fix: reject non-finite scorer weights

src/scorers/util.ts

@@ -9,7 +9,8 @@ export function clamp01(n: number): number {
 /** Read the weight from a spec, defaulting to 1 and rejecting negatives. */
 export function specWeight(spec: ScorerSpec): number {
   const w = typeof spec.weight === "number" ? spec.weight : 1;
-  return w < 0 ? 0 : w;
+  if (!Number.isFinite(w) || w < 0) return 0;
+  return w;
 }
 
 /** Convenience builder that fills in the boilerplate of a {@link ScoreResult}. */

src/suite.ts

@@ -137,8 +137,8 @@ function validateScorer(data: unknown, caseId: string, index: number): ScorerSpe
   );
   if (s.weight !== undefined) {
     assert(
-      typeof s.weight === "number" && s.weight >= 0,
-      `case "${caseId}" scorers[${index}].weight must be a non-negative number`,
+      typeof s.weight === "number" && Number.isFinite(s.weight) && s.weight >= 0,
+      `case "${caseId}" scorers[${index}].weight must be a finite non-negative number`,
     );
   }
   return s as ScorerSpec;

tests/suite.test.ts

@@ -72,6 +72,24 @@ cases:
     ).toThrow(/at least one scorer/);
   });
 
+  it.each([Number.POSITIVE_INFINITY, Number.NEGATIVE_INFINITY, Number.NaN])(
+    "rejects non-finite scorer weight (%s)",
+    (weight) => {
+      expect(() =>
+        validateSuite({
+          name: "d",
+          cases: [
+            {
+              id: "x",
+              input: { prompt: "a" },
+              scorers: [{ type: "regex", weight }],
+            },
+          ],
+        }),
+      ).toThrow(/scorers\[0\]\.weight/);
+    },
+  );
+
   it("rejects an out-of-range threshold", () => {
     expect(() =>
       validateSuite({