diff --git a/src/main/persistence.ts b/src/main/persistence.ts
index 58b5a393541..9517e6ba9f1 100644
--- a/src/main/persistence.ts
+++ b/src/main/persistence.ts
@@ -2908,7 +2908,14 @@ export function hoistSshPartitionsIntoLocalSession(
       if (missing.length === 0) {
         continue
       }
-      local.tabsByWorktree = { ...local.tabsByWorktree, [worktreeId]: [...existing, ...missing] }
+      // Cloned, not aliased. Spreading the partition's own tab objects in leaves both planes
+      // holding the SAME object, so a mutation scoped to `local` — the whole point of
+      // `arbitratedFrom` — silently rewrites the partition too, stranding a shell whose owner
+      // never voted on that decision.
+      local.tabsByWorktree = {
+        ...local.tabsByWorktree,
+        [worktreeId]: [...existing, ...missing.map((tab) => structuredClone(tab))]
+      }
       for (const tab of missing) {
         alreadyHoisted.add(tab.id)
       }
@@ -2925,7 +2932,11 @@ export function hoistSshPartitionsIntoLocalSession(
       if (!hasTab) {
         continue
       }
-      local.terminalLayoutsByTabId = { ...local.terminalLayoutsByTabId, [tabId]: layout }
+      // Cloned for the same reason: a shared layout leaks `ptyIdsByLeafId` edits across planes.
+      local.terminalLayoutsByTabId = {
+        ...local.terminalLayoutsByTabId,
+        [tabId]: structuredClone(layout)
+      }
       changed = true
     }
     for (const [paneKey, incarnationId] of Object.entries(
diff --git a/src/main/ssh-partition-upgrade-tab-loss.test.ts b/src/main/ssh-partition-upgrade-tab-loss.test.ts
index 9c0f5ed2427..c98a240bc60 100644
--- a/src/main/ssh-partition-upgrade-tab-loss.test.ts
+++ b/src/main/ssh-partition-upgrade-tab-loss.test.ts
@@ -373,4 +373,26 @@ describe('an SSH pane whose membership was persisted into the ssh partition', ()
       )
     })
   })
+
+  // The hoisted pane must not ALIAS the partition's objects. `arbitratedFrom: 'local'` exists so a
+  // decision read from one plane cannot mutate the other; a shared object defeats it silently and
+  // strands a shell whose owner never voted on that decision.
+  it('hoists copies, so mutating the local pane leaves the partition alone', async () => {
+    const before = await createStore()
+    before.setWorkspaceSession(paneSession() as never, SSH_PARTITION)
+    before.flushOrThrow()
+    stripHoistMarker()
+
+    const store = await reopenStore()
+    const localTab = (store.getWorkspaceSession().tabsByWorktree?.[WORKTREE] ?? [])[0]
+    expect(localTab, 'the pane was not hoisted, so aliasing cannot be observed').toBeDefined()
+
+    // A mutation scoped to the local plane.
+    localTab!.ptyId = null
+
+    expect(
+      store.getWorkspaceSession(SSH_PARTITION).tabsByWorktree?.[WORKTREE]?.[0]?.ptyId,
+      'a local-only edit reached through into the ssh partition'
+    ).toBe(PTY)
+  })
 })