diff --git a/novelforge/names.py b/novelforge/names.py
index 60faf99..24b0991 100644
--- a/novelforge/names.py
+++ b/novelforge/names.py
@@ -51,10 +51,11 @@
 
 # Validate that every allowed genre has a name-pool mapping.
 _missing_name_genres = ALLOWED_GENRES - _GENRE_GROUP.keys()
-assert not _missing_name_genres, (
-    f"Genres missing from _GENRE_GROUP in names.py: {sorted(_missing_name_genres)}. "
-    f"Add a style-group mapping for each."
-)
+if _missing_name_genres:
+    raise ValueError(
+        f"Genres missing from _GENRE_GROUP in names.py: {sorted(_missing_name_genres)}. "
+        f"Add a style-group mapping for each."
+    )
 
 # ---------------------------------------------------------------------------
 # Name pool data
diff --git a/novelforge/voice.py b/novelforge/voice.py
index 391aa5f..09e9213 100644
--- a/novelforge/voice.py
+++ b/novelforge/voice.py
@@ -241,10 +241,11 @@
 
 # Validate that every allowed genre has voice weights.
 _missing_voice_genres = ALLOWED_GENRES - _GENRE_VOICE_WEIGHTS.keys()
-assert not _missing_voice_genres, (
-    f"Genres missing from _GENRE_VOICE_WEIGHTS in voice.py: {sorted(_missing_voice_genres)}. "
-    f"Add a voice weight mapping for each."
-)
+if _missing_voice_genres:
+    raise ValueError(
+        f"Genres missing from _GENRE_VOICE_WEIGHTS in voice.py: {sorted(_missing_voice_genres)}. "
+        f"Add a voice weight mapping for each."
+    )
 
 
 def select_voice_seed(genre: str = "", premise: str = "") -> dict[str, str]:
diff --git a/tests/test_names.py b/tests/test_names.py
index 1eb9f3a..bed284f 100644
--- a/tests/test_names.py
+++ b/tests/test_names.py
@@ -1,7 +1,11 @@
 """Tests for the novelforge.names module (genre-aware name pools)."""
 
+import importlib
+
 import pytest
 
+import novelforge.names
+import novelforge.validation
 from novelforge.names import (
     _GENRE_GROUP,
     _NAMES,
@@ -167,3 +171,22 @@ def test_output_mentions_male_female_last(self):
         assert "male first names" in result.lower()
         assert "female first names" in result.lower()
         assert "last names" in result.lower()
+
+
+# ---------------------------------------------------------------------------
+# Genre coverage validation raises ValueError (not silenced by -O flag)
+# ---------------------------------------------------------------------------
+
+class TestNameGenreValidation:
+    """names.py must raise ValueError for missing genre mappings even under -O."""
+
+    def test_raises_value_error_when_genre_missing_from_genre_group(self, monkeypatch):
+        """Reloading names.py with an extra ALLOWED_GENRES entry raises ValueError."""
+        extended = novelforge.validation.ALLOWED_GENRES | {"FakeGenreForTest"}
+        monkeypatch.setattr(novelforge.validation, "ALLOWED_GENRES", extended)
+        with pytest.raises(ValueError, match="FakeGenreForTest"):
+            importlib.reload(novelforge.names)
+
+    def test_no_error_when_all_genres_covered(self):
+        """Reloading names.py with the standard ALLOWED_GENRES does not raise."""
+        importlib.reload(novelforge.names)
diff --git a/tests/test_voice.py b/tests/test_voice.py
index 674f714..5049a92 100644
--- a/tests/test_voice.py
+++ b/tests/test_voice.py
@@ -2,10 +2,13 @@
 Tests for novelforge/voice.py — voice seed selection and formatting.
 """
 
+import importlib
 import random
 
 import pytest
 
+import novelforge.validation
+import novelforge.voice
 from novelforge.voice import (
     _PREMISE_KEYWORD_BOOST,
     _PREMISE_KEYWORDS,
@@ -212,3 +215,23 @@ def test_embeds_seed_content(self):
         assert seed["prose_style"] in prompt
         assert seed["emotional_register"] in prompt
         assert seed["sensory_preference"] in prompt
+
+
+
+# ---------------------------------------------------------------------------
+# Genre coverage validation raises ValueError (not silenced by -O flag)
+# ---------------------------------------------------------------------------
+
+class TestVoiceGenreValidation:
+    """voice.py must raise ValueError for missing genre mappings even under -O."""
+
+    def test_raises_value_error_when_genre_missing_from_voice_weights(self, monkeypatch):
+        """Reloading voice.py with an extra ALLOWED_GENRES entry raises ValueError."""
+        extended = novelforge.validation.ALLOWED_GENRES | {"FakeGenreForTest"}
+        monkeypatch.setattr(novelforge.validation, "ALLOWED_GENRES", extended)
+        with pytest.raises(ValueError, match="FakeGenreForTest"):
+            importlib.reload(novelforge.voice)
+
+    def test_no_error_when_all_genres_covered(self):
+        """Reloading voice.py with the standard ALLOWED_GENRES does not raise."""
+        importlib.reload(novelforge.voice)