diff --git a/core/tests/unit/test_typed_metadata.py b/core/tests/unit/test_typed_metadata.py
index 198c3397..177cd1ed 100644
--- a/core/tests/unit/test_typed_metadata.py
+++ b/core/tests/unit/test_typed_metadata.py
@@ -157,6 +157,18 @@ def test_number_coercion_rejects_nan_and_infinity(self):
         with pytest.raises(TypedMetadataError, match="cannot store NaN or infinite"):
             _normalize_values({"value": float("inf")}, {"value": "number"})
 
+    def test_number_coercion_rejects_nan_and_infinity_strings(self):
+        """Non-finite values supplied as strings must be rejected too.
+
+        Regression: the string branch parsed "inf"/"nan" (and overflowing
+        literals like "1e400") into non-finite floats without the finite check
+        applied to numeric inputs, letting them through to storage where they
+        break JSON serialization and Postgres double precision columns.
+        """
+        for token in ("inf", "-inf", "Infinity", "nan", "1e400"):
+            with pytest.raises(TypedMetadataError, match="cannot store NaN or infinite"):
+                _normalize_values({"value": token}, {"value": "number"})
+
     def test_decimal_coercion(self):
         """Test decimal coercion from various types."""
         metadata = {
diff --git a/core/utils/typed_metadata.py b/core/utils/typed_metadata.py
index 307dc825..c9f9ff8a 100644
--- a/core/utils/typed_metadata.py
+++ b/core/utils/typed_metadata.py
@@ -238,9 +238,12 @@ def _coerce_number(value: Any, field: str) -> int | float:
         try:
             if all(ch.isdigit() or ch in {"+", "-", "_"} for ch in text.replace("_", "")) and "." not in text:
                 return int(text.replace("_", ""))
-            return float(text)
+            parsed = float(text)
         except ValueError as exc:  # noqa: BLE001
             raise TypedMetadataError(f"Metadata field '{field}' expects a numeric value.") from exc
+        if math.isnan(parsed) or math.isinf(parsed):
+            raise TypedMetadataError(f"Metadata field '{field}' cannot store NaN or infinite values.")
+        return parsed
 
     raise TypedMetadataError(f"Metadata field '{field}' expects a numeric value.")