Fix prompting and JSON parsing

Author: gspencergoog

examples/travel_app/lib/src/travel_planner_page.dart

@@ -353,11 +353,9 @@ the user can return to the main booking flow once they have done some research.
 
 ## Controlling the UI
 
-Use the provided tools to build and manage the user interface in response to the
-user's requests. To display or update a UI, you must first call the
-`surfaceUpdate` tool to define all the necessary components. After defining the
-components, you must call the `beginRendering` tool to specify the root
-component that should be displayed.
+To display or update a UI, you must output a `surfaceUpdate` message in JSONL format.
+The `surfaceUpdate` message must define all necessary components and specify the root
+component in the `components` list. The root component must have the ID "root".
 
 - Adding surfaces: Most of the time, you should only add new surfaces to the
   conversation. This is less confusing for the user, because they can easily
@@ -368,9 +366,6 @@ component that should be displayed.
   user because it avoids confusing the conversation with many versions of the
   same itinerary etc.
 
-Once you add or update a surface and are waiting for user input, the
-conversation turn is complete, and you should call the provideFinalOutput tool.
-
 If you are displaying more than one component, you should use a `Column` widget
 as the root and add the other components as children.
 

packages/genui/lib/src/model/a2ui_schemas.dart

@@ -203,8 +203,8 @@ class A2uiSchemas {
           properties: {
             'id': S.string(
               description:
-                  'The unique identifier for this component. The root component '
-                  "of the surface MUST have the id 'root'.",
+                  'The unique identifier for this component. The root '
+                  "component of the surface MUST have the id 'root'.",
             ),
             'weight': S.integer(
               description:

packages/genui/test/catalog/core_widgets/text_field_test.dart

@@ -32,10 +32,9 @@ void main() {
       SurfaceUpdate(surfaceId: surfaceId, components: components),
     );
     manager.handleMessage(const CreateSurface(surfaceId: surfaceId));
-    manager.dataModelForSurface(surfaceId).update(
-      DataPath('/myValue'),
-      'initial',
-    );
+    manager
+        .dataModelForSurface(surfaceId)
+        .update(DataPath('/myValue'), 'initial');
 
     await tester.pumpWidget(
       MaterialApp(

packages/genui_google_generative_ai/lib/src/google_generative_ai_content_generator.dart

@@ -274,7 +274,6 @@ class GoogleGenerativeAiContentGenerator implements ContentGenerator {
     final service = serviceFactory(configuration: this);
 
     try {
-
       // A local copy of the incoming messages which is updated with
       // tool results
       // as they are generated.
@@ -435,7 +434,17 @@ With functions:
 
   void _processLine(String line) {
     line = line.trim();
-    if (line.isEmpty) return;
+    if (line.isEmpty) {
+      return;
+    }
+
+    // If the line doesn't start with '{', it's not a JSONL object.
+    // We ignore it to prevent markdown artifacts or other noise from being
+    // treated as text.
+    if (!line.startsWith('{')) {
+      genUiLogger.fine('Ignored non-JSONL line: $line');
+      return;
+    }
 
     genUiLogger.fine('Processing line: $line');