Revert "fix: multi message in single stream support"

This reverts commit 49a53f2.

Author: callycodes

packages/ai/src/ui/chat.ts

@@ -551,48 +551,15 @@ export abstract class AbstractChat<UI_MESSAGE extends UIMessage> {
               // streaming is set on first write (before it should be "submitted")
               this.setStatus({ status: 'streaming' });
 
-              // Handle multiple messages in the queue
-              if (activeResponse.state.messageQueue && activeResponse.state.messageQueue.length > 0) {
-                // Add all queued messages to the chat
-                for (const queuedMessage of activeResponse.state.messageQueue) {
-                  const existingMessageIndex = this.state.messages.findIndex(
-                    msg => msg.id === queuedMessage.id
-                  );
-                  
-                  if (existingMessageIndex >= 0) {
-                    // Update existing message
-                    this.state.replaceMessage(existingMessageIndex, queuedMessage);
-                  } else {
-                    // Add new message
-                    this.state.pushMessage(queuedMessage);
-                  }
-                }
-                // Clear the queue after processing
-                activeResponse.state.messageQueue = [];
-              }
-
-              // Handle the current message
               const replaceLastMessage =
                 activeResponse.state.message.id === this.lastMessage?.id;
 
-              const existingMessageIndex = this.state.messages.findIndex(
-                msg => msg.id === activeResponse.state.message.id
-              );
-
-              if (existingMessageIndex >= 0) {
-                // Update existing message
-                this.state.replaceMessage(
-                  existingMessageIndex,
-                  activeResponse.state.message,
-                );
-              } else if (replaceLastMessage) {
-                // Replace last message for backward compatibility
+              if (replaceLastMessage) {
                 this.state.replaceMessage(
                   this.state.messages.length - 1,
                   activeResponse.state.message,
                 );
               } else {
-                // Add new message
                 this.state.pushMessage(activeResponse.state.message);
               }
             },
@@ -616,22 +583,6 @@ export abstract class AbstractChat<UI_MESSAGE extends UIMessage> {
         },
       });
 
-      // Process any remaining messages in the queue after stream consumption
-      if (activeResponse.state.messageQueue && activeResponse.state.messageQueue.length > 0) {
-        for (const queuedMessage of activeResponse.state.messageQueue) {
-          const existingMessageIndex = this.state.messages.findIndex(
-            msg => msg.id === queuedMessage.id
-          );
-          
-          if (existingMessageIndex >= 0) {
-            this.state.replaceMessage(existingMessageIndex, queuedMessage);
-          } else {
-            this.state.pushMessage(queuedMessage);
-          }
-        }
-        activeResponse.state.messageQueue = [];
-      }
-
       this.setStatus({ status: 'ready' });
     } catch (err) {
       // Ignore abort errors as they are expected.

packages/ai/src/ui/process-ui-message-stream-multi.test.ts

@@ -38,9 +38,6 @@ export type StreamingUIMessageState<UI_MESSAGE extends UIMessage> = {
     string,
     { text: string; index: number; toolName: string; dynamic?: boolean }
   >;
-  // Support for multiple messages in a single stream
-  isFinalized?: boolean;
-  messageQueue?: UI_MESSAGE[];
 };
 
 export function createStreamingUIMessageState<UI_MESSAGE extends UIMessage>({
@@ -66,8 +63,6 @@ export function createStreamingUIMessageState<UI_MESSAGE extends UIMessage>({
     activeTextParts: {},
     activeReasoningParts: {},
     partialToolCalls: {},
-    isFinalized: false,
-    messageQueue: [],
   };
 }
 
@@ -605,38 +600,12 @@ export function processUIMessageStream<UI_MESSAGE extends UIMessage>({
             }
 
             case 'start': {
-              // Handle multiple messages in a single stream
               if (chunk.messageId != null) {
-                // If current message is finalized, save it and create a new one
-                if (state.isFinalized && state.message.parts.length > 0) {
-                  // Save the current message to the queue
-                  state.messageQueue!.push(state.message);
-                  
-                  // Create a new message for the new messageId
-                  state.message = {
-                    id: chunk.messageId,
-                    metadata: chunk.messageMetadata as InferUIMessageMetadata<UI_MESSAGE>,
-                    role: 'assistant',
-                    parts: [] as UIMessagePart<
-                      InferUIMessageData<UI_MESSAGE>,
-                      InferUIMessageTools<UI_MESSAGE>
-                    >[],
-                  } as UI_MESSAGE;
-                  
-                  // Reset state for the new message
-                  state.activeTextParts = {};
-                  state.activeReasoningParts = {};
-                  state.partialToolCalls = {};
-                  state.isFinalized = false;
-                } else {
-                  // First message or updating existing message
-                  state.message.id = chunk.messageId;
-                  await updateMessageMetadata(chunk.messageMetadata);
-                }
-              } else {
-                await updateMessageMetadata(chunk.messageMetadata);
+                state.message.id = chunk.messageId;
               }
 
+              await updateMessageMetadata(chunk.messageMetadata);
+
               if (chunk.messageId != null || chunk.messageMetadata != null) {
                 write();
               }
@@ -648,8 +617,6 @@ export function processUIMessageStream<UI_MESSAGE extends UIMessage>({
               if (chunk.messageMetadata != null) {
                 write();
               }
-              // Mark the current message as finalized for multi-message support
-              state.isFinalized = true;
               break;
             }