Add active-turn steering (#3394)

* feat(agents): add active-turn steering

Let users choose whether an immediate prompt interrupts or joins the active turn. The daemon owns exact-turn admission, provider delivery, safe fallback, and canonical timeline identity while queueing remains client-side.

* fix(agents): stabilize steering history and replay QA

* fix(agents): preserve steering timeline order

* fix(agents): reconcile resumed provider history

* fix(agents): serialize steering with cancellation

* test(agents): prove Claude multi-tool steering

* test(agents): force explicit history hydration

* fix(agents): flush output before steer admission

packages/app/src/timeline/session-stream-reducers.test.ts

@@ -197,6 +197,32 @@ describe("deriveAgentStreamTurnLiveness", () => {
   });
 });
 
+describe("timeline turn membership compatibility", () => {
+  it("hydrates tagged rows while retaining legacy rows without a turn ID", () => {
+    const hydrated = hydrateStreamState([
+      {
+        event: {
+          type: "timeline",
+          provider: "claude",
+          turnId: "turn-1",
+          item: { type: "user_message", text: "prompt", clientMessageId: "prompt-id" },
+        },
+        timestamp: new Date(1000),
+      },
+      {
+        event: {
+          type: "timeline",
+          provider: "claude",
+          item: { type: "assistant_message", text: "legacy" },
+        },
+        timestamp: new Date(2000),
+      },
+    ]);
+
+    expect(hydrated.map((item) => item.turnId)).toEqual(["turn-1", undefined]);
+  });
+});
+
 describe("detached timeline windows", () => {
   it("does not apply or catch up live events while viewing an older window", () => {
     const currentTail = [makeAssistantItem("older window")];
@@ -285,8 +311,17 @@ describe("processTimelineResponse", () => {
       text: "local prompt",
       timestamp: new Date(1000),
       timelineCursor: { epoch: "epoch-1", seq: 1 },
+      turnId: "turn-1",
     });
-    const currentTail = [canonical, makeAssistantItem("existing tail", "existing-tail")];
+    const hello = createUserMessage({
+      id: "hello",
+      clientMessageId: "hello-client",
+      text: "hello",
+      timestamp: new Date(1500),
+      timelineCursor: { epoch: "epoch-1", seq: 2 },
+      turnId: "turn-1",
+    });
+    const currentTail = [canonical, makeAssistantItem("existing tail", "existing-tail"), hello];
     const currentHead = [makeAssistantItem("existing head", "existing-head")];
 
     const result = processTimelineResponse({
@@ -314,6 +349,7 @@ describe("processTimelineResponse", () => {
         ],
       },
     });
+    expect(result.tail.find((item) => item.id === "hello")?.turnId).toBe("turn-1");
 
     expect(result.commit).toBe("discard");
     expect(result.tail).toBe(currentTail);

packages/app/src/timeline/session-stream-reducers.ts

@@ -126,6 +126,7 @@ interface TimelineResponseEntry {
   sourceSeqRanges?: TimelineSeqRange[];
   collapsed?: string[];
   provider: string;
+  turnId?: string;
   item: Record<string, unknown>;
   timestamp: string;
 }
@@ -1269,6 +1270,7 @@ export function processTimelineResponse(
       type: "timeline",
       provider: entry.provider,
       item: entry.item,
+      ...(entry.turnId ? { turnId: entry.turnId } : {}),
     } as AgentStreamEventPayload,
     timestamp: new Date(entry.timestamp),
   }));

packages/app/src/timeline/turn-time.ts

@@ -1,4 +1,5 @@
 import type { StreamItem } from "@/types/stream";
+import { startsNewTurn } from "@/agent-stream/turn-membership";
 
 export interface TurnTiming {
   startedAt: Date;
@@ -21,6 +22,7 @@ export function deriveStreamTurnTiming(params: {
   let currentUserAt: Date | null = null;
   let currentLastItemAt: Date | null = null;
   let currentAssistantIds: string[] = [];
+  let previousItem: StreamItem | null = null;
 
   const flushCompletedTurn = () => {
     if (!currentUserAt || !currentLastItemAt || currentAssistantIds.length === 0) {
@@ -37,20 +39,21 @@ export function deriveStreamTurnTiming(params: {
   };
 
   const visitItem = (item: StreamItem) => {
-    if (item.kind === "user_message") {
+    if (startsNewTurn(item, previousItem)) {
       flushCompletedTurn();
-      currentUserAt = item.timestamp;
+      currentUserAt = item.kind === "user_message" ? item.timestamp : null;
       currentLastItemAt = null;
       currentAssistantIds = [];
-      return;
     }
     if (!currentUserAt) {
+      previousItem = item;
       return;
     }
     currentLastItemAt = item.timestamp;
     if (item.kind === "assistant_message") {
       currentAssistantIds.push(item.id);
     }
+    previousItem = item;
   };
 
   for (const item of params.tail) {