fix(sanitize): keep a short redacted value idempotent

crates/tinyinference-core/src/sanitize.rs

@@ -336,8 +336,9 @@ pub fn scrub_credentials(input: &str) -> String {
             return full_match.to_string();
         }
         // Already redacted: an unquoted value stops at `*`, so a second pass
-        // would match the kept prefix and stack another marker. Leave it.
-        if rest.starts_with("*[REDACTED]") {
+        // would match the kept prefix and stack another marker. A short
+        // quoted value was replaced whole, so its value is the marker.
+        if rest.starts_with("*[REDACTED]") || value.as_str().starts_with("*[REDACTED]") {
             return full_match.to_string();
         }
         // Replace only the value span. Rebuilding the key from captures used

crates/tinyinference-core/src/sanitize_tests.rs

@@ -137,6 +137,15 @@ fn scrub_credentials_is_idempotent() {
     assert_eq!(scrub_credentials(&once), once);
 }
 
+// A second pass must not stack a marker on a short value that the first
+// pass replaced whole (`"ab"` -> `"*[REDACTED]"`).
+#[test]
+fn short_quoted_value_scrubs_idempotently() {
+    let once = scrub_credentials(r#"{"token":"ab"}"#);
+    assert_eq!(once, r#"{"token":"*[REDACTED]"}"#);
+    assert_eq!(scrub_credentials(&once), once);
+}
+
 #[test]
 fn scrub_credentials_empty_input() {
     assert_eq!(scrub_credentials(""), "");