fix: stabilize streamed message rendering

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/EryxAppService.ts

@@ -609,18 +609,24 @@ export class EryxAppService extends EventEmitter<AppServiceEvents> {
     sessionId: string,
     event: TurnDeltaEvent,
   ): Promise<void> {
+    if (event.content === undefined && event.contentDelta === undefined) {
+      return;
+    }
+
     const session = this.requireSession(workspace, sessionId);
     const existing = session.messages.find((message) => message.id === event.messageId);
 
     if (existing) {
-      existing.content = mergeStreamingText(existing.content, event.contentDelta);
+      existing.content =
+        event.content ?? mergeStreamingText(existing.content, event.contentDelta);
       existing.pending = true;
+      existing.authorName = event.authorName;
     } else {
       session.messages.push({
         id: event.messageId,
         role: 'assistant',
         authorName: event.authorName,
-        content: event.contentDelta,
+        content: event.content ?? event.contentDelta,
         createdAt: nowIso(),
         pending: true,
       });
@@ -636,6 +642,7 @@ export class EryxAppService extends EventEmitter<AppServiceEvents> {
       messageId: event.messageId,
       authorName: event.authorName,
       contentDelta: event.contentDelta,
+      content: event.content,
     });
   }
 
@@ -697,6 +704,7 @@ export class EryxAppService extends EventEmitter<AppServiceEvents> {
         occurredAt: nowIso(),
         messageId: message.id,
         authorName: message.authorName,
+        content: message.content,
       });
 
       this.emitCompletedActivity(sessionId, pattern, message);

src/renderer/components/ChatPane.tsx

@@ -418,7 +418,13 @@ export function ChatPane({
                               : `rounded-xl border px-4 py-3 text-[14px] leading-relaxed text-zinc-200 ${assistantContainerClass}`
                           }
                         >
-                          <MarkdownContent content={message.content} />
+                          {!isUser && message.pending ? (
+                            <div className="whitespace-pre-wrap break-words text-[14px] leading-relaxed text-zinc-200">
+                              {message.content}
+                            </div>
+                          ) : (
+                            <MarkdownContent content={message.content} />
+                          )}
                           {message.pending && message.content && (
                             <span className="mt-1 inline-block h-4 w-[2px] animate-pulse rounded-sm bg-zinc-400" />
                           )}

src/renderer/lib/sessionWorkspace.ts

@@ -77,17 +77,18 @@ function applyErrorEvent(session: SessionRecord, event: SessionEventRecord): Ses
 }
 
 function applyMessageDeltaEvent(session: SessionRecord, event: SessionEventRecord): SessionRecord {
-  if (!event.messageId || event.contentDelta === undefined) {
+  if (!event.messageId || (event.content === undefined && event.contentDelta === undefined)) {
     return session;
   }
 
+  const resolvedContent = event.content ?? event.contentDelta ?? '';
   const messageIndex = session.messages.findIndex((message) => message.id === event.messageId);
   if (messageIndex >= 0) {
     const existing = session.messages[messageIndex];
     const nextMessage: ChatMessageRecord = {
       ...existing,
       authorName: event.authorName ?? existing.authorName,
-      content: mergeStreamingText(existing.content, event.contentDelta),
+      content: event.content ?? mergeStreamingText(existing.content, resolvedContent),
       pending: true,
     };
 
@@ -112,14 +113,14 @@ function applyMessageDeltaEvent(session: SessionRecord, event: SessionEventRecor
     ...session,
     messages: [
       ...session.messages,
-      {
-        id: event.messageId,
-        role: 'assistant',
-        authorName: event.authorName ?? 'assistant',
-        content: event.contentDelta,
-        createdAt: event.occurredAt,
-        pending: true,
-      },
+        {
+          id: event.messageId,
+          role: 'assistant',
+          authorName: event.authorName ?? 'assistant',
+          content: resolvedContent,
+          createdAt: event.occurredAt,
+          pending: true,
+        },
     ],
     updatedAt: event.occurredAt,
   };
@@ -139,10 +140,15 @@ function applyMessageCompleteEvent(session: SessionRecord, event: SessionEventRe
   const nextMessage: ChatMessageRecord = {
     ...existing,
     authorName: event.authorName ?? existing.authorName,
+    content: event.content ?? existing.content,
     pending: false,
   };
 
-  if (nextMessage.authorName === existing.authorName && !existing.pending) {
+  if (
+    nextMessage.authorName === existing.authorName
+    && nextMessage.content === existing.content
+    && !existing.pending
+  ) {
     return session;
   }
 

src/shared/contracts/sidecar.ts

@@ -133,6 +133,7 @@ export interface TurnDeltaEvent {
   messageId: string;
   authorName: string;
   contentDelta: string;
+  content?: string;
 }
 
 export interface TurnCompleteEvent {

src/shared/domain/event.ts

@@ -15,6 +15,7 @@ export interface SessionEventRecord {
   messageId?: string;
   authorName?: string;
   contentDelta?: string;
+  content?: string;
   activityType?: SessionActivityType;
   agentId?: string;
   agentName?: string;