diff --git a/scripts/generate_readme.py b/scripts/generate_readme.py
index 6daf8a8c..bc783f91 100644
--- a/scripts/generate_readme.py
+++ b/scripts/generate_readme.py
@@ -45,7 +45,6 @@ def compute_coverage(
     platforms_dir: str,
     db: dict,
     data_registry: dict | None = None,
-    supplemental_names: set[str] | None = None,
     emulators_dir: str = _EMULATORS_DIR,
 ) -> dict:
     config = load_platform_config(platform_name, platforms_dir)
@@ -54,7 +53,6 @@ def compute_coverage(
         db,
         emulators_dir,
         data_dir_registry=data_registry,
-        supplemental_names=supplemental_names,
     )
     sc = result.get("status_counts", {})
     ok = sc.get("ok", 0)
@@ -295,16 +293,14 @@ def generate_readme(db: dict, platforms_dir: str) -> str:
     platform_names = list_registered_platforms(platforms_dir, include_archived=True)
 
     from common import load_data_dir_registry
-    from cross_reference import _build_supplemental_index
 
     data_registry = load_data_dir_registry(platforms_dir)
-    suppl_names = _build_supplemental_index()
 
     coverages = {}
     for name in platform_names:
         try:
             coverages[name] = compute_coverage(
-                name, platforms_dir, db, data_registry, suppl_names
+                name, platforms_dir, db, data_registry
             )
         except FileNotFoundError:
             pass
diff --git a/scripts/generate_site.py b/scripts/generate_site.py
index 2bd6200f..45cd079b 100644
--- a/scripts/generate_site.py
+++ b/scripts/generate_site.py
@@ -3813,7 +3813,7 @@ def main() -> None:
     for name in sorted(platform_names):
         try:
             cov = compute_coverage(
-                name, args.platforms_dir, db, data_registry, suppl_names,
+                name, args.platforms_dir, db, data_registry,
                 emulators_dir=args.emulators_dir,
             )
             coverages[name] = cov
diff --git a/scripts/verify.py b/scripts/verify.py
index 0e8fa476..756e3256 100644
--- a/scripts/verify.py
+++ b/scripts/verify.py
@@ -884,7 +884,6 @@ def verify_platform(
     emu_profiles: dict | None = None,
     target_cores: set[str] | None = None,
     data_dir_registry: dict | None = None,
-    supplemental_names: set[str] | None = None,
     regions: list[str] | None = None,
 ) -> dict:
     """Verify all BIOS files for a platform, including cross-reference gaps.
@@ -1085,22 +1084,18 @@ def verify_platform(
             ):
                 file_severity[dest] = sev
 
-    # Cross-reference undeclared files
-    if supplemental_names is None:
-        from cross_reference import _build_supplemental_index
-
-        supplemental_names = _build_supplemental_index()
-    # The builder's declarations, not the enriched ones: a core file the
-    # platform also declares under another name is packed at the core's own
-    # path, and a report reading the enriched set never counted it (21 such
-    # files in the RetroArch pack).
+    # Cross-reference undeclared files, called exactly as the builder calls
+    # it: its declarations, not the enriched ones (a core file the platform
+    # also declares under another name is packed at the core's own path, 21
+    # such files in the RetroArch pack), and no names from inside archives
+    # or data trees (a loose file whose name exists only as a member of
+    # naomi2.zip was counted "in pack" while the builder shipped nothing).
     undeclared = find_undeclared_files(
         config,
         emulators_dir,
         db,
         emu_profiles,
         target_cores=target_cores,
-        data_names=supplemental_names,
         declared_names=platform_declarations(config, db, enrich=False),
     )
     if region_drops:
@@ -2226,9 +2221,6 @@ def _main(held: contextlib.ExitStack) -> None:
     groups = group_identical_platforms(
         platforms, args.platforms_dir, target_cores_cache if args.target else None
     )
-    from cross_reference import _build_supplemental_index
-
-    suppl_names = _build_supplemental_index()
 
     all_results = {}
     group_results: list[tuple[dict, list[str]]] = []
@@ -2242,7 +2234,6 @@ def _main(held: contextlib.ExitStack) -> None:
             emu_profiles,
             target_cores=tc,
             data_dir_registry=data_registry,
-            supplemental_names=suppl_names,
             regions=requested_regions,
         )
         names = [
diff --git a/tests/test_core_file_fills_declaration.py b/tests/test_core_file_fills_declaration.py
index 34ed15fc..81e42302 100644
--- a/tests/test_core_file_fills_declaration.py
+++ b/tests/test_core_file_fills_declaration.py
@@ -79,7 +79,7 @@ class ACoreFileFillsAFreeDeclaration(unittest.TestCase):
 
     def test_verify_counts_what_the_pack_counts(self):
         result = verify_platform(
-            self.config, self.db, str(self.emulators), supplemental_names=set(),
+            self.config, self.db, str(self.emulators),
         )
         out = self.root / "out"
         with redirect_stdout(io.StringIO()):
@@ -131,7 +131,7 @@ class AFileDeclaredUnderAnotherName(unittest.TestCase):
             "files": [{"name": "ROM", "path": "gs/ROM", "md5": md5, "required": True}],
         }))
         config = load_platform_config("fakeplat", str(root / "platforms"))
-        result = verify_platform(config, db, str(root / "emulators"), supplemental_names=set())
+        result = verify_platform(config, db, str(root / "emulators"))
         with redirect_stdout(io.StringIO()):
             zip_path = generate_pack(
                 "fakeplat", str(root / "platforms"), db, str(root / "bios"),
@@ -223,5 +223,41 @@ class AFileNobodyHoldsIsAnOmission(unittest.TestCase):
         self.assertEqual(omitted["diabdat.mpq"]["reason"], "not_found")
 
 
+
+class AMemberNameIsNotALooseFile(unittest.TestCase):
+    """verify counted a core file "in pack" when its name existed only as a
+    member of some ZIP (naomi2.zip's 315-6146.bin); the builder, which reads
+    no archive member names, shipped nothing."""
+
+    def test_verify_reads_undeclared_files_as_the_builder_does(self):
+        import cross_reference
+
+        _emulator_profiles_cache.clear()
+        root = Path(tempfile.mkdtemp(dir=REPO_ROOT / "tmp"))
+        self.addCleanup(shutil.rmtree, root, True)
+        (root / "platforms").mkdir()
+        (root / "emulators").mkdir()
+        (root / "platforms" / "fakeplat.yml").write_text(yaml.safe_dump({
+            "platform": "FakePlat", "verification_mode": "existence",
+            "base_destination": "system", "cores": ["naomi2core"],
+            "systems": {"sega-naomi2": {"files": []}},
+        }))
+        (root / "emulators" / "naomi2core.yml").write_text(yaml.safe_dump({
+            "emulator": "N2", "type": "libretro", "cores": ["naomi2core"],
+            "systems": ["sega-naomi2"],
+            "files": [{"name": "315-6146.bin", "required": True}],
+        }))
+        db = {"files": {}, "indexes": {"by_md5": {}, "by_name": {}, "by_crc32": {},
+                                      "by_path_suffix": {}}}
+        config = load_platform_config("fakeplat", str(root / "platforms"))
+        with mock.patch.object(cross_reference, "_build_supplemental_index",
+                               lambda *a, **k: {"315-6146.bin"}):
+            result = verify_platform(config, db, str(root / "emulators"))
+        self.assertEqual(
+            [(u["name"], u["in_repo"]) for u in result["undeclared_files"]],
+            [("315-6146.bin", False)],
+        )
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/tests/test_native_mode.py b/tests/test_native_mode.py
index 07c4601b..0a2406b2 100644
--- a/tests/test_native_mode.py
+++ b/tests/test_native_mode.py
@@ -157,7 +157,6 @@ class ThePolicyIsSpeltInOnePlace(unittest.TestCase):
         }
         result = verify.verify_platform(
             config, {"files": {}, "indexes": {}}, emu_profiles={},
-            supplemental_names=set(),
         )
         self.assertEqual(result["verification_mode"], nativemode.DEFAULT_MODE)
 
diff --git a/tests/test_region.py b/tests/test_region.py
index ac275da7..6d869170 100644
--- a/tests/test_region.py
+++ b/tests/test_region.py
@@ -659,11 +659,10 @@ class TestReportAndBuilderNarrowTogether(unittest.TestCase):
 
             plain = reporter.verify_platform(
                 config, db, str(root / "emulators"), profiles,
-                supplemental_names=set(),
             )
             narrowed = reporter.verify_platform(
                 config, db, str(root / "emulators"), profiles,
-                supplemental_names=set(), regions=["north-america"],
+                regions=["north-america"],
             )
             before = {u["name"] for u in plain["undeclared_files"]}
             after = {u["name"] for u in narrowed["undeclared_files"]}
@@ -694,11 +693,10 @@ class TestReportAndBuilderNarrowTogether(unittest.TestCase):
             profiles = common.load_emulator_profiles(str(root / "emulators"))
             plain = reporter.verify_platform(
                 config, db, str(root / "emulators"), profiles,
-                supplemental_names=set(),
             )
             narrowed = reporter.verify_platform(
                 config, db, str(root / "emulators"), profiles,
-                supplemental_names=set(), regions=["north-america"],
+                regions=["north-america"],
             )
             missing = [u["name"] for u in plain["undeclared_files"] if not u["in_repo"]]
             self.assertEqual(missing, ["jp.bin"])
@@ -722,7 +720,7 @@ class TestReportAndBuilderNarrowTogether(unittest.TestCase):
             profiles = common.load_emulator_profiles(str(root / "emulators"))
             result = reporter.verify_platform(
                 config, db, str(root / "emulators"), profiles,
-                supplemental_names=set(), regions=["brazil"],
+                regions=["brazil"],
             )
             self.assertEqual(result["region_fallbacks"], ["demo-system"])
             out = io.StringIO()
diff --git a/tests/test_twin_declarations.py b/tests/test_twin_declarations.py
index 10e39317..7a2ab26b 100644
--- a/tests/test_twin_declarations.py
+++ b/tests/test_twin_declarations.py
@@ -68,7 +68,7 @@ class TwinDeclarations(unittest.TestCase):
             },
         }
         report = verify_platform(
-            config, self.db, str(self.emulators), {}, supplemental_names=set()
+            config, self.db, str(self.emulators), {}
         )
         by_system = {d["system"]: d for d in report["details"] if d["name"] in ("N88SUB.ROM", "disk.rom")}
         statuses = sorted(d["status"] for d in by_system.values())
diff --git a/tests/test_unplaced_extras.py b/tests/test_unplaced_extras.py
index 09486e9f..e3d1df41 100644
--- a/tests/test_unplaced_extras.py
+++ b/tests/test_unplaced_extras.py
@@ -86,7 +86,7 @@ class SlugPlatform(unittest.TestCase):
 
     def test_the_report_does_not_count_it_packed(self):
         report = verify_platform(
-            self.config, self.db, "emulators", self.profiles, supplemental_names=set()
+            self.config, self.db, "emulators", self.profiles
         )
         entry = next(u for u in report["undeclared_files"] if u["name"] == "MT32_CONTROL.ROM")
         self.assertTrue(entry["in_repo"])