diff --git a/headroom/cache/dynamic_detector.py b/headroom/cache/dynamic_detector.py
index 5030862e9..3c5117f83 100644
--- a/headroom/cache/dynamic_detector.py
+++ b/headroom/cache/dynamic_detector.py
@@ -777,20 +777,23 @@ class SemanticDetector:
             return [], "numpy not installed. Install with: pip install numpy"
 
         sentence_texts = [s[0] for s in sentences]
-        if self._model is None or self._exemplar_embeddings is None:
+        # `is_available` only guarantees `_model` is set. Guard each piece
+        # separately and *before* encoding so a None never reaches `.T` (a
+        # real crash), mypy can narrow the `Any | None` attributes, and the
+        # caller gets a warning that names the actual missing piece — the
+        # model vs. the exemplar matrix. (Folding both into one guard, as a
+        # prior change did, returned the generic "semantic detector" message
+        # even when only the exemplars were missing.)
+        if self._model is None:
             return [], self._load_error or "semantic detector is not initialized"
+        if self._exemplar_embeddings is None:
+            return [], "exemplar embeddings not initialized"
 
         sentence_embeddings = self._model.encode(
             sentence_texts,
             convert_to_numpy=True,
         )
 
-        # Compute similarities. `is_available` only guarantees `_model` is
-        # set; guard the exemplar matrix explicitly so a None never reaches
-        # `.T` (real crash) and mypy can narrow the `Any | None` attribute.
-        if self._exemplar_embeddings is None:
-            return [], "exemplar embeddings not initialized"
-
         similarities = np.dot(sentence_embeddings, self._exemplar_embeddings.T)
 
         for i, (text, start, end) in enumerate(sentences):
diff --git a/tests/test_cache/test_dynamic_detector.py b/tests/test_cache/test_dynamic_detector.py
index 154a309d9..309efa66f 100644
--- a/tests/test_cache/test_dynamic_detector.py
+++ b/tests/test_cache/test_dynamic_detector.py
@@ -486,7 +486,9 @@ class TestSemanticDetector:
         spans, warning = detector.detect("The current stock price changes every minute.")
 
         assert spans == []
-        assert warning == "semantic detector is not initialized"
+        # Model present but exemplar matrix missing → the warning names the
+        # actual missing piece (matches TestSemanticDetectorGuards below).
+        assert warning == "exemplar embeddings not initialized"
 
 
 class TestIntegrationWithAllTiers: