diff --git a/apps/web/src/schemas/__tests__/validation.property.test.ts b/apps/web/src/schemas/__tests__/validation.property.test.ts
index 06cef929d..44cc99a56 100644
--- a/apps/web/src/schemas/__tests__/validation.property.test.ts
+++ b/apps/web/src/schemas/__tests__/validation.property.test.ts
@@ -68,10 +68,24 @@ function safeChatContent(min: number, max: number) {
 /** Arbitrary that generates valid UUIDs */
 const validUuid = fc.uuid();
 
-/** Arbitrary that generates valid ISO 8601 datetime strings */
-const validIsoDate = fc.date({ min: new Date('2000-01-01'), max: new Date('2099-12-31') }).map(
-  (d) => d.toISOString(),
-);
+/**
+ * Arbitrary that generates valid ISO 8601 datetime strings.
+ *
+ * `noInvalidDate: true` excludes the `new Date(NaN)` "Invalid Date"
+ * sentinel that fast-check's `fc.date()` would otherwise produce
+ * occasionally. Without it, a sporadic CI run hits
+ *   RangeError: Invalid time value
+ * inside `.toISOString()` and fails the whole property suite — a
+ * non-deterministic flake that has nothing to do with the property
+ * being asserted.
+ */
+const validIsoDate = fc
+  .date({
+    min: new Date('2000-01-01'),
+    max: new Date('2099-12-31'),
+    noInvalidDate: true,
+  })
+  .map((d) => d.toISOString());
 
 /** Arbitrary that generates valid email-shaped strings */
 const validEmail = fc