ExecutionHostId,
   session: WorkspaceSessionState
 ): void {
-  const prior =
+  const persisted =
     owner[sessionHostPartitionOperationsContext].runtime.state.workspaceSessionsByHostId?.[hostId]
+  const prior = persisted ? withRequiredWorkspaceSessionMaps(persisted) : undefined
+  // Host slices omit empty maps; retirement and rebasing need them before inspecting membership.
+  session = withRequiredWorkspaceSessionMaps(session)
   // Why here and not at the callers: the before-unload stage path writes the renderer's payload
   // straight through, so a per-caller guard leaves the quit write erasing runtime-authored rows.
   session = dropClosedTerminalTabs(preserveRuntimeAuthoredWorkspaceSessionFields(session, prior))
diff --git a/src/main/persistence/loading-store/store-host-partition-before-unload.test.ts b/src/main/persistence/loading-store/store-host-partition-before-unload.test.ts
new file mode 100644
index 00000000000..9166da6fcab
--- /dev/null
+++ b/src/main/persistence/loading-store/store-host-partition-before-unload.test.ts
@@ -0,0 +1,110 @@
+import { mkdtempSync, rmSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, describe, expect, it } from 'vitest'
+import { getDefaultWorkspaceSession } from '../../../shared/constants'
+import type { WorkspaceSessionState } from '../../../shared/workspace-session-state-types'
+import {
+  closeTestStores,
+  createSqliteTestStore,
+  makeTerminalTab
+} from '../../persistence-test-harness'
+import { Store } from './store'
+
+const HOST_ID = 'ssh:target-1'
+const WORKTREE = 'repo-1::/srv/app'
+const FOLDER_WORKTREE = 'folder:folder-1'
+const TAB_ID = 'host-tab'
+const LEAF_ID = '11111111-1111-4111-8111-111111111111'
+
+const directories: string[] = []
+afterEach(async () => {
+  await closeTestStores()
+  for (const directory of directories.splice(0)) {
+    rmSync(directory, { recursive: true, force: true })
+  }
+})
+
+function openStore(): Store {
+  const directory = mkdtempSync(join(tmpdir(), 'orca-host-before-unload-'))
+  directories.push(directory)
+  return createSqliteTestStore(Store, { dataFile: join(directory, 'orca-data.json') })
+}
+
+/** The renderer's host split leaves out terminal maps for a host with only editor tabs. */
+function editorOnlySlice(worktreeId = WORKTREE): WorkspaceSessionState {
+  const slice: WorkspaceSessionState = {
+    ...getDefaultWorkspaceSession(),
+    openFilesByWorktree: {
+      [worktreeId]: [
+        { worktreeId, filePath: '/srv/app/a.ts', relativePath: 'a.ts', language: 'typescript' }
+      ]
+    }
+  }
+  Reflect.deleteProperty(slice, 'tabsByWorktree')
+  Reflect.deleteProperty(slice, 'terminalLayoutsByTabId')
+  return slice
+}
+
+describe('before-unload staging of an editor-only host slice', () => {
+  it.each([
+    [{}, WORKTREE],
+    [{ 'repo-1': 1 }, WORKTREE],
+    [{ 'repo-1': 1 }, FOLDER_WORKTREE]
+  ])('saves the slice when the partition has topology revisions %j (%s)', (revisions, worktree) => {
+    const store = openStore()
+    store.setWorkspaceSession(
+      { ...getDefaultWorkspaceSession(), terminalTopologyRevisionByRepoId: revisions },
+      HOST_ID
+    )
+
+    store.stageWorkspaceSessionBeforeUnload(editorOnlySlice(worktree), HOST_ID)
+
+    const saved = store.getWorkspaceSession(HOST_ID)
+    expect(saved.openFilesByWorktree?.[worktree]).toHaveLength(1)
+    expect(saved.tabsByWorktree).toEqual({})
+    expect(saved.terminalLayoutsByTabId).toEqual({})
+  })
+
+  it('accepts an older saved partition that is missing the terminal maps', () => {
+    const store = openStore()
+    store.setWorkspaceSession(
+      { ...getDefaultWorkspaceSession(), terminalTopologyRevisionByRepoId: { 'repo-1': 1 } },
+      HOST_ID
+    )
+    const older = store.getWorkspaceSession(HOST_ID)
+    Reflect.deleteProperty(older, 'tabsByWorktree')
+    Reflect.deleteProperty(older, 'terminalLayoutsByTabId')
+
+    store.stageWorkspaceSessionBeforeUnload(editorOnlySlice(), HOST_ID)
+
+    expect(store.getWorkspaceSession(HOST_ID).tabsByWorktree).toEqual({})
+  })
+
+  it('keeps fenced live terminal tabs the stale slice leaves out', () => {
+    const store = openStore()
+    const tab = makeTerminalTab({ id: TAB_ID, worktreeId: WORKTREE, ptyId: 'live-pty' })
+    const layout = {
+      root: { type: 'leaf', leafId: LEAF_ID },
+      activeLeafId: LEAF_ID,
+      expandedLeafId: null,
+      ptyIdsByLeafId: { [LEAF_ID]: 'live-pty' }
+    } as const
+    store.setWorkspaceSession(
+      {
+        ...getDefaultWorkspaceSession(),
+        tabsByWorktree: { [WORKTREE]: [tab] },
+        terminalLayoutsByTabId: { [TAB_ID]: layout },
+        terminalTopologyRevisionByRepoId: { 'repo-1': 1 }
+      },
+      HOST_ID
+    )
+
+    store.stageWorkspaceSessionBeforeUnload(editorOnlySlice(), HOST_ID)
+
+    expect(store.getWorkspaceSession(HOST_ID)).toMatchObject({
+      tabsByWorktree: { [WORKTREE]: [tab] },
+      terminalLayoutsByTabId: { [TAB_ID]: layout }
+    })
+  })
+})