fix(webchat): render final assistant payloads without history wait (#14928)

Co-authored-by: BradGroux <3053586+BradGroux@users.noreply.github.com>

ui/src/ui/controllers/chat.test.ts

@@ -53,7 +53,7 @@ describe("handleChatEvent", () => {
     expect(state.chatStream).toBe("Hello");
   });
 
-  it("returns 'final' for final from another run (e.g. sub-agent announce) without clearing state", () => {
+  it("returns final for final from another run without clearing active stream", () => {
     const state = createState({
       sessionKey: "main",
       chatRunId: "run-user",
@@ -73,6 +73,7 @@ describe("handleChatEvent", () => {
     expect(state.chatRunId).toBe("run-user");
     expect(state.chatStream).toBe("Working...");
     expect(state.chatStreamStartedAt).toBe(123);
+    expect(state.chatMessages).toEqual([]);
   });
 
   it("processes final from own run and clears state", () => {
@@ -93,6 +94,30 @@ describe("handleChatEvent", () => {
     expect(state.chatStreamStartedAt).toBe(null);
   });
 
+  it("appends final payload message from own run before clearing stream state", () => {
+    const state = createState({
+      sessionKey: "main",
+      chatRunId: "run-1",
+      chatStream: "Reply",
+      chatStreamStartedAt: 100,
+    });
+    const payload: ChatEventPayload = {
+      runId: "run-1",
+      sessionKey: "main",
+      state: "final",
+      message: {
+        role: "assistant",
+        content: [{ type: "text", text: "Reply" }],
+        timestamp: 101,
+      },
+    };
+    expect(handleChatEvent(state, payload)).toBe("final");
+    expect(state.chatMessages).toEqual([payload.message]);
+    expect(state.chatRunId).toBe(null);
+    expect(state.chatStream).toBe(null);
+    expect(state.chatStreamStartedAt).toBe(null);
+  });
+
   it("processes aborted from own run and keeps partial assistant message", () => {
     const existingMessage = {
       role: "user",

ui/src/ui/controllers/chat.ts

@@ -72,6 +72,21 @@ function normalizeAbortedAssistantMessage(message: unknown): Record<string, unkn
   return candidate;
 }
 
+function normalizeFinalAssistantMessage(message: unknown): Record<string, unknown> | null {
+  if (!message || typeof message !== "object") {
+    return null;
+  }
+  const candidate = message as Record<string, unknown>;
+  const role = typeof candidate.role === "string" ? candidate.role.toLowerCase() : "";
+  if (role && role !== "assistant") {
+    return null;
+  }
+  if (!("content" in candidate) && !("text" in candidate)) {
+    return null;
+  }
+  return candidate;
+}
+
 export async function sendChatMessage(
   state: ChatState,
   message: string,
@@ -208,6 +223,10 @@ export function handleChatEvent(state: ChatState, payload?: ChatEventPayload) {
       }
     }
   } else if (payload.state === "final") {
+    const finalMessage = normalizeFinalAssistantMessage(payload.message);
+    if (finalMessage) {
+      state.chatMessages = [...state.chatMessages, finalMessage];
+    }
     state.chatStream = null;
     state.chatRunId = null;
     state.chatStreamStartedAt = null;