diff --git a/crates/coven-threads-core/src/identity_invariants.rs b/crates/coven-threads-core/src/identity_invariants.rs
index f99d888..ae701f8 100644
--- a/crates/coven-threads-core/src/identity_invariants.rs
+++ b/crates/coven-threads-core/src/identity_invariants.rs
@@ -388,8 +388,15 @@ fn parse_identity_declaration(value: &str) -> Result<IdentityInvariantDeclaratio
         ),
         (None, None) => return Err("expected `==` or `includes` operator".into()),
     };
-    let fact = IdentityFact::from_declaration_name(left.trim())
-        .ok_or_else(|| format!("unsupported identity fact {:?}", left.trim()))?;
+    // Never echo left-of-operator text: a reversed declaration (e.g.
+    // `'<person>' == familiar.person`) would carry principal-adjacent values
+    // into migration reports and stdout. Name the expected grammar instead.
+    let fact = IdentityFact::from_declaration_name(left.trim()).ok_or_else(|| {
+        "unsupported identity fact left of operator; expected one of: \
+         familiar.name, familiar.person, familiar.pronouns, familiar.purpose, \
+         familiar.coven"
+            .to_string()
+    })?;
     let right = right.trim();
     if right.is_empty() {
         return Err("expected value must not be empty".into());
@@ -1045,6 +1052,22 @@ mod tests {
         assert!(errors.iter().any(|error| error.contains("Name")));
     }
 
+    #[test]
+    fn unsupported_fact_rejection_never_echoes_left_of_operator_text() {
+        // Reversed declaration: principal-adjacent text sits left of the
+        // operator. The rejection must name the grammar, never the text.
+        let errors = IdentityInvariantSet::compile([
+            r#"'Val Alexander' == familiar.person"#,
+            r#"familiar.name == "Nova""#,
+            r#"familiar.person == "Val""#,
+        ])
+        .unwrap_err();
+        assert_eq!(errors.len(), 1);
+        assert!(errors[0].starts_with("invariant[0]: unsupported identity fact"));
+        assert!(errors[0].contains("familiar.pronouns"));
+        assert!(!errors[0].contains("Val Alexander"));
+    }
+
     #[test]
     fn compiler_uses_the_first_declared_operator_not_rhs_text() {
         let invariants = IdentityInvariantSet::compile([