Fix streaming double-dispatch: suppress raw chunks during provisional buffering

packages/server/src/server/agent/agent-manager.test.ts

@@ -1384,7 +1384,7 @@ describe("AgentManager", () => {
     expect(fetched.rows.map((row) => row.seq)).toEqual([1, 2]);
   });
 
-  test("streams assistant chunks provisionally and commits one finalized assistant row", async () => {
+  test("buffers assistant chunks provisionally and streams one finalized assistant row", async () => {
     const workdir = mkdtempSync(join(tmpdir(), "agent-manager-provisional-timeline-"));
     const storagePath = join(workdir, "agents");
     const storage = new AgentStorage(storagePath, logger);
@@ -1435,18 +1435,10 @@ describe("AgentManager", () => {
     }
 
     const assistantTimelineEvents = streamEvents.filter((event) => event.itemType === "assistant_message");
-    expect(assistantTimelineEvents).toHaveLength(3);
+    expect(assistantTimelineEvents).toHaveLength(1);
     expect(assistantTimelineEvents[0]).toMatchObject({
       eventType: "timeline",
       itemType: "assistant_message",
-      text: "final ",
-    });
-    expect(assistantTimelineEvents[0]?.seq).toBeUndefined();
-    expect(assistantTimelineEvents[1]).toMatchObject({
-      text: "reply",
-    });
-    expect(assistantTimelineEvents[1]?.seq).toBeUndefined();
-    expect(assistantTimelineEvents[2]).toMatchObject({
       text: "final reply",
       seq: 1,
     });

packages/server/src/server/agent/agent-manager.ts

@@ -1972,6 +1972,7 @@ export class AgentManager {
     const isForegroundEvent = Boolean(
       eventTurnId && agent.activeForegroundTurnId === eventTurnId,
     );
+    let suppressLiveDispatch = false;
 
     // Only update timestamp for live events, not history replay
     if (!options?.fromHistory) {
@@ -2027,6 +2028,7 @@ export class AgentManager {
         }
         if (event.item.type === "assistant_message") {
           agent.provisionalAssistantText = `${agent.provisionalAssistantText ?? ""}${event.item.text}`;
+          suppressLiveDispatch = true;
           break;
         }
         if (event.item.type === "reasoning") {
@@ -2194,7 +2196,7 @@ export class AgentManager {
     }
 
     // Skip dispatching individual stream events during history replay.
-    if (!options?.fromHistory) {
+    if (!options?.fromHistory && !suppressLiveDispatch) {
       this.dispatchStream(
         agent.id,
         event,