diff --git a/rust/src/generated/api_types.rs b/rust/src/generated/api_types.rs
index 0583c0922..a72b0a521 100644
--- a/rust/src/generated/api_types.rs
+++ b/rust/src/generated/api_types.rs
@@ -30406,6 +30406,8 @@ pub enum ModelPickerCategory {
     /// Powerful model category optimized for complex tasks.
     #[serde(rename = "powerful")]
     Powerful,
+    #[serde(rename = "experimental")]
+    Experimental,
     /// Unknown variant for forward compatibility.
     #[default]
     #[serde(other)]
diff --git a/rust/tests/session_test.rs b/rust/tests/session_test.rs
index 69a65a558..eddb483bc 100644
--- a/rust/tests/session_test.rs
+++ b/rust/tests/session_test.rs
@@ -14,7 +14,7 @@ use github_copilot_sdk::handler::{
 };
 use github_copilot_sdk::rpc::{
     CanvasProviderInvokeActionRequest, CanvasProviderOpenRequest, CanvasProviderOpenResult,
-    OpenCanvasInstance,
+    ModelPickerCategory, ModelsListResult, OpenCanvasInstance,
 };
 use github_copilot_sdk::session_events::{
     ManagedSettingsResolvedSource, McpOauthRequiredData, ReasoningSummary, SessionLimitsConfig,
@@ -4106,6 +4106,77 @@ async fn rpc_namespace_client_models_list_dispatches_correctly() {
     assert!(result.models.is_empty());
 }
 
+#[tokio::test]
+async fn raw_client_call_supports_supplemental_model_compatibility() {
+    let (client, mut server_read, mut server_write) = make_client();
+
+    let supplemental_call = tokio::spawn({
+        let client = client.clone();
+        async move {
+            let value = client.call("models.listSupplemental", None).await.unwrap();
+            serde_json::from_value::<ModelsListResult>(value).unwrap()
+        }
+    });
+
+    let request = read_framed(&mut server_read).await;
+    assert_eq!(request["method"], "models.listSupplemental");
+    let response = serde_json::json!({
+        "jsonrpc": "2.0",
+        "id": request["id"],
+        "result": {
+            "models": [{
+                "id": "experimental-model",
+                "name": "Experimental Model",
+                "capabilities": {},
+                "modelPickerCategory": "experimental"
+            }, {
+                "id": "future-model",
+                "name": "Future Model",
+                "capabilities": {},
+                "modelPickerCategory": "future-category"
+            }, {
+                "id": "legacy-model",
+                "name": "Legacy Model",
+                "capabilities": {}
+            }]
+        }
+    });
+    write_framed(&mut server_write, &serde_json::to_vec(&response).unwrap()).await;
+
+    let result = timeout(TIMEOUT, supplemental_call).await.unwrap().unwrap();
+    assert_eq!(
+        result.models[0].model_picker_category,
+        Some(ModelPickerCategory::Experimental)
+    );
+    assert_eq!(
+        result.models[1].model_picker_category,
+        Some(ModelPickerCategory::Unknown)
+    );
+    assert_eq!(result.models[2].model_picker_category, None);
+
+    let unavailable_call = tokio::spawn(async move {
+        client
+            .call("models.listSupplemental", None)
+            .await
+            .unwrap_err()
+    });
+
+    let request = read_framed(&mut server_read).await;
+    let response = serde_json::json!({
+        "jsonrpc": "2.0",
+        "id": request["id"],
+        "error": {
+            "code": -32601,
+            "message": "Method not found"
+        }
+    });
+    write_framed(&mut server_write, &serde_json::to_vec(&response).unwrap()).await;
+
+    let error = timeout(TIMEOUT, unavailable_call).await.unwrap().unwrap();
+    assert_eq!(error.rpc_code(), Some(-32601));
+    assert!(!error.is_transport_failure());
+}
+
 #[tokio::test]
 async fn client_stop_sends_session_destroy_for_each_active_session() {
     // One client, two registered sessions. Client::stop must send
diff --git a/scripts/codegen/rust.ts b/scripts/codegen/rust.ts
index b5235ce1e..8ef01d2aa 100644
--- a/scripts/codegen/rust.ts
+++ b/scripts/codegen/rust.ts
@@ -85,6 +85,25 @@ const STRING_NEWTYPE_OVERRIDES: Record<string, string> = {
 	requestId: "RequestId",
 };
 
+/**
+ * Keep the Rust model metadata lossless while supplemental models roll out
+ * ahead of the next published CLI schema.
+ */
+function addExperimentalModelPickerCategory(schema: ApiSchema): ApiSchema {
+	const definition = collectDefinitions(
+		schema as unknown as Record<string, unknown>,
+	).ModelPickerCategory;
+	if (!definition || typeof definition !== "object" || !Array.isArray(definition.enum)) {
+		throw new Error("ModelPickerCategory enum is missing from api.schema.json");
+	}
+
+	if (!definition.enum.includes("experimental")) {
+		definition.enum.push("experimental");
+	}
+
+	return schema;
+}
+
 // ── Naming helpers ──────────────────────────────────────────────────────────
 
 function toPascalCase(s: string): string {
@@ -2235,7 +2254,7 @@ async function generate(): Promise<void> {
 	);
 	const apiSchema = propagateInternalVisibility(
 		postProcessSchema(
-			stripBooleanLiterals(apiRaw) as JSONSchema7,
+			stripBooleanLiterals(addExperimentalModelPickerCategory(apiRaw)) as JSONSchema7,
 		),
 	) as unknown as ApiSchema;