Update v0.9 Spec: Add borderless Button variant alongside Primary

specification/v0_9/docs/a2ui_protocol.md

@@ -215,7 +215,7 @@ The following example demonstrates a complete interaction to render a Contact Fo
 
 ```jsonl
 {"createSurface":{"surfaceId":"contact_form_1","catalogId":"https://a2ui.dev/specification/v0_9/standard_catalog.json"}}
-{"updateComponents":{"surfaceId":"contact_form_1","components":[{"id":"root","component":"Card","child":"form_container"},{"id":"form_container","component":"Column","children":["header_row","name_row","email_group","phone_group","pref_group","divider_1","newsletter_checkbox","submit_button"],"justify":"start","align":"stretch"},{"id":"header_row","component":"Row","children":["header_icon","header_text"],"align":"center"},{"id":"header_icon","component":"Icon","name":"mail"},{"id":"header_text","component":"Text","text":"# Contact Us","variant":"h2"},{"id":"name_row","component":"Row","children":["first_name_group","last_name_group"],"justify":"spaceBetween"},{"id":"first_name_group","component":"Column","children":["first_name_label","first_name_field"],"weight":1},{"id":"first_name_label","component":"Text","text":"First Name","variant":"caption"},{"id":"first_name_field","component":"TextField","label":"First Name","value":{"path":"/contact/firstName"},"variant":"shortText"},{"id":"last_name_group","component":"Column","children":["last_name_label","last_name_field"],"weight":1},{"id":"last_name_label","component":"Text","text":"Last Name","variant":"caption"},{"id":"last_name_field","component":"TextField","label":"Last Name","value":{"path":"/contact/lastName"},"variant":"shortText"},{"id":"email_group","component":"Column","children":["email_label","email_field"]},{"id":"email_label","component":"Text","text":"Email Address","variant":"caption"},{"id":"email_field","component":"TextField","label":"Email","value":{"path":"/contact/email"},"variant":"shortText","checks":[{"call":"required","message":"Email is required."},{"call":"email","message":"Please enter a valid email address."}]},{"id":"phone_group","component":"Column","children":["phone_label","phone_field"]},{"id":"phone_label","component":"Text","text":"Phone Number","variant":"caption"},{"id":"phone_field","component":"TextField","label":"Phone","value":{"path":"/contact/phone"},"variant":"shortText","checks":[{"call":"regex","args":{"pattern":"^\\d{10}$"},"message":"Phone number must be 10 digits."}]},{"id":"pref_group","component":"Column","children":["pref_label","pref_picker"]},{"id":"pref_label","component":"Text","text":"Preferred Contact Method","variant":"caption"},{"id":"pref_picker","component":"ChoicePicker","variant":"mutuallyExclusive","options":[{"label":"Email","value":"email"},{"label":"Phone","value":"phone"},{"label":"SMS","value":"sms"}],"value":{"path":"/contact/preference"}},{"id":"divider_1","component":"Divider","axis":"horizontal"},{"id":"newsletter_checkbox","component":"CheckBox","label":"Subscribe to our newsletter","value":{"path":"/contact/subscribe"}},{"id":"submit_button_label","component":"Text","text":"Send Message"},{"id":"submit_button","component":"Button","child":"submit_button_label","primary":true,"action":{"name":"submitContactForm","context":{"formId":"contact_form_1","clientTime":{"call":"now","returnType":"string"},"isNewsletterSubscribed":{"path":"/contact/subscribe"}}}}]}}
+{"updateComponents":{"surfaceId":"contact_form_1","components":[{"id":"root","component":"Card","child":"form_container"},{"id":"form_container","component":"Column","children":["header_row","name_row","email_group","phone_group","pref_group","divider_1","newsletter_checkbox","submit_button"],"justify":"start","align":"stretch"},{"id":"header_row","component":"Row","children":["header_icon","header_text"],"align":"center"},{"id":"header_icon","component":"Icon","name":"mail"},{"id":"header_text","component":"Text","text":"# Contact Us","variant":"h2"},{"id":"name_row","component":"Row","children":["first_name_group","last_name_group"],"justify":"spaceBetween"},{"id":"first_name_group","component":"Column","children":["first_name_label","first_name_field"],"weight":1},{"id":"first_name_label","component":"Text","text":"First Name","variant":"caption"},{"id":"first_name_field","component":"TextField","label":"First Name","value":{"path":"/contact/firstName"},"variant":"shortText"},{"id":"last_name_group","component":"Column","children":["last_name_label","last_name_field"],"weight":1},{"id":"last_name_label","component":"Text","text":"Last Name","variant":"caption"},{"id":"last_name_field","component":"TextField","label":"Last Name","value":{"path":"/contact/lastName"},"variant":"shortText"},{"id":"email_group","component":"Column","children":["email_label","email_field"]},{"id":"email_label","component":"Text","text":"Email Address","variant":"caption"},{"id":"email_field","component":"TextField","label":"Email","value":{"path":"/contact/email"},"variant":"shortText","checks":[{"call":"required","message":"Email is required."},{"call":"email","message":"Please enter a valid email address."}]},{"id":"phone_group","component":"Column","children":["phone_label","phone_field"]},{"id":"phone_label","component":"Text","text":"Phone Number","variant":"caption"},{"id":"phone_field","component":"TextField","label":"Phone","value":{"path":"/contact/phone"},"variant":"shortText","checks":[{"call":"regex","args":{"pattern":"^\\d{10}$"},"message":"Phone number must be 10 digits."}]},{"id":"pref_group","component":"Column","children":["pref_label","pref_picker"]},{"id":"pref_label","component":"Text","text":"Preferred Contact Method","variant":"caption"},{"id":"pref_picker","component":"ChoicePicker","variant":"mutuallyExclusive","options":[{"label":"Email","value":"email"},{"label":"Phone","value":"phone"},{"label":"SMS","value":"sms"}],"value":{"path":"/contact/preference"}},{"id":"divider_1","component":"Divider","axis":"horizontal"},{"id":"newsletter_checkbox","component":"CheckBox","label":"Subscribe to our newsletter","value":{"path":"/contact/subscribe"}},{"id":"submit_button_label","component":"Text","text":"Send Message"},{"id":"submit_button","component":"Button","child":"submit_button_label","variant":"primary","action":{"name":"submitContactForm","context":{"formId":"contact_form_1","clientTime":{"call":"now","returnType":"string"},"isNewsletterSubscribed":{"path":"/contact/subscribe"}}}}]}}
 {"updateDataModel":{"surfaceId":"contact_form_1","path":"/contact","value":{"firstName":"John","lastName":"Doe"}}}
 {"deleteSurface":{"surfaceId":"contact_form_1"}}
 ```
@@ -561,7 +561,7 @@ The [`standard_catalog.json`] provides the baseline set of components and functi
 | **Tabs**          | A set of tabs, each with a title and child component.                                  |
 | **Divider**       | A horizontal or vertical dividing line.                                                |
 | **Modal**         | A dialog that appears over the main content triggered by a button in the main content. |
-| **Button**        | A clickable button that dispatches an action.                                          |
+| **Button**        | A clickable button that dispatches an action. Supports 'primary' and 'borderless' variants. |
 | **CheckBox**      | A checkbox with a label and a boolean value.                                           |
 | **TextField**     | A field for user text input.                                                           |
 | **DateTimeInput** | An input for date and/or time.                                                         |

specification/v0_9/docs/evolution_guide.md

@@ -11,18 +11,19 @@ Version 0.9 represents a fundamental philosophical shift from "Structured Output
 
 ### Summary Table
 
-| Feature                  | v0.8.1                                   | v0.9                                                   |
-| :----------------------- | :--------------------------------------- | :------------------------------------------------------|
-| **Philosophy**           | Structured Output / Function Calling     | Prompt-First / In-Context Schema                       |
-| **Message Types**        | `beginRendering`, `surfaceUpdate`, ...   | `createSurface`, `updateComponents`, ...               |
-| **Surface Creation**     | Explicit `beginRendering`                | Explicit `createSurface`                               |
-| **Component Type**       | Key-based wrapper (`{"Text": ...}`)      | Property-based discriminator (`"component": "Text"`)  |
-| **Data Model Update**    | Array of Key-Value Pairs                 | Standard JSON Object                                   |
-| **Data Binding**         | `dataBinding` / `literalString`          | `path` / Native JSON types                             |
-| **Button Context**       | Array of Key-Value pairs                 | Standard JSON Object                                   |
-| **Catalog**              | Separate component and function catalogs | Unified Catalog (`standard_catalog.json`)              |
-| **Auxiliary Rules**      | N/A                                      | `standard_catalog_rules.txt`                           |
-| **Validation**           | Basic Schema                             | Strict `ValidationFailed` feedback loop                |
+| Feature                  | v0.8.1                                   | v0.9                                                 |
+| :----------------------- | :--------------------------------------- | :--------------------------------------------------- |
+| **Philosophy**           | Structured Output / Function Calling     | Prompt-First / In-Context Schema                     |
+| **Message Types**        | `beginRendering`, `surfaceUpdate`, ...   | `createSurface`, `updateComponents`, ...             |
+| **Surface Creation**     | Explicit `beginRendering`                | Explicit `createSurface`                             |
+| **Component Type**       | Key-based wrapper (`{"Text": ...}`)      | Property-based discriminator (`"component": "Text"`) |
+| **Data Model Update**    | Array of Key-Value Pairs                 | Standard JSON Object                                 |
+| **Data Binding**         | `dataBinding` / `literalString`          | `path` / Native JSON types                           |
+| **Button Context**       | Array of Key-Value pairs                 | Standard JSON Object                                 |
+| **Button Variant**       | Boolean (`primary: true`)                | Enum (`variant: "primary"`)                          |
+| **Catalog**              | Separate component and function catalogs | Unified Catalog (`standard_catalog.json`)            |
+| **Auxiliary Rules**      | N/A                                      | `standard_catalog_rules.txt`                         |
+| **Validation**           | Basic Schema                             | Strict `ValidationFailed` feedback loop              |
 | **Data Synchronization** | Implicit                                 | Explicit Client->Server data syncing (`attachDataModel`) |
 
 ## 2. Architectural & Schema Changes
@@ -256,7 +257,19 @@ Specifying an unknown surfaceId will cause an error. It is recommended that clie
 - **Standard Map**: `context: { "id": "123" }`
 - **Reason**: Token efficiency. LLMs understand JSON objects as maps natively.
 
-### 6.2. TextField
+### 6.2. Button Variant
+
+**v0.8.1:**
+
+- **Boolean**: `primary: true` or `primary: false`.
+- **Limited**: Only two styles were explicitly supported.
+
+**v0.9:**
+
+- **Enum**: `variant: "primary"` or `variant: "borderless"`.
+- **Reason**: More flexible and consistent with other components (like `Text` and `Image`) that use `variant` for styling hints. 'borderless' provides a standard way to represent clickable text or icons without a button-like frame.
+
+### 6.3. TextField
 
 **v0.8.1:**
 
@@ -269,7 +282,7 @@ Specifying an unknown surfaceId will cause an error. It is recommended that clie
 - Validation: **`checks`** (generic list of function calls).
 - **Reason**: Consistency with `Text` and `Image` components which already used `variant`. Validation is now more flexible and reusable. Also, `text` was renamed to **`value`** to match other input components.
 
-### 6.3. ChoicePicker (vs MultipleChoice)
+### 6.4. ChoicePicker (vs MultipleChoice)
 
 **v0.8.1:**
 
@@ -282,7 +295,7 @@ Specifying an unknown surfaceId will cause an error. It is recommended that clie
 - Properties: **`value`** (array), **`variant`** (enum: `multipleSelection`, `mutuallyExclusive`). The `maxAllowedSelections` property was removed.
 - **Reason**: `ChoicePicker` is a more generic name that covers both radio buttons (mutually exclusive) and checkboxes (multiple selection). The `variant` controls the behavior, simplifying the component surface area.
 
-### 6.4. Slider
+### 6.5. Slider
 
 **v0.8.1:**
 

specification/v0_9/json/standard_catalog.json

@@ -415,9 +415,10 @@
               "type": "string",
               "description": "The ID of the child component. Use a 'Text' component for a labeled button. Only use an 'Icon' if the requirements explicitly ask for an icon-only button. Do NOT define the child component inline."
             },
-            "primary": {
-              "type": "boolean",
-              "description": "Indicates if this button should be styled as the primary action."
+            "variant": {
+              "type": "string",
+              "description": "A hint for the button style. If omitted, a default button style is used. 'primary' indicates this is the main call-to-action button. 'borderless' means the button has no visual border or background, making its child content appear like a clickable link.",
+              "enum": ["primary", "borderless"]
             },
             "action": {
               "type": "object",

specification/v0_9/test/cases/button_checks.json

@@ -113,6 +113,63 @@
           ]
         }
       }
+    },
+    {
+      "description": "Button with variant 'primary'",
+      "valid": true,
+      "data": {
+        "updateComponents": {
+          "surfaceId": "test_surface",
+          "components": [
+            {
+              "id": "btn_primary",
+              "component": "Button",
+              "child": "txt_primary",
+              "action": { "name": "submit" },
+              "variant": "primary"
+            },
+            { "id": "txt_primary", "component": "Text", "text": "Submit" }
+          ]
+        }
+      }
+    },
+    {
+      "description": "Button with variant 'borderless'",
+      "valid": true,
+      "data": {
+        "updateComponents": {
+          "surfaceId": "test_surface",
+          "components": [
+            {
+              "id": "btn_borderless",
+              "component": "Button",
+              "child": "txt_borderless",
+              "action": { "name": "cancel" },
+              "variant": "borderless"
+            },
+            { "id": "txt_borderless", "component": "Text", "text": "Cancel" }
+          ]
+        }
+      }
+    },
+    {
+      "description": "Button with deprecated 'primary' property (should fail)",
+      "valid": false,
+      "data": {
+        "updateComponents": {
+          "surfaceId": "test_surface",
+          "components": [
+            {
+              "id": "btn_dep",
+              "component": "Button",
+              "child": "txt_dep",
+              "action": { "name": "submit" },
+              "primary": true
+            },
+            { "id": "txt_dep", "component": "Text", "text": "Submit" }
+          ]
+        }
+      }
     }
   ]
 }