feat: switch chat bridge to streaming for full A2UI content capture

Blocking mode only returns the final task state, missing intermediate
A2UI response content from working status-update events. Streaming
captures all events and aggregates parts into the response.

packages/a2a-server/src/chat-bridge/a2a-bridge-client.ts

@@ -164,8 +164,9 @@ export class A2ABridgeClient {
   }
 
   /**
-   * Sends a text message to the A2A server.
-   * Includes A2UI extension metadata so the server enables A2UI mode.
+   * Sends a text message to the A2A server using streaming.
+   * Uses streaming to capture all intermediate A2UI content from status-update
+   * events, since the final task state may not contain the response content.
    */
   async sendMessage(
     text: string,
@@ -188,12 +189,9 @@ export class A2ABridgeClient {
           extensions: [A2UI_EXTENSION_URI],
         },
       },
-      configuration: {
-        blocking: true,
-      },
     };
 
-    return this.client.sendMessage(params);
+    return this.collectStreamResponse(params);
   }
 
   /**
@@ -244,11 +242,88 @@ export class A2ABridgeClient {
           extensions: [A2UI_EXTENSION_URI],
         },
       },
-      configuration: {
-        blocking: true,
-      },
     };
 
-    return this.client.sendMessage(params);
+    return this.collectStreamResponse(params);
+  }
+
+  /**
+   * Sends a message via streaming and collects all A2UI parts from intermediate
+   * status-update events. The A2A server sends response content in "working"
+   * status updates, while the final event (e.g. "input-required") may be empty.
+   * Streaming captures everything.
+   */
+  private async collectStreamResponse(
+    params: MessageSendParams,
+  ): Promise<A2AResponse> {
+    if (!this.client) {
+      throw new Error('A2A client not initialized.');
+    }
+
+    const stream = this.client.sendMessageStream(params);
+    const collectedParts: Part[] = [];
+    let latestTaskId: string | undefined;
+    let latestContextId: string | undefined;
+    let latestState = 'working';
+
+    for await (const event of stream) {
+      switch (event.kind) {
+        case 'status-update':
+          latestTaskId = event.taskId;
+          latestContextId = event.contextId;
+          latestState = event.status.state;
+          if (event.status.message?.parts) {
+            collectedParts.push(...event.status.message.parts);
+          }
+          break;
+        case 'artifact-update':
+          latestTaskId = event.taskId;
+          latestContextId = event.contextId;
+          if (event.artifact?.parts) {
+            collectedParts.push(...event.artifact.parts);
+          }
+          break;
+        case 'task':
+          // Full task response from stream - augment with collected parts
+          if (
+            collectedParts.length > 0 &&
+            event.status &&
+            !event.status.message?.parts?.length
+          ) {
+            event.status.message = {
+              kind: 'message',
+              role: 'agent',
+              messageId: uuidv4(),
+              parts: collectedParts,
+            };
+          }
+          return event;
+        case 'message':
+          // Full message response from stream - augment with collected parts
+          if (collectedParts.length > 0 && !event.parts?.length) {
+            event.parts = collectedParts;
+          }
+          return event;
+        default:
+          break;
+      }
+    }
+
+    // Stream ended with only status-update/artifact-update events.
+    // Build a synthetic Message with all collected parts.
+    logger.info(
+      `[ChatBridge] Stream completed: taskId=${latestTaskId}, state=${latestState}, parts=${collectedParts.length}`,
+    );
+
+    // Return as a Message containing all collected A2UI parts
+    const response: Message = {
+      kind: 'message',
+      role: 'agent',
+      messageId: uuidv4(),
+      parts: collectedParts,
+      contextId: latestContextId,
+      taskId: latestTaskId,
+    };
+    return response;
   }
 }