fix(skill): reconcile rebase with runner contracts

tests/integration_tests/box/test_cloud_box_admission_integration.py

@@ -411,7 +411,39 @@ async def test_cloud_core_skills_mount_generically_and_do_not_require_box_entitl
         )
         assert [skill['name'] for skill in await repository.list_skills(ineligible)] == ['docs-only']
         with pytest.raises(EntitlementUnavailableError):
-            await service.execute_tool({'command': 'true'}, _query(ineligible, 92))
+            await RunnerBoxService(service).acquire(ineligible, {'reuse_key': 'global'}, _query(ineligible, 92))
+    finally:
+        server_task.cancel()
+        client_task.cancel()
+        await runtime.shutdown()
+
+
+@pytest.mark.asyncio
+async def test_activated_skill_mount_changes_recreate_shared_box_session(tmp_path):
+    service, runtime, backend, entitlements, server_task, client_task = await _stack(tmp_path)
+    context = _context('workspace-a')
+    entitlements.snapshots[context.workspace_uuid] = _snapshot(context.workspace_uuid)
+    try:
+        first_query = await _bound_query(service, context, 101)
+        await service.execute_tool({'command': 'echo before activation'}, first_query)
+        assert len(backend.started_specs) == 1
+
+        skill = await service.ap.skill_repository.create_skill(
+            context, {'name': 'demo', 'instructions': 'Run a script'}
+        )
+        second_query = await _bound_query(service, context, 102)
+        skill_loader.register_activated_skill(second_query, skill)
+        await service.execute_tool(
+            {'command': 'echo with skill'},
+            second_query,
+            read_only_mounts=skill_loader.build_execution_mounts(service.ap, second_query),
+        )
+        assert len(backend.started_specs) == 2
+        assert backend.stopped_sessions == [backend.started_specs[0].session_id]
+
+        await service.execute_tool({'command': 'echo first query again'}, first_query)
+        assert len(backend.started_specs) == 3
+        assert backend.stopped_sessions == [backend.started_specs[0].session_id] * 2
     finally:
         server_task.cancel()
         client_task.cancel()