diff --git a/crates/model-connector/src/contract.rs b/crates/model-connector/src/contract.rs
index bb6459e..3062fe4 100644
--- a/crates/model-connector/src/contract.rs
+++ b/crates/model-connector/src/contract.rs
@@ -540,8 +540,9 @@ pub enum Refusal {
     Indeterminate,
     ReplayConflict,
     Malformed,
-    /// A `ReasoningState` of another provider sits in the in-flight tool
-    /// exchange, where dropping it would break the provider's own rules.
+    // A `ReasoningState` of another provider sits in the in-flight tool
+    // exchange, where dropping it would break the provider's own rules. A plain
+    // comment: a doc comment would split the published schema into a union.
     ForeignReasoningState,
 }
 
diff --git a/crates/model-connector/tests/published_schemas.rs b/crates/model-connector/tests/published_schemas.rs
index 4634280..8a1bf47 100644
--- a/crates/model-connector/tests/published_schemas.rs
+++ b/crates/model-connector/tests/published_schemas.rs
@@ -98,3 +98,18 @@ fn the_published_ciphertext_is_what_the_wire_sends() {
         .unwrap();
     assert!(matches!(wire, rmpv::Value::Binary(bytes) if bytes.len() == 40));
 }
+
+#[test]
+fn the_refusal_schema_is_one_flat_string_enum() {
+    let schema: serde_json::Value = serde_json::from_str(&render::<Refusal>()).unwrap();
+    assert!(schema.get("oneOf").is_none(), "{schema}");
+    assert_eq!(schema["type"], "string");
+    let variants: Vec<&str> = schema["enum"]
+        .as_array()
+        .expect("a closed set of strings")
+        .iter()
+        .map(|value| value.as_str().unwrap())
+        .collect();
+    assert_eq!(variants.len(), 12);
+    assert!(variants.contains(&"ForeignReasoningState"));
+}
diff --git a/schemas/transport_result.json b/schemas/transport_result.json
index 25d97ab..acdf6b6 100644
--- a/schemas/transport_result.json
+++ b/schemas/transport_result.json
@@ -38,28 +38,20 @@
       ]
     },
     "Refusal": {
-      "oneOf": [
-        {
-          "type": "string",
-          "enum": [
-            "Expired",
-            "IdentitySubstitution",
-            "ProviderDigestSubstitution",
-            "ModelNotAllowed",
-            "OutputBound",
-            "PayloadBound",
-            "Capacity",
-            "InFlight",
-            "Indeterminate",
-            "ReplayConflict",
-            "Malformed"
-          ]
-        },
-        {
-          "description": "A `ReasoningState` of another provider sits in the in-flight tool\nexchange, where dropping it would break the provider's own rules.",
-          "type": "string",
-          "const": "ForeignReasoningState"
-        }
+      "type": "string",
+      "enum": [
+        "Expired",
+        "IdentitySubstitution",
+        "ProviderDigestSubstitution",
+        "ModelNotAllowed",
+        "OutputBound",
+        "PayloadBound",
+        "Capacity",
+        "InFlight",
+        "Indeterminate",
+        "ReplayConflict",
+        "Malformed",
+        "ForeignReasoningState"
       ]
     },
     "StopReason": {