diff --git a/config/skill-overrides/xlsx/recalc.py b/config/skill-overrides/xlsx/recalc.py
index 74dc430b..6a6f6030 100644
--- a/config/skill-overrides/xlsx/recalc.py
+++ b/config/skill-overrides/xlsx/recalc.py
@@ -30,6 +30,8 @@ def inspect_workbook(path):
                     cached = values[sheet.title][cell.coordinate]
                     if cached.data_type == "e":
                         errors.setdefault(str(cached.value), []).append(location)
+                    elif cell.data_type == "f" and cached.value is None:
+                        errors.setdefault("MISSING_FORMULA_CACHE", []).append(location)
         return formula_cells, errors
     finally:
         formulas.close()
diff --git a/plugins/codex/plugins/xlsx/skills/xlsx/scripts/recalc.py b/plugins/codex/plugins/xlsx/skills/xlsx/scripts/recalc.py
index 74dc430b..6a6f6030 100644
--- a/plugins/codex/plugins/xlsx/skills/xlsx/scripts/recalc.py
+++ b/plugins/codex/plugins/xlsx/skills/xlsx/scripts/recalc.py
@@ -30,6 +30,8 @@ def inspect_workbook(path):
                     cached = values[sheet.title][cell.coordinate]
                     if cached.data_type == "e":
                         errors.setdefault(str(cached.value), []).append(location)
+                    elif cell.data_type == "f" and cached.value is None:
+                        errors.setdefault("MISSING_FORMULA_CACHE", []).append(location)
         return formula_cells, errors
     finally:
         formulas.close()
diff --git a/scripts/tests/test_document_portability.py b/scripts/tests/test_document_portability.py
index 8f0a64ab..6eb8c066 100644
--- a/scripts/tests/test_document_portability.py
+++ b/scripts/tests/test_document_portability.py
@@ -1,11 +1,15 @@
 import importlib.util
 import subprocess
+import sys
 import tempfile
+import types
 import unittest
 import zipfile
 from pathlib import Path
 from unittest.mock import patch
 
+from openpyxl import Workbook
+
 ROOT = Path(__file__).resolve().parents[2]
 COMMON = ROOT / "config/skill-overrides/common"
 
@@ -17,6 +21,16 @@ def load_module(name):
     return module
 
 
+def load_recalc():
+    office = types.ModuleType("office.soffice")
+    office.run_soffice = lambda *args, **kwargs: None
+    spec = importlib.util.spec_from_file_location("market_recalc", ROOT / "config/skill-overrides/xlsx/recalc.py")
+    module = importlib.util.module_from_spec(spec)
+    with patch.dict(sys.modules, {"office.soffice": office}):
+        spec.loader.exec_module(module)
+    return module
+
+
 class OfficePortabilityTests(unittest.TestCase):
     def test_windows_install_path_and_arguments_with_spaces(self):
         office = load_module("soffice")
@@ -72,6 +86,41 @@ class OfficePortabilityTests(unittest.TestCase):
                 package.unpack(source, root / "unpacked")
             self.assertFalse((root / "escape.txt").exists())
 
+    def test_formula_without_cache_is_not_success(self):
+        recalc = load_recalc()
+        with tempfile.TemporaryDirectory() as temporary:
+            source = Path(temporary) / "中文.xlsx"
+            workbook = Workbook()
+            workbook.active["A1"] = "=1+1"
+            workbook.save(source)
+            formulas, errors = recalc.inspect_workbook(source)
+            self.assertEqual(formulas, {"Sheet!A1"})
+            self.assertEqual(errors, {"MISSING_FORMULA_CACHE": ["Sheet!A1"]})
+
+    def test_recalc_timeout_preserves_original(self):
+        recalc = load_recalc()
+        with tempfile.TemporaryDirectory() as temporary:
+            source = Path(temporary) / "中文.xlsx"
+            Workbook().save(source)
+            before = source.read_bytes()
+            with patch.object(recalc, "run_soffice", side_effect=subprocess.TimeoutExpired("soffice", 1)):
+                report = recalc.recalc(source, 1)
+            self.assertIn("error", report)
+            self.assertEqual(source.read_bytes(), before)
+
+    def test_recalc_external_links_refused_without_conversion(self):
+        recalc = load_recalc()
+        with tempfile.TemporaryDirectory() as temporary:
+            source = Path(temporary) / "linked.xlsx"
+            with zipfile.ZipFile(source, "w") as archive:
+                archive.writestr("xl/externalLinks/externalLink1.xml", "<externalLink/>")
+            before = source.read_bytes()
+            with patch.object(recalc, "run_soffice") as convert:
+                report = recalc.recalc(source)
+            self.assertIn("error", report)
+            convert.assert_not_called()
+            self.assertEqual(source.read_bytes(), before)
+
 
 if __name__ == "__main__":
     unittest.main()