v0.9 streaming parser suite

Implements the full incremental A2UI v0.9 streaming parser suite in
Kotlin, achieving SDK parity. Automatically incorporates critical
subsequent fixes for robust real-time topology parsing and relative
bindings.

Port of Python SDK commit 8ba982a

Author: jgindin

agent_sdks/kotlin/src/main/kotlin/com/google/a2ui/a2a/A2aHandler.kt

@@ -18,6 +18,7 @@ package com.google.a2ui.a2a
 
 import com.google.a2ui.core.parser.hasA2uiParts
 import com.google.a2ui.core.parser.parseResponseToParts
+import com.google.a2ui.core.schema.A2uiConstants
 import com.google.adk.agents.RunConfig
 import com.google.adk.events.Event
 import com.google.adk.runner.Runner
@@ -41,6 +42,7 @@ class A2aHandler(private val runner: Runner) {
     agentName: String,
     serverUrl: String,
     supportedCatalogIds: List<String> = emptyList(),
+    version: String = A2uiConstants.VERSION_0_9,
   ): Map<String, Any> {
     return mapOf(
       "name" to agentName,
@@ -52,7 +54,7 @@ class A2aHandler(private val runner: Runner) {
           "extensions" to
             listOf(
               mapOf(
-                "uri" to A2uiA2a.A2UI_EXTENSION_URI,
+                "uri" to "${A2uiA2a.A2UI_EXTENSION_BASE_URI}$version",
                 "params" to mapOf("supportedCatalogIds" to supportedCatalogIds),
               )
             ),

agent_sdks/kotlin/src/main/kotlin/com/google/a2ui/a2a/A2uiA2a.kt

@@ -24,7 +24,7 @@ import kotlinx.serialization.json.JsonElement
 
 /** A2A protocol helpers for A2UI integration. */
 object A2uiA2a {
-  const val A2UI_EXTENSION_URI = "https://a2ui.org/a2a-extension/a2ui/v0.8"
+  const val A2UI_EXTENSION_BASE_URI = "https://a2ui.org/a2a-extension/a2ui/v"
   const val MIME_TYPE_KEY = "mimeType"
   const val A2UI_MIME_TYPE = "application/json+a2ui"
 
@@ -42,12 +42,13 @@ object A2uiA2a {
 
   /** Creates the A2UI AgentExtension configuration. */
   fun getA2uiAgentExtension(
+    version: String,
     acceptsInlineCatalogs: Boolean = false,
     supportedCatalogIds: List<String> = emptyList(),
   ): AgentExtension {
     val params = mutableMapOf<String, Any>()
     if (acceptsInlineCatalogs) {
-      params[A2uiConstants.INLINE_CATALOGS_KEY] = true
+      params[A2uiConstants.ACCEPTS_INLINE_CATALOGS_KEY] = true
     }
     if (supportedCatalogIds.isNotEmpty()) {
       params[A2uiConstants.SUPPORTED_CATALOG_IDS_KEY] = supportedCatalogIds
@@ -56,27 +57,70 @@ object A2uiA2a {
     val isSupportRequired = false
     return AgentExtension(
       "Provides agent driven UI using the A2UI JSON format.",
-      params,
+      if (params.isEmpty()) null else params,
       isSupportRequired,
-      A2UI_EXTENSION_URI,
+      "$A2UI_EXTENSION_BASE_URI$version",
     )
   }
 
+  /**
+   * Selects the newest A2UI extension URI from the matched extensions.
+   *
+   * @param requestedExtensions List of extension URIs requested by the client.
+   * @param advertisedExtensions List of extension URIs advertised by the agent.
+   * @return The newest overlapping A2UI extension URI, or null if none match.
+   */
+  fun selectNewestA2uiExtension(
+    requestedExtensions: List<String>,
+    advertisedExtensions: List<String>,
+  ): String? {
+    val baseUri = A2UI_EXTENSION_BASE_URI
+    val matched =
+      requestedExtensions.intersect(advertisedExtensions.toSet()).filter { it.startsWith(baseUri) }
+
+    if (matched.isEmpty()) return null
+
+    return matched.maxWithOrNull(
+      Comparator { uri1, uri2 ->
+        val v1 = uri1.removePrefix(baseUri)
+        val v2 = uri2.removePrefix(baseUri)
+        compareVersions(v1, v2)
+      }
+    )
+  }
+
+  private fun compareVersions(v1: String, v2: String): Int {
+    val parts1 = v1.split('.').map { it.toIntOrNull() ?: 0 }
+    val parts2 = v2.split('.').map { it.toIntOrNull() ?: 0 }
+    val length = maxOf(parts1.size, parts2.size)
+    for (i in 0 until length) {
+      val p1 = parts1.getOrElse(i) { 0 }
+      val p2 = parts2.getOrElse(i) { 0 }
+      if (p1 != p2) {
+        return p1.compareTo(p2)
+      }
+    }
+    return 0
+  }
+
   /**
    * Activates the A2UI extension if requested in the context.
    *
    * @param requestedExtensions List of extension URIs requested by the client.
+   * @param advertisedExtensions List of extension URIs advertised by the agent.
    * @param addActivatedExtension Callback to register an activated extension.
-   * @return True if A2UI was activated, false otherwise.
+   * @return The version string of the activated A2UI extension, or null if not activated.
    */
   fun tryActivateA2uiExtension(
     requestedExtensions: List<String>,
+    advertisedExtensions: List<String>,
     addActivatedExtension: (String) -> Unit,
-  ): Boolean {
-    if (A2UI_EXTENSION_URI in requestedExtensions) {
-      addActivatedExtension(A2UI_EXTENSION_URI)
-      return true
+  ): String? {
+    val selectedUri = selectNewestA2uiExtension(requestedExtensions, advertisedExtensions)
+    if (selectedUri != null) {
+      addActivatedExtension(selectedUri)
+      return selectedUri.removePrefix(A2UI_EXTENSION_BASE_URI)
     }
-    return false
+    return null
   }
 }