diff --git a/tests/test_audit_regressions.py b/tests/test_audit_regressions.py
index 4d75d9e5..de818c17 100644
--- a/tests/test_audit_regressions.py
+++ b/tests/test_audit_regressions.py
@@ -20,6 +20,13 @@ from unittest import mock
 
 import yaml
 
+try:
+    import jsonschema  # noqa: F401
+except ImportError:
+    HAS_JSONSCHEMA = False
+else:
+    HAS_JSONSCHEMA = True
+
 ROOT = Path(__file__).resolve().parent.parent
 TMP_ROOT = ROOT / "tmp" / "tests"
 TMP_ROOT.mkdir(parents=True, exist_ok=True)
@@ -229,6 +236,7 @@ class UnreachableCitationRegressions(unittest.TestCase):
     check is offline and runs on every push.
     """
 
+    @unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
     def _hits(self, text: str) -> bool:
         import validate_schemas
 
@@ -255,6 +263,7 @@ class UnreachableCitationRegressions(unittest.TestCase):
             with self.subTest(citation=good):
                 self.assertFalse(self._hits(good))
 
+    @unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
     def test_the_corpus_carries_none(self):
         import validate_schemas
 
@@ -1039,6 +1048,7 @@ class InstallerBoundaryRegressions(unittest.TestCase):
         with self.assertRaisesRegex(ValueError, "unsafe"):
             install._validate_manifest(manifest, "retroarch")
 
+    @unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
     def test_target_schema_accepts_the_null_the_generator_emits(self):
         """The schema and generate_target_manifests must agree on null.
 
@@ -1056,6 +1066,7 @@ class InstallerBoundaryRegressions(unittest.TestCase):
         document = {"windows": None, "switch": ["a5200"]}
         self.assertEqual(list(validator.iter_errors(document)), [])
 
+    @unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
     def test_pack_manifests_are_read_from_inside_the_archive(self):
         """generate_pack writes manifest.json into the ZIP, not beside it.
 
diff --git a/tests/test_directory_entries.py b/tests/test_directory_entries.py
index 7bc522d8..814667e1 100644
--- a/tests/test_directory_entries.py
+++ b/tests/test_directory_entries.py
@@ -19,6 +19,13 @@ from pathlib import Path
 
 import yaml
 
+try:
+    import jsonschema  # noqa: F401
+except ImportError:
+    HAS_JSONSCHEMA = False
+else:
+    HAS_JSONSCHEMA = True
+
 REPO_ROOT = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(REPO_ROOT / "scripts"))
 
@@ -246,6 +253,7 @@ class PackCarriesADirectory(DirectoryFixture):
         self.assertEqual(missing, ["Fonts"])
 
 
+@unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
 class ProfileContract(unittest.TestCase):
     """One way to say an entry is a directory, so one place reads it."""
 
diff --git a/tests/test_optional_dependencies.py b/tests/test_optional_dependencies.py
new file mode 100644
index 00000000..86fa427a
--- /dev/null
+++ b/tests/test_optional_dependencies.py
@@ -0,0 +1,55 @@
+"""The suite runs with only the build dependencies installed.
+
+jsonschema is needed by the schema validator and by CI, nowhere else. Six
+tests imported it unguarded, so a contributor with stdlib and pyyaml saw
+fifteen errors instead of skipped schema checks.
+"""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+
+HIDE_AND_RUN = """
+import io
+import sys
+import unittest
+
+sys.modules["jsonschema"] = None
+names = sys.argv[1:]
+suite = unittest.defaultTestLoader.loadTestsFromNames(names)
+result = unittest.TextTestRunner(stream=io.StringIO(), verbosity=0).run(suite)
+for test, trace in result.errors + result.failures:
+    print(test.id())
+    print(trace.strip().splitlines()[-1])
+sys.exit(0 if result.wasSuccessful() else 1)
+"""
+
+
+class SuiteWithoutJsonschema(unittest.TestCase):
+    def test_every_module_skips_instead_of_erroring(self):
+        names = sorted(
+            f"tests.{path.stem}"
+            for path in (REPO_ROOT / "tests").glob("test_*.py")
+            if path.stem != Path(__file__).stem
+            and any(
+                token in path.read_text(encoding="utf-8")
+                for token in ("jsonschema", "validate_schemas")
+            )
+        )
+        completed = subprocess.run(
+            [sys.executable, "-c", HIDE_AND_RUN, *names],
+            cwd=REPO_ROOT,
+            capture_output=True,
+            text=True,
+            timeout=600,
+        )
+        self.assertEqual(completed.returncode, 0, completed.stdout + completed.stderr[-2000:])
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/test_pack_counts.py b/tests/test_pack_counts.py
index 66a3727f..dddfb6a5 100644
--- a/tests/test_pack_counts.py
+++ b/tests/test_pack_counts.py
@@ -20,6 +20,13 @@ from pathlib import Path
 
 import yaml
 
+try:
+    import jsonschema  # noqa: F401
+except ImportError:
+    HAS_JSONSCHEMA = False
+else:
+    HAS_JSONSCHEMA = True
+
 REPO_ROOT = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(REPO_ROOT / "scripts"))
 
@@ -142,6 +149,7 @@ class ManifestStatesWhatThePackHolds(PackCountFixture):
         self.assertEqual(manifest["total_files"], 2)
         self.assertEqual(manifest["pack_files"], 2 + 3 + len(builder.PACK_DOCUMENTS))
 
+    @unittest.skipUnless(HAS_JSONSCHEMA, "validating a schema needs jsonschema")
     def test_the_manifest_schema_accepts_the_two_figures(self):
         from jsonschema import Draft202012Validator