diff --git a/crates/weksa/tests/golf_loop.rs b/crates/weksa/tests/golf_loop.rs
index e52da20..ae0b7fe 100644
--- a/crates/weksa/tests/golf_loop.rs
+++ b/crates/weksa/tests/golf_loop.rs
@@ -2952,6 +2952,8 @@ fn admit_refusals_are_counted_by_rule_and_printed_with_the_label() {
 struct Reciter {
     corpus: weksa::store::CorpusStore,
     answer: fn(&str) -> String,
+    /// An item whose text holds this gets an answer file that is not UTF-8.
+    unreadable: Option<&'static str>,
     seen: Vec<String>,
 }
 
@@ -2963,6 +2965,9 @@ impl ModelPort for Reciter {
         self.seen.push(prompt.text().to_string());
         let key = &prompt.item_keys()[0];
         let item = self.corpus.get(key).unwrap().unwrap();
+        if self.unreadable.is_some_and(|t| item.text.contains(t)) {
+            return Err(PortError::Io(std::io::ErrorKind::InvalidData));
+        }
         Ok((self.answer)(&item.text))
     }
 }
@@ -2977,6 +2982,7 @@ fn reciter(dao: &Dao, answer: fn(&str) -> String) -> Reciter {
     Reciter {
         corpus: weksa::store::CorpusStore::open(&dao.corpus).unwrap(),
         answer,
+        unreadable: None,
         seen: vec![],
     }
 }
@@ -3039,3 +3045,40 @@ fn the_published_round_schema_does_not_require_a_field_older_records_lack() {
     assert!(!required.iter().any(|r| r == "admit_rules"), "{required:?}");
     assert!(schema["properties"]["admit_rules"].is_object());
 }
+
+#[test]
+fn a_recall_mean_is_over_every_probe_an_unreadable_answer_counts_0_and_only_live_public_domain_items_are_probed() {
+    use weksa::corpus::Source;
+    use weksa::run::RecallOutcome;
+    let dao = dao_over(|corpus, entities| {
+        let entities = weksa::EntityStore::open(entities).unwrap();
+        let mut store = weksa::CorpusStore::open(corpus).unwrap();
+        // The same words under other sources: not public domain, not probed.
+        let mut written = store.get("item:daodejing:2").unwrap().unwrap();
+        written.id = "item:written:1".into();
+        written.text = "A line of some other source with words enough to split.".into();
+        written.names = vec![];
+        written.prior_turns = vec![];
+        written.source = Source::OperatorWritten;
+        store.add(written, &entities).unwrap();
+        store.withdraw("item:daodejing:3").unwrap();
+    });
+    let both = |dao: &Dao, unreadable: Option<&'static str>| {
+        let mut m = reciter(dao, second_half);
+        m.unreadable = unreadable;
+        let RecallOutcome::Read(r) = dao.run.recall(&mut m).unwrap() else {
+            panic!("answered");
+        };
+        r
+    };
+    let full = both(&dao, None);
+    assert_eq!(
+        (full.n, full.answered),
+        (2, 2),
+        "neither the written item nor the withdrawn one is probed"
+    );
+    // One of two unreadable: the mean falls to a half.
+    let part = both(&dao, Some("Heaven is long-enduring"));
+    assert_eq!((part.n, part.answered), (2, 1));
+    assert!((part.chrf - full.chrf / 2.0).abs() < 1e-9, "{}", part.chrf);
+}