Fix agent turn timing persistence

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

@@ -0,0 +1,87 @@
+import assert from "node:assert/strict";
+import { describe, it } from "vitest";
+import { deriveStreamTurnTiming } from "./turn-time";
+import type { StreamItem } from "@/types/stream";
+
+function user(id: string, timestamp: Date): StreamItem {
+  return {
+    kind: "user_message",
+    id,
+    text: id,
+    timestamp,
+  };
+}
+
+function assistant(id: string, timestamp: Date): StreamItem {
+  return {
+    kind: "assistant_message",
+    id,
+    text: id,
+    timestamp,
+  };
+}
+
+describe("deriveStreamTurnTiming", () => {
+  it("uses the last user message as the running turn start", () => {
+    const firstUserAt = new Date("2026-05-15T00:00:00.000Z");
+    const secondUserAt = new Date("2026-05-15T00:01:00.000Z");
+
+    const timing = deriveStreamTurnTiming({
+      agentStatus: "running",
+      tail: [
+        user("u1", firstUserAt),
+        assistant("a1", new Date("2026-05-15T00:00:05.000Z")),
+        user("u2", secondUserAt),
+      ],
+      head: [assistant("a2", new Date("2026-05-15T00:01:04.000Z"))],
+    });
+
+    assert.equal(timing.runningStartedAt, secondUserAt);
+    assert.equal(timing.byAssistantId.has("a2"), false);
+  });
+
+  it("derives completed turn timing from user and assistant item timestamps", () => {
+    const userAt = new Date("2026-05-15T00:00:00.000Z");
+    const assistantAt = new Date("2026-05-15T00:00:07.000Z");
+
+    const timing = deriveStreamTurnTiming({
+      agentStatus: "idle",
+      tail: [
+        user("u1", userAt),
+        assistant("a1", assistantAt),
+        user("u2", new Date("2026-05-15T00:01:00.000Z")),
+      ],
+      head: [],
+    });
+
+    assert.deepEqual(timing.byAssistantId.get("a1"), {
+      startedAt: userAt,
+      completedAt: assistantAt,
+      durationMs: 7000,
+    });
+  });
+
+  it("maps multiple assistant chunks in one turn to the same timing", () => {
+    const userAt = new Date("2026-05-15T00:00:00.000Z");
+    const firstAssistantAt = new Date("2026-05-15T00:00:03.000Z");
+    const lastAssistantAt = new Date("2026-05-15T00:00:07.000Z");
+
+    const timing = deriveStreamTurnTiming({
+      agentStatus: "idle",
+      tail: [
+        user("u1", userAt),
+        assistant("a1", firstAssistantAt),
+        assistant("a2", lastAssistantAt),
+      ],
+      head: [],
+    });
+
+    const expected = {
+      startedAt: userAt,
+      completedAt: lastAssistantAt,
+      durationMs: 7000,
+    };
+    assert.deepEqual(timing.byAssistantId.get("a1"), expected);
+    assert.deepEqual(timing.byAssistantId.get("a2"), expected);
+  });
+});